JPH03131171A - Picture reader - Google Patents

Abstract

PURPOSE:To decrease the density fluctuation of a picture, especially the density fluctuation opposite to a luminous quantity detection position by providing a reference signal processing means processing a reference signal read from a storage means based on luminous quantity at two positions detected by a luminous quantity detection means when a read means reads an original picture. CONSTITUTION:A storage means B consists of a shading correction memory 4, stores a signal outputted from a read means A when the read means A reads a white reference board 10a. A luminous quantity detection means C consists of a photodetector 5 and detects a reflecting light from each of 2nd and 3rd white level reference boards 16b, 16c arranged at both sides at the outside of an original picture area in the subscanning direction. A reference signal processing means D consists a mean value circuit 18 and a multiplier/divider (picture signal correction device employing mean value) 10 and processes a reference signal read from the storage means B based on luminous quantity from two positions detected by a luminous quantity detection means C.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an image reading device.

[Conventional technology]

FIG. 9 is a plan view of the conventional white reference plate, and FIG. 10 is the same (a diagram showing the positional relationship between the conventional reference signal and the white reference plate).
FIG. 11 is a block diagram showing a configuration in which conventional optical detection is performed using an analog signal. In FIG. 9, 15 is an original glass, 16a is a white reference plate arranged in the main scanning direction, and 16b is a sub This is a white reference plate arranged on only one side in the scanning direction.

Next, the operation of the conventional image reading device is shown in FIGS. 9 to 11.
This will be explained using figures.

In conventional image reading apparatuses, in order to perform shading correction, a white reference plate arranged in the main scanning direction is read and stored before the start of document image reading, and the stored data is used as a reference signal.

However, if the fluctuation in the light amount of the light source is so large that it cannot be ignored, it is also necessary to correct the fluctuation in the light meter.

For this purpose, as shown in FIGS. 9 and 10, a second white reference plate is provided in the sub-scanning direction on one side outside the document image reading range, and the reflected light from the white reference plate is directed onto the photoelectric conversion element array. The reference signal is corrected based on the detected amount of light. Further, FIG. 11 shows a conventional example in which the light amount detection is performed using an analog signal. In Figure 11, 31, 33, 34 are analog switches, 35 is a sample and hold circuit, 1 is an amplifier, 2 is an A/D converter, 3 is a tri-state buffer, 4 is a memory, 7 is a latch, and 12 is a D/A It is a converter.

(Problems to be Solved by the Invention) As described above, in the conventional example, it is assumed that the light amount fluctuation ratio of the rod-shaped light source is the same over the entire longitudinal direction of the light source.

However, the actual amount of light does not vary at a constant rate due to temperature differences in the longitudinal direction of the light source. Therefore, although light amount fluctuation correction can be performed almost accurately in the vicinity of the pixel that is detecting the light amount, there is a problem in that the correction error increases at a position away from the light amount detection pixel.

This invention was made in order to solve the above-mentioned problems of the conventional method.The present invention was made in order to solve the problems of the conventional method as described above. The purpose is to reduce concentration fluctuations on the opposite side of the detection position.

[Means to solve the problem]

Therefore, in the present invention, there is provided a reading means for reading a white reference plate arranged in the main scanning direction and a document image, and a signal output from the reading means when the reading means reads the white standard plate. a storage means for storing, second and third white reference plates disposed in the sub-scanning direction on both sides outside the document image reading area, and detecting reflected light from the second and third white reference plates. 114. Reference signal processing that processes the reference signal read from the storage means based on the light amount at two locations detected by the light amount detection means when the original image is read by the light amount detection means and the reading means. The object of the present invention is to achieve the above object by means of an image reading device comprising means.

Further, - in the above invention, the reference signal processing means is
The above objective is achieved by using an image reading device which is a processing means that multiplies the average of the fluctuation ratios of the amounts of light detected by the first detection means.

