JPS6273869A - Picture reader - Google Patents

Abstract

PURPOSE:To attain complete shading correction by providing a dark current correction means correcting an output distribution in the line direction by a dark current of a line sensor into the line direction of the line sensor and a means applying shading correction as to a line sensor read signal after the correction. CONSTITUTION:An output lamp signal of a central control circuit 7 is set to light a light source 23. In this case, the circuit 7 outputs a write signal to a light level storage circuit 8 for one horizontal synchronizing period and stores a read signal outputted from the 1st correction processing section 10 into the light level storage circuit 8 by one line. A CCD line sensor 1 is not scanned ad the shading data by main scanning one line is stored in the light level storage circuit 8 to read a white correction plate 22. The 2nd correction processing section 11 applies division to a picture read data being an output of the 1st correction processing section 10 by the output of the light level storage circuit 8 thereby correcting the shading. Thus, proper shading correction over the one line direction of the line sensor is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to an image reading apparatus such as a facsimile, a digital copying machine, and a scanner reader that performs shading correction iE.

[Prior Art] Conventionally, in an image reading device using a solid-state image sensor such as a CCD as an image reading sensor, a white correction plate or the like is used.
From the read output, we have compensated for shading caused by optical systems such as light sources and lenses, and shading caused by uneven sensitivity of sensors such as CCDs.

Furthermore, when analog output from a sensor is A/D converted, the gain of the analog output has been automatically adjusted.

Furthermore, adjustment of the standard voltage when amplifying the analog output of the sensor has also been carried out.

[Problems to be Solved by the Invention] However, a dark current flows through the CCD sensor, and as a result, even when there is no light incident on the CCD, an output is output from the CCJ itself. Since the temperature tends to increase near the manual line of the clock due to the temperature, it was not possible to completely compensate for the shading by the above-mentioned adjustment.

[Means for solving the problem 1] The present invention compensates for the output due to the dark current of the CCD sensor.
The purpose of this is to obtain an image reading device that can read an ideal image by performing F. For this purpose, a current correction means is provided that corrects the output distribution in the line direction due to the dark current of the line sensor in the line direction of the line sensor. and shading correction is performed on the line sensor read signal after correction by the 11't'ifi style correction means.
It can be compared to the L stage.

1 Example 1 The present invention will now be described in detail with reference to the drawings.

FIG. 1 is a circuit block diagram of an embodiment of the present invention. In FIG. 1, l is a CCD line sensor for image reading, and 2 is the voltage output level of the CCD line sensor l.
:Level shift circuit for shifting downward, 4 is CC[
l A circuit that maintains the lowest level of the output of line sensor l;
5 is a circuit for detecting the maximum output level of the output of the level shift circuit 2, and 3 is a circuit for appropriately amplifying the image signal output from the level shift circuit 2.

The output of the maximum level detection circuit 5 is disconnected in the central control circuit 7. 6 is a circuit for A/D converting the analog output of the amplifier 3; 8 and 9 are digital outputs of the A/rl fL converter 6; a bright level and a dark level for storing the output of the first auxiliary iE processing section IO; Memory circuit, lO and I
I is a first and second correction circuit for image data, and 12 is an address counter that generates an address of the memory circuits 8 and 9.

In such a configuration, first, the light incident on the CCD line sensor l is inputted to the lowest level holding circuit 4.

At this time, as shown in FIG. 3, the white supplementary iF&22 attached to F of the document table 21 is not irradiated by the light source 23, and the lamp of the light source is turned off. This operation is performed by turning off the output Lamp signal of the central control circuit 7.
The light source 23 is turned on by the output La input ρ signal of the central control circuit 7.
lights up.

Thereby, the output of the CCD line sensor 1 receives a voltage shift according to the output of the lowest level holding circuit 4 by the level shift circuit 2. This allows the number '(r~fi-
Among the CCD line sensor outputs made up of T- sensors, the level shift circuit 2 obtains an output that is set to the minimum voltage reference 0. The output of this level shift circuit 2 is sent to an amplifier 3. The signal is input to the maximum level detection circuit 5. The maximum level detected by the maximum level detection circuit 5 is input to the central control circuit 7, where the amplification factor is determined, the determined amplification factor is output to the amplifier 3, and the level shift circuit is activated in the amplifier 3 based on this amplification factor. The output of 2 is amplified.

The signal amplified by the amplifier 3 is sent to the A/D converter 6.
,) /, to be converted into. The output of the A/mouth converter 6 is input to a dark level storage circuit 9 and a first correction processing section 10.

Then, the central control circuit 7 turns off the output Lamp signal and turns off the light source 23. Further, the central control circuit 7 outputs a prediction signal to the dark level storage circuit 9 during the first water cycle. As a result, the dark level for the signal line when the light source 23 is turned off is stored from the ^/Df converter 6 into the dark level storage circuit 9.

