JP2002148353A - Photo detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photo detector which is hardly affected by disturbance light and hard to cause intentional malfunction. SOLUTION: Light is emitted form a light emitting element 1, and the emitted light is reflected by the detected object 2 to enter a photo detecting element 2. According to the output of the photo detecting element 3, the existence/ absence of the detected object 2 is determined. The light emitting timing of the light emitting element 1 and the photo detecting timing of the photo detecting element 3 are compared, and when both timings are synchronized, the determination result is taken to be effective. As the cycle of the light emitting timing of the light emitting element 1 varies, the light of an inverter- contained luminaire is not synchronized with the variable period, so that wrong detection is not caused by the light of the luminaire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a light detecting device for detecting an object to be detected using light.

[0002]

2. Description of the Related Art A photodetection device of this kind is applied to, for example, a pachinko game machine, a copying machine, etc., and detects a pachinko ball, paper, or the like. In this device, the light of the light emitting element is applied to the pachinko ball or paper, the reflected light is received by the light receiving element, and the presence or absence of the pachinko ball or paper is detected based on the output of the light receiving element. This is called a reflection-type photodetector. Alternatively, the light from the light emitting element is made incident on the light receiving element, the light incident on the light receiving element is blocked by a pachinko ball or paper, and the presence or absence of the pachinko ball or paper is detected based on the output of the light receiving element at this time. . This is referred to as a blocking type photodetector.

Incidentally, in such a photodetector, malfunction may be caused due to the incidence of disturbance light on the light receiving element. For this reason, in the conventional apparatus, the light-emitting element emits light at a constant period, and the output of the light-receiving element is detected in synchronization with the light-emitting element, thereby preventing erroneous detection of unsynchronized disturbance light (Japanese Patent Laid-Open No. Hei 6 (1994) -106). -42963 and JP-A-8-1
84680).

[0004]

By the way, in recent years, luminaires which incorporate an inverter and turn on a light source at a high frequency have become widespread. This type of luminaire usually contains various frequency components in its light, instead of a single frequency component. For this reason, the light component of the lighting equipment may be synchronized with the light emission period of the light emitting element of the light detecting device, and when this light component enters the light emitting device of the light detecting device, a malfunction of the light detecting device occurs.

[0005] When the light emitting period of the light emitting element is constant, the light emitting period is easily detected. In a pachinko game machine, if the light emission cycle can be measured without permission and the light of the light emission cycle can be duplicated, the light of the light emission cycle can be externally transmitted for the purpose of injustice and intentionally inducing a malfunction. Irradiation is possible.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a photodetector which is hardly affected by disturbance light and hard to induce intentional malfunction. And

[0007]

In order to solve the above-mentioned problems, a photodetector according to the present invention has a light emitting element, a light receiving element for receiving light from the light emitting element, and a light emitting cycle of the light emitting element. The light emitting device includes a period changing unit and a synchronization detecting unit that detects an output signal of the light receiving element in synchronization with a light emitting period of the light emitting element.

According to the present invention having such a configuration, the light emitting cycle of the light emitting element is changed, and the output signal of the light receiving element is detected in synchronization with the changing light emitting cycle. Since the light emission cycle of this light emitting element fluctuates, it is almost impossible for disturbance light to synchronize with this light emission cycle. Therefore, malfunction of the light detection device hardly occurs due to disturbance light. Further, when the photodetection device of the present invention is applied to a pachinko game machine,
Since it is extremely difficult to irradiate light synchronized with the fluctuation period from the outside, it is possible to prevent fraud that intentionally causes a malfunction.

Further, in the present invention, the period changing means randomly changes the light emission period. Or
The period changing means changes the light emission period stepwise.
Further, the cycle changing means includes a random number generating means for generating a random number, and based on the random number generated by the random number generating means,
The light emission cycle is varied. Further, the cycle changing means changes the light emission cycle based on a plurality of signals having different cycles. Further, the cycle varying means varies the light emission cycle based on a plurality of signals having different waveforms.

The light emission cycle can be varied by any of these methods.

Further, in the present invention, the period changing means changes the light emission period in response to an external signal.

This makes it possible to externally control the fluctuation of the light emission cycle.

