JPH0722331B2 - Semiconductor integrated circuit for image signal correction - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to an image signal correcting semiconductor integrated circuit that performs dark correction or shading correction on an image signal.

[Prior art]

When an image of a document is read by an image sensor, the output of the image sensor is subjected to corrections such as dark correction and shading correction and then output as an image signal. FIG. 4 shows such an image reading device. In FIG. 4, 1 is an image, 2 is a light source, 3 is an image sensor, and 4 is
An AD conversion circuit, 5 is a dark correction circuit, 6 is a shading correction circuit, and 7 is an output terminal. The dark correction circuit 5 and the shading correction circuit 6 are configured as a semiconductor integrated circuit. The image sensor 3 reads an image by receiving the reflected light of the image 1 illuminated by the light source 2, and the output thereof is converted into a digital amount by the AD conversion circuit 4. Then, after being respectively corrected by the dark correction circuit 5 and the shading correction circuit 6, the image signal is output from the output terminal 7. FIG. 5 shows a conventional semiconductor integrated circuit for image signal correction. Reference numerals correspond to those in FIG. 4, 8 is a data input terminal, 9 is a clock input terminal, 10 is a D flip-flop,
11 is a subtractor, 12 is a D flip-flop, 13 is a line memory, 14 is a timing controller, 15 is a start signal line, 16 is a write command signal line, 17 is an address signal line, 18
Is a write enable signal line, 19 is an output data enable signal line, 20 is a D flip-flop, 21 is a divider, 22 is D
Flip-flop, 23 is a line memory, 24 is a timing controller, 25 is a start signal line, 26 is a write command signal line, 27 is an address signal line, 28 is a write enable signal line, and 29 is an output data enable signal line. The D flip-flops 10, 12, 20, 22 are provided for synchronizing data with the clock when sending data to the next stage.
The line memories 13 and 23 are memories for storing data for one line (row) of an image, and are RAM (random.
Access memory) is used. The timing controllers 14 and 24 are for timing the operation of the respective correction circuits. AD means address, WE means write enable, and DE means data enable. Next, the operation of the circuit will be described. Prior to the correction, the following preparations are made. First, the image 1 in FIG. 4 is used as the black reference plane, and the light source 2 is turned off. The output of the image sensor 3 at this time is input to the data input terminal 8 of FIG. It is written in the line memory 13 as black reference data Bi. Writing is performed according to the AD signal and the WE signal from the timing controller 14. This is used as a reference value for dark correction. FIG. 6 is a diagram for explaining the dark correction, in which the horizontal axis represents the line direction position (longitudinal direction of the image sensor 3) and the vertical axis represents the output of the image sensor 3. FIG. 6A shows the black reference data Bi. The output of the image sensor 3 when the black reference plane is read is ideally zero, but it is not actually zero, and some output is output as shown in the figure. This is, so to speak, an offset amount. Next, the image 1 is used as the white reference plane, and the light source 2 is turned on. The output of the image sensor 3 at this time is also inputted to the data input terminal 8 of FIG. 5 via the AD conversion circuit 4. The difference is Wi-Bi with the black reference data Bi written in the line memory 13 by the subtractor 11 as white reference data Wi.
This difference is sent to the shading correction circuit 6 and written in the line memory 23. This is used as a reference value for shading correction. The image 1 is set as the image to be read, the light source 2 is turned on, and the image data to the data input terminal 8 when read by the image sensor 3 is Vi. Then, the subtractor 11 obtains the difference Vi-Bi between Vi and the black reference data Bi. Taking this difference is dark correction, and in FIG. 6B, it is correction that subtracts the black reference data Bi that is the offset amount from Vi. The dark-corrected image data Vi-Bi is divided by Wi-Bi stored in the line memory 23 in the divider 21 of the shading correction circuit 6. As a result Is the image data that has undergone shading correction. This is output from the output terminal 7.

[Problems to be Solved by the Invention]

However, the above-described conventional semiconductor integrated circuit for image signal correction has the following problems. The first problem is that since the dark correction circuit and the shading correction circuit have different configurations, they must be manufactured separately, which is troublesome and costly. The second problem is that the shading correction circuit must include a divider, but a large number of transistors are required to form the divider. An object of the present invention is to solve the above problems.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, in a semiconductor integrated circuit for correcting an image signal of the present invention, a line memory for storing a reference value for correction, a subtracter for subtracting the reference value from input data, and an output of the subtractor for a select signal. LOG conversion or reverse L
It was decided to have a LOG / inverse LOG conversion circuit for OG conversion.

