JP2002214360A - Photodetector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photodetector making allowing appropriate adjustment of variations in the emission output of a light emitting element among products and correction of the temperature characteristic of the light emitting element even in the absence of the subject of inspection. SOLUTION: A detection control portion 41 causes a LED 14 to emit a primary light beam before a paper sheet reaches a position where the LED 14 with the paper sheet inserted therein emits the primary light beam, based on a signal output from a main control portion 51, and reads the value of a voltage output from a second PD 16 and a value of adjustment reference data stored in an EEPROM 45. The detection control portion 41 controls the operation of an LED drive circuit portion 43 so that the value of the voltage output from the second PD 16 coincides with the value of the adjustment reference data. Once the paper sheet has reached the position where the primary light beam is applied thereto from the LED 14, the detection control portion 41 causes the LED 14 to emit the primary light beam while controlling the operation of the LED drive circuit portion 43 so that the value of the voltage output from the second PD 16 coincides the value of the adjustment reference data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photodetector for irradiating primary light to an object to be inspected and detecting secondary light emitted from the object to be inspected.

[0002]

2. Description of the Related Art Conventionally, banknotes, voting tickets for horse races and horse races,
In order to discriminate the authenticity of paper sheets such as securities, when these paper sheets are irradiated with primary light (excitation light) in a predetermined wavelength band, a secondary wavelength band different from the primary light is used. A material that emits light (fluorescent ink, etc.) is applied, and a discriminating apparatus for discriminating the authenticity of a sheet is irradiated with primary light to an object to be inspected to be inspected. A light detection device for detecting secondary light emitted from the object is provided. According to this discriminating apparatus, it is possible to discriminate the authenticity of the paper sheet by irradiating the paper sheet with the excitation light and detecting the presence or absence of the fluorescence of the ink which is the secondary light in the light detection apparatus. Become.

[0003]

By the way, the light output of the light emitting element for irradiating the sheet with the excitation light in the photodetector has a variation (luminance variation) for each product. For this reason, for example, when the light emission output of the light emitting element is low, the output of the emitted secondary light also becomes low, and it becomes difficult to appropriately detect the secondary light with the photodetector. As a result, even when ink is applied to the paper sheet, there is a possibility that the paper sheet may be erroneously determined to be fake.
In addition, the characteristics of the light emission output of the light emitting element may change depending on the temperature, and it is difficult to properly detect the secondary light with the light detection device as in the case where there is variation among products. turn into.

In a photodetector, a light receiving element is usually configured to selectively receive secondary light. For this reason, it is difficult for the light receiving element to detect the state of the light emission output of the light emitting element. In order to adjust the variation of each product and correct the temperature characteristics of the light emitting element as described above, ink is applied. It is necessary to irradiate excitation light from the light emitting element in the presence of the used paper sheets. Therefore, it is difficult to adjust the variation of the light emission output of the light emitting element for each product, correct the temperature characteristic of the light emitting element, and the like in advance in a state where no paper sheet exists.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and even when no inspection object is present, it is possible to reliably adjust the variation in the light emission output of the light emitting element for each product, correct the temperature characteristic of the light emitting element, and the like. It is another object of the present invention to provide a photodetector that can be appropriately performed.

[0006]

A light detecting device according to the present invention comprises a light emitting element for irradiating an object to be inspected with primary light having a predetermined wavelength band, and a light emitting element for irradiating the primary light. A first light receiving element for receiving secondary light emitted from the object to be inspected, a second light receiving element provided near the light emitting element for receiving primary light emitted from the light emitting element, and light emission of the light emitting element Adjusting means for adjusting the output; storage means for storing adjustment reference data relating to the signal output of the second light receiving element;
The primary light is emitted from the light emitting element, the adjustment reference data stored in the storage means and the signal output from the second light receiving element are read, and the signal output from the second light receiving element is read as the adjustment reference data. And control means for controlling the operation of the adjusting means so as to coincide with each other.

