JP4329673B2 - White scratch inspection device for solid-state image sensor - Google Patents

Description

  The present invention relates to a white flaw inspection apparatus for a solid-state imaging device used for a camera or the like.

In video cameras, digital cameras, and the like, solid-state image sensors such as CCDs and CMOS image sensors are generally used as photoelectric conversion elements for converting an optical image obtained by an optical system into a video electric signal. .
The solid-state image sensor is an aggregate of a plurality of fine light receiving pixels (photoelectric conversion elements). Although it is desirable that all of these light receiving pixels can be manufactured without defects, in practice, some light receiving pixels may be defective due to dust problems in the manufacturing process.

Among the light receiving pixels that are defective, there are some that are recognized as white spots when viewed as video output. These are usually referred to as white scratches. The camera is provided with a function for correcting the white defect as a means for making the normal white defect inconspicuous, but there is a limit to the range that can be corrected.
Therefore, before putting the solid-state image sensor into the production line built into the camera, the solid-state image sensor is inspected and selected according to predetermined criteria such as the level and number of white scratches. Only what is considered is used.

As a method for inspecting this white scratch, use a waveform monitor or an oscilloscope to observe a video signal, or capture the signal output of a solid-state image sensor as data for one screen into an image memory, etc., and perform numerical statistical processing. Is generally performed (see, for example, Patent Document 1).
JP 2000-92397 A

  By the way, in these solid-state imaging devices, white scratches include a type of white scratch that blinks when displayed on a monitor, in addition to a normal white scratch. This has the problem that it is difficult to detect with the conventional measuring method because the signal level is arbitrarily changed with time.

  Also, there are cases where a solid-state image sensor white scratch inspection device is deployed at each production site, and when a camera incorporating a solid-state image sensor is maintained, a service site is deployed. It is necessary to prepare. Accordingly, there has been a problem that a solid image pickup device inspection apparatus for a solid-state image pickup device that has a simple configuration and is inexpensive and that can detect white flaws accurately and reliably is desired. .

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a white flaw inspection apparatus for a solid-state image sensor, which is a simple structure at a low cost and can reliably detect white flaws and blinking white flaws. And

  When inspecting a white flaw in the solid-state image pickup device from the level of a video signal obtained by imaging with a solid-state image pickup device, the inspection is performed even when the electric signal level of the white flaw varies in an unstable state. In a white scratch inspection apparatus for a solid-state imaging device capable of performing the above, a level setting unit that sets a reference level for determining the white scratch, a determination signal generating unit that converts the reference level into a DC voltage signal, the DC voltage signal, and the Compared with a video signal, if the video signal is larger than the DC voltage signal, the video signal is selected. If the video signal is smaller than the DC voltage signal, the DC voltage signal is selected and output. A comparison circuit unit to be output; a determination attenuation circuit unit configured to subtract and output the DC voltage signal obtained by converting the reference level from the video signal or the DC voltage signal output from the comparison circuit unit; Providing white defect inspection apparatus of a solid-state imaging device characterized in that it has.

  According to the present invention, the level setting unit for setting a reference level for determining the white defect, the determination signal generating unit for converting the reference level into a DC voltage signal, the DC voltage signal and the video signal are compared. When the video signal is larger than the DC voltage signal, the video signal is selected, and when the video signal is smaller than the DC voltage signal, the comparison circuit unit selects and outputs the DC voltage signal; A determination attenuation circuit unit that subtracts and outputs a DC voltage signal obtained by converting the reference level from the video signal or the DC voltage signal output from the comparison circuit unit. A white flaw inspection apparatus for a solid-state imaging device that can reliably detect flaws and blinking white flaws can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings by way of preferred examples.

FIG. 1 is a block diagram showing an embodiment of a white flaw inspection apparatus for a solid-state image sensor according to the present invention.
FIG. 2 is a block diagram illustrating an example of a MIX unit and a level 5 setting unit in the white scratch inspection apparatus for a solid-state image sensor according to the present invention.
FIG. 3 is a graph showing signal waveforms in the example of the white flaw inspection apparatus for a solid-state imaging device of the present invention.

As shown in FIG. 1, the solid-state imaging device 11 to be subjected to white scratch inspection is incorporated in a camera 10, and the camera 10 is provided with a lens unit 18. An optical image is formed on the solid-state image sensor 11.
At the time of white flaw inspection, the lens unit 18 is covered with a cap, and the solid-state imaging device 11 is left in a non-light quantity state.

