JPS58106956A - Picture reader - Google Patents

Abstract

PURPOSE:To compensate the variance of the sensitivity due to a change of the quantity of light or the like, by storing a read picture signal outputted from an image pickup element and compensating the signal level on a basis of stored contents to give a uniform lightness to a pressing face of an input original along the scanning direction of the image pickup element. CONSTITUTION:An original 1 is guided by rollers 2 and is allowed to pass between a pressing plate 4 and a target glass 5 in a prescribed speed, and an original pressing face 4a of the plate 4 is illuminated uniformly by a light source 3 such as a fluorescent lamp. A detection signal DS is generated from an original sensor 8 before the original 1 reaches a scanning and reading position P, and the picture signal of the original 1 is applied to an image pickup element 7 through an image pickup optical system 6 at the position P, and the picture signal is read by the element 7, and a read picture signal V0 from a DC reproducing circuit 10 is applied to a reading circuit. This signal V0 is stored in a storage device of the reading circuit, and the signal V0 is inputted and compensated in a compensating circuit on a basis of contents stored in the storage device, and thus, a uniform lightness is given to the pressing face 4a along the scanning direction of the image pickup element.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an m-reading device, and particularly to one that scans and reads image information of an input document using an image pickup device.

For example, in an image reading device of a facsimile machine.

It is a good idea to correct sensitivity variations due to the scanning position +11C when scanning an input document.
1111! It is essential to obtain an outstanding bond. This sensitivity variation is due to the sensitivity variation of a single image sensor such as a COD,
This is caused by a decrease in the amount of peripheral light in the imaging optical system, or by non-uniformity in the light amount distribution of a light source such as a fluorescent lamp. Therefore, in the past, variations in the read image signal level caused by these variation factors are fixedly stored in advance in a storage device such as a ROM, and the yV in the memory of this storage device is
It is provided that the read image signal level at the time of reading a document is corrected based on c. This certainly makes it possible to suppress variations in sensitivity to some extent. however.

The variation in which the correction effect appears in the conventional image reading device described above is mainly caused by variation in the image sensor or the optical system, etc., and the variation factor is a fixed factor that does not change depending on the surrounding environment or time. For example, when the ambient temperature of a fluorescent lamp used as a light source is 5@C and 30@C, the amount of light is 2 to 30 degrees Celsius.
It is known that the difference is as much as 3 times, and no correction effect could be obtained for such fluctuating variation factors.

This invention was made in view of the conventional problems as described above, and its purpose is to eliminate not only sensitivity variations due to fixed factors, but also sensitivity variations due to fluid factors that change depending on the surrounding environment or time. II that can effectively correct variations! ii*l! There is a device that provides a disassembly.

In order to achieve the above object, an image reading apparatus according to the present invention is an image reading apparatus that reads and scans image information of an input document using a camera.

A storage device that stores the g4j-1 signal level output from the image sensor, and storage contents 1111 of this IW device.
and a correction circuit for correcting the reading signal level based on the reading signal level based on 1:". Further, the holding surface of the input document is made to have uniform brightness at least along the scanning direction of the image pickup device.・Then, 1, when the input document is not in the jp:grabbing position of the image pickup device, the 1151! image capture 1 image signal level of the presser surface is set as the memory content of the memory narrow 1;
The present invention is characterized in that the contents stored in the storage device are updated each time a manuscript is input.

Hereinafter, a preferred actual winding machine of the present invention will be explained in detail based on the drawings.

In each figure, common or equivalent parts are given the same reference numerals.

