Image analysis – Applications – Manufacturing or product inspection
Reexamination Certificate
2000-06-29
2004-03-02
Mehta, Bhavesh M. (Department: 2625)
Image analysis
Applications
Manufacturing or product inspection
C382S141000, C382S216000, C382S286000, C382S294000, C438S016000, C438S018000, C700S096000, C700S121000
Reexamination Certificate
active
06701002
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
1. Field of the Invention
The present invention relates to a test method for semiconductor image pickup devices, and more particularly relates to a method used for tests in which certain areas within an image plane of an image pickup device are specified for testing.
2. Description of the Related Art
Previously, in testing solid-state image pickup devices such as a CCD which constitutes and outputs a image data by using photo sensors arranged one-dimensionally or two-dimensionally, in addition to ordinary test items for integrated circuits, it is required to find the number of damaged portions on the pickup screen, kinds of sensitivity irregularities called “shading” or the like by various image processing calculations, and to judge the quality of the image pickup device. In the mass production test, in order to shorten the image processing time for a vast number of pixels, test equipment has often been equipped with specialized hardware for an image pre-processor which performs, for example, the sensitivity compensation corresponding to the color by taking out pixels in specified areas or the like as shown in Japanese Patent Publication for opposition (Kokoku) No. 1-61279.
When developing test procedures using such test equipment, in order to obtain the exact number of pixel data in row and column of an image pickup device and reference levels, it has been required for the test engineer to set the principal definitions of the coordinates of the start and end points of the optical black area (area optically masked) provided on the image pickup device, the coordinates of the start and end points of the pixel area where the color filter is arranged, the ordering of different color filters or the like to the hardware in the test equipment, and to construct a test program. However, recently, along with progresses in the area of digital still camera and CMOS image sensors, image pickup devices having a lot of pixels and a complex picture constitution have become common, and accordingly, it has increasingly become impossible to deal with testing requirements with specialized hardware only, and in such cases, some extra peripheral circuits or software processing has been added after hardware pre-processing to deal with tougher requirements, and the test development work has become considerably more tedious.
On the other hand, with the recent improvement of the computer technology for the multimedia or the like, it has become possible to obtain an image processing time comparable to that of a test using specialized hardware with the software processing alone, and special hardware is no longer essential for testing units in many instances. This removes limitations resulting from hardware functionalities and improves the flexibility. On the contrary, however, the setting of pixel areas and the image processing may be different depending the test engineer who develops the test define such tests. This can be a factor in preventing the test program from being reused.
According to the example disclosed in Japanese Patent Publication for Opposition No. 1-61279, a mask memory corresponding to each pixel of an image pickup device is prepared, and the definitions of the optical black and the color of the color filter are written therein. If there is a mask memory which corresponds one-to-one to each pixel, an area with an arbitrary shape can be specified, but actually, the specification is made such that the mask memory is set in rectangular areas specified by (1) the start coordinate, (2) the width, and (3) the height of the area. In many cases, simply such areas as area
101
and area
102
shown in
FIG. 1
are specified. Since it is impossible to perform image processing by dividing areas more finely with hardware only, such divisions are described using software. It is, however, difficult to grasp the relationship between any two areas, making the test development work troublesome. Furthermore, in order to specify an area left after a rectangle area is cut out, many rectangles have to be connected to define such an area, again. For example, when specifying area
103
in FIG.
1
, it is necessary to connect a total of 5 rectangular areas including an upper rectangle, an area between areas
101
and
102
, a rectangle on the left side of area
101
, a rectangle on the right side of area
102
, and a lower rectangle. Setting and changing specified areas become extremely troublesome.
Moreover, it is often necessary to further divide the area where the color filter is arranged (in case of black-and-white image pickup devices, a part which is not optical black) into several areas and perform the image processing corresponding to each area. For example, in “zoning rules of shading of image signals” shown on Page 9 of the data sheet for a solid-state image pickup device ICX205AK published by Sony Corporation (in Japanese), it is specified to divide an area into 3 areas as shown in FIG.
2
. In a testing unit described in Japanese Patent Publication for Opposition No. 1-61279, the masking of the disregarded area only can be performed by hardware processing, and therefore, it is necessary to separately define specifications using software processing after the hardware processing, in order to extract data for zones II and II′.
As for the division of color filter areas, as shown in the “Color Signal Evaluation Method” of Japanese Patent Publication for Opposition (Kokoku) No. 3-101582, an area is divided into a central part and several small peripheral parts. As shown in
FIG. 3
, however, if area
201
of the most important central part is taken first, and if the middle part left after cutting out the outermost peripheral area
206
is divided into 4 pieces in the four corner directions, the pieces are processed as areas
202
,
203
,
204
,
205
. Then, the specifications of a number of non-rectangular areas would become necessary, and descriptions using software also become complex. Furthermore, depending on the way of using an image pickup device to be tested, the size of the central area
201
changes, and depending on the manufacturing process for color filters, such adjustments as increasing the width of the peripheral area
206
to be cut out are often required, consuming considerable man-hours.
With a descriptive method similar to sequential programming which is common in the digital test, it is also possible to deal with shapes other than rectangles. That is, in addition to the specifications of (1) the start coordinate, (2) the width, and (3) the height, by accepting (4) the number of repeats and (5) subroutine calls, it is possible to describe various shapes including simple rectangular areas and complex polygons or a collection of discrete points in terms of software programs. Alternatively, only for the areas which are not rectangular and cannot be described by the conventional specification of (1) the start coordinate, (2) the width, and (3) the height, a pattern is generated by another program, and the result thereof is read into such a device as a “mask memory” described in the test equipment of Japanese Patent Publication for Opposition No. 1-61279, or numerical values may be stored in array valuables corresponding to a mask memory to be referred to for software processing, so that the area may be specified.
FIG. 11
shows the flow of processing image pickup device data according to conventional methods. After retrieving data
601
from an image pickup device which is simple one-dimensional dump data, mask data stored in coordinates of a mask memory for each data is retrieved while counting addresses with a horizontal address counter
605
and a vertical address counter
606
, and it is checked (
607
) whether such data matches the attributes of a desired area specification or not (
608
) (in this case, whether or not the attribute is an “AC” indicating an active area), and when it matches the attribute, the image pickup device data is passed to the next processing as selected data
602
. Next, this selected data
602
is s
Agilent Technologie,s Inc.
Kassa Yosef
Mehta Bhavesh M.
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