JPH03140807A - Optical position sensor - Google Patents

Abstract

PURPOSE: To simplify the configuration and to improve the detection accuracy by determining the resonance frequency of input light that is subjected to amplitude modulation based on a detection signal, generating maximum light intensity in a resonator, and relating the resonance frequency to the length of the resonator. CONSTITUTION: The light of a light source 42 is transmitted to a coupler 34 via an optical path 38 and most light is transmitted to an optical fiber 36, but one portion is transmitted to a photodetector 44 via an optical path 40. Then, the light source light that is transmitted to the optical fiber 36 reaches an entrance port 16 via an optical connector 30, an optical fiber 46, an optical connector 32, and an optical fiber 28. Then, the light source light that is transmitted into a position detection device 10 from the port 16 is transmitted into an optical path 12 via the delay line part of an optical path 14 that forms one portion of a path with a variable path. Then, light source light through the path 12 is reflected by a mirror 22 of a disk 24, and the reflection light is detected by the photodetector 44 via the paths 12 and 14, an output port 18, an optical fiber 28, light connectors 32 and 30, an optical fiber 36, a coupler 34, and a path 40.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical position detection device, and more particularly, the present invention relates to a device for measuring a straight line distance using a variable-length optical path. It is something.

[Prior Art] Optical position detection devices are suitable for use in control systems for aircraft and the like that require sensors that are lightweight and unaffected by interference. However, optical position detection devices have the drawbacks of being complex and expensive.

In recent years, several optical position detection devices using optical fibers have been proposed. The most advanced of these optical position sensing devices uses a plate with a digitally encoded surface to deliver a binary pattern of light into a fiber optic channel. . In this technique, a large number of optical fibers are required because each optical fiber channel corresponding to each bit of binary data requires an optical fiber arranged in parallel. In this technique, since the data is digitized, the influence of noise can be removed without degrading position detection performance. Further, as another method, there is a method in which the information is amplitude information of - or a plurality of channels. However, with this method, amplitude fluctuations pose a problem when an optical connector is used to connect the optical fibers. moreover. A multiplexing technique based on time domain and wavelength has also been proposed, as shown in U.S. Pat. No. 4,546,466.

[Problems to be Solved by the Invention] However, conventionally proposed devices have not been able to obtain satisfactory results in reducing the cost of optical position detection devices.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical position detection device that has a simple structure, can be manufactured at low cost, and has high detection accuracy.

[Means for Solving the Problems] In order to achieve the above and other objects, according to a first configuration of the present invention, amplitude-modulated input light is transmitted to a passive optical resonator with a variable optical path length. supplying the input light to resonate the input light at a frequency corresponding to the optical path length of the optical resonator, detecting the output light of the passive optical resonator, and generating a detection signal indicative of the detected light intensity; determining the resonant frequency of the amplitude-modulated input light based on the resonator, generating the maximum light intensity within the resonator, and linking the resonant frequency and the length of the resonator. A method of adjusting the frequency of input light in a system is provided.

Further, according to the second configuration of the present invention, a passive optical resonator has an optical path length that changes depending on the distance to the detection position, and a passive optical resonator that changes the resonant frequency according to the optical path length; an input port for introducing amplitude-modulated input light into the resonator; and detecting the amplitude-modulated input light and resonance frequency, which indicates the brightness within the resonator and whose wavelength changes according to the optical path length of the resonator. An optical position detecting device is provided, characterized in that it is configured by an output port that generates output light for the purpose of the present invention.

Furthermore, according to a third configuration of the present invention, an optical delay line has an input/output end and a detection end, and has a refractive index that substantially matches the refractive index of a fluid in a detection chamber into which the detection end is inserted; Displaced in the detection chamber with respect to the detection end of the optical delay line in the positional relationship with the detection target provided in the detection chamber, introduced from the input end, reflects the input light, and causes interference between the input light and the reflected light. and a mirror surface member that forms output light, and further characterized in that the input/output end of the optical delay line has a mirror surface.

Note that in the third configuration of the present invention described above, there is provided an input side optical fiber that transmits the amplitude-modulated input light generated by the light source means to the input/output end, and an input side optical fiber that transmits the output light to the detector. It is also possible to provide an output side optical fiber for transmitting. Further, a variable capacity chamber communicating with the detection chamber may be provided, and the amount of the fluid may be adjusted to increase or decrease in response to a change in the capacity of the detection chamber due to displacement of the mirror member within the detection chamber.

