JPH0161279B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tester for determining the quality of a color solid-state image sensor itself or an imaging device incorporating a color solid-state image sensor, and particularly to a tester for determining the quality of each photoelectric conversion cell of a color solid-state image sensor. The present invention aims to provide a color imaging device tester that can test the quality of cells of each color.

<Background of the Invention> Solid-state image sensors 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 using a selection signal and irradiation is applied to 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 and scanned to obtain an image signal.

Since each photoelectric conversion cell is formed on a semiconductor substrate by integrated circuit manufacturing technology, defects may occur in the photoelectric conversion cell due to inconveniences in the manufacturing process. Further, there may be a difference in photosensitive characteristics or a difference in dynamic range between the photoelectric conversion cells, or electrical leakage may occur between the cells.

In particular, in the case of a color solid-state image sensor, a color filter is placed over each photoelectric conversion cell, as shown in Figure 4, and the three colors of red (R), green (G), and blue (B) are emitted. configured to respond to Therefore, in the case of a color solid-state image sensor, it is necessary to test whether the photoelectric conversion cells assigned to each color of R, G, and B have proper photoelectric conversion characteristics for each color of light.

For this reason, for example, when testing the characteristics of photoelectric conversion cells that respond to red light, the drive circuit must be configured to select only those photoelectric conversion cells that respond to red light and obtain their photoelectric conversion output. However, scanning only specific cells in this way has the drawback that the structure of the drive circuit becomes complicated.

Furthermore, one solid-state image sensor is composed of approximately 500×500 photoelectric conversion elements, and the number of photoelectric conversion cells is a large value. Testing such a large number of photoelectric conversion cells one by one for photoelectric conversion characteristics for each color of light is quite a difficult task.

<Purpose of the Invention> The present invention makes it possible to test whether each photoelectric conversion cell has regular photoelectric conversion characteristics for each color of light even when a color solid-state image sensor is driven using a normal scanning method. The purpose is to provide a color imaging device tester.

In this invention, it goes without saying that the color solid-state image sensor itself is tested, but also a camera incorporating the solid-state image sensor is tested.

<Summary of the invention> In this invention, pixel signals of each color obtained from a color solid-state image sensor are converted into AD signals, and the AD
The converted digital pixel signal is stored in a data memory, and the control information is read out from a mask memory that stores control information in addresses corresponding to the photoelectric conversion cell positions of each color of the solid-state image sensor.The control information converts the digital pixel signal. A gate is installed to select and extract only the digital pixel signals of each color.
The digital pixel signal extracted by the data processor is compared with a reference value, and a test is performed to determine the quality of the color imaging device based on the comparison result.

Therefore, according to the present invention, even if a color solid-state image sensor is driven by a normal scanning method to obtain pixel signals of each color as a serial signal, only the signal of a desired color is extracted from the serial signal and the signal of that color is extracted. The photoelectric conversion characteristics of light can be tested. Therefore, the drive circuit for the solid-state image sensing device can be manufactured at low cost, for example by using a drive circuit commonly used in the television standard scanning system.

FIG. 1 shows an overview of the invention. In the figure, 101 indicates a solid-state image sensor to be tested. This solid-state image sensor 1
01 may be a CCD format, a MOS format, or a CPD format that has these features. The only difference between these formats is the format structure of the photoelectric conversion cell and the selection method of the photoelectric conversion cell, and it can be considered that the optical characteristics are the same.

Reference numeral 102 denotes a drive circuit that provides a cell selection signal to the solid-state image sensor 101. It is assumed that the drive circuit 102 selects and scans each of the CCD, MOS, and CPD type solid-state image sensors according to the arrangement of their respective photoelectric conversion cells, and sequentially obtains pixel signals. This scanning speed can be set equal to the standard scanning speed for television signals.

Pixel signal 10 obtained from solid-state image sensor 101
3 is amplified by a preamplifier 104 and supplied to an AD converter 105. The AD converter 105 AD converts the pixel signal in synchronization with the clock pulse applied from the drive circuit 102, and converts it into, for example, an 8-bit digital pixel signal.

The 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. As will be described later, this data processor 108 has a color signal sorting means and various comparison and determination means, which are essential parts of the present invention, and the determination means determines whether the photoelectric conversion cell is good or bad and whether the solid-state image sensor 101 as a whole is good or bad. Determine.

109 is a controller. This controller 109 starts and stops the drive circuit 102 and controls the data processor 108. Further, a control signal is given to the optical control system 111 to perform control such as gradually changing the light amount of the light source 112 as the test progresses.

Reference numeral 113 denotes a monitor, which performs DA conversion on the digital pixel signals taken into the data memory 106 and projects an image on the screen based on the pixel signals obtained from each photoelectric conversion cell.

