WO2000040010A1

WO2000040010A1 - Contoured surface cover plate for image sensor array

Info

Publication number: WO2000040010A1
Application number: PCT/US1999/030654
Authority: WO
Inventors: Scott Campbell
Original assignee: Photobit Corporation
Priority date: 1998-12-24
Filing date: 1999-12-23
Publication date: 2000-07-06

Abstract

A cover (214) for an image sensor array (102) is disclosed. The cover (214) includes a plate formed of substantially transparent material and placed adjacent to the image sensor array (102). The plate has a plurality of surfaces and forms a lensing structure (224). At least one of the plurality of surfaces is contoured into a lensing surface (226) capable of performing an imaging improvement or enhancement function.

Description

CONTOURED SURFACE COVER PLATE FOR IMAGE SENSOR ARRAY

Cross-Reference to Related Applications

This application claims benefit of the priority of U.S.

Provisional Application Serial Number 60/113,850, filed

December 24, 1998 and entitled "Contoured Surface of Image

Plane Array Cover Plate."

Background

The present specification generally relates to image

sensor arrays, and particularly to a contoured-surface cover

plate for such image sensor arrays.

When a sensor array is mounted on an image sensor

assembly such as a digital camera system, the sensor array is

sealed for protection by bonding a cover plate on the assembly

over the sensor array. Often, the cover plate is a flat piece

of transparent material, such as glass, plastic or plexiglass,

which provides protection only from the environment. The

cover plate offers little in terms of optical enhancement.

On the other hand, competition for cheap camera systems

is driving demand for high quality optics at a low price.

However, such high quality optics are difficult to design and fabricate without the use of multiple lensing elemen s.

Therefore, the use of multiple lensing elements often drives

the price up. In addition, the lensing elements, once

fabricated, must be mounted and aligned to the camera system

at fairly tight tolerances in positioning, focus, and

attitude. This also adds to the overall cost of the camera

system.

Summary

The techniques described herein obviate the above

described difficulties by deterministically contouring the

optically-flat cover plate. The contouring allows for the use

of the cover plate as an additional lensing element. The

placement of the contoured cover plate in the optical path of

an incident light converts a singlet lens system into a

doublet system, a doublet system into a triplet system, and so

on.

The contouring of the cover plate also allows using the

plate as mounting structures for the lensing elements, such as

lenses, filters, and polarizers. The mounting structures can

have alignment marks which are used to automatically align and

secure the lensing elements. Furthermore, the contouring of the cover plate enhances the ability of the lensing element to

correct the aberration of Petzval field curvature. The

aberration is the natural tendency for a lens to produce its

image on a curved rather than a flat focal plane. Therefore,

the placement of the contoured cover plate close to the image

sensor often reduces this aberration.

A lensing structure may include lensing elements,

mounting structures, and alignment marks.

In one aspect, the present specification involves a cover

for an image sensor array. The cover includes a plate formed

of substantially transparent material and placed adjacent to

the image sensor array. The plate has a plurality of surfaces

and forms a lensing structure. At least one of the plurality

of surfaces is contoured into a lensing surface capable of

performing an imaging improvement or enhancement function.

In another aspect, an image sensor camera system for

converting optical data into digital image data is described.

The camera system includes a lens system, an image sensor

array, and sensor electronics.

The lens system carries and focuses the optical data onto

the image sensor array. The lens system includes a plurality of lenses and a cover plate. The cover plate is contoured

into a lensing structure for imaging improvement and

enhancement function.

The image sensor array has a plurality of sensors. The

sensors receive the optical data and integrate the data into

electrical charge proportional to the amount of optical data

collected within a particular period of time. The sensor

electronics receive the electrical charge and converts the

electrical charge received by the plurality of sensors into

digital image data.

The details of one or more embodiments are set forth in

the accompanying drawings and the description below. Other

embodiments and advantages will become apparent from the

following description and drawings, and from the claims.

Brief Description of the Drawings

These and other aspects will be described in reference to

the accompanying drawings wherein:

FIG. 1A is an exploded view of a cover plate;

FIG. IB is a side view of the cover plate cut along the

plane 1-1 indicated in FIG. 1A; FIG. 1C is another embodiment of the cover plate

contoured into a positive lens with convex protuberance;

FIG. 2A is one embodiment of an existing three-element

lens system;

FIG. 2B is the lens system of FIG. 2A inserted into the

cover plate;

FIG. 3A is a diffraction grating blazed onto the surface

of the cover plate;

FIG. 3B is a diffraction grating blazed on a concave

depression;

FIG. 3C is a diffraction grating blazed on a convex

protuberance ;

FIG. 4A is an injection molded cover plate having a post

and a convex lensing surface;

FIG. 4B is an injection molded cover plate having a post

and a concave lensing surface;

FIGS. 5A and 5B show top views of the cover plates

including mounting structures;

FIGS. 5C through 5H show different embodiments of the

mounting structure from the side; FIGS. 6A through 6C show different embodiments of the

cover plate having a combination of lensing elements and

mounting structures;

FIG. 7A is a cut-away side perspective view of an image

sensor camera system; and

FIG. 7B is a block diagram of the image sensor camera

system.