Figure P1!1 shows an embodiment of the reading part of the image reading device according to the present invention. In the figure, first, the original 1 is guided by the rollers 2, 2, and is pressed against the presser plate 4 and the target glass 50.
5 to pass through the gap at a predetermined speed. Presser plate 4
The presser foot 4a is uniformly illuminated by a light source 3 such as a fluorescent lamp. At the original Sft taking position P, scanning is performed by the image sensor 7 in a direction orthogonal to the moving direction of the original 1. Recover ItP
A 4m element system 6 including a mirror 6a, a lens 6b, etc. is interposed between the image sensor 7 and the image sensor 7. Further, a sensor 8 for detecting input of the original document 1 is arranged at the hand @VC of the reading position P of the original document holder 4a. This sensor 8 issues a detection signal DB to the surface of the document 1 reaching the reading position PK. The output of the image sensor 7 passes through the device amplifier 9 and the DC reproducing circuit 10, and then is sent as a read image decoding Vo to a reading circuit, which will be described later. An example of a portion is shown. The circuit shown in the figure includes a variable attenuator 12. A/D converter 13. Peak hold circuit 14, memory by RAM K!
[15, It is composed of an address counter 16, etc., and receives the upper read image signal h, the detection signal D8, etc. as input signals. The variable attenuator 12 corresponds to the correction circuit described above. The A/D converter 13 converts the input (IN) to the gi level, as shown in a specific example in Fig. 3. Comparator group CPO-CP15 for comparison with different reference levels
, a resistor string RO to R16 for providing reference levels to the comparators @cpo to CP15, respectively, and a comparator group cp
Encoder 13 that creates 4-bit binary data DO~D3V based on comparison outputs CO~C15 of o~CP1B
Consists of 1st class. This A/D converter 13 obtains a reference level for its conversion.
) Class 24 reference levels Refl and Ref2 are used.

The first reference level Refx determines the upper limit 1' of the input level range of the A/D converter 13, and the reference level Rer2 of Mr. I 2 determines the lower limit 1'. Therefore, when the input level of the A/D converter 13 is directly above its upper limit i, "
Binary data of 1111'' is output, and when it is less than the lower limit it, binary data of 0000'' is output.

In the circuit shown in FIG. 2, the human power level range is set by the output level of the peak hold circuit 14. Now, here, the waveform chart I! shown in Figure 4 shows the operation of the cable* device shown in Figures 1 and 2. To explain with reference, first, the detection *'l'jDa from the document detection sensor 8
A reset signal R8 and an initial signal S are created based on the TIC. The reset signal R8 resets the peak hold circuit 14i. Further, the initial signal S is set for 5 hours so that it lasts until just before the document 1 reaches the threading position [P]. The logical product of this initial signal S and the main scanning clock HK of the image pickup device 7 becomes the signal WR set in the write state of the ML unit 15. On the other hand, the read image signal gVo is input to the variable attenuator 12. The output v1 of this attenuator 12 is given to each input of the A/D converter 13 and the peak hold circuit 1114, respectively. The output data v2 of the A/D converter 13 becomes the write data of the storage device 15. At this time, the memory device f15 is stored in the mood element 7.
The address is designated by the address counter 16, which is incremented by the main scanning clock HKK which is synchronized with the scanning of the main scanning clock HKK, and reset by the sub-scanning clock VKK, so that the memory 1jll15 stores the read image signal Vo Y quantized image. Data 9 is stored in correspondence with the scanning position of the image pickup device 7. At this time, the variable attenuator 12 is fixed at a state WAWc in which the level control amount, that is, the attenuation amount is the minimum from the initial signal SK. Storage device 15 from this K
For original 5lf) v7, take the original presser m4m1) 11!
s drawing signal level is stored. Therefore, the pressing surface 4
111C If uniform brightness is maintained at least along the scanning direction of the image sensor 7, information regarding sensitivity variations will be written in the storage device 15. This writing only needs to be performed during the sub-scanning period, but in this embodiment, as shown in FIG. 4, it is performed three times, and only the variation information in the last set meal period is recorded. ! It remains as the memory content of the device 15. The writing of such variation information is repeated every time the original $1 is input for one page. Therefore, the latest variation information is always stored in the storage device 15 each time the document 1 is input.

After the variation information is written in the storage device 15 as described above, when the document l reaches the reading device P and the scanning reading is started, the variable attenuator 12 is changed to the storage device 15. Storage data D read from
1, thereby correcting the level of the read image signal Vo in accordance with the scanning position. The output vl of the attenuator 12 is quantized by the A/D converter 13, and the quantized output v2 is derived as a sensitivity-corrected one-channel signal. The variable attenuator 12 is the fifth
As an example is shown in the figure, a voltage dividing circuit is made up of weighted resistances 8R, 4R, 2R, R and a reference resistance 8.58, and weighted resistances 8R, 4R.

