JPS60182855A - Picture reader - Google Patents

Abstract

PURPOSE:To correct shading distortion while eliminating the effect of fluctuation of luminous amount distribution of a light source by inputting simultaneously an optical signal from an original and a white reference board and processing the signal in parallel so as to simplify the circuit. CONSTITUTION:The reflected light from an original 10 and the white reference board 11 irradiated by the light from a reading light source 12 passes through separate paths 10a, 11a, is reflected on a mirror 13, the reflected light from the original 10 is collected to a linear image sensor 16 and the reflected light from the white reference board 11 is collected to a linear image sensor 15. The signal from both the linear image sensors 15, 16 is inputted to a comparator 21 via amplifiers 17, 18. Then it is possible to binary-code a picture signal at each position of the original scanning based on a slice level corresponding to shading distortion. No memory is required through the parallel processing in this way and no A/D, D/A converter is required resultingly.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an image reading device, and more specifically, to a method of reading a document by correcting shading distortion based on information obtained by reading a reference plate. This invention relates to an improved image reading device.

[Prior art]

Conventionally, the operation method of an image reading device has been as follows. First, information for shading distortion correction is stored in a memory by scanning a white reference plate. Next, the document is scanned, and at the same time, information on white reference plate scanning for shading distortion correction stored in the memory is extracted from the memory in correspondence with each point on the document. This makes it possible to binarize the image signal at each point of document scanning based on the slice level corresponding to shading distortion.

A circuit diagram of a conventional example of such an image reading υ method is shown in FIG. In the figure, the reference numeral 1 is a CCT (charge coupled device) linear image sensor, which converts an input optical signal into an electrical signal and can send it to the subsequent circuit. This linear image sensor 1 is constructed of a semiconductor, and is capable of extracting an optical signal applied in a -dimensional manner as a potential change multiple times continuously from one end. By scanning the entire document, all information in the document can be read. As shown in FIG. 1, this linear image sensor 1 is controlled by a reading control section 5 to amplify an electric signal from the image sensor 1 and output it to a signal line 2a or a signal line 2b. Signal line 2a is A/D (analog to digital)
It is connected to the converter 3 and serves as a signal path during the first scanning of the white reference plate. The signal line 2b is connected to the comparator 7, and serves as a signal path for the original during image reading.

The A/D converter 3 is a device that converts analog information into digital information.

The electrical signal sent from the signal line 2a is analog information that is continuous with respect to time, whereas the memory 6 can only store digital information. Therefore, by extracting the analog information from the signal line 2a at regular time intervals, it is converted into time-discontinuous digital information and sent to the memory 6.

The D/A (digital to analog) converter 4 is a device that converts digital information into analog information.

The digital information stored in the memory 6 is converted into continuous analog information with respect to time, and as a continuous potential change,
Comparator 7 passes through a voltage divider circuit consisting of resistors 8 and 9.
Continuing to. This path becomes a signal path for shading distortion correction during document reading. The memory 6 is under the control of the reading control unit 5, and when reading the white reference plate, A/l'
) When inputting information via converter 3 or reading a document
The information is outputted via the /A converter 4. The reading control unit 5 controls image reading, controls the linear image sensor 1, and performs A/A via the memory 6.
It controls the D converter 3 and the D/A converter 4, and also controls the signal lines 2a and 2b via them. A voltage dividing circuit composed of resistors 8 and 9 connects the D/A converter 4.
By raising and lowering the baseline of the signal of continuous potential fluctuations sent to the comparator 7, the magnitude relationship with the potential fluctuations from the other signal line 2b inputted to the comparator 7 is adjusted.

The comparator 7 determines the magnitude relationship between the potentials of the two signal lines -H input thereto, and outputs one of two predetermined potentials depending on the magnitude relationship. These two types of signals correspond to white and black in the original, and this is the meaning of the binarization by the comparator 1.

The conventional example is configured as described above, and operates as described below. First, when scanning a white reference plate, an optical signal due to reflected light from the white reference plate is input to the linear image sensor 1, and a thickened potential change is detected by the signal line 2.
a, the signal is input to the A/D converter 3, converted into a digital signal, and then stored in the memory 6. This process is under the control of the reading control section 5. Next, when scanning a document, an optical signal due to light reflected from the document is input to the linear image sensor 1, and an electric signal as a potential change is input to the amplifier 2, as in the above case. However, in this case, the output signals of the amplifiers 2 and υ are output to the signal line 2b and directly input to the comparator 7. At the same time as scanning this document, information obtained as a result of scanning the white reference plate is
In order to correct shading distortion, data is output from the memory 6 corresponding to each point on the document. This information is input to the Luhe converter 4 and converted into an analog signal, after which the baseline of potential fluctuation is adjusted by a voltage divider circuit made up of resistors 8 and 9, and input to the comparator 7. As a result, information from the white reference board at the same point as a certain point on the document is input to the comparator 7, and the information is compared with the white reference board by the comparator at the same time while scanning the document. It becomes possible to do this. This results in
It becomes possible to binarize the image signal at each point of document scanning based on the slice level corresponding to shading distortion.

