Long-length industry camera image sensor for flat surface inspection application

A long-length industry camera image sensor (LICIS) is proposed for, expressed in X-Y-Z coordinates, converting a pixel line image (PLI) of length LPL along X-direction into a line image signal (LIS). The LICIS includes a full-width linear image sensor (FLIS) of length LIS along X-direction and displaced from the PLI along Z-direction by an imaging distance DIMG for converting an incident line image (ILI) impinging upon its FLIS top surface into the LIS. Where LIS is about equal to LPL. The LICIS also has a full-width linear rod lens (FLRL) of length LRL along X-direction and displaced from the PLI in Z-direction by a working distance DWKG. Where LRL is about equal to LPL and DWKG is selected such that the PLI gets focused by the FLRL into the ILI at the FLIS top surface with an imaging magnification factor of about 1:1.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electronic imaging. More particularly, the present invention is related to an I-CIS (Industrial Camera Image Scanner) such as used for large flat panel inspection.

2. Related Background Art

A prior art camera image scanner configuration for industrial application is illustrated in FIG. A. Such industrial application includes, for example, the real-time inspection of large liquid crystal display (LCD) production panels, thin film solar panels and textile production webs. Here, an object surface located in an object plane is, while being illuminated by an Illumination Source, imaged by a charge coupled device (CCD) Image Sensor located at an “Imaging Distance” away from the object plane (along Z-direction). While not specifically illustrated here, to those skilled in the art a real inspection of the object surface can be accomplished by imaging the object surface on a scan-line by scan-line basis, with each scan line width labeled “Object Image Width” (X-direction), while providing a controlled relative motion (along Y-direction) between the object surface and the CCD Image Sensor. In an industrial application, the Object Image Width can be easily as large as 36″ to 72″. As the “Image sensor Width” of a single CCD Image Sensor is only in the range of 1″ to 2″ that is substantially smaller than the Object Image Width, an intervening focusing optical path with a Focusing Lens effecting a tiny magnification factor (1:72 to 1:18) is required between the object plane and the imaging surface of the CCD Image Sensor. Given the large Object Image Width and tiny magnification factor, the resulting Imaging Distance lies typically in the range of 10-30 cm.

FIG. B is a basic lens ray diagram for the focusing optical path of the prior art camera image scanner configuration of FIG. A. In addition to a Normal Imaging Light Ray along the Z-axis, a large number of Oblique Imaging Light Rays, each at an Oblique Angle θ from the Normal Imaging Light Ray, need to be focused between the CCD Imaging surface and the Object Plane as well. As the Oblique Angle θ becomes progressively larger toward the edge of the object plane, in the absence of any so-called f-θ compensation in the Focusing Lens design the Oblique Imaging Light Rays would become progressively out of focus as illustrated by the dashed arc tangential to the object plane. Given the imaging geometric parameters involved the Oblique Angle θ can become as large as 60 to 70 degrees where the degree of f-θ compensation can become unacceptable even with an expensive f-θ Focusing Lens. Additionally, it is known in the art that the imaging light intensity falls off toward the edge of the object plane following the cosine-law below:
Intensity(θ)=I0×cos4(θ)
Where I0is the imaging light intensity at θ=0 degree. Thus, for example, at θ=60 degree Intensity (60 degree)=6.25%×I0. Such a loss of imaging light intensity near the edge of the object plane is most likely unacceptable in that its associated image signal level and signal-to-noise ratio (S/N) would be too low.

FIG. C illustrates another prior art wherein multiple line cameras (Camera-1, Camera-2, Camera-3, etc.) are juxtaposed with a camera pitch along the object image width for large flat panel inspection. Thus, for each camera, the magnification factor is proportionally increased while the Oblique Angle α, is proportionally reduced with the total number of cameras. With the reduction of Oblique Angle α, the problems of f-α compensation and image signal level fall-off at the edges are correspondingly reduced. However, accompanying the increasing number of cameras are disadvantages of bigger overall camera image scanner size, complication of required precision inter camera alignment for image stitching and inter camera imaging parallax error.

Accordingly, it is a primary object of the present invention to provide an Industrial Camera Image Scanner that is compact, having a short Imaging Distance and requiring only simple intervening focusing optical path and simple imaging signal processing.

