JPH01250050A - Detecting device for sticking dust of optical system - Google Patents

Abstract

PURPOSE:To detect abnormality for only dust, etc., which is stuck fixedly by detecting the same value being obtained as position information on dust, etc., sticking on the optical system when a prescribed number of continuous bodies are scanned. CONSTITUTION:An image signal S1 obtained by a line sensor 4 is compared by a comparing circuit 11 with a reference level S2 and converted into a binary signal, which is supplied to a belt processing circuit 13 to mask a part which becomes a dark signal owing to a conveyor belt 1 with a mask signal S4. A position detecting circuit 5 for dust, etc., stores position information on the dark signal according to an image signal and updates it every time a scan is made to detect the position information on the dust, etc., sticking on the optical system. A continuity check means 16 inputs the position information from the detecting circuit 15 every time one body is scanned and counts the number of pieces of the same position information. A decision means 17 decides the sticking of the dust according to the counted number from the continuity check means 16.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is used in a banknote discriminating device that distinguishes the authenticity of banknotes, whether they are genuine or defective, and determines whether the banknotes are valid or defective. In a photoelectric conversion device that obtains an image signal corresponding to the pattern of a banknote by repeatedly scanning a line with a line sensor via an optical system, dust, scratches, and The present invention relates to an optical system for detecting adhering dust and the like for detecting defects in the line sensor.

(Prior Art) Conventionally, for example, a light 71' used in a banknote discrimination device!
The conversion device is generally constructed as shown in FIG. That is, a light source (not shown) irradiates a banknote P that is preferentially held by the conveyor belt 1, and the reflected light from the banknote P is focused by a lens 3 through a transparent glass 2 serving as a protection member. For example, an image is formed on the light receiving surface of a CCD type line sensor 4. The line sensor 4 performs photoelectric conversion by repeatedly scanning a line in a direction perpendicular to the conveyance direction of the banknote P by self-scanning, and outputs an image signal corresponding to the pattern on the banknote P. Here,
FIG. 6 shows an example of an image signal obtained from the line sensor 4 through one scan.

In such a photoelectric conversion device, whether there is dust or scratches on the optical path of the optical system such as the transparent glass 2 or lens 3, or whether the line sensor 4 used is normal. In order to detect whether or not there is a banknote P, a white plate 5 is provided at the rear of the banknote P conveyance path, as shown in FIG. 5, and the white plate 5 is scanned before the banknote P is conveyed. An image signal as shown in FIG. 7(a) is obtained, and the obtained image signal is compared with a predetermined reference level voltage as shown in FIG. 7(b). It is checked whether or not there is an image signal S having a level lower than the reference level as shown in FIG. It is designed to perform diagnostic operations.

However, in the image signal obtained in the above diagnostic operation, in addition to the dust and scratches permanently attached to the optical system or the defects of the line sensor 4, there are also dust and dust temporarily attached to the optical system. Or, it may detect dirt or dust floating in the air on the optical path, and even in such cases, the device will notify you that there is an abnormality, so it will stop the operation and remove the dirt and dust. It was necessary to remove or inspect it. However, if an abnormality is detected due to dirt or dust that has temporarily adhered to the optical system or floating on the optical path, the dust or dirt has already been removed when the equipment is stopped for inspection. There were problems in that there were many noises that did not exist, lowering the operating rate of the equipment and poor maintainability.

Further, according to the conventional method, the detection range of dust etc. is limited to the range where the white plate 5 exists within the field of view of the optical system.
If the white plate 5 covering the entire field of view of the optical system cannot be provided due to physical constraints in the device configuration, there is also the problem that reliable abnormality detection cannot be performed.

(Problems to be Solved by the Invention) As described above, the present invention solves the problem of detecting an abnormality due to dust temporarily attached to the optical system, resulting in a decrease in operation rate and poor maintainability, and However, the detection range is limited by the size of the white plate, making it impossible to reliably detect abnormalities. This was developed to solve the problem, and it is possible to detect abnormalities only from fixedly attached dust, etc., and by detecting dust, etc. attached to the entire field of view of the optical system, the operation rate can be improved. It is an object of the present invention to provide an optical system-based detection device for adhering dust, etc., which is capable of improving maintenance performance, has excellent maintainability, and can reliably detect abnormalities.

[Structure of the Invention] (Means for Solving the Problems) The optical system attached dust detection device of the present invention detects a moving object by repeatedly scanning a line with a photoelectric converter through an optical system. A photoelectric conversion device that obtains an image signal includes a binarization means for binarizing the image signal obtained by scanning the photoelectric converter, and a binarization means for binarizing the image signal obtained by the binarization means for one scan. detecting a dark signal and storing position information indicating the position of the dark signal within the scanning range;
Regarding the dark signal in the binarized signal for subsequent scanning,
Position detection that obtains position information of dust, etc. attached to the optical system by detecting only dark signals that appear at the same or subsequent positions as the stored position information and storing the position information while updating it. a continuity determining means for determining whether or not the position information obtained by the position detecting means appears with the same value for a plurality of consecutive objects; On the other hand, when it is determined that positional information of the same value has appeared consecutively, the optical system is characterized by comprising a determining means that determines that there is dust or the like attached to the optical system.

(Function) The present invention is capable of
When a moving object is line scanned through the optical system,
Focusing on the fact that a dark signal is always obtained at the same scanning position, among the image signals obtained by line scanning an object, position information within the scanning range where a dark signal appears for one scan is stored, In the next scan, the position information where the dark signal appeared is stored at the position after the position indicated by the position information obtained in the previous scan, and the position information where the dark signal appeared is similarly updated for each scanning line. When scanning is completed, the stored position information is used as the position of the dust etc. attached to the optical system, and the same position information is used as the position information of the dust etc. attached to the optical system during consecutive scanning of a predetermined number of objects. When the value is obtained, it is determined that there is fixed adhering dust or the like in the optical system, and the determination result is output. This makes it possible to detect an abnormality only with respect to fixedly attached dust, etc., and also to reliably detect the adhesion of dust, etc. over the entire range of the field of view of the optical system.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 6 denotes a photoelectric conversion device used in a banknote discriminating device, which has the same configuration as, for example, the device shown in FIG. Reference numeral 10 denotes a scanning control circuit that drives a line sensor 4 composed of, for example, 256 CCD elements (corresponding to pixels), and also receives, for example, 10-bit address data ADR representing the position of the currently driven CCD element. Output sequentially. Reference numeral 11 denotes a comparison circuit, which connects the line sensor 4 as shown in FIG. 3(a).
By comparing the image signal s1 obtained from the image signal s1 with a predetermined reference level voltage S2 generated by the reference voltage generating circuit 12, the image signal s1 is binarized into a dark signal and a bright signal. The image signal s3 binarized by the comparator circuit 11 is output as a dark signal at a low level and a bright signal at a high level, as shown in FIG. 3<b>. Note that the reference level voltage S2 generated by the reference voltage generation circuit 12 is as follows:
For example, the operator can input the detected parameters using a keyboard or the like (not shown) as an input means.

The belt processing circuit 13 performs mask processing to exclude the image signal corresponding to the conveyor belt 1.1 that pinches and conveys the banknote P from the image signal S3 to be detected. That is, as shown in FIG. 3(a), the image signal S1 obtained from the line sensor 4 includes portions that become dark signals SBI and SB2 due to the conveyor belt 1.1, and the dark signals are detected. In the circuit of this embodiment, these dark signals SBI and SB2 are converted into meaningless signals, that is, bright signals, in order to exclude them from detection targets. Second belt processing circuit 13
Now, assuming that the mask signal s4 having a fixed waveform generated by the mask signal generation circuit 14 as shown in FIG. 3(c) is one human input, the comparison circuit 11 shown in FIG. 3(b) The binarized image signal s3 supplied from the conveyor belt 1.1 is used as the other input to generate an image signal S5 from which the dark signals SBI and SB2 caused by the conveyor belt 1.1 are removed, as shown in FIG. 3(d). It has become.

The pulses SMI and 8M2 in the mask signal S4 corresponding to the dark signals SBI and SB2 in the image signal S3 have pulse widths slightly larger than those of the dark signals SBI and SB2. It has become.

For example, as shown in FIG. 2, the dust position detection circuit 15 includes a D-type flip-flop 30. In-ta 31, A
ND gate 32, register 33, and comparator 3
It is composed of 4.

That is, the flip-flop 3o records the signal supplied to the data input terminal at the rising edge of the pulse applied to the clock input terminal CKI and outputs it to the data output terminal Q.

The data input terminal of this flip-flop 30 is connected so as to always maintain a high level, and is always set to a high level when the pulse applied to the clock input terminal CKI causes a rising change. It has become. Further, the image signal S5 outputted from the belt processing circuit 13 is connected to the clock input terminal CKI.
The signal is inverted by the AND gate 32, and the AND gate 32 performs a logical product. Furthermore, the reset input terminal R1 is for resetting the contents of the flip-flop 30 to a low level, and the output signal at the data output terminal Q also to a low level. A reset pulse R8Tl generated by a control circuit (not shown) is applied to this reset input terminal R1 before starting each scan.