Further, in the invention, the reference signal processing means attempts to achieve the above object by using an image reading device which is a processing means that multiplies the reference signal by a value that increases or decreases at a constant slope in the main scanning direction.

[Effect]

The image reading device according to the present invention reads the white reference plate arranged in the main scanning direction and the original image by the reading means, and when the reading means reads the white reference plate,
The storage means stores the signal output from the reading means, and the light amount detection means detects reflected light from each of second and third white reference plates arranged in the sub-scanning direction on both sides outside the document image area. When the document image is read by the glare removing means, the reference signal processing means processes the reference signal read from the storage means based on the light amounts at two locations detected by the light amount detection means.

Further, in the above invention, the reference signal processing means processes the reference signal by multiplying it by the average of the fluctuation ratio of the light amount detected by the light amount detection means.

Further, in the invention, the reference signal processing means processes the reference signal by multiplying it by a value that increases or decreases at a constant slope in the main scanning direction.

〔Example〕

Three examples of the present invention will be explained below based on the drawings.

FIG. 1 is a block diagram showing the configuration of a first embodiment of the present invention, FIG. 2 is a plan view showing a white reference plate of the first embodiment,
Fig. 3 is a diagram showing the positional relationship between the reference signal and the reference white plate in the first embodiment, Fig. 4 is a block diagram of the light amount detector in the first embodiment, and Fig. 5 is a diagram showing the positional relationship between the reference signal and the reference white plate in the first embodiment. A block diagram of another form of the light amount detector, FIG. 6 is a diagram showing the relationship between optical Ji fluctuation and DAC reproduction waveform, FIG. 6 A1 is the waveform stored in the memory 4 in FIG. 1, and FIG. The state in which the light intensity of the light source increases during the reading operation, Fig. 6B shows the conventional reproduction waveform in which the light intensity is detected only on one side, Fig. 6C shows the waveform processed by the DAC 12 in Fig. The amount of light at two locations shows the wavy texture after processing. FIG. 7 is a block diagram showing the structure of a second embodiment of the invention, and FIG. 8 is a block diagram showing the structure of a third embodiment of the invention.

Next, regarding the first embodiment of this invention, FIGS.
This will be explained using figures. In Figure 1 of the drawing, 1 is an amplifier for a video input signal, and 2 is an A/D converter (hereinafter referred to as A/D converter).
The video input signal amplified by the amplifier 1 is converted into a digital value by the ADC 2. 3 is a tri-state buffer, and 4 is a memory for storing a reference signal.

11 is a selector, and FFh is manually operated in the 8-person system. 12 is a D/A converter (hereinafter referred to as DAC),
In this embodiment, each has an 8-bit configuration, and the output of the DAC 12 is configured to be input to the reference voltage terminal of the ADC 2. Reference numeral A denotes a reading means for reading an image of a white reference plate (FIG. 2) and a document (not shown) arranged in the main scanning direction. Reference numeral B denotes a self-memory means, which is composed of a shading correction memory 4, and receives a signal output from the reading means A when reading the white reference plate 16a (FIG. 2) with the reading means A equipped with an image sensor. It is a means of remembering. C is a light amount detection means, and second and third light amount detection means are arranged in the sub-scanning direction on both sides outside the document image area.
This means detects the reflected light from each of the white reference plates 16b and 16c, and is composed of a light amount detector 5.

D is a reference signal processing means, which is composed of an average value circuit 6 and a multiplier/divider (image signal corrector using an average value) 10, and when reading an ff1 image with a reading means A (not shown), This is a means for processing the reference signal read out from the storage means B based on the amount of light at two locations detected by the light amount detection means C. In this case, the average of the fluctuation ratio of the light amount detected by the light amount detection means C is This is a means for multiplying or a means for multiplying by a value that increases or decreases at a constant slope in the main scanning direction (details will be described later). Next, the operation of the first embodiment will be explained with reference to FIGS. 1 to 6, focusing on the reference signal processing means.