The present invention further comprises a band-pass filter for passing an output signal of the light-receiving element corresponding to the light of the light-emitting element, and the synchronization detecting means inputs the output signal of the light-receiving element via the band-pass filter. are doing.

With such a band-pass filter, only the output signal of the light receiving element corresponding to the light of the light emitting element can be selected, and the output signal of the light receiving element corresponding to the disturbance light can be excluded. For example, it is possible to substantially eliminate light from a lighting apparatus that includes components of various frequencies.

Further, in the present invention, the frequency band of the band-pass filter is changed according to the change of the light emission cycle.

Here, since the frequency component of the light of the light emitting element fluctuates with the fluctuation of the light emitting cycle of the light emitting element, the frequency band of the band-pass filter is fluctuated, so that the light receiving element corresponding to the light of the light emitting element is always obtained. The output signal of the element is properly selected.

Further, in the present invention, the light emitting time of the light emitting element is set longer than 33 microseconds, and the high-frequency cutoff frequency of the band-pass filter is set corresponding to the light emitting time.

Generally, in a lighting fixture with a built-in inverter,
A frequency of 30 KHz or more is employed. For this reason,
In order to clearly distinguish the light from such a luminaire, the light emission time of the light emitting element may be set longer than 33 microseconds (the light emission frequency is set to less than 30 KHz). Frequency cut-off frequency (30K
(Less than Hz), the output signal of the light receiving element corresponding to the light of the light emitting element can be selected by the band-pass filter, and the output signal of the light receiving element corresponding to the light of the lighting fixture can be excluded.

Furthermore, in the present invention, when the synchronization detecting means detects the output signal of the light receiving element in synchronization with the light emitting cycle of the light emitting element, the synchronization detecting means latches the detected signal for a period equal to or longer than the light emitting cycle. Latch means is provided.

If the output signal of the light receiving element is latched by the latch means, the detection result of the photodetector can be easily confirmed.

Further, in the present invention, the period changing means and the synchronization detecting means are formed on the same integrated circuit.

As a result, the signal transmission path can be shortened, and the influence of disturbance noise is reduced.

Further, the present invention further includes an optical path for allowing light from the light emitting element to enter only the light receiving element.

If the light of the light emitting element is made incident only on the light receiving element, it becomes impossible to detect the light of the light emitting element from the outside and measure the light emission period. For example, in a pachinko game machine, it is impossible to externally measure the light emission cycle and imitate the light of the light emission cycle, and for the purpose of fraud and intentionally causing a malfunction, the light emission cycle is Light cannot be irradiated from outside.

[0025]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing one embodiment of the photodetector of the present invention. In the photodetector of the present embodiment, light is emitted from a light emitting element (light emitting diode) 1, this light is reflected by an object 2 to be detected, and is incident on a light receiving element (photodiode) 3. , The presence or absence of the detected object 2 is determined. Further, the light emission timing of the light emitting element 1 is compared with the light reception timing of the light receiving element 3, and when the two timings are synchronized, the determination result is regarded as valid.

The first and second oscillators 4 and 5 form respective oscillation signals having different frequencies from each other, and output these oscillation signals to the pulse variation circuit 6. The pulse variation circuit 6 generates a pulse signal P whose period varies based on each oscillation signal, and outputs the pulse signal P to the timing signal generation circuit 7. For example, the pulse variation circuit 6
Each of the oscillation signals is synthesized, and each time the level of the synthesized signal exceeds a preset threshold, a pulse signal P is generated and output.

The timing signal generating circuit 7 includes, for example, a 4-bit binary counter and a gate circuit.
Each time a 16-bit pulse signal P is input, the signal shown in FIG.
The light emitting element driving pulse signal of the light emitting element pulse driving circuit 8
Output to The light emitting element driving pulse signal in FIG.
The pulse width A is set to 1/16 of the cycle B. Since the cycle of the pulse signal P changes, the cycle B also changes.

Further, the timing signal generation circuit 7
The signal detection gate pulse signal shown in FIG. 2C, the noise detection gate pulse signal shown in FIG. 2E, and the shift register clock signal shown in FIG. 2H are formed, and these signals are output to the signal processing circuit 13.

The light emitting element pulse driving circuit 8 includes a switch circuit, a constant current circuit, and the like. When the light emitting element driving pulse signal shown in FIG. Add to 1. Thus, the light emitting element 1 emits light in synchronization with the fluctuation cycle of the light emitting element drive pulse signal in FIG.