SUMMARY OF THE INVENTION

A long-length industry camera image sensor (LICIS) is proposed for, expressed in an X-Y-Z Cartesian coordinate system, converting a pixel line image (PLI) of length LPLalong the X-direction into a corresponding line image signal (LIS). The LICIS includes:a) A full-width linear image sensor (FLIS) of length LISalong the X-direction and displaced from the PLI along the Z-direction by an imaging distance DIMGfor converting an incident line image (ILI) impinging upon its FLIS top surface into the LIS. Where LISis about equal to LPL.b) A full-width linear rod lens (FLRL) of length LRLalong the X-direction and displaced from the PLI in the Z-direction by a working distance DWKGwith DWKG<DIMG. Therefore the FLRL is located between the PLI and the FLIS. Where LRLis about equal to LPLand DWKGis selected with respect to DIMGsuch that the PLI gets focused by the FLRL into the ILI at the FLIS top surface with an imaging magnification factor of about 1:1. In a more specific embodiment, the imaging magnification factor is set to be from about 0.8:1 to about 1.2:1.

In a more specific embodiment, the FLIS includes a multi-segment stitched sensor base board (SSBB) having numerous linearly stitched sensor board segments SBSj, j=(1, 2, . . . , M) where M>=1. Each SBSjconverts an incident line image segment (ILIj) of the ILI into a corresponding line image signal segment (LISj) of the LIS.

In a more specific embodiment, each SBSjfurther includes:A base board (BBj).Numerous linearly stitched linear sensor integrated circuit LSICjk, k=(1, 2, . . . , N) located atop the base board where N>=1. Each LSICjkconverts an incident line image segment (ILIjk) of the ILIjinto a corresponding line image signal segment (LISjk) of the LISj. In one embodiment, each LSICjkis made of a linear CMOS sensor integrated circuit.

In a more detailed embodiment, each BBjfurther includes, along the X-direction, a left-end anti-bumping profile and a right-end anti-bumping profile. The left-end anti-bumping profiles and the right-end anti-bumping profiles are shaped and sized such that, when the BBjand BBj+1are stitched together, the right-end anti-bumping profile of BBjwill engage the left-end anti-bumping profile of BBj+1and accordingly guaranteeing the following:A minimum X-direction inter-IC clearance (IICX) between LSICjNand LSICj+1,1.A maximum Y-direction inter-IC offset (IIOY) between LSICjNand LSICj+1,1.
In a more specific embodiment, the IICXis from about 10 micron to about 30 micron while the IIOYis from about 0 micron to about 30 micron.

In a more detailed embodiment, for enclosing the FLIS and the FLRL while affixing them with respect to each other, the LICIS further includes a structured housing having:A housing base lying in the X-Y plane for seating the FLIS.Two housing side walls plus a top cover running along the X-axis for enclosing the FLIS and the FLRL. The top cover has a transparent central portion for passing through imaging lights near an optical imaging axis along the Z-direction and reaching the FLRL.

In an important embodiment:The width of the top cover along the Y-direction is, while avoiding significant blockage of the imaging lights through it, minimized to become narrower than a corresponding width of the housing base.Correspondingly, the upper portions of both housing side walls are tapered from the housing base toward the top cover so as to minimize the blockage of lateral illumination lights originated near the housing base and aiming at a reflective surface being imaged above the LICIS.

These aspects of the present invention and their numerous embodiments are further made apparent, in the remainder of the present description, to those of ordinary skill in the art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The description above and below plus the drawings contained herein merely focus on one or more currently preferred embodiments of the present invention and also describe some exemplary optional features and/or alternative embodiments. The description and drawings are presented for the purpose of illustration and, as such, are not limitations of the present invention. Thus, those of ordinary skill in the art would readily recognize variations, modifications, and alternatives. Such variations, modifications and alternatives should be understood to be also within the scope of the present invention.

FIG. 1illustrates the present invention long-length industry camera image sensor (LICIS)1for converting a pixel line image (PLI)109of length LPLalong the X-direction into a corresponding line image signal (LIS)110. The pixel line image (PLI)109is part of an object plane92made visible by an illumination source90located nearby and oriented along the X-direction.

The LICIS1has a full-width linear image sensor (FLIS)5of length LISalong the X-direction and displaced from the pixel line image (PLI)109along the Z-direction by an imaging distance DIMGfor converting an incident line image (ILI)102impinging upon its FLIS top surface8into the line image signal (LIS)110. The LICIS1also has a full-width linear rod lens (FLRL)12of length LRLalong the X-direction and displaced from the pixel line image (PLI)109in the Z-direction by a working distance DWKGwith DWKG<DIMG. The FLRL12is therefore located between the pixel line image (PLI)109and the FLIS5. Notably, length LRLis selected to be about equal to length LPLand the working distance DWKGis correspondingly selected with respect to DIMGsuch that the pixel line image (PLI)109gets focused by the FLRL12into the incident line image (ILI)102at the FLIS top surface8with an imaging magnification factor of about 1:1. As a reference, the imaging magnification factor is defined to be:
imaging magnification factor=LIS/LPL
In a more specific embodiment, the imaging magnification is set to be from about 0.8:1 to about 1.2:1.