In the photodetector according to the present invention, the second light receiving element is provided in the vicinity of the light emitting element, and adjustment reference data relating to the signal output of the second light receiving element is stored in the storage means. Then, the control means emits primary light from the light emitting element, and controls the operation of the adjusting means such that the signal output from the second light receiving element coincides with the adjustment reference data stored in the storage means. The light emission output of the light emitting element is adjusted. As a result, the light emission output of the light emitting element is adjusted based on the adjustment reference data, and it is possible to suppress the light emission output of the light emitting element from being varied from product to product, and to suppress the light emitting element due to a temperature change or the like. The change of the light emission output can be corrected.

Further, in the photodetector according to the present invention, not the first light receiving element for receiving the secondary light but the signal output of the second light receiving element for receiving the primary light emitted from the light emitting element. The control means controls the operation of the adjusting means to adjust the light emission output of the light emitting element. For this reason, even when the inspection object does not exist, it is possible to adjust the variation of the light emission output for each product, correct the temperature characteristic of the light emitting element, and the like.

As a result, in the photodetector according to the present invention, even when the object to be inspected does not exist,
Adjustment of the variation of the light emission output of the light emitting element for each product, correction of the temperature characteristic of the light emitting element, and the like can be reliably and appropriately performed, and the detection of the secondary light can be accurately performed.

In addition, the apparatus further comprises detecting means for detecting that the object to be inspected has been inserted, wherein the control means detects that the object to be inspected emits primary light from the light emitting element based on an output from the detecting means. Before reaching the position to be illuminated, 1
The next light is emitted, the adjustment reference data stored in the storage means and the signal output from the second light receiving element are read, and the signal output from the second light receiving element is matched with the adjustment reference data. By controlling the operation of the adjusting means, when the object to be inspected reaches the position where the primary light is emitted from the light emitting element, the signal output from the second light receiving element is adjusted to match the adjustment reference data. Preferably, the primary light is emitted from the light emitting element while the operation of the means is controlled. In such a configuration, the primary light is emitted from the light emitting element in a state where the variation of the light emitting output of the light emitting element for each product is adjusted, the temperature characteristic of the light emitting element is corrected, and the like for each inspection object. be able to. As a result, it is possible to detect the secondary light with higher accuracy without causing a variation for each inspection object.

The light-emitting element comprises a light-emitting diode, the first light-receiving element comprises a first photodiode, and the second light-receiving element comprises a second photodiode. The current is adjusted, the storage means stores adjustment reference data relating to the output voltage value of the second photodiode, and the control means emits primary light from the light emitting diode and is stored in the storage means. It is preferable that the adjustment reference data and the output voltage value of the second photodiode are read, and the operation of the adjustment means is controlled so that the output voltage value of the second photodiode matches the adjustment reference data. With this configuration, even when a light emitting diode that is inexpensive and has a large variation in light emitting output is used as the light emitting element, it is possible to reliably adjust the variation in the light emitting output of the light emitting diode for each product and correct the temperature characteristics of the light emitting diode. And it can be performed appropriately. As a result, the cost of the photodetector can be reduced without lowering the detection accuracy of the secondary light.

Preferably, the storage means is a non-volatile memory. Since the storage means is a non-volatile memory, a third party cannot easily change the adjustment reference data. As a result, it is possible to prevent the detection accuracy of the secondary light from deteriorating due to mischief by a third party or the like.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the photodetector according to the present invention will be described below in detail with reference to the drawings. In each of the drawings, the same elements are denoted by the same reference numerals, and description thereof is omitted. In the present embodiment, an example in which the present invention is applied to a paper sheet discriminating apparatus will be described.

First, a configuration of a paper sheet discriminating apparatus according to an embodiment of the present invention will be described with reference to FIG. Figure 1
1 is a schematic sectional view showing a paper sheet discriminating apparatus according to the present embodiment.

The paper sheet discriminating apparatus 1 has an upper frame 2 and a lower frame 3. The transport path 4 for the paper sheets T is
The upper frame 2 is composed of the lower surface 2a of the upper frame 2 and the upper surface 3a of the lower frame 3. By fixing the upper frame 2 and the lower frame 3 in contact with each other, the mating surface between the upper frame 2 and the lower frame 3 is formed. It is formed. An insertion port 5 for inserting a paper sheet T is provided at one end of the transport path 4.
Discharge ports 6 for discharging paper sheets T are provided on the other end side. The insertion port 5 and the discharge port 6 are constituted by a lower surface 2 a of the upper frame 2 and an upper surface 3 a of the lower frame 3, similarly to the transport path 4. In the vicinity of the insertion slot 5, an insertion sensor (detection means) 7 for detecting the insertion of the paper sheet T from the insertion slot 5 is provided. A known photoelectric sensor or the like can be used as the insertion sensor 7, and the insertion sensor 7 outputs an ON signal when the paper sheet T is inserted from the insertion slot 5. In FIG. 1, a fluorescent material (such as a fluorescent ink) P that emits secondary light having a wavelength band different from the primary light when primary light (excitation light) in a predetermined wavelength band is irradiated on the surface thereof is applied. This shows a state in which the paper sheet T is inserted into the paper sheet discriminating apparatus 1 and is being transported in the transport path 4.

Above the transport path 4, there is provided a light detecting unit (light detecting device) 11 for irradiating the sheet T conveyed on the transport path 4 with primary light and detecting secondary light. ing.
The light detection unit 11 is fixed while being disposed above the upper frame 2. At a position corresponding to the light detection unit 11 of the upper frame 2, a detection hole 2b for transmitting the primary light from the light detection unit 11 and the secondary light from the paper sheet T (fluorescent material P) is formed. ing.

The light detecting unit 11 has a housing 12 and a first substrate 13 as shown in FIGS. This housing 12 is fixed to a first substrate 13.
In a space defined by the housing 12 and the first substrate 13, a light emitting diode (LED) 14 as a light emitting element and a first photodiode (first PD) as a first light receiving element
15, a second photodiode (second PD) 16 as a second light receiving element, and a second substrate 17 are provided. As shown in FIG. 1, the light detection unit 11
The ED 14 is disposed on the front side when viewed in the transport direction of the paper sheet T,
The first PD 15 is fixed to the upper frame 2 in a state where the first PD 15 is disposed on the rear side when viewed in the transport direction of the paper sheet T. First substrate 13
Is provided with a terminal portion 13a for inputting and outputting a signal to and from the first substrate 13.

The LED 14 generates primary light having a predetermined wavelength band in order to emit secondary light from the fluorescent material P applied to the paper sheet T, and outputs the primary light having a predetermined wavelength band. Irradiates T (fluorescent material P). LED1
4 is fixed while being electrically connected to the first substrate 13. The LED 14 emits 1
The optical axis of the next light (light projection optical axis) is disposed at a predetermined angle (for example, about 45 °) with respect to the paper sheet T to be conveyed. An aperture 18 is provided in front of the LED 14.

The first PD 15 receives the secondary light emitted from the fluorescent material P applied to the paper sheet T by the irradiation of the primary light. The first PD 15 is disposed so that the light receiving optical axis of the first PD 15 is substantially orthogonal to the paper sheet T to be conveyed. By arranging the LED 14 at a predetermined angle and arranging the first PD 15 substantially perpendicular to the paper sheet T, it is possible to prevent specular reflected primary light from being incident on the first PD 15. become. An SC filter 19 and an interference filter 20 are provided in front of the first PD 15. SC filter 19 and interference filter 20
Is for removing light (disturbance light and primary light) in a wavelength band other than the secondary light so that the light does not enter the first PD 15.

The second PD 16 is for receiving the primary light emitted from the LED 14. The second PD 16
The light sensitive area is disposed on the side of the LED 14 such that the light sensitive area is located near the tip of the LED 14. 1st PD
The 15 and the second PD 16 are fixed while being electrically connected to the second substrate 17.

As shown in FIG. 1, the paper sheet discriminating apparatus 1 is provided with various rollers for transport vertically above and below the transport path 4. The rollers sandwich the light detection unit 11 in the transport direction of the paper sheet T in the transport path 4, and a part of the rollers in the order of the first feed roller 21 and the second feed roller 22 from the insertion port 5 side of the transport path 4. Are provided so as to face the transport path 4.