<Detailed explanation of the data memory 106> When determining the quality of the solid-state image sensor 101 based on pixel signals obtained by a single scan in the solid-state image sensor 101, the expected value may be different from the expected value due to noise that happens to be mixed in. There is a possibility that a discrepancy will occur, and based on this, the product will be determined to be defective. In order to eliminate such inconvenience, in this example, the image sensor 10
The average value of the pixel signals of each photoelectric conversion cell obtained by scanning each photoelectric conversion cell 1 multiple times is stored in the data memory 106.

The configuration for obtaining this average value is shown in FIG.
In FIG. 2, 105 is the AD converter explained in FIG. For example, an 8-bit AD conversion output from this AD converter 105 is supplied to a data memory 106. Data memory 106 includes an adder 201 and a memory section 202. The memory unit 202 reads out the previous pixel signal that is the same as the digital pixel signal output from the AD converter 105, adds the read output and the digital pixel signal obtained this time in the adder 201,
The addition result is rewritten to the same address in the memory section 202.

Since reading and writing must be performed at high speed, in this example, the memory section 202 is divided into four memory cards 202a, 202b, 202c, and 2.
02d, and by using the plurality of memory cards 202a to 202d in a time-sharing manner, each memory card 202a to 202d is operated at a slow speed.

Each memory card 202a-202d has the same structure. In other words, memory card 202a
As shown in FIG. 2, it is composed of a card selector 203, a memory main body 204, an output latch circuit 205, and an input latch circuit 206.

The card selector 203 receives a card select signal from the control bus 207 and an address signal from the address bus 208, learns that it has been called, takes in the address signal at that time, and accesses the memory main body 204 using the address signal. do. The memory main body 204 reads the data stored at that address in the initial state of access,
The output latch circuit 205 is made to latch. The latch output is given to the adder 201, and the adder 201
, the previous and current digital pixel signals are added, and the addition result is latched in the input latch circuit 206.

When the addition result is latched in the input latch circuit 206, the card selection is moved to the next card. Therefore, each memory card 202a to 202d is an adder 2.
01 is connected to the output latch circuit 20.
5 latches the readout output of the memory main body 204 until the input latch circuit 206 latches the addition result. Immediately after the addition result is latched in the input latch circuit 206, the card latches the readout output of the memory main body 204. be separated from Therefore, the next selected memory card, for example 202b, is the adder 20.
1, the memory card 202a
The addition result latched in the input latch circuit 206 can be rewritten to the same address. Therefore, each memory card performs AD processing from reading to writing.
It is sufficient to execute the process in a time four times as long as the conversion speed of the converter 105, thereby reducing the burden on the operating speed of each memory card 202a to 202d.

In this way, each memory card 202a-20
In the memory main body 204 of 2d, the added value of digital pixel data of the same pixel each time is accumulated at the same address. Here, as a method for obtaining an average value from the added values, for example, when the output of the AD converter 105 is 8 bits, the bit capacity of the write data of the memory body 204 is set to 16 bits. In this way 8
By adding bit digital signals 128 times and extracting the upper 8 bits obtained as a carry output of the addition result, the average value of each pixel for 128 times can be obtained. This upper 8 bit data is output to terminal 2.
09, it is possible to obtain the average value of pixel data obtained by scanning the photoelectric conversion cell 128 times.

By averaging each pixel signal in this way, even if noise is mixed in, the influence of the noise can be reduced. Noise mixed into the pixel signal may occur, for example, when an object such as dust passes between the solid-state image sensor 101 and the light source 112. Therefore, if the quality of each photoelectric conversion cell is judged based on only one scan result, the result will be unreliable. However, as mentioned above, in this embodiment, the quality of each photoelectric conversion cell is determined by averaging the results of multiple scans. Since the judgment is performed, highly reliable judgment results can be obtained.

<Main part of the invention> FIG. 3 shows an embodiment of the main part of the invention. In this invention, the data processor 108 is provided with a mask memory 301 for sorting each color signal, a control signal for sorting each color signal is read out from this mask memory 301, and the gate 302 is opened/closed using this control signal. The system is configured to sort and obtain desired color signals.

That is, the mask memory 301 is a plurality of memories 301
For example, in 301R of each of these memories 301R, 301G, and 301B, an H logic control signal is written to an address corresponding to the position of a photoelectric conversion cell that responds to red light, and other L logic is written in the address corresponding to the photoelectric conversion cell of the color, and H logic is written in the address corresponding to the position of the photoelectric conversion cell that responds to green light in the memory 301G. Write L logic to the address corresponding to the position of the photoelectric conversion cell that responds. Furthermore, memory 301B
H logic is written in the address of the photoelectric conversion cell that responds to blue light, and L logic is written in the address corresponding to the position of the photoelectric conversion cell that responds to light of other colors.

In this way, for example, the memory 301R is read out in conjunction with the driving of the solid-state image sensor 101, the opening/closing of the gate 302 is controlled by the readout output signal, and the pixel signal is taken out through this gate 302, thereby making it possible to take out only the red signal. . in this case
The digital pixel signal output from the AD converter 105 is directly supplied to the gate 302, and the AD converter 1
The AD conversion output of AD converter 105 may be sorted directly by color, but in this example, the AD conversion output of AD converter 105
A case is shown in which the AD conversion output is taken into the data memory 106 described in FIG. 2, the average value of a plurality of times is obtained, and the average value is sorted by gate 302 for each color.

