JPS62200872A - Correcting device for output signal of image pickup element - Google Patents

Abstract

PURPOSE:To linearly associate the level of an output signal from an image pickup element with the light intensity of the color of an inputted image by connecting an output signal correcting device consisting of a ROM, a RAM being a correction data storage means and an Xn multiplier being an arithmetic means to the later stage of a shading correcting device. CONSTITUTION:When a CCD 1 reads an original in half tone, correction data used for setting the levels of the output signals of each image pickup element to the prescribed value is stored at every address in the ROM 8 of the correcting device 200. In order to set the levels of said signals, the arithmetic, XnXXn (0<Xn), is executed. Consequently, Xn that is <=1 or >=1 according as the level of the output of the shading correcting device 100 is larger or smaller than the prescribed value, and Xn that is '1' if the level of the output of the device 100 is the prescribed value, are stored as correction data in the ROM 8. A control circuit 2 gives address data corresponding to the element of the position of the read-out CCD 1 to the RAM 9. Thus a piece of data Xn required for XnXXn, which is executed for correcting the deviation of said element, is given to the RAM 9 by outputting from the ROM 8. As a result the correcting device 200 corrects the output data of the device 100, whereby data distortion due to the deviation of elements of CCD 1 in terms of linearily can be removed.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a CC used in a facsimile machine, etc.
The present invention relates to an image sensor output signal correction device used for correcting an output signal of an image sensor such as D.

Technical Background of the Invention] A shading correction device is conventionally known as a device for correcting an output signal of an image sensor.

In this device, when a fluorescent lamp is used as a light source when reading a document image etc. to the II image element, the light intensity of the fluorescent lamp differs in the length direction, so the level of the output signal of the image sensor is lower than that of the above-mentioned light. This is to correct for the fact that it differs in the main scanning direction depending on the intensity. Typically, such devices input a white original and detect the level of the signal obtained from the image sensor at this time.
Correction is applied to the output signal of the image sensor so that the level of the signal is the same at each position in the main scanning direction.

[Problems in the Background Art] According to such a shading correction device, the output signal of the image carrier is not deviated from the maximum exposure when a document of a predetermined color (usually white) is read. It can be used as a signal. However, when considering the elements at each position in the main scanning direction of the image sensor, it is not ensured that the elements read from white to black with linearity only by the above-mentioned shading correction. In other words, if there is a deviation in the linearity of the elements at each position in the main scanning direction, the output signal of the element having the deviation will be distorted. Halftone patterns read by W&image elements that include such elements may cause streaks in the parts of the elements that have deviations when they are binarized, and may also cause problems in photographs, etc. When creating a halftone image, there were drawbacks such as uneven density.

For this reason, it has not been possible to meet the requirements for high image quality.

[Object of the Invention] The present invention was made in view of the drawbacks of the above-mentioned conventional device for correcting the output signal of an image sensor, and its purpose is to correct the output signal corresponding to each position in the main scanning direction of the image sensor. An object of the present invention is to provide an image sensor output correction device that can accurately perform correction when the level does not linearly correspond to the light intensity of the color of an input image.

[Summary of the Invention] Accordingly, in the present invention, the present device is connected to a downstream stage of a shading correction device that performs shading correction on an output signal of an image sensor, and when the R element reads an image having a predetermined light intensity, correction data storage means for storing correction data corresponding to each position in the main scanning direction for making the level of the output signal output from the shading correction device the same level in the main scanning direction of the S element; , based on the output signal output from the shading correction device and the correction data in the correction data storage means corresponding to the position in the main scanning direction of the image sensor from which the original signal of the output signal is obtained, The above object is achieved by configuring an image sensor output correction device including a calculation means for calculating linearity correction for an output signal at each position in the scanning direction.

[Embodiments of the Invention] In FIG. 1, 1 indicates COD. The CCD 1 outputs analog signals read by elements at each position in the main scanning direction to the A/D converter 3 in synchronization with successive clocks supplied from the control circuit 2 . The A/D converter 3 converts the analog signal output from the CCDI and read by the elements at each position in the main scanning direction into digital data, and provides the converted digital data to the ROM 4 and the multiplier 5. The control circuit 2 provides a conversion timing signal to the A/D converter 3.

The output data of the A/D converter 3 is applied to the address terminal of the ROM 4. The ROM 4 stores correction data necessary for shading correction in correspondence with addresses. For example, when the CGDI reads a reference document such as white or an image of a conveyance path such as white, the level vL of the output signal changes as shown in Figure 2 in response to the main scanning direction. If so, all levels vL are correction levels■
A coefficient a obtained from the equation of V, Xa=■La is stored in the ROM 4 so that La. And A/D
Since the output data V of the converter 3 becomes the address data, data with a large coefficient a is stored corresponding to a small address, and data with a small coefficient a is stored corresponding to a large address. The output data (coefficient a) of ROM4 is R
Applied to the data terminal of AM6. The control circuit 2 is RA
An R/W signal and address data for switching between write mode and read mode are applied to M6. in particular,
When storing the data that forms the basis of shading correction in the RAM 6, that is, when inputting the aforementioned reference original, etc., the RAM 6 is set to write mode by the R/W signal, and the CC
Address data corresponding to the element at a predetermined position in the main scanning direction of the CCD 1 corresponding to successive clocks applied to D1 is output.

Next, the data that forms the basis of shading correction is stored in RAM.
6 will be explained. At this time, the aforementioned reference document and the like are input.

At this time, the control circuit 2 sets the R/W signal to write mode. When a reference document is input, a signal having a level at the left end in FIG. 2 is output from the CCD 1, which is digitized and output from the A/D converter 3. At this time, the control circuit 2 provides address data (for example, O) corresponding to the leftmost element of the CCD 1 in the main scanning direction to the RAM 6. Then, the data of the coefficient a corresponding to the leftmost level is output from the ROM 4, and this data is written to the address of the RAM 6. Next, when the control circuit 2 gives successive clocks to the CCD 1, the CCD 1 outputs a signal having a level corresponding to the element of the CCD 1 located next to the left end in FIG. converter 3
is output from.

At this time, the control circuit 2 provides the RAM 6 with address data (for example, 1) corresponding to the next element at the left end of the CCD 1 in the main scanning direction. Then, the data of the coefficient a corresponding to the level obtained from the element of the CCD 1 located next to the left end is output from the ROM 4, and this data is written to the address of the RAM 6. Below, the same operation is performed in the second
This continues until the data of the coefficient a corresponding to the element located at the right end position in the figure is written to the corresponding address in the RAM 6.

In this way, when the data is stored in the RAM 6, shading correction during normal document reading becomes possible. When a normal original is input, the control circuit 2 supplies the R/W signal to the RAM 6 in continuous mode. When a normal document is input, the control circuit 2 supplies a read clock to the CGDI to sequentially read the document in the main scanning direction. Then, the digitally converted signal is given to the multiplier 5. On the other hand, the control circuit 2 outputs address data corresponding to an element at a predetermined position of the CCD 1 corresponding to the read clock to the RAM 6. As a result, the coefficient a for shading correction of the element of the CCD 1 from which the data given to the multiplier 5 was obtained is outputted from the RAM 6 and given to the multiplier 5. The multiplier 5 multiplies the output data vb of the A/D converter 3 by the coefficient a to obtain 8. Here, if the original is white, Vb-V, and 7.a = LA. The multiplication result data 8 obtained in this way is sent to the divider 7, where it is divided by appropriate fixed data and becomes data Bn. The meaning of this division is that it is usually difficult to obtain the desired level (a level that is easy to process in the subsequent stage) by only multiplication, and when the desired level can be obtained only by multiplier 5, divider 7 is not necessary. that's all,
Control circuit 2 and ROM 4 for shading correction
, a multiplier 5, a RAM 6, and a divider 7 constitute a shading correction device 1''oO.

At the subsequent stage of the shading correction device fi100, there is a control circuit 2, a ROM 8, and an RA which is a correction data storage means.
M9, X which is a calculation means. An image sensor output signal correction device 200 consisting of a multiplier 10 is connected. The output of the shading correction device 21ioo is transmitted to the ROM 8 and the X1 multiplier 1.
given to 0. The control circuit 2 stores the data serving as the basis for shading correction in the RAM 6 and the data for correcting the linearity of each element of the CCD 1, which will be described next, in the RAM 9.
Since the R/W signal is given to M9 as the write mode, Xo
No data is given to the multiplier 10 from the RAM 9, and no calculation of the power of X0 is performed.

The ROM 8 stores correction data for each address for aligning the level of the signal output from each element of the CCD 1 to a predetermined value when the CCD 1 reads an original with a light intensity of a predetermined halftone. . Specifically, each element of the CCD 1 preferably performs level conversion in exactly the same way for light intensities of all colors from white to black, but there are deviations for each element. Therefore, in this embodiment, an original with a predetermined halftone is input, and if the levels of the signals output from each element of the CCD 1 are uneven, the deviations for each element are corrected by aligning them to a predetermined value. . In order to match this predetermined value, in this embodiment, an operation is performed to the power of X (0<X.), and for this purpose, X is necessary for each element. seek. The ROM 8 stores a value X that corresponds to the output level (digital value) of the shading correction device aioo and is smaller than 1 if the value is larger than a predetermined value. However, if the value is smaller than a predetermined value, xo, which is a value greater than 1, is stored corresponding to the ripple, and if the value is the predetermined value, xo, which is 1, is stored. The control circuit 2 provides the RAM 9 with address data corresponding to elements at predetermined positions of the CCD 1 corresponding to successive clocks applied to the CGDI.

Therefore, data for shading correction is stored in RAM.
When the half-tone original stored in the CCD 6 is input, the shading correction device 100 outputs data corresponding to the shading-corrected original to each element of the CCD 1.

The control circuit 2 has a shading correction device 10 in the RAM 9.
Since the address data corresponding to the element of CCD 1 which is the source of the output data of 0 is given, the RAM 9 contains data X necessary for calculating the power of Xn to correct the deviation of the element.
. is outputted from the ROM 8, given, and written.

The operation of the main parts of a facsimile machine in which the image element output signal correction device jfi 200 is connected to the downstream of the shading correction device 100 will be described with reference to a case where a normal original is input. It is assumed that necessary data has already been written to the RAM 6.9.

Now, the density of one predetermined line of the input document is shown in Figure 3 (
Assume that the change is as shown in a).
When a line is read by the CCD 1, as a result of shading by the fluorescent lamp, an output signal with a low level at both ends of the CCD 1 in the main scanning direction is obtained (see Fig. 3).
b)). When such an output signal passes through the shading correction device 100, the coefficient a is multiplied by each element of the CCD 1, the levels at both ends of the CCDI in the main scanning direction are increased, and the shading is corrected (see Fig. 3 (C). )).

However, the output data after this shading correction is
Vertical fluctuations in level caused by deviations in linearity for each element of the CCD 1 can be seen except in the white portion. Vertical fluctuations in the level of the white portion have already been removed during shading correction. @In the image element output signal correction device 200, the control circuit 2 outputs the R/W signal to the RAM 9 in continuous mode, and continuously outputs the address data corresponding to the CCDI element that is the source of the output data of the shading correction device 100. It is applied to the RAM 9 in correspondence with the clock.

Therefore, the output data Bn of the shading correction device 100 and the output data Xn of the RAM are provided to the Xo multiplier 10, and the XO multiplier 10 performs the calculation of (Bn/A)Xn. Here, A is data output from the shading correction apparatus 100 at maximum exposure (when a white original or the like is input). In this way, the linearity of each element of CCD 1 is corrected, and the final output data is shown in Figure 3, in which vertical fluctuations in level from white to black are almost eliminated at all positions of one line. (d)
Data like this can be obtained.

As described above, according to this embodiment, the data X used to raise the shading-corrected output data to the X power as correction data. RAM 9 is a correction data storage means in which is stored, and X is a calculation means. The i-pixel output signal correction device 200 equipped with the multiplier 10 performs the correction,
Data distortion due to deviations in linearity of each element of the CCD 1 can be reliably removed. For this reason, it is expected that the image quality of images obtained by CCDI will be improved, and even if the signal readout speed of CCD 1 is increased, image quality higher than that of conventional devices can be obtained. This opens the door to faster speeds for facsimile machines. Further, it is also possible to obtain higher quality image data by connecting the apparatuses of the present invention in multiple stages and providing each stage with correction data when inputting images with different light intensities.

In the embodiment, an X1 multiplier was used, but when the image sensor reads an image having a predetermined light intensity, the level of the output signal of the shading device is set to the same level in the main scanning direction of the image sensor. Depending on the correction data to be used, calculation means other than the Xo multiplier, such as a multiplier, may be used.

Further, the image sensor does not need to be a COD, and the present invention can be applied to any device that can detect the timing at which an output signal at each position in the main scanning direction is output from the image element.

[Effects of the Invention] As explained above, according to the present invention, the level of the output signal corresponding to each position in the main scanning direction of the R image element does not correspond linearly to the light intensity of the color of the input image. This makes it possible to accurately correct the situation, and it is possible to obtain high-quality image data.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing shading by a fluorescent lamp, and FIG. 3 is a diagram showing a transition of a signal corrected by the embodiment of the present invention. 1...CCD 2...Control circuit 3・A/D
Converter 4.8-ROM 5... Multiplier 6.9... RAM7... Divider 10... Xo multiplier 100... Shading correction V device 200... Imaging element output signal correction device Agent Patent Attorney Nori Chika Yudo Sanno −

Claims (1)

[Claims] A shading correction device that performs shading correction on an output signal of an image sensor is connected to a subsequent stage, and when the image sensor reads an image having a predetermined light intensity, the level of the output signal output from the shading correction device is adjusted to the level of the output signal of the image sensor. a correction data storage means in which correction data for achieving the same level in the main scanning direction is stored corresponding to each position in the main scanning direction; an output signal output from the shading correction device; and an original signal of this output signal. calculation means for calculating linearity correction for the output signal at each position in the main scanning direction of the image sensor based on the correction data in the correction data storage means corresponding to the position in the main scanning direction of the image sensor where the image sensor is obtained; An image sensor output signal correction device comprising: