JP3994669B2 - Photodetector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light detection device used in a paper sheet detection device, a paper sheet discrimination device, and the like.
[0002]
[Prior art]
This type of light detection device includes a light emitting element that irradiates measurement light to an object to be inspected and a light receiving element that detects measurement light from the light emitting element, and emits light based on an output signal of the light receiving element. An apparatus configured to detect whether or not an object to be inspected that exists between an element and a light receiving element is an object that transmits measurement light is known. For example, when the above-described light detection device is applied to a paper sheet detection device to detect paper sheets such as banknotes and securities, the wavelength band (for example, about 940 nm) that transmits the paper sheets as a light receiving element is used. When an LED that outputs light is used and measurement light emitted from the LED to the object to be inspected passes through the object to be inspected and is received and detected by the light receiving element, the object to be inspected is a paper sheet. If the measurement light emitted from the LED to the object to be inspected does not sufficiently pass through the object to be inspected and is not received or detected by the light receiving element, the object to be inspected is a paper sheet. Judging that it is not a kind.
[0003]
By the way, in the above-described photodetection device, there is a variation for each element in the light emission output of the light emitting element and the detection sensitivity of the light receiving element. For this reason, variation adjustment of the light emission output of the light emitting element and the detection sensitivity of the light receiving element is performed for each light detection device at the time of product shipment.
[0004]
[Problems to be solved by the invention]
However, the conventional technique has a problem that it takes time for the adjustment process of the photodetection device because the operator manually performs the adjustment of variation.
[0005]
In addition, the light output of the light-emitting element and the detection sensitivity of the light-receiving element change their characteristics even when the element itself changes over time or when dust or dirt adheres to it. It becomes difficult to do. For this reason, it is necessary to adjust characteristic changes such as the light emission output of the light emitting element and the detection sensitivity of the light receiving element even when the photodetection device is used. In addition, the characteristics of the light emission output of the light emitting element may change depending on the temperature, and similarly, it becomes difficult to appropriately detect the measurement light by the light detection device.
[0006]
The present invention has been made in view of the above points. Even when using a light detection device, the light emission output of the light emitting element and the variation in detection sensitivity of the light receiving element and the correction of the characteristic change are surely and appropriately performed for each product. It is an object of the present invention to provide a photodetection device that can be performed in a simple manner.
[0007]
[Means for Solving the Problems]
The light detection device according to the present invention includes a light emitting element that irradiates measurement light to an object to be inspected, a light receiving element that detects measurement light from the light emitting element, A memory that stores in advance a ratio between a current value supplied to the light emitting element when the measurement light is detected and a current supply value supplied to the light emitting element when the light receiving element detects the measurement light in a state where the inspection target exists. And a supply current value detection means for detecting the supply current value to the light emitting element when the measurement light is output from the light emitting element at a predetermined timing when the inspection target does not exist and the light receiving element detects the measurement light; A supply current value determining means for determining a supply current value to the light emitting element based on a supply current value detected by the supply current value detecting means and a ratio stored in advance in the storage means; and a supply current value to the light emitting element. At the supply current value determination means It is characterized in that includes a supply current value control means for controlling such that the boss was supplied current value.
[0008]
In the light detection device according to the present invention, the storage means causes the supply current value to the light emitting element when the light receiving element detects the measurement light in the state where the inspection target does not exist and the state where the inspection target exists. A ratio with a current value supplied to the light emitting element when the light receiving element detects the measurement light is stored in advance. The supply current value detecting means outputs the measurement light from the light emitting element at a predetermined timing when there is no object to be inspected, and the supply current value to the light emitting element when the light receiving element detects the measurement light is detected. The value determination means determines the supply current value to the light emitting element based on the supply current value detected by the supply current value detection means and the ratio stored in advance in the storage means. The supply current value control means controls the supply current value to the light emitting element to be the supply current value determined by the supply current value determination means. As a result, the supply current value to the light emitting element is adjusted based on the ratio stored in advance in the storage means, and the light emission output of the light emitting element and the detection sensitivity of the light receiving element vary from product to product. Can be suppressed. In addition, it is possible to eliminate an artificial work process for variation adjustment, and it is possible to shorten the time required for adjustment of the light detection device.
[0009]
Further, in the light detection device according to the present invention, a change in characteristics of the light emission output of the light emitting element and the detection sensitivity of the light receiving element due to a change with time, adhesion of dust or the like, etc. It is possible to correct appropriately and reliably at each timing.
[0010]
The apparatus further comprises a temperature sensor that detects the ambient temperature of the light emitting element, and a correction unit that corrects a ratio stored in advance in the storage unit based on the ambient temperature detected by the temperature sensor. Preferably, the supply current value to the light emitting element is determined based on the supply current value detected by the supply current value detection means and the ratio corrected by the correction means. In such a configuration, the correction means corrects the ratio stored in advance in the storage means based on the ambient temperature detected by the temperature sensor, and the supply current value determination means detects the ratio by the supply current value detection means. The supply current value to the light emitting element is determined based on the supply current value and the ratio corrected by the correction means. Thereby, the characteristic change of the light emission output of the light emitting element due to the temperature change can be corrected, and the object to be inspected can be detected independent of the temperature change of the light emitting element.
[0011]
In addition, the supply current value to the light emitting element when the light receiving element detects the measuring light in a state where the inspection target does not exist is the light emission when the light receiving element detects the measuring light in the state where the inspection target does not exist. The supply current value to the light emitting element when the light receiving element detects the measurement light in the state where the inspected object exists is obtained by measuring the supply current value to the element a plurality of times. The supply current value to the light emitting element when the light receiving element detects the measurement light in the state where the inspection object exists for each of the plurality of inspected objects can be obtained based on a statistical method. preferable. When configured in this way, the supply current value to the light emitting element when the light receiving element detects the measuring light in a state where the inspection target does not exist, and the light receiving element in the state where the inspection target exists Since the supply current value to the light-emitting element when detecting is obtained by a statistical method, the ratio stored in advance in the storage means can be appropriately obtained.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the photodetection device according to the present invention will be described in detail with reference to the drawings. In the present embodiment, an example in which the present invention is applied to a paper sheet detection apparatus will be described.
[0013]
First, based on FIG. 1, the structure of the paper sheet detection apparatus which concerns on embodiment of this invention is demonstrated. FIG. 1 is a block diagram illustrating a configuration of a paper sheet detection apparatus according to the present embodiment.
[0014]
The paper sheet detection apparatus 1 includes a light emitting diode (LED) 11 as a light emitting element, a phototransistor (PTr) 13 as a light receiving element, and a temperature sensor 15. The LED 11 and the PTr 13 are arranged with a predetermined interval so that the inspection target T can pass between them. The LED 11 irradiates the inspection target T with measurement light having a predetermined wavelength band. In the present embodiment, the wavelength band of the measurement light is set to a wavelength band capable of transmitting paper sheets such as banknotes, paper tickets (number tickets, numbered tickets), for example, about 940 nm. The PTr13 detects measurement light from the LED 11 (including measurement light transmitted through the inspection target T). The temperature sensor 15 detects the ambient temperature of the LED 11 and PTr 13, and is disposed in the vicinity of the LED 11 and PTr 13.
[0015]
The paper sheet detection apparatus 1 further includes a control unit unit 20. The control unit 20 is a processing unit that controls signal processing and the like of the entire paper sheet detection apparatus 1 and includes a central processing unit (CPU), ROM, RAM, and the like (not shown). The control unit unit 20 outputs a control signal for controlling the light emission output (luminance) of the LED 11 to the D / A conversion circuit 31 by performing calculation according to a control program stored in advance, and a binarization circuit Based on the output signal from 35, it is determined whether or not the inspection object T is a paper sheet.
[0016]
The D / A conversion circuit 31 is for converting the control signal output from the control unit 20 into a DC voltage signal. The output of the D / A conversion circuit 31 is connected to the voltage / current conversion circuit 33, and the output of the voltage / current conversion circuit 33 is connected to the LED 11. The voltage / current conversion circuit 33 is for generating a current proportional to the DC voltage signal output from the D / A conversion circuit 31 and supplying it to the LED 11. The control signal output from the control unit unit 20 changes the supply current value to the LED 11 and changes the light emission output of the LED 11.
[0017]
An output from the PTr 13 is connected to the binarization circuit 35 described above. The binarization circuit 35 is for converting the value of the current that flows when the PTr 13 receives light into a voltage signal (digital signal). The output of the binarization circuit 35 is connected to the control unit unit 20.
[0018]
An output from the temperature sensor 15 is connected to the control unit 20 via a current-voltage conversion circuit (not shown).
[0019]
Next, based on FIG. 2, the structure of the control unit part 20 is demonstrated in detail. FIG. 2 is a block diagram for explaining the function of the control unit 20. The control unit 20 performs processing according to a control program stored in a ROM or the like, and as a functional component, as shown in FIG. 2, a storage unit 21 (storage unit) and a correction unit 23 (Correction means), supply current value detection section 25 (supply current value detection means), supply current value determination section 27 (supply current value determination means), supply current value control section 29 (supply current value control means), , And is configured.
[0020]
The storage unit 21 is configured by a ROM or the like, and supplies a current value to the LED 11 when the PTr 13 detects measurement light in a state where there is no paper sheet as the inspection target T, and the inspection target T as the inspection target T. The ratio with the supply current value to the LED 11 when the PTr 13 detects the measurement light in the state where the paper sheet exists is stored in advance.
[0021]
Here, in a state where there is no paper sheet as the inspection target T, a current value supplied to the LED 11 when the PTr 13 detects measurement light, and a state where a paper sheet as the inspection target T exists. A method for obtaining the value of the current supplied to the LED 11 when the PTr 13 detects the measurement light will be described.
[0022]
First, a method for obtaining a supply current value to the LED 11 when the PTr 13 detects measurement light in a state where there is no paper sheet will be described. In the state where the inspection target T does not exist, the measurement light is output while changing the light emission output of the LED 11 by changing the supply current value to the LED 11 to increase or decrease, and when the PTr 13 detects the measurement light, the LED 11 receives the measurement light. Measure the supply current value. This measurement is repeated several times. These measurements are performed at a reference temperature (for example, 25 ° C.). The supply current value to the LED 11 measured a plurality of times, for example, becomes a sample frequency distribution FD1 as shown in FIG. Then, by taking this sample frequency distribution FD1 into consideration, the supply current value “C” to the LED 11 when the LED 11 detects the measurement light in a state where there is no paper sheet is obtained based on a statistical method.
[0023]
Next, a method for obtaining a supply current value to the LED 11 when the PTr 13 detects measurement light in a state where paper sheets are present will be described. Prepare multiple paper sheets as samples. And in the state which inserted this sample between LED11 and PTr13, measuring light was output, changing the light emission output of LED11 by changing the supply current value to LED11, and PTr13 permeate | transmitted the sample. A supply current value to the LED 11 when measuring light is detected is measured. This measurement is performed multiple times for each sample. These measurements are performed at a reference temperature (for example, 25 ° C.). The supply current value to the LED 11 measured a plurality of times, for example, shows a sample frequency distribution FD2 as shown in FIG. The sample frequency distribution FD2 has a variation between supply current values “A” to “B” to the LED 11. Then, by considering the variation of the sample frequency distribution FD2, the supply current value “A” to the LED 11 when the LED 11 detects the measurement light in the state where the paper sheet exists is obtained based on a statistical method.
[0024]
Reference is again made to FIG. The correction unit 23 reads and corrects the ratio stored in advance in the storage unit 21 based on the ambient temperature detected by the temperature sensor 15. The correction unit 23 obtains a temperature correction coefficient corresponding to the ambient temperature detected by the temperature sensor 15 based on the relationship between the ambient temperature and the temperature correction coefficient shown in FIG. Then, the correction unit 23 corrects the ratio stored in advance in the storage unit 21 by multiplying the ratio stored in the storage unit 21 by the calculated temperature correction coefficient. The correction unit 23 sends the corrected ratio to the supply current value determination unit 27.
[0025]
The relationship between the ambient temperature and the temperature correction coefficient is set as follows. First, in the operating temperature range of the paper sheet detection apparatus 1 (for example, a range of −20 ° C. to 80 ° C.), the PTr 13 is measured in a state where there is no paper sheet as the inspection target T while changing the temperature. A supply current value (forward current value) to the LED 11 when light is detected and a detected current value (photocurrent value) of the PTr 13 are measured. Next, the supply current value to the LED 11 at each measurement temperature is expressed as a relative value when the supply current value to the LED 11 at the reference temperature (for example, 25 ° C.) is “1”. Similarly, the detected current value of PTr13 at each measurement temperature is expressed as a relative value when the detected current value of PTr13 at the reference temperature (for example, 25 ° C.) is “1”. Then, for each measured temperature, the ratio of the relative value of the supply current value to the LED 11 and the relative value of the detection current value of the PTr 13 (the relative value of the supply current value to the LED 11 / the relative value of the detection current value of the PTr 13) is calculated. calculate. The calculated ratio is a temperature correction coefficient at each measurement temperature. In the present embodiment, since the reference temperature is set to 25 ° C., the temperature correction coefficient is larger than “1” in a region higher than 25 ° C., with 25 ° C. being “1” as shown in FIG. Thus, the temperature becomes lower than “1” in the region lower than 25 ° C.
[0026]
The supply current value detection unit 25 outputs measurement light from the LED 11 at a predetermined timing when the inspection target T does not exist, and detects the supply current value to the LED 11 when the PTr 13 detects the measurement light. . The supply current value detection unit 25 outputs a control signal to the D / A conversion circuit 31 at a predetermined timing when the inspection target T does not exist, for example, when the paper sheet detection apparatus 1 is activated or idling. The measurement light is output from the LED 11 and the supply current value to the LED 11 is increased or decreased to change the emission output of the LED 11. Based on the output signal from the binarization circuit 35, the supply current value detection unit 25 determines whether or not the PTr 13 has detected the measurement light, and the supply current value to the LED 11 when the PTr 13 has detected the measurement light ( The PTr 13 detects the minimum supply current value to the LED 11 that detects the measurement light. The supply current value detection unit 25 sends the detected supply current value to the LED 11 to the supply current value determination unit 27.
[0027]
The supply current value detection unit 25 outputs the measurement light from the LED 11 every time a predetermined period elapses as the predetermined timing described above, and detects the supply current value to the LED 11 when the PTr 13 detects the measurement light. You may make it do. In this case, it is necessary for the paper sheet detection apparatus 1 to separately detect that the inspection target T is not inserted between the LED 11 and the PTr 13.
[0028]
The supply current value determination unit 27 receives the ratio sent from the correction unit 23 and the supply current value to the LED 11 sent from the supply current value detection unit 25, to the LED 11 detected by the supply current value detection unit 25. The supply current value to the LED 11 is determined based on the supply current value and the ratio corrected by the correction unit 23. Specifically, the supply current value to the LED 11 is determined by multiplying the supply current value detected by the supply current value detection unit 25 by the ratio obtained by multiplying the supply current value to the LED 11 by the temperature correction coefficient. The supply current value determination unit 27 sends the determined supply current value to the LED 11 to the supply current value control unit 29.
[0029]
The supply current value control unit 29 receives the supply current value to the LED 11 sent from the supply current value determination unit 27, and the supply current value to the LED 11 becomes the supply current value determined by the supply current value determination unit 27. The control signal is generated so that the supply current value to the LED 11 becomes the supply current value determined by the supply current value determination unit 27, and is output to the D / A conversion circuit 31. As a result, the supply current value to the LED 11 becomes the supply current value determined by the supply current value determination unit 27, and the LED 11 has a light emission output corresponding to the supply current value determined by the supply current value determination unit 27. Measuring light is output.
[0030]
In addition, the control unit 20 supplies the LED 11 based on the supply current value to the LED 11 detected by the supply current value detection unit 25 (the minimum supply current value to the LED 11 for which the PTr 13 detects the measurement light). When the current value becomes larger than the predetermined value, it is determined that the performance of the LED 11 or PTr13 has deteriorated due to dirt, life, etc., and a maintenance request signal is output. Thus, maintenance such as replacement of the LED 11 or the PTr 13 can be reliably performed before a malfunction occurs in the paper sheet detection apparatus 1.
[0031]
Thus, in the paper sheet detection apparatus 1 according to the present embodiment, the control unit unit 20 includes the storage unit 21, the correction unit 23, the supply current value detection unit 25, and the supply as functional components. The current value determination unit 27 and the supply current value control unit 29 are configured. When the PTr 13 detects the measurement light in the state where the sheet as the inspection target T does not exist in the storage unit 21, A ratio between the supply current value to the LED 11 and the supply current value to the LED 11 when the PTr 13 detects the measurement light in a state where the paper sheet as the inspection target T exists is stored in advance. In the correction unit 23, the ratio stored in advance in the storage unit 21 is corrected based on the ambient temperature of the LED 11 and PTr 13 detected by the temperature sensor 15. The supply current value detection unit 25 outputs measurement light from the LED 11 at a predetermined timing when the inspection target T does not exist, and detects the supply current value to the LED 11 when the PTr 13 detects the measurement light. The supply current value determination unit 27 determines the supply current value to the LED 11 based on the supply current value detected by the supply current value detection unit 25 and the ratio corrected by the correction unit 23. The supply current value control unit 29 is controlled so that the supply current value to the LED 11 becomes the supply current value determined by the supply current value determination unit 27. As a result, the supply current value to the LED 11 is adjusted based on the ratio stored in advance in the storage unit 21, and the occurrence of variations in the light emission output of the LED 11 and the detection sensitivity of the PTr 13 from product to product is suppressed. be able to. In addition, it is possible to eliminate an artificial work process for variation adjustment, and it is possible to shorten the time required for adjustment of the paper sheet detection apparatus 1, so that a significant effect can be obtained in reducing the cost.
[0032]
Further, in the paper sheet detection apparatus 1, a change in characteristics of the light emission output of the LED 11 and the detection sensitivity of the PTr 13 due to a change with time, adhesion of dust or the like is detected at a predetermined timing when the inspection target T does not exist. Every time (for example, when the paper sheet detection apparatus 1 is started, when idling, etc.), the correction can be performed appropriately and reliably.
[0033]
In the paper sheet detection apparatus 1, the ratio stored in advance in the storage unit 21 is corrected by the correction unit 23 based on the ambient temperature of the LED 11 and PTr 13, and the supply current value determination unit 27 supplies Since the supply current value to the LED 11 is determined based on the supply current value detected by the current value detection unit 25 and the ratio corrected by the correction unit 23, the characteristic change of the light emission output of the LED 11 due to the temperature change, And the characteristic change of the light receiving sensitivity of the PTr13 can be corrected, and the inspection target T can be detected without depending on the temperature change of the LED 11 and the PTr13.
[0034]
Further, in the paper sheet detection apparatus 1, as described above, the supply current value to the LED 11 when the PTr 13 detects the measurement light in the state where the paper sheet as the inspection target T does not exist, and Since the supply current value to the LED 11 when the PTr 13 detects the measurement light in the state where the paper sheet as the inspection target T is present is obtained based on a statistical method, it is stored in the storage unit 21 in advance. An appropriate ratio can be obtained.
[0035]
The present invention is not limited to the above-described embodiment, and the light detection device according to the present invention is not limited to the above-described paper as long as it irradiates the measurement object T with the measurement light and detects the measurement light. The present invention can also be applied to devices other than the leaf detection device 1. Further, the light projection wavelength band of the LED 11 and the light reception wavelength band of the PTr 13 are appropriately selected and set according to the type, material, etc. of the inspection target T.
[0036]
Further, in the present embodiment, the supply current value to the LED 11 when the PTr 13 detects the measurement light in the state where the paper sheet as the inspection target T does not exist, and the paper sheet as the inspection target T Although the supply current value to the LED 11 when the PTr 13 detects the measurement light in a state where there is a kind is obtained based on a statistical method, the present invention is not limited to this, and is obtained based on a single measurement. Also good.
[0037]
Further, in the present embodiment, the minimum value “A” of the supply current value to the LED 11 in the sample frequency distribution FD2 as the supply current value to the LED 11 when the LED 11 detects the measurement light in the presence of the paper sheet. However, the present invention is not limited to this. For example, a value larger than the minimum value “A” by a predetermined value may be selected.
[0038]
【The invention's effect】
As described above in detail, according to the present invention, even when the light detection device is used, the light emission output of the light emitting element and the variation in detection sensitivity of the light receiving element for each product, the correction of the characteristic change, and the like can be reliably performed. A photodetection device that can be appropriately performed can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a paper sheet detection apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram for explaining a function of a control unit included in the paper sheet detection apparatus according to the embodiment of the present invention.
FIG. 3 is a diagram showing the relationship between the ambient temperature of the LED and PTr and the temperature correction coefficient.
FIG. 4 is a diagram showing a frequency distribution of a supply current value to an LED.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Paper sheet detection apparatus, 11 ... Light emitting diode (LED), 13 ... Phototransistor (PTr), 15 ... Temperature sensor, 20 ... Control unit part, 21 ... Memory | storage part, 23 ... Correction | amendment part, 25 ... Supply current value Detection unit, 27... Supply current value determination unit, 29... Supply current value control unit, T.

Claims (3)

A light emitting element for irradiating the object to be inspected with measurement light;
A light receiving element for detecting the measurement light from the light emitting element;
A supply current value to the light emitting element when the light receiving element detects the measurement light in a state where the inspection target does not exist, and the light receiving element in the state where the inspection target exists Storage means for storing in advance a ratio of the current supplied to the light emitting element when detected;
Supply current value for detecting the supply current value to the light emitting element when the measurement light is output from the light emitting element at a predetermined timing when the inspection target does not exist and the light receiving element detects the measurement light Detection means;
Supply current value determining means for determining a supply current value to the light emitting element based on the supply current value detected by the supply current value detecting means and the ratio stored in advance in the storage means;
And a supply current value control unit configured to control the supply current value to the light emitting element to be the supply current value determined by the supply current value determination unit. A temperature sensor for detecting the ambient temperature of the light emitting element;
Correction means for correcting the ratio stored in advance in the storage means based on the ambient temperature detected by the temperature sensor;
The supply current value determining means determines a supply current value to the light emitting element based on the supply current value detected by the supply current value detection means and a ratio corrected by the correction means. The photodetecting device according to claim 1. The supply current value to the light emitting element when the light receiving element detects the measurement light in a state where the inspection target does not exist is the light supply element that supplies the measurement light in the state where the inspection target does not exist. Measured multiple times the supply current value to the light emitting element when detected, is determined based on a statistical method,
The supply current value to the light emitting element when the light receiving element detects the measurement light in a state where the inspection target exists is present for each of the plurality of inspection target objects. 3. The method according to claim 1, wherein the supply current value to the light emitting element is measured when the light receiving element detects the measurement light in a state, and is obtained based on a statistical method. Light detection device.

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