FIG. 2illustrates the focusing optical path93of the present invention LICIS1with the FLRL12effecting a magnification factor of about 1:1. Thus the FLRL12, being a critical functional part along the focusing optical path93, focuses the pixel line image (PLI)109on the object plane92into the incident line image (ILI)102on the image plane94. In one embodiment, as illustrated, the FLRL12is made up of an array of rod lenslets14along the X-direction and each rod lenslet14is a GRIN (gradient index) lens. In practice, for an imaging magnification from about 0.8:1 to about 1.2:1, the FLRL12is characterized by the following parameters:rod lens thickness (RLT)=1 cm-2 cmDWKG˜0.5 cm-2 cmfocal length (FCL) ˜0.5 cm-2 cmDIMG=2 cm-4 cm
Comparing the above DIMGof 2 cm-4 cm with the Imaging Distance of 10 cm-30 cm of FIG. A shows that the present invention LICIS1with a magnification factor of about 1:1 can be a lot more compactly packaged than the prior art camera image scanner configuration with a tiny magnification factor of 1:72 to 1:18. Secondly, as the focusing optical path93of the present invention LICIS1can be seen to be dominated by paraxial rays, the previously mentioned need of f-θ compensation and cosine-law fall off of the imaging light intensity toward the edge of the object plane92have both become insignificant resulting in a correspondingly improved imaging quality here. Thirdly, the single-camera configuration here has avoided numerous complications associated with the prior art multiple line camera system of FIG. C as well. Fourthly, under the 1:1 imaging system the required FLIS5spatial resolution only needs to be about the same as the pixel line image (PLI)109. Whereas, in a prior art 1:72 imaging system the required CCD Image Sensor spatial resolution would have to be about 72 times higher than the original Object Image.

FIG. 3AandFIG. 3Brespectively illustrates top and bottom views of the LICIS1.FIG. 3Cillustrates a cross sectional view, along section A-A ofFIG. 3A, of the LICIS1with an optionally added strutted base bracket22. The FLIS5includes a multi-segment stitched sensor base board (SSBB)6seating numerous linearly stitched linear sensor integrated circuits LSIC7, to be presently described in more detail.

The LICIS1has a structured housing20for enclosing the FLIS5and the FLRL12and affixing them with respect to each other. The structured housing20has:A housing base20alying in the X-Y plane for seating the FLIS5. A number of line image signal connectors (LISC)112and a power and control connector114are provided at the housing base20afor interfacing and powering the FLIH1in its application environment.Two housing side walls20bplus a top cover20crunning along the X-axis for enclosing the FLIS5and the FLRL12. The top cover20chas a transparent central portion for passing through imaging lights96near an optical imaging axis97along the Z-direction and reaching the FLRL12. Thus, running through the center of the top cover20cin the X-direction is an image scan line98of the LICIS1. The transparent central portion has a cover glass16held in place by a cover glass holder17. Notice the top cover width TCW is narrower than the housing base width HBW and, correspondingly, the two housing side walls20bare tapered toward the top cover20cwith a taper angle θ and this will be presently explained.
Although optional, for the purpose of external mounting in an application environment, the LICIS1can include a strutted base bracket22having numerous mounting holes22d. Mounting holes20dare provided on the structured housing20for attaching it to the strutted base bracket22.

FIG. 4AandFIG. 4Billustrate the application of the LICIS1in a reflective (FIG. 4A) and a transmissive (FIG. 4B) inspection mode. Thus, under the reflective mode ofFIG. 4A, illumination sources90and the FLIH1are placed at the same side of a reflective object99. Whereas, under the transmissive mode ofFIG. 4B, illumination source90and the LICIS1are placed at the opposite sides of a transmissive object100. Hence, in the reflective mode, to prevent the structured housing20from significantly blocking imaging lights96travelling from illumination sources90near the housing base20ato an object plane92of the reflective object99, the two housing side walls20bare tapered toward the top cover20cwith a taper angle θ from the optical imaging axis97. On the other hand, with the illumination source90and the LICIS1placed at the opposite sides of the transmissive object100under transmissive mode, the tapering of two housing side walls20bbecomes unimportant.

