JPS61244166A - Original reader - Google Patents

Abstract

PURPOSE:To read a black-and-white original without lowering resolution by switching the output processing of a line image sensor to either of a binary coding circuit and a chrominance signal processing circuit according to the kind of the original. CONSTITUTION:When the original is a black-and-white original, the output of the line image sensor 1 is inputted to a sample holding S/N circuit 6 by a multiplexer 4 to obtain a signal sampled and held at every bit of the line image sensor 1. The output signal of the S/H circuit 6 is inputted to one input of a comparator 7. Threshold values which are different for respective colors of a striped filter for color separation on the line image sensor 1 are inputted to the other input terminal of the comparator 7. When one input signal of the comparator 7 correspond to a light receiving cell provided with filters R, G, and B, the threshold values are denoted as ER, EG, and EG and it is compared by the comparator 7 to obtain a binary coded signal. The threshold values are switched by a multiplexer 8 in synchronism with an output signal for one bit of the line image sensor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image reading and depositing apparatus using an image sensor in which a striped filter for color separation is integrally provided on a sensor.

Conventional technology Conventionally, a light receiving cell 1 is placed on the light receiving section of a line image sensor.
Various apparatuses have been devised for reading color originals using a line image sensor provided in such a way that one stripe of a striped filter for color separation corresponds to each color original (for example, Japanese Patent Application Laid-Open No. 58-178660 Publication No.).

The conventional method will be explained in detail. There is a striped filter array for color separation as shown in FIG. However, R, G, and B are each red.

These are green and blue color separation filters, and each filter corresponds to one bit of the line image sensor. In this case, the image information for one pixel on the document is composed of three consecutive bits (one bit each for R, G, and B) from the line image sensor, and a color signal is extracted for each color filter.
It was configured to perform predetermined signal processing and obtain color signals of three colors.

Problems to be Solved by the Invention In the image reading device described above, when reading a black and white original such as a document, in order to obtain an image signal of one pixel on the original from three consecutive bits of the line image sensor, for example,
If there is a black line on the document with a width of 2 pits or less on the line image sensor, accurate information cannot be obtained, and the line image sensor is There is a problem in that the resolution is lower than when reading so that each bit corresponds to one pixel of a black and white original.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention converts the output of a line image sensor in which a striped filter for color separation is provided on the light receiving part into a striped filter for color separation. A binarization circuit that binarizes the output of each color using a different threshold value for each color, and a color signal processing circuit that performs predetermined color signal processing on the processing output when a color original is read by the line image sensor. and a switching means for performing output processing of the line image sensor by either the binarization circuit or the color signal processing circuit depending on the type of document.

Function The present invention provides an embodiment in which the resolution when a monochrome original is read by the above-described means can be made the same as the resolution when read by a line image sensor without passing through a striped filter for color separation. EXAMPLE Hereinafter, an embodiment of the present invention will be explained using FIGS. 1 and 2. FIG. 1 is a block diagram of an embodiment of the present invention, in which a stripe-shaped filter for color separation arranged in a predetermined periodic pattern is connected to one light-receiving cell of the light-receiving section. 2 is a line image sensor drive circuit that outputs pulses necessary to drive the line image sensor 1; 3 is a line image sensor drive circuit that outputs pulses necessary to drive the line image sensor 1; 4 is a first switching means (for example, a multiplexer) that selects two signal processing circuits to be described later depending on the type of the original; 6 is a first switching means (for example, a multiplexer) for selecting the output of the line image sensor 1 when the original is a color original; A color signal processing circuit for obtaining each color signal (RGB signal) from the output image signal, 6
In the case of a black and white original, a sample/hold function is used to sample and hold the output image signal for each bit of the line image sensor 1.
A hold circuit, 8 a comparator that compares the output of the sample and hold circuit with a different threshold value for each color of the filter on the line image sensor, and 8 a threshold value of the comparator 7 according to the output of the sample and hold circuit. Fig. 2 is a timing diagram explaining the operation of this embodiment.◇When the original is a color original, the multiplexer 4 switches the input to the a side. The color signal processing circuit 6 performs processing such as γ correction and two-color correction to obtain R, G, and B image signals.

If the original is black and white, the second
The output of the line image sensor 1 as shown in FIG. Get a signal. The output signal of the sipule hold circuit is used as one input signal of the comparator 7. A different threshold value is inputted to the other input terminal of the comparator 7 for each color of the striped filter for color separation on the line image sensor 1. In this case, using a different threshold value for each color of the filter is as follows.
This is because the transmission characteristics of the filter differ depending on the color of the filter, and the output for the same density on the document differs depending on the filter.

As shown in FIG. 2 (C+) and (d), when one input signal of the comparator 7 is a signal corresponding to a light receiving cell equipped with an H filter, the threshold value is set to ER, and the G filter is In the case of a signal corresponding to a light-receiving cell provided with a filter, the threshold value is set to EG, and in the case of a signal corresponding to a light-receiving cell provided with a filter B, the threshold value is set to EG and compared by a comparator 7, as shown in FIG. A binarized signal as shown in d) is obtained.

This switching of the threshold value is performed by one of the line image sensors 1.
The multiplexer 8 is the switching means that performs the switching in synchronization with the output signal for K. In this case, the threshold of the binarization circuit 7 is a fixed level that is different for each color filter. Various methods may be used, such as a floating slice method using image signals for each color filter.

Next, a second embodiment of the present invention will be described with reference to FIG. Items that are the same as those in Figure 1 are given the same numbers 07-
R, G, and B are threshold values ER2EG and EB for the output corresponding to the filter color of the color separation filter, and the binarization circuit 9 performs binarization in synchronization with each filter of the color separation filter 7-R. , G, and B, and 10 is an OR gate that receives the three outputs of the binarization circuit as inputs.

The multiplexer 9 is synchronized with the output signal corresponding to the filter color of the color separation filter on the line image sensor 1.
and the subsequent binarization circuit 7-R,G.

One of B is selected and binarized, and the binarization circuit 7-
By passing the three outputs of R, G, and B through an OR gate,
A serial black and white binary signal can be obtained.

Effects of the Invention As described above, according to the present invention, a monochrome original can be read with an extremely simple configuration without lowering the resolution, and the industrial angle is extremely large.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an image reading device in one embodiment of the present invention, FIG. 2 is a timing diagram for explaining the operation of the device, and FIG. 3 is a block diagram of an image reading device in another embodiment of the present invention. The block diagram in FIG. 4 is a diagram for explaining problems with a conventional image reading device. 1...Line image sensor, 2...
Line image sensor drive circuit, 3...Amplifier, 4,8゜9...Multiplexer, 6...
...Color signal processing circuit, 6...Sample/hold circuit, 7.7-R,G. B...Binarization circuit, 1o...OR gate. Ill Cause I2 Figure (d) -11111 ■Bottom T- Figure 4 IJ, Kei Prefecture 111

Claims (1)

[Scope of Claims] Color separation striped filters arranged in a predetermined periodic pattern are arranged such that one stripe of the color separation striped filter corresponds to one light receiving cell. a line image sensor provided on the light receiving section; a color signal processing circuit that reads a color document with the line image sensor and performs predetermined color signal processing; and a plurality of colors separated by the striped filter for color separation. a binarization circuit that performs binarization using a predetermined threshold value that is different for each color signal; and one of the color signal processing circuit and the binarization circuit processes the output of the line image sensor. What is claimed is: 1. A document reading device comprising: switching means for switching between