JPS5814672A - Image reader - Google Patents

Abstract

PURPOSE:To compensate the reduction of the level of a picture signal which is caused by the deterioration of the illumination light volume of a reading light source, by reading a standard white surface simultaneously with an image surface with a reading element and setting the level at a constant value for the area corresponding to the white surface. CONSTITUTION:A light source 2 irradiates an original, and a reading element 1 gives the photoelectric conversion to the reflected light of an original irradiated by the light source 2. A standard white surface 3 is set on the scanning surface of the original. A digital control type variable attenuator 7 attenuates the output picture signal of the element 1. An extracting means extracts the reading picture signal of the surface 3 out of the output picture signal of the attenuator 7. A comparator 11 compares the output signal of the above-mentioned extracting means with a prescribed reference level signal. a counter 16 controls the degree of attenuation of the attenuator 7 based on the result of comparison of the comparator 11. Then the level is kept constant for the part corresponding to the surface 3 among the output signals of the attenuator 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image reading apparatus that corrects fluctuations and deterioration of the light amount of a reading light source and also displays a request for replacement of the light source.

In conventional image reading devices, the amount of light irradiated by a reading light source such as a fluorescent lamp deteriorates macroscopically over time. On the other hand, for a short time after the lamp is turned on, the amount of irradiated light increases with time. - If the amount of light irradiated by the reading light source changes in this way, the read signal will be distorted in the signal processing circuit, and even if an image is reproduced based on this read signal, it will be completely different from the original image. was.

The present invention has been made in view of the above-mentioned drawbacks. Firstly, it is possible to correct the influence of the reading signal due to fluctuations or deterioration of the illumination light amount of the reading light source, and secondly, it is also possible to display a request for replacement of the reading light source. An object of the present invention is to provide an image reading device that can perform the following operations.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 1 is a schematic block diagram of an image reading device showing an embodiment of the present invention. In FIG. 1, 1 is an optical reading element, and 2 is a fluorescent pair used as a light source. 3 is a standard white plate, and 4a and 4b are paper guide plates. A document (not shown) passes between a standard white plate 3 and paper guide plates 4a, 4b. 6 is a lens. Note that FIG. 2 is a diagram showing the positional relationship between the reading element 1 and the standard white plate 3, and the same members as in FIG. 1 are given the same symbols. In the figure, B indicates the maximum document width, and A indicates the reading scanning width of the reading element 1.

6 is an amplifier that amplifies the signal obtained by reading, 7 is a digitally controlled variable attenuator that applies light amount correction to the image signal obtained by the reading element 1, 8 is a signal processing circuit, and 9 is an output terminal.

1o is a gate circuit that extracts a portion necessary for light intensity correction control from the output signal of the variable attenuator 7; 11 is a gate circuit 1;
The output signal of o and the reference level signal d input from terminal 12
When the reference level signal d is smaller than the reference level signal d, the output signal e is set to the low level L, and when the reference level signal d is larger, the output signal e is set to the high level H. 13 is an input terminal for a clock pulse signal that is synchronized with each bit of the image signal output by the reading element 1; 14 is an input terminal for the gate signal a; 15 is an AND circuit; 16 is a counter circuit that controls the variable attenuator 7. It is. 17 is a replacement detection circuit for the fluorescent pair 2, and 18 is a replacement request display device for the fluorescent pair 2.

Regarding the operation of the image reading device having the above configuration, the third
This will be explained below using timing diagrams shown in FIGS.

First, the reading operation of this image reading device will be explained.
□The fluorescent lamp 2 illuminates a moving document (not shown) 1, and the lens 6 collects the reflected light from the surface of the document.The reading element 1 photoelectrically converts this light, so that it can be faithfully reproduced on the document. image signal can be obtained. This image signal is input to a signal processing circuit 8 via an amplifier 6 and a variable attenuator 7. This signal processing circuit 8 converts the image signal into a form suitable for a subsequent device, and outputs it from an output terminal 9 to the subsequent device.