FIG. 2 is a view of the V and document table of the image reading apparatus of the present invention viewed from above. In Figure 2 of the drawing, v, M base glass 1
A U-shaped white reference plate 16 is placed around the document reading range above 5.
a, 16b, and 16c are arranged. The fixed side is the home position, and the selector 11 is pressed just before reading the document.
(Fig. 1), the white reference plate 16a arranged in the main scanning direction is read by selecting 8 manual power for the output, and the successive signals are converted into digital values and stored in the memory 4 as reference signals. be done. The video waveform at this time is shown by the solid line in FIG. Further, signals read from the white reference plates 16b and 16c arranged in the sub-scanning direction at the same time are detected by a light amount detector 5 (FIG. 1), and the signal level of each signal is detected. FIG. 4 is a block diagram of the light amount detector 5. In the high section of the light detection section signal shown in FIG. 3, the white reference plate 16b
, 16c is detected, and the latch 22.2 is activated at the falling edge of the light amount detection section signal.
It is configured such that it is latched and outputted to each of the three. Further, as shown in FIG. 5, this circuit may detect an average value or a median value. An average value circuit 6 (FIG. 1) calculates the average of the outputs of the light amount detector 5, and latches it in a latch 9 as an initial value.

During document reading, the selector 11 selects the input in the document image reading period and the B input in the light amount detection period, and outputs the selected data to the DAC 12 . The tri-state buffer 3 disconnects the memory 4 from the ADC 2, and the reference number 43 stored in memory is read out from the memory 4 and latched into the latch 7.

Further, the light "1" from the light source is detected by the light amount detection circuit 5, the average value is calculated by the average value circuit 6, and the average value is latched by the latch 8. The outputs of each of the latches 7.8.9 are connected to the respective multiplier/divider 10
A, B, and C. Human power depends on human power. The multiplier/divider 10 is A*B/
The calculation result of C is output to the selector 11. The signal waveform reproduced by the DAC 12 is in the shape of the broken line in Fig.
It is input to the reference voltage terminal of No.2.

If the waveform A1 shown in FIG. 6 is the signal waveform stored in the memory 4, and the light intensity of the light source increases more on the right side than on the left side as shown in figure A on the left during the reading operation, then the DAC
The waveform processed and reproduced from 12 becomes as shown in FIG. C, and the error can be made smaller than that of the reproduced waveform diagram B in the conventional method of detecting the amount of light on only one side shown in FIG. Here, Figures B, C,
The waveform in Figure A is indicated by a broken line f in D for comparison.

Next, a second embodiment of the present invention will be described using FIG. 7.

FIG. 7 is a block diagram of a configuration in which light amount detection is performed using an analog signal.
1, the sample and hold circuit 35 detects the signal read from the white reference plate shown in FIG. 2 16b, and the analog switch 32 and sample hold circuit 36 detect the signal read from the white reference plate shown in FIG. 2 16c. The adder 37 obtains the added output.

Next, the operation of the second embodiment will be explained using FIG. 7.

First, just before reading the image, turn on the analog switch 33,
is turned off and the white reference plate 16a is stored in the reading memory 4.

When reading an image, turn off the analog switch 33 and turn off the analog switch 34.
ONL, the reference signal stored in the memory 4 is read out and reproduced by the DAC 12.

Incidentally, FIG. 11 shows a conventional example, and 40 is a double amplifier.

Next, a third embodiment of the present invention will be described using FIG. 8.

FIG. 8 shows a portion of the configuration of the first embodiment in which the reference signal was corrected using the average of the detected light amounts at two locations, which was detected using the white reference plates 16b and 16c, respectively. The white reference plate 16b determines the change in light amount for each pixel position based on the temporal variation ratio of the light amount, and the spatial change rate of the variation ratio.
Calculated for each pixel, assuming that it is constant between and 16c,
This is used to correct the reference signal.