1. The register 33 stores, for example, 10-bit data input to the data input terminal Di in synchronization with the rising edge of the pulse applied to the clock input terminal (2), and outputs it to the data output terminal Qi. The data input terminal Di of this register 33 is supplied with the address data ADR of the CCD element outputted from the scanning control circuit 10. Also, the address data ADR outputted from the data output terminal Qi is supplied. The data is sent to the comparator 34.
It is supplied to a CPU (not shown). Further, the reset input terminal R2 receives a reset pulse RS generated by a control circuit (not shown) before the conveyance of one banknote P is started.
T2 is applied and the contents of the register 33 are cleared.

Comparator 34 compares the data input to data input terminal A and the data input to data input terminal B, and the data input to data input terminal A is greater than the data input to data input terminal B. A high level signal is output to the output terminal O when the conditions A≧B are satisfied. The output signal from this output terminal O is supplied to one input terminal of an AND gate 32. The data input terminal A of the comparator 3.4 receives the address data ADR output from the scan control circuit 0, and the data input terminal B receives the output signal of the register 33.

The continuity check means 16 includes, for example, a CPU (as shown in the figure (7)).
Each time scanning of one banknote P is completed, it takes in the dust information sent from the register 33 of the detection circuit 15. By comparing the address information obtained from the banknote that was scanned earlier, it is checked whether the address information of the same value is continuous, and the address information of the same value is continuous. In this case, the consecutive number is counted.The number counted by the continuity checking means 16 is sent to the determining means 17.

The determination means 17 is configured by processing of, for example, a CPU (not shown), and determines the number of consecutive addresses in which the value set in the determination reference counter 18 and the same value of address information detected by the continuity check means 16 are consecutive. Compare with
When the number of consecutive pieces of address information having the same value becomes larger than the content of the determination reference counter 18, a detection signal indicating the presence of attached dust or the like is output. This detection signal is used, for example, to drive alarm means (not shown). In addition, the above-mentioned judgment standard counter 18
The value to be set can be input by the operator as a detection parameter using, for example, a keyboard or the like (not shown) as an input means.

Next, the operation will be explained with reference to FIG.

First, before transporting the banknote P, a control circuit (not shown) generates reset signals R5Tl and R3T2, and the flip-flop 30 of the dust etc. position detection circuit 15
and register 33 is cleared. Next, the line sensor 4 is
Scanning of the banknote P by is started. At this time, it is assumed that dust 20 is attached to the transparent glass 2 at the illustrated position, for example. As shown in FIG. 4(a), the above-mentioned scanning is performed sequentially from the leading end to the trailing end as the banknote P is transported. Note that the shaded area in the figure is the part that always outputs a dark signal if dust or the like is attached to a predetermined position of the optical system (the part corresponding to the 150th CCD element described below).
It shows.

The image signal S obtained from the line sensor 4 through this scanning
1 is the reference level voltage S in the comparator circuit 11 as described above.
It is binarized by comparing it with belt processing circuit 1.
3. As described above, the image signal S3 supplied to the belt processing circuit 13 is masked by the mask signal S4 in the portion that becomes a dark signal due to the conveyor belt 1.1, and is sent to the dust etc. position detection circuit 1 as an image signal S5 to be detected.
5.

Next, the dust etc. position detection circuit 15 which received the image signal S5
works as follows. First, the image signal S1 as shown in FIG.
5, it is inverted by the inverter 31 and becomes A.
It is supplied to one input terminal of the ND gate 32. At this time, the other input terminal of the AND gate 32 is kept at a high level, and the output signal of the inverter 31 is directly ANDed.
It passes through the gate 32 and is supplied to the clock input terminal CKI of the flip-flop 30. The other input terminal of the AND gate 32 is kept at a high level because the banknote P
Since the register 33 is cleared before the start of transport, even if the address data ADR is increased by the scan control circuit 10, the condition A≧B is satisfied in the comparator 34.

In this way, when the signal S5 is supplied to the flip-flop 301 via the inverter 31 and the A N D gate 32, the first falling edge (rising edge at the clock input terminal CK1) of the signal S5 changes. As a result, the flip-flop 30 is set to a high level, and the output signal of the data output terminal Q also changes from a low level to a high level. This change is transmitted to the clock input terminal CK2 of the register 33, and the scan control circuit 10 outputs the clock signal C.
The currently driven CC that has reached the data input terminal Di
Address data ADR of the D element is set in the register 33. For example, as shown in Figure 4(b), if 11 CCD elements from the 50th to the 60th output a low level, the change in the signal of the 50th CCD element causes the Address data ADR of the currently driven CCD element output from the scan control circuit 10
- "50" will be set in the register 33;

As long as the reset signal R5Tl is not applied, that is, unless the next scan is started, the flip-flop 30
Since the output signal does not change to rise, the dust detection circuit 15 does not operate for low level signals that appear thereafter. therefore,
Even if a low level signal based on the dust 20 attached to the transparent glass 2 appears at the position of the 150th CCD element, it will be ignored in this first scan (2).

In the next scan (2), it is assumed that the waveform of the image signal S1 as shown in FIG. 4(c) is obtained. That is, assume that the 20th CCD element outputs a low level. In this case, since "50" is stored in the register 33 due to the previous scan (■), the address data ADR of the CCD element
Even if l-20J is given to the comparator 34 as
The condition ≧B is not satisfied, therefore, the comparator 34
A low level signal is still output to the output terminal O of. Therefore, the image signal S input to the AND gate 32 via the inverter 31 is.

Since the transmission thereof is inhibited, no rising signal is applied to the clock input terminal CKI of the flip-flop 3), and the image signal S1 changing at the position of the address data ADR-r20J is ignored. Next, the CCD
The address data ADR of the element increases and the 70th C
Assuming that the CD element outputs a low level signal, the condition A≧B is established at this time, and the output signal of the output terminal 0 of the comparator 34 is at a high level. Therefore, the same operation as in the case of scanning (3) is performed. Address data ADR■ "70" is set in the register 33. and,
Subsequent changes in the image signal S1 will be ignored. In other words, the low level signal based on the dust 20 attached to the transparent glass 2 is also ignored in this scanning (2).

In the next scan (2), it is assumed that the waveform of the image signal S1 as shown in FIG. 4(d) is obtained. That is, assume that the 20th CCD element outputs a low level. In this case, since "70" is stored in the register 33 due to the previous scan (■), the address data ADR of the CCD element
Even if "20" is given to the comparator 34 as A2
Condition B is not satisfied, and therefore, a low level signal remains output to the output terminal O of the comparator 34. Therefore, in the same way as described above, the transmission of the image signal S1 input to the AND gate 32 via the inverter 31 is suppressed, and no rising signal is applied to the clock input terminal CKI of the flip-flop 30, and the address data is Image signal S that changes at the position of ADR=r20J
1 will be ignored. Next, if the address data ADR of the CCD element increases and the 150th CCD element outputs a low level signal, then the condition A2B is satisfied and the output signal of the output terminal O of the comparator 34 is It's at a high level. Therefore, the address data ADR-r150J is set in the register 33 by the same operation as in the case of scanning (2). Subsequent changes in the image signal S1 will be ignored. That is,
In this scanning ■, dust 20 attached to the transparent glass 2 is
This means that a low level signal based on

In subsequent scans ■, ■, . . . , the same operation as above is repeated, and as long as the position of the dust 20 attached to the transparent glass 2 does not change, the address data ADR-rl 50J
A low level signal always appears at the position , and the value r150j will remain in the register 33 when the last scan is completed. This value is determined by the continuity check means 16.
sent to.

Next, the same process as described above is repeated for the banknotes P that are subsequently conveyed, but the dust 2 attached to the transparent glass 2
Since the position of the banknote P does not change, the value r150j remains in the register 33 even when the scanning of the banknote P is completed, and this value is also checked by the continuity check means 16.
sent to.

The continuity checking means 16 counts how many times the address data ADR of the same value has been sent consecutively, and sends the counted number to the determining means 17.

The judgment means 17 compares the value set in the judgment standard counter 8 with the value sent from the continuity check means 16, and the value sent from the continuity check means 16 is counted as the value set in the judgment standard counter 18. When the value becomes larger than the value set in , it is assumed that there is fixed adhering dust in the optical system and a detection signal is output. This detection signal is transmitted to the operator by, for example, an alarm means, so that the operator can remove dust and perform other inspections.

In addition, if there is no fixed dust attached to the optical system,
The value obtained in the register 33 when the scanning of one banknote P is completed is the address data ADR of the CCD element corresponding to the boundary line formed between the side edge of the banknote P parallel to the conveying direction and the background thereof. will be obtained. This address data ADR changes for each banknote P conveyed due to skew, positional deviation, etc. of the banknote P when the banknote P is pinched and conveyed by the conveyor belt 1.1, and address data ADR of the same value is continuous. You won't get it many times. Therefore, it is possible to distinguish between cases where dust or the like is fixedly attached to the optical system, and it is possible to effectively detect dust or the like that is fixedly attached to the optical system.