Furthermore, according to a fourth configuration of the present invention, a passive optical resonator has an optical path length that changes depending on the distance to the detection position, and has a resonant frequency that changes in accordance with the optical path length; an input port for introducing amplitude-modulated input light into the resonator; An optical position detection device is provided, comprising: an output port that generates output light for detecting a resonant frequency of input light.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an optical position detection device l according to an embodiment of the present invention.
, and this position detection device IO is connected to an optical path 12.
．． 14 and a common inlet port 16 and outlet port 18. The optical passageway 14 constitutes a fiber optic delay line and has a mirror finish on its entrance and exit ends.

The mirrored surfaces at the inlet and outlet ends have a refractive index that matches the refractive index of the fluid contained within the optical passageway 12.

On the other hand, the optical passage 12 is constituted by a hollow cylinder. The end of this optical path 12 is sealed by a movable disk 24 having a mirror surface 22. One end of the rod or piston 26 is joined to the movable disk 24, and the other end of the rod or piston 26 is brought into contact with a position detection target.

FIG. 2 shows the optical path 14 of the optical position detection device of FIG.
This figure shows the state of the delay line section viewed from the inlet end and outlet end sides. Small circular recesses in the mirror-finished surfaces of the entrance and exit ends of the optical passage 14 are formed by etching or the like. The end of the optical fiber 28 is abutted against this recess and is connected to the delay line portion of the optical path 14 by heating and melting. It is also possible to adhere the optical fiber 28 to the delay line portion of the optical path 14 with an optical adhesive.

Note that in this embodiment, the optical fiber 28 functions as both an input line and an output line of the optical position detection device.

Optical fiber 28 is connected to an optical coupler or combiner splitter 34 . Note that between the position detection device lO and the coupler 34,
- to a plurality of optical connectors 30, 32 can be interposed. In particular, when the optical position detection device is used in an aircraft or the like, it is necessary to use optical connectors 30, 32 in order to arrange the optical fiber 28 in a complicatedly curved optical fiber path. The coupler 34 has two optical paths 38, 40 formed of optical fibers, thereby forming two branches.

In the optical system shown in FIG.
2, and the source light is transmitted through this optical path 38 to the coupler 34. Most of the light transmitted from optical path 38 to coupler 34 is transmitted to optical fiber 36, but some of it is returned to light source 42 via optical path 38, and another portion is transmitted through optical path 40. via photodetector 4
4.

The light source light transmitted from the coupler 34 to the optical fiber 36 is
Optical connector 30, optical fiber 46, optical connector 32
and reaches the input port 16 through the optical fiber 28. The light source light transmitted into the position detection device 10 through the inlet port 16 is transmitted through the optical path 1 forming a part of the variable length path.
4 and is transmitted into the optical path 12 from the end of this delay line section. The refractive index of the fluid in optical passage 12 matches or nearly matches the refractive index of the delay line of optical passage 14, so that the boundary between the delay lines of optical passage 12 and optical passage 14 is transparent. And the light source light is
The light is not reflected at this boundary portion and is introduced into the optical path I2. The light source light passes through the optical path 12 and reaches the disk 2.
The light reaches the mirror surface 22 of No. 4 and is reflected by this mirror surface 22. The reflected light reflected by the mirror surface 22 passes through the optical path 12, the boundary between the delay line between the optical path 12 and the optical path 14, and the optical path 1.
4 delay line, and exit port 18.

The reflected light further passes through optical fiber 28 , optical connector 32 , optical fiber 46 , optical connector 30 , optical fiber 36 , optical path 40 and is detected by photodetector 44 .

FIG. 5 shows an optical position detection device according to another embodiment of the invention. In this embodiment, the variable length optical path includes an optical delay line 14a inserted into a liquid-filled hollow tube 20a. This optical delay line 14
The refractive index of a corresponds approximately to the refractive index of the liquid sealed in the hollow tube 20a. A mirror disk 22a is displaceably housed in the hollow tube 20a. The mirror disk 22a is attached to the tip of the rod 26a, and the other end of the rod 26a is attached to the object to be detected.

The detection device 10a shown in FIG.
8 is provided. This liquid container 128 is stretchable and compensates for changes in the amount of liquid contained in the hollow tube depending on the position of the mirror disk 22a within the hollow tube 20a. Therefore, the liquid storage chamber and liquid container of the hollow tube 201 are connected to the mirror disk 22a and the hollow tube 20 &
They communicate through a gap formed between the inner circumferential surfaces of the two. The rod 26a extends through one side wall of the liquid container 128, and a sealing member 50 is provided at the opening of the container through which the rod 26a passes, forming a liquid-tight seal. . Furthermore, an opening through which the hollow tube 20a is inserted is formed in the other side wall of the liquid container 128, and a sealing member 52 is provided in this opening to form a liquid-tight seal. At least a portion of the side wall in the axial direction of the liquid container has a flexible portion 54 formed in a bellows shape or the like.
This allows the container 128 to expand and contract.

