JPH0721306A - Detecting method for stain of image sensor - Google Patents

Abstract

PURPOSE:To provide a method to correctly detect the stains and the dust of an image sensor before they affect the images to be read. CONSTITUTION:An optical reader converts the light reflected on a slip into electric signals by an image sensor 1 and performs the amplification, A/D conversion and binarization of the output of the sensor 1 through an amplifier 2, an A/D converter 3 and a binarizing circuit 4 respectively. A detecting means 7 is added to the optical reader to detect the presence or absence of the vertical component of the black picture element included in a clear area of the slip and the position information on the vertical component out of a video memory 6 which stores image of the slip, together with a storing means 8 which stores the information on the presence/absence and the position of the vertical component of the black picture element detected by the means 7, and a means 9 which decides the presence of stains or dust of the sensor 1 and outputs an alarm when the vertical components are detected at the same position based on the information on the presence/absence of the vertical component and its position that is acquired by the precedent reading of the slip and the information acquired by the present reading of the slip.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor in an optical reading device used for inputting an image of a form, and more particularly to an image sensor stain detecting method capable of detecting stains on the image sensor in advance.
(Note that the term "dirt" in this specification has a broad meaning including dust adhesion and the like.)

[0002]

2. Description of the Related Art In a conventional optical reader,
When the image sensor portion is dirty, it is impossible to distinguish whether the read signal from the image sensor is the read signal of the original document itself or the read signal of the original document is affected by the dirt of the image sensor. Therefore, the slice level of the read signal is shifted due to dirt on the image sensor, and black lines or white spots may occur in the read document information. Therefore, in order to prevent such black streaks and white spots from occurring, by comparing the read signal of the white data when the image sensor unit is not dirty and the read signal of the current white data, It was considered to detect in advance the dirt on the image sensor unit, which would have an adverse effect. Such a conventional technique is described in, for example, Japanese Patent Application Laid-Open No. 2-288766 (Japanese Patent Application No. 1-111518).

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The one described in Japanese Patent Application No. 88766 (Japanese Patent Application No. 1-111518) simply compares the read signals of two white data, and therefore not only the image sensor is contaminated but also the deterioration of the light source and the white reflection. Dirty plate, medium (form, etc.)
There was a problem that an alarm would be issued even if the dirt on the floor. An object of the present invention is to provide a method for detecting dirt on an image sensor, which can detect dirt on the image sensor regardless of deterioration of the light source and dirt on the medium.

[0004]

To achieve the above object, the present invention uses a clear area of an OCR form (an area where printing / writing is prohibited to detect an edge of the OCR form), and an image is obtained. The black pixel vertical component (perpendicular to the scanning direction of the image sensor) on the image plane generated by the dirt of the sensor unit is detected, and it is obtained by the form reading operation to distinguish the dirt of the image sensor unit and the dirt of the medium. Stores the position information of the black pixel vertical component,
This stored information is read, the previous position information and the current position information are compared and collated, and the match signal detects the dirt on the image sensor unit.

[0005]

According to the present invention, since the information of the black pixel vertical component in the clear area of the OCR form is detected and compared every time for each form, the malfunction of the image sensor unit can be prevented without deterioration due to the deterioration of the light source and the stain of the medium. Only dirt can be detected.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. 1, 2 and 3. First, FIG. 1 is a block diagram for performing a method according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 is an image sensor composed of a photodiode or CCD for converting light reflected from a form surface into an electric signal, 2 is an amplifier for amplifying a read electric signal output from the image sensor 1, and 3 is an amplifier. The A / D converter 4 for converting the electric signal amplified in 2 into digital data is discriminated between the white data (0) and the black data (1) with reference to the slice level designated by the controller 5. A binarizing circuit for binarizing, 5 is a control unit for controlling all functions, 6 is binarized data of a form clear area (described later) shown by reference numeral 12 in FIG. 3, and reference numeral in FIG. A video memory for storing binarized data of a recognition target area (described later) indicated by 16 and 7 is position information d (dimension from the bottom edge of the form) and θ of the clear area output from the control unit 5. A vertical component detecting unit for detecting the presence / absence of a black pixel vertical component and position information of the form clear area using the form skew angle), and 8 stores presence / absence of a pixel vertical component and position information obtained by the vertical component detecting unit 7. Vertical component position information storage area, 9 is a vertical component detection unit 7
In this case, the position information of the black pixel vertical component detected this time is compared with the position information of the previously detected black pixel vertical component stored in the vertical component position information storage area 8, and if they are the same position, the control unit 5 is a position information comparison unit that outputs an alarm.

FIG. 2 is a diagram for explaining an OCR form used in the present invention. In FIG. 2, 10 is a clear area (a blank area where nothing is printed) provided around the form, and 10a is a clear area with a width d provided at the bottom of the form. Next, the operation of the first embodiment of the present invention will be described. In the present embodiment, the clear area 10a at the lower end of the form in FIG. 2 is used to detect dirt on the image sensor unit, and the processing will be described below. In the normal image sensor 1, a light source and a photodiode array connected in series are arranged in parallel with the main scanning direction, and the photodiode receives the reflected light of the light source reflected from the medium (form) in one scan, and It is a system that shifts and outputs electric charges generated by photoelectric conversion in a diode. Therefore, if dirt adheres to the image sensor, the photodiode cannot receive the reflected light from the medium (form etc.) sufficiently,
It is regarded as black data because electric charges are not sufficiently generated by photoelectric conversion. Since the image sensor or the medium scans in the sub-scanning direction in this state, the black data appears at the same position on the image. As a result, a black pixel vertical component perpendicular to the scanning direction of the image sensor is generated.