As a result, in conventional image reading devices, A/i)
Disadvantages include the need for expensive equipment such as converters, D/A converters, and memory, and the complicated control system, which inevitably leads to complicated peripheral circuits and a significant increase in costs. was there. Furthermore, since monochrome fluorescent lamps are currently widely used as light sources for reading, the light intensity distribution tends to change over time. There was also a drawback that the amount of light was different when scanning a document and that shading distortion could not be adequately corrected.

〔the purpose〕

The present invention was made to improve the above-mentioned conventional drawbacks, and by simultaneously inputting the optical signals from the original and the white reference plate and processing them in parallel, it is possible to simplify the circuit and reduce costs. It is an object of the present invention to provide an image reading device configured to eliminate the influence of fluctuations in the light intensity distribution of a light source and to sufficiently correct shading distortion.

[Actual flow side]

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 2 explains one embodiment of the present invention, and shows reference numeral 1.
0 is the document to be read by the reading device, and 11 is the white reference plate.

Both are irradiated with light by a reading light source 12,
Those reflected lights each have separate paths 10a.

The direction of the light beam is changed by nine mirrors 13 through 11a and 11a. They are focused by the same lens 14 at different positions depending on their respective paths.

If the optical signal comes from the white reference plate through one path 113, the light is focused on the linear image sensor 15, and if it is the optical signal from the path 1081, that is, the document, the light is focused on the linear image sensor 16. Both near image sensors 15 and 16 are under the control of the reading control section 22, and convert optical signals into electrical signals as changes in potential. These are amplified by intensifiers 17 and 18, respectively, and the signal from the white reference plate, that is, the signal that has passed through amplifier 17, is input to a voltage divider circuit consisting of resistors 19 and 20, and then to a comparator. 21. The signal from the other original, that is, the signal that has passed through the amplifier 18, is 1,
The signal is directly input to the comparator 21 as it is.

The operation of this embodiment configured as above will be explained.

Optical signals input simultaneously and independently from the original and the white reference plate are converted into electrical signals by each linear image sensor. The signal from the white reference plate, which serves as a reference for shading distortion correction, is amplified, then subjected to baseline adjustment by a voltage dividing circuit, and input to the comparator 21 . On the other hand, the signal from the original is directly input to the comparator 21 after being amplified. The optical signals inputted simultaneously and independently in this way are inputted simultaneously and independently to the comparator 21 as electrical signals. In this way, it is possible to binarize the image signal at each point of document scanning based on the slice level corresponding to shading distortion.

In this way, by performing parallel processing, signals can be input from the original and the white reference board at the same time, and no memory is required. is also no longer necessary.

Since this embodiment is configured as described above, expensive A/D/D/A converters and memories are not required, and the circuit can be simplified, resulting in the effect of cost reduction and the light source. Since the influence of changes in the light amount distribution over time can be completely removed, it is possible to achieve the effect that shading distortion can be sufficiently corrected.

〔effect〕

As is clear from the above description, according to the present invention, effects such as cost reduction due to circuit simplification and shading distortion can be sufficiently corrected can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram explaining a conventional example, and FIG. 2 is a circuit diagram explaining the present invention in detail. 1... Linear image sensor 2... Amplifier 3...
・A/1) Converter 4...D/A converter 5...Reading control section 6 ・Memory 7...Comparator 8...Resistor 9...Resistor 1o...Original 11... White reference plate 12...Light source 13...Mirror 14...Lens 15...Linear image sensor 16...Linear image sensor 17...Amplifier 18...Amplifier 19...Resistor 20... resistance

Claims (1)

[Claims] An image reading device that corrects shading distortion based on the brightness of the reference plate and reads the original image has a linear image sensor for reading the reference plate and a linear image sensor for reading the original; Image reading characterized by processing the signals of the linear image sensor in parallel to convert the image signal of the linear image sensor for reading an original into 21-digit format using the shading distortion waveform obtained by the linear image sensor for reading the reference plate as a reference. Device.