[Work]

Since the dark correction circuit and the shading correction circuit, which are semiconductor integrated circuits for image signal correction, have exactly the same hardware configuration, it is possible to reduce the manufacturing labor and cost. Become. Further, since the image signal correcting semiconductor integrated circuit does not include a divider, the number of transistors is reduced.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a semiconductor integrated circuit for image signal correction according to the present invention. Reference numerals correspond to those in FIG. 5, 31 is a LOG / inverse LOG conversion circuit, 32 is a subtractor, 33 is a LOG / inverse LOG conversion circuit, 34 is a select signal input terminal, and 35 is an inverter. The LOG / inverse LOG conversion circuit can be used as both a LOG conversion circuit and an inverse LOG conversion circuit, and its switching is performed by a select signal. The LOG conversion circuit is a circuit that converts an input into a LOG value. FIG. 2 is a diagram showing LOG conversion, in which the horizontal axis represents input and the vertical axis represents output. For example, when "7" is entered, "Log
7 ”is output. The inverse LOG conversion circuit is a circuit that converts an input LOG value into a value without LOG. FIG. 3 is a diagram showing inverse LOG conversion, in which the horizontal axis represents input and the vertical axis represents output. For example, "Log7"
When is input, "7" is output. In the present invention, the dark correction circuit 5 and the shading correction circuit 6 have exactly the same hardware configuration. However, in the dark correction circuit 5, the LOG / inverse LOG conversion circuit 31 works as a LOG conversion circuit, and in the shading correction circuit 6, LOG / inverse L
The only difference is that the OG conversion circuit 33 is operated as an inverse LOG conversion circuit. Next, the operation will be described. The black reference data Bi is stored in the line memory 13 as in the conventional case. This is used as a reference value for dark correction. Next, as in the conventional case, the output of the image sensor 3 when the image 1 is the white reference plane is passed through the AD conversion circuit 4 of FIG. 4 to the dark correction circuit 5, that is, the data input terminal 8 of FIG.
To enter. The white reference data Wi is used as the difference, and the subtracter 11 subtracts the difference from the black reference data Bi stored in the line memory 13.
Take Wi-Bi. This difference is LOG in the LOG / inverse LOG conversion circuit 31.
Convert to get log (Wi-Bi). This is sent to the shading correction circuit 6 and stored in the line memory 23. This is used as a reference value for shading correction. The image 1 is set as the image to be read, the light source 2 is turned on, and the image data to the data input terminal 8 when read by the image sensor 3 is Vi. Then, in the subtractor 11, the difference Vi−Bi between Vi and the black reference data Bi is obtained and dark correction is performed, and further LOG conversion is performed by the LOG / inverse LOG conversion circuit 31 to obtain log (Vi−Bi). To be done. In the shading correction circuit 6, log (V
i-Bi) and the log (Wi-
Bi) is taken. log (Vi-Bi) -log (Wi-Bi)
That is, Is. The above result obtained by the subtracter 32 is the LOG / inverse LOG conversion circuit 33.
Reverse LOG conversion with Becomes As a result, the same shading-corrected image data as the conventional one is obtained. The inverter 35 is connected to the LO signal from the select signal input terminal 34.
When the select signal that causes the G / reverse LOG conversion circuit 31 to function as a LOG conversion circuit is input, that signal is used to perform LOG / reverse LOG.
It is inserted to create a select signal that causes the conversion circuit 33 to function as an inverse LOG conversion circuit. Dark correction circuit 5 and shading correction circuit 6 of the present invention
Since the hardware configurations are the same, it means that the same semiconductor integrated circuit can be used in time, which is less labor and cost than the conventional different circuits.

【The invention's effect】

As described above, the semiconductor integrated circuit for image signal correction of the present invention has the following effects. The dark correction circuit and the shading correction circuit, which are semiconductor integrated circuits for image signal correction, have exactly the same hardware configuration, so that the manufacturing labor is reduced and the cost can be reduced. Since the image signal correcting semiconductor integrated circuit does not include a divider, the number of transistors is reduced.

[Brief description of drawings]

1 ... Semiconductor integrated circuit for image signal correction of the present invention FIG. 2 ... Diagram showing LOG conversion FIG. 3 ... Diagram showing inverse LOG conversion FIG. 4 ... Image reading device FIG. 5 ... Conventional image signal correction Semiconductor integrated circuit FIG. 6 is a diagram for explaining dark correction. In the figure, 1 is an image, 2 is a light source, 3 is an image sensor, 4 is an AD conversion circuit, 5 is a dark correction circuit, 6 is a shading correction circuit, and 7 is an output. Terminal, 8 is a data input terminal, 9 is a clock input terminal, 10 is a D flip-flop,
11 is a subtractor, 12 is a D flip-flop, 13 is a line memory, 14 is a timing controller, 15 is a start signal line, 16 is a write command signal line, 17 is an address signal line, 18
Is a write enable signal line, 19 is an output data enable signal line, 20 is a D flip-flop, 21 is a divider, 22 is D
Flip-flop, 23 line memory, 24 timing controller, 25 start signal line, 26 write command signal line, 27 address signal line, 28 write enable signal line, 29 output data enable signal line, 31 log・ Reverse L
OG conversion circuit, 32 subtractor, 33 LOG / inverse LOG conversion circuit, 34
Is a select signal input terminal, and 35 is an inverter.

Claims (1)

[Claims] 1. A line memory for storing a reference value for correction,
A semiconductor for image signal correction, comprising a subtracter for subtracting the reference value from input data, and a LOG / inverse LOG conversion circuit for LOG conversion or inverse LOG conversion of the output of the subtractor according to an instruction of a select signal. Integrated circuit.