The container itself can be made of a stretchable material, or it can be made of metal with at least a portion shaped like an accordion or bellows to give it stretchability. It may be formed.

Note that various methods can be considered as means for changing the lengths of the optical passages 12 and 12a in FIGS. 1 and 5. For example, by surrounding the optical passageway 12.12a to form an outer container and communicating the outer container with the optical passageway, the amount of fluid in the optical passageway can be compensated to maintain a constant fluid pressure in the optical passageway. It is possible to have a configuration that allows displacement of the disk. The position detection device 10a shown in FIG.
Inlet port 16a and outlet port 18a separated from each other
are formed, and these ports 16a, 18a are connected to separately provided optical fibers 56, 58, respectively. Optical fiber 5 connected to inlet port 16a
6 is connected to a light source 66 via an optical connector 68, an optical fiber 66, an optical connector 64, and an optical fiber 62. On the other hand, the optical fiber 58 connected to the exit port 18a is connected to the detector 74 via an optical connector 72, an optical fiber 70, an optical connector 78, and an optical fiber 76. Note that the separately formed inlet port 16a
As shown in FIG. 3, the exit port 18a can be formed by different parts of the open lower portion 9, which are formed by etching or the like at the end of the optical delay line 14a. Note that the configuration of the inlet port 16a and the outlet port 18a is as follows.
The present invention is not limited to the configuration shown in FIG. 3, and it is of course possible to use the configuration shown in FIG. 4, which will be described later in connection with the embodiment shown in FIG. 6, for example. Moreover, the optical fiber 56.58 is
Similar to the configuration shown in FIG. 1, it is connected to the inlet port 16a and the outlet port 18a by welding it in contact with the inlet port 16a and the outlet port 18a, or by adhering it using an optical adhesive.

The configuration of the position detection device 10a shown in FIG.
It can also be used for tuning 2a. That is, optical path 1
If the optical path length of the optical delay line 2a is a (variable) and the optical path length of the optical delay line 14a is b (fixed), then the optical path length of the entire optical path is λ
+b, and the intensity of the light introduced into the optical path is λ = 2(a + b) / n, where n satisfies the formula of an integer, in order to cause constructive interference with the brightness modulation of the reflected light. can be modulated to a frequency with a wavelength (λ) of A phase-locked loop (PLL) 80 can be used to modulate the input source light into a continuous wave. A PLL 81 similar to this PPL can also be used in the configuration shown in FIG. The modulation frequency is adjusted to the resonant frequency.

The wavelength of light at the resonant frequency is 2(a+b) described above.
/n, which is a value proportional to the position of the detection target.

FIG. 6 shows an optical position detection device tab according to a third embodiment of the present invention, except that a liquid container 82 is provided on the optical delay line 14b side of a hollow tube 86. , has the same structure as the embodiment shown in FIG. 5 above. The liquid container 82 in this embodiment is configured to continuously expand and contract from the current state shown by the solid line to the extended position shown by the broken line. Therefore, the structure of the liquid container 82 is such that its volume can be changed continuously. Note that since various types of expandable and contractible liquid containers themselves have been known in the past, a description of their specific configurations will be omitted. Note that this liquid container 82 can compensate the amount of liquid in the hollow tube 86 and keep the pressure in the hollow tube constant regardless of the position in the hollow tube of the input shaft joined to the detection object 15 Any configuration can be used. In this embodiment, the liquid container and the liquid chamber in the hollow tube 86 are defined by the inner peripheral surface of the hollow tube 86 and the optical delay line 14b.
They are communicated through a gap formed between them.

In this embodiment, a rod-shaped piston 88 is used, and one end of this piston 88 is connected to a hollow tube 86.
The other end is connected to the position detection target. End face 9 located within hollow tube 86 of piston 88
0 has a mirror finish. The piston 88 is configured such that the position of the mirror-finished surface 90 within the hollow tube 86 changes depending on the position of the detection target.

The light source 92 includes an optical fiber 94, an optical connector 112, an optical fiber 96, an optical connector 114, and an optical fiber 98.
It is connected to the input port 100 via. Note that in this embodiment, the optical delay line 14b is an optical fiber 98.
etc., and is formed to have a larger cross section than the optical fiber 98 in order to provide the exit port 102.

16 The exit port 102 is an optical fiber 106, an optical connector! 18, is connected to the detector 104 via an optical fiber 108, an optical connector 116, and an optical fiber 110, and the reflected light reflected by the mirror-finished surface 90 is transmitted to the detector 1.
Transmit to 04.

Note that, as described above, the optical connector is provided as necessary, and the optical position detection device according to the present invention does not necessarily require the provision of this.

FIG. 4 shows the optical position detection device 1 according to the embodiment of FIG.
0b shows the end of the optical delay line 14b. As shown in FIG. 4, the inlet port 100 and the outlet port 102 are
It consists of four small circular parts formed by etching, etc., and the end surfaces are mirror-finished. Therefore,
The reflectance of the end face on the left side of FIG. 6 of the optical delay line 14b is "l"
It is smaller than. On the other hand, the reflectance of the mirror-finished surface 90 of the piston 88 is approximately "1".

In the optical position detection device 10b shown in FIG. 6, the detector 10 is
It is possible to hold the vibration detected as the maximum detection intensity of 4.

As shown by the arrow in FIG. 6, the light source light introduced from the inlet port 100 is reflected on the inner circumferential wall surface of the optical delay line 14b and the inner circumferential wall surface of the optical passage 12b, and then hits the mirror-finished surface 90 of the piston 88. The light reaches the mirror-finished surface 90 and is reflected by the mirrored surface 90 to head toward the exit port 102 as reflected light. In the configuration shown in FIG. 6, if the optical path length of the optical path with respect to the wavelength of the light source light is set appropriately, constructive interference will occur between the light source light and the reflected light. As a result, the maximum light intensity at the detector 104 can be obtained, and the information necessary for detecting the position of the detection target can be obtained. Note that in actual position detection, the position is calculated based on information such as the optical path length of the optical path and the length of the piston and information obtained by the detector 104.

FIG. 7 shows the control circuit 10 of the optical position detection device described above.
6, and this control circuit 106 is used in the device shown in FIG. 6 that generates continuous waves.

- The illustrated control circuit is the PLL shown in FIGS. 1 and 5.
It can also be used to control

Optical path 1 in the detector 104 in the apparatus of FIG.
When trying to select a frequency that maximizes the light intensity output from 2b and 14b, a variable frequency generator is used to variously change the frequency of the light source light generated from the light source 92 and then introduced into the optical path. It is common to perform brightness modulation by In this case, the frequency must be continuously varied over a wide range to detect the frequency at which the output is maximum. In this operation, first, the frequency is continuously varied over a wide range, the frequency region where the output is close to the maximum is detected, and within this frequency region, the frequency is finely adjusted to find the frequency where the output is the maximum. Accurate detection is performed.

The control circuit shown in FIG. 7 automatically performs the above operations. FIG. 8 shows changes in the output waveform according to changes in frequency during this operation process. In FIG. 8, waveform 10
B shows the change in output from the optical path as a function of frequency change over a distance. Waveform 110 of FIG. 8 also shows the optical path power change at another distance, and waveform 112 shows the power change at an even different distance. Note that the distance in waveform 110 and the distance in waveform 112 indicate distances at positions displaced in opposite directions with respect to the distance in waveform 108, respectively. For example, if the distance obtained by waveform 110 is shorter than the distance obtained by waveform 108, the distance obtained by waveform 112 is longer than the distance obtained by waveform 10B. The operation of the control circuit shown in FIG. 7 is similar to manual frequency detection, in which the peak frequency on the oscilloscope is detected by operating the oscillator to drive the resonator. In order to automatically perform this peak detection, a method is adopted in which a dither operation is performed at frequency fm, and the amount of change in frequency with respect to the current frequency, which is proportional to the difference, is calculated to determine the center frequency fc.

When the frequency setting operation is started, first, the control circuit 106
operation mode becomes scan mode, switch 200
The step signal generator 204 selects the step signal supplied to the signal line 202 from 0 to
A step signal is provided to an integrator 206.

Integrator 206 provides an integral signal to adder 210 via signal line 208 . The addition output of this adder 210 is
A voltage controlled oscillator (VCO) 212 is provided. The voltage controlled oscillator 212 is connected to the light source 9 shown in FIG.
The frequency of the light source drive signal supplied to 2 is changed stepwise from a low frequency to a high frequency. The operation in this scan mode corresponds to a scan operation in a wide frequency range by manual adjustment.

