JPH0213509B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image signal correction device in a reading section of a facsimile machine or the like.

Configuration of conventional example and its problems The reading section of the conventional facsimile device has the configuration as shown in Fig. 1, in which an image signal PIX is input from a scanner (not shown) to terminal 1, and the image signal PIX is read from the original and photoelectrically changed. is sent to a picture signal distortion correction unit (VPU) 8 through an automatic background adjustment circuit (ABC) 9 incorporating an amplifier 2 and an ABC control circuit 6,
The image signal is converted into an analog-to-digital signal by an A/D converter (ADC) 3, and is multiplied with data preset in a connected external memory (ROM) 5 to correct image signal distortion and output. ing. Here, to briefly explain the VPU 8, this VPU 8 incorporates an ADC 3 and a multiplexer (MUL) 4, and the image signal read by a solid-state plane scanning type is normally
Since it is affected by distortions such as non-uniformity of the illumination light source, characteristics of the lens used, and variations in the sensitivity of the image sensor, if output as is, the image quality will inevitably deteriorate, and the circuit used to correct this will be
It is VPU8.

However, ROM, which is an external memory like the one mentioned above,
According to the conventional VPU 8 using the VPU 5, it is not possible to cope with fluctuations in distortion characteristics due to factors such as temperature and aging, resulting in the inconvenience that the data set in advance cannot be corrected correctly.

As a solution to this problem, a random access memory (RAM) 10 is connected to the ROM 5 of the VPU 8 as shown in Figure 2, and the ABC control circuit is controlled by a control signal that determines the level of the image signal output from the VPU 8. It is conceivable to control 6.
With this configuration, the optimal data for the distortion waveform is
Since it can be written to the RAM 10 and output to the MUL 4, it is possible to cope with fluctuations in distortion characteristics due to factors such as temperature and aging.

However, with this configuration, RAM1 used as external memory is
A random value is written to 0, and as a result, the correction coefficient input to VPU8 is not an accurate value, and the ABC control signal (overflow signal (OVF)) from VPU8 malfunctions, causing VPU8
distortion correction becomes unstable.

Purpose of the Invention The present invention solves the above-mentioned drawbacks of the prior art, and aims to always
The optimal correction coefficient can be written to RAM, preventing incorrect operation of the overflow signal (OVF),
An object of the present invention is to provide an image signal correction device that can perform accurate correction processing even when a distortion waveform changes.

Structure of the Invention In order to achieve the above object, the present invention provides an automatic background adjustment circuit comprising an attenuator that attenuates an analog image signal input from a scanner and a control means that controls the attenuation ratio of this attenuator. An A/D converter that converts the analog image signal output from the automatic background adjustment circuit into a digital image signal, a correction coefficient calculation means that calculates a correction coefficient for correcting image signal distortion, and an output from the A/D converter. an image signal distortion correction unit comprising a digital calculation means for calculating the digital image signal and the correction coefficient and outputting a digital image signal subjected to image signal distortion correction; a rewritable storage means for reading and storing correction coefficients, reading out the correction coefficients and inputting them to the digital calculation means in synchronization with the output of the image signal from the scanner; and storing an initial value of the storage means in advance. , a buffer for outputting the initial value to the storage means before the digital calculation means calculates the correction coefficient to the storage means; The present invention is characterized in that the attenuation ratio of the attenuator is controlled by the determined control signal.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 3 of the drawings. In the image signal correction device for the facsimile device shown in FIG. 3, 11 is a signal input terminal for inputting the image signal PIX from a scanner (not shown), and the input image signal PIX changes to the resistance value of the resistors R ₁₁ and R ₁₂ . It is amplified by amplifier 12 with a conversion factor thus determined. The transistor TR ₁₁ serves as a variable impedance and serves as an attenuator depending on the resistance ratio with the resistor R ₁₃ . This attenuator controls the attenuation ratio by the resistance ratio and keeps the image signal PIX constant. 16 is an ABC control circuit that determines whether or not to charge the capacitor C ₁₁ to change the gate voltage of the transistor TR ₁₁ ; 13;
is an analog-to-digital converter (ADC), and the automatic background adjustment circuit 19 includes the above-mentioned amplifier 12, ABC control circuit 16, resistors R ₁₁ , R ₁₂ ,
It consists of R ₁₃ and capacitor C ₁₁ . 18
is a picture signal distortion correction unit (VPU), which includes an analog-digital converter (ADC) 13, a multiplexer (MUL) 14 for performing multiplication processing with a correction value from an external memory RAM 15 to correct picture signal distortion, and ROM that stores distortion correction coefficients
The image signal PIX corrected by a buffer (BUFF) 22 is outputted from an output terminal 17. Batsuhua 22 is RAM 15
This is for writing the initial value to , and 23 is
It serves as a control signal (*RAME) that selectively selects either the RAM 15 or the buffer 22. 24 is a write/read signal (*RAMW) to the RAM 15, and 25 is an ABC control circuit OVF.