FIG. 3 is a view showing a read image of an OCR form for explaining the generation of the black pixel vertical component as described above. In FIG. 3, 11 is a form read image, 12
Is a form clear area, 13 is a black pixel vertical component generated due to dirt on the image sensor, 14 is a dirty image on the form, 15 is a printed print image, 16 is a recognition target area,
Reference numeral 17 is a form skew angle θ, and 18 is a form bottom end clear area (width d). In the figure, the horizontal axis (X axis)
Is taken in the scanning direction of the image sensor, and the Y axis is taken perpendicularly thereto.

The vertical component detecting unit 7 pays attention to the bottom edge clear area 18 of the form, and utilizes the fact that the black pixel vertical component 13 is generated in the clear area 18 when dirt is attached to the image sensor unit. Position information (coordinates in the X-axis direction, that is, X coordinate) is detected. The detected black pixel vertical component “present” information and position information (X coordinate) are stored in the vertical component position information storage area 8. The position information comparison unit 9 detects the vertical component detection unit 7 when reading the next form.
Position information of the vertical component position information storage area 8 and the current vertical component detection unit 7 according to the information of the black pixel vertical component “present” from
The position information obtained in step 1 is compared and collated. As a result of this comparison and collation, when both position information match, it is determined that the image sensor unit is dirty and an alarm is issued.

On the other hand, not the image sensor is dirty,
When the medium (form) is soiled, the images shown by reference numerals 14 and 15 in FIG. 3 are obtained. Strictly speaking, the document is always skewed (inclined) with respect to the image sensor, and therefore is often not perpendicular to the scanning direction of the image sensor but oblique. Therefore, even if the vertical component image noise happens to occur due to the straight line of the print thread as shown by reference numeral 15, the form skew angle θ becomes random, and therefore the vertical component image noise is continuously output at the same position. Is extremely small. Therefore, in a continuous form reading operation, it is extremely unlikely that a component perpendicular to the image sensor is continuously detected in the clear area due to a cause other than the stain on the image sensor unit, and no alarm is issued. Further, in the present embodiment, the black pixel vertical component is not detected even when the light source is deteriorated because it is not a simple comparison of white data. For this reason, it is possible to detect only the dirt on the image sensor unit and issue an alarm.

Next, a second embodiment of the present invention will be described. Figure 1
In, the OCR form is read by the image sensor 1, and the read image is output as digital data by the A / D converter 3. The binarization circuit 4 converts the data into white data (0) and black data (1). At that time, O in FIG.
When reading the clear area 10 (usually the area 10a within a few mm from the bottom edge of the form), which is an area where printing and writing are prohibited on the outer frame of the CR form, it is binarized so that it is output darker than a normal read image. The slice level for control is controlled to be set to a low value. By doing so, it is possible to detect a minute stain on the image sensor unit before the image to be recognized is affected (a black line appears). In the second embodiment, it is possible to control the slice level of the image in the clear area and the image in the recognition target area.
By providing a means for storing the state and the degree of dirt detection corresponding thereto, the degree of detection (corresponding to the slice level) can be changed according to the form / character type / state.

Further, by providing an image sensor cleaning mechanism, self-cleaning is possible. For example, when the position information comparison unit 9 detects a stain on the image sensor unit and outputs an alarm signal, the wiper or the like is operated by the alarm signal to automatically remove the stain on the image sensor unit. do it.

[0013]

According to the present invention, since the information of the black pixel vertical component in the clear area of the OCR form is detected and compared for each form, the image sensor unit can be operated without malfunction due to deterioration of the light source and contamination of the medium. It is possible to detect only the dirt of the and issue an alarm. Further, according to the present invention, it is possible to detect the stain on the image sensor unit before the influence of the stain on the read image (black line seeping out) occurs.

[Brief description of drawings]

FIG. 1 is a block diagram for implementing an image sensor stain detection method of the present invention.

FIG. 2 is a diagram for explaining an OCR form used in the present invention.

FIG. 3 is a diagram for explaining generation of a black pixel vertical component when dirt is attached to the image sensor unit.

[Explanation of symbols]

 1 image sensor 2 amplifier 3 A / D converter 4 binarization circuit 5 control unit 6 video memory 7 vertical component detection unit 8 vertical component position information storage area 9 position information comparison unit 10 clear area 10a clear area at the bottom of the form 11 form Scanned image 12 Form clear area 13 Image sensor dirty image 14 Form dirty image 15 Form print thread image 16 Recognition area 17 Form skew angle 18 Form bottom clear area

Claims (1)

[Claims] 1. A method for detecting dirt of an image sensor in an optical reading device for optically reading a form, wherein an image of the form is read and stored in a memory, and black pixels in a clear area of the form are read from the image data stored in the memory. Presence / absence of the vertical component and position information of the detected black pixel vertical component are held, and the presence / absence and position information of the black pixel vertical component obtained by the previous form reading and this time are stored. The presence or absence of the black pixel vertical component and position information obtained by reading the form of the above are compared, and when the result of the comparison shows that the black pixel vertical component is detected at the same position, it is regarded as a stain on the image sensor. Characteristic image sensor dirt detection method.