JPH0510815A - Light-excited vibrator type sensor - Google Patents

Abstract

PURPOSE:To obtain a sensor being small in size, inexpensive and easy to use by a construction wherein a semiconductor laser with a photodetector which applies a light beam to a vibrator and detects the natural frequency of the vibrator from interference of a reflected light with an internal light and the vibrator are integrated on the same base plate. CONSTITUTION:A vibrator 1, a semiconductor laser 2 for detection and a photodetector 3 are integrated on the same base plate. The vibrator 1 is subjected to pulse irradiation by a laser light and thereby a natural frequency is excited in the horizontal direction. When the laser 2 irradiates the vibrator l from the opposite side in a state of continuous oscillation, on the other hand, a reflected light 8 is fed back to the laser 2. The reflected light 8 interferes with an internal light 9 and a light output 10 changing in a cosine function in a period of lambda/2 in relation to a space (h) between the end face 6 of the vibrator 1 and the end face 7 of the laser 2 is obtained. This light output 10 is detected by the photo-detector 3 and the natural frequency of the vibrator 1 is measured therefrom. By integrating a frequency detecting system with the vibrator 1, a light-excited vibrator type sensor is made small in size, inexpensive and easy to use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optically excited oscillator type sensor used for measuring pressure, temperature, displacement, flow rate and the like.

[0002]

2. Description of the Related Art FIGS. 6 (1) and 6 (2) are schematic diagrams of a conventional photo-excited oscillator type sensor using a knife edge method and an interferometry method (blade: "application of photothermal vibration to nondestructive optical measurement"). Optics, 19, PP. 85-90, 1990)
Is. In the case of FIG. 6 (1), the semiconductor laser 2 for vibration excitation is used.
In step 4, the oscillator 21 is irradiated with a light pulse having its natural frequency through the condenser lens 25 to generate thermal stress in the thickness direction of the oscillator 21 to excite the natural vibration, while the semiconductor laser 22 for detection vibrates. The vibrating part of the child 21 is irradiated, and the positional deviation of the reflected light is detected by the photodetector 23 through the knife edge 26 by the same principle as the focus error detection of the optical disk. Oscillator 2
The natural frequency of 1 changes depending on the pressure applied to the vibrator 21, the temperature, and the like. This type of sensor has a feature that the measurement sensitivity is extremely high because it measures their quantity from changes in the frequency. FIG. 6B shows an optical path conversion mirror 27 and an interferometer 28 in place of the detection semiconductor laser 22, knife edge 26, and photodetector 23. The interferometer 28 vibrates through the optical path conversion mirror 27. The child 21 is irradiated with a light beam, and the natural frequency of the vibrator 21 is measured from the interference between the reflected light and the internal light.

FIG. 7 shows an example in which the photoexcited oscillator type sensor of FIG. 6B is applied to a pressure sensor. The oscillator 21 is manufactured by the anisotropic etching technique of Si,
1a and a diaphragm spring 21b. The natural frequency of the vibrator 21 due to the pressure difference between the portions 30 and 31 is detected by the interferometer 28 shown in FIG. 6B through the optical fiber 29. The oscillation pumping semiconductor laser 24 has an optical output of 2.25 mW, and irradiates a region on the oscillator 21 having a diameter of about 60 μm.

[0004]

In the above-mentioned conventional photoexcited oscillator type sensor, the oscillator itself is small, but since the vibration excitation system and the frequency detection system are both separate configurations and are large in size, they are expensive. It had the drawback of being difficult to use. An object of the present invention is to provide a photoexcited oscillator sensor that is small, inexpensive, and easy to use.