The operation of the image signal correction device configured as described above is as follows. That is, first, the *RAMW signal 24 is set to "L" level to make the RAM 15 ready for writing, and then the *RAME signal 23 is set to "H" level.
The initial value is set as the level through buffer 22.
After writing to RAM15 *RAMW signal 24
is set to "H" level *RAM signal 23 is set to "L" level. Therefore, when the image signal PIX scanned on the white board is inputted from the input terminal 11, it is amplified by the amplifier 12 according to the ratio of the resistors R ₁₁ and R ₁₂ , and then sent to the ADC 13.
The signal is converted into a digital signal and sent to the multiplexer 14 as a digital signal. At the same time, the initial value written by the above process is written to RAM15.
The multiplexer 14 multiplies the digital signal PIX by the initial value. Therefore
The ABC control circuit 16 controls the OVF signal 25 to be at "H" level (for example, the peak value of the image signal is 5V).
makes the gate voltage of transistor _TR11 variable. The gate voltage of the transistor TR ₁₁ when the OVF signal 25 goes to "H" level is maintained as it is, and in that state, the RAMW signal 24 is set to "L" level to make the RAM 15 ready for writing again. Here, the image signal that scanned the white board next
PIX is converted into a digital signal by ADC13,
Calculate the corresponding distortion correction coefficient in ROM20
Store in RAM15. The above processing is performed for all image signals of one line. After this process, *
The RAMW signal 24 becomes "H" level.

This process is performed using two lines of image signals obtained by scanning the white board. Thereafter, the image signal PIX obtained by scanning the original passes through the automatic background adjustment circuit 19, is digitally converted by the ADC 13, and is sent to the multiplexer 14. At the same time, the correction coefficient written in the above processing is read from the RAM 15 and multiplied by the multiplexer 14 to remove image signal distortion.

The OVF signal 25 controls the attenuation ratio of the attenuator of the automatic background adjustment circuit 19 depending on the level of the digital image signal output from the MUL 14 in order to provide the ADC 13 with an optimal input image signal.

Effects of the Invention According to the present invention, by setting an initial value in external RAM, it is possible to always output an accurate overflow signal (OVF) without writing random values to RAM even when the power is turned on. .
As a result, it is possible to correctly correct the image signal distortion that occurs in the facsimile reading section, and in particular, even if the distortion characteristics change due to any cause, the distortion can be accurately corrected by using the appropriate correction value corresponding to the change. The transmission performance of facsimile devices and the like can be significantly improved.

[Brief explanation of drawings]

1 and 2 are block diagrams showing the conventional configuration of an image signal distortion correction device in a facsimile device, and FIG. 3 is a block diagram showing an image signal distortion correction device in a facsimile device according to an embodiment of the present invention. 11...Picture signal input terminal, 12...Amplifier, 1
3...A/D converter, 14...Multiplexer (MUL), 15...External memory RAM, 16...
...Automatic background adjustment circuit, 17...Picture signal output terminal,
18... Image signal distortion correction unit (VPU), 20... Correction coefficient storage unit ROM, 22... Buffer for initial value setting, 23... RAM/buffer select signal,
24...RAM write read signal, 25...OVF
signal.

Claims (1)

[Claims] 1 An automatic background adjustment circuit consisting of an attenuator that attenuates an analog image signal input from a scanner and a control means that controls the attenuation ratio of this attenuator, and an automatic background adjustment circuit that converts the analog image signal output from the automatic background adjustment circuit into a digital image An A/D converter for converting into a signal, a correction coefficient calculating means for calculating a correction coefficient for correcting image signal distortion, and calculating the digital image signal output from the A/D converter and the correction coefficient, an image signal distortion correction section comprising a digital calculation means for outputting a digital image signal subjected to image signal distortion correction; and a correction coefficient calculated by the correction coefficient calculation means, which is read and stored, and the image signal from the scanner is read and stored. a rewritable storage means for reading out the correction coefficient and inputting it to the digital calculation means in synchronization with the output of the storage means; and a rewritable storage means for storing the initial value of the storage means in advance, and the digital calculation means storing the correction coefficient in the storage means. and a buffer for outputting the initial value to the storage means before calculation, and the attenuation ratio of the attenuator is controlled by a control signal that determines the magnitude of the level of the digital image signal output from the digital calculation means. An image signal correction device characterized by: