JPH1114453A - Photodetector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To add a light interceptor which can maintain an open state or a shut-off state, which is operated surely and whose power consumption is small by installing a square-wave oscillator or the like which oscillates a square-wave signal and a changeover signal which is synchronized with its rise. SOLUTION: A square-wave oscillator 1 outputs a square-wave signal (a) and a changeover signal (b) which is synchronized with its rise. A psudo differentiating circuit 2 outputs a signal (c) which time-differentiates the square-wave signal (b), and an amplifier circuit 3 amplifies the square-wave signal (a) so as to output a signal (a'). Whenever the changeover signal (b) is output, a signal changeover circuit 4 changes over the signal (c) and the signal (a') so as to output a signal waveform (d), and a power amplifier 5 amplifies the signal waveform (d) so as to excite an exciting coil by a voltage (d'). Then, since a large attraction force is generated between a core and a permanent magnet only during a short time in which a shutter used to shut off incidentlight is moved to an open position from a closed position, the shutter can be operated surely by increasing a slight power consumption, and the reliability of a light detecting apparatus is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photodetector provided with a light blocker for blocking incident light at an arbitrary time period.

[0002]

2. Description of the Related Art A photodetector equipped with a light blocker for blocking incident light at an arbitrary time period, for example, a pyroelectric infrared detector, measures the amount of incident infrared light from the time differential value of temperature change. Since it is a device, it is necessary to periodically interrupt the incidence of infrared rays to perform continuous measurement. For this reason, the incidence of infrared rays is periodically interrupted using an optical circuit breaker. FIG. 5 shows a configuration example of this conventional photodetector with an optical circuit breaker. In the drawing, H is incident light of a detection target emitted from a light source (not shown). 8 is the base,
A photosensitive element 9 and a gantry 10 are fixed to the base 8. Two piezoelectric bimorphs 11 are fixed to the gantry 10 in parallel, and a slit plate 12 is attached to the tip of each to cover the photosensitive element 9 so as to block the incident light H at the top and bottom. ing. The slit plate 12 has a predetermined slit opening. When no voltage is applied to the piezoelectric bimorph 11, the slits of the two slit plates 12 overlap with each other, and the incident light H reaches the photosensitive element 9 through the slits. When a voltage is applied to the piezoelectric bimorph 11, the piezoelectric bimorph 11
Is displaced, and the slit openings of the two slit plates 12 are shifted from each other, thereby blocking the incident light H. Thus, by periodically applying a voltage to the piezoelectric bimorph 11, the light H incident on the photosensitive element 9 is periodically blocked. Thus, an optical circuit breaker is constituted by the piezoelectric bimorph 11 and the slit plate 12 (for example, SANYO techni).
cal review vol. 21 No. 2 JU
N. 1989). In this configuration, since the displacement amount of the piezoelectric bimorph is small, it is difficult to increase the operation amount of the slit plate. In order to increase the operation amount, it was necessary to lengthen the piezoelectric bimorph or to apply a voltage that fluctuates at the resonance frequency to the piezoelectric bimorph. However, if the piezoelectric bimorph is lengthened, there is a problem that the dimensions of the photodetector increase, and if a voltage that fluctuates at the resonance frequency is applied, the optical circuit breaker cannot be opened or stopped in a cut-off state. was there.

As a second prior art example which solves these problems, there has been proposed a photodetector provided with an optical circuit breaker driven by an electromagnet. FIG. 6 shows an example of the configuration of a photodetector with an optical circuit breaker according to the second prior art. In the figure, reference numeral 8 denotes a base, on which a photosensitive element 9 and an electromagnet 21 are fixed. The electromagnet 21 has an exciting coil 22 wound around an iron core 23. An arm 24 is rotatably attached to the base 8 via a shaft 25. A shutter 26 is fixed to one end of the arm 24 so as to cover above the photosensitive element 9. Shutter 2
Reference numeral 6 denotes a flat plate having a slit 27 formed in a part thereof. A permanent magnet 28 is fixed to the opposite end of the arm 24, and faces the iron core 23. When the excitation coil 22 is not energized, the permanent magnet 28 is attracted to the iron core 23, so that the arm 24 is at a position rotated counterclockwise. At this time, the slit 27 comes directly above the photosensitive element 8, and incident light from above enters the photosensitive element 8. When the permanent magnet 28 is energized to the exciting coil 22 in such a direction that the iron core 23 repels, the arm 24 rotates clockwise and the slit 27
Comes to a position deviated from directly above the photosensitive element 8, so that incident light from above is blocked. As described above, in the photodetector with an optical circuit breaker according to the second conventional technique, an ON / OFF type rectangular wave current as shown in FIG. 7 is supplied to the exciting coil to drive the shutter.

[0004]

However, in the prior art, an ON / OFF type rectangular wave current is supplied to the exciting coil, and the attractive force between the permanent magnet and the non-excited iron core is used.
Since the shutter is driven from the closed position to the open position, there is a problem that the driving force is weak and the operation becomes uncertain. Also, in order to increase the attractive force between the permanent magnet and the iron core, a current in the opposite direction is supplied to the exciting coil, that is, a rectangular wave current whose polarity alternates as shown in FIG. 8 is supplied. Then, since the power is always supplied, there is a problem that the power consumption increases and the exciting coil generates heat. Therefore, an object of the present invention is to provide a photodetector with an optical circuit breaker that can maintain an open or shut-off state, operates reliably, and consumes less power.

[0005]

In order to solve the above problems, the present invention provides an electromagnet, a rectangular wave oscillator that oscillates a rectangular wave signal and a switching signal synchronized with rising and falling of the rectangular wave signal, An amplifier circuit for amplifying a rectangular wave signal; a pseudo-differential circuit for differentiating the rectangular wave signal; a signal switching circuit for alternately switching an output of the amplifier circuit and an output of the pseudo-differential circuit by the switching signal; The shutter is driven by a power amplifier that supplies a current proportional to the output of the switching circuit to the electromagnet.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. Since the mechanism of the photodetector itself is the same as that of the photodetector with a light breaker according to the second prior art, an electric circuit will be described. FIG. 1 is a block diagram of an electric circuit of an optical circuit breaker of a photodetector showing an embodiment of the present invention, and FIG. 2 is a time chart showing electric signals flowing through the electric circuit. In the figure, reference numeral 1 denotes a rectangular wave oscillator which outputs a rectangular wave signal a and a switching signal b synchronized with rising and falling of the rectangular wave signal a. A pseudo-differential circuit 2 receives the rectangular wave signal a and outputs a signal c having a waveform obtained by time-differentiating the rectangular wave signal a. Reference numeral 3 denotes an amplifying circuit which receives the rectangular wave signal a and outputs a signal a 'obtained by amplifying the rectangular wave signal a. Reference numeral 4 denotes a signal switching circuit which receives a switching signal b of the rectangular wave oscillator 1, an output signal c of the pseudo differentiating circuit 2, and an output signal a 'of the amplifying circuit 3, and generates a pseudo signal every time the switching signal is inputted. The output signal c of the differentiating circuit 2 and the output signal a 'of the amplifying circuit 3 are switched to generate and output a signal waveform d. A power amplifier 5 amplifies the signal waveform d to obtain a required voltage d ',
2 is energized. Next, an output waveform d of the signal switching circuit 4 will be described with reference to FIG. In the time section indicated by T1, the exciting coil 22 includes the permanent magnet 28 and the iron core 23.
Current continues to flow in such a direction that
Is separated from the iron core 23, and the shutter 26 is at a position for blocking incident light. In the next time section indicated by T2, a current flows through the exciting coil 22 in such a direction as to attract the permanent magnet 28 and the iron core 23, and the permanent magnet 23 is attracted by a large force.
Adsorbed on the iron core 23, the shutter 26 moves to a position where the incident light passes. In the next time section T3, the voltage becomes 0.
, And no current flows through the exciting coil 22. At this time, the permanent magnet 28 attracts the iron core 23 and
6 is kept open. The time section T2 is a shorter time than T1 and T2. This is because the distance between the permanent magnet 28 and the iron core 23 is large in the closed position.
This is because the suction force acting between the shaft 8 and the iron core 23 is weaker than the frictional force between the shaft 25 and the bearing. Permanent magnet 28
When the distance between the coil 23 and the iron core 23 is short, a sufficient attractive force to overcome the frictional force can be obtained without energizing the exciting coil 22. In the time section T3, if the current continues to flow, power consumption is uneconomical, and the heat generated from the exciting coil 22 increases. In addition,
If a rectangular wave with required characteristics can be obtained by the rectangular wave oscillator 1, a configuration in which the amplifier circuit 3 is omitted and the rectangular wave output of the rectangular wave oscillator 1 is directly input to the signal switching circuit 4 can be selected. If the required power can be obtained by the rectangular wave oscillator 1, a configuration in which the power amplifier 5 is omitted can be selected. Next, a second embodiment of the present invention will be described with reference to the drawings. Since the mechanism of the photodetector is the same as that of the first embodiment, the electric circuit will be described. FIG. 3 is a block diagram of an optical circuit breaker of the photodetector according to the embodiment of the present invention. In the figure, reference numeral 1 denotes a rectangular wave oscillator that oscillates a rectangular wave of an arbitrary pattern. For example, an arbitrary rectangular wave pattern is input in the form of a digital signal, stored in a semiconductor memory, and
This is a device obtained by a known technique that reads out this digital signal and oscillates a rectangular wave of the previously input pattern. Reference numeral 5 denotes a power amplifier, which amplifies the output of the signal rectangular wave oscillator 1 to obtain a required voltage, and energizes the exciting coil 22. If the required power can be obtained by the square wave oscillator 1, a configuration in which the power amplifier 5 is omitted can be selected. In FIG.
2 shows a pattern of a rectangular wave input to the rectangular wave oscillator 1. In the figure, Ta, Tb, and Tc denote time sections, respectively. In the time section Ta, a constant voltage is maintained so that a current flows in a direction in which the iron core 23 and the permanent magnet 28 repel each other. Next, in the time section Tb, the core 2
A voltage having a polarity opposite to that of the time section Ta is generated so that the permanent magnet 3 and the permanent magnet 28 attract with a large force. Finally, in the time section Tc, the voltage is set to 0 and the iron core 23 is demagnetized. When a rectangular wave repeating this pattern is oscillated by the rectangular oscillator 1, a large attractive force is applied to the iron core 23 and the permanent magnet 28 for a short time during which the shutter 26 moves from the closed position to the open position.
Therefore, the operation of the shutter 26 can be ensured with a slight increase in power consumption.