The basic operation is the same as in the first embodiment, except that the data input manually to B and C of the multiplier/divider 10 is updated for each pixel.

The CPU 51 extracts the light amount bt from the light amount detector 5 when storing the reference signal in the memory 4, sets the value of the white reference plate 16b to X of the adder 52, and sets the value of the white reference plate 16b and 1.
A value is calculated by dividing the difference between the values of 6c by the number of pixels between 16b and 16c, and the value is set to Y. Further, during image reading, the output of the light amount detector 5 is read out for each line, and the same calculation as described above is performed and set in the adder 53. This adder 52.
53 adds and outputs Y for each pixel, with the initial value being X.

In this way, by manually updating the data input to B and C of the multiplier/divider 10 for each pixel, the D
The AC output waveform can better reproduce the distribution of the amount of light from the light source, as shown in the seventh diagram.

As described above, in each of the first, second, and third embodiments, the reference signal processing means is multiplied by the average of the fluctuation ratio of the light amount detected by the light amount detection means C, or the inclination is constant in the main scanning direction. By multiplying by a value that increases or decreases, the original image on the reading means A can be processed, and the amount of light from the light source can be well reproduced as described above.

〔Effect of the invention〕

As explained above, according to the present invention, fluctuations in image density, which are a problem in image reading devices using bar-shaped light sources with large fluctuations in the optical meter, such as fluorescent lamps, can be avoided, especially density fluctuations on the opposite side of the optical meter detection position. It has the effect of making it smaller.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a first embodiment of the present invention, FIG. 2 is a plan view showing a white reference plate of the first embodiment, and FIG.
The figure shows the positional relationship between the reference signal, the basic signal, and the reference white plate in the first embodiment, FIG. 4 is a block diagram of the light amount detector in the first embodiment, and FIG. 5 shows the light amount in the first embodiment. A block diagram of another form of the detector, FIG. 6 is a diagram showing the relationship between light amount fluctuation and DAC reproduction waveform, FIG. 6 A1 is a waveform stored in the memory 4 in FIG. 1, and FIG. 6 A is a reading operation. Figure 6B shows the conventional reproduction waveform in which the light intensity is detected only on one side, and Figure 6C shows the state in which the light intensity of the light source has increased. The sixth figure, which shows the waveform processed by the DAC 12, shows the waveform after processing at two light intensities. FIG. 7 is a block diagram showing the configuration of a second embodiment of the invention, FIG. 8 is a block diagram showing the configuration of a third embodiment of the invention, and FIG. 9 is a plan view of a conventional white reference plate. FIG. 10 is a diagram showing the positional relationship between a reference signal and a white reference plate in a conventional example, and FIG. 11 is a block diagram showing a configuration in which light amount detection in a conventional example is performed using an analog signal. A...Reading means B----Storing means C...Light amount detection means D...Reference signal processing means l...Amplifier 2... ---A/D converter 4 --- Memory 5 --- Light amount detector 6 --- Average value circuit 0 --- Multiplier/divider! ...Selector 2...D/A converter 5...W, stacking glass

Claims (3)

[Claims] (1) a reading means for reading a white reference plate arranged in the main scanning direction and a document image, and when the reading means reads the white standard plate,
storage means for storing the signal output from the reading means; second and third white reference plates arranged in the sub-scanning direction on both sides outside the document image reading area; and the second and third white reference plates. a light amount detection means for detecting reflected light from a reference plate; and when reading a document image by the reading means, the reference signal read from the storage means is based on the light amount at two locations detected by the light amount detection means. An image reading device comprising a reference signal processing means for processing. (2) The image reading apparatus according to claim 1, wherein the reference signal processing means is a processing means that multiplies an average of fluctuation ratios of light amounts detected by the light amount means. (3) The image reading apparatus according to claim 1, wherein the reference signal processing means is processing means for multiplying by a value that increases or decreases at a constant slope in the main scanning direction.