3 4
on external images from an outside scene formed by tion is illustrated in FIG. 3. Note that a complete eyelight rays C. tracker package can be made without substantially
A light ray emanating from a particular pixel of dis- changing the overall dimensions of the display. As play 12 is shown as line B2. This ray is reflected by the shown in FIG. 3, a detector array 14 is formed of a Illscreen 28 (line Bl) onto the eye optics (not shown) and 5 V diode array 50 transferred to a glass substrate 52 or on to the macula (not shown) of eye 32. The axial rays directly above and onto front glass 54 of an active maof greatest importance will impinge on the fovea of the trix LCD display 12. The detector pixels 62 are posieye, the most sensitive part of the macula. These rays tioned so that each is completely above the drive tranreturn to the display in the vicinity of the original pixel sistors 64 of the active matrix circuit and therefore do because reflection from the fovea is approximately nor- 10 not block any of the display's light output from pixel mal to the retina and therefore nearly axial. Non-axial electrodes 64. (See FIG. 4). The detector row and colrays which will impinge on the retina beyond the fovea umn interconnects (not shown) are positioned directly will not be reflected back along the axial optical path above the display row and columns, so that the interand will not return to the detector array 14. connect wires do not block any light.
The viewing screen 28 may comprise, for example, 15 Note that the cut-out shown in FIG. 4 is not required
the visor of a heads-up helmet mounted optical system in practice since the detector array substrate 52 is made
for pilots and the integrated detector/display can be of transparent material such as glass or quartz,
inserted in a helmet-mounted optical system without For infrared detection, GaAs appears to be the best
physical modification to the helmet or optics. Addition- choice for the detector elements The bandgap of GaAs
ally, no physical contact with the eye is required. 20 is 1.43 eV, corresponding to an absorption edge of
Once the axial rays Bl, B2 return to the display, the about 0.87 fun. This material may also be suitable for detector array 14 identifies the portion of the array from visible light; however, if it is desirable to suppress infrawhich the axial ray emanated, by generating a voltage red absorption in the detector, the bandgap can be insignal by a detector pixel located in the array nearest the creased to about 1.9 eV (0.65 u-m) by adding aluminum returned ray. That portion of the array is, of course, the 25 (Al) to form the ternary compound semiconductor Al*. part of the display focussed on by the user. A test pat- Ga^_iAs. (A bandgap of 1.9 eV is obtained for tern from computer 18 is then interlaced with the dis- x=0.38.)
play image to enable initial determination of the eye's The process used to form the detector array is based position. Software, in computer 18, provides a cursor on the LED array process described in the aboveimage for display 12 which is projected on screen 28 at 30 referenced co-pending application Ser. No. 07/643,552, the line-of-sight location. This cursor is interlaced to as a baseline. In this process, the detector material 70 is provide constant feedback to the detector array 14. The first grown on substrate 72 by OMCVD. A release layer interlace frequency can be adjusted to make the cursor 74 is formed that permits the epitaxial film 70 to be visible or not visible to the user. separated from the substrate 72, but separation is de
For the case of a partially transparent system of FIG. 35 ferred until after the front side metallization 76 is 1 in which scenes from the surroundings are superim- formed (FIG. 5A). After metallization of rows of metalposed on the display image, the detector array 14 is lization and mesa etching to delineate the pixels 62, the provided with a narrow band pass filter overlay to surface of the wafer is bonded to a carrier 78 (FIG. 5B). reject all wavelengths except the wavelength of the This carrier is preferably the front panel 54 of display cross hair or cursor, which must be one of the display 40 12. The substrate 72 is then removed to yield a partially primary colors. Suppose for example that the selected processed detector array 14 bonded to a display array color is primary red. In this case, a narrow band red 12. The processing is then completed to form a matrix rejection filter 30 is placed on the outside of the screen addressed two-dimensional array 12 of detector pixels 28, and a narrow red bandpass filter 16 is placed over 62 aligned with the TFT's 64 (indicated by X's) but the pixels of the detector array 14. In this way, the 45 slightly displaced from corresponding pixel electrodes detector array 14 only receives light originating from 66 (indicated by dots) of the display array 12 (FIG. 5C). the display. A second method of accomplishing the Several points need to be emphasized regarding the same result is to use polarizing filters as shown in FIG. formation of the integrated detector array 14 and dis2. In this case the flat panel display 12 is an AMLCD play 12. First, the matrix metallization (not shown) of light valve helmet or head mounted display (HMD), 50 the detector must be positioned over the metallization having a polarizer 40 on its output face. The polarized of the display. In this way, no decrease in the optical nature of the light from the display 40, combined with a aperture of the display is introduced by the metal inter90° crossed polarizer 42 on the screen 28, prevents un- connects of the detector array 14. Second, the detector wanted light from the outside scene from propagating pixels 62 can be made as small as a few microns square to the detector array. 55 provided the detector sensitivity is high enough. Since
Another alternative is to chop or rapidly blink the the TFT's are also in the order of a few microns wide,
video signals from computer 18 for the cursor presenta- detector pixels of such size would not block light,
tion so that software in the computer can subtract the Third, the detector array 14 does not need to use an
background light. Yet, another alternative that can be active matrix, because III-IV materials, such as, GaAs used with LCD displays is to use infrared light that can 60 and AlGaAs are extremely fast detectors (< 1 Jas decay pass through the red filters of the LCD. But this ap- 'time) and so the detector array can be scanned as fast or
proach requires an IR rejection filter on the front of the faster than the display. Since the detector pixels are
viewing screen. It can be seen from the above that there small, they can be placed over the transistors in the
are a number of methods of using the display 12 to active matrix display, resulting in very little reduction
provide a signal for the detector array 14, without inter- 65 in optical aperture of the display,
ference from outside light. The integrated eyetracker device 100 can consist of a
An exploded view of an AMLCD display and mono- pair of units that can be simultaneously scanned by
lithic detector array 14 in accordance with the inven- computer 18 to obtain real time correlation between the