Next, based on FIG.
Will be described. FIG. 4 is a block diagram of the paper sheet discriminating apparatus 1 in the present embodiment.

The output from the first PD 15 is connected to a current-voltage conversion circuit section (IV conversion circuit section) 31. The IV conversion circuit unit 31 converts a value of a current flowing when the first PD 15 receives light into a voltage signal. I
The output of the V conversion circuit unit 31 is connected to the amplifier circuit unit 32. The amplification circuit section 32 is for amplifying the output signal output from the IV conversion circuit section 31. Second
The output from the PD 16 is connected to a current-voltage conversion circuit section (IV conversion circuit section) 33. The IV conversion circuit unit 33
This is for converting a value of a current flowing when the second PD 16 receives light into a voltage signal. These IV conversion circuit section 31, amplification circuit section 32, and IV conversion circuit section 33
Are formed on the second substrate 17 as a known analog circuit. The outputs of the amplification circuit section 32 and the IV conversion circuit section 33 are connected to a detection control section 41 as control means.

The detection control unit 41 includes the light detection unit 1
1 is a processing unit that performs overall signal processing and the like, and includes a central processing unit (CPU), a ROM, a RAM, and the like (not shown). The detection control unit 41 performs an operation according to a control program stored in advance, thereby
PWM (Plus) for controlling the light emission output (luminance)
A Width Modulation control signal is output to the LED drive circuit unit (adjustment means) 43 to control the operation of the LED drive circuit unit 43. It is connected to a main control unit 51 that controls signal processing and the like of the entire sheet discriminating apparatus 1.

The LED drive circuit unit 43 includes a detection control unit 41
LED 14 based on the PWM control signal output from
Adjust the light emission output of The LED drive circuit unit 43
The M control signal is converted into a DC voltage signal, and a current proportional to the DC voltage signal is generated and supplied to the LED 14.
When the pulse width of the PWM control signal changes, LE
The value of the current supplied to D14 changes, and L
The light emission output of the ED 14 will change.

The main control unit 51 determines the authenticity of the paper sheet T inserted into the paper sheet discriminating apparatus 1 based on the output signal from the detection control unit 41, and notifies the determination result. The output of the insertion sensor 7 is connected to the main control unit 51. The main control unit 51 outputs to the detection control unit 41 a signal capable of identifying whether or not the sheet T has been inserted, based on the output signal from the insertion sensor 7.

The detection control section 41 is connected to an EEROM 45 as storage means (non-volatile memory). The adjustment reference data (the value of the voltage signal) relating to the signal output of the second PD 16 and the threshold data (the value of the voltage signal) relating to the signal output of the first PD 15 are written into the EEROM 45 at the time of shipment of the light detection unit 11. It is memorized. The detection control unit 41 writes the adjustment reference data and the threshold data into the EEPROM 45 and
5 to read the stored adjustment reference data and threshold data. Note that the above-described detection control unit 41, LED drive circuit unit 43, and EEPROM 45
Are formed on the second substrate 17.

Here, the EEROM 45 at the time of shipment is
The procedure for reading the adjustment reference data into the memory will be described. First, at a predetermined temperature (for example, 25 ° C.), the standard paper sheet for inspection is measured by the light detection unit 11. At this time, an external signal is sent to the detection control unit 41,
The detection control unit 41 outputs a PWM control signal to the LED drive circuit unit 43 so that the output voltage of the first PD 15 converted by the IV conversion circuit unit 31 has a predetermined voltage value.
The value of the current supplied to the LED 14 is adjusted. Then, the first PD 15 (amplifying circuit unit 32) is detected by the detection control unit 41.
When the output voltage of the second PD 16 reaches a predetermined voltage value
The value of the output voltage of the (IV conversion circuit unit 33) is written and stored in the EEPROM 45 as adjustment reference data.

Next, the light detection unit 11 (the detection control unit 4)
The detection processing operation executed in 1) will be described based on the flowchart shown in FIG. This detection processing operation is executed based on a control program stored in the ROM.

First, in S101, the detection control unit 41
It is determined whether or not an output signal indicating that the sheet T has been inserted into the sheet discriminating apparatus 1 has been output from the main control unit 51. When an output signal indicating that the sheet T has been inserted is output from the main control unit 51 (“Ye
s "), and then proceeds to S103. When the output signal indicating that the paper sheet T is inserted is not output from the main control unit 51 (“No” in S101), the process returns, and the paper sheet T is inserted from the main control unit 51. It waits until an output signal indicating this is output.

In step S103, the detection control unit 41
The adjustment reference data stored in the EEPROM 45 is read. In subsequent S105, the detection control unit 41 outputs a PWM control signal to the LED drive circuit unit 43 to turn on the LED 14 before the inserted sheet T reaches the irradiation position of the primary light from the LED 14. Thereby, the paper sheet T
The primary light is emitted from the LED 14 in a state where no LED exists, and is irradiated on the upper surface 3 a of the lower frame 3 below the light detection unit 11. When the LED 14 is turned on, S10
At 7, the detection control unit 41 reads the value of the output voltage of the second PD 16 (IV conversion circuit unit 33).

When the value of the output voltage of the second PD 16 is read, the process proceeds to S109, where the detection control unit 41
5 and the value of the adjustment reference data read from the second PD 16
To determine whether these values match. Adjustment reference data value and second PD 16
Is equal to the output voltage value (“Ye” in S109).
s "), and proceeds to S111, where the detection control unit 41 sets the first PD
15 (amplifier circuit section 32).

In S113, the detection controller 41 compares the value of the output voltage of the first PD 15 with the value of the threshold data read from the EEPROM 45, and the value of the output voltage of the first PD 15 is larger than the value of the threshold data. It is determined whether or not. If the value of the output voltage of the first PD 15 is greater than the value of the threshold data (“Yes” in S113), the process proceeds to S115, and the detection control unit 41 determines that the value of the output voltage of the first PD 15 is greater than the value of the threshold data. A signal indicating the effect is output. On the other hand, if the value of the output voltage of the first PD 15 is equal to or less than the value of the threshold data (“No” in S113), the process proceeds to S11.
Proceeding to 7, the detection control unit 41 outputs a signal indicating that the value of the output voltage of the first PD 15 is equal to or smaller than the value of the threshold data.

When the fluorescent material P is applied to the inserted paper sheet T, the secondary light is emitted by the irradiation of the primary light from the LED 14, so that the value of the output voltage of the first PD 15 becomes the threshold value. It is larger than the value of the data. Therefore, when a signal indicating that the value of the output voltage of the first PD 15 is greater than the value of the threshold data is output from the detection control unit 41, the main control unit 51 determines that the regular paper sheet coated with the fluorescent material P is Assuming that T has been inserted, it is determined that the inserted paper sheet T is genuine.

On the other hand, if the fluorescent material P is not applied to the inserted paper sheet T, or if the inserted paper sheet T
If any paper sheet is attached to the first PD 15, the secondary light is not emitted, or the intensity of the secondary light is low, so that the output voltage value of the first PD 15 becomes equal to or less than the threshold data value. Therefore, the main control unit 51 performs the detection control unit 41
Outputs a signal indicating that the value of the output voltage of the first PD 15 is equal to or less than the value of the threshold data, it is determined that the inserted sheet T is fake.

By the way, the value of the adjustment reference data and the second P
When the value of the output voltage of D16 does not match (“No” in S109), the process proceeds to S119, and the detection control unit 41 determines whether the value of the output voltage of the second PD 16 is larger than the value of the adjustment reference data. to decide. When the value of the output voltage of the second PD 16 is larger than the value of the adjustment reference data (“Yes” in S119), the process proceeds to S121. In S121, the detection control unit 41 outputs a PWM control signal to the LED drive circuit unit 43 so as to reduce the emission output of the LED 14, and returns to S107.

On the other hand, when the value of the output voltage of the second PD 16 is smaller than the value of the adjustment reference data ("N" in S119).
o "), and proceeds to S123. In S123, the detection control unit 4
1 is an LE so as to increase the emission output of the LED 14.
A PWM control signal is output to the D drive circuit unit 43, and S10
Return to 7. S107 until the value of the output voltage of the second PD 16 matches the value of the adjustment reference data.
The steps of S109, S119, S121, and S123 will be repeated.

Next, the operation of the light detection unit 11 will be described with reference to FIGS.

When the insertion sensor 7 detects the paper sheet T, an output signal (Low Level signal) indicating that the paper sheet T has been inserted is sent from the main control unit 51 as shown in FIG. Output to the detection control unit 41. When a Low Level signal indicating that the paper sheet T is inserted is output from the main control unit 51, the detection control unit 41 sends a P signal to the LED drive circuit unit 43.
The WM control signal is output, and the LED 14 is turned on to emit primary light, as shown in FIG. At this time, since the sheet T has not reached the irradiation position of the primary light from the LED 14, the primary light is applied to the upper surface 3 a of the lower frame 3 below the light detection unit 11.

Then, the primary light emitted from the LED 14 is received by the second PD 16, and the value of the output voltage of the second PD 16 (IV conversion circuit unit 33) is read into the detection control unit 41. The read value of the output voltage of the second PD 16 is
The value of the adjustment reference data stored in the EEPROM 45 is compared with the value of the adjustment reference data, and the detection control unit 41 determines that the output voltage of the second PD 16 matches the value of the adjustment reference data.
When a PWM control signal is output to the ED drive circuit 43,
The emission output of the ED 14 is adjusted.

For example, when the light emitting output of the LED 14 is small and the value of the output voltage of the second PD 16 is smaller than the value of the adjustment reference data, the current supplied to the LED 14 is adjusted so that the light emitting output of the LED 14 becomes large. You. Thereby, as shown in FIG. 6C, the second PD 16
Is larger than the value at the start of the lighting of the LED 14, and is in a state in which it matches the value of the adjustment reference data. As described above, the emission output of the LED 14 is controlled so that the value of the output voltage of the second PD 16 matches the value of the adjustment reference data. Before reaching the light irradiation position, the reference data for adjustment is set to EER when the light detection unit 11 is shipped.
The same state as the state adjusted for writing to the OM 45 (the state in which light emission is output at 25 ° C.) is maintained.

When the sheet T reaches the irradiation position of the primary light from the LED 14, first, light scattered on the surface of the sheet T enters the first PD 15 and is received, and the output voltage of the first PD 15 is received. Rises as shown in FIG. 6 (d). Then, when the portion where the fluorescent material P is applied reaches the irradiation position of the primary light, secondary light is emitted from the fluorescent material P, and the secondary light is received by the first PD 15. When the secondary light is received by the first PD 15, the first P
The value of the output voltage of D15 rises significantly from the value of the output voltage when the primary light is applied to the surface of the paper sheet T (the portion where the fluorescent material P is not applied).

When the value of the output voltage of the first PD 15 is equal to
When the value becomes larger than the threshold data value stored in M45, as shown in FIG. 6E, a signal (High Level signal) indicating that the output voltage value of the first PD 15 is larger than the threshold data value. Is output from the detection control unit 41 to the main control unit 51.

At the timing when the sheet T has passed the position below the light detection unit 11, the output of the Low Level signal is stopped (it becomes High Level), and the LED 14 is turned off as shown in FIG. I do. As described above, the LED 14 is turned on when the paper sheet T is inserted and passes below the light detection unit 11, and the measurement of the paper sheet T is completed, and the state where the paper sheet T is not inserted. By turning off the LED 14, the lighting time of the LED 14 can be shortened, and the life of the LED 14 can be extended.

As described above, in the present embodiment, the second
The PD 16 is provided near the LED 14, and adjustment reference data relating to the signal output (output voltage) of the second PD 16 (IV conversion circuit unit 33) is stored in the EEPROM 45. Then, the detection control unit 41 controls the LED 1
4 emits primary light, and controls the operation of the LED drive circuit 43 so that the value of the output voltage from the second PD 16 matches the value of the adjustment reference data stored in the EEPROM 45. The output will be adjusted. As a result, the light emission output of the LED 14 is adjusted based on the adjustment reference data.
It is possible to suppress a variation in the light emission output of each LED (light detection unit 11) in each product (light detection unit 11), and to correct a change in the light emission output of the LED 14 due to a temperature change or the like.

