JPH04196759A - Picture read processing unit - 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] Industrial Application Field The present invention is an image reading processing device that projects an image onto a photoelectric conversion element, converts the image information from the photoelectric conversion element into a digital signal, and converts it into a binary or multivalued signal. It is related to.

2. Description of the Prior Art An image reading and processing device is required to have a processing technology that can read the image information of a document faithfully, that is, with high precision and high gradation.

An example of the above-mentioned conventional image reading processing device will be described below without reference to the drawings.

FIG. 3 shows a block diagram of a conventional image reading and processing device. In FIG. 3, 100 is an analog image signal input terminal from a photoelectric conversion element, and 101 is an analog-to-digital converter (A/D converter). ), 102 is the data selector, 103.104 is the memory, 7 yen
105 and 106 are digital-to-analog converters (D/A converters), 107 is an A/D converter, and 108 is a digital image signal output terminal. To explain the operation, first, an analog image signal obtained by reading a standard white original is input to the A/D converter 101 from the terminal 100, and a digital output corresponding to the voltage value is input to the memory 103 by the data selector 102 and stored. Next, read the standard black original, and as before, check if the analog image signal is at terminal 100.
9 is input to the A/D converter 101, and a digital output corresponding to the voltage value is manually input and stored in the memory 104 by the data selector 102. Next, the standard white digital value of each photoelectric conversion element is input from the memory 103 to the D/A converter 105, and the corresponding analog value is applied to the upper limit reference voltage terminal of the A/D converter 107. do. Similarly, store the standard black digital value in memory 1.
04 to the D/A converter 106, and the corresponding analog value is applied to the lower limit reference voltage terminal of the A/D converter 107 to correct white shading and black shading of each photoelectric conversion element. be. (Unexamined Japanese Patent Publication No. 60
Problems to be Solved by the Invention However, the above configuration had the problem that two systems of memory and D/A converters were required for white and black, increasing the circuit scale. In view of the above problems, the present invention provides an image reading processing device that performs white correction and black correction with a circuit configuration that does not increase the circuit scale.

Means for Solving the Problems In order to solve the above problems, the image reading processing device of the present invention (L) is equipped with an A/D converter that converts image information from a photoelectric conversion element into a digital signal, and a standard white a first memory for storing a digital signal from the A/D converter for image information from the photoelectric conversion element when reading black; and a digital signal from the A/D converter for image information from the photoelectric conversion element when reading black; A D/A converter for converting the digital signal from the first storage means into an analog signal, and a second storage means for storing the analog signal from the D/A converter. Function The present invention has the above-described structure, and is capable of storing memory for white and black colors.
Only one system of D/A converters is required for each system, reducing the circuit scale.

Embodiment An image reading processing apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of the image reading processing apparatus according to an embodiment of the present invention. In FIG. 1, 1 is an analog image signal input terminal from a photoelectric conversion element, 2 is an A/D conversion terminal 3, 4
are the lower limit reference voltage terminal and the upper limit reference voltage terminal of the A/D converter 2, respectively. 5 is memory (first storage means)
, 6 is a D/A converter, 7 is a sample hold circuit as a second storage means for storing the analog signal from the D/A converter 6, and 8 is a digital image signal output terminal. 9
, 10, 11, and 12 are changeover switches, and 13 is a reference voltage source. The operation of the image reading processing apparatus configured as described above will be explained below using FIGS. 1 and 2. First, FIG. 2 is a block diagram showing each operation of FIG. 1. Figure 2 (a) shows the changeover switch 9.
．． 11 and 12 are connected to a and b, respectively. In this state, a standard white original is read and the image information digitized by the A/D converter 2 is stored in, for example, an odd address in the memory 5. Next, the image information read from a standard black original or with the illumination turned off and digitized by the A/D converter 2 is stored in an even address in the memory 5, for example.
The state shown is that they are connected to a, a, and b, respectively. In this state, the standard white original image information of the first bit pixel from the odd numbered address of the memory 5 is converted into an analog voltage by the output L D/A converter 6, and this is converted into an analog voltage by the sample hold circuit 7.
is applied to the upper limit reference voltage terminal 3 of the storage LA A/D converter 2. In Fig. 2, (c) is a changeover switch 9.10,
11 and 12 are connected to a, b, b, and a, respectively. In this state, the black original image information of the 1st bit pixel from the even address of the memory 5 is output.
The voltage is converted into an analog voltage by the A converter 6 and applied to the lower limit reference voltage terminal 3 of the A/D converter 2. In this state, when an analog image reading signal is input from the 1st bit pixel, the white shading correction is performed. High-precision, high-gradation digital image information that has been corrected for black shading is output to the digital image signal output terminal 8. This operation is executed within the time of one pixel. That is, the standard white voltage is A by the operation shown in Fig. 2(b).
After applying the standard black voltage to the upper limit reference voltage terminal of the A/D converter and applying the standard black voltage to the lower limit reference voltage terminal of the A/D converter in the operation shown in FIG. 2(c), input the analog image reading signal from the pixel. to correct white shading and black shading. This operation is performed for each pixel corresponding to the number of photoelectric conversion element pixels.

As described above, according to this embodiment, L; C1 system memory D
A /A converter and a simple sample-and-hold circuit serving as a storage means can provide high-precision, high-gradation digital image information, making it possible to read documents faithfully.

Effects of the Invention As described above, the present invention provides an A/D converter that converts image information from a photoelectric conversion element into a digital signal, and an A/D conversion of image information from the photoelectric conversion element when reading standard white. A first storage means for storing digital signals from the A/D converter and image information from the photoelectric conversion element when reading black; By providing a D/A converter that converts into a signal and a second storage means that stores the analog signal from the D/A converter, it is possible to obtain high-precision, high-gradation digital image information with a small-scale circuit configuration. It is now possible to read the document faithfully to the original.a

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an image reading processing device according to an embodiment of the present invention. FIG. 2 is a block diagram for explaining each operation of FIG. 1. FIG. 3 is a block diagram of a conventional image reading processing device. 1...Analog image signal input terminal, 2...A/D converter 3...A/D converter lower limit reference voltage terminal, 4...A
/D converter upper limit reference voltage terminal, 5... memory (first storage means), 6... D/A converter 7... sample hold circuit (second storage means), 8
... Digital image signal output terminal, 9, 10, 11, 12... Changeover switch, 13.
...Name of reference voltage representative Patent attorney Akira Okaji and 2 other people

Claims (4)

[Claims] (1) In an image reading processing device that projects images onto multiple photoelectric conversion elements and converts the image information from the photoelectric conversion elements into digital signals, an A/D that converts the image information from the photoelectric conversion elements into digital signals. converter, image information from the photoelectric conversion element when reading standard white, digital signal from the A/D converter, and image information from the photoelectric conversion element when reading black;
a first storage means for storing a digital signal from the A/D converter; a D/A converter for converting the digital signal from the first storage means into an analog signal; an image reading processing device comprising: second storage means for storing an analog signal of the image reading processing device; (2) A second device that stores analog signals from the D/A converter.
2. The image reading processing apparatus according to claim 1, wherein a sample and hold circuit is used as the storage means. (3) The image reading processing device according to claim 2, wherein the image information from the photoelectric conversion element when reading standard black is black. (4) The image reading processing device according to claim 2, wherein the image information from the photoelectric conversion element is black when the illumination is turned off.