JP2000101804A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the background from being soiled in half tone the effect of a deteriorated luminous quantity becomes especially conspicuous. SOLUTION: Presence of an original is sensed (S2) in a standby state (S1), whether or not the original is in half tone is discriminated (S3), and when the original is in half tone, the value of a read counter is read (S4). An arithmetic equation selected from among a plurality of predetermined arithmetic equations based on the count is used to calculate a peak correction value (S5), the value is applied to a peak value read from an SRAM to correct it (S6), and the corrected value is stored in the SRAM and a peak register (S7). Then the original is read (S8) repetitively till an end of the original is detected (S9). When the original is not in half tone in the step S3, the processing is transferred directly to the reading in the step S9.

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, and more particularly, to an image reading apparatus that performs optical reading using a scanner such as a contact sensor.

[0002]

2. Description of the Related Art Conventionally, in an image reading apparatus using a solid-state imaging device such as a CCD or the like, a variation in sensitivity of each pixel of the solid-state imaging device or a document based on a signal of the solid-state imaging device obtained by reading a white reference plane. Correction of illumination light amount unevenness by the illumination system, so-called shading correction is performed. Further, in order to prevent the image from being deteriorated due to the decrease of the dynamic range due to the deterioration of the optical system with time, the deterioration of the optical system is detected by monitoring the shading data for the specific pixel and the average value of a certain range. .

In a conventional image reading apparatus, there is a roller immediately above a reading surface, and in the case of a reading apparatus which does not have a white reference, shading correction is performed once at the time of shipment from a factory, and the captured data is output when a power failure occurs. However, it is stored in a memory such as an SRAM which is backed up. Once stored, the light quantity setting value and the peak value are not updated unless shading is performed again or the RAM is cleared.

[0004]

However, if the user has been using the product for a long time after shipping the product, the light source LE
Due to the aging of D and the aging of the sensor chip,
The level actually read becomes lower than the white reference level at the time of shipment, so that the dynamic range is reduced and the gradation of the image is reduced. At the time of binary reading, even if the output is slightly deteriorated, the output is within the image processing range and the peak level is followed, so that no image abnormality occurs. Since the peak level correction is performed, the background stain is significantly generated.

[0005] Further, in the conventional image reading apparatus,
Since the 8-bit data after the A / D conversion is directly stored in the RAM as the shading data, the usage rate of the RAM is increased, and the area used for other corrections is reduced, or the capacity of the RAM used is increased. Is inevitable.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described circumstances, and has as its object to provide an image reading apparatus capable of preventing a halftone background stain in which the influence of light quantity deterioration is particularly prominent. It was done as.

[0007]

According to a first aspect of the present invention, there is provided a count value reading means for reading a count value of a read counter, and a divisor for calculating a divisor according to the count value read by the count value reading means. Calculating means, and dividing means for dividing the peak level at the time of halftone by the divisor calculated by the divisor calculating means, and removing background dirt when the light amount of the scanner is deteriorated. is there.

According to a second aspect of the present invention, in the first aspect of the present invention, the division number calculating means calculates the division number by using an arithmetic expression selected from a plurality of predetermined arithmetic expressions according to the count value. It is characterized in that the background is removed in accordance with the characteristics of the scanner used.

According to a third aspect of the present invention, in the first aspect of the present invention, a count value detecting means for detecting that the read count value has reached a certain count value, and an LED based on the detection result of the count value detecting means. And a light amount increasing means for increasing the amount of light of the scanner, and compensating for the deterioration of the amount of light even when the number of scanners reaches the durable number.

[0010]

FIG. 1 is a block diagram for explaining an example of an image reading apparatus to which the present invention is applied. 1 is a scanner, 2 is a light amount adjusting circuit, 3 is an A / D converter,
Is a light amount determination circuit, 5 is a dark output correction circuit, 6 is a shading correction circuit, 7 is a peak value detection circuit, 8 is a peak correction circuit, 9 is an offset adjustment circuit, 10 is a binarization circuit, 1
1 is a line buffer, 12 is a CPU, 13 is an SRAM,
Reference numeral 14 denotes a DRAM.

The scanner 1 is an optical scanner device such as a contact sensor or a CCD. The scanner 1 irradiates a light source such as an LED light source onto a document surface, captures the reflected light with a sensor chip, and photoelectrically converts the light amount to an analog signal. Captures electrical signals. The light amount of the light source is adjusted by the light amount adjustment circuit 2,
The video signal converted into the analog electric signal is converted into a digital signal by the A / D converter 3. Hereinafter, A
The case where the / D converter 3 performs 8-bit conversion will be described.

First, before reading an original, a white reference surface is read to acquire correction data necessary for dark output correction and shading correction. Thereafter, correction is performed using the correction data captured when reading the document. When reading the white reference plane, the peak value of the white reference plane is detected by the shading correction circuit 6, and the light amount adjustment circuit 2 is set so that the peak value falls within a certain range. Since the signal is an 8-bit digital signal, the maximum value is 255. However, if the light amount is too large, the saturation occurs to 255, so the light amount is adjusted so that the peak value becomes about 240.

At this time, the light amount adjustment set value is stored in the RAM, and thereafter, the set value is read out each time the light amount is read, and the light amount is set. At the same time, the peak value at this time is transferred from the register of the peak value detection circuit 7 to the RAM, and is stored there. After the light amount setting value is determined, the light source is turned off.
The FF is used to scan one line of the white reference plane, the data is captured by the dark output correction circuit 5, and then the light source is turned on to scan one line of the white reference plane. And store it in the RAM.

Next, in the operation of reading the original, when the original is set, the original is fed to the reading position of the scanner, and the light amount setting stored in the RAM is set in the light amount adjusting circuit 2. When the light source is turned on at the same time as the start of the reading operation and the document is fielded, the image information becomes
The data is taken into the image processing circuit via the D converter 3.
First, dark output correction is performed in the image processing circuit.

Since dark output correction data is stored for each reading position, the data is read out and the dark output data (hereinafter, referred to as D) is subtracted from the video data (hereinafter, referred to as V) obtained by reading the original. The calculated VD data is transferred to the shading correction circuit 6. In the shading correction circuit 6, shading correction data (hereinafter, referred to as W) for each pixel when the white reference plane is read.
Is read from the RAM, and correction is performed for each pixel. The peak correction circuit 8 applies a peak level correction to the data that is (V−D) * W after the correction.

At this time, the peak level to be used does not follow the peak level at the time of binary reading, so that nothing is done on the software side, but does not follow the peak level at the time of halftone reading. Therefore, the peak level (hereinafter, referred to as P) when the shading data is fetched is read, and the data (hereinafter, referred to as X) stored in a certain area (hereinafter, referred to as address A) in the RAM is read from the value. PX is calculated by division, and this is used as the peak level. Offset adjustment circuit 9, 2
The data is processed by the value conversion circuit 10 and finally becomes binary data of 1: black and 0: white. After being converted into binary data, the data is transferred to the line buffer 11, where it is sent to the print output unit for printing, or is compressed and transferred from the modem.

FIG. 2 is a flowchart for explaining an embodiment of the image reading apparatus according to the present invention.
The document is detected from 1) (S2), it is determined whether or not the document is halftone (S3). If the document is halftone, the value of the reading counter is read out (S4), and peak correction is performed by a selected arithmetic expression described later. The value is calculated (S5), and the SRA
The peak value read from M13 is corrected (S6),
The value is held in the SRAM 13 and the peak register (S
7). Thereafter, the reading operation is performed (S8), and the reading operation is repeated until the end of the document is detected (S9). In S3, if the document is not halftone, the operation proceeds to the reading operation in S9.

As described above, in the present invention, the following measures are taken so as not to generate halftone background stains. Each time a reading operation is performed, the reading counter of the system is incremented by one, and this reading operation count value is stored in a certain area of the RAM. Performed and calculated data X
Is stored at address A of the RAM. Several types of arithmetic expressions are prepared, and are selected according to a scanner deterioration curve described later.