[0007]

As described above, according to the present invention, the following effects can be obtained. (1) Since the electromagnet is energized in the direction to attract the permanent magnet, the operation of the shutter is more reliable, and the reliability of the photodetector is improved. (2) Since the time during which the electromagnet is energized in the direction to attract the permanent magnet is short, the power consumption is small and the heat generated from the exciting coil is small, so that the photodetector can be downsized.

[Brief description of the drawings]

FIG. 1 is a block diagram of an electric circuit of an optical circuit breaker according to a first embodiment of the present invention.

FIG. 2 is a time chart of an electric signal of the optical circuit breaker according to the first embodiment of the present invention.

FIG. 3 is a block diagram of an electric circuit of an optical circuit breaker according to a second embodiment of the present invention.

FIG. 4 is a time chart of an electric signal of an optical circuit breaker according to a second embodiment of the present invention.

FIG. 5 is a perspective view of a photodetector showing a first example of the prior art.

FIG. 6 is a perspective view of a photodetector showing a second example of the related art.

FIG. 7 is a time chart of an electric signal of an optical circuit breaker showing a second example of the related art.

FIG. 8 is a time chart of an electric signal of an optical circuit breaker showing a second example of the related art.

[Explanation of symbols]

 1: square wave oscillator 2: pseudo differentiation circuit 3: amplification circuit 4: signal switching circuit 5: power amplification circuit 8: base 9: photosensitive element 10: mount 11: piezoelectric bimorph 12: slit plate 21: electromagnet 22: excitation coil 23 : Iron core 24: Axis 25: Arm 26: Shutter 27: Slit 28: Permanent magnet a: Rectangular wave signal a ': Output signal of amplifier circuit b: Switching signal c: Output signal of pseudo-differential circuit d: Output of signal switching circuit Waveform d ': output voltage of power amplifier H: incident light

Claims (5)

[Claims] 1. A photosensitive element for detecting incident light, an optical circuit breaker driven by magnetic repulsion and magnetic attraction acting between a permanent magnet and an electromagnet, and periodically intercepting a light beam incident on the photosensitive element. A photodetector comprising: a rectangular wave signal; a rectangular wave oscillator that oscillates a switching signal synchronized with a rise of the rectangular wave signal; a pseudo-differential circuit that differentiates the rectangular wave signal; A photodetector, comprising: a light breaker provided with a signal switching circuit that alternately switches the output of a pseudo-differential circuit with the switching signal. 2. A photosensitive element for detecting incident light, an optical circuit breaker driven by a magnetic repulsive force and a magnetic attractive force acting between a permanent magnet and an electromagnet, and periodically intercepting a light beam incident on the photosensitive element. A photodetector comprising: a rectangular wave signal; a rectangular wave oscillator that oscillates a switching signal synchronized with a rise of the rectangular wave signal; a pseudo-differential circuit that differentiates the rectangular wave signal; An optical circuit breaker comprising: a signal switching circuit that alternately switches the output of a pseudo-differential circuit by the switching signal; and a power amplifier that causes a current proportional to the output of the signal switching circuit to flow through the electromagnet. Photodetector. 3. A photosensitive element for detecting incident light, an optical circuit breaker driven by a magnetic repulsive force and a magnetic attractive force acting between a permanent magnet and an electromagnet, and periodically intercepting a light beam incident on the photosensitive element. A light detecting device comprising: a light interrupter provided with a rectangular wave oscillator that oscillates a rectangular wave signal having an arbitrary waveform. 4. A photosensitive element for detecting incident light, an optical circuit breaker driven by a magnetic repulsive force and a magnetic attractive force acting between a permanent magnet and an electromagnet, and periodically intercepting a light beam incident on the photosensitive element. An optical detector comprising: a rectangular wave oscillator that oscillates a rectangular wave signal having an arbitrary waveform; and a power amplifier that includes a power amplifier that causes a current proportional to the output of the rectangular wave oscillator to flow through the electromagnet. Characteristic photodetector. 5. The waveform repeats a cycle of holding a constant voltage for a certain period of time, then turning to reverse voltage for a short period of time, then holding zero voltage for a certain period of time, and returning to the initial voltage again. The photodetector according to claim 3 or 4, wherein