JP3454870B2 - Optical displacement sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical displacement sensor for optically measuring a displacement amount of an object.

[0002]

2. Description of the Related Art Conventionally, as an optical system for measuring a displacement amount of an object using a semiconductor laser, a Michelson interferometer as shown in FIG. 20 (for example, see "Semiconductor Laser and Optical Measurement" edited by Ichiro Yamaguchi et al. )It has been known.

That is, the laser beam emitted from the semiconductor laser 1 is shaped into a parallel light flux by the first collimator lens 3, and then is irradiated onto the beam splitter 7 via the optical isolator 5 and is split into two directions.

One of the laser beams is reflected from the beam splitter 7 and applied to the fixed mirror 9, and then is reflected again by the fixed mirror 9 toward the beam splitter 7. The other laser beam passes through the beam splitter 7, irradiates a mirror 11 attached to an object (not shown), and is then reflected by the mirror 11 toward the beam splitter 7 again.

The respective laser beams reflected from both mirrors 9 and 11 are recombined by the beam splitter 7 and then condensed on the light receiving element 15 via the condenser lens 13.

In the light receiving element 15, a change state of the light intensity corresponding to the optical path difference between these two laser beams (for example,
The change state of the brightness and darkness of the interference fringes) is detected. The displacement amount (S) of the mirror 11 attached to the object is measured based on the detection data detected by the light receiving element 15.

The optical isolator 5 changes the oscillation mode of the semiconductor laser 1 (mode hopping), or
The return light to the semiconductor laser 1 is blocked in order to prevent adverse effects such as jumps in the oscillation wavelength and fluctuations in laser output.

On the other hand, by irradiating the laser beam from the semiconductor laser 1 to the object to be measured and returning the reflected light from the object to be measured to the semiconductor laser 1, a composite resonator is formed and the object to be measured is formed. Method for measuring the displacement of
No. 25656079) is proposed, and FIG.
Shows the configuration.

As shown in FIG. 21, the laser beam emitted from the semiconductor laser 1 is made into parallel light by the collimator lens 3 and further split by the beam splitter 7 in two orthogonal directions. One of the laser beams is radiated vertically to the external mirror 11 attached to the measured object,
The reflected light returns to the semiconductor laser 1 through a pair of paths with the emitted light. The other laser beam is used by the photodetector 5 to measure its light output.

[0010] External mirror 11 is displaced in the X or -X direction, the phase relationship of the semiconductor laser 1 of the emitted light and the reflected light, each of the displacement is changed by half the oscillation wavelength λ ₀ (λ _0/2) The displacement of the external mirror 11 can be measured by utilizing the change in the intensity of the light output.

[0011]

However, as shown in FIG.
The interferometer as shown in FIG. 2 is configured to combine the lenses 3 and 13, the optical isolator 5, the beam splitter 7, the mirrors 9 and 11 and the like to split or combine the laser beams. Therefore, a large volume is required to assemble the entire optical system, and it is difficult to integrate it as a very small microsensor.

The configuration shown in FIG. 21 also requires the collimating lens 3 and the beam splitter 7 for collimating the laser beam, which limits the miniaturization of the sensor.

Further, in the structure shown in FIG. 21, for example, when an ordinary semiconductor laser having a stripe structure is used, when the amount or phase of light returned to the semiconductor laser changes, the oscillation mode in the semiconductor laser changes ( Due to the mode hopping, the optical output is likely to change. Therefore, regular and light output changes every lambda _0/2 with respect to the displacement X, will be the change in light output by the irregular mode hopping is measured overlap, accurate measurement of displacement It's difficult. Therefore, an object of the present invention is to provide a compact optical displacement sensor capable of highly accurate displacement measurement with an extremely simple structure.

[0014]

In order to achieve such an object, an optical displacement sensor of the present invention includes a vertical cavity surface emitting laser and an optical system including the vertical cavity surface emitting laser and an optical system. Due to a relative position change between the external reflection means, which are opposed to each other and are combined with each other to form a composite resonator, and the vertical cavity surface emitting laser and the external reflection means. Detecting a relative change in position between the vertical cavity surface emitting laser and the external reflection means by measuring the resulting periodic change in laser output or the periodic change in mirror loss of the composite resonator. And a detection means configured as possible. Another optical displacement sensor of the present invention is such that at least two vertical cavity surface emitting lasers formed on the same substrate are opposed to the vertical cavity surface emitting laser without an optical system. External reflection means having at least two reflective regions which are arranged together and are combined with each other to form at least two composite resonators, and for providing the phase shift of the light beam provided in the at least one composite resonator. Periodic changes in two or more laser outputs caused by changes in the relative distance between the optical phase shift means, the vertical cavity surface emitting laser and the reflection surface of the external reflection means, or the composite resonance Of the relative distance between at least two of the vertical cavity surface emitting lasers and the reflection surface of the external reflection means by measuring a periodic change in mirror loss of the external reflection means. And a detection means for detecting for.