Peak detector 214 and comparator 216 detect frequencies near the center frequency fc at which the output of the optical path is maximum. In this operation of the peak detector 214, the peak frequency is updated sequentially, and when the output of the optical path starts to fall, this is detected and the comparator 216 is activated. At this time,
Flip-flop 218 is triggered and switch 200 is switched to the fine adjustment mode position. This operation mode switching operation corresponds to an operation of switching manual operation to manual fine adjustment after detecting a frequency near the peak.

In the fine adjustment mode of operation, the envelope detector 22
0 generates a current frequency detection signal with an amplitude indicative of the current frequency f, and supplies this to the synchronous demodulator 222. Tuning demodulator 222 generates an error signal if the frequency set by voltage controlled oscillator 212 does not match the peak frequency.

The error signal of the synchronous demodulator 222 is supplied to the integrator 206, and the integrated signal of this integrator causes the voltage controlled oscillator 21
2 to adjust the frequency supplied to the light source 92 to the peak frequency. To fine-tune the frequency at this time, the local oscillation output oscillated by the local oscillator 224 is given to the adder 210, and the signal component of the local oscillation output is superimposed on the integral signal of the integrator 206 to be sent to the voltage controlled oscillator 212. This essentially performs a dithering operation.

The output of voltage controlled oscillator 212 is also provided to a frequency-to-digital (F/D) converter that is externally connected to the illustrated control circuit.

FIG. 9 shows the modulation frequency fm oscillated from the local oscillator 224, and the waveform of this modulation frequency is
This corresponds to the waveform of the signal supplied to 28. Signal line 2
The local oscillator output supplied to 28 functions as a dither signal and is connected to optical path 12b.

A dither operation is performed to detect the frequency (center frequency fC) at which the output of 14b becomes maximum. At this time, the amplitude of the local oscillation output of the local oscillator 224, which functions as a dither signal, corresponds to the signal value of the error signal output from the synchronous demodulator 222 to the integrator 206.

By the frequency adjustment operation of the control circuit 106 described above, the frequency of the light source light supplied from the light source 92 becomes exactly the same as the frequency at which the maximum light intensity is obtained at the detector 104. The accuracy is sufficient to accurately detect the position.

FIG. 10 shows signal waveforms in each part of the control device in FIG. 7. The signal waveform 3 240 in FIG. This shows the output waveform when not doing so. Usually, the brightness modulation frequency is performed in units of 50 MHz. This normal brightness modulation frequency corresponds to a wavelength of 4 m within the optical fiber. Therefore, when the length adjustment unit of the hollow tube 86 in FIG. 6 is several cm, the adjustment unit is slightly shorter than 4 m for the entire wavelength of the light source light of the optical delay line 14b. Of course, the length of the optical delay line 14b is set to be a fraction of the wavelength of the light source light, and is set so as to cause constructive interference as described above.

A waveform 242 in FIG. 10(b) shows the signal waveform of the signal line 228. The local oscillation output supplied from the local oscillator 212 to the signal line 228 is in units of several KHz, such as 3 KHz, and corresponds to an optical wavelength of 100°000 m. Therefore, FIGS. 1θ (a) and (b) are shown on different time axes. In the illustrated example, the tenth
The time axis in FIG. 10(b) is compressed to 1/2083 of the time axis in FIG. 10(a). FIG. 104(c) shows a waveform obtained by adding the basic modulation frequency fc and the dither frequency fm. Waveform 24 in Figure 1θ (c)
4 is not shown to the exact scale, but is shown on approximately the same time axis as FIG. 1O(a). Note that the waveform 244 in FIG. 10(c) is similar to the signal line 22 in FIG.
6 signal waveforms.

The waveform 246 in FIG. 1O(d) represents the current optical path 12b.
, 14b shows a signal waveform whose amplitude is modulated according to the frequency transfer characteristics of the signals. In Figure 10, 1θ diagram (a)
Assume that the carrier frequency shown by waveform 240 does not correspond to the center frequency of the frequency transfer characteristic of the optical path. In this case, the error signal shown in FIG. 9 is generated.

Waveform 248 in FIG. 10(e) shows the signal waveform of the signal supplied from envelope detector 220 in FIG. 7 to signal line 250. Envelope detector 220 detects amplitude modulation due to the dither. Waveform 240 as above
Assuming that the carrier frequency shown by does not correspond to the center frequency of the frequency transfer characteristic of the optical path, the dither generates a second harmonic pulse and a harmonic pulse at the dither frequency whose average is zero at the envelope detector 220. be done.