[0005]

A first optically excited vibration type sensor according to the present invention vibrates from a vibrator and an optical output based on interference between reflected light and internal light when the vibrator is irradiated with a light beam. A semiconductor laser with a photodetector that detects the natural frequency of the child is integrated on the same substrate. A second optically excited vibration type sensor of the present invention is a vibrator, a vibration excitation semiconductor laser for exciting a natural vibration of the vibrator, and a light beam irradiating the vibrator to cause interference between reflected light and internal light. A semiconductor laser with a photodetector that detects the natural frequency of the vibrator from the optical output based on the above is integrated on the same substrate.

A third optically excited vibration type sensor of the present invention is a vibrator, a vibration excitation semiconductor laser for exciting a natural vibration of the vibrator, and a light beam of the vibration excitation semiconductor laser on the vibrator. A first lens for condensing, a second lens for detecting the vibration state of the vibrator, and a light beam irradiating the vibrator through the second lens, and passing through the second lens A semiconductor laser with a photodetector that detects the natural frequency of the vibrator from the optical output based on the interference of the reflected light that returns and the internal light is integrated on the same substrate.

[0007]

In the present invention, the principle of the vibration excitation system is the same as the conventional one, but the frequency detection system utilizes the complex resonance action when the reflected light from the oscillator returns to the semiconductor laser with photodetector. ing. In this method, since the end face of the oscillator and the output end face of the semiconductor laser with photodetector form a compound resonator, the optical output of the semiconductor laser for detection is λ /
It changes with a cosine function with a period of 2 (λ: optical wavelength). That is, the change in the intrinsic number of the oscillator is detected from the change in the optical output of the detection semiconductor laser.

In the first photoexcited oscillator type sensor, the oscillator and the frequency detection system are integrated, and in the second and third photoexcited oscillator type sensors, the oscillator, the frequency detection system and the vibration excitation system are integrated. As a result, the photoexcited oscillator sensor is small and inexpensive, and is easy to use. Further, in the third photoexcited oscillator type sensor, since the distance between the vibration excitation system and the frequency detection system can be widened, the photoexcited oscillator type sensor can be easily manufactured.

[0009]

Embodiment 1 Next, an embodiment of the present invention will be described with reference to the drawings. 1 (1) is a plan view of an optically excited oscillator type sensor according to a first embodiment of the present invention, FIG. 1 (2) is a side view thereof, FIG. 1 (3) is a signal detection principle diagram, and FIG. 1 (4). FIG. 4 is a waveform diagram of the optical output 10.

In the present embodiment, the oscillator 1, the detecting semiconductor laser 2 for irradiating the oscillator 1 with a light beam in its continuous oscillation state, and the optical output 10 of the detecting semiconductor laser 2 determine the natural vibration of the oscillator 1. The photodetector 3 for detecting the number is integrated on the same substrate. A portion of the detection semiconductor laser 2 surrounded by a broken line is a waveguide region, and the end surface 7 of the detection semiconductor laser 2 and the end surface 6 of the vibrator 1 face each other. An insulating groove 5 is formed between the detection semiconductor laser 2 and the photodetector 3 to electrically insulate the two. The semiconductor laser 2 for detection and the photodetector 3 form a semiconductor laser with a photodetector.

The oscillator 1 is pulse-irradiated with a laser beam (not shown) to horizontally excite the oscillator 1 to its natural vibration. On the other hand, as shown in FIG. 1C, when the detecting semiconductor laser 2 irradiates the oscillator 1 in the continuous oscillation state from the opposite side, the reflected light 8 returns to the detecting semiconductor laser 2. The reflected light 8 interferes with the internal light 9, and as shown in FIG. 1 (4), λ / 2 (λ: light) with respect to the distance h between the end face 6 of the vibrator 1 and the end face 7 of the vibration detecting semiconductor laser 2. A light output 10 that changes with a cosine function with a cycle of (wavelength) is obtained. The optical output 10 of the semiconductor laser 2 for detection is detected by the photodetector 3, and the natural frequency of the vibrator 1 is measured. The optical output 10 is moved from the detection semiconductor laser 2 to the oscillator 1 as the interval h increases.
Since the light beam radiated to the laser spreads around, the amplitude gradually decreases. Further, the interval h is invariable with respect to the vibration of the vibrator 1 in the vertical direction, and the natural frequency of the vibrator 1 is measured from the composite resonance action due to the magnitude of the reflected light 8.

The groove of the insulating groove 5 is formed by reactive ion beam etching. Substrate material is G instead of Si
A semiconductor laser material such as aAs or InP is used. A selective etching method is applied to manufacture the vibrator 1. This is because an etch stop layer with a greatly different etching rate is formed in advance when forming a semiconductor laser crystal,
This is because when the etching reaches the layer, the etching no longer proceeds in the vertical direction but in the lateral direction, and the lower portion is scooped to form the vibrator 1. This depth is, for example, 8 μm, and the substrate thickness of the photoexcited oscillator type sensor is about 100 μm.
The size is about 500 × 500 μm.

FIG. 2 (1) is a plan view of an optically excited oscillator type sensor according to a second embodiment of the present invention, and FIG. 2 (2) is a side view thereof. In this embodiment, the oscillation excitation semiconductor laser 4 is integrated with the photoexcitation oscillator type sensor of the first embodiment, and the operation principle is the same as that of the first embodiment. FIG. 3 (1) is a plan view of an optically excited oscillator type sensor according to a third embodiment of the present invention.
(2) is a side view thereof.

In the second embodiment, since the detection is performed in the end face region where the light beam does not spread, it is necessary to form the vibrator 1 between the vibration excitation semiconductor laser 4 and the detection semiconductor laser 2 at a distance of about 10 μm. Therefore, the structure is simple, but the fabrication requires high technology. Therefore, in the present embodiment, the distance is increased to facilitate the production, and the oscillator 1, the vibration excitation semiconductor laser 4, the lens 11 for condensing the light beam of the semiconductor laser 4 on the oscillator 1, the vibration. The lens 12 for detecting the state, the photodetector 3, and the semiconductor laser 2 for detection are integrated. Lens 1
Dielectric materials such as Si ₃ N ₄ and SiO ₂ can be used for 1 and 12.

FIG. 4 (1) is a plan view of an optically excited oscillator type sensor according to a fourth embodiment of the present invention, and FIG. 4 (2) is a sectional view thereof. Although the vibrator 1 is a cantilever in the first, second, and third embodiments, it is a cantilever in this embodiment, which increases the strength of the vibrator 1. Oscillator 1
Is a portion of 13 and is lifted from the substrate 14 as shown in FIG. In addition, the digging 15 on the back side of the substrate 14
Thus, the diaphragm 16 is formed to form a resonance system with the vibrator 1. This increases the sensitivity. Oscillator 1
Is made of the same GaAs and InP as the semiconductor lasers 2 and 4.
Or the same material as the lenses 11 and 12
_{A 3} N ₄ or SiO ₂ dielectric may be used.

FIG. 5 (1) is a plan view of an optically excited oscillator type sensor according to a fifth embodiment of the present invention, and FIG. 5 (2) is a side view thereof. In this embodiment, the optical axis 1 of the vibration excitation semiconductor laser 4 is used.
7 and the optical axis 18 of the detection semiconductor laser 2 are shifted from each other to prevent the light of the vibration excitation semiconductor laser 4 from entering the detection semiconductor laser 2 and prevent the deterioration of the signal detection characteristics. . Although this embodiment has been described with respect to the second embodiment, it can be similarly applied to the third and fourth embodiments.