[0015]

The relative position change between the vertical cavity surface emitting laser and the external reflection means is changed by the detection means into the relative position change between the vertical cavity surface emitting laser and the external reflection means. It is detected by measuring the resulting periodic change in the laser output or the periodic change in the mirror loss of the composite resonator.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic principle of the present invention will be described below, and then each embodiment to which this principle is applied will be sequentially described. FIG. 1 shows a basic configuration of an optical system, which is a basic principle of the present invention, including a compound resonator configured by combining a vertical cavity surface emitting laser 19 and an external mirror 21. The change in the intensity of the laser light or the change in the mirror loss in this composite resonator is detected by the detecting means 23.

As the detecting method by the detecting means 23, a method of directly detecting the intensity change of the laser beam by the light receiving element 25 or a PN junction potential difference detecting means 27.
External mirror 21 and vertical cavity surface emitting laser 1
9 includes an external mirror caused by relative displacement with
There is known a method of detecting a change in mirror loss of a laser based on a change in carrier density inside the compound resonator.

The phase of the laser light returned from the external mirror 21 is determined by the relative displacement (S) between the external mirror 21 and the vertical cavity surface emitting laser 19, and the wavelength of the laser light (λ ₀ ). The laser light output fluctuates in a cycle of a displacement amount corresponding to ½ of the above.

The displacement amount (ΔL) at this time is calculated by the counting device 2
9 and the calculation device 31. In particular,
The number of fluctuations Nc of the laser light output counted through the counter 29 is input to the arithmetic unit 31. Arithmetic unit 31
Performs arithmetic processing on the input data (Nc) based on the following calculation formula. _{ΔL = Nc · λ 0/2} / n ... (1) n; refractive index value obtained as a result of this operation of the medium between the external mirror 21 and the vertical cavity surface emitting laser 19, the amount of displacement ([Delta] L ). The refractive index (n) is n = 1.0 in the following description on the assumption that it is operated in the atmosphere.
And

The case where the light receiving element 25 is used as the detecting means for detecting the change in the laser light intensity or the change in the mirror loss of the composite resonator will be described below.
Unless otherwise specified, this may be replaced with a detecting means 27 for detecting a change in the mirror loss of the resonator.

Next, in order to explain the more detailed operation principle, as shown in FIG. 2, a vertical cavity having a distributed reflection (DBR) mirror (not shown) as a semiconductor laser that outputs a single mode. A compound resonator to which the surface emitting laser 19 is applied will be described.

In the following description, the oscillation mode of the laser is considered only for the longitudinal mode corresponding to the cavity direction, and the transverse mode in the vertical direction is controlled to be a single mode. Here, in order to control the transverse mode to a single mode, among the cross-sectional dimensions of the waveguide inside the surface-emitting laser, the cross-sectional dimension perpendicular to the resonator is not more than a certain value (10
μm). Here, when the effective cavity length of the vertical cavity surface emitting laser 19 is l _eff and the distance between the laser emission surface and the external mirror 21 is L,

[0023]

[Equation 1]

As shown in FIG.
The characteristics shown in (a) to (c) can be obtained.
As shown in FIG. 3A, the reflectance R of the entire composite resonator is
_{The tot} is caused by the interference between the reflected light from the external mirror 21 (see FIG. 2) and the light resonating inside the vertical cavity surface emitting laser 19, so that the reflectance R _{DBR of the DBR} mirror has a period Δ.
It will be modulated by λ _FP . Where Δλ _FP is λ ₀
Is the oscillation wavelength, under the condition of equation 1,

[0025]

[Equation 2] Given as.

On the other hand, as shown in FIG. 3B, in the vertical cavity surface emitting laser 19 alone, the wavelength interval Δλfp satisfying the phase condition of the cavity is represented by n _eff of the wavelength dispersion of the laser waveguide (not shown) Taking into account the effective refractive index,

[0027]

[Equation 3] Given as.

A DB normally formed by a semiconductor multi-layer mirror (not shown) of the vertical cavity surface emitting laser 19.
Bandwidth Δλ at which the reflectance of R is half of its peak
_{Since the DBR} (see (a) in the figure) is about 20 nm, considering the condition of equation (2)

[0029]

[Equation 4] It turns out that

As typical values, λ ₀ = 0.97 μm, L =
Assuming 100 μm, l _eff = 3.5 μm, and n _eff = 4.3,
Δλ _fp = 31 nm and Δλ _FP = 4.7 nm. In a normal semiconductor laser having a stripe structure, Δλ _fp is 1n
Although about m, in the vertical cavity surface emitting laser, as described above, Δλ _fp is several tens of nm, which is about the same as Δλ _DBR . As shown in, in the wavelength region where the DBR mirror exhibits high reflectance,
Only at most one or two modes satisfy the phase condition of FIG.

Therefore, the vertical cavity surface emitting laser is
It has a feature that the mode is very stable and hardly causes mode hopping. Even in the vertical cavity surface emitting laser having no DBR mirror, Δλ _fp is several tens n.
m, and because of the wavelength dependence of the optical gain of the active layer,
It is known that in the modes having wavelengths different by Δλ _fp , the mode gain difference is large and mode hopping of the laser oscillation mode hardly occurs.

