CA2133977A1

CA2133977A1 - Vertical-cavity surface-emitting laser array display system

Info

Publication number: CA2133977A1
Application number: CA002133977A
Authority: CA
Inventors: Jack L. Jewell; Gregory R. Olbright
Original assignee: Individual
Current assignee: Photonics Research Inc
Priority date: 1992-04-21
Filing date: 1993-04-20
Publication date: 1993-10-28
Also published as: JPH07506220A; AU4291593A; EP0637409A1; EP0637409A4; US5325386A; WO1993021673A1; CN1082228A

Abstract

A visual display system is disclosed which utilizes one- and/or two-dimensional arrays of visible emitting vertical-cavity surface-emitting lasers (VCSELs) (200) in order to provide a desired visual display within an observer's field of view (220). Sweep and subscanning techniques are employed, individually or in combination, to create a full M x N image from 1 x L or K x L arrays of VCSELs, where M and N are multiple integers of K and L, respectively. Preferably, the VCSELs (200) are contained within a display housing which may be attached to the head of the user by an attachment mechanism or may alternatively be hand held or mounted to a surface. The circular symmetry and low divergence of the emitted VCSEL radiation as well as the availability of multiple wavelengths, particularly, red, blue, and green, allow high resolution monochrome or color images to be generated.

Description

~ WO93/216732 1 3 3 9 7 7 P~T/US93/03738 VERTICAL-CAVITY SURFACE-EMITTING
LASER ARRAY DISPLAY SYSTEM

~ROSS-REF~RENCE TO ~ELATXD APPLICATION
5This application is related to our co-pending application serial No. 07/790,964 entitled "Visible Light Surface Emitting Semiconductor ~aser"
filed on November 7, l99l, which is incorporated herein by reference.

FIELD OF THE INVENTION
The present invention relates to the fie'Ld of miniature visual display~ and, more particularly, to miniature visual displays that utilize visible emitting vertical-cavity surface-emitting lasers ~-(VCSELs) to project a display within an observer's field of view. :

BACKGROUND OF T~E INVENTION
Because of the human visual sensory system's enormous capacity to absorb and process information, visual displays are extremely effective in displaying a variety of information formats, such as, for example, moving sceneries, alphanumeric characters, ~5 maps, graphs, and targeting data, all of which may b superimposed on an ohserver's normal field of vision.
Particularly, tactical military operations requiring highly complex series of tasks to be performed in unpredictable environments greatly benefit from the 30 use of miniature visual displays, such as head-up, direct view, or helmet-mounted displays. For instance, tactical aircraft personnel are now being equipped with helmet-_ounted displays (HMDs) which allow a miniature visual display system to be held on 35 the head of the observer so as to project a display 2 1 3 :~ 9 ~ 7 PCr/US93/0373~

within the observer's field of vision. In the commercial sector, high-resolution HMDs can provide a "virtual reality" for entertainment and education.
In the last decade, a va~t amount of effort 5 has been expended to develop compact, lightweight visual displays, such as HMDs. Desirably, miniature visual displays should efficiently`~eliver an image generated from the display devic~` typically a cathode ray tube (CRT), to the observer's field of view with 10 minimal or no distortion. Unfortunately, the progress made to date in the miniature visual display and, more particularly, the HMD technology has been primaril'y in the classical or holographic-optics used in the imaging or relaying of the image. See, for examplle, 15 J. R. Burley et al., "A Full-Color Wide-Field-of-View Holographic ~elmet Mcunted Display for Pilot/Vehicle Interface Development and Human Factors Studies,"
Proceedinas of the SPIE, Vol. 1290, pp. ~-15 (1990).
Very little progress has, in fact, been made 20 in developing compact, high brightness, high contrast, low power CRTs. Accordingly, the lack of suitable compact CRTs severely limited the applicability of miniature visual displays, leading to the development of miniature display systems which utilized other 25 suitable display devices.
One such display system is disclosed in U.S.
Patent No. 5,003,330, which is incorporated herein by reference. This display system utilizes a diode array fixed within a helmet-visor structure. Although these 30 diode arrays perform acceptably in the helmet, they -- have not been completely satisfactory for displaying high resolution and/or color display images. Linear diode axrays and even diode laser arrays required to achieve such improvements are either not availa~le at 35 the desired visible wavelengths for color display ... -.;~.. ... . ..... ....... . ..... .. ..

W~93~21673 PCT/US~3/03738 _ 3 æ 1 3 3 9 7 7 images or not available in the array sizes required for color or high resolution miniature visual display applications.
Further, prior art lasers are not suitable 5 for two-dimensional array fabrication or micro-optic integration which is preferred for today's scanning, printing and display applications. This is due to the astigmatic beam quality of conventional semiconductor lasers as well their high divergence whirh make it 10 prohibitively difficult to project high resolution imagPs within the field of view of the observer without the use of relatively expensive and bulky optics.
Other display dev~ces which have also been 15 d~velop~d in an effort to replace the dominant image display deYice, include, for example, liquid crystal di~plays (LCDs), AC and DC plasma dis!?lays, thin film electro-luminescence displays, and vacuum fluorescent displays. Each of these alternative technologies, 20 however, has fundamental shortcomings, particularly for addressing HMD applications. LCDs, for example, have a very low ~fici~ncy in generating, modulating, and transmitting light . See, for example, D.L. Jose et al., "An Avionic Grey-Scale Color Head Down 25 Display,'C Proceedinqs of the 5PIE, Vol. l289, pp. 74-98 (l9g0). ~lasma displays, on the other hand, require on the order of approximately l00 volts or more, while the other alternative display devices are difficult to scale down to sizes achievable with 30 either the diode or laser array (approximately 20-40 ~m2 per element) technology necessary to achieve miniaturization.
To date, therefore, the size, nature and/or availability of wavelengths for display devices have W O 93/21673 .Pt~r~US93/03738 .
213~977 - 4 ~

limited the practicality and utility o~ miniature visual displays.
It is therefore an object ~f the present invention to provide a visual display system that 5 utilizes compact, solid state, high efficient, high brightness, and high contrast display devices for providing monochrome as well as full color displays to an observer's field of view. -It is a further object of the presentinvention to provide a miniature visual display system that provides a high resolution color image of visual i~formation and is suitable for a broad range of consumer, industrial, busine~s, medical and military applications.
It is still a further objeet of the present invention to provide a miniature visual display system or technology that is compatible with the existing classical and holographic optics and which utilizes a display device that is superior to the prior art 20 display devices to achieve a higher resolution.