FIG. 5AthroughFIG. 5Dillustrate the mechanical makeup of the multi-segment SSBB6of the LICIS1for photoelectrically sensing the ILI102. As mentioned before inFIG. 3C, the SSBB6seats numerous linearly stitched linear sensor integrated circuits LSIC7. More specifically, the SSBB6has a number of linearly stitched sensor board segment SBS16A, sensor board segment SBS26B, sensor board segment SBS36C, . . . , sensor board segment SBSM6M where M>=1. Thus, each SBS converts an incident line image segment of the ILI102into a corresponding line-segment image signal of the LIS110(FIG. 1). Examples are: sensor board segment SBS16A converts incident line image segment ILI1102A into line-segment image signal (LSIS1)104A, sensor board segment SBS26B converts incident line image segment ILI2102B into line-segment image signal (LSIS2)104B, sensor board segment SBS36C converts incident line image segment ILI3102C into line-segment image signal (LSIS3)104C, . . . , sensor board segment SBSM6M converts incident line image segment ILIM102M into line-segment image signal (LSISM)104M. In turn, an enlarged representative sensor board segment SBS36C is illustrated to have a base board BB37C with numerous stitched linear sensor integrated circuit LSIC7C1, linear sensor integrated circuit LSIC7C2, linear sensor integrated circuit LSIC7C3, . . . , linear sensor integrated circuit LSIC7CN located atop. Thus, each linear sensor integrated circuit LSIC (7C1,7C2, . . . ) would further convert an incident line image segment (1031,1032, . . . ) of the incident line image segment ILI3102C into a corresponding line-segment image signal. The reason for the just described scheme of photoelectrical conversion via stitching with numerous LSICs as building blocks is that the length of each LSIC is, under state of the art semiconductor chip manufacture technology, limited to a few inches whereas the required length LISof the full-width linear image sensor (FLIS)5can be easily as large as 36 to 72 inches. In a preferred embodiment the base board can be made of a printed circuit board (PCB) or a ceramic circuit substrate and the LSIC can be made of a linear CMOS sensor integrated circuit.

Notice each base board (7B,7C, etc.) has a left-end anti-bumping profile200C and a right-end anti-bumping profile300C with enlarged views shown inFIG. 5BthroughFIG. 5D. The rightmost LSIC elements atop base board BB27B are LSIC7BN-1and LSIC7BN whereas the leftmost LSIC elements atop base board BB37C are LSIC7C1and LSIC7C2. The right-end anti-bumping profile300B is shaped with protruded anti-bumping edge (PABE)302B and recessed offset control edge (ROCE)304B. Correspondingly, the left-end anti-bumping profile200C is shaped with recessed anti-bumping edge (RABE)202C and protruded offset control edge (POCE)204C respectively engaging with the protruded anti-bumping edge (PABE)302B and the recessed offset control edge (ROCE)304B to prevent the LSIC7BN and the LSIC7C1from bumping thus damaging each other along the X-direction during assembly and from displacing from each other with an otherwise excessive amount of offset along the Y-direction. The rightmost photoelectric sensor pixels of the LSIC7BN are labeled as8BN-2,8BN-1and8BN whereas the leftmost photoelectric sensor pixels of the LSIC7C1are labeled as8C1and8C2displaced from (8BN-2,8BN-1,8BN) with a Y-direction inter-IC offset (IIOY) causing an inter-sensor board segment (inter-SBS) image offset that should be minimized for high image quality. Hence, upon engagement of the ROCEs304B with the POCEs204C the Y-direction inter-IC offset (IIOY) is guaranteed not to exceed a pre-determined maximum value. Similarly, the center-to-center spacing between sensor pixel8BN and sensor pixel8C1should be made as close to the on-chip, precision center-to-center inter-sensor pixel spacings (for example, between sensor pixels8BN-1and8BN and likewise between sensor pixels8C1and8C2). Hence, upon engagement of the PABEs302B with the RABEs202C the X-direction inter-IC clearance (IICX) is guaranteed not to fall below another pre-determined minimum value for acceptable uniformity of inter-sensor pixel spacing. In a more specific embodiment, the IICXcan be controlled to within a range from about 10 micron to about 30 micron while the IIOYcan be controlled to within a range from about 0 micron to about 30 micron. An advantage related to the use of the as described anti-bumping profiles (300B,200C, etc.) between neighboring SBSs is the prevention of excessive buildup of inter-SBS misalignment due to environmental variations such as temperature and humidity. By now it should become clear to those skilled in the art that a large number of variations of the specifically illustrated anti-bumping profiles (302B,304B,202C,204C), including profiles deviated from both X- and Y-direction, can be used instead to limit the inter-SBS misalignment as well.

A full width line image sensing head long-length industry camera image sensor is proposed for converting a pixel line image into a corresponding line image signal with an imaging magnification factor of about 1:1. Throughout the description and drawings, numerous exemplary embodiments were given with reference to specific configurations. It will be appreciated by those of ordinary skill in the art that the present invention can be embodied in numerous other specific forms and those of ordinary skill in the art would be able to practice such other embodiments without undue experimentation. The scope of the present invention, for the purpose of the present patent document, is hence not limited merely to the specific exemplary embodiments of the foregoing description, but rather is indicated by the following claims. Any and all modifications that come within the meaning and range of equivalents within the claims are intended to be considered as being embraced within the spirit and scope of the present invention.