By the way, as shown in FIG. 2, in the image signal output from the reading element 1, a signal obtained by reading the standard white plate 3 is added before and after a signal obtained by reading the document.

In this embodiment, the light amount of the fluorescent pair 2 is detected using the signal read from the standard white plate 3 included in this image signal, and the deterioration and fluctuation of this light amount is corrected.

Next, the light amount correction operation will be explained. FIG. 3A shows the timing of the image signal output from the reading element 1. That is, the image signal is output at the high level portion of the signal shown in FIG. 3A. At the output timing of this image signal, the control circuit (not shown) of this image reading device creates a gate signal a for extracting a part of the signal that is read from the standard white board and is included in the image signal. , is supplied to terminal 14. Since this gate signal a is supplied to the AND gate circuit 1°, only the standard signal C corresponding to the portion read from the standard white board out of the output of the variable attenuator 7 is displayed at the output of the gate circuit 10. be exposed.

This standard signal C is input to a comparator 11 and compared with a reference level signal d. When the reference level signal d is larger than the standard signal C, the comparator 11 sets its output, the comparison signal e, to a low level, and conversely, when the reference level signal d is smaller than the standard signal C, the comparison signal e is set to low level. It is output to the counter 16 as a high level.

On the other hand, the AND circuit 16 receives a clock pulse signal synchronized with each bit of the image signal input from the terminal 13, and a clock pulse signal synchronized with each bit of the image signal input from the terminal 13.
4, the output of the AND circuit 16 is input to the signal sum counter 16 as shown in FIG.

Each time a document (not shown) arrives, the counter 16
The count value is set to 0'', and only when the comparison signal e is at a low level, the clock pulse signal S output from the AND circuit 15 is counted, and this count value is output to the variable attenuator 7. On the other hand, the variable attenuator 7 changes its own attenuation amount according to the count value of the counter 16. In this embodiment, when the count value of the counter 16 is "O", the attenuation amount is minimized, and as the count value increases, the attenuation amount is minimized. , the amount of attenuation is increased in stages.

Therefore, assuming that the comparison signal e is always at a low level, the clock pulse signal is the counter 1 as shown in FIG.
6, the amount of attenuation of the variable attenuator 7 increases stepwise, so that the output signal of the variable attenuator 7, that is, the standard signal C, is also attenuated as shown in FIG.

However, if the light intensity of the fluorescent pair 2 is normal, the standard signal C becomes smaller than the reference level signal d during the process. When the standard signal C becomes smaller than the reference level signal d, the comparator 11
The comparison signal e outputted from is at a high level. Therefore, the counter 17 stops counting, and the standard signal C becomes a constant level as shown in FIG. 6C. In this way, the fluorescent pair 2
Even if the level of the image signal decreases due to deterioration in the amount of light, the output of the variable attenuator 7 can maintain the level of the image signal corresponding to standard white at a constant level. Therefore, since the image signal processing circuit 8 can always process image signals of the same level, distortion of the image signal is eliminated.

Although the above operation has been explained for one operation, this function does not stop until all of one sheet of original is read.

That is, the amount of light from the fluorescent pair 2 increases for a short time after the light is turned on. This is because the temperature inside the device increases. In this embodiment, fluctuations in the image signal level due to changes in the amount of light are also corrected. This operation will be explained below.

First, while one document is being read, the comparison signal e is at a high level, the count value of the counter 16 is stopped, and the amount of attenuation of the variable attenuator 7 is also fixed. At this time, when the amount of light from the fluorescent pair 2 increases, the level of the image signal output from the reading element 1 increases, and the output signal from the variable attenuator 7 also increases. As a result, as a matter of course, the level of the standard signal C output from the gate circuit 10 increases with each reading operation, and eventually the standard signal C becomes higher than the reference level signal. Then, the comparison signal e output from the comparator 11 becomes low level. Therefore, the counter 16 restarts counting and increases the attenuation amount of the variable attenuator 7. Then, when the standard signal C becomes smaller than the reference level signal d, the comparison signal e becomes high level, and the counter 1
Counting of 6 stops. Thereafter, by repeating the same operation, even if the light amount of the fluorescent pair 2 increases and the level of the image signal rises during the reading operation of one document, the output of the variable attenuator 7 will not produce the standard white color. Since the level of the image signal corresponding to the image signal can be kept constant, the signal processing circuit 8 can always process the image signal of the same level, and the image signal after processing will not be distorted. In addition, in this embodiment, when the standard signal is smaller than the reference level signal, the correction control operation is maintained, and the correction control operation is resumed only when the standard signal becomes larger than the reference level signal. Correction control can be performed.