SUMM~RY OF THE INV~ENI'ION
These and other objects are achieved in accordance wit~ the invention in a miniature visual 25 display 5yste~ ~hat utilizes visible laser diode arrays (VLDAs) and, more preferably, that utilizes one- and/or two-dimensional arrays of visible emitting vertical-cavity surface-emittiny lasers (VCSELs) in order to provide a desired visual display within an 30 observer's field of view.
In preferred embodiments, sweep and sub-scanning techniques, individually or in combination, are employed to create a full M x M image from l x N
or N x N arrays of VCSELs, where M is a multiple 35 integer of N. Such scanning techniques advantageously W093/2~673 2 1 ~ 3 9 7 7 PCT/US93/0373X

further increase the resolution of the displayed image for a given number of VCSELs by displacing the image of the VCSELs within the field of view of the observer ~-as the VCSELs are simultaneously modulated with the 5 information ~o be displayed.
Preferably, the VCSELs are contained within a display housing which may be attached to the head of the user by an attachment mechanism or alternatively may be hand held or mounted. Advantageously, the 10 circular symmetry and low divergence of the emitted VCSEL radiation as well as ~he availability of multiple wavelengths, particularly, red, blue and green, allow high resolutio~ monochrome or color images to be generated. Addressing individual VCSELs within two-dimen~ional arrays is achieved by utilizing matrix addressing techniques, such as by the use of a row/column addresæing geometryO

BRIEF DES~RIPTION_OF THE DRAWING
A more complete understanding of the invention may be obtained by reading the following description in conjunction with the appended drawings in which:
Fig. l is a cross-sectional view of a 25 visible emitting vertical-cavity surface-emitting laser ~VCSEL);
Fig. 2 is an exemplary VCSEL array display system in accordance with the principles of the inventlon;
Fig. 3 is another exemplary VCSEL array display system illustrating the use of full-sweep scanning;
Fig. 4 is an illustration of the effective beam positions seen by an observer viewing into the 35 VCSE~ array display system of Fig. 3;

3 ~ PCT~US93J0373X
2133977 - 6 ,. ~

Fig. 5 is a cross-sectional view of a monolithically integrated VCSEL array and micro-lenslets used in the practice of the present VCSEL
array display 8y8tem;
Fig. 6 is an illustra~ion of the effective beam positions seen by an obserYer viewing into a VCSEL array display system utilizing sub-scanning which improves the image resolution;
Fig. 7 is an illustration of the use 10 multiple micro-lenslets with sub-scanning to increase the effPctive resolution of the display system of the present invention;
Fig. 8 is a top vi~w of a staggered linear array of VCSELs with electronic drivers fabricated on 15 a different substrate;
Fig. 9 is illustration of the effective beam positions s~an by an observer viewing into a one-dimensional VCSEL array system utilizing jump scanning;
Fig. lO is an illustration of the effective beam positions seen by an observer viewing into a VCSE~ array display system utilizing ~weep scanning in conjunction with sub-scanning;
Fig. ll is a top view of Zl ultra-wide field-25 of-view helmet mounted display in accordance with the invention; and Fig. 12 is a side view of the helmet mounted display of Fig. ll.

DETAILED DESCRIPTIQN
The present invention is based on utilizing visible emitting yertical-cavity surface emitting asers (VCSELs) to develop a high brightness, high efficient, compact display technology and, more 35 specifically, a VCSEL array display system.

WO93/21673 2 1 ~ 3 9 7 7 PCT/~S93/03738 Particularly, the size, structure and nearly-ideal beam qualities of the VCSEL~ afford high resolution monochrome or color display images, real or virtual, to be placed within an observer's field of view.
VCSELs are a new class of semiconductor -lasers which unlike conventional edge-emitting laser diodes emit laser radiation in a direction perpendicular to the plane of the p-n junction formed therein. As disclosed in our co-pending application 10 serial No. 07/790,964, VCSELs may now ~e fabricated to emit visible laser radiation in the range between 0.4 and 0.7 ~m by utilizing an active quantum well reg:ion llO comprising alternating l~yers of, for example, GaInP and Al~Ga~InP which are sandwiched between two distributed Bragg reflectors (DBRs) or mirrors 120 and 130, as illustrated in Fig. l.
In operation, injection current is typically confined within active region llO by the use of annular shaped proton implanted regions 140 to achieve 20 stimulated emission. Importantly, VCSELs may be fabricated in one- and/or two-dimensional arrays and may be integrated with micro-optics~ With the appropriate s~lection of materials, each VCSEL can be made to emit laser radiation in different portions of 25 the visible re~ion of the electromagnetic spectrum.
The operation and fabrication of these VCSELs are discussed in de~ail in the above-identified related application and will not be described in detail here for the sake of brevity.
The basic concept of the VCSEL array display system is illustrated in Fig. 2. Tt is to be understood, however, that the VCSEL array display system depicted in Fig. 2 is for the purpose of illustration only and not for the purpose of 35 limitation. The VCSEL array display system, which is ."~
'~13397~ - 8 -typically positioned about the observer~s head, such as for use as a HMD, comprises an array of VCSELs 200, a lens system 210, and, preferably, a partially transmittin~ faceplate 220, such as a dichroic filter 5 or mirror. Lens system 210 isjpl~ced approximately an effective focal length away from VCSEL array 200 so as to collimate the visible radiation emitted from VCSEL
array 200 in order to produce a virtual image of VCSEL
array 200 in accordance with well-known optical 10 theoxy. At any instant in time, an observer looking into faceplate 220 sees simultaneously a virtual image of VCSEL array 200 as well as external visual information that is directe~ toward faceplate 220.
In displaying the desired image to the 15 observer, each laser within VCSEL array 200 may be individually addrecsed and modulated with the appropriate chroma or monochrome information by driver electronics ~30. The necessary electrical signals to address and generate the desired light intensity have 20 very low drive currents and voltagès that are compatible with analog or digital integrated CMOS and TTL electronic circuits.
Additionally, three~dimensional virtual imag~s can be produced by translating VCSEL array 200 25 or, alternatively, lens system 210 alnng the optical axis of the system to sw~ep the virtual image location from infinity to a distance close to the observer.
Such translation may be readily accomplished by a translation driver 240 that utilizes mechanical servos 30 or piezoelectric transducers to physically move the array or lens.
It is anticipated that the space occupied by VCSEL array 200 will be approximately the same as that occupied by the phosphor screens of prior art 35 miniature CRTs, which typically have a dimension of ~. .
_ 9 _ approximately 20 x 20 mm. Accordingly, critical parameters such as the HMD's field of ~iew (FOY) and packaging known in the prior art will remain s~bsti~ntially unaffected by utilizing VCSEL array 200 5 rather than the conventional CRT or other well known display devices. Moreover, those skilled in the art will know of optical designs and packing means which would further facilitate the use of VCSEL array 200 as a display system suitable for attachment to the head 10 of an observer or for hand-held use. For example, see U.S. Patent Nos. S,023,905 and 5,048,077 which are incorporated hersin by reference. For instance, the VCSEL array display of the present invention may be packaged in a disp'ay unit having an opening through which the image may be ~iewed and may be attached to a sidewall of a user's helmet, or a user's eyeglasses.
Alternatively, the display system may be attached to a user's belt, with remote display information pro~ided from a computer, pocket calculator, or radio wa~e 20 transmitter.
In one embodiment, VCSEL array 200 comprises a two-dimensional M x M array of individually addressable VCSELs. VCSELs within the M x M array may be f abricated to lase either at one predetermined 25 wavelength or at several wavelengths, such as blue, green and red, to produce monochrome or full color images, respectively, in arcordance with well known colorimetry theory.
The VCSEL array is fabricated using 30 conventional planar large scale lntegration (LSI) - processing techniques, such as _olecular beam epitaxy (MBE), wet chemical etching and the like. More particularly, the two-dimensional array is fabricated by first depositing epitaxially the semiconductor 35 layers of the VCSEL structure and then defining, for 213397~

example, by optical photolithography and etching a plurality of columns, each a separably addres~able VCSEL. Contacts to the VCSELs are formed by conventional deposition techni~es wherein, for 5 example, common row and colu~n.~us contacts may be formed to individually address each VCSEL, as disclosed in our co-pending application serial No.
07/823,496 entitled "Integra~ion of Transistors With Vertical Cavity Surface Emitting Lasers" filed on 10 January 21, 1992, which is incorporated herein by reference.
The number of VCSELs in the two-dimensional array will, of course, be dependent on the required resolution as well as the width and length of the displayed image projected to the observer.
In comparison to edge-emitting lasers, which are a few hundred microns long by 10 ~m, each VCSEL is approximately 10 ~m in ~iameter, affording more than twenty-five ~imes more display elements per unit area 20 than prior art display devices. Importantly, the emitted radiation has a circular symmetry as well as a low divergence which allow low numerical aperture lens system to be employed in generating an enlarged virtual image of the VCSELs. Also, since the VCSELs 25 have no inherent astigmatism and can be fabricated as closely-spaced, individually electrically addressable display elements, it will be apparent to those skilled in the art that an enhanced resolution may be achieved.
Information is applied to the VCSELs by individually addressing each VCSEL through the use of, for example, a matrix or row/column addressing contacts similar to those used for charged coupled device (CCD) arrays. Fully addressing a M x M array 35 of display devices electronically requires M2 leads, W093~21673 2 1 3 ~ 9 7 7 PCT/US93/03738 which is prohibitively impractical at array sizes much larger than 16 x 16 (256 leads). Accordingly, information is applied to the VCSELs by individually addressing each of the VCSELs through the use of the 5 matrix or row/column addressing geometry, reducing the number of leads from M2 to 2M. See, for example, M.
Orenstein et al., "Matrix-Addressable Vertical Cavity Surface Emitting Laser Array," Electronic Letters Vol. 27, pp.437-438 (1g91), which is incorporated 1O herein by reference. Associated driver electronic.s 230, including, for example, shift registers, transistors, and the like, used for addressing and modulating the intensity of~the emitted radiation may be integrated on the chip or substrate containing the 15 VCSEL array rather than being located external to the display unit. Such integration further reduces the number of leads, allowing large arrays, e.g., 512 x 512, to be readily fabricated. ~
If the number of elements in the VCSEL array -?O matches the required resolution of the displayed image, no scanning other than the electronic addressing is necessary. However, to increase the resolution for given number of VCSELs or to reduce the number of VCSELs needed to achieve a desired 25 resolution, various scann-ng techniques may be employed. More particularly, those skilled in the art will appreciate that scanning allows a full page display to be created from a much smaller number of display devices than is necessary to generate the full 30 page display, whether for a real or virtual image.
For example, a M x M display image may be generated from a 1 x M VCSEL array by utilizing a technique known as full-sweep scanning. The full page display is achieved by scanning along one axis the 35 VCSEL's virtual-image position perceived by the W093/21673 2~3~97~ PCT/Us93/0377`

observer. In this type of scanning, the VCSEL array comprises a plurality of linearly-aligned VCSELs having an individual VCSEL or ç ement for each resolution element along one~àxis~ Resolution 5 elements along the other axi's are provided by the scanning mechanism discussèd in more detail below.
Referring to both Figs. 3 and 4, a VCSEL
array 300 comprises a single vertical column of VCSELs represented by the black dots on the left hand side of 10 Fig. 4. Gollimated light output from the array is directed by a lens 310 to, for example, a vibrating mirror 320 of an electro-mechanical scanner 330.
Electro-mechanical scanner 330 may be of type disclosed in ~.S. Patent No. 4,902,083, which is incorporated herein by reference, in which mirror 320 is vibrated in accordance with control signals from a s~anner electronics 350. By selectively illuminating various lasers within VCSEL array 300 at various points during the vibration of mirror ~20, successive 20 columns of pixels or picture elements, i.e., display points, will be caused to appear within the field of view of the observer. These display points are represented in Fig. 4 by the entire two-dimensional array of dots, in which the black dots also represent ~5 the image position of radiation from the VCSELs in the absence of scanning and the stippled dots represent the additional display points achieved by scanning.
At any instance in time, the observer sees only one column or vertical line of VCSEL array 300, but 30 because mirror 320 is repetitively oscillated or scanned in the horizontal direction 50 as to sweep the apparent location of the vertical line of VCSEL array 300 from one edge of the observer's field of view to the other, the observer's eye perceives a full screen 35 of information, as depicted in Fig. 4.