When the object to be detected 2 is present, the light emitting element 1
Is reflected by the detected object 2 and is incident on the light receiving element 2. Thus, light synchronized with the light emitting element drive pulse signal is received by the light receiving element 2.

The output signal of the light receiving element 2 is
After being amplified by 0, it is input to the AC amplifier 11. The AC amplifier 11 removes a DC component and a low frequency component from an output signal of the light receiving element 2 and outputs a signal of a high frequency component. The comparator 12 compares the high-frequency component signal with a preset first threshold value, and outputs a high-level signal to the signal processing circuit 13 when the high-frequency component signal exceeds the first threshold value. In the comparator 12, once the signal of the high frequency component is equal to or higher than the first threshold and the output thereof is once set to the high level, the signal of the high frequency component is equal to or lower than the second threshold lower than the first threshold. It does not return its output to a low level. Due to the hysteresis characteristic of the output with respect to such an input, even if the level of the signal of the high frequency component is unstable near the first threshold, the output of the comparator 12 does not need to be switched frequently, and the chattering phenomenon can be prevented. it can.

The signal processing circuit 13 includes, for example, a signal detection gate circuit 13a and a noise detection gate circuit 1 as shown in FIG.
3b and a digital integration circuit 13c. The signal detection gate circuit 13a includes the timing signal generation circuit 7
2 (c) is input, and the output of the comparator 12 is sampled in synchronization with this signal and supplied to the digital integration circuit 13c. Thus, the output of the comparator 12 is sampled at the timing when the light emitting element 1 emits light. As is clear from the comparison between FIGS. 2 (i) and 2 (c), the signal detection gate pulse signal in FIG. 2 (c) is slightly delayed from the light emitting element drive pulse signal in FIG. 2 (i). The time of this delay is
The setting is made in consideration of the time required from the generation of the light emitting element drive pulse signal in FIG.

The digital integration circuit 13c includes, for example, a three-stage shift register. The output of the comparator 12 is sequentially accumulated in the shift register and shifted in synchronization with the shift register clock shown in FIG. A high-level signal or a low-level signal is output according to each signal level in the shift register. For example, when the high-level output of the comparator 12 is sampled three times consecutively in synchronization with the signal detection gate pulse signal of FIG.
When a high-level signal is output from the digital integration circuit 13c and the low-level output of the comparator 12 is sampled three times in succession, the digital integration circuit 1
A low level signal is output from 3c.

Further, the noise detection gate circuit 13b receives the noise detection gate pulse signal of FIG. 2 (e) from the timing signal generation circuit 7, samples the output of the comparator 12 in synchronization with this signal, and performs digital integration. It is given to the circuit 13c. Thus, the output of the comparator is sampled at the timing when the light emitting element 1 does not emit light. If the output of the comparator 12 sampled by the noise detection gate circuit 13b is at a high level, the digital integration circuit 13c initializes the shift register and outputs a low-level signal.

The signal from the signal processing circuit 13 is output to the outside through the output circuit 14. In addition, the constant voltage circuit 15
Supplies an operating voltage to each part of the photodetector.

Here, the first and second oscillators 4 and 5, a pulse variation circuit 6, a timing signal generation circuit 7, a light emitting element pulse drive circuit 8, a head amplifier 10, an AC amplifier 1
1, comparator 12, signal processing circuit 13, output circuit 1
4 and the constant voltage circuit 15 are formed on a one-chip integrated circuit. This is because, if these circuits are formed separately from each other, the circuit is susceptible to external noise and the influence of the capacitance component of the wire between the circuits becomes large. These circuits are mounted on a one-chip integrated circuit. This is because noise resistance can be significantly improved if provided. In particular, in the present embodiment,
Since this is a reflection-type device in which light from the light emitting element 1 is reflected by the object 2 to be detected and the reflected light is received by the light receiving element 3, the light receiving level of the light receiving element 3 is low and the output level thereof is also low. It is necessary to set the amplification factor of the head amplifier 10 high, and the head amplifier 10 is easily affected by noise. For this reason, it is necessary to improve noise resistance by integrating each circuit.

An example of the operation of the photodetector having such a configuration will be described with reference to the timing chart of FIG. FIG.
Each signal in (c) and (e) is the same as each signal in FIGS. 2 (c) and (e).

First, at time T0, when the object 2 to be detected disappears, the light emitting element 1 emits a light emitting element driving pulse signal (FIG. 2).
4 (a), the light of the light emitting element 1 is not received by the light receiving element 3 as shown in FIG. 4 (a). The output goes low. Thereafter, in the signal processing circuit 13, the signal detection gate circuit 13a synchronizes the comparator 1 with the signal detection gate pulse signal in FIG.
2 is sampled three times in succession, and at time T1, the output of the digital integration circuit 13c switches to low level as shown in FIG. 4 (g). This low-level output indicates that the detected object 2 does not exist, and is output to the outside through the output circuit 14.

Next, at time T2, disturbance light synchronized with the light emitting element drive pulse signal (shown in FIG.
When the light is received by the comparator 1, as shown in FIG.
2 becomes high level. At this time, in the signal processing circuit 13, the high-level output of the comparator 12 is synchronized with both the signal detection gate pulse signal of FIG. 4C and the noise detection gate pulse signal of FIG. 4E. 4 (d) and 4 (f), the high-level output of the comparator 12 is sampled by the signal detection gate circuit 13a and the noise detection gate circuit 13b. In this case, since the digital integrator 13c is initialized by the output of the noise detection gate circuit 13b, the output of the digital integrator 13c is maintained at a low level.

Incidentally, even if the high-level output of the comparator 12 is synchronized only with the signal detection gate pulse signal of FIG. 4C and the high-level output of the comparator 12 is sampled only by the signal detection gate circuit 13a, Since this high-level output is not sampled three consecutive times, the output of the digital integration circuit 13c is maintained at a low level.

Next, at time T3, disturbance light asynchronous with the light emitting element driving pulse signal (shown in FIG.
When the light is received by the comparator 1, as shown in FIG.
2 becomes high level. Since this high-level output is asynchronous to both the signal detection gate pulse signal of FIG. 4C and the noise detection gate pulse signal of FIG. 4E, the signal detection gate circuit 13a and the noise detection gate circuit 13b , The output of the digital integration circuit 13c is maintained at a low level.

Next, at time T4, disturbance light having a low frequency component is received by the light receiving element 3. Since the output of the light receiving element 3 corresponding to this disturbance light is a low frequency component, it is removed by the AC amplifier 11 and is not added to the comparator 12. Therefore, there is no change in the subsequent stage of the AC amplifier 11, and the output of the digital integration circuit 13c is maintained at a low level.

Next, when the detected object 2 appears at time T5, the light emitting element 1 is synchronized with the light emitting element drive pulse signal (shown in FIG. 2 (i)) as shown in FIG. The light is received by the light receiving element 3, and the output of the comparator 12 becomes high level as shown in FIG. Thereafter, in the signal processing circuit 13, in synchronization with the signal detection gate pulse signal of FIG. 4C, the high-level output of the comparator 12 becomes 3 by the signal detection gate circuit 13a as shown in FIG. 4 times at a time T6.
As shown in (g), the output of the digital integration circuit 13c switches to the high level. This high-level output indicates that the detected object 2 is present, and is taken out through the output circuit 14.

Although the disturbance light having a low frequency component is superimposed on the light of the light emitting element 1, the output of the light receiving element 3 corresponding to the disturbance light is removed by the AC amplifier 11.
This disturbance light does not affect the subsequent stage of the AC amplifier 11.

In addition, a latch circuit is provided at a stage preceding the noise detection gate circuit 13b, and the latch circuit is used by the comparator 12 corresponding to disturbance light generated during a period from immediately after the shift register clock signal to immediately before the light emitting element driving pulse. May be latched. This makes it possible to detect disturbance light generated before the light emitting element drive pulse.

As described above, in the photodetector of this embodiment, the light receiving element 3 corresponding to the disturbance light of the DC component and the low frequency component is used.
Is removed, so that it is not affected by the disturbance light. Even if the disturbance light has a high frequency component, if the disturbance light does not coincide with the light emission timing of the light emitting element 1, the disturbance light is treated as noise.
Erroneous detection does not occur. Further, even if the disturbance light is a high frequency component and the timing of the disturbance light coincides with the light emission timing of the light emitting element 1, the timing of the disturbance light coincides with the light emission timing of the light emitting element 3 three times continuously. Otherwise, the disturbance light is treated as noise, so that erroneous detection of the detected object 2 can be avoided. Moreover, since the cycle of the light emission timing of the light emitting element 1 fluctuates,
The light of the lighting equipment with built-in inverter is not synchronized,
False detection does not occur due to the light of the lighting fixture.
Furthermore, when this light detection device is applied to a pachinko game machine, it is extremely difficult to irradiate light synchronized with the fluctuation period from the outside, so that it is possible to prevent fraud that intentionally causes a malfunction. .

In the above embodiment, the pulse signal P whose period fluctuates is formed based on the oscillation signals of the first and second oscillators 4 and 5, but the pulse signal P is formed by another method. It may be formed. For example, a microcomputer may generate a random number and set the cycle of the pulse signal P corresponding to the random number. Alternatively, a variable may be changed stepwise by a microcomputer, and the cycle of the pulse signal P corresponding to this variable may be set. Further, an input terminal for externally controlling the microcomputer may be provided, and a method of generating a random number, a variable, and the like, a generation cycle, and the like may be externally instructed to the microcomputer through the input terminal.

Also, a pulse signal whose period fluctuates can be formed by a circuit as shown in FIG. FIG.
, The triangular wave oscillator 22 generates the triangular wave signal shown in FIG. 6A and outputs the triangular wave signal to the gate control circuit 23. The gate control circuit 23 receives the triangular wave signal and FIG.
FIG. 6 (b) comparing the preset threshold voltage Vth of FIG. 6 (b), when the level of the triangular wave signal is higher than the threshold voltage Vth, the level becomes high, and when the level of the triangular wave signal is lower than the threshold voltage Vth, the level becomes low. The square wave signal shown in (b) is output to the oscillator 25.

The oscillator 25 includes an operational amplifier 24, each resistor R
1, R2, each of the resistors R3 and R4 inserted in the feedback loop, the gate circuit 26, and the capacitor C. The square wave signal from the gate control circuit 23 is applied to the gate circuit 26. When the square wave signal is at a high level, the gate circuit 26 is open, and the resistance value of the feedback loop becomes the value of the resistor R3. When the square wave signal is at the low level, the gate circuit 26 is in the closed state, and the resistance value of the feedback loop is the combined value of the resistors R3 and R4. Since the combined value of the resistors R3 and R4 is lower than the value of the resistor R3,
When the gate circuit 26 is in the closed state, the charging and discharging time of the capacitor C is shorter, and the oscillation cycle of the oscillator 25 is shorter. The terminal voltage of the capacitor C changes as shown in FIG. 6C, and the output of the oscillator 25 changes as shown in FIG.

As is clear from FIGS. 6A to 6D,
When the square wave signal is at the high level and the gate circuit 26 is in the closed state, the charging and discharging time of the capacitor C is short, and the cycle of the pulse signal P output from the oscillator 25 is short. Further, when the square wave signal is at a low level and the gate circuit 26 is in the open state, the charging and discharging time of the capacitor C becomes longer, and the pulse signal P from the oscillator 25 becomes longer.
Period is longer.

Here, since the cycle of the triangular wave signal of the triangular wave oscillator 22 and the cycle of the square wave signal of the oscillator 25 are always asynchronous, the cycle of the square wave signal of the oscillator 25 fluctuates unevenly. Note that, instead of the triangular wave oscillator 22 and the gate control circuit 23, another oscillator that outputs a square wave signal shown in FIG.

Further, as shown in FIG.
A band pass filter 17 may be inserted between the timing signal generator 7 and the timing signal generator 7. This bandpass filter 1
Reference numeral 7 has a pass band for passing only the output signal of the light receiving element 3 corresponding to the light of the light emitting element 1. Since the frequency component of the output signal of the light receiving element 3 also changes with the change of the light emitting cycle of the light emitting element 1, the pass band of the band pass filter 17 is changed. Here, the triangular wave oscillator 2 shown in FIG.
2, the gate control circuit 23 and the oscillator 25 are applied, and the square wave signal of FIG. 6B from the gate control circuit 23 is added to the band-pass filter 17, and the band-pass filter is responded to the square wave signal. The pass band of the band-pass filter 17 is changed by switching each constant (resistance value or capacitor capacity) of the filter 17.

As a result, only the output signal of the light receiving element 3 corresponding to the light of the light emitting element 1 can be selected, and more accurate detection and erroneous detection can be prevented.

In a lighting device with a built-in inverter, 3
A frequency of 0 KHz or higher is employed, and the light contains a fundamental frequency component and a multiple component. Therefore, if the upper limit of the pass band of the band-pass filter 17 (higher cut-off frequency) is set to less than 30 KHz and the light emission time of the light emitting element is set to be longer than 33 microseconds,
The output signal of the light receiving element 3 corresponding to the light of the light emitting element 1 can be selected by passing through the band-pass filter 17, and the output signal of the light receiving element 3 corresponding to the light of the lighting equipment with a built-in inverter can be excluded.

Such a light detection device can be applied to detection of a pachinko ball in a pachinko game machine, detection of a sheet in a copying machine, and the like.

FIG. 8 shows a pachinko ball detecting apparatus for detecting a pachinko ball. 8A is a plan view of the apparatus, FIG. 8B is a side view of the apparatus, and FIG.
(C) is a longitudinal sectional view of the device.

The light detection device shown in FIG. 7 is applied to this pachinko ball detection device. The light emitted from the light emitting element 1 is divided into a cylindrical lens 31 and each slit 32.
To the passage hole 33a of the holder 33 through the gap. At this time, when the pachinko ball naturally falls and passes through the passage hole 33a and the pachinko ball 34 enters the detection range, light from the light emitting element 1 is reflected on the surface of the pachinko ball 34, and this reflected light is During this time, the light enters the light receiving element 3 via the cylindrical lens 36 and the prism 37.

If the pachinko ball does not enter the passage hole 33a, the light of the light emitting element 1 is dispersed and is not guided to the light receiving element 3. However, FIG.
As shown in (c), the light emitting element 1 is formed by each slit 32.
Since the light emission angle is kept small, this light hardly leaks outside the holder 33. For this reason, it is impossible to detect the light of the light emitting element 1 from the outside and measure the light emission cycle thereof, and to imitate the light of this light emission cycle. In addition, the light of the light emission cycle can be radiated from outside.

The present invention is not limited to the above embodiment, but can be variously modified. For example, the light emitting element and the light receiving element may be of any type. Further, the present invention can be applied to not only a reflection type light detection device but also a cut-off type light detection device.

[0061]

As described above, according to the present invention, the light emitting cycle of the light emitting element is changed, and the output signal of the light receiving element is detected in synchronization with the changing light emitting cycle. Since the light emission cycle of this light emitting element fluctuates, it is almost impossible for disturbance light to synchronize with this light emission cycle. Therefore, malfunction of the light detection device hardly occurs due to disturbance light. In addition, when the photodetection device of the present invention is applied to a pachinko game machine, it is extremely difficult to irradiate light synchronized with the fluctuation period from the outside. Therefore, it is necessary to prevent fraud that intentionally causes a malfunction. Can be.

Further, according to the present invention, the light emission cycle is varied by various methods.

Further, according to the present invention, the fluctuation of the light emission cycle can be controlled from the outside.

According to the present invention, only the output signal of the light receiving element corresponding to the light of the light emitting element is selected by the band pass filter, and the output signal of the light receiving element corresponding to the disturbance light is excluded. Thereby, for example, light of a lighting fixture containing components of various frequencies can be almost eliminated.

Further, according to the present invention, the frequency component of the light of the light emitting element also fluctuates with the fluctuation of the light emitting cycle of the light emitting element. The output signal of the light receiving element corresponding to the light can be properly selected.

Further, according to the present invention, the light emission time of the light emitting element is set longer than 33 microseconds, and the high cut-off frequency of the band-pass filter is set corresponding to the light emission time. Generally, a lighting device with a built-in inverter uses a frequency of 30 KHz or more. Therefore, in order to clearly distinguish the light from such a lighting device, the light emitting time of the light emitting element may be set to be longer than 33 microseconds (the light emitting frequency is set to less than 30 KHz). If the high cut-off frequency (less than 30 KHz) of the filter is set, the output signal of the light receiving element corresponding to the light of the light emitting element is selected by the band pass filter, and the output of the light receiving element corresponding to the light of the lighting fixture is selected. Signals can be rejected.