The second PD for receiving the primary light emitted from the LED 14 is not the first PD 15 for receiving the secondary light.
Based on the signal output of the PD 16, the detection control unit 41
The operation of the D drive circuit unit 43 is controlled to adjust the light emission output of the LED 14. Therefore, the state in which the sheet T does not exist (the state before the sheet T reaches the irradiation position of the primary light)
Even in this case, it is possible to adjust the variation of the LED 14 for each light detection unit 11, correct the temperature characteristic of the LED 14, and the like. Further, regardless of the wavelength band of the secondary light, for example, even when the wavelength band of the primary light and the wavelength band of the secondary light are close, the emission output of the LED 14 can be surely adjusted.

As a result, in the light detection unit 11 according to the present embodiment, the paper T
Even when the LED does not exist, the variation of the emission output of the LED 14 for each light detection unit 11 is adjusted,
Correction of the temperature characteristic of No. 4 can be performed reliably and appropriately, and detection of secondary light by the first PD 15 can be performed with high accuracy.

Further, based on the output from the main control unit 51 (the result of detection by the insertion sensor 7), the detection control unit 41 determines whether or not the paper sheet T reaches the position where the primary light is emitted from the LED 14. , The primary light is emitted from the LED 14 and the second PD
16 (IV conversion circuit 33) and EE
The value of the adjustment reference data stored in the ROM 45 is read, and the operation of the LED drive circuit unit 43 is controlled so that the value of the output voltage from the second PD 16 matches the value of the adjustment reference data. When the LED reaches the position where the primary light is emitted from the LED 14, the operation of the LED drive circuit unit 43 is controlled such that the value of the output voltage from the second PD 16 matches the value of the adjustment reference data. LED14 to 1
By irradiating the next light, LED 1
The primary light can be emitted from the LED 14 in a state where the variation of the light emission output of 4, the correction of the temperature characteristic of the LED 14, and the like have been performed. As a result, the detection of the secondary light by the first PD 15 can be performed with higher accuracy without causing a variation between the sheets T.

Further, according to the present embodiment, even when the LED 14 which is inexpensive and has a large variation in the light output is used as the light emitting element, the variation in the light output of the LED 14 for each light detection unit 11 can be adjusted, and the temperature characteristics of the LED 14 can be improved. Can be surely and appropriately performed. As a result, the cost of the light detection unit 11 can be reduced without lowering the detection accuracy of the secondary light in the first PD 15.

Further, in this embodiment, since the EEPROM 45 which is a nonvolatile memory is used as the storage means,
A third party cannot easily change the adjustment reference data. As a result, the first PD 15
This can prevent the detection accuracy of the secondary light from deteriorating.

The light detection unit 1 according to the present embodiment
In 1, the variation control of the light emission output of the LED 14 in each light detection unit 11, the correction of the temperature characteristic of the LED 14, and the like are executed by digital control by the detection control unit 41. In comparison with the above-mentioned ones that perform the variation adjustment and correction,
A space for mounting a hardware circuit is not required, and the size of the light detection unit 11 can be reduced. Further, according to the present embodiment, there is no need to consider problems such as long-term stabilization of the volume adjustment resistance value and improvement in reliability that occur when an electronic volume is used.
The adjustment of the variation of the light emission output and the correction of the temperature characteristic of the LED 14 can be performed very easily.

Further, in the present embodiment, as described above, the variation control of the light emission output of the LED 14 for each light detection unit 11, the correction of the temperature characteristic of the LED 14, and the like are executed by the detection control unit 41 under digital control. Therefore, even when the lighting time of the LED 14 (the time until the inserted paper sheet T reaches the irradiation position of the primary light) is short, the light emission output of the LED 14 can be surely adjusted.