Assuming that the distance L between the external mirror 21 and the vertical cavity surface emitting laser 19 (see FIG. 2) changes by ΔL, the wavelength characteristic of the reflectance R _tot as a compound resonator is as shown in the figure. As shown in 3 (a), it is shifted by δλ _FP ,
The wavelength characteristic is represented by _R'tot .

The shift amount "δλ _FP " can be expressed as δλ _FP = λ ₀ · ΔL / L (6)

In order to oscillate the vertical cavity surface emitting laser 19, it is necessary to suspend the optical gain g _th (cm ⁻¹ ) formed by the active layer constituting the semiconductor laser with the loss of the cavity.

Now, the vertical cavity surface emitting laser 19 is activated.
The thickness of the conductive layer is d, the internal loss of the waveguide is α _i (cm ⁻¹ ),
The mirror loss of the entire resonator normalized by l _eff is α _{m, tot}
(Cm ⁻¹ ), assuming that the reflectances of the mirrors before and after the vertical cavity surface emitting laser 19 alone are R ₁ and R ₂ ,

[0036]

[Equation 5]

[0037]

[Equation 6] It can be expressed as.

Note that β is a factor by which the external mirror 21 modulates the reflectance of the DBR on the front surface of the vertical cavity surface emitting laser 19. This β is determined by the reflectance R _EX of the external mirror 21 and the optical phase and the amount of returned light from the external mirror 21 corresponding to the distance L between the external mirror 21 and the vertical cavity surface emitting laser 19. a value is strongly modulated at a period of half of the light wavelength (λ _0/2) along the envelope gradually decreases with respect to the distance L.

The laser light emitted from the vertical cavity surface emitting laser 19 is, as compared with the ordinary semiconductor laser,
The beam divergence angle is small and the full width at half maximum (FWHM) is 5
It is about deg. However, since the light is not perfectly parallel light, β becomes very small when the distance L increases to several tens of cm, and the contribution from the external mirror 21 to the laser oscillation hardly appears.

Since the vertical cavity surface emitting laser 19 has a smaller l _{eff in the} equation (8) than that of a normal semiconductor laser, α _{m, tot} varies greatly with a slight change in β. Therefore, the laser oscillation is turned on / off, or the laser light output changes extremely.

[0041] Therefore, as shown in FIG. 3 (c), by a distance L of the external mirror 21 is changed, since the light output is modulated at a cycle of lambda _0/2, the change frequency of the light output It is possible to measure the displacement amount (S; see FIG. 1) of the external mirror 21 by counting with the counting device 29 (see FIG. 1) and applying the above equation (1).

An optical displacement sensor according to the first embodiment of the present invention to which such a principle is applied will be described below with reference to FIG. FIG. 4A schematically shows the configuration of a small displacement sensor to which the above principle is applied.

As shown in FIG. 4A, in the small displacement sensor of this embodiment, the vertical cavity surface emitting laser 37 fixed in the housing 35 via the heat sink 33 and the housing 35.
An external mirror 43 mounted to face the vertical cavity surface emitting laser 37 at the lower end of a support rod 41 inserted through a guide hole 39 formed in the inside, and a side of the outside mirror 43 protruding outside the housing 35. An attachment portion 45 configured to attach an object to be measured (not shown) to the upper end portion of the support rod 41 and a light receiving element 47 attached to the main surface side of the external mirror 43 are provided.

The external mirror 43 is attached to the lower end portion of the support rod 41 so that its main surface is orthogonal to the optical axis of the laser light 49, and the support rod 4 is attached via the attachment portion 45.
By moving 1 in the direction of the arrow S in the figure, it is movable in the optical axis direction.

The vertical cavity surface emitting laser 37 includes a casing 3
The base end portion of the laser driving electric wiring 53 inserted through the first through hole 51 formed in 5 is connected,
A tip portion of the electric wiring 53 is electrically connected to a semiconductor laser (LD) driving power source 57 via a laser driving electrode terminal 55.

Therefore, the drive current output from the LD drive power source 57 is supplied to the vertical cavity surface emitting laser 37 through the laser drive electrode terminal 55 and the laser drive electrical wiring 53.

Further, the light receiving element 47 is connected to a base end portion of a light intensity detecting electric wiring 61 inserted through a second through hole 59 formed in the casing 35, and this electric wiring 61 is connected. The tip end of is electrically connected to the current detecting means 65 via the light intensity detecting current terminal 63. A light receiving element power supply 67 is connected to the current detecting means 65, and the detection data output from the current detecting means 65 is configured to be output to the arithmetic device 71 via the counting device 69. There is.

The light receiving element 47 is the same as the light receiving element 47.
In order to suppress the influence of the reflected light from the external mirror 43, it is preferable that the external mirror 43 is bonded to the peripheral portion of the irradiation area of the laser light 49 on the main surface.

FIG. 4B shows an enlarged structure of the vertical cavity surface emitting laser 37. As shown in FIG. 7B, on the N-type semiconductor substrate 73, an N-type semiconductor buffer layer 75, a lower distributed Bragg reflector 77 including a semiconductor multilayer film, an N-type semiconductor clad layer 79, an active layer