JPH04192568A - Movable photodetector - Google Patents

Abstract

PURPOSE:To obtain a wide detection range and to detect a direction whose optical intensity is largest by a method wherein this photodetector is composed of the following: a scanning part which can be turned in at least two directions by the elastic vibration of an elastic deformation part; and a photodetector chip installed at the scanning part. CONSTITUTION:When a vibration part 5 is vibrated by using a driving source 6, both vibrations in a twist deformation mode and in a bend deformation mode are amplified at an elastic deformation part 2, and a vibration at a turning angle thetaT around the axial center P and a vibration at a turning angle thetaB around a Q-direction are composed at a scanning part 3. As a result, the photodetection direction of a photodetector chip 4 is scanned inside a space at a definite pyramid-shaped solid angle. In addition, an output signal from the photodetector chip 4 is input to a signal processing device. Thereby, light can be detected over a wide range, and it is possible to detect a direction whose photodetection sensitivity is highest.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a movable light-receiving element that can continuously change the light-receiving direction.

[Background technology]

A conventionally used light receiving element (phototransistor) 51 is shown in FIG. This is done by mounting a light-receiving element chip (not shown) formed on a silicon substrate on a lead frame 52 or stem that is the element body, molding it with resin and housing it in a resin case 54 with a lens 53, or It is shielded with a cap. FIG. 7(a) shows the light receiving direction (direction angle φ) of the light receiving element 51.
An example of the relationship between and light receiving sensitivity (relative sensitivity) is shown. Here, the directivity angle φ is an angle determined with the center of the light receiving element 51 as a reference, as shown in FIG. 7(b). In this way, the light receiving element 51 generally has a highly directional light receiving sensitivity.

[Problem to be solved by the invention]

As mentioned above, the light-receiving element generally has strong directivity, so it cannot detect a wide range.If you want to obtain a wide detection range, you need to add a complicated optical system and use this optical system. It is necessary to make the transmitted light enter the light-receiving element, which increases the overall size and limits the expansion of the detection range. Alternatively, multiple light-receiving elements may be arranged in different directions, but in that case, in order to eliminate areas with low light-receiving sensitivity (blind spots), a very large number of light-receiving elements would be required. The overall shape also had to become larger. Furthermore, in order to detect the direction in which the light receiving sensitivity is maximum, the light receiving element is attached to the movable part of the mechanical drive device.
The light receiving direction of the light receiving element must be changed in all directions by the driving device, and there is a problem in that the overall shape becomes large. The present invention was made in view of the drawbacks of the conventional examples described above, and its purpose is to obtain a wide detection range using a directional light-receiving element chip, and furthermore, to obtain the maximum detection range of light intensity. An object of the present invention is to provide a small-sized light receiving element that can detect large directions.

[Means to solve the problem]

The movable light receiving element of the present invention includes an elastic deformation section having at least two elastic deformation modes, an excitation section provided at one end of the elastic deformation section, and vibrations at a resonant frequency for each elastic deformation mode of the elastic deformation section. a drive source for applying the vibration to the vibrating part, and a drive source provided at the other end of the elastic deformation part, so as to elastically vibrate the elastic deformation part in at least one of the elastic deformation modes when vibration is applied to the vibration part. It is characterized in that it consists of a scanning section that is arranged so that it can rotate in at least two directions by elastic vibration of an elastically deformable section, and a light-receiving element chip provided in the scanning section.

[Effect]

When vibrations at resonance frequencies for two elastic deformation modes of the elastic deformation section are applied to the vibrating section, the elastic deformation section vibrates elastically in both elastic deformation modes, and the scanning section rotates in two directions simultaneously. For this reason, the light receiving direction of the light receiving element chip provided in the scanning section changes continuously within a certain angular (solid angle) region, and even if one light receiving element chip with directivity is used, it can cover a wide range. Light can be detected. Furthermore, by continuously changing the direction of the light-receiving element chip having directivity, it is possible to detect the direction in which the light intensity is greatest (the direction in which the light-receiving sensitivity is maximum) by itself. In addition, the scanning section, elastic deformation section, and vibration section can be formed into plate shapes, and a small actuator such as a piezoelectric vibrator can be used as the drive source, so the above functions can be achieved. The movable light-receiving element can be downsized. Furthermore, if the amplitude of the vibrating part is changed depending on the driving source,
The amplitude of the elastic vibration in the elastic deformation section (the rotation angle of the scanning section) can be changed, and the size of the light receiving area or the light receiving range can be easily adjusted.