[0017]

As described above, the present invention has the following effects. (1) According to the first aspect of the invention, by integrating the frequency detection system with the vibrator, the photoexcited vibrator type sensor is small and inexpensive, and is easy to use. (2) According to the second aspect of the present invention, by integrating the vibration frequency detection system and the vibration excitation system with the vibrator, the photoexcited vibrator sensor is small and inexpensive, and is easy to use. (3) According to the invention of claim 3, by integrating the frequency detection system and the vibration excitation system with the vibrator, the photoexcited vibrator type sensor is small and inexpensive, and is easy to use. Furthermore, the vibration excitation semiconductor is used. By providing the lens for condensing the laser light beam on the oscillator and the lens for detecting the vibration state of the oscillator, the photoexcitation oscillator sensor can be easily manufactured. (4) According to the invention of claim 4, the optical axis of the vibration exciting semiconductor laser and the optical axis of the detecting semiconductor laser are shifted from each other, whereby in addition to the effects of (2) and (3), deterioration of the signal detection characteristic is caused. Can be prevented.

[Brief description of drawings]

FIG. 1 is a plan view (FIG. 1 (1)), a side view (FIG. 2 (2)), and an explanatory view of a signal detection principle (FIG. )) And a waveform diagram of the optical output 10 ((4) in the same figure).

FIG. 2 is a plan view (FIG. 1 (1)) and a side view (FIG. 2 (2)) of an optically excited oscillator type sensor according to a second embodiment of the present invention.

FIG. 3 is a plan view (FIG. 1 (1)) and a side view (FIG. 2 (2)) of an optically excited oscillator type sensor according to a third embodiment of the present invention.

FIG. 4 is a plan view (FIG. 1 (1)) and a side view (FIG. 2 (2)) of an optically excited oscillator type sensor according to a fourth embodiment of the present invention.

FIG. 5 is a plan view (FIG. 1 (1)) and a side view (FIG. 2 (2)) of an optically excited oscillator type sensor according to a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram of a conventional optically excited oscillator type sensor.

FIG. 7 is a diagram showing an example in which the conventional photoexcited oscillator type sensor of FIG. 6 (2) is applied to a pressure sensor.

[Explanation of symbols]

1 oscillator 2 Semiconductor laser for detection 3 Photodetector 4. Semiconductor laser for vibration excitation 5 Insulation groove 6 End face of transducer 1 7 End face of semiconductor laser 2 for detection 8 reflected light 9 Internal light 10 Optical output of semiconductor laser 2 for detection 11,12 lens 13 parts 14 board 15 digging 16 diaphragm 17 Optical axis of semiconductor laser 2 for detection 18 Optical axis of semiconductor laser 4 for vibration excitation 21 oscillator 22 Semiconductor laser for detection 23 Photodetector 24 Semiconductor laser for vibration excitation 25 lenses 26 knife edge 27 Optical path changing mirror 28 Interferometer 29 optical fiber 30,31 parts

Claims (4)

[Claims] 1. A vibrator and a semiconductor laser with a photodetector for irradiating the vibrator with a light beam and detecting the natural frequency of the vibrator from the optical output based on the interference between the reflected light and internal light. Optically excited oscillator sensor integrated on the same substrate. 2. A vibrator, a vibration-exciting semiconductor laser that excites a natural vibration of the vibrator, and a light beam emitted to the vibrator, and the vibration is generated from an optical output based on interference between reflected light and internal light. A photo-excited oscillator sensor in which a semiconductor laser with a photodetector that detects the natural frequency of a child is integrated on the same substrate. 3. A vibrator, a vibration exciting semiconductor laser for exciting a natural vibration of the vibrator, and a first lens for focusing a light beam of the vibration exciting semiconductor laser on the vibrator. A second lens for detecting the vibration state of the vibrator, and an interference between the reflected light and the internal light that irradiates the vibrator with a light beam through the second lens and returns through the second lens. A photoexcited oscillator-type sensor in which a semiconductor laser with a photodetector that detects the natural frequency of the oscillator from the optical output based on the above is integrated on the same substrate. 4. The optically excited oscillator type sensor according to claim 2, wherein the optical axis of the vibration exciting semiconductor laser and the optical axis of the detecting semiconductor laser of the semiconductor laser with a photodetector are deviated from each other.