JPH0440062A - Image sensor pixel sensitivity correction device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is applicable to facsimiles, image scanners, etc.
The present invention relates to an image sensor-pixel sensitivity correction device used in a document reading device.

[Conventional technology]

Conventionally, in order to correct variations in pixel sensitivity of an image sensor consisting of multiple pixels to a video signal, a uniform white material (hereinafter referred to as standard white material) was read by the image sensor, and its raw material was read by the image sensor. This information was converted into a digital signal, stored in memory as a correction signal, and read out as needed to be used to correct the video signal.

FIG. 3 is a perspective view showing an example of a document reading system used in a conventional facsimile. , is read by an image sensor 3 having a plurality of pixels arranged in a line, and its output level is used as a sensitivity correction signal.

[Problem to be solved by the invention]

However, in the above conventional example, when the standard white material 2 is read by the image sensor 3, there are variations in the sensitivity of the plurality of pixels of the image sensor 3, and furthermore, there is dust on the surface of the platen roller 2. If the dirt is opaque like glue from adhesive tape or dark like eraser scum, it may be darker than the surface color of platen roller 2. The color output level will be incorrect, and the correction signal will be inaccurate.
The problem of not being able to properly correct the video signal was solved.

This invention has been accomplished by solving the above conventional problems, and aims to provide an image sensor-pixel sensitivity correction device that is less affected by local stains, discoloration, etc. of standard white coloring material. It is something.

(Means for solving !It) Therefore, the image sensor pixel sensitivity correction device according to the present invention corrects the variation in pixel sensitivity of the image sensor consisting of a plurality of pixels to a video signal. a correction signal generator that is a sensitivity correction device and outputs a correction signal corrected so that when a standard white material is read by an image sensor, a pixel output decreases within a certain percentage with respect to an output of a pixel scanned immediately before; a correction information memory that stores the correction signal; an A-D converter that reads the correction signal from the correction information memory, corrects the video signal, and outputs a video signal with image sensor pixel sensitivity corrected; The above object is achieved by a configuration characterized in that the correction signal generation function of the correction signal generator is stopped and the input video signal is output without being corrected. .

[For production]

With the above configuration, when the standard white coloring material is read by the image sensor, in addition to variations in the sensitivity of the multiple pixels of the image sensor itself, variations in the output between pixels will occur due to dirt and discoloration of the standard white coloring material. , the correction signal generator outputs a correction signal corrected so that the decrease in the output of a pixel whose output is lower than the output of the pixel scanned immediately before is within a certain percentage of the output of the pixel scanned immediately before. The correction signal is then stored in the correction information memory. The AD converter corrects the video signal using the correction signal read from the correction information memory and outputs a video signal with image sensor pixel sensitivity corrected.

Note that the switching means can select between the output of the correction signal of the correction signal generator and the output that stops generation of the correction signal and does not correct the input video signal. In other words, when switching to outputting the video signal as is, A-
The D converter can input the video signal output from the correction signal generator and correct the pixel sensitivity of the image sensor using the correction signal.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The image sensor pixel sensitivity correction signal generation device according to the present invention will be described below with reference to embodiments.

FIG. 2 is an explanatory diagram showing an output waveform when a standard white material, for example, the platen roller 2 or a white original is read by the image sensor 3.

In the figure, the solid line portion 5 of the waveform between P and Q is when the dust 4 attached to the platen roller 2 is read, and the waveform portion 5 is incorrect as a correction signal. . Further, a dotted line 6 from P to Q is a normal waveform when there is no dust. The one-point button 1IA7 from P to Q is the waveform of the correction signal according to this embodiment.

FIG. 1 is a block diagram showing one embodiment of the present invention. The correction signal generator 8 is equipped with a time constant circuit 8a consisting of a capacitor O and a resistor R. Then, only when reading the standard white color material and creating a correction signal, turn on the switch (SW), which is the switching means 9, to delay the change in the falling direction of the image sensor pixel output and correct it. It is configured to output a signal. Note that the switch (SW) is in an OFF state when reading a document.

The amount of delay is determined based on experimental data, such as the magnitude of the output change within a normal range as shown in area A in FIG. 2, and the degree of darkness of the dust 4. The correction signal output from the correction signal generator is converted into a digital signal by an A/D converter 10, and the signal segment is inputted to a correction information memory 12 via a device 11 and stored therein.

Next, the correction of the video signal using the correction signal in this embodiment will be explained. A correction signal stored in the correction information memory 12 is applied to the reference voltage input terminal V REF of the A-D converter 10, and the signal is divided into the signals by the device 11. in synchronization with the pixel scanning of the image sensor 3. input via the D-A converter 14,
A division operation is performed on the manually generated video signal that has passed through the correction signal generation circuit 8 to output a video signal in which sensitivity variations between pixels of the pixels constituting the image sensor 3 have been corrected.

In FIG. 1, the peak value detection circuit 13 is for detecting the largest output signal of the video signal and holding that level as a peak signal. When creating the voltage, input it directly to the reference voltage input terminal VREP of the A-D converter 10.

Then, when correcting the sensitivity using the correction signal, pull out the correction signal from the correction information memory 12,
At the same time, the peak signal is also introduced into the D-A converter 14.
It is input as a reference voltage to the A converter 14, produces a correction signal, and guides it to the above-mentioned A-D converter 1o. The output signal of the A-D converter 1o at this time is a video signal subjected to sensitivity correction.

In this example, the platen roller 2 is used as the standard white color material.
was used, but other standard white plates etc. may also be used.

〔Effect of the invention〕

As explained above, according to the present invention, when a standard white material is read with an image sensor consisting of a plurality of pixels,
The correction signal generator outputs a correction signal corrected so that the output drop of a pixel whose output is lower than that of the pixel scanned immediately before is within a certain percentage of the output of the pixel scanned immediately before, and the correction signal is stored in the correction information memory. be remembered. The AD converter corrects the video signal using the correction signal read from the correction information memory and outputs a video signal with image sensor pixel sensitivity corrected.

It should be noted that the switching means can switch between the output of the correction signal from the correction signal generator and the output of the correction signal by stopping the generation of the correction signal and not correcting the manually generated video signal.

In other words, when an image sensor reads a standard white coloring material, the image sensor is not only sensitive to variations in the sensitivity of the plurality of pixels of the image sensor itself, but also to variations in output between pixels due to dirt and discoloration of the standard white coloring material. It is possible to provide an image sensor pixel sensitivity correction device capable of correcting a video output obtained by reading an original.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment according to the present invention, FIG. 2 is an explanatory diagram of an image sensor output waveform, and FIG. 3 is a perspective view of a conventional document reading system. 1 is the original, 2 is the platen roller which is a standard white color material, 3
The image sensor 14 is dirt attached to the platen roller, 5 is the output waveform of the dirty part, 6 is the output waveform when no dirt is attached, 7 is the output waveform corrected according to the example, 8 is the correction Signal generator, 8a is a time constant circuit,
9 is a switching means, 10 is an AD converter, 11 is a signal divider, 12 is a correction information memory, 13 is a peak value detection circuit, and 14 is a DA converter.

Claims (1)

[Claims] An image sensor pixel sensitivity correction device that corrects variations in pixel sensitivity of an image sensor consisting of multiple pixels to a video signal, and when a standard white color material is read with an image sensor, the pixel output is an output corresponding to the output of the pixel that was scanned immediately before. a correction signal generator that outputs a correction signal corrected so that the decrease is within a certain percentage; a correction information memory that stores the correction signal; and a correction information memory that reads the correction signal from the correction information memory to correct the video signal. A that outputs a video signal with the image sensor pixel sensitivity corrected.
- An image sensor pixel sensitivity correction device comprising: a D converter; and a switching means that stops the correction signal generation function of the correction signal generator and outputs the input video signal without correction.