JPH03216566A - Tester of ccd linear image sensor - Google Patents

Abstract

PURPOSE:To detect spike-like sensitivity irregularity in a pixel unit by comparing the digital value of a pixel unit obtained by applying uniform light to a CCD linear image sensor with previous data. CONSTITUTION:The output pixel data obtained when uniform light is applied to a CCD linear image sensor 1 is converted to digital data by an A/D converter 3 through a pre-processor 2 and latched by latch buffers 4, 6 at every pixel. A comparator 8 compares the output OA of the buffer 4 with the output OB of the buffer 6 in which the pixel data, one before the address of the buffer 4 is stored while shifted successively. When the difference between both outputs exceeds the threshold value set by a switch group 9, an abnormal signal is outputted to stop a pulse generator 11. By this constitution, the buffers 4, 6 and a counter 12 are stopped and the abnormal pixel data or pixel address at that time is displayed on display devices 5, 7, 13.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a COD linear image sensor/sensor testing device that tests variations in output values of a COD (charge coupled device) linear image sensor on a pixel-by-pixel basis. .

[Conventional technology]

FIG. 4 is a diagram showing the electrical and optical characteristics of, for example, a COD linear image sensor currently in practical use.
1 is the value of sensitivity non-uniformity characteristic (hereinafter abbreviated as PRNU), 2
2 is a note defining the PRNU.

Next, an outline of the PRNU 21K will be explained.

As described in Note 22, the absolute value 1Δx1 of the difference between the 5K average output amplitude value and the amplitude value of the maximum (or minimum) output pixel is specified as a maximum of 10 cm, so uniform light is applied to the photosensitive surface. When this occurs, an output variation of ±5 degrees will occur with respect to the average output amplitude value Xk.

In the case of an actual device, when uniform light is applied to the photosensitive surface, this phenomenon of variation may appear as a gentle curve as shown in Figure 2, or as a frequency change as shown in Figure 3. It may also appear as a high spike-like waveform.

[Problem to be solved by the invention]

Sensitivity non-uniformity of conventional COD linear image sensor (
P RNU ) has the above characteristics, so
If the COD linear image sensor is used for binary reading, such as in facsimiles, slight variations in actual output values will not pose a problem in terms of functionality, but COD linear image sensors such as high-gradation image scanners may When using a linear image sensor, etc., there is a problem in that when spike-like variations occur, a clear step in gradation appears on the output screen, albeit with a low amplitude, and the image quality deteriorates significantly.

Further, even if this variation is discovered after the sensor is installed in a device and an attempt is made to replace the sensor, there are problems such as optical and mechanical restrictions making it difficult to replace the sensor.

This invention was made to solve the above-mentioned problem, and before the CCD linear image sensor was incorporated into equipment, it was discovered that the 7000D linear image sensor had a characteristic of spike-like sensitivity variation. It is an object of the present invention to obtain a test device for a CCDIJ near image sensor that can automatically determine whether or not there is a CCDIJ near image sensor.

[Means to solve the problem]

The COD linear image sensor test device according to the present invention digitally converts image output data when uniform light is applied to the COD linear image sensor and converts it into a pixel-by-pixel IC.
J first and second data storage means for primary storage, a comparator for comparing the data of the first data storage means and previous data stored in the second data storage means, and an output from the comparator. The sensor is constructed with a display device, etc. that outputs abnormal pixel information based on the abnormal signal generated, and is designed to test for spike-like sensitivity variations on a pixel-by-pixel basis.

[For production]

The first and second data storage means in this invention sequentially store pixel data output in pixel units when uniform light is applied to the COD linear image sensor, and the stored data is used in subsequent stages. It is applied to a comparator and the difference is taken out.

If the difference exceeds a predetermined value, abnormal pixel information is output to the display, so that the electrical and optical characteristics of the sensor are automatically checked for each K pixel before installation.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is a COD linear image sensor, 2 is a C
a preprocessor that performs waveform processing such as sample/hold and amplification on the image output signal of the CD linear image sensor 1;
3 is an A-D converter; 4 and 6 are 2 latch buffers as first and second data storage means for latching the output image data of the COD linear image sensor 1 pixel by pixel; and 5 and 7 are respective latch buffers. 7-segment display that displays the output values of latches 4 and 6, 8 a comparator that compares the output values of each latch 4 and 6, 9 that sets judgment conditions such as threshold values for comparator 8, and 10 is a driver that drives the drive clock of the COD linear image sensor 1; 11 is a pulse generator that generates drive clock pulses of the COD linear image sensor 1; 12 is a counter that counts the pulses of the pulse generator 11; 13 is a 7-segment display that displays the output value of the counter 12.

Next, the operation will be explained. First, pixel data output from the CCD linear image sensor 1 is sampled and held in a preprocessor 2 to remove reset noise and clock components, and then amplified by K. The signals are then digitally converted by the AD converter 3 and latched into latch buffers 4 and 6 for each pixel. The comparator 8 always operates the latch buffer 7a 6, which is stored in such a manner that the output value oA of the latch buffer 4 and the pixel data immediately before the address of the pixel data stored in the latch buffer 4 are sequentially shifted. The pulse generator 11 is compared with the output value OB, and when the difference exceeds a threshold set by the switch group 9K, an abnormality signal is output and the pulse generator 11 is stopped.

When the pulse generator 11 stops, the latch backs 7a 4 and 6 and the capacitor 12 also stop, and data and pixel addresses as abnormal pixel information determined to be abnormal at that time are displayed on the 7-segment displays 5, 7, and 13.

In the above embodiment, a circuit configuration was described in which the abnormal data and the pixel address at that time are temporarily stored in the latch buffer 4 or 6 and the counter 12. All the sensitivity variations may be stored and displayed.

〔Effect of the invention〕

As described above, according to the present invention, the first data storage means stores the image output data of the CCD linear image sensor, and the second data storage means stores the pixel data before the stored pixel data. A test device for a CCD linear image sensor was configured with a comparator that compares the two pixel data and outputs an abnormal signal when the difference exceeds a predetermined value, and a display that displays the abnormal signal as abnormal pixel information. , it is possible to test for spike-like sensitivity variations before incorporating the sensor into equipment K, which has the effect of improving product inspection reliability and yield.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a test device for a CCD linear image sensor according to an embodiment of the present invention, FIGS. 2 and 3 are waveform diagrams showing an example of PRNU characteristics of a CCD linear image sensor, and FIG. Figure (Al, (Bl) is an explanatory diagram of the electrical and optical characteristics of the CCDIJ near image sensor currently being commercialized. In the figure, 1 is a COD linear image sensor, 4.6
are latch back 7a (first and second data storage means), 5
, 7.13 is a display, and 8 is a comparator. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A first data storage means that digitally converts image output data when uniform light is applied to a CCD linear image sensor and stores it in pixel units; A second data storage means for storing pixel data is compared with the pixel data stored in the first data storage means and the second data storage means, and if the difference exceeds a predetermined value, an abnormal signal is output. A test device for a CCD linear image sensor, comprising a comparator and a display that displays abnormality information when receiving an abnormality signal from the comparator.