WO93/21673 2 1 3 3 g 7 7 PCT/U~93/03738 - -~

Typically, mirror 320 is oscillating at approximately 100 Hz so as to create the illusion of a continuous full pagë or M x M image generated ~rom a 1 x M array.
Of course, the vertical line or column~-of VCSEL array 300 is appropriately modulated or electrically excited to selectively emit light for each column within the desired display image. Such driver electronics may be integrated with the VCSELs.
10 Electronic timing ensures that the proper VCSEL for each column or vertical line is illuminated at the correct time during scanning. One example of a miniature visual display an~, more particularly, a HMD
which utilizes full-sweep scanning is disclosed in 15 ~.S. Patent No. 4,~34,773, which is incorporated -herein by reference.
The number of VCSELs in the linear array will be dependent on, for example, the width of the desired image to be displayed to the-obæerver. In one 20 preferred embodim~nt, for a 1024 x 1024 display, VCSEL array 300 would ~vntain 1024 linearly-aligned VCSELs. VCSELs contemplated for use in this embodiment are approximately 10 ~m in diameter with approximately a 10 ~m space between each VCSEL.
2~ It is also possible to use sweep scanning with a VCSEL array which is not linear, such as, for example, with a quasi-linear or staggered array.
Those skilled in the art will know how to modify the electronic driver signals to compensate, in this case, 30 for the altered positions of the VCSELs.
Other scanning techniques which may be more stable are also contemplated. These techniques, for example, involve the use of micro-optics which is readily integrated with the VCSEL array. The 35 formation of sub-millimeter diameter lenslets as well WO93/21673 2 l 3397 ~ PCT/US93/03738 as the formation of waveguides on the substrate containing the VCSEL array, for example, i~prove the performance, light efficiency, surface scattering, wavelength sensitivity and beam divergence of the 5 display, all of which decre,a~es the size, weight, and complexity of the imaging ~ystems. Fig. 5 depicts an exemplary monolithic integration of a VCSEL array 510 and micro-lenslets 520 which may be used in the practice of the present invention to facilitate the 10 use of various other scanning techniques, such as electro-optic scanning techniques that employ acousto-optic _odulators (AOMs). Those skilled in the art will particularly note that~micro-lenslets 520 direct the propagation of the radiation emitted by the 15 VCSELs, performing some, if not all, of the imaging functionality of optical lens 310. For instance, micxo-lenslets 520 can decrease the beam divergence of the emitted radiation so that lower numerical aperture optical systems can be used for displaying a desired 20 image within the field of view of the ob~erver.
Alternatively, they can increase the beam divergence to increase image resolution.
In another embodiment, a noYel sub-scanning technique is employed to create a full ~ x M display 25 image from a N x N array of VCSELs, where M is a multiple integer of N. Sub-scanning, in contrast to sweep scanning, is the real or virtual movement of the VCSEL array within the field of view of the observer by a distance smaller than the inter-element or VCSE~
30 spacing. Referring to Fig. 6, the solid black dots indicate the position of the image elements of the VCSELs when directly imaged to the observer. When each image element displayed to the observer is scanned along horizontal and vertical axes 610 and 35 620, respectively, the image elements are perceived to be located at those locations represented by the stippled dots to create the illusion that a full page is being displayed. As with sweep scanning, the radiation from the VCSELs is approprîately modulated 5 during the scanning ~f the VCSEL array. The scanning can also ba accomplished by a real image displacement using, for example, piezoelectric transducers.
Typically, the inter-spacing distance, l, between each VCSEL is an integer multiple of the 10 spacing, d, between the generated sub-elements or the factor by which the resolution has been improved. It is contemplated that sub-scanning may be achieved by the use of other means, such-as piezoelectric transducers, mechanical scanners, acousto-optic modulators and the like.
These scanning techniques may also benefit from the use of micro-~ptics as well as benefit from their integration with the VCSEL array. For example, typically the ratio o~ the inter-element spacing to 20 its beam diameter is approximately 2:1. The utilization of micro-lenslets, such as illustrated in Fig. 5, to focus the radiation output or beamlet from each VCSEL to a reduced spot size increases the inter-element spacing to beam diameter ratio.
25 Advantageously, sub-scanning could then be usPd to increase the effective resolution by generating sub-pixels between adjacent VCSELs as discussed above. In contrast, the beam fr~m a light emitting diode cannot be focused effectively to a reduced spot size.
Rather than utilizing micro-lenslets, larger lenslets which collect light from multiple VCSELs can be used in conjunction with the above sub-scanning techniques. As shown in Fig. 7, lenslet pairs 710 and 720 focus emitted radiation from multiple VCSELs 730a-35 d to a reduced spot size. Whereas the spacing between WO93/21673 P~T/~S93/0373~
2~339~ - 16 - ~`

VCSEL pairs 73Qa-b and 730c-d is originally a distance, a, the spacing after the beamlets traverse through the lenslets pairs is a much smaller distance, b. Sub-scanning may now be used to generate sub-5 pixels between the imaged VCSELs, which sub-pixels are indicated by the stippled dots. Note that the demagnification factor realized by lenslet pairs 730a-b and 730c-d ~hould be an integer number equal to the number of sub-pixels required to fill the field of 10 view of the observer or the sp~ce between the imaged VCSEL points. Utilization of a single macro-lens, in contrast, does not increase the effective resolution.
Although the macro-lens would decrease the spot size, it would also decrease the inter-element spacing by 15 the same factor. That is, the ratio of the inter-element spacing to spot diameter remains unchanged.
Utilization-of sub-scanning cannot therefore be used to increase the resolution to its maximum po~sible extent where a single micro-lens is employed.
It is to be understood for the above sub-scanning tec~nique that the scanning le~gths along each axis do not have to be symmetric. By utilizing different scanning lengths it is possible ~o generate in general a M x N array display image from a K x L
25 VCSEL array, where M and N are multiple integers of K
and L, respectively.
As an example of a sub-scanning system, a 128 x 128 VCSEL array with a 40 ~m inter-element spacing may be scanned in increments of 5 ~m up to the 30 maximum distance of 35 ~m in both axes to achieve a 1024 x 1024 image (7 sub-positions in each axis between adjacent VCSEL elements).
In the above embodiments, it is contemplated that the information to be displayed may initially be -35 stored in a data storage device such as RAM, ROM, WO93/21673 2 1 3 ~ 9 7 7 PCT/US93/03738 `

EPROM and the like, which are well known in the art, when a limited set of information needs to be selectively provided to the observer. Otherwise, and for most applications requiring information which 5 varies with time, new information to be displayed may be applied to the VCSELs during the end of a frame, such as at the end of a scan.
New information to be displayed may also be directly applied to each VCSEL to create a full 10 display as discussed above by individually addressing each VCSEL without the use of matrix addressing.
Furthermore, the N x N VCSEL array may alternatively comprise rows of VCSELs whic~ are staggered in order to compensate for gaps between the devices. Fig. 8 15 depicts a portion of a staggered linear array of ~CSELs 810 having wirebonds to electronic drivers 820 which may be fabricated on a different substrate. The VCSEL arr~y and electronic drivers may alternatively be fabricated on the same substrate to eliminate the 20 need for wire bonding as disclosed in our pending application serial No. 07/823,496. Driver electronics 820 include transistors, such as FETs, bipolar ~~-~
transistors, and the like. In general, the structures disclosed in the above-identified application may be 25 used in the practice of the present invention.
In one example, one-dimensional sub-scanning may be utillzed for laser printing applications, such as a 3600 dots-~er-inch (dpi) printer covering a 20 x 75 inch area. A 20 inch linear VCSEL array having 300 30 VCSELs per inch can be sub-scanned in one dimension such that each VCSEL controls the illumination at 12 points (pixels) in a line to achieve the desired 3600 dpi resolution. Advancing the printing material in the other dimension allows printing in that dimension.

W O 93/21673 PC~r/VS93/0373~ ~
213~7 - 18 -An alternative to one-dimensional sub-scanning is to translate a one-dimensional array of VLDAs, such as of the VCSEL type, by a distance equal to a multiple integer length of the array size plus 5 one inter-pixel distance. As shd~n in Fig. 9, a VCSEL
array 850 comprising three gro~ps 860a-c of a 1 x 4 VCSEL sub-arrays is scanne~ by stepping the arrays through the image in multiple illumination phases. In the first phase, the arrays control the illumination 10 of display points 870a-c. For the second phase, radiation from arrays 860a-c is translated, such as by electro-mechanical means, to the positions indicated by stippled dots 870a'-c', respectively. The VCSELs are accordingly modulated with appropriate monochrome or chroma information corresponding to their translated positions to generate new effective re~olution elements or pixels. Then, in the third phase, radiation from arrays 860a-c is stepped or translated to positions 870a"-c", respectively. This 20 stepping or "jump" technique effectively produces 4 additionally pixels for each translation or step.
Here, 8 additional pixels are produced for each of sub-arrays 860a-c. This particular type of scanning, referred to as "jump" scanning, may also be used for 25 laser printing applications. For example, if 6000 lasers on 60 chips of 100 lasers each would be required to ac~ieve a desired resolution, then the same task could be done using 10 chips of 100 lasers each by performing 6 "jumps" or repeated translations.
Two-dimensional display images may also be generated by combining both sweep ~canning and sub-scanning techniques. Referring to Fig. 10, a 16 x 16 display image may be generated from 1 x 4 VCSEL array by sweep scanning along a horizontal axis 910 and sub-35 scanning along a vertical axis 920. The inter-element WO93/21673 ? 1 3 3 9 7 7 PCT/US93/037~ ~

spacing, y, between VCSELs is such that 3 sub-positions are generated therebetween by displacing the virtual image of the VCSELs in repeated increments.
Along horizontal axis 9lO the virtual image perceived 5 by the ob~erver is displaced in increments corresponding to the desired sub-positi.on spacing, x, up to a distance corresponding to l~ pixels. Along vertical axis 920, however, the virtual image is displaced in increments of the desired sub-position 10 spacing, x, but only up to a distance corresponding to the inter-element VCSEL spacing, y~
A unique aspect of the present invention is the ability to generate a ful~ color display. In or~e embodiment of a full-color display, three different 15 types of VCSELs are needed in a single array, each of which types emits light at a different wavelength such as a green, blue and red, in order to provide color visual images. Illustratively, each row of VCSELs in the array comprises VCSELs of only one type and the 20 colors emitted by such rows alternate in regular fashion. The rows themselves may be staggered to eliminate the gaps between each VCSEL.
Under the control of timing and control circuitry, the appropriate chroma data is applied to 25 each row of VCSETs, but at slightly different time intervals. As a result, the output from each set of three adjacent rows of different color VCSELs is imaged to the same line within the virtual image so as to produce a color display in accordance with well 3~ known colorimetry theory.
Approximate ranges for the green, red and blue wavelengths are 6lO-630 nm, 514-554 nm, and 440-470 nm, respectively. These wavelength ranges satisfactorily provide the full color spectrum and are 35 within the operating range of the VCSELs disclosed in 21339~7 - 20 -our co-pending application serial No. 07/790,964.
More specifically, alternating layers of GaInP and Al~Gal~InP within the active region may be used to generate radiation in the red region; alternating 5 layers of GaInP and Al~Gal~P within the active region may be used to generate radiation in the green region;
and alternating layers of AlyGal~N and Al~Ga~N within the active region may be used to generate radiation in the blue region.
Preferably, 605 nm, 554 nm and 460 nm will be used as the wavelengths for the red, green, and blue radiation, respectively, because these wavelengths provide the highest efficiency for producing white light. Utilizing longer wavelengths above 605 nm as the red source requires greater red light intensity 'n order to maintain the same irradiance.
Partially transmissive reflectors may further be used to direct the color display image ~0 within thR field of view of the observer. These reflectors may be fabricated with enhanced reflectivities at the radiation wavelengths of the VCSELs to minimize the required optical power.
Moreover, the reflectivities elsewhere may be 25 minimized (i.e., high transmissivity) to maximize ou~side ~iewing of external information.
In accordance with the principles of the invention, VCSELs may be also integrated with, or even replaced by, other display devices, such as visible 30 diode lasers or superluminescent light emitting diodes (SLEDs~ to further au~ment and/or complement the applicability of the present inventive VCSEL array display system. Those skilled in the art will know that a SL~D is a light emitting diode (LED) whose efficiency and emission directionality are enhanced by the addition of a partial cavity. SLEDs can be constructed very similarly to VCSE~s using standard planar LSI proc~ssing techniques. In accordanc~ with the principles of inventions, it is cvntemplated that 5 VCSELs will be integrated with SLED and/or LEDs.
In another embodiment, sweep scanning in conjunction with sub-scanning may further be utilized to realize a HMD having a ultra-wide field-of-view~
More specifically, the sweep scanning is implemented 10 by using a rotating polygonal mirror to achieve fields of view near 180 degrees. Rotating polygonal mirro:rs are advantageously more robust than vibrating mirro:rs and, moreover, afford one the capability to exploit the nearly circular symmetry field-of-view of HMDs.
Shown in Figs. ll and 12 are top and side views, respectively, of a ultra-wide field-of-view HMD
which u~ilizes the principles of the present invention. Polygonal mirror 920 rotates about a vertical axis ~o sweep the apparent location of a 20 ~CSEL array 9lO from one edge of the observer's field of view to the other/ as previously illustrated in Fiy. 4. A 180 degree field-of-view ~ay be achieved by a 90-l20 degree rotation of polygonal mirror 920 with the appropriate number of sides. For this arrangement 25 the VCSEL array advantageously is a linear array oriented in a vertical direction so that it is parallel to the axis of rotation of mirror 920. A
cylindrical lens 930 located near the upper portion of the HMD or forehead of the observer expands the 30 emitted radiation from VCSEL array 9lO along the horizontal axis. The beam expansion is sufficient to fill the pupil aperture of both eyes of the observer to achieve full binocular display. Either an appropriate horizontal curvature on polygonal mirror 35 920, as shown in Fig. 12, or a multiplicity of W~93/21673 PCT/US~3/03738 213397~ - 22 -, ~

cylindrical lenses may, however, be used to replace single cylindrical lens 930.
It is believed that a vertical expansion of only 15-~0 ~m need be achieved to account for the 5 observer's head motion. Pre~erably, for binocular displays, horizontal beam widths of 100 mm or more are contemplated. A concave partial reflector 940, which is preferably 50-75 mm from the observer' pupil~, produces a virtual image of VCSEL array 910 within the 10 field of view of the observer in accordance with well known optical theory. Appropriately addressing and modulating each individual VCSEL in conjunction with ~-sweep scanning then presents~a full panorama display to the observer.
Note that since radiation from each VCSEL
-traverses through only a small portion of the system, the system components do not introduce any substantial optical aberrations. Thus, resolution better than one cycle per mrad may be accomplished over the entire 20 field-of-view with only a small number of optical components.
Those skilled in the art will readily note that the vertical Goncavity of both polygonal mirror 920 and partial reflector 940 is used to tailor the 25 vertical beam characteristics of the emitted radiation. Cylindrical lens 930 and the horizontal curvature of concave partial reflector 940, on the other hand, tailor the horizontal ~hape or beam characteristics of the emitted radiation. In this 30 manner, the emitted radiation can be properly directed into, for example, 180 degree fîeld-of-view.
Multiple VCSEL arrays, each array emitting radiation at a different wavelength can further be employed to produce color image~. For example, VCSEL
35 arrays 910, 950 and 960 may be placed at different ~_ WO93/21673 2 1 3 3 9 7 7 PCT/US93/03738 t positions around rotating mirror 920, where array 910 emits red radiation, array 950 emits gr~en radiation and array 960 emits blue radiation. Radiation from each array, of course, would be synchronized to 5 generate a color image in accordance with well known colorimetry theory.
Each side of rotating mirror 920 further could be tilted vertically with respect to each other so that each side sweeps out a unique set of 10 horizontal pixels~ For example, with a 4 sided rotating mirror, each side having a slight vertical tilt, sub-scanning as described hereinabove may be realized in the vertical direction to effectively increase the vertical resolution by a factor of four.
15 Hence, a display resolution of 1024 elements in the vertical direction could be accomplished by utilizing a ~ingle array haYing only 256 VCSELs. Note that this latter scheme effectively combines sub-scanning and sweep scanning techniques to produce extremely high 20 resolution display images over a ultra-wide field-of-view with a minimum number of VCSELs.
It should be understood that various other modifications will be readily apparent to those skilled in the art without departing from the scope 25 and spirit of the invention. For example, head-down displays fox cockpit environments may also be constructed utilizing the principles of the invention in which a real image is projected from the VCSEL
array onto a screen for viewing by an observer.
30 Moreover, simulators may also be constructed employing a combination of ~irtual-image and real-image displays.
Accordingly, it is not intended that the scope of the claims appended hereto be limited to the 35 description set forth therein, but rather that the WO93/21673 PCT~US93/03738 213~77 - 24 ~

claims be construed as encompassing all the features of patentable novelty ~hat raside in the present invention, including all features that would be treated as equivalents thereof~b~ those skilled in the 5 art to which this inventio~pertains.

1o ,:

Claims

What is claimed is:

1. A visual display system comprising:
a plurality of visible emitting vertical-cavity surface-emitting lasers, each of said lasers emitting radiation; and means for displaying an image of said plurality of visible emitting vertical-cavity surface-emitting lasers within the field of view of an observer.

2. The visual display system of claim 1 having a size suitable for headgear-mounted use.

3. The visual display system of claim 2 wherein said means for displaying includes means for creating a virtual image of said plurality of visible emitting vertical-cavity surface-emitting lasers, and a rotating mirror for displacing said virtual image over a desired field-of-view.

4. The visual display system of claim 1 further comprising means for selectively modulating the intensity of the radiation from each of said plurality of visible emitting vertical-cavity surface-emitting lasers so that said image substantially represents a predetermined visual display.

5. The visual display system of claim 1 wherein said plurality of visible emitting vertical-cavity surface-emitting lasers emit radiation at a predetermined wavelength so that said image is monochrome.

6. The visual display system of claim 1 wherein said plurality of visible emitting vertical-cavity surface-emitting lasers emit radiation at a plurality of wavelengths so that said image is in color.

7. The visual display system of claim 6 wherein said plurality of visible emitting vertical-cavity surface-emitting lasers are aligned in sets of three lines, said vertical-cavity surface-emitting lasers in each line emitting radiation at a different predetermined wavelength.

8. The visual display system of claim 7 wherein vertical-cavity surface-emitting lasers in a first line of said sets emit in the visible red region of the electromagnetic spectrum, vertical-cavity surface emitting lasers in a second line of said sets emit in the visible green region of the electromagnetic spectrum, and vertical-cavity surface-emitting lasers in a third line of said sets emit in the visible blue region of the electromagnetic spectrum.

9. The visual display system of claim 8 wherein said vertical-cavity surface-emitting lasers in said first, second and third lines are staggered with respect to each other.

10. The visual display system of claim 1 wherein said plurality of visible emitting vertical-cavity surface-emitting lasers are aligned in a substantially one-dimensional array.

11. The visual display system of claim 1 wherein said plurality of visible emitting vertical-cavity surface-emitting lasers are aligned in a substantially two-dimensional array.

12. The visual display system of claim 1 wherein said means for displaying comprises imaging means for creating a virtual image of said plurality of visible emitting vertical-cavity surface-emitting lasers, and means for reflecting said virtual image into the field of view of the observer.

13. The visual display system of claim 12 wherein said means for reflecting includes a mirror.

14. The visual display system of claim 12 wherein said means for reflecting includes a partially transmissive, partially reflective faceplate such that the observer can simultaneously view the image of said plurality of visible emitting vertical-cavity surface-emitting lasers and external visual information directed to the observer.

15. The visual display system of claim 12 further comprising means for adjusting the location of said virtual image from infinity to a distance close to the observer.

16. The visual display system of claim 15 wherein said means for adjusting includes a mechanical servo for displacing said plurality of vertical-cavity surface emitting lasers.

17. The visual display system of claim 1 further comprising micro-lenslets for directing the propagation of the radiation from said plurality of vertical-cavity surface-emitting lasers.

18. A visual display system for displaying an image having M x N picture elements within the field of view of an observer, said visual display system comprising:
a plurality of visible emitting vertical-cavity surface-emitting lasers aligned substantially in at least a first 1 x N array, said lasers emitting radiation;
means for creating an image of said plurality of visible emitting vertical-cavity surface-emitting lasers;
means for repetitively displacing the position of said image within the field of view of the observer; and means for selectively controlling the intensity of the radiation emitted from each of said plurality of vertical-cavity surface-emitting lasers as the position of said image is displaced to create the desired M x N image.

19. The visual display system of claim 18 wherein said image is a virtual image.

20. The visual display system of claim 18 wherein said plurality of visible emitting vertical-cavity surface-emitting lasers emit radiation at a predetermined wavelength so that said M x N image is monochrome.

21. The visual display system of claim 18 wherein said plurality of visible emitting vertical-cavity surface emitting lasers emit radiation at a plurality of wavelengths so that said image is in color.

22. The visual display system of claim 21 wherein said plurality of visible emitting vertical-cavity surface-emitting lasers are aligned in three lines of 1 x N arrays, said vertical-cavity surface-emitting lasers in each line emitting radiation at a different predetermined wavelength.

23. The visual display system of claim 22 wherein vertical-cavity surface-emitting lasers in a first line of said 1 x N arrays emit in the visible red region of the electromagnetic spectrum, vertical-cavity surface emitting lasers in a second line of said 1 x N arrays emit in the visible green region of the electromagnetic spectrum, and vertical-cavity surface-emitting lasers in a third line of said 1 x N
arrays emit in the visible blue region of the electromagnetic spectrum.

24. The visual display system of claim 18 further comprising micro-lenslets for directing the propagation of the radiation from said plurality of vertical-cavity surface-emitting lasers.

25. The visual display system of claim 18 wherein vertical-cavity surface-emitting lasers within said 1 x N arrays are staggered with respect to one another.

26. A visual display system for displaying an image having M x N picture elements within the field of view of an observer, said visual display system comprising:
a plurality of visible emitting lasers aligned substantially in a K x L array, said lasers emitting radiation;
means for creating an image of said plurality of visible emitting vertical-cavity surface-emitting lasers;
means for repetitively displacing the position of said image within the field of view of the observer; and means for selectively controlling the intensity of the radiation emitted from each of said plurality of vertical-cavity surface-emitting lasers as the position of said image is displaced to create the desired M x N image, where M and N are greater than K and L, respectively.

27. The visual display system of claim 26 wherein said visible emitting lasers are vertical-cavity surface-emitting lasers.

28. The visual display system of claim 26 wherein said visible emitting lasers are light emitting diodes.

29. The visual display system of claim 26 wherein said visible emitting lasers are edge-emitting laser diodes.

30. The visual display system of claim 26 wherein said image is a virtual image.

31. The visual display system of claim 26 wherein said plurality of visible emitting lasers emit radiation at a predetermined wavelength so that said M
x N image is monochrome.

32. The visual display system of claim 26 wherein said plurality of visible emitting lasers emit radiation at a plurality of wavelengths so that said image is in color.

33. The visual display system of claim 26 wherein 1 x L arrays of said K x L arrays of said plurality of visible emitting lasers are aligned in three lines, said visible emitting lasers in each line emitting radiation at a different predetermined wavelength.

34. The visual display system of claim 33 wherein visible emitting lasers within said 1 x L
arrays are staggered with respect to one another.

35. The visual display system of claim 33 wherein said visible emitting lasers in a first line of said 1 x L arrays emit in the visible red region of the electromagnetic spectrum, vertical-cavity surface emitting lasers in a second line of said 1 x L arrays emit in the visible green region of the electro-magnetic spectrum, and vertical-cavity surface-emitting lasers in a third line of the said 1 x L
arrays emit in the visible blue region of the electromagnetic spectrum.

36. The visual display system of claim 26 further comprising micro-lenslets for directing the propagation of the radiation from said plurality of visible emitting lasers.

37. A visual display system for displaying a desired image within the field of view of an observer, said visual display system comprising:
a laser array including a plurality of vertical-cavity surface-emitting lasers and light emitting diodes, said vertical-cavity surface-emitting lasers and light emitting diodes emitting radiation in the visible electromagnetic spectrum;
means for creating an optical image of said laser array;
means for repetitively displacing the position of said optical image within the field of view of the observer; and means for selectively controlling the intensity of the radiation emitted from said laser array as the position of said optical image is displaced to create the desired image.

38. A visual display system for displaying a desired image having M x N picture elements within the field of view of an observer, said visual display system comprising a plurality of surface-emitting lasers aligned substantially in K 1 x L arrays, said 1 x L
arrays being arranged in groups of two or more lasers;
a plurality of lenslet pairs having an optical axis substantially collinear with the direction of propagation of radiation emitted from said lasers, each lenslet pair for imaging lasers within a group to corresponding groups of reduced image size such that the inter-group spacing for the groups of reduced image size is greater than that for said groups of lasers;
means for creating an image of said groups of reduced image size;
means for repetitively displacing the position of said image within the field of view of the observer so as to generate sub-picture elements between the groups of reduced image size; and means for selectively controlling the intensity of the radiation emitted from each of said plurality of surface-emitting lasers as the position of said image is displaced to create the desired M x N
image, where M and N are greater than K and L, respectively.

39. The visual display system of claim 38 wherein said surface-emitting lasers are vertical-cavity surface-emitting lasers.

40. The visual display system of claim 38 wherein said surface-emitting lasers are light emitting diodes.

41. The vidual display system of claim 38 wherein said surface-emitting lasers are edge-emitting laser diodes.

42. A visual display system for displaying a desired image having M x N picture elements within the field of view of an observer, said visual display system comprising:
a plurality of surface-emitting lasers aligned substantially in a 1 x L array, said 1 x L
array being arranged in groups of two or more lasers;

a plurality of lenslet pairs having an optical axis substantially collinear with the direction of propagation of radiation emitted from said lasers, each lenslet pair for imaging lasers within a group to corresponding groups of reduced image size such that the inter-group spacing for the groups of reduced image size is greater than that for said groups of lasers;
means for creating an image of said groups of reduced image size;
means for repetitively displacing the position of said image within the field of view of the observer so as to generate sub-picture elements between the groups of reduced image size and picture elements along first and second directions, respectively, of said image; and means for selectively controlling the intensity of the radiation emitted from each of said plurality of surface-emitting lasers as the position of said image is displaced to create the desired M x N
image, where M and N are greater than K and L, respectively.

43. The visual display system of claim 42 wherein said surface-emitting lasers are vertical-cavity surface-emitting lasers.

44. The visual display system of claim 42 wherein said surface-emitting lasers are light emitting diodes.

45. The visual display system of claim 42 wherein said surface-emitting lasers are edge-emitting laser diodes.

46. A scanning configuration comprising:
a plurality of surface-emitting lasers substantially aligned in at least a 1 x N array along a first direction, said 1 x N array having an inter-element spacing, d, and each of said lasers corresponding to a picture element;
means for creating an image of said plurality of surface-emitting lasers; and means for repetitively displacing the image of said plurality of surface-emitting lasers by a distance less than the inter-element spacing, d, along said first direction so as to generate sub-picture elements between the images of adjacent lasers.

47. The scanning configuration of claim 4?
wherein said surface emitting lasers are vertical-cavity surface-emitting lasers.

48. The scanning configuration of claim 46 wherein said surface emitting lasers are light emitting diodes.

49. The scanning configuration of claim 46 wherein said surface emitting laser are edge-emitting laser diodes.

50. The scanning configuration of claim 46 wherein surface-emitting lasers within said 1 x N
array are staggered with respect to one another.

51. The scanning configuration of claim 46 further comprising means for respective ? displaying the image of said plurality of surface-emitting lasers along a second direction, said second direction substantially perpendicular to said first direction.

52. The scanning configuration of claim 51 wherein said plurality of surface-emitting lasers emit radiation at a plurality of wavelengths so that said image is in color.

53. The scanning configuration of claim 51 wherein said plurality of surface-emitting lasers are aligned in three lines of 1 x N arrays, said surface-emitting lasers in each line emitting radiation at a different predetermined wavelength.

54. The scanning configuration of claim 53 wherein surface-emitting lasers in a first line of said 1 x N arrays emit in the visible red region of the electromagnetic spectrum, surface-emitting lasers in a second line of said 1 x N arrays emit in the visible green region of the electromagnetic spectrum, and surface emitting lasers in a third line of said 1 x N arrays emit in the visible blue region of the electromagnetic spectrum.

55. The scanning configuration of claim 46 further comprising micro-lenslets for directing the propagation for radiation from said plurality of surface-emitting lasers.

56. The scanning configuration of claim 46 wherein said means for creating an image includes an optical lens system.

57. The scanning configuration of claim 46 wherein said means for repetitively displacing said image includes a resonating mirror.

58. The scanning configuration of claim 46 wherein said means for repetitively displacing said image includes a rotating mirror.

59. The scanning configuration of claim 58 wherein said rotating mirror has N sides, each side having a vertical tilt with respect to each other.