JPS6240875A - Picture reader - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image reading device, and more specifically, the present invention relates to an image reading device, and more specifically, a reference plate is read at a reading number of 1.411, and shading distortion is detected based on image information including t-shading distortion. The present invention relates to an image reading device that reads a document with supplementary information.

[Prior Art] This type of image reading device is widely used for facsimile machine images, and has adopted a circuit configuration as shown in FIG.

In FIG. 3, the symbol 1 indicates an image sensor such as a CCD sensor, into which light reflected from the reference plate and the document enters.

This image sensor 1 receives and collects reflected light from a reference plate and a predetermined area of the document due to movement of the document or the sensor itself, and after amplifying the obtained output with an amplifier 5,
It is input to the A/D converter 9 and comparator 17.

The output obtained by reading the reference plate by the image sensor 1 is converted into a digital signal representing shading distortion information by the A/D converter 9 and inputted to the memory 7. The data in the memory 7 can be converted back into analog data by the D/A converter 11.

The reference numeral -3 is a reading control section composed of a microcomputer or the like, which generates a control clock for the image sensor 1, an addressing signal for the memory 7, an R/W (read/write) signal, and the like.

- On the other hand, a changeover switch 19 is provided between the reading control section 3 and the image sensor l.

The first section 3 that controls the reading is equipped with a reference frequency oscillator or a Gronk generator using a combination of multiple frequency dividers.
3b, and by switching the selector switch 19, one of the clocks can be selected.

That is, the configuration is such that the bin rate for driving the image sensor 1 can be changed by switching the f, +1 changeover switch 19.

Next, the operation of the image reading device having the above structure will be explained.

First, when first reading the reading reference plate, the changeover switch 19 is switched to the low-speed clock 3a side, the image sensor 1 is driven at low speed 12, and the output of the image sensor 1 is connected to the amplifier 5 and transferred to the A/D converter. 9 performs A/D conversion and stores the image quality 1) of the reference plate in the memory 7 as a digital value.

On the other hand, when actually reading a document, the switching switch 19 is switched to drive the image sensor 1 at high speed with the high-speed clock 3b, and the read analog image signal is input to the comparator 17.

The comparator 1/17 reads out the analog voltage from the memory 7, converts it into an analog signal by the D/A converter 11, and divides the voltage by the resistor 13.15. The signal is sliced at the slice level for binarization to obtain a binarized signal.

If such a structure is adopted, a high-speed and low-speed clock switching switch will be provided between the image sensor and the readout control unit, and the readout control unit will generate two high-speed and low-speed clocks, resulting in high speed and expensive operation. High-speed reading is possible without using an A/D converter.

[Problem 1 to be solved by the invention 1. If the structure described above is adopted, the changeover switch 1
By switching 9, the drive clock of the COD image sensor can be set to a low speed only when storing the shading waveform, and the image sensor can be driven at a low speed. can do.

However, when a COD image sensor is driven at a low speed, the charge accumulation time of the image sensor increases, the amount of exposure to the CCD increases, and in some cases, the amount of exposure may be exceeded.
There are drawbacks such as the CCD becomes saturated and becomes unusable.

Note that the charge accumulation time T of COD requires the following condition: T21 bit period x total number of bits (1), so if the 1 bit period is made larger, the accumulation time T must also be made thicker. It turns out.

[F stage for solving the problem] In the present invention, in order to solve the problem described above, 1-Prior to reading a document by an image sensor, the image sensor is driven at a low speed to read a reading reference plate and perform shading. A structure is adopted in which the amount of exposure is reduced only when data for distortion correction is taken in and the reading reference plate is scanned.

[Function 1 1-If the structure described above is adopted, the COD is driven at a low speed, and even if the charge accumulation time becomes long, the exposure dose will be reduced and an accurate shading waveform will be obtained without overexposure. be able to.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

In the embodiment described below, the same or corresponding parts as in FIG. 3 are denoted by the same reference numerals, and the explanation thereof will be omitted.

[First Embodiment] FIG. 1 explains the first embodiment of the present invention.
In the figure, the reference numeral 21 indicates a document to be read, which is illuminated by a light source 23 .

A reading reference plate 31 is arranged on the 1- side of the original 21 .

The light from the light source 23 is irradiated onto the reading reference plate 31 or the original 21, and the reflected light is reflected by the mirror 25.
The light is input to the image sensor l via the condensing lens 29.

The reference numeral 27 indicates a driving section of the light source 23.

Next, the operation of this embodiment configured as follows-1- will be explained.

Before reading the original 21, a shape ink waveform for shape ink correction is captured. When storing this shading waveform, the reflected light from the reading reference plate 31 is reflected by the mirror 25.
．． c c of the image sensor l via the condensing lens 29
The amplified image signals 1 to 1 are guided to the A/D converter 9, and the digitized signals are stored in the memory 7.

At this time, since the signal 19a to the switch 19 is at a high level, the low-speed clock 3b is input to the CCD of the image sensor 1.

Further, the high-level signal is manually operated by the light source drive unit 27 to reduce the drive current and lower the brightness (light amount) of the light source 23.

As a result, the CCU of the image sensor l is driven at low speed.
, ccI), even if the charge accumulation time becomes longer, overexposure ψ does not occur, and an accurate shading waveform can be obtained.

If the data stored in the memory 7 is read in synchronization with the reading of the original 21 in this manner, the original reading signal from which shading distortion has been removed is binarized using the slice level that takes shading distortion into consideration. .

[Second Embodiment] 1- In the above-described embodiment, a method of reducing the amount of light from the light source 23 was adopted as a means for reducing the amount of exposure when storing the shading waveform, but the method is not limited to this method. You may also adopt the method shown in .

That is, what is indicated by the reference numeral 29a in FIG. 2 is a diaphragm mechanism that can adjust the amount of exposure to the condenser lens 29.

This aperture mechanism 29 is driven by a drive section 33, and when the input signal 19a to the face switch 19 is at a high level, the aperture mechanism 29 is apertured and the exposure amount can be reduced.

Even if such a structure is adopted, the exposure V to the image sensor-C7) CCD during shading waveform storage
Even if the COD is driven at a low speed by reducing the COD, overexposure will not occur and an accurate shading waveform can be obtained.

[Third Example] Note that the above 1. In the embodiment described above, the amount of light from the light source is reduced or an aperture is used to reduce the amount of light ej-t! However, if you want to configure it at the lowest cost, you can use a gray board with low reflectivity as the reading reference plate to avoid COD.
It is possible to reduce the amount of light input to the If such a structure is adopted, an accurate shading waveform can be obtained at the lowest cost.

In this example, the detected shading distortion causes 2
Shape ink distortion was removed by changing the slice level for value conversion, but this is not limited to the removal of shading distortion data by performing operations such as division and addition on the read image signal. Distortion removal may also be performed.

[Effect] As is clear from the explanation in -1- below, according to the present invention, since a structure is adopted that reduces the amount of exposure to the image sensor when taking in data for shading correction, the image sensor Even when driven at low speed, overexposure does not occur and accurate data for shading correction can be obtained.

[Brief explanation of drawings]

1 and 2 are block diagrams of the control circuit to explain the first and third embodiments of the present invention, and FIG. 3 is a block diagram of the control circuit to explain the conventional structure. l...Image sensor 3...Reading control section 5...Amplifier 7...Memory 9...A/
D converter 11... D/A converter 17... Comparator 19... Selection switch

Claims (1)

[Scope of Claims] 1) A case where, prior to reading a document by an image sensor, the image sensor is driven at low speed to read a reading reference plate to capture data for correcting shading distortion and to scan the reading reference plate. An image reading device characterized in that the exposure amount is reduced only when the exposure amount is reduced. 2) The image reading device according to claim 1, wherein the exposure amount is reduced by reducing the amount of light from a light source. 3) The image reading device according to claim 1, wherein the reduction of the exposure amount is performed by a diaphragm mechanism provided in the optical system.