An electrical signal obtained by photoelectric conversion by the solid-state imaging device 11 (because there is no light, it becomes a black level 5 signal) is sent to a process circuit 12 built in the camera 10, where it is converted into a video signal 1, It is sent to the white flaw inspection device 20 of the solid-state image sensor.
The white flaw inspection device 20 for a solid-state imaging device includes a MIX unit (hereinafter also referred to as a signal synthesis unit) 13, a determination attenuation unit 14, a determination signal generation unit 15, and a level 5 setting unit 16.

The video signal 1 output from the process circuit 12 of the camera 10 is sent to the MIX unit 13.
The determination signal generator 15 generates a predetermined DC voltage signal 2 corresponding to the signal level specified by the level 5 setting unit 16 and sends it to the MIX unit 13.
The MIX unit 13 combines the video signal 1 from the process circuit 12 and the DC voltage signal 2 and sends a MIX signal (hereinafter also referred to as a combined signal) 3 to the determination attenuation unit 14. Here, the synthesis of signals is performed as follows. That is, when the video signal 1 is larger than the DC voltage signal 2, the video signal 1 is output as the MIX signal 3. Conversely, when the video signal 1 is smaller than the DC voltage signal 2, the DC voltage signal 2 is output as the MIX signal 3.

  On the other hand, the level signal 6 of the level setting unit 16 is sent to the determination attenuation unit 14 as the determination level signal 5. The value of the determination level signal 5 may be a value obtained by adding Δα to the level signal 6 of the level setting unit 16 in order to prevent a determination error. The determination level signal 5 and the DC voltage signal 2 correspond to each other and may be the same.

The determination attenuation unit 14 refers to the determination level signal 5 for the MIX signal 3 input from the MIX unit 13, and outputs the MIX signal 3 as it is as the determination video signal 4 when the MIX signal 3 is larger than the determination level signal 5. When the MIX signal 3 is equal to or lower than the determination level signal 5, the level signal 5 of the MIX signal 3 is lowered and output as the determination video signal 4. The level to be lowered is preferably a black level, but may be in a range that can be distinguished well from the level signal 5 of white scratches. Here, the DC component of the MIX signal 3 may be cut without using the determination level signal 5.
The determination video signal 4 output from the determination attenuation unit 14 is sent to the monitor 17 and displayed on the screen.

  On the screen, among the video signals 1 obtained from the solid-state imaging device 11, the video signal 1 having a level equal to or higher than the predetermined level signal corresponding to the DC voltage signal 2 is displayed as white scratches, which can be detected visually. Even if the white scratches are blinking type, they can be reliably detected as white scratches if the screen is displayed for a predetermined time.

Next, an example of the MIX unit 13 and the determination signal generation unit 15 will be described with reference to FIG.
As shown in the figure, the MIX unit 13 includes two transistors 25 and 26. The transistors 25 and 26 are emitter followers, and a predetermined operating voltage Vd is applied to each collector from a terminal 22. The base of the transistor 25 is supplied with a video signal 1 obtained by the solid-state imaging device 11 from a terminal 21 connected to the output of the process circuit 12.

  The determination signal generation unit 15 includes two variable resistors 28 and 29 connected in series via a connection point 27. One end of the variable resistor 29 that is not on the connection point 27 side is grounded, and one end of the variable resistor 28 that is not on the connection point 27 side is connected to the terminal 22, and a predetermined operating voltage Vd is applied. By adjusting the variable resistors 28 and 29, respectively, the DC voltage signal 2 corresponding to the level given by the level setting unit 16 (not shown) below the operating voltage Vd can be given to the connection point 27.

On the other hand, the DC voltage signal 2 is applied to the base of the transistor 26.
Accordingly, the larger of the video signal 1 input to the transistor 25 and the DC voltage signal 2 input to the transistor 26 is output from the emitter to the terminal 23 as the MIX signal 3.

Next, each waveform of the above-described signal will be described with reference to FIG. For convenience of explanation, in each of FIGS. 3A, 3B, 3C, and 3D, a signal waveform of one line is displayed.
FIG. 3A shows the video signal 1 obtained from the solid-state imaging device 11 containing white scratches. D indicates a black level signal. Vs indicates the DC voltage signal 2 corresponding to the level signal 6 determined to be white scratches. Waveform A, Waveform B, and Waveform C are all larger than the black level of 5. However, Waveform A and Waveform C should be detected as white scratches. The waveform b does not have to be regarded as white scratches.