【Example】

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. An embodiment of the present invention is shown in FIGS. 1(a) and 1(b). This movable light receiving element 7 is composed of a thin plate 1, a small drive source 6 such as a piezoelectric vibrator or a magnetostrictive vibrator that generates minute vibrations, and a light receiving element chip 4 such as a photodiode chip. There is. In the plate 1, an excitation part 5 for applying vibration from a drive source 6 is integrally provided at the lower end of a long narrow elastic deformation part 2, and a scanning part 3 is integrally provided at the upper end of the elastic deformation part 2. It is being Here, the elastic deformation section 2 has a torsional deformation mode in which it twists and deforms around the axis P as shown in FIG. A bending deformation mode is enabled, and the elastic vibration in the torsional deformation mode has a resonance frequency of fT, and the elastic vibration in the bending deformation mode has a resonance frequency of fa. The scan section 3 is formed in an unbalanced shape with respect to the axis P of the elastically deformable section 2, and the weight section 8 is formed in a portion away from the axis P of the elastically deformable section 2. Therefore, the center of gravity of the scanning section 3 is located away from the axis P of the elastically deformable section 2, and is further located above the upper end of the elastically deformable section 2. In addition, on the surface of the scanning unit 3, there is a highly directional 1
A number of light receiving element chips 4 are attached. Vibrating part 5
is fixed to the drive source 6 such as a piezoelectric vibrator by adhesion or bonding, and the scanning section 3 is freely supported by the elastic deformation section 2 . A drive source 6 such as a piezoelectric vibrator that applies high-frequency vibration (for example, several hundred Hz) to the vibrator 5 is controlled by a drive circuit, and has a resonance frequency f7 in a torsional deformation mode and a resonance frequency fa in a bending deformation mode. Excited vibrations. What is shown in FIG. 3 is an example of this drive circuit 9, which includes an oscillator lO that continues to output a voltage signal with a frequency that matches the resonance frequency fa of the torsional deformation mode, and a voltage that is output from the oscillator 10. An amplifier 11 that amplifies a signal, an oscillator 12 that continues to output a voltage signal with a frequency that matches the resonance frequency f'a of the bending deformation mode, and this oscillator 12
an amplifier 13 that amplifies the voltage signal output from the
It consists of a mixing circuit 14 that superimposes the voltage signal of frequency fT output from both amplifiers 11 and 13 and the voltage signal of frequency fa and outputs the superimposed voltage signal. Since the movable light-receiving element 7 according to the present invention is configured as described above, the drive circuit 9 causes the drive source 6 to vibrate, and this vibration is applied to the vibrator 5 to cause reciprocating vibration. When this happens, an inertial force acts on the scanning section 3, and this inertial force causes the elastic deformation section 2 to elastically deform and vibrate in the direction in which the inertial force is applied. Moreover, the component of the driving frequency f applied to the vibrating section 5 is the resonance frequency fT of the torsional deformation mode or the resonance frequency of the bending deformation mode, which is determined by the spring stiffness of the elastic deformation section 2, the value of the moment of inertia, the shape of the plate 7, etc. When the frequency matches f8, the elastic vibration of the mode is amplified by the elastic deformation section 2, and the scanning section 3 is driven at a large rotation angle. That is, the relationship between the drive frequency f (component) and the rotation angle θ7 in the torsional deformation mode or the rotation angle θ8 in the bending deformation mode of the scanning section 3 is as shown in FIG. 2, for example. FIG. 2 shows the relationship between the drive frequency f of the drive source 6 and the rotation angle of the scanning unit 3 when the two resonance frequencies fi<fo, where the horizontal axis is the drive frequency f and the vertical axis is the rotation angle of the scanning unit 3. The rotation angle θa in the torsional deformation mode or the rotation angle θ8 in the bending deformation mode of the scanning section 3 is shown. In this way, the rotation angle θ7 in the torsional deformation mode is determined by the drive frequency f being fT.
It reaches its maximum when it is equal to , and rapidly attenuates on both sides. On the other hand, the rotation angle θ8 in the bending deformation mode reaches a maximum when the drive frequency f is equal to fa, and rapidly attenuates on both sides thereof. Therefore, even if the driving source 6 is a piezoelectric vibrator that can only produce minute vibrations, it is possible to rotate the scanning unit 3 by a large angle by driving it at a frequency equal to the resonance frequency of each elastic deformation mode. I can do it. Therefore, when the voltage applied to the vibrating section 5 includes the resonance frequency ft of the torsional deformation mode, the vibration of the torsional deformation mode is amplified in the elastic deformation section 2, and the scanning section 3
As shown in Figure (a), it is rotated around the axis P at a rotation angle of θ1. Therefore, the light receiving direction of the light receiving element chip 4 is scanned in the X direction. Furthermore, if the voltage applied to the vibrating section 5 includes the resonant frequency fB of the bending deformation mode, the vibration of the bending deformation mode is amplified in the elastic deformation section 2, and the scanning section 3 is
), the direction Q perpendicular to the axis P at a rotation angle of θ8
can be rotated around. Therefore, the light receiving direction of the light receiving element chip 4 is scanned in the X direction. Therefore, the driving source 6 causes vibrations having a resonance frequency f in the torsional deformation mode and a resonance frequency f in the bending deformation mode. When the excitation unit 5 is vibrated in a vibration mode in which vibrations with The vibration at the moving angle θ and the vibration at the rotation angle θ around the Q direction are combined. As a result, the light-receiving direction of the light-receiving element chip 4 is scanned within a pyramid-shaped space of a constant solid angle, and one light-receiving element chip 4 with strong directivity is used to receive or detect light over a wide range. be able to. Furthermore, by inputting the output signal from the light-receiving element chip 4 to a signal processing device (not shown), it is possible to know the direction in which the light intensity is greatest (the direction in which the light-receiving sensitivity is greatest). Furthermore, when the amplitude of the vibrating section 5 is changed by adjusting the voltage applied to the drive source 6, the rotation angle θ of the scanning section 3
