JPS633265B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tester for determining the quality of a solid-state image sensor, and more particularly to a tester that can accurately test the blooming phenomenon of a solid-state image sensor.

<Background of the Invention> Solid-state imaging devices have been developed and are being put into practical use for the purpose of downsizing and reducing power consumption of television cameras. As is well known, in a solid-state image sensor, a large number of photoelectric conversion cells made of semiconductor are arranged on one side, and the photoelectric conversion cells are sequentially selected one by one according to a selection signal and irradiated onto the photoelectric conversion cells. A pixel signal corresponding to the amount of light is obtained, and the selection of the photoelectric conversion cells is sequentially switched to perform surface scanning to obtain an image signal.

Scanning of the image signal by selecting the photoelectric conversion cell is performed by transferring the charge output depending on the amount of light received by the photoelectric conversion cell to the potential well of the CCD or MOS, regardless of whether the solid-state image sensor is a CCD type or a MOS type. This is done by storing the wells and transferring them one after another to the neighboring potential wells. There is a limit to the capacity of such optical signal charges to be accommodated in the potential well, and when a photoelectric conversion cell is partially irradiated with a light spot with high illuminance, the amount of charge overflows from the potential well.
In this case, the charge overflowing from the potential well will also flow into the adjacent potential well. In other words, optical signal charges are accommodated even in areas where the optical signal is not irradiated, resulting in a distorted image. This phenomenon is called blooming.

FIG. 1 shows a conventional imaging device tester that can test the blooming of solid-state imaging devices. In the figure, 101 indicates a solid-state image sensor to be tested. 1
02 indicates a drive circuit that provides a cell selection signal to the solid-state image sensor 101. The driving circuit 102 selects the solid-state image sensor 101 according to the arrangement of its respective photoelectric conversion cells, and obtains pixel signals one after another.

Pixel signal 10 obtained from solid-state image sensor 101
3 is amplified by a preamplifier 104 and provided to an AD converter 105. The AD converter 105 receives clock pulses 100 from the drive circuit 102.
The pixel signal is AD-converted in synchronization with, for example, a 10-bit digital pixel signal.

The digital pixel signal AD-converted by the AD converter 105 is taken into the data memory 106. The data memory 106 counts the clock pulses applied from the drive circuit 102 with an address counter 107, and the address is sequentially incremented by one address based on the count output, and the digital pixel signals output from the AD converter 105 are sequentially stored.

The digital pixel signals taken into data memory 106 are sequentially transferred to data processor 108. This data processor 108 has various comparison and determination means, and uses this determination means to determine the quality of the photoelectric conversion cell and the quality of the solid-state image sensor 101 as a whole.

109 is a controller. This controller 109 starts and stops the drive circuit 102 and controls the data processor 108. Further, the controller 109 provides a control signal to the light source 111 to control the amount of light and the mechanical position.

In this conventional imaging device tester, a blooming test of a solid-state imaging device is performed as follows. FIG. 2 is a diagram for explaining the operation of this blooming test.

A light source 11 is provided on the imaging surface of the solid-state image sensor 101 under test.
From 1 onwards, a spot light with high illuminance is irradiated. The area irradiated with this spot light is indicated by SP in FIG. Blooming occurs as a, b,
It appears like c. In order to test the occurrence of this blooming, its magnitude, direction, etc., we focused on certain areas E ₁ and E ₂ within the imaging plane, and measured the pixel signals in these areas E ₁ and E ₂ when no spot light was irradiated. and area E ₁ when spot light is irradiated,
The pixel signal in _E2 is compared.

That is, pixel signals are output from the solid-state image sensor 101 under test by the drive circuit 102, and these signals are
The data is AD converted by the AD converter 105 and stored in the data memory 106. The area is read from the data memory 106 by the control signal of the controller 109.
Digital pixel signals corresponding to E ₁ and E ₂ are transferred to data processor 108 . Next, the light source 111
A strong spot light is irradiated onto the solid-state image sensor 101 to be tested, and each pixel signal at that time is similarly outputted one after another, AD converted, and stored in the data memory 106. The digital pixel signals corresponding to areas E ₁ and E ₂ at this time are transferred to the data processor 108 and compared with the previous data.

By repeating this operation while changing the illuminance of the spot light and the position of the area of interest, it is possible to test the occurrence of blooming, its magnitude, direction, etc.

However, in this imaging device tester, it is not possible to obtain sufficient mechanical precision when irradiating the spot light from the light source 111 to the solid-state image sensor 101, and therefore it is difficult to accurately set the position of the spot light. Can not. Therefore, the above area
When determining E ₁ , E _{2 ,} etc., the areas E ₁ and E ₂ must be determined at a certain distance L from the position SP where the spot light is irradiated, taking into account the positional shift of the spot light. . This is to prevent the data of the position SP itself irradiated with the spot light from being included in the data of the areas E ₁ and E ₂ due to the positional shift of the spot light.

In this way, since the data of the position more than the distance L from the position SP where the spot light is irradiated is used, the blooming that occurs within the distance L,
For example, blooming as shown in a in FIG. 2 cannot be detected. That is, the conventional imaging device tester has a drawback that it cannot detect small blooming such as when a blooming phenomenon starts to occur.

<Object of the Invention> The present invention aims to provide an imaging device tester that can detect even a small blooming phenomenon as described above and can also test its size.

<Summary of the Invention> According to the present invention, a digital pixel signal corresponding to each pixel is obtained by irradiating a solid-state image sensor under test with low-intensity spot light that does not cause blooming, and a spot light is detected using this digital pixel signal. Information indicating the position of the light is obtained and this information is stored in the mask memory. Next, the illuminance of the spot light is increased, and a digital pixel signal corresponding to each pixel at that time is obtained and stored in the data memory. When calling the data stored in the data memory to determine blooming, this data memory and the mask memory are accessed in common, and when information indicating the spot light position is obtained from the mask memory,
The data from the data memory at that time is prohibited and is not subject to determination.

By doing this, it is possible to accurately distinguish between the positions on the solid-state image sensor under test that are irradiated with spot light and those that are not irradiated with spot light, so even extremely small blooming, such as the beginning of blooming, can be detected. can be measured.

<Embodiment of the Invention> FIG. 3 shows an embodiment of the imaging device tester according to the invention. In FIG. 3, parts common to those in FIG. 1 are given the same numbers as in FIG. 1.

In FIG. 3, 201 is a comparator that compares each digital pixel signal read from the data memory 106 with a reference level set by the controller 109, and when the digital pixel signal is greater than the reference level, for example, 1", and if it is small, outputs "0".

202 is a mask memory and data memory 10
6 is given the same address as data memory 1.
The digital pixel signal of 06 is set to “1” by the comparator.
Or, when it is classified as "0", that "1" or "0" is stored in a position corresponding to the address of the data memory at that time.

203 is an inhibition circuit to which the digital pixel signal from the data memory 106 and the signal from the mask memory 202 are applied. For example, when the signal from the mask memory 202 is "1", the data memory 10
The digital pixel signals from 6 are inhibited from being provided to data processor 108.

In this example, the blooming test is conducted as follows.

A light source 111 is controlled by a controller 109 to irradiate a desired position of the solid-state imaging device under test with spot light. The illuminance from the light source at this time is normal illuminance, which is much lower than the level at which blooming occurs. Driven by the drive circuit 102, pixel signals from each pixel of the solid-state image sensor at this time are sequentially extracted and sent to the AD converter 1.
05, the signal is converted into a digital signal and stored in the data memory 106.

When each digital pixel signal has been stored in the data memory 106 in this way, the digital pixel signal is read out from the data memory 106 under the control of the controller 109 and applied to the comparator. A reference level is given to the comparator 201 from the controller 109, and the value of each digital pixel signal is compared with this reference level to see if it is larger. This reference level is a level for distinguishing between a part of the solid-state image sensor 101 under test that is irradiated with spot light and a part that is not irradiated with it, and for example, a digital pixel signal that should be obtained from a pixel that is irradiated with spot light. and the digital pixel signal that should be obtained from pixels not irradiated with spot light.

In this way, each digital pixel signal is compared with the reference level, outputted from the comparator 201 as a "1" or "0" signal, and applied to the mask memory 202. The mask memory is accessed by the controller 109 at the same address as the data memory 106, and the "1" or "0" signal obtained from the comparator 201 is stored at that address. Therefore, when the digital pixel signal read from a certain address in the data memory 106 is higher than the reference level, for example, "1" is stored in the mask memory 2.
02 is stored at the same address.

The data stored in the mask memory in this way ultimately indicates the position of the solid-state image sensor under test that is irradiated with the spot light.

Next, under the control of the controller 109, the light source 11
The illuminance of 1 is increased to such an extent that blooming occurs, and each pixel signal is similarly AD converted and stored in the data memory 106 as a digital pixel signal.
For various tests on the blooming phenomenon, this digital pixel signal is read out from the data memory 106 and transferred to the data processor 108. At this time, the data stored in the mask memory 202 is also read out and transferred to the mask memory 108. When the data from 202 is "1", the prohibition circuit 203 prohibits the transfer of the digital pixel signal to the data processor 108.

In this way, the digital pixel signals of the pixels illuminated by the spot light are accurately distinguished and their transfer to the data processor 108 is prohibited.

In other words, the spot light position is first set and the spot light of normal illuminance is irradiated, and then only the illuminance of the spot light is increased to obtain data regarding blooming, so the mechanical position of the spot light during that time is The data corresponding to the position of the spot light can be inhibited accurately by the inhibition information obtained in the mask memory without any change.

The digital pixel signals thus obtained in the data processor 108 are designated, for example, as shown in FIG. Detection of blooming by comparing with each other
Its size and direction can be tested. At this time, as mentioned above, since the spot light position can be accurately distinguished, data at a point slightly distant from the spot light position can be accurately obtained, and therefore, for example, small blooming phenomena such as the beginning of blooming can be accurately measured. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a conventional imaging device tester, FIG. 2 is a conceptual diagram for explaining the operation when performing a blooming test using the conventional imaging device tester shown in FIG. 1, and FIG. The figure is a block diagram showing an embodiment of an imaging device tester according to the present invention. 101; solid-state image sensor to be tested, 102; drive circuit, 105; AD converter, 106; data memory, 108; data processor, 109; controller, 111; light source, 201; comparator, 20
2; Mask memory, 203; Prohibition circuit.

Claims (1)

[Scope of Claims] 1. An imaging device tester that applies an optical signal from a light source to an imaging device and determines the quality of the imaging device based on data output from the imaging device, which includes: The pixel signals obtained from each photoelectric conversion cell according to the amount of light received are sequentially AD converted.
an AD converter, a data memory that stores digital pixel signals corresponding to the pixel signals of each photoelectric conversion cell output from the AD converter, and each digital pixel signal stored in the data memory has a predetermined standard. a comparator for comparing whether or not the signal is greater than the level; and a measurement prohibition signal is stored at the same address as the address of the data memory where the digital pixel signal is stored when the comparison signal is output from the comparator. a mask memory; and a prohibition circuit that prevents a digital pixel signal read from the data memory from being measured when a signal from the mask memory read at the same address is a measurement prohibition signal; An imaging device tester comprising: a determining means for performing various tests on the imaging device under test using digital pixel signals obtained through the digital pixel signal and determining whether the imaging device is good or bad.