JPH06105146A - Picture reader - Google Patents

Abstract

PURPOSE:To discriminate a lateral width of an original without provision of an exclusive discrimination means. CONSTITUTION:A gray color white reference reflection board 15 is read with a higher gain than a usual gain and resulting white reference data (e) are stored in a 1st storage means (RAM) 18. Then the white reference reflection board 15 are read by a usual gain to store gray reference data (i) to a 2nd storage means (RAM) 23. An original 16 is read, picture data (h) obtained by correcting the picture data (d) with a shading correction means (ROM) 19 are compared with the gray reference data (i) at a comparator 24. Since white background of an original 10 and the gray reference data (i) are compared, latch circuits 25, 26 latch a change point based on address information of each element of an image sensor 11 from an address generating means 20 to discriminate an original area thereby discriminating the lateral width of the original 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus used for image input such as a facsimile, an image scanner and a copying machine.

[0002]

2. Description of the Related Art Generally, an image reading apparatus uses a mechanical micro switch or an optical sensor as a means for discriminating the lateral width of a document to be read. FIG. 3 shows the configuration of the discriminating means using the optical sensor. 1 is a document holder, 2 is an A4 size document, 3 is B4
The size original 4 is an optical sensor for discriminating the lateral width of the original placed between the lateral widths of A4 size and B4 size.

In the conventional image reading apparatus having the above structure, when the B4 size original 3 is placed on the original placing table 1, the light emitted from the optical sensor 4 is reflected by the B4 size original 3. Then, the light is again received by the optical sensor 4, so that it is determined that the B4 size document 3 is placed on the document table 1. Further, when the A4 size document 2 is placed on the document table 1, the light emitted from the optical sensor 4 is not reflected by the A4 size document 2, so that the A4 size document 2 is placed on the document table 1. It is determined that it has been done.

[0004]

However, in the above-mentioned conventional image reading apparatus, in order to determine the lateral width of the document to be read, a dedicated determination means such as a mechanical micro switch or an optical sensor is used. In order to be able to discriminate the width of many originals, a plurality of discriminating means are required accordingly, and the arrangement of the discriminating means and the connection with the control unit are complicated. It was

The present invention solves such a conventional problem, and provides an image reading apparatus capable of discriminating the lateral width of a document without providing a dedicated discriminating means for discriminating the lateral width of the document. The purpose is to

[0006]

In order to achieve the above object, an image reading apparatus of the present invention comprises an image sensor for reading reflected light from an image, a gain control means for controlling an amplification gain of the image sensor, An analog-digital converter that digitizes the analog signal obtained from the image sensor, address generation means that generates an address corresponding to each element of the image sensor, and a gray white reference read by the image sensor with a higher gain than usual. First storage means for storing white reference data corresponding to
The second storage means for storing gray reference data obtained by reading the gray white reference with a normal gain, and the white reference data stored in the first storage means for the image data corresponding to the document read by the image sensor. Shading correction means for obtaining image data by performing shading correction,
Comparison means for comparing the shading-corrected image data with the gray reference data stored in the second storage means;
And means for discriminating the lateral width of the document from the output of the comparing means and the address information of each element of the image sensor from the address generating means.

[0007]

With the above arrangement, the image reading apparatus of the present invention reads the gray white reference with a higher gain than usual before reading the original image, so that white reference data can be obtained even if the white reference is gray. You can Then, by reading the white reference with a normal gain, gray reference data is obtained. By comparing the gray reference data with the white color of the background of the original, the existing area of the original can be detected, and by combining this with the address information of each element of the image sensor, the width of the original can be determined. You can

[0008]

FIG. 1 is a block diagram showing the arrangement of an image reading apparatus according to an embodiment of the present invention. In FIG. 1, 11
Is an image sensor for reading an image, 12 is an amplifier circuit for amplifying the analog signal a from the image sensor 11, 13
Is a clamp circuit for clamping the analog signal b from the amplifier circuit 12 at a black level, and 14 is an analog-to-digital conversion of the analog signal c from the clamp circuit 13 (hereinafter referred to as A /
It is abbreviated as D conversion. ) A / D converter. The image sensor 11 is read by the image sensor 11.
A gray white reference reflector having the same length as the reference numeral 16 is an original read by the image sensor 11. Reference numeral 17 is a switch that reads the white reference reflector 15 with a gain higher than usual and intermittently connects the white reference data e A / D converted, and 18 is a first switch that stores the white reference data e for each element of the image sensor 11. A random access memory (hereinafter abbreviated as RAM) 19 serving as a storage means is provided with shading correction data, which is given image data d obtained by reading the original 16 and A / D converted and white reference data e from the RAM 18 as addresses. A read only memory (hereinafter abbreviated as ROM) as a shading correction unit that outputs h, 20 is an address generator that receives a clock signal g and generates an address f corresponding to each element of the image sensor 11, and 21 is an address generator. A gain switching circuit for switching the gain of the amplifier circuit 12, and 22 is a normal white reference reflector 15 Switch for intermittently gray reference data i which has been read shading correction in-23 gray reference data i
RAM as a second storage means for storing each element of the image sensor 16, 24 is a comparator for comparing the shading correction data h with the gray reference data i, 25 is a shading correction by the comparison output j of the comparator 24. The latch circuit 26 latches the first address k at which the data h becomes whiter than the gray reference data i, and 26 indicates the last address l at which the shading correction data h becomes whiter than the gray reference data i by the comparison output j of the comparator 24. And a reference numeral 27 is a subtracter for subtracting the address k from the address 1 and outputting the document width data m. The amplification circuit 12 and the gain switching circuit 21 constitute a gain control means.

The operation of the image reading apparatus of this embodiment constructed as described above will be described below. First, the gain switching circuit 21 sets the gain of the amplifier circuit 12 higher than that in the case of reading a normal image. At this time, the switch 17 is closed. The image sensor 11 is
The light reflected by the gray white reference reflector 15 is received, and the analog signal a is sequentially output for each element of the image sensor 11. The analog signal a is amplified by the amplifier circuit 12, the amplified analog signal b is clamped at a black level by the clamp circuit 13, converted into white reference data e by the A / D converter 14, and the image sensor 1 of the RAM 18 is processed.
1 is stored in the address corresponding to each element. in this case,
Because the gain is set high, the gray white reference reflector 1
5 is the sufficiently white white reference data e.

Next, the gain switching circuit 21 sets the gain of the amplifier circuit 12 to the same level as when reading a normal image. At this time, the switch 17 is open and the switch 22 is closed. The image sensor 11 receives the light reflected by the gray white reference reflection plate 15, converts it into image data d via the amplifier circuit 12, the clamp circuit 13, and the A / D converter 14, and inputs it to the address of the ROM 19. It At the same time, the address generator 20 generates an address corresponding to the image data d, and the white reference data e from the RAM 18 is input to the address of the ROM 19. The ROM 19 stores the correction data obtained by the calculation of (127 × d ÷ e) when the data width is 7 bits, for example, and the gray reference data i subjected to the shading correction is output. It is stored in the address corresponding to each element of the sensor 11.
In this case, the gain is the same as when reading a normal image, so that the gray white reference reflector 15 has the gray reference data i.
Becomes

Next, when reading an actual original image, both the switch 17 and the switch 22 are open. The image sensor 11 receives the light reflected by the original 16 and outputs its analog signal a to the amplifier circuit 12, the clamp circuit 13, the A /
The image data d is converted via the D converter 14. ROM
The address 19 is the image data d of the original 16 and the RAM
White reference data e from 18 is input, and shading-corrected image data h is output. Shading correction image data h output from ROM 19 and RAM
The gray reference data i output from 23 is compared by the comparator 24. In the comparator 24, as shown in FIG. 2, when the signal level of the shading correction image data h is higher than the signal level of the gray reference data i, the document exists "1".
Is output, and if it is smaller, "0" indicating no document is output. The latch circuits 25 and 26 latch the address k at which the document starts and the address l at which the document ends based on the comparison output j of the comparator 24, and the subtractor 27 determines the address l.
The original width data m is output by subtracting the address k from.

As described above, in the above embodiment, the gain when first reading the gray white reference reflector 15 is set higher than the gain when reading the image to obtain the white reference data e, and then the white reference reflection e. Since the gray reference data i is obtained by reading the plate 15 with a normal gain, the original can be detected by comparing the gray reference data i with the white color of the background of the original. It is possible to determine the width of the document by combining the address information of

In this embodiment, since the gray white reference plate is used, the method of switching the gain of the amplifier circuit for amplifying the analog signal output of the image sensor between when the white reference is read and when the image is read has been described. However, it goes without saying that the same effect can be obtained by a method of switching the charge storage time of the image sensor.

[0014]

As is apparent from the above description, the image reading apparatus of the present invention is provided with an image sensor for reading reflected light from an image, a gain control means for controlling an amplification gain of the image sensor, and an image sensor. An analog-digital converter for digitizing an analog signal to be generated,
Address generation means for generating an address corresponding to each element of the image sensor; first storage means for storing white reference data corresponding to a gray white reference read by the image sensor with a gain higher than usual; Shading based on the white storage data stored in the first storage means and the second storage means for storing the gray reference data obtained by reading the white reference of the above with a normal gain, and the image data corresponding to the original read by the image sensor. Shading correction means for correcting and obtaining image data, comparison means for comparing the shading-corrected image data with the gray reference data stored in the second storage means, the output of the comparison means and the image from the address generation means Since it is provided with means for discriminating the width of the document from the address information of each element of the sensor, It is possible to determine the width of a document without providing the judging means.

[Brief description of drawings]

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

FIG. 2 is a graph for explaining the operation of the image reading apparatus according to the embodiment of the present invention.

FIG. 3 is a plan view of a document table for explaining a document width determination method in a conventional image reading apparatus.

[Explanation of symbols]

 11 Image Sensor 12 Amplifying Circuit 13 Clamping Circuit 14 A / D Converter 15 White Reference Reflector 16 Original 17 Switch 18 RAM (First Storage Means) 19 ROM (Shading Correcting Means) 20 Address Generator 21 Gain Switching Circuit 22 Switch 23 RAM (second storage means) 24 comparator 25 latch circuit 26 latch circuit 27 subtractor

Claims (1)

[Claims] 1. An image sensor for reading light reflected from an image, gain control means for controlling an amplification gain of the image sensor, an analog-digital converter for digitizing an analog signal obtained from the image sensor, and the image. Address generating means for generating an address corresponding to each element of the sensor; first storage means for storing white reference data corresponding to a gray white reference read by the image sensor with a gain higher than usual;
Second storage means for storing gray reference data obtained by reading the gray white reference at a normal gain, and white data for storing image data corresponding to the document read by the image sensor in the first storage means. Shading correction means for obtaining image data by performing shading correction with reference data, comparison means for comparing the shading-corrected image data with gray reference data stored in the second storage means, and output of the comparison means And an image reading device that determines the lateral width of the document based on the address information of each element of the image sensor from the address generating unit.