The synchronous demodulator 222 compares the envelope detected by the envelope detector 220 with the dither frequency itself, and sends a signal having a waveform 250 shown in FIG. 10(f) to the signal line 230.
supply to. The synchronous demodulator 222 acts as a multiplier, detects the polarity of the local oscillation output on the signal line 228 oscillated from the local oscillator 224, and increases the signal on the signal line 250 by +1.
Or multiply by -1.

Further, the synchronous demodulator 222 filters the signal on the signal line 230 and supplies a filtered error signal having a waveform 252 in FIG. 10(g) to the signal line 230.

FIG. 11(a) to FIG. 11(g) shows the waveform of the same signal as each signal in FIG. 10 when the carrier frequency matches the center frequency of the frequency transfer characteristic of the optical path. There is. Therefore, the envelope detection output of envelope detector 220 is shown by waveform 260 in FIG. 11(e). At this time, only the second harmonic of the dither frequency is generated in the envelope detection output. Therefore, the error signal output from the synchronous demodulator 222 is as shown in FIG.
It becomes zero as shown in Figure 1 (g).

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an optical position detection device with a simple configuration and high detection accuracy.

Note that the present invention is not limited to the above-described configuration, but includes all configurations that do not deviate from the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram schematically showing an optical position detection device according to a first embodiment of the present invention, FIGS. 2 to 4 are diagrams showing the coupling state of an optical path and an optical fiber, and FIG. , a circuit diagram schematically showing an optical position detecting device according to a second embodiment of the present invention, FIG. 6 is a circuit diagram schematically showing an optical position detecting device according to a second embodiment of the present invention, 27 FIG. is a block diagram of the control circuit used in the embodiment of FIG. 6, FIG. 8 is a diagram showing the relationship between the frequency of light source light and the output of the optical path, and FIG. 9 is a diagram of the control circuit of FIG. 7. Waveform diagrams for explaining the operation. FIGS. 10 and 1f are waveform diagrams showing the waveforms of each part in FIG. 7. 8 → 3 means heat, poverty and frugality) Pause◇

Claims (6)

[Claims] (1) Supplying amplitude-modulated input light to a variable optical path length passive optical resonator, resonating the input light at a frequency corresponding to the optical path length of the optical resonator, and outputting the output from the passive optical resonator. detecting light and generating a detection signal indicating the detected light intensity; determining a resonant frequency of the amplitude-modulated input light based on the detection signal to generate maximum light intensity within the resonator; A method for adjusting the frequency of input light in an optical system, characterized in that the resonant frequency and the length of the resonator are correlated. (2) A passive optical resonator that has an optical path length that changes depending on the distance from the detection position and whose resonant frequency changes in accordance with the optical path length, and an input light that is amplitude modulated into the resonator. an input port for introducing light into the resonator; and an output port for generating output light for detecting a resonant frequency of amplitude-modulated input light that indicates the brightness within the resonator and whose wavelength changes depending on the optical path length of the resonator. An optical position detection device characterized by comprising: (3) an optical delay line having an input/output end and a detection end, and having a refractive index substantially matching the refractive index of the fluid in the detection chamber into which the detection end is inserted; a mirror surface member that is displaced relative to the detection end of the optical delay line in the detection chamber in a positional relationship, is introduced from the input end, reflects input light, and forms output light by interference between the input light and the reflected light; The optical resonator device is further characterized in that the input/output end of the optical delay line has a mirror surface. (4) An input-side optical fiber for transmitting amplitude-modulated input light generated by the light source means to the input/output end, and an output-side optical fiber for transmitting the output light to the detector. 4. A device according to claim 3, characterized in that: (5) A variable capacity chamber communicating with the detection chamber is provided, and the amount of the fluid is adjusted to increase or decrease in response to a change in the capacity of the detection chamber due to displacement of the mirror member within the detection chamber. The device according to item 3 or 4. (6) A passive optical resonator that has an optical path length that changes depending on the distance from the detection position and whose resonant frequency changes in accordance with the optical path length, and an input light that is amplitude modulated into the resonator. an input port to be introduced, and a resonant frequency of the amplitude-modulated input light, which indicates the brightness within the resonator and changes such that the average brightness wavelength shown by the output light is maximum according to the optical path length of the resonator. 1. An optical position detection device comprising: an output port that generates output light;