Further, according to the present invention, since the output signal of the light receiving element is latched by the latch means, the detection result of the photodetector can be easily confirmed.

Further, according to the present invention, since the period changing means and the synchronization detecting means are formed on the same integrated circuit,
The signal transmission path can be shortened, and the influence of disturbance noise is reduced.

Further, according to the present invention, since the light of the light emitting element is made incident only on the light receiving element, it becomes impossible to detect the light of the light emitting element from outside and measure the light emission period. For example, in a pachinko game machine, it is impossible to externally measure the light emission cycle and imitate the light of the light emission cycle, and for the purpose of fraud and intentionally causing a malfunction, the light emission cycle is Light cannot be irradiated from outside.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a photodetector of the present invention.

FIGS. 2 (i), (c), (e) and (h) are timing charts showing respective signals in the device of FIG.

FIG. 3 is a block diagram showing a signal processing circuit in the device of FIG.

FIGS. 4A to 4G are timing charts showing signals in the device of FIG. 1;

FIG. 5 is a block diagram showing a triangular wave oscillator, a gate control circuit, and an oscillator applied in place of the first and second oscillators in the device of FIG. 1;

FIGS. 6A to 6D are timing charts showing signals in the circuit of FIG. 5;

FIG. 7 is a block diagram showing a modification of the apparatus of FIG.

8A is a plan view showing a pachinko ball detection device to which the device of FIG. 7 is applied, FIG. 8B is a side view of the pachinko ball detection device, and FIG. 8C is a longitudinal section of the pachinko ball detection device. FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light emitting element 2 object to be detected 3 light receiving element 4 first oscillator 5 second oscillator 6 pulse variation circuit 7 timing signal generation circuit 8 light emitting element pulse drive circuit 10 head amplifier 11 AC amplifier 12 comparator 13 signal processing circuit 14 output circuit 15 fixed Voltage circuit

Claims (13)

[Claims] 1. A light-emitting element, a light-receiving element for receiving light from the light-emitting element, a period changing means for changing a light-emission cycle of the light-emitting element, and an output signal of the light-receiving element in synchronization with the light-emission cycle of the light-emitting element And a synchronization detecting means for detecting the light detection. 2. The light detecting device according to claim 1, wherein the period changing means randomly changes a light emitting period. 3. The photodetector according to claim 1, wherein the period changing unit changes the light emission period in a stepwise manner. 4. The apparatus according to claim 1, wherein the period changing unit includes a random number generating unit that generates a random number, and changes the light emission period based on the random number generated by the random number generating unit. 3. The photodetector according to claim 1. 5. The photodetector according to claim 1, wherein the period changing unit changes the light emission period based on a plurality of signals having different periods. 6. The photodetector according to claim 1, wherein the period changing unit changes the light emission period based on a plurality of signals having different waveforms. 7. The photodetector according to claim 1, wherein the period changing unit changes the light emission period in response to an external signal. 8. A band pass filter for passing an output signal of the light receiving element corresponding to light of the light emitting element, wherein the synchronization detecting means inputs an output signal of the light receiving element via the band pass filter. Claims 1 to 7
The photodetector according to any one of the above. 9. The photodetector according to claim 8, wherein the frequency band of the band-pass filter is changed according to the change of the light emission cycle. 10. The light-emitting device according to claim 8, wherein the light-emitting time of the light-emitting element is set to be longer than 33 microseconds, and the cut-off frequency on the high frequency side of the band-pass filter is set in accordance with the light-emitting time. Photodetector. 11. The synchronization detecting means includes latch means for latching the detected signal for a period equal to or longer than the light emitting cycle when detecting the output signal of the light receiving element in synchronization with the light emitting cycle of the light emitting element. 11. The method according to claim 1, wherein
The photodetector according to any one of the above. 12. The photodetector according to claim 1, wherein the period changing means and the synchronization detecting means are formed on the same integrated circuit. 13. The light path according to claim 1, further comprising an optical path for allowing light from the light emitting element to enter only the light receiving element.
13. The photodetector according to any one of claims 12 to 12.