  FIG. 3B shows the output of the determination signal generator 15 and shows the DC voltage signal 2 (this is the voltage Vs), and the level of the DC voltage determines whether the white flaw of the solid-state image sensor 11 is good or bad. This signal is a reference signal for this purpose, and can be changed corresponding to the level signal 6 of the level setting unit 16.

  In FIG. 3C, the video signal 1 input to the MIX unit 13 and the DC voltage signal 2 are compared, and a larger signal (a higher level signal) is output. Among the video signals, waveform A and waveform C are larger than Vs, so they are output as MIX signal 3, and DC voltage signal 2 (Vs) is output at other positions corresponding to black level D and waveform B.

  FIG. 3D shows the determination video signal 4 that is processed and output by the determination attenuation unit 14 from the MIX signal 3 output from the MIX unit 13 to the determination attenuation unit 14. The determination attenuation unit 14 cuts the DC component (may be attenuated to a predetermined level 5) and outputs it, that is, a signal larger than Vs with Vs set to the ground level is output as a signal level obtained by subtracting Vs. The

When this video signal for determination is displayed on the monitor 17, the waveform A and the waveform C are clearly displayed as white dots on the uniform substantially black screen as compared with the surroundings. These can be recognized and identified as white scratches. Here, for example, even if the waveform A is a blinking type white defect, it is displayed blinking so that it can be easily detected and identified. Also, when the white defect is within the standard, the standard is determined by the level of the DC voltage signal 2 The video signal 1 is masked to the voltage level of the DC voltage signal 2. The output of the determination attenuation unit 14 is all attenuated because the video signal 1 is below the level of the DC voltage signal 2, and can be recognized as a uniform substantially black screen when displayed on the monitor 17.

  As described above, according to the white flaw inspection device for a solid-state image sensor of the present invention, it is possible to reliably inspect and select white flaws of the solid-state image sensor with an inexpensive and simple configuration. Furthermore, even if the signal level fluctuates, such as blinking white scratches in a solid-state image sensor, the blinking display is visually obvious, and this is also easy and sure to inspect and select as white scratches in the solid-state image sensor. Can do.

It is a block diagram which shows the Example of the white flaw inspection apparatus of the solid-state image sensor of this invention. It is a block diagram which shows an example of the MIX part and level 5 setting part in the white flaw inspection apparatus of the solid-state image sensor of this invention. It is a graph which shows the waveform of the signal in the Example of the white flaw inspection apparatus of the solid-state image sensor of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Video signal, 2 ... DC voltage signal, 3 ... MIX signal (synthesis signal), 4 ... Video signal for determination, 5 ... Level signal for determination, 6 ... Level signal, 10 ... Camera, 11 ... Solid-state image sensor, 12 DESCRIPTION OF SYMBOLS ... Process circuit, 13 ... MIX part (comparison circuit part), 14 ... Determination attenuation part, 15 ... Determination signal generation part, 16 ... Level setting part, 17 ... Monitor, 18 ... Lens unit, 20 ... White defect inspection apparatus, 21 Terminals 22 Terminals 23 Terminals 25 Transistors 26 Transistors 27 Connection points 28 Variable resistors 29 Variable resistors

Claims (1)

Solid-state imaging that can be inspected even when the electrical signal level of the white scratch fluctuates in an unstable state when inspecting the white scratch in the solid-state image sensor from the level of the video signal obtained by imaging with the solid-state image sensor In the device white scratch inspection device,
A level setting unit for setting a reference level for determining white scratches;
A determination signal generator for converting the reference level into a DC voltage signal;
The DC voltage signal is compared with the video signal. When the video signal is larger than the DC voltage signal, the video signal is selected. When the video signal is smaller than the DC voltage signal, the DC voltage is selected. A comparison circuit section for selecting and outputting a signal;
A determination attenuation circuit unit that subtracts and outputs the DC voltage signal obtained by converting the reference level from the video signal or the DC voltage signal output from the comparison circuit unit;
A white flaw inspection apparatus for a solid-state imaging device, comprising:

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