X calculated by the arithmetic expression is generally small when the read count value is small, and is large when the read count value is large. At the time of halftone reading, by setting the value of PX to the peak level, the initial value is small because X is small, so the peak level is large, and when X deteriorates with time and X becomes large, the peak level becomes small. Is difficult to read.

When the value of the reading counter approaches the endurance number of the scanner, the value of X becomes considerably large, and the deterioration of the light amount becomes considerably large. Then, even with this correction, there is a possibility that the background will be read. It detects that the value of the reading counter reaches the endurance number of the scanner, and if it is detected,
The setting of the current adjustment circuit for adjusting the current of the LED light source is changed from the current setting to a setting for increasing the current, and the light amount of the LED is increased to prevent the occurrence of background contamination. At this time, the value of X in PX is fixed to the value calculated at the time of endurance.

As an example of the above arithmetic expression, when the peak value when reading the white reference surface is p, the read count value is a, and the scanner deterioration curve constants are b and c, the following is obtained. Peak value at halftone = p− (a ÷ b + c)

In the above equation, the scanner degradation curve constants b and c are selected in accordance with the scanner degradation (the scanner degradation is evaluated by several scans and the characteristics are measured). In the case of a scanner in which the reading characteristic is degraded by one every 200 readings, the arithmetic expression is p- (a ÷ 200 + 0).

In the case of a scanner having a scanner characteristic in which the reading level is degraded by 1 every 1000 sheets of reading and rapidly deteriorates by 10 by the initial 100 sheets, the arithmetic expression is p
− (A ÷ 1000 + 10).

[0024]

According to the first aspect of the present invention, there is provided a count value reading means for reading a count value of a reading counter, a division number calculation means for calculating a division number according to the count value read by the count value reading means, Dividing means for dividing the peak level at the time of halftone by the dividing number calculated by the dividing number calculating means, thereby preventing background contamination at the time of light quantity deterioration of the scanner.

According to a second aspect of the present invention, in the first aspect of the present invention, the division number calculating means calculates the division number by an arithmetic expression selected from a plurality of predetermined arithmetic expressions according to the count value. In addition, it is possible to perform image correction according to the light amount deterioration curve of each scanner.

According to a third aspect of the present invention, in the first aspect of the present invention, a count value detecting means for detecting that the read count value has reached a certain count value, and an LED based on the detection result of the count value detecting means. And a light amount increasing unit for increasing the amount of light, and compensating for light amount deterioration even when the number of scanners reaches the endurance number, so that halftone background stain can be prevented even when the number of scanners reaches the endurance number.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of an image reading apparatus to which the present invention is applied.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... scanner, 2 ... light amount adjustment circuit, 3 ... A / D converter, 4 ... light amount judgment circuit, 5 ... dark output correction circuit, 6 ... shading correction circuit, 7 ... peak value detection circuit, 8 ... peak correction circuit, 9 ... Offset adjustment circuit, 10 ... Binary circuit, 11 ... Line buffer, 12 ... CPU, 13 ... SR
AM, 14 ... DRAM.

Claims (3)

[Claims] 1. A count value reading means for reading a count value of a reading counter, a division number calculation means for calculating a division number according to the count value read by the count value reading means, and a calculation by the division number calculation means. A dividing means for dividing a peak level at the time of halftone by the obtained division number, and removing a background stain when the light amount of the scanner is deteriorated. 2. A scanner according to claim 1, wherein said division number calculating means calculates said division number by an arithmetic expression selected according to said count value from a plurality of predetermined arithmetic expressions and uses said scanner. An image reading apparatus that performs background removal according to characteristics of the image reading apparatus. 3. The image reading apparatus according to claim 1, wherein a count value detecting means for detecting that the read count value has reached a predetermined count value, and a light amount of the LED is determined based on a detection result of the count value detecting means. An image reading apparatus comprising: a light amount increasing unit for increasing the number of light beams, and compensating for light amount deterioration even when the number of scanners reaches the endurance number.