Therefore, after loading the average value of the output of each photoelectric conversion cell into the data memory 106, the data memory 10
6 and the mask memory 301R at the same time, the average value of pixel signals obtained from the photoelectric conversion cells emitting red light is read out from the data memory 106 from the address corresponding to the photoelectric conversion cell emitting red light. At the same time, an H logic control signal is read from the mask memory 301R. Therefore, the gate 302 is controlled to be open and only the red pixel signal can be taken out.

In this way, the mask memories 301R, 301
By arbitrarily switching and using G and 301B, any color signal of red, green, or blue can be freely extracted. Note that 310 is a mask memory 301R,
A control signal 311 is an address signal for determining which one of 301G and 301B is selected. Also 3
12 and 313 are memory selection circuits.

FIG. 4 shows an example of the arrangement of photoelectric conversion cells of a color solid-state image sensor. As shown in FIG. 4, photoelectric conversion cells responsive to red R, green G, and blue B light are arranged, and each color signal is extracted in this arrangement order.

Each color signal taken out from the gate 302 is transferred to means 300 for detecting the total amount of light received for each color. The total amount of light received for each color detection means 300 includes, for example, an adder 303, a latch circuit 304, an integrator 305,
It can be configured by a comparator 306 and a reference value setter 307. For example, a red pixel signal output from the gate 302 is integrated by a loop composed of an adder 303, a latch circuit 304, and an integrator 305, and the integrated value is sent to a comparator 306.
, it is compared with a reference value and it is determined whether the integrated value is within a certain range with respect to the reference value.

With this configuration, for example, the total amount of light received by all the red photoelectric conversion cells of the solid-state image sensor, the total amount of light received by the green photoelectric conversion cells, and the total amount of light received by the blue photoelectric conversion cells can be calculated using an integrator. A comparator 306 determines whether the total amount of light received for each color is within a predetermined tolerance range, and if the determination result is significantly different from the tolerance range, the solid-state image sensor is determined to be defective. It is determined that By sequentially performing this determination operation while changing the amount of light from the light source 112, it is possible to test the overall linearity of the photoelectric conversion cells of each color.

In addition to the test method of comparing the total amount of light received for each color with a reference value, for example, as shown in FIG. It can also be configured such that the signal is supplied to the comparator 502 and compared with the digital pixel signal of each photoelectric conversion cell in the comparator 502 to determine whether each photoelectric conversion cell is good or bad. In this case, a counter 503 is provided on the output side of the comparator 502, and a comparator 504 compares the number of defective cells counted by the counter 503 with the number of allowable defective cells. It is also possible to configure the defect indicator 506 to be operated into a display state. Note that 505 is a data file that stores the number of permissible defective cells.

<Effects of the Invention> As explained above, according to the present invention, the opening and closing of the gate 302 is controlled by the control signals read out from the mask memories 301R, 301G, and 301B, and the color signals are sorted by this gate. The image sensor 101 can sort color signals even if it is scanned using a standard scanning method. Therefore, a commonly used drive circuit can be used as the drive circuit for driving the solid-state image sensor 101, and it can be manufactured at low cost.

In addition, even when testing a solid-state image sensor having a structure in which a color signal is obtained by a combination of photoelectric conversion cells that respond to color signals such as red and yellow, the mask memory 301
Sorting can be done simply by changing the address of the control signal stored in the memory. Therefore, even if the formation of the solid-state image sensor changes, the change is easy.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining the outline of the invention, FIG. 2 is a block diagram for explaining an example of a memory having a function of averaging and capturing pixel signals obtained from a solid-state image sensor, and FIG. The figure is a block diagram showing an embodiment of the main part of the present invention, FIG. 4 is a plan view for explaining an example of a color solid-state image sensor, and FIG. 5 is a diagram of a data processor that can be used in the present invention. FIG. 7 is a block diagram showing another example. 101: Color solid-state image sensor, 102: Drive circuit, 105: AD converter, 106: Data memory, 108: Data processor, 301: Mask memory, 302: Gate.

Claims (1)

[Scope of Claims] 1. An AD converter that AD converts pixel signals of each color obtained from the color solid-state image sensor, and B. Control to an address corresponding to the position of each color photoelectric conversion cell of the color solid-state image sensor. A mask memory that stores information, C. A data memory that stores digital pixel signals corresponding to the pixel signals of each photoelectric conversion cell output from the AD converter, and D. Opening/closing control based on control information read from the mask memory. a gate for selecting and extracting only digital pixel signals of each color from the digital pixel signals read out from the data memory; E comparing the extracted digital pixel signals with a reference value; A color imaging device tester comprising: a data processor for determining the quality of a color image sensor;