As mentioned above, when dust is fixedly attached to an optical system, when scanning a banknote using that optical system, a dark signal is always obtained at the same scanning position. Among the image signals obtained by scanning, the address data of the CCD element of the line sensor when a low-level signal first appears in the scanning direction is obtained and stored, and for the next scanning, the address data obtained from the previous scanning is used. The address data of the CCD element when a low-level signal first appears at the position after the address data is obtained and stored, and the above operation is repeated to detect the position of the dust attached to the optical system and continuously When address data of the same value is obtained for a predetermined number of banknotes, a detection signal indicating that fixed dust has adhered to the optical system is output. Therefore, there is no need to stop and inspect the device in such a case, and a decrease in the operating rate of the device can be avoided and maintainability is also excellent. Furthermore, since the attachment of dust or the like can be detected over the entire field of view of the optical system, it is possible to reliably detect abnormalities and improve reliability.

In addition, in the above embodiment, detection was explained when there is dust attached to the optical system, but the detection is not limited to this. For example, when the optical system is scratched, it is possible to detect dust attached to the light receiving surface of the line sensor. The present invention can be similarly applied to detecting cases where a line sensor is scratched or damaged, or when a specific element of a line sensor is out of order, and provides the same effects as the above embodiments.

Furthermore, in the above embodiments, the case where the application is applied to a photoelectric conversion device used in a banknote discriminating device has been described, but the invention is not limited to this. A photoelectric conversion device that can be widely applied as long as it obtains an image signal of a moving object by repeatedly scanning lines of the moving object with a photoelectric converter through an optical system, such as a photoelectric conversion device used in equipment, etc. It is.

[Effects of the Invention] As detailed above, according to the present invention, position information within a scanning range in which a dark signal appears for one scan among image signals obtained by line scanning an object is stored. , in the next scan, the position information where the dark signal appeared is stored at the position after the position indicated by the position information obtained from the previous scan, and the position information where the dark signal appeared is similarly updated for each scanning line. When the scanning is completed, the stored position information is used as the position of the dust etc. attached to the optical system, and when a predetermined number of consecutive objects are scanned, the stored position information is used as the position information of the dust etc. attached to the optical system. When the same value is obtained, it is determined that there is fixedly attached dust etc. in the optical system and the judgment result is output, so that it is possible to detect abnormalities only for fixedly attached dust etc. Moreover, by detecting the adhesion of dust, etc. in the entire field of view of the optical system, we provide a device for detecting adhesion of dust, etc. in the optical system, which improves the operating rate, has excellent maintainability, and can reliably detect abnormalities. can do.

[Brief explanation of the drawing]

1 to 4 show one embodiment of the present invention, in which FIG. 1 is a block diagram showing the configuration, FIG. 2 is a detailed circuit diagram of the dust position detection circuit, and FIGS. The figure is a waveform diagram for explaining the operation, Figures 5 to 7 are for explaining the conventional example, Figure 5 is a diagram showing the configuration of the photoelectric conversion device, and Figures 6 and 7 are for explaining the conventional example. FIG. 3 is a waveform diagram for explaining the operation. DESCRIPTION OF SYMBOLS 1... Conveyance belt, 2, 3... Optical system, 4... Line sensor (photoelectric converter), 6... Photoelectric conversion device, 1
0: Scanning control circuit, 11: Comparison circuit (binarization means), 15: Dust, etc. position detection circuit (position detection means)
, 16... Continuity check means (continuity judgment means),
17... Judgment means, 20... Garbage, P... Banknotes (
moving objects). Applicant's representative Patent attorney Takehiko Suzue Figure 2 @ Figure 3 Figure 4 General connection 2'O + 5'o 200 Figure 4 Figure 6 Figure 7

Claims (1)

[Scope of Claims] A photoelectric conversion device that obtains an image signal of a moving object by repeatedly scanning lines of the object with a photoelectric converter through an optical system, comprising: an image signal obtained by scanning the photoelectric converter; A binarization means for binarizing, and detecting a dark signal in the binarized signal for one scan obtained by the binarization means and storing position information indicating the position of the dark signal within the scanning range. However, for dark signals in the binarized signal for subsequent scanning, only dark signals appearing at the same or subsequent positions as the stored position information are detected, and the position information is updated and stored. By doing so, there is provided a position detection means for obtaining position information of dust etc. adhering to the optical system, and a position detection means for detecting whether or not the position information obtained by this position detection means appears with the same value for a plurality of consecutive objects. a continuity determination means for making a determination; and a determination for determining that there is dust, etc. attached to the optical system when the continuity determination means determines that position information of the same value has continuously appeared for a predetermined number of objects. What is claimed is: 1. An optical system for detecting adhered dust, etc., comprising: means.