JPS61137459A - Image reader - Google Patents

Abstract

PURPOSE:To prevent join parts of read images obtained by plural solid-state image sensors from becoming discontinuous in image density by providing an output level adjusting part which corrects output levels of output image signals of the solid-state image sensors after A/D conversion. CONSTITUTION:A selector 19 inputs difference 31 and data theta, which are outputted as a correcting signal 32 alternately in synchronism with a data switching signal 28. Namely, when an image reader is so constituted that a difference device 17 subtracts B latch data 30 from A latch data 29, the data thetais outputted with while image signals of solid-state image sensors are read out with the data switching signal 28 and the difference data 31 is outputted while image signals of solid-state image sensors 6 are read out with the data switching circuit 28. A black reference readout signal 23 has a low logical level, so the image signal of an A/D converter 9 is added to the correcting signal 32. Consequently, image signals having uniform levels are obtained from the two solid-state image sensors.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image reading device such as a facsimile or scanner device that scans a document, and particularly relates to an image reading device using a plurality of solid-state image sensors such as COD. .

Conventional technology When scanning and reading a document using a solid-state image sensor such as COD, multiple solid-state image sensors are mainly used for the purpose of securing a wide readable area or increasing the resolution of image information. Arranged at regular intervals in the scanning direction,
- There are systems in which the main scanning area is shared by each solid-state image sensor. (For example, JP-A-58-1168
65, JP-A-68-130670, etc.).

A conventional image reading device will be described below with reference to FIG.

A light source 1 uniformly illuminates a document 2, and the reflected light is applied to a solid-state image sensor 6.6, such as a COD, through condenser lenses 3 and 4, where it is photoelectrically converted into an image signal. By switching the changeover switch 7 in the sensor select circuit 1°, analog image signals are continuously taken out from the solid-state image sensors 5 and 6, and are amplified to an appropriate amplitude by the amplifier 8.

The system/Df converter 9 converts the analog image signal amplified by the amplifier 8 into a digital image signal while synchronizing with the sensor switching timing notified from the sensor select circuit 1o. Thereafter, the image signal is binarized by a digital signal processor 11, or subjected to processing such as gradation correction in an image reading device that outputs it in multiple gradations, and then output to an external device, memory, or the like. Here, solid-state image sensor 6.
6 are arranged so that their reading areas overlap,
-Sensor switching in main scanning is performed while image signals of the overlapping portion are being extracted. Therefore, the image information at the joint portion of the images will not be duplicated or missing.

Incidentally, the sub-scanning is performed by a sub-scanning feeding means (not shown) in a direction perpendicular to the plane of the paper in FIG.

Problems to be Solved by the Invention In such a conventional configuration, it is required that the amplifier 8 accurately adjusts the balance of each sensor output so that the image density at the joint portion of the read image does not become discontinuous. be done. This discontinuity in image density at the seam portion of the read image is caused by variations in the light-receiving sensitivity of each sensor, and is particularly noticeable in the case of minute-level image signals (black original). Therefore, as the number of gradations in image signal processing increases, high accuracy is required for the adjustment, and there is a drawback that accurate adjustment becomes extremely difficult with only the balance of the amplifier 8.

The present invention solves the above-mentioned problems of the prior art, and aims to provide an image reading device in which the image density at the joint portion of images read by a plurality of solid-state image sensors does not become discontinuous.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a system by providing an output level adjustment unit that corrects the output level of the output image signal of the solid-state image sensor after MU/D conversion. , which achieves the above objectives.

By providing the above output level adjustment section, the present invention compares the output levels of each solid-state image sensor after M/D conversion, and applies a correction signal according to the comparison result to the output image signal from each solid-state image sensor. It is calculated as follows.

Embodiment FIG. 1 is a block diagram showing an embodiment of an image reading apparatus of the present invention.

In FIG. 1, 1 is a light source, 2 is a document, 3 and 4 are condenser lenses, 6 and 6 are solid-state image sensors such as CGD, 7 is a changeover switch, 8 is an amplifier, 9 is a MU/D converter, and 10 1 is a sensor selection circuit, and 11 is a digital signal processor, which have the same structure as shown in FIG. 6, including the sub-scanning method. Reference numeral 12 denotes an output level adjustment unit that compares the output levels of the solid-state image sensors 6.6 and calculates a correction signal according to the comparison result with the output image signal from each solid-state image sensor 6.6. sensor 6
．． Since the detailed configuration differs depending on how the output level μ of No. 6 is compared, the detailed configuration will be described later.

Although not shown, a black reference with a constant density is installed on the document table on which the original 2 is set, and the black reference is scanned before the original 2 is scanned.

The configuration of the output level adjustment section 12 will be explained below.

FIG. 2 is a block diagram showing the configuration of the first embodiment of the output level adjustment section.

In FIG. 2, 13 is a selector circuit for selecting the output light of the digital image signal from the MU/D converter 9, and 14 is a solid-state image sensor 55.8 for calculating the average of the image signals over each main scan. An average circuit 16 is a latch circuit that latches the average value of image signals over a lifetime of scanning of the solid-state image sensor 5; 16 is a solid-state image sensor 6;
17 is a difference circuit that calculates the difference between the signals latched in the latch circuits 15 and 16; 18 is a difference circuit 17;
19 is a selector circuit, 20 is an adder, and 21 is a timing controller that generates each control signal in synchronization with the sensor select signal 22 and the black reference read signal 23. Note that FIG. 3 is a waveform diagram of the main part of FIG. 2.

The operation of the above configuration will be explained below with reference to FIG. Note that the processing up to the MU/D converter 9 is the same as the operation described using FIG. 6, so a description thereof will be omitted. First, when the black reference read signal 23 is logic "high" (FIG. 3 (b)), the selector circuit 13 passes the image signal from the hem/D converter 9 to the averaging circuit 14, so that the black reference read signal 23 is Logic 60-” (Figure 3 (b))
In this case, the image signal from the D/D converter 9 is passed to the adder 20. Now, assuming that the black reference read signal 23 is scanning the black reference at logic 6 high, the averaging circuit 14 receives a clear signal sent from the timing controller 21 every time the solid-state image sensor 6.6 switches to each other. Pulse 24 (Figure 3 (
c)) While clearing the calculation results, the solid-state image sensor 6.6 calculates the average of the image signals over the lifetime of each scan. The calculation results are transmitted from the timing controller 21 by the Muwotchi pulse 26 and the B latch pulse 25 (see Figure 3). The objects are respectively latched by latch circuits 16.

Mulatch data p2 latched in latch circuit 15 and 16
The difference between the data 3o (FIG. 3()) and H) is calculated by the subtractor 17.The above operation is repeated while the black reference read signal 23 is at logic 1 high. .

Next, when the black reference reading signal 23 becomes logic "low" and the document 2 is to be scanned, a latch pulse 27 is sent out from the timing controller 21 in synchronization with the change (FIG. 3 (c)).
As a result, the calculation result of the differentiator 17 is latched into the latch circuit 18. Since the black reference read signal changes once per negative scan, the output data of the latch circuit 18, that is, the difference data 31 sent from the latch circuit 18 (see FIG.
) remains unchanged during the scanning of 20 originals.

In the selector 19, an input terminal 33 having the same number of bits as the differential data 31 is grounded. That is, the difference data 31
and data 1θ” are input, and both inputs are corrected signal 3.
2 (FIG. 3)) and are output alternately in synchronization with the data switching signal 28 (FIG. 3 0). In other words, the difference unit 17 converts the shim latch data 29 to the B latch data 3.
If the configuration is such that 0 is subtracted, the data switching signal 28
is logic “high”, that is, outputs data 9θ” while reading the image signal of solid-state image sensor 6, and data switching signal 28 is logic “10-”, that is, outputs data 9θ” while reading the image signal of solid-state image sensor 6.
Difference data 31 is output while reading the image signal. Conversely, if the configuration is such that the difference device 17 subtracts the uneven latch data from the B latch data 30, the data switching signal 2
8 is logic 1 high", that is, the difference data 31 is output while reading the image signal of the solid-state image sensor 6, and the data switching signal 28 is logic 10-", that is, the data is output while reading the image signal of the solid-state image sensor 6. θ” is output.

Now, since the black reference read signal 23 is logic 10-'', the image signal from the M/D converter 9 is input to the adder 2o, where it is added to the correction signal 32. As a result,
Image signals with uniform output levels can be obtained between the two solid-state image sensors.

As described above, according to this embodiment, the output of the solid-state image sensor 6.6 is calculated by comparing the output of each solid-state image sensor 6.6 with the average of the image signals taken out from the solid-state image sensor 6.6 or 6 over a lifetime of scanning. Since accurate comparison can be performed without being affected by bit-to-bit variations, it is possible to realize an image reading device in which the density level is uniform not only in the vicinity of the joint portion of the read image but also in the entire area.

Next, a second embodiment of the output level adjustment section 12 will be described.

FIG. 4 is a block diagram of an output level adjustment section in a second embodiment of the present invention.

In FIG. 4, '19 is a selector circuit, 20 is an adder, 36 is a DC voltage power supply, 37 is a D/M converter that converts a digital signal into an analog signal, and 38 is a negative fMIIn.
't (CRT'sO image-e-2p, 39, 4
0 is a resistor. 34 is a dip switch for setting a correction signal to be added to the image signal taken out from the solid-state image sensor 6; 36 is a dip switch for setting a correction signal to be added to the image signal taken out from the solid-state image sensor 6; both dip switches are One terminal is grounded, and the other terminal is connected to the DC voltage power supply 36 and the selector 19 through resistors 39 and 40. Therefore, the correction signal can be set as a digital value by combining shorting and opening for each bit.

The operation of the above configuration will be explained below.

The selector 19 outputs the correction signal set to the dip switch 34 when the sensor select signal 22 sent from the sensor select circuit 10 is logic "high", and outputs the correction signal set to the dip switch 34 when the sensor select signal 22 is logic "low". Outputs the correction signal set to . Since the adder 2o adds the output signal of the selector 19 and the image signal from the M/D converter 9, the output image signal is converted into a D/D converter.
By converting the analog image signal into an analog image signal using the system converter 37 and reproducing it on the image monitor 3B, the image density of the joint portion of the read image can be checked with the human eye. Therefore, by adjusting the set values of the dip switches 34 and 35 while checking the continuity of image density on the image monitor 38, image signals with uniform output levels can be obtained between the two solid-state image sensors.

As described above, according to this embodiment, the correction signal to be added to the image signal is set by the DIP switch, and the setting is performed by referring to the reproduced image on the image monitor. An image reading device in which density does not become discontinuous can be realized.

Note that the image monitor 38 in this embodiment is not necessarily required for each image reading device according to the present invention, and only a few monitors are required at the production site. Further, in this embodiment, the black reference on the document table is not necessarily required, and the dip switches 34 and 35 may be set while scanning a black document with uniform density.

Further, as another embodiment of the present invention, the solid-state image sensor 6 can be
．． There is also a method of comparing the output levels of No. 6, and a method of comparing the output levels and then correcting them using correction data stored in the ROM.

Comparing the image sensors of each facet of the present invention as described above,
By calculating a correction signal according to the comparison result with the output image signal from each solid-state image sensor, not only will the image density at the joint between images read by the plurality of solid-state image sensors not become discontinuous; It is possible to realize an image reading device in which the image density level is uniform throughout the entire area of the read image.

[Brief explanation of the drawing]

Fig. 1 is a block wiring diagram of an image reading device according to an embodiment of the present invention, Fig. 2 is a block wiring diagram showing a first embodiment of an output level/v adjustment section of the same device, and Fig. 3 is an output level The main part timing chart of the adjustment section, Figure 4 shows the output level/
Block wiring diagram showing the second embodiment of the L' adjustment section, No. 6
The figure is a block diagram of a conventional image reading device. 6.6... Solid-state image sensor, 7...
・Selector switch, 9...Music/D converter, 10・
...Sensor selection circuit, 12...Output level adjustment section, 14...Additional averaging circuit, 17.
...Differentiator, 19...Buffer, 20.
...Adder, 34.35...Dip switch.

Claims (3)

[Claims] (1) A plurality of solid-state image sensors arranged at regular intervals in the main scanning direction, a changeover switch that continuously extracts image signals from the plurality of solid-state image sensors, and output image signals from the plurality of solid-state image sensors. an A/D converter that converts the image signals into digital signals; an output level adjustment unit that corrects the output level after A/D conversion of the output image signals of the plurality of solid-state image sensors; , an image reading device comprising a sensor selection circuit that notifies the output level adjustment section of switching timing of the solid-state image sensor. (2) The output level adjustment unit includes an output level comparison unit that calculates the difference in output levels of each solid-state image sensor, and an output level correction that determines a correction amount from the comparison result of the output level comparison unit and corrects the image signal. An image reading device according to claim 1, comprising: means. (3) The image reading device according to claim 1, wherein the output level adjustment section includes averaging means for calculating an average of image signals of a plurality of pixels.