JPH03289873A - Picture signal correction circuit - Google Patents

Abstract

PURPOSE:To reduce the cost of the circuit by employing an analog multiplexer for a circuit storing and retarding video signals for one picture element. CONSTITUTION:When an analog video signal from an image sensor is inputted to a noninverting input terminal of an amplifier A1, in which the signal is amplified at a prescribed gain and the amplified signal is outputted to an analog multiplexer 10. When control signals 2, 3 are inputted to a switch control 9 in the analog multiplexer 10, a voltage is stored in a capacitor C1 or C2. When control inputs A, B are at L, H or H, H, the voltage by one picture element stored in the capacitor C1 or C2 via a channel 1X or 3Y is delayed and inputted to an inverting input terminal of an amplifier A2. A video signal 6 of one preceding picture element is subtracted from a double voltage of a current video signal and a signal 7 being the result of subtraction is outputted to, e.g. an A/D converter.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image signal correction circuit that corrects an analog video signal from an image sensor in, for example, a facsimile.

(Prior Art) In recent years, with the diversification of information, one of the means of transmitting information, for example, facsimile, has become widespread.

This is how information such as characters and figures is divided into small sections (pixels) on the sending side.
After decomposing the pixels, an electric signal proportional to the density is encoded and sent, and on the receiving side, the encoded pixels are combined again and the information is reproduced.

Furthermore, facsimile machines are becoming more popular in ordinary households due to miniaturization due to the development of electronic technology.

FIG. 5 shows an image signal correction circuit that corrects the video signal in the above-mentioned facsimile.

As shown in the figure, the image signal correction circuit includes an image sensor (not shown) that reads information such as characters and figures on the paper.
An A/D converter 1 is provided for converting an analog video signal from a digital video signal into a digital video signal. The image signal correction circuit also includes a memory 2 that stores the converted digital video signal as data, an arithmetic circuit 3 that performs signal correction calculations based on the stored data, and a calculation circuit 3 that performs signal correction calculations based on the stored data. A control section 4 is provided for controlling the system.

In such an image signal correction circuit, information such as characters and figures on the paper read by the image sensor is converted into a digital video signal by the A/D converter 1, and then stored in the memory 2 as data. Stored. Next, the data stored in the memory 2 is output after a signal correction operation is performed by the arithmetic circuit 3 controlled by the control section 4.

Then, based on this calculation result, an electrical signal proportional to the density of information such as characters and graphics is encoded and sent to the receiving side.

(Problems to be Solved by the Invention) However, in the conventional image signal correction circuit described above,
Since the amount of information such as characters and graphics read by the optical sensor is large, it is impossible to share the memory with other circuits. For this reason, a dedicated memory is required, and a complicated arithmetic circuit 3 is required due to its circuit configuration, which hinders efforts to reduce the cost of the device.

In addition, since there are restrictions on the calculation time by the calculation circuit 3,
It is not suitable for speeding up encoding processing.

Furthermore, it requires the development of a dedicated program, which increases the burden on the software.

The present invention was made in response to these circumstances, and
It is an object of the present invention to provide an image signal correction circuit that can reduce the burden on software, increase the speed of signal processing, and reduce the cost of the device.

(Means for Solving the Problem) In order to achieve the above object, the image signal correction circuit of the present invention includes a storage means for storing an analog video signal from an image sensor, and a video signal for one pixel that is delayed. 1
The present invention is characterized by comprising a pixel delay means, and an arithmetic means for calculating a video signal of one pixel before, which has been delayed by the one pixel delay means, and a video signal of one current pixel.

(Function) In the image signal correction circuit of the present invention, when the storage means stores an analog video signal from the image sensor, the one pixel delay means delays the video signal for one pixel. Next, the calculation means performs calculations on the video signal of one pixel before, which has been delayed by the one-pixel delay means, and the video signal of the current one pixel.

Therefore, by using a simple circuit configuration, such as an analog multiplexer, as a circuit for storing and delaying a video signal for one pixel, the cost of the apparatus can be reduced.

Furthermore, since it is possible to handle this using hardware, the burden on software is reduced.

Furthermore, since arithmetic processing is performed before A/D conversion, signal processing speed can be increased.

(Example) Hereinafter, details of an example of the present invention will be described based on the drawings.

FIG. 1 shows an embodiment in which the image signal correction circuit of the present invention is applied to a facsimile.

As shown in the figure, the image signal correction circuit includes a memory 5 consisting of an analog multiplexer that stores an analog video signal from an image sensor (not shown), and a 1-pixel delay circuit 6 that delays the video signal for one pixel. , this 1l
An arithmetic unit 7 is provided which performs an arithmetic operation between the video signal of one pixel before by the ii-element delay circuit 6 and the video signal of one current pixel.