In this embodiment, a request for replacement of the fluorescent pair 2 can also be displayed. The operation is shown below. Only when the attenuation amount of the variable attenuator 7 is minimized, the counter 16 sets the signal f output to the detection circuit 17 to a high level. At this time, if the comparison signal e of the comparator 11 is at a high level, the detection circuit 17 sets the output signal q to the display circuit 18 at a high level.

This causes the display circuit 18 to turn on, for example, a fluorescent replacement lamp. In other words, even when the variable attenuator 7 cannot correct a decrease in the image signal level due to the deterioration of the light intensity of the fluorescent pair 2, the fluorescent lamp replacement lamp can be displayed, and the reproduced image becomes dark due to insufficient light intensity of the fluorescent pair. It is possible to prevent problems such as digitization and inability to read text.

As is clear from the above description, according to the present invention, the reading element reads the standard white surface at the same time as the image surface, and by keeping the level of the portion corresponding to the white surface constant, the amount of illumination light from the reading light source can be reduced. It is possible to correct a decrease in the level of the image signal due to deterioration. Furthermore, by sequentially switching the attenuation amount of the variable attenuation means to a larger value when the output signal of the extraction means is smaller than the reference level signal, even if the illumination light intensity of the reading light source increases while reading one document, The resulting increase in the level of the image signal can be successively corrected.

Furthermore, since it is equipped with a detection means for detecting the replacement of the light source by obtaining the output from the control means and the comparison means, and a display means for indicating the replacement of the light source based on the output of the detection means, the amount of illumination light from the reading light source can be adjusted. If the image signal decline due to deterioration cannot be corrected, it is possible to indicate that the reading light source should be replaced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an image reading device according to an embodiment of the present invention, FIG. 2 is a positional relationship diagram between a reading element and a white plate, and FIG.
5 to 5 are timing diagrams of the main parts, respectively. 1-...Reading element, 2...Fluorescent lamp, 3
...White plate, 7...Variable attenuator, 8...
...Picture signal processing circuit, 10...Gate circuit, 11
...Comparator, 16...Counter circuit,
17...detection circuit, 18...display device. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 13 Country No. 411 (a)
(L(GF)
/b1115 Figure

Claims (1)

[Claims] (1) A light source for irradiating the original, a reading element that photoelectrically converts the light reflected from the original irradiated by the light source, a standard white surface placed on the original scanning surface, and attenuating the output image signal of the reading element. a digitally controlled variable attenuator, an extracting means for extracting a read image signal of the standard white surface from an output image signal of the digitally controlled variable attenuator, and an output signal of the extracting means and a predetermined reference level signal; and a control means for controlling the attenuation amount of the digitally controlled variable attenuator based on the comparison result of the comparing means, An image reading device characterized by maintaining a constant level of a portion corresponding to a white surface. (b)) In the image reading device according to claim 1, the control means for controlling the amount of attenuation of the digitally controlled variable attenuator controls the amount of attenuation when the output signal of the extraction means is smaller than the reference level signal. An image reading device characterized in that the image reading device switches in order from larger to larger. 0) In the image reading device according to claim 1 or 2, there is a detection means for detecting the replacement of the light source by obtaining the output from the control means and the comparison means, and a light source replacement display based on the output of the detection means. What is claimed is: 1. An image reading device comprising display means for performing.