7 or θ3 can be controlled. That is, the curve shown by the broken line in FIG.
When the amplitude of θ7. increases, the rotation angle θ7. θ
8 also increases. Therefore, the light receiving range of the light receiving element chip 4 can also be changed by changing the applied voltage. In addition, in the above explanation, the case where the rotational movement around the P-axis and the rotational movement around the Q-axis are performed simultaneously,
The drive circuit may perform rotational movement only around the P axis or around the Q axis. 4(a) and 4(b) show another embodiment of the present invention, in which the angle of the detection surface 15 can be detected using the movable light-receiving element 7. That is, a light emitting element 16 such as a semiconductor laser or a light emitting diode is fixed to the pressure detection surface 15, and the light emitting element 16 is connected to the detection surface 1.
5, and the angle θ of the scanning unit 3 and the light receiving element chip 4 is synchronized with the detection signal of the light receiving element chip 4, and when the light receiving intensity of the light receiving element chip 4 reaches the maximum. The angle of the detection surface 15 is known from the angle θ. Specifically, FIG. 5(a) shows the state of the scanning section 3 when the scanning section 3 is rotating around the P axis at a rotation angle of θ7 as shown in FIG. 4(a). The angle θ is shown (the direction when the scanning unit 3 is not driven is θ−〇), and FIG. 4 shows a change in the strength W of the detection signal of No. 4. The intensity W of the light reception signal of the light receiving element chip 4 is the maximum value Wmax
At this time, the light receiving element chip 4 faces the direction of the light emitting element 16 (or the direction perpendicular to the detection surface 15), so if we know the angle θm of the scanning unit 3 when the intensity W is the maximum value Wmax, The angle of the detection surface 15 can be known. Similarly, the angle of the detection surface 15 rotating around the Q-axis as shown in FIG. 4(b) can also be determined. Note that in the above method, if there is a possibility that an error may be included in the direction of the scanning unit 3 when it is not driven, the detection surface 15 should be placed facing the reference direction, so that the intensity W of the detection signal is at its maximum. By measuring the scanning section angle, the angle of the detection surface 15 can be known with respect to the direction, and the accuracy of measurement of the detection surface 15 can be improved. The movable light-receiving element of the present invention is not limited to the above embodiments, and various design changes can be made without departing from the technical idea of the present invention. For example, the drive source may be any actuator capable of high-speed micro-vibration in addition to piezoelectric vibrators, magnetostrictive vibrators, etc. For example, an actuator that generates micro-vibration using electrostatic force may be used. Further, the illustrated shape of the plate is only an example, and the plate is not limited to the illustrated shape as long as it can obtain two or more types of elastic deformation modes. Effects of the Invention According to the present invention, the vibration of a drive source such as a piezoelectric vibrator can be converted into rotational movement in at least two directions in the scanning section by the elastic deformation section, and the light receiving direction of the light receiving element chip can be changed. Scanning can be performed over a wide spatial area. Therefore, light can be detected in a wide range using a light receiving element chip having directivity without using a complicated optical system. Furthermore, it is possible to detect the direction in which the light receiving sensitivity is highest using a single light receiving element chip having directivity. Moreover, according to the present invention, a light receiving element having the above-mentioned functions can be miniaturized. Further, by adjusting the amplitude of the vibrating section, each scan angle of the scanning section can be changed, and a single light receiving element can scan an arbitrary spatial region in the light receiving direction.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) show one embodiment of the present invention, and FIG. 1(a) is a perspective view showing its torsional deformation mode;
Figure (b) is a perspective view showing the bending deformation mode, Figure 2 is a diagram showing the relationship between the drive frequency and the rotation angle of the scanning section, and Figure 3 is a diagram showing the drive circuit for driving the same drive source. The block diagram shown in FIG. 4(a) and FIG. 4(b) are another embodiment of the present invention, in which FIG. 4(a) is a perspective view showing its torsional deformation mode, and FIG. 4(b) is a perspective view showing its bending mode. FIG. 5 is a perspective view showing the deformation mode, FIG. ) is a diagram showing the relationship between the light-receiving direction (directivity angle) and light-receiving sensitivity of the light-receiving element, and FIG. 7(b) is an explanatory diagram of the directivity angle in FIG. 7(a). 2... Elastic deformation part 3... Scanning part 4... Light receiving element chip 5... Vibrating part 6... Drive source

Claims (1)

[Claims] (1) an elastic deformation section having at least two elastic deformation modes; an excitation section provided at one end of the elastic deformation section; and a vibration at a resonant frequency for each elastic deformation mode of the elastic deformation section applied to the excitation section. a drive source provided at the other end of the elastic deformation section and arranged to elastically vibrate the elastic deformation section in at least one of the elastic deformation modes when vibration is applied to the vibrating section; 1. A movable light-receiving element comprising a scanning part that can be rotated in at least two directions by elastic vibration, and a light-receiving element chip provided in the scanning part.