2R and RK switches 80-8 each connected in parallel
It is composed of 3 and K. Each switch SO~S3
is controlled to open and close depending on the state of each bit of the stored data Dm.

By the way, in the embodiment, the first reference level (Refl)k of the A/D converter 13 is set to the output level of the peak hold circuit 14; The upper limit value can be automatically set to the high value of the background level of the document 1. Therefore-A
The upper limit of the input level range of the /D converter 13 is always the optimum level for reading the original s1.

FIG. 6 shows a more preferred embodiment of the present invention. *To explain only the differences from the above-mentioned embodiments, here, the second reference level Ref2 f peak hold circuit of the A/O conversion 413 before reading the original is explained. It is obtained by dividing the 14 output levels. For this reason, vc,
A voltage dividing circuit 17 that divides the voltage according to the voltage division ratio of the output level control amount of the peak hold circuit 14 and a switch circuit S for switching to the output side of the second reference level Ref2'1 voltage dividing circuit 17 before reading the document are provided. ing. Here, for example, the reference level Ref2 of @2, the output level of Y peak hold apposition 14, that is, the first reference level Refl
If the above partial pressure ratio is set to 50%, then 50%
The level becomes the lower limit value of the input level range of the A/D converter 13. That is, when the input level corresponds to 50% of the level, the VCA/D converter 13 outputs the minimum quantization of 1 ["oooo"". That is, 60% to 10
The level range of 0% corresponds to the quantum specific gravity range of ``oooo'' to ``1111''.

This essentially corresponds to increasing the resolution of the A/D converter 130 by kl bits, and thereby the accuracy of correction of sensitivity variations can be further improved. of course.

The above partial pressure ratio (output/input x 100%) is not limited to 50%; for example, the sensitivity variation is 25% over the years.
If it is confirmed that the ratio is within 75%, the partial pressure ratio can be set to 75%, and the resolution of the MU/D converter 130 in this case can be substantially improved by 2 bits. The above partial pressure ratio (output/input x 1oO%) is (100-K)% or less, and The attenuation amount of the variable attenuator 12 is set to be as large as possible, and the range of change in the amount of attenuation of the variable attenuator 12 is appropriately selected accordingly. This makes it possible to perform highly accurate correction even with an A/D converter with a small number of bits.

As described above, in the image reading device according to the present invention, it is possible to effectively correct not only sensitivity variations due to fixed factors, but also sensitivity variations due to R dynamic factors such as changes in the light amount of a light source. .

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the reading section of the 11-dimensional wILIIIL device according to the present invention, FIG. 2 is a circuit diagram showing an embodiment of the reading circuit section, and FIG. FIG. 4 is a waveform chart showing an example of the operation of the reading device shown in FIG. 1 and FIG. 2, FIG. 5 is a circuit diagram showing a partial section of FIG. 2, and FIG. FIG. 2 is a circuit diagram showing an embodiment of the present invention. 1... Original 2... Roller 3... Light source 4...
- Pressing plate 4a...Original holding surface 5...Darget glass 6...Image source material 7...Pixel sensor 8...
Original sensor 9... Front amplifier 10... DC regeneration circuit 12... Variable attenuator 13... A/
D Asakusa 14...Peak hold circuit 15...
・Note 1! Device 16...Address counter 17...
・Voltage dividing circuit Vo... Reading own signal vl... Attenuator output (1-Doushi) v2... Doji-ized image 11 signal D8... Original detection signal P... Scanning reading position Its Applicant's agent Kiyoshi Torii 1 Figure 1 Figure 2 ef2 7',, 5

Claims (1)

[Scope of Claims] An image** weir device that scans and reads j flaw information on an input document using an image sensor (including a storage device that stores the removal m* signal level output from the image sensor; and a correction circuit that corrects the tILIIL image signal level based on the stored content of the storage device, and a correction circuit that corrects the tILIIL image signal level based on the stored content of the storage device, and a correction circuit that has a small (and uniform llK along the scanning direction of the image pickup device) on the holding surface of the input document. Furthermore, the I!composition image signal level of the presser surface when the input document is not at the scanning reading position of the image pickup device is set as the memory content of the storage device. An image reading device that allows content to be updated.