JPH01296773A - Picture reader - Google Patents

Abstract

PURPOSE:To avoid the effect of flaw or dust on a reference white board by moving the reference white board and providing a comparator comparing a correction obtained at the preceding time and a correction quantity obtained at present. CONSTITUTION:The reference white board 11 is irradiated by a light source 12, its reflected light is collected by a lens 13, the light is photoelectric-converted into an electric signal by a photoelectric conversion element 14, amplified by an amplifier 15 to obtain a waveform 11. A point A of the waveform 1 represents the effect of dust or flaw on the reference white board 11. Then the reference white board 11 is moved in the direction of arrow and its output waveform 2 is obtained, the value is divided by a prescribed value R at a divider 16, its output waveform is subject to A/D conversion by an A/D converter 17, and the output of the A/D converter 17 and a value stored in a temporary storage element 18 corresponding to each photoelectric conversion element are compared by a comparator 19. When the output of the A/D converter 17 is larger, the value of A/D conversion is again stored to a location corresponding to the photoelectric conversion element. Thus, the correction quantity is as shown in figure (b) and the effect of flaw is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an image reading device that reads an image of a document as an electrical signal using a photoelectric conversion element (for example, COD, etc.). This paper proposes a means for correcting variations in reflectance.

2. Description of the Related Art In recent years, image reading devices read a reference white plate as a means of correcting sensitivity variations depending on the scanning position of an input document (for example, variations between elements such as COD, non-uniformity of light sources, etc.). It is common to use this value as a reference to quantize images read thereafter.

An example of the above-mentioned image reading device will be described below with reference to the drawings.

FIG. 4 shows a block diagram of a conventional image reading device. In FIG. 4, 11 is a reference white plate or original, 12 is a light source, 13 is a lens, 14 is a photoelectric conversion element, 1
6 is an amplifier, 16 is a divider, 17 is a MU/D converter, 18
is a temporary storage element.

First, the reference white plate 11 is irradiated with the light source 12 , and the reflected light is collected by the lens 13 , photoelectrically converted into an electric signal by the photoelectric conversion element 14 , and amplified by the amplifier 15 .

Here, when the reference white plate 11 is irradiated, the output of the amplifier 16 corresponding to each element arranged to receive reflected light from a plurality of positions of the reference white plate of the photoelectric conversion element 14 is defined as Wll. do.

When the input of the divider 16 is divided by a constant value R, the input of the divider 1
The output vn for each element of 6 is Vn = Wn/R
--(1) is obtained.

This value is subjected to MU/D conversion by the A/D converter 17 and stored in the temporary storage element 18 as a value corresponding to each element.

Next, the document is irradiated with the light source 12 instead of the reference white plate, and the lens 13. Photoelectric conversion element 14. The output corresponding to each element of the photoelectric conversion element 14 obtained through the amplifier 15 is turned on.

The divider 16 divides the output 15i by the output value Wfi of each element stored in the temporary storage element 18 when the reference white plate is irradiated.
When operated to divide Vn= Ran/wn
...The output of (2) is obtained.

This value represents the reflectance at a plurality of positions on the document with the reference white plate of each element of the photoelectric conversion element 14 as a reference. The value obtained by performing M/D conversion on this value by the A/D converter 17 is a value representing the gradation of an original having halftones such as a photograph.

Problems to be Solved by the Invention However, with the above configuration, it is impossible to correct the variations in the reference white plate itself. This is because sensitivity variations are corrected using the reference white plate as a reference, so there is a problem in that scratches, dust, etc. on the reference white plate are recognized as the reference and erroneous correction is performed.

In view of the above problems, the present invention provides an image reading device that is capable of correcting variations in a reference white plate.

Means for Solving the Problems In order to solve the above problems, an image reading device of the present invention includes:
The reference white plate is first read with a photoelectric conversion element, the read value is temporarily stored as a first signal, and then another position of the reference white plate is read with the photoelectric conversion element, and the value generated at that time is comparing a second signal and the first signal;
Replace the first signal with a second signal and store it only when the signal level is dog, and according to the stored signal value,
The purpose is to use each output of the photoelectric conversion element during subsequent document reading.

According to the above-described configuration, the present invention first stores the value corrected by the conventional technique as the first signal in the temporary storage element, and then corrects the other positions of the reference white plate again. comparing a second signal generated at the time with the first signal,
The first signal is switched to the second signal only when the second signal level becomes large.
The signal is replaced with the signal and stored in the temporary storage element. By repeating this operation, the maximum variation of the reference white plate (
The correction amount (maximum value of reflectance) is temporarily stored in the storage element, thereby eliminating the influence of scratches, dust, etc. on the reference white plate.

Embodiment Hereinafter, an image reading apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of an image reading device according to a first embodiment of the present invention.

11 is a reference white plate or original, 12 is a light source, 13 is a lens, 14 is a photoelectric conversion element, 16 is an amplifier, 16 is a divider,
17 is an A/D converter, 18 is a temporary storage element, and 19 is a comparator.