The image reading output of the A/D converter 6 is corrected by calculating the output of the dark level storage circuit 9 in the first correction processing section 10. This corrects the variation in dark current corresponding to the reading l life of the main scanning of the CCD line sensor l. Note that the address counter 12 has a water synchronization signal H3YN.
C and the image transfer lock CLK are input, the address value is cleared for each wood synchronization signal, and the number of image transfer locks is counted, so that the corresponding bright level storage circuit 8. Indicates the storage location of the memory in the dark level storage circuit 9.

Next, the output Lap signal of the central control circuit 7 is turned on, and the light source 23 is turned on. At this time, the central control circuit 7 outputs a write signal to the bright level storage circuit 8 during the horizontal synchronization period, and stores one line of the read signal output from the first correction processing unit IO in the II+ level storage circuit 8. . At this time, the CCD line sensor 1 does not scan, and the white supplementary + E plate 2
2, the bright level storage circuit 8 stores shading data for )S run 1'f:I life.

In the second correction processing section 11, the first correction processing? Shading M rF is performed by IS, which divides the image reading data output from l110 by the output from the Lebel memory circuit 8.

Also, the output of the IIFI level storage circuit 9 is sent to the comparator 1.
3 and is compared with a threshold output from the central control circuit 7 to the comparator 13, and the comparison result is input to the central control circuit 7. If the output of the dark level memory circuit 9 exceeds the rice planting level, it is possible that the dark current has increased due to heat generation in part or all of the CCD line sensor. A warning message will be displayed on the display, etc.

Regarding the embodiment I, the operating principle of the present invention will be explained below.

The dark current characteristics of the CCD line sensor 1 vary greatly depending on the environmental temperature, and the dark commutation increases rapidly when the temperature becomes high. In addition, in the CCD line sensor try> inner m, the closer to the clock supply side of the claw 2 line, the greater the heat generation, and the dark? The If current also increases.For this reason, as shown in Figure 2, the lowest value of the dark current is first set to the reference value, and then the C
Shift the output voltage of the CD line sensor. That is, FIG. 2 shows this output voltage as a sum. In Figure 2, the vertical axis is the voltage level.

The horizontal axis is a read image of one CCD line in the main scanning direction.

In addition, the output of the CCCC line sensor force read from the white correction plate 22 is suitably amplified and is C (this is the output of the amplifier 3), and the dark current component A is subtracted and corrected in the first auxiliary processing unit IO. By.

Only shading component B can be obtained.

Using this as shading data, the reading output of the CCD line sensor is corrected by division. For example, if a white supplementary iE board is read and supplemented, a uniform output level is obtained for one line of the CCD line sensor as shown in E. °1t can be done. If I don't do Denma Auxiliary +E.

Light incident on the CCD line sensor 04. -proportional to 1. However, for the same incident light V, for the output l life of the CCD line sensor,
It is not possible to obtain the same level of output.

[Effects of the Invention] As described in 1-1, according to the present invention, the output distribution in the line direction due to the dark current of the line sensor is compensated along the line of the line sensor, and the shading is performed after the main m correction. By performing the correction, one of the line sensors
i11 throughout the line direction! + [Shading correction can be performed. Furthermore, if the dark current increases abnormally due to the generation of M, etc., the system can issue a warning, thereby informing the need for maintenance.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an embodiment of the present invention; Fig. 2 is a diagram showing the image level 0 in each processing section of unreleased 1!1; Fig. 3 is a 0?i width scanner reader. 1... CCD line sensor. 2... Level shift circuit. 3... Amplifier. 4... Minimum level holding circuit. 5... Maximum level detection circuit. 6... A/D converter, 7... Central control circuit, 8... Bright level storage circuit, 9... Dark level storage circuit, lO... 1st complement+F processing section, I+... 2nd correction Processing unit, 12... Address counter, 13... Comparator.

Claims (1)

[Scope of Claims] 1) Dark current correction means for correcting the output distribution in the line direction due to the dark current of the line sensor in the line direction of the line sensor, and shading for the line sensor read signal after correction by the dark current correction means. An image reading device comprising: means for performing correction. 2) The dark current correction means includes a shift means for shifting the output level of the line sensor so that the lowest value of the dark current output of the line sensor becomes a reference voltage of an amplifier of the line sensor output, and a voltage obtained from the shift means. A storage means for storing the dark current output voltage of the line sensor for one line of the line sensor, and when reading an image by the line sensor,
2. The image reading device according to claim 1, further comprising means for outputting a value obtained by subtracting a dark current output value at a corresponding position from a line sensor output as a dark current correction value.