Like reference numbers and designations in the various

drawings indicate like elements.

Detailed Description

A detailed description of the contoured surface of an

image sensor array cover plate is herein provided with respect

to the figures.

FIG. 1A shows an exploded view of a cover plate 100

placed in front of an image sensor array 102. The image

sensor array can be an array of active pixel sensors. Each

active pixel sensor includes a photoreceptor, e.g., a

photodiode or photogate, an in-pixel follower transistor, and

an in-pixel selector transistor. The cover plate 100 is

contoured to act as an additional lensing element 104. The lensing element 104 operates to enhance the focusing of light

onto the image sensor array 102.

FIG. IB shows a side view of the cover plate 100 cut

along the plane 1-1 indicated in FIG. 1A. The cover plate 100

is contoured into a negative lens with concave depression 106

and is placed in front of the image sensor array 102 to focus

the light falling onto the sensor array 102.

FIG. 1C shows another embodiment of the cover plate 108

contoured into a positive lens with convex protuberance 110.

The cover plate 108 is placed in front of the sensor array

102.

FIG. 2A shows one embodiment of an existing three-element

lens system 200. The lens system 200 includes a first convex

lens 202, a second plano-concave lens 204, and a third plano-

convex lens 206. The lens system 200 also includes a lens

mount 208, a threaded retaining ring 210, and a guide tab 212.

Light enters the lens system 200 from the direction indicated

as 214.

FIG. 2B illustrates the lens system 200 inserted into a

cover plate 214. The cover plate 214 can have a mounting

structure 218 attached to the front surface 222. In another embodiment, the cover plate 214 can be a single-piece

injection molded structure that includes the mounting

structure 218.

The lens system 200 can be inserted into the cover plate

214 by threading it into the mounting structure 218. The

threaded retaining ring 210 on the lens mount 208 is guided

into a threaded ring 220 on the mounting structure 218 to lock

the lens system 200 onto the cover plate 214. In an

alternative embodiment, the lens system 200 can be secured

onto the cover plate 214 by locking the guide tab 212 on the

lens mount 208 onto the cover plate 214 using an alignment

mark 216.

Once the three-element lens system 200 is firmly secured

to the cover plate 214, the combination effectively forms a

four-element lens system comprising the three lenses 202, 204,

206 in the lens system 200 and a contoured surface 226 of the

lens 224 formed by the cover plate 214. Furthermore, the

contoured lens 224 enhances the ability of the four-element

lens system to correct the aberration of Petzval field

curvature. The aberration is the natural tendency for a lens

to produce its image on a curved rather than a flat focal plane. Therefore, the placement of the contoured cover plate

214 close to the image sensor 102 often reduces this

aberration inherent in flat cover plates.

FIG. 3A shows a diffraction grating 302 blazed onto the

surface of a cover plate 300. The diffraction grating 302

performs similar imaging improvement function to the

refractive lens system in FIG. 2B. Therefore, the cover plate

300 with the diffraction grating 302 formed on its surface

acts as a diftractive lensing element 316.

In another embodiment, hybridization of refractive and

diftractive profiles is formed on a cover plate 304. FIG. 3B

shows a diffraction grating 306 blazed on a concave depression

308 formed on the cover plate 304. The concave grating 306

can be manufactured using ruling and holographic techniques.

The concave grating forms a hybrid refractive-diftractive

lensing element 318.

In a further embodiment, shown in FIG. 3C, a diffraction

grating 312 is formed on a convex surface 314 of a cover plate

310. The convex grating 312 can be manufactured using a

similar technique used for the concave grating 306 shown in FIG. 3B. The convex grating forms a hybrid refractive-

diftractive lensing element 320.

FIG. 4A shows an injection-molded cover plate 400 having

a post 402 and a convex lensing surface 404. The post 402 and

the lensing surface 404 form a complete lens system and

thereby eliminate the need for additional lenses. The post

402 and the lensing surface 404 are formed over the sensor

array region 406 to direct the light onto the sensor array

102. The post 402 and the lensing surface 404 form a lensing

element 408.

In an alternative embodiment, shown in FIG. 4B, the

lensing surface 410 can be contoured as a concave depression

forming a lensing element 412.

FIGS. 5A through 5H show several different embodiments of

a mounting structure 500, 502. The mounting structure 500,

502 is formed over the sensor array. The mounting structure

500, 502 is configured to allow the lens system to be easily

and quickly mounted onto the cover plate 504.

FIG. 5A shows a top view of the cover plate 504 including

the mounting structure 500 formed on the top surface 506 of

the cover plate 504. In this embodiment, the mounting structure 500 forms a square pattern, which allows a square-

shaped lens mount to be mounted securely to the mounting

structure 500. FIG. 5B shows a circular-shaped mounting

structure 502 formed on the surface 506 of the cover plate

504.

FIGS. 5C through 5H show several different embodiments

of the mounting structure 500 from the side. The side views

are formed by slicing the cover plate 504 along the line 5-5.

FIG. 5C shows a mounting structure formed with a mesa-

like protrusion 508 on the surface 510 of the cover plate

504. The protrusion 508 can be a clear material attached to

the front surface of the cover plate 504 or injection molded

into a single-piece cover plate 504. The protrusion 508 can

have a threaded retaining ring on the outside wall for easy

insertion, focus and removal of the lens system.

FIG. 5D shows a variation of the mounting structure

shown in FIG. 5C. The mounting structure in FIG. 5D can be

formed with a hollowed-out mesa-like protrusion or a ringed-

wall structure attached to the cover plate 504.

FIGS. 5E and 5F show two variations of the ringed

mounting structure 512 shown in FIG. 5D. FIG. 5E shows a threaded retaining ring 514 on the outside wall of the

ringed structure 512. FIG. 5F shows the threaded retaining

ring 514 on the inside wall of the ringed structure 512.

The threaded retaining ring 514 is used to mount and

securely attach the lens mount to the mounting structure

512.

FIGS. 5G and 5H show a mounting structure formed with a

well-like depression 516 in the cover plate 504. The

depression 516 can be used to lock the lens mount onto the

cover plate 504. FIG. 5H also shows a threaded retaining

ring 518 on the side wall of the well-like depression 516

for locking the lens mount .

FIGS. 6A through 6C show different embodiments of the

cover plate having a combination of lensing elements and

mounting structures.

FIG. 6A shows a cover plate 600 having a lensing

element 608 and a mounting structure 604. The lensing

element 608 is formed with a concave lensing surface 602.

The mounting structure 604 can have a threaded retaining

ring 606 on the inside or outside wall of the mounting

structure 604. FIG. 6B shows another combination of a lensing element

616 and a mounting structure 612. The lensing element 616

is formed with a post 618 and a convex lensing surface 614

at the top of the post 618.

FIG. 6C shows a combination of a ringed mounting

structure 622 and a lensing element 620 in the middle. The

lensing element 620 is formed with a post 624 and a convex

lensing surface 626.

FIG. 7A shows a cut-away side perspective view of an

image sensor camera system 700. The camera system can be an

active pixel sensor (APS) system or a charge-coupled device

(CCD) system. The camera system 700 includes a lens system

708, a cover plate 702, an image sensor array 704, and

sensor electronics 706.

The lens system 708 includes a plurality of lenses 714

mounted on a lens mount 710. The lens system 708 may also

include other lensing elements, such as a filter or a

polarizer 712. The contoured cover plate 702 acts as an

additional lensing element.

FIG. 7B shows a block diagram of the image sensor

camera system 700. The camera system 700 receives optical image data 716. The optical data 716 are focused by the

lens system 708 and the contoured cover plate 702 onto the

image sensor array 704. The sensor electronics 706 converts

electrical charge falling on the sensor array 704 to digital

image data 718.

Although only a few embodiments have been described in

detail above, those of ordinary skill in the art certainly

understand that modifications are possible. For example, a

contouring can be done on both surfaces of the cover plate.

Also, while the preferred aspect shows only a square and a

circular mounting structures, mounting structures of other

shapes are possible, such as a hexagonal- or octogonal-

shaped mounting structure. In addition, other alignment

marks or lens locking mechanisms can be used on the cover

plate to securely attach the lens system to the cover plate.

All such modifications are intended to be encompassed within

the following claims, in which:

Claims

What is claimed is:

1. A cover for an image sensor array, the cover

comprising:

a plate formed of substantially transparent material

and placed adjacent to the image sensor array, said plate

having a plurality of surfaces forming a lensing structure,

such that at least one of said plurality of surfaces is

contoured into a lensing surface capable of changing imaging

characteristics.

2. The cover of claim 1, wherein said plate is made

of a transparent material which is one of glass, plastic, or

plexiglass, said plate being transparent over all, or a

substantial portion of, the image sensor array.

3. The cover of claim 1, wherein said lensing

structure is made of at least one lensing element, said

lensing structure covering all or a substantial portion of

the image sensor array, such that said at least one lensing

element is formed on the lensing surface.

4. The cover of claim 3, wherein said at least one

lensing element is a refractive lensing element.

5. The cover of claim 4, wherein said refractive

lensing element includes a concave lens.

6. The cover of claim 4, wherein said refractive

lensing element includes a convex lens.

7. The cover of claim 4, wherein said refractive

lensing element forms a post having at least one lensing

surface .

8. The cover of claim 3, wherein said at least one

lensing element is a diffractive lensing element, said

diffractive lensing element blazed on the lensing surface.

9. The cover of claim 3, wherein said at least one

lensing element is a hybrid refractive-diftractive lensing

element, said hybrid lensing element being formed with a diffraction grating blazed on the refractive lensing

surface.

10. The cover of claim 1, wherein said lensing

structure is a mounting structure formed on the lensing

surface of the plate for attaching additional lensing

elements to the plate.

11. The cover of claim 10, wherein said lensing

structure also includes an alignment mark, formed on the

lensing surface, to guide the additional lensing elements

when attaching to the plate.

12. The cover of claim 10, wherein said mounting

structure is formed by a mesa-like protrusion on the lensing

surface .

13. The cover of claim 10, wherein said mounting

structure is formed by a ringed-wall structure having an

inside wall and an outside wall, said ringed-wall structure

formed on the lensing surface.

14. The cover of claim 13, further comprising a

threaded retaining ring on the inside wall for firmly

attaching the additional lensing element to the plate.

15. The cover of claim 13, further comprising a

threaded retaining ring on the outside wall for firmly

attaching the additional lensing element to the plate.

16. The cover of claim 13, wherein said mounting

structure is formed by a well-like depression on the lensing

surface .

17. The cover of claim 16, further comprising a

threaded retaining ring on the inside wall of the depression

for firmly attaching the additional lensing element to the

plate.

18. The cover of claim 3, wherein said lensing

structure is a hybrid of lensing elements and mounting

structures for additional lensing elements.

19. The cover of claim 18, further comprising an

alignment mark formed on the lensing surface to guide the

additional lensing elements when attaching to the plate.

20. A lensing structure coupled to a cover for an

image sensor array, the structure comprising:

an element made of substantially transparent material

and having a lensing surface, said element formed on or with

the cover, such that said lensing surface of said element

changes the incoming light.

21. The structure of claim 20, wherein the lensing

structure and the cover is injection molded into a single-

piece cover plate.

22. The structure of claim 20, wherein the changing

includes said element functioning as an additional lensing

element .

23. The structure of claim 20, wherein the changing

includes said element functioning as a mounting structure or

alignment marks to attach other lensing elements to the

cover .

24. The structure of claim 20, wherein the image

sensor array is a charge-coupled device sensor array.

25. The structure of claim 20, wherein the image

sensor array is an active pixel sensor array that has a

follower transistor and a selection transistor in each

pixel .

26. An image sensor camera system for converting

optical data into digital image data, the system comprising:

an image sensor array having a plurality of sensors,

said sensors operating to receive the optical data and

integrate the data into electrical charge proportional to

the amount of optical data collected within a particular

period of time; a lens system operatively coupled to the image sensor

array and configured to carry and focus the optical data

onto the image sensor array, said lens system including a

plurality of lenses and a cover plate, said cover plate

contoured into a lensing structure that changes an imaging

characteristic; and

sensor electronics coupled to the image sensor array,

and configured to receive the electrical charge, the sensor

electronics operating to convert the electrical charge

received by the plurality of sensors into the digital image

data.

27. An active pixel sensor system having an active

pixel array, the system comprising:

a lensing element configured to receive optical data

and change an imaging characteristic, said lensing element

providing cover for the active pixel array.

28. A method of contouring an image sensor array cover

plate for imaging improvement or enhancement function, the

method comprising: forming a lensing structure on a lensing surface of the

cover plate by contouring said lensing surface of the cover

plate into a lensing element .

29. The method of claim 28, wherein forming a lensing

structure includes blazing diffraction grating on said

lensing surface.

30. The method of claim 28, wherein said lensing

structure is attached to said cover plate.

31. The method of claim 28, wherein said lensing

structure and said cover plate are injection molded as a

single-piece structure.