The present invention is not limited to the above-described embodiment. The photodetector according to the present invention irradiates primary light to an object to be inspected, and emits secondary light emitted from the object to be inspected. If the device for detecting the
It is also possible to apply to other devices. Also, L
The emission wavelength band of ED14 (wavelength band of primary light), 1st P
The light receiving wavelength bands of the D15 and the second PD 16 are appropriately selected and set according to the characteristics of the fluorescent material P used.

[0054]

As described above in detail, according to the present invention, even when the inspection object does not exist, the variation of the light emission output of the light emitting element for each product and the temperature characteristic correction of the light emitting element are corrected. And the like can be provided reliably and appropriately.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a paper sheet discriminating apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic bottom view showing a light detection unit included in the paper sheet discriminating apparatus according to the embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view showing a light detection unit included in the paper sheet discriminating apparatus according to the embodiment of the present invention.

FIG. 4 is a block diagram showing a paper sheet discriminating apparatus according to the embodiment of the present invention.

FIG. 5 is a flowchart showing a detection processing operation in a light detection unit included in the paper sheet discriminating apparatus according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating an operation of a light detection unit included in the paper sheet discrimination device according to the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Paper discrimination apparatus, 7 ... Insertion sensor, 11 ... Light detection unit, 13 ... 1st board | substrate, 14 ... Light emitting diode (LE
D), 15 ... first photodiode (first PD), 1
6 ... second photodiode (second PD), 17 ... second
Substrate, 41: detection control unit, 43: LED drive circuit unit, 4
5: EEROM, 51: main control unit, P: fluorescent material, T:
Paper sheets.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G07D 7/12 G01V 9/04 U F term (reference) 2G043 AA04 BA14 CA07 DA02 DA05 EA01 FA01 GA06 GA08 GA21 GB11 GB21 LA01 MA11 NA01 NA06 2G065 AB11 AB28 BA09 BC14 BC21 BC33 CA21 DA05 DA15 3E041 AA01 AA03 BA09 BA20 BB03 CB07

Claims (4)

[Claims] 1. A light emitting element for irradiating a primary light having a predetermined wavelength band to an inspection object, and a secondary light emitted from the inspection object by irradiating the primary light. A first light receiving element that receives light, a second light receiving element that is provided near the light emitting element and receives the primary light emitted from the light emitting element, and an adjustment unit that adjusts a light emission output of the light emitting element. A storage unit for storing adjustment reference data related to a signal output of the second light receiving element; and emitting the primary light from the light emitting element, and adjusting the adjustment reference data stored in the storage unit and the second reference light. Control means for reading the signal output from the second light receiving element and controlling the operation of the adjusting means so that the signal output from the second light receiving element coincides with the adjustment reference data. Featured light detection Location. 2. The apparatus according to claim 1, further comprising a detection unit configured to detect that the inspection target is inserted, wherein the control unit is configured to detect the insertion of the inspection target from the light emitting element based on an output from the detection unit. Before reaching the position where the primary light is irradiated, the primary light is emitted from the light emitting element, and the adjustment reference data stored in the storage means and the signal output from the second light receiving element are output. Is read, and the operation of the adjusting means is controlled so that the signal output from the second light receiving element matches the adjustment reference data, and the object to be inspected is the primary light from the light emitting element. When the operation of the adjusting means is controlled such that the signal output from the second light receiving element coincides with the adjustment reference data when the irradiation position is reached, the light emitting element is used for the primary light emitting element. Irradiating light Light detecting device according to claim 1, symptoms. 3. The light-emitting element comprises a light-emitting diode; the first light-receiving element comprises a first photodiode; the second light-receiving element comprises a second photodiode; The supply current to the light emitting diode is adjusted, the storage unit stores adjustment reference data relating to the output voltage value of the second photodiode, and the control unit transmits the primary light from the light emitting diode. The light is emitted and the adjustment reference data and the output voltage value of the second photodiode stored in the storage unit are read, and the output voltage value of the second photodiode matches the adjustment reference data. The photodetector according to claim 1, wherein the operation of the adjusting unit is controlled as described above. 4. The photodetector according to claim 1, wherein the storage unit is a nonvolatile memory.