The operation of the image reading apparatus configured as described above will be described below with reference to FIGS. 1 and 2. First, the second
The figure shows signal waveforms in the main parts of FIG. 1. The reference white plate 11 is irradiated with the light source 12, and the reflected light is collected by the lens 13, photoelectrically converted into an electric signal by the photoelectric conversion element 14, and amplified by the amplifier 16, and the signal component of the output waveform is , the waveform shown by ■ in FIG. 2a is obtained. In addition,
The dots in this waveform (■) represent the influence of dust and scratches on the reference white plate. In the divider 16, the divider output divided by the constant value R is obtained by formula (1) as shown in the conventional example, and is stored in the - hour storage element 18.

Next, the reference white plate is moved in the direction of the arrow in Figure 1, and the waveform marked ■ in Figure 2 a (shows the case where there are no scratches on the white plate) is obtained as the signal component of the output waveform. . The divider 1e divides this value by a constant value R, and the output waveform is divided by a constant value R.
The D converter 17 performs A/D conversion, and the comparator 19 compares the output value of the M/D converter 17 with the value stored corresponding to each element of the photoelectric conversion element of the temporary storage element 18. If the output value of the /D converter is large, the mu/D converted value is again
It is stored in a location corresponding to the photoelectric conversion element. The correction amount re-stored in the negative time storage element in this way becomes as shown in FIG.

As described above, according to this embodiment, by changing the position of the reference white plate and performing correction again, and by providing a comparator between the mu/D converter output and the temporary storage element, To eliminate the influence of scratches on a reference white board and to reduce overall variation.

By repeating this operation, the amount of correction of the maximum value of the reflectance of the reference white plate is stored as a value in the temporary storage element, and the influence of scratches, dust, etc. on the reference white plate can be corrected.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram of an image reading device showing a second embodiment of the present invention. The difference in the configuration from the one shown in FIG. 1 in this figure is that the comparator 19 is provided to compare the converted value of the MU/D converter 17 itself. The operation of the image reading device configured as described above will be described below.

First, as shown in the conventional example and the first embodiment, the reference white plate 11 is irradiated with the light source 12, the reflected light is collected by the lens 13, converted into an electrical signal by the photoelectric conversion element 14, and then the amplifier 15, the output of the amplifier 16 is divided by a certain constant value R by the divider 16, the resulting value is A/D converted by the A/D converter 17, and temporarily stored in the - hour storage element 18.

Next, the reference white plate 11 is moved in the direction of the arrow in FIG. , the correction amount corresponding to each element of the photoelectric conversion element is read from the temporary storage element 18 for the correction amount obtained in the previous correction, and the output of the amplifier 16 is divided by the read correction amount by the divider 16.

Here, if the amplifier output corresponding to each element of the photoelectric conversion element of the previous reference white plate is Wjfi, and the amplifier output corresponding to each element of the photoelectric conversion element of the current reference white plate is W2n, then the output of the divider 16 is vnba, then.

This vn is subjected to Mu/D conversion by Mu/D converter 17, and compared by comparator 19 to see if this value is larger or smaller than R. Only when it is larger than R, output from Mu/D converter 1 By rewriting the value to the temporary storage element 18, the correction amount of the - time storage element is stored in the temporary storage element as a large value of the reflectance of the reference white plate.

As described above, by comparing the divider output with a constant value, the configuration of the comparator is simplified.

In addition, in the first and second embodiments, after the divider 16, the A/
Although the D converter 17 is connected, conversely, after Mu/D conversion, the value may be passed through a divider and stored in a temporary storage element, or the value of the Mu/D converter itself may be temporarily stored as a correction amount. Although it was stored in the memory element, it was not the value of the M/D converter itself, and finally,
It is sufficient if the correction amount based on the reference white plate is stored in the temporary storage element.

Further, in the second embodiment, the comparator 19 compares the output of the MU/D converter, but it may also compare the output of the divider with a certain value according to equation (3).

Effects of the Invention As described above, the present invention moves the reference white plate and provides a comparator that compares the correction amount obtained last time with the correction amount obtained this time, thereby eliminating scratches, dust, etc. on the reference white plate. can eliminate the influence of

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an image reading device according to a first embodiment of the present invention, FIG. 2 is a signal waveform diagram of the same embodiment, and FIG. 3 is a block diagram of an image reading device according to a second embodiment of the present invention. FIG. 4 is a block diagram of a conventional image reading device. 11...Reference white board or manuscript, 12...
・Light source, 13...Lens, 14...Photoelectric conversion element, 16...Amplifier, 16...
・Divider, 17...A/D converter, 18...
...-time storage element, 19... comparator. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (1)

[Claims] Converting the reflected light from the plurality of positions into an electric signal according to the amount of light by a plurality of photoelectric conversion elements arranged corresponding to the plurality of positions of the reference white plate, and storing the electric signal, A second electric signal generated in the photoelectric conversion element when the relative reading position between the reference white plate and the photoelectric conversion element is changed is compared with the stored electric signal, and the second electric signal is Only the part where the signal level is high is replaced with a second electrical signal and stored, and after this replacement operation is performed at least once, the above-mentioned electrical signal is An image reading device characterized by controlling each output of a photoelectric conversion element.