JPH02303276A - High frequency distortion correction device for ccd linear image sensor device - Google Patents

Abstract

PURPOSE:To attain proper correction without needing read of a white level original in advance by providing a comparison discrimination means which splits a picture data output into a data for each picture element, compares it with a preceding and succeeding picture element data and gives an output when an absolute value of a difference between the picture element data is a prescribed value or below. CONSTITUTION:A picture element data from a CCD linear image sensor 51 is corrected by a high frequency distortion correction LSI 52, a comparison discrimination means A splits data of each picture element, compares it with preceding and succeeding picture element data and gives an output when the absolute value of a difference between picture element data is a prescribed value or below and stores the picture data output discriminated by the comparison discrimination means A to a picture signal recording memory 61. Thus, the read of a white level original is not needed in advance and transient noise is immune and high frequency distortion caused due to fluctuation of each picture element output of a picture data is dynamically corrected.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a clock switching circuit for a high frequency distortion correction device that corrects pixel variations in the output of a CCD linear image sensor device.

[Conventional technology]

Figure 2 shows, for example, ■ Published by Hitachi, September 1986 (7) r HO2:1084 DIPP x-f
FIG. 2 is a block diagram of a circuit configuration for high frequency distortion correction of the CCD linear image sensor device shown in X-Mars Full J. In this FIG. 2, 1 is a CCD linear image sensor, 2 is an image signal processing LSI with a high frequency distortion correction function that processes the data output photoelectrically converted by this CCD linear image sensor 1, and 3 is a high frequency distortion correction A high frequency distortion correction memory stores data, and 4 is a memory buffer of this high frequency distortion correction memory. 5 is a data latch buffer for the image data processed by the image signal processing LSI 2; 6 is a multiplexer for bit-converting the image data that has passed through the data latch buffer 5; and 7 is for storing the image data bit-converted by the multiplexer 6. This is a memory for recording image signals. Further, FIG. 3 is an explanatory diagram showing a state of reading high frequency distortion data when using the high frequency distortion correction function in the image signal processing LSI 2. In this Figure 3, 21
is a light source, 22 is a white reflecting plate that reflects the light from this light source 21, and 23 is a condensing lens that focuses the light reflected by this white reflecting plate 22. 24 corresponds to the CCD linear image sensor 1, and receives light from the condensing lens 23 and converts it photoelectrically. 25 corresponds to the image signal processing LSI 2, and corresponds to the CCD linear image sensor. This is an image signal processing LSI that processes 24 data outputs. Further, FIG. 4 is an explanatory diagram showing a correction data reading operation when using the high frequency distortion correction function in the image signal processing LSI 25. In this Figure 4, 31 is the read data of the white line, and 32 is the 4-bit A/
D converter, 33 is a 4-bit D/A converter, 34 is a shading waveform, 35 is its high frequency distortion, 3
6 is data obtained by converting the high frequency distortion 35 into 4-bit digital data. Furthermore, FIG. 5 is an explanatory diagram showing the internal operation within the image signal processing LSI 25 when actually performing high frequency distortion correction. In this FIG. 5, 41 is the 4 bit A
4-bit A/D converter corresponding to the /D converter 32, 42 is human image data, 43 is a shading waveform, 44 is high frequency distortion data transferred from an external high frequency distortion correction memory, 45 is high frequency distortion data 44 This is the high frequency distortion generated by Next, the operation will be explained. The output data from the CCD linear image sensor l is A/D converted in the image signal processing LS [2, and if the high frequency distortion correction function is enabled, it is sent from the high frequency distortion correction memory 3 to the memory buffer 4. It is corrected based on the input high frequency distortion correction data and output to the data latch buffer 5. The data at this time is 4 pixels worth of output data from the CCD linear image sensor 1.
The data is converted into bits and transferred in a configuration of 8 bits for 2 pixels. Further, the image data passing through the data latch buffer 5 is converted into 4-bit data for each pixel by a multiplexer 6, and then stored in the image signal recording memory 7. In order to activate the high frequency distortion correction function in the image signal processing LSI 2, first, as shown in FIG. 3, one line of white data is read and the high frequency distortion data is extracted. need to be detected. That is, the light from the light source 21 is reflected by the white reflecting plate 22, condensed by the condensing lens 23, and then photoelectrically converted by the CCD linear image sensor 24 and sent to the image signal processing LSI.
Sent to 25th. Then, inside the image signal processing LSf25, the fourth
As shown in the figure, the white line reading data 3! is sent to a 4-bit A/D converter 32, where it is compared with a shading waveform 34 obtained by a 4-bit D/A converter 33, its high frequency distortion 35 is detected, and 4-bit digitized high frequency distortion data 3 is generated.
6 is obtained, and this high frequency distortion data 36 is
The data is stored in the high frequency distortion correction memory 3 shown in the figure. Therefore, when reading a document, which is a normal object to be read, inside the image signal processing LSI 25, as shown in FIG. Image data 42 and shading waveform 43. In addition, each of the high-frequency distortion correction waveforms 45 generated from the high-frequency distortion data 44 transferred from the external high-frequency distortion correction memory 3 is manually input at the same time.
High frequency distortion of the input image data 42 is corrected, and after this correction, it is output as 4-bit digital data.

[Problems to be Solved by the Invention] Since the conventional high-frequency distortion correction device for a CCD linear image sensor device is configured as described above, it is necessary to hold high-frequency distortion correction data in the memory, and Before reading the original, it is necessary to read a white original several times, which makes the operation unnecessarily complicated, and if temporary noise is not completely removed, it will be difficult to correct it. On the other hand, there are problems such as people getting used to the occurrence of high-frequency distortion, and although it is thought that the signal output level and the high-frequency distortion level are proportional, the actual CC
Pixel variation in output in D linear image sensor device,
That is, the so-called PRNU does not necessarily have a linear relationship with the signal output level, and there is a problem in that the correction may be appropriate or inappropriate depending on the signal output level. This invention was made to solve the above-mentioned problems, and it eliminates the need to read the white MM4 in advance, is not affected by transient noise, and reduces pixel variations in the output of a CCD linear image sensor. An object of the present invention is to obtain a high frequency distortion correction device for a CCD linear image sensor device that can appropriately correct PRNU. [Means for Solving the Problems] A high-frequency distortion correction device for a CCD linear image sensor device according to the present invention corrects pixel data from a CCD linear image sensor using a high-frequency distortion correction LSI, and uses a comparison and judgment means to correct each pixel. At the same time, it is divided into data, compared with the previous and subsequent pixel data, and output when the absolute value of the difference between each pixel data is less than a predetermined value, and the image data output determined by the comparison determination means is recorded as an image signal. It is designed to be stored in memory for use.

[Effect]

The high-frequency distortion correction device of the CCD linear image sensor device according to the present invention divides the image data output processed by the high-frequency distortion correction LSI into data for each pixel, and compares this with the previous and subsequent pixel data to determine the difference between each pixel data. By providing a comparison judgment means that outputs when the absolute value of the difference is less than a predetermined value, each pixel in the image data Dynamically corrects high frequency distortion caused by output variations.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a high frequency distortion correction device for a CCD linear image sensor device to which this embodiment is applied. In the figure, 51 is a CCD linear image sensor, 52
is an image signal processing LSI having a high frequency distortion correction function that processes image data output photoelectrically converted by this CCD linear image sensor 51. 53 is the image signal processing L
A data latch buffer for the 8-bit image data for 2 pixels processed by the SI 52; 54 is a multiplexer that divides the 8-bit data for 2 pixels that has passed through the data latch buffer 53 into 4-bit data for each pixel;
5 is a data latch buffer that delays the output data of the multiplexer 54 by one pixel, 56 is a data latch buffer 1% that similarly delays the output data by two pixels, 57 is a data latch buffer that similarly delays the output data by three pixels, and 58 is a one pixel delay. a comparator that compares the data and the 3-pixel delay data and makes the output Y logic "1" when they are equal;
9 is gate power G is “l” and 2 pixel delay data and 3
A comparator makes the output Y logic "1" only when the absolute value of the difference in pixel delay data is 4 or less, and 60 is a selector that selects and outputs one of the two 4-bit data according to the logic of the input S. These constitute the comparison and determination means A. Reference numeral 61 denotes a comparison/judgment means image signal recording memory for recording the determined image data output. Next, the operation will be explained. First, analog data output from the CCD linear image sensor 51 is sampled and held by the image processing LSI 52, and then subjected to A/D conversion. Each two pixels is output as 8-bit data. Also, the 8-bit data is transferred to the 8-bit data latch buffer 5.
3 and sent to the multiplexer 54, where it is divided into 4-bit data for each pixel. Next, this 4-bit data is transferred to data latch buffers 55 and 56 by a clock synchronized with the transfer rate of one pixel.
．． 57, and are transferred sequentially as 1-pixel delayed data, 2-pixel delayed data, and 3-pixel delayed data, respectively. In addition, the comparator 58 constantly compares the 1 pixel delay data and the 3 pixel delay data, and when the two are equal,
Output Y is set to logic "L". In the comparator 59, 2
Constantly compare pixel delay data and 3 pixel delay data,
When the gate power G is logic "1", that is, when the 1-pixel delay data and the 3-pixel delay data are equal, the absolute value of the difference between the 2-pixel delay data and the 3-pixel delay data is 4 or less, so to speak, the output is Y. is set to logic “1”. In the selector 60,
9 out of 1 pixel delay data and 2 pixel delay data, usually 2
Transfer the pixel delay data to the image signal recording memory 61,
Only when the output Y of the comparator 59 is logic "1",
Transfer 1 pixel delay data. Here, the pixel variation PRUN of a CCD linear image sensor device is determined by Jot
-20, and is relatively unnoticeable when the image output level is varied, and is noticeable when the image output level is flat. Therefore, as mentioned above, by constantly comparing the 1-pixel delayed data and the 3-pixel delayed data, it is possible to check whether the image output level has changed, and if it has not changed, the 2-pixel delayed data and the 2-pixel delayed data can be checked. The absolute value of the difference is 4 or less. In other words, since each pixel at this time is 4-bit data, 4÷24X100.25 is calculated as follows:
The 2-pixel delay data is regarded as high-frequency distortion data and is not recorded in the image signal recording memory, but instead the 1-pixel delay data is recorded to maintain the flatness of the image output level. And when the change in the 2-pixel delay data exceeds 25X, by recording it as is in N, the result is C.
This eliminates the fear that the resolution of the CD linear image sensor will be significantly degraded. In the above embodiment, the amount of change in the two-pixel delay data was set to 2596 or less, but this value may be changed in accordance with the characteristics of the CCD linear image sensor. In addition, in this S, it is judged whether the image is flat or not based on data for two pixels, 1-pixel delayed data and 3-pixel delayed data, but if the sample data is increased, the judgment will become more stable. can be done.

【Effect of the invention】

As described above, according to the present invention, the high frequency distortion correction LSI
The image data output from the CCD linear image sensor processed by is divided into data for each pixel, and this is compared with the previous and subsequent pixel data, and when the absolute value of the difference between each pixel data is less than a predetermined value, Provide a comparison judgment means to output,
Since high-frequency distortion correction is performed dynamically using a CCD linear image sensor, there is no need to read a white original in advance and there is no need to hold high-frequency distortion correction data, making the device extremely easy to operate. , there is no risk of inappropriate correction due to temporary noise, and there is an effect that stable correction can be made regardless of the output image level.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a high frequency distortion correction device for a CCD linear image sensor device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a high frequency distortion correction device for a conventional CCD linear image sensor device. , FIG. 3 is an explanatory diagram showing the state of reading high frequency distortion data in the prior art, FIG. 4 is an explanatory diagram showing the operation of reading correction data when using the high frequency distortion correction function in the prior art, and FIG. FIG. 6 is an explanatory diagram showing an operation when performing high frequency distortion correction on read data according to the prior art. 51 is a CCD linear image sensor, 52 is an image signal processing LSI having a high frequency distortion correction function, 61 is a memory for recording image signals, and A is a comparison/judgment means. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Figure 3 Figure 4

Claims (1)

[Claims] A CCD linear image sensor, a high frequency distortion correction LSI that corrects high frequency distortion caused by variations in the output of each pixel in image data read by the CCD linear image sensor, and the high frequency distortion correction LSI. Comparing and determining means that divides the processed image data output into data for each pixel, compares this with previous and subsequent pixel data, and outputs it when the absolute value of the difference between each pixel data is equal to or less than a predetermined value; A high frequency distortion correction device for a CCD linear image sensor device, comprising an image signal recording memory for storing image data output determined by the comparison and determination means.