FIG. 2 shows a specific example of the image signal correction circuit of FIG. 1.

As shown in the figure, the memory 5 and the one-pixel delay circuit 6 are provided with an analog multiplexer 10 that includes an amplifier AI and capacitors CI and C2 and whose channels are switched by a switch control 9.

Here, the channels of the analog multiplexer 10 are:
It is said to be 4 channels x 2. Further, the analog multiplexer 10 operates according to the truth value shown in FIG. 3, for example.

The calculation unit 7 is provided with an amplifier A2 having an input resistor R1 and a gain setting resistor R2 connected to the inverting input terminal side, and an input resistor R3 connected to the non-inverting input terminal side.

The input characteristics of this circuit are eO= ((R2/R1) +1) ・e2−(R2/
R1) ・01. However, eO is the output voltage of amplifier A2, and el is 1
The video signal voltage before the pixel, 82, indicates the current video signal voltage.

Next, the operation of the image signal correction circuit will be explained using FIG. Note that in the figures described below, the operating gain (R2/R1) of the arithmetic unit 7 is assumed to be 1 for convenience of explanation. Therefore, eO=2 C2-el.

Further, α and β shown in the figure each correspond to one pixel, and indicate high and low voltages.

First, when the analog video signal ■ from the image sensor is input to the non-inverting input terminal of the amplifier AI, it is amplified with a predetermined gain, and then sent to the analog multiplexer 10.
output to the side.

On the analog multiplexer 10 side, when the control signals (1) and (2) are input to the switch control 9, a voltage is accumulated in the capacitor CI or C2.

In other words, at the truth value in Figure 3, control human power A
, B are H, H or H, L, the voltage for one pixel of the signal (2) or (2) is accumulated in the capacitor CI or C2 via the channel 3X or IY.

Next, at the truth value in Figure 3, control human power A
, B, H or H, H, channel IX or 3
The voltage for one pixel accumulated in the capacitor C1 or C2 via Y is delayed and input to the inverting input terminal side of the amplifier A2. At this time, the signal input to the inverting input terminal side is the signal ■.

Amplifier A2 converts the voltage from twice the current video signal to 1
Subtraction is performed with the video signal (2) before the pixel, and as a result of the subtraction, the signal (2) is output to, for example, an A/D converter (not shown).

In this way, in this embodiment, an analog multiplexer with a simple circuit configuration is used as a circuit for storing and delaying a video signal for one pixel, so that the cost of the apparatus can be reduced.

Furthermore, since it is possible to handle this using hardware, the burden on software is reduced.

Furthermore, since arithmetic processing is performed before A/D conversion, signal processing speed can be increased.

Furthermore, in this embodiment, a voltage twice as high as the video signal for the current one pixel is subtracted from the video signal for the previous pixel. Therefore, as shown by the signal (2) in FIG. 4, it is possible to emphasize the edge portion signal that changes from black to white or from white to black, thereby improving the resolution of the image sensor in the scanning direction.

Furthermore, since the resolution of the image sensor in the scanning direction is improved, the outline of the image becomes clearer, so that thin lines, small dots, etc. can be reproduced clearly.

In this embodiment, the case where the image signal correction circuit of the present invention is applied to a facsimile machine has been described, but the application is not limited to this example, and may be applied to other devices such as a copying machine or an image scanner. This makes it possible to reduce the cost of applicable equipment.

(Effects of the Invention) As explained above, according to the image signal correction circuit of the present invention, a simple circuit configuration such as an analog multiplexer is used as a circuit for storing and delaying a video signal for one pixel. The cost of the device can be reduced.

Furthermore, since it is possible to handle this using hardware, the burden on software is reduced.

Furthermore, since arithmetic processing is performed before A/D conversion, signal processing speed can be increased.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the image signal correction circuit of the present invention applied to a facsimile, and FIG.
A circuit diagram showing an example of a specific circuit configuration of the image signal correction circuit shown in the figure, Fig. 3 is a table showing truth values in the operation of the analog multiplexer shown in Fig. 1, and Fig. 4 shows the image signal correction circuit shown in Fig. 1. FIG. 5 is a block diagram showing a conventional image signal correction circuit. 5... Memory, 6... 1 pixel delay circuit, 7... Arithmetic unit, 9... Switch control, 10... Analog multiplexer, AI, A2... Amplifier, CI
, C2...Capacitor, R1, R3...Input resistance, R2...[Gain setting resistance.

Claims (1)

[Claims] (1) A storage means for storing an analog video signal from an image sensor, a 1-pixel delay means for delaying a video signal for one pixel, and a video signal of the previous pixel delayed by the 1-pixel delay means and the current video signal. 1. An image signal correction circuit comprising: arithmetic means for performing an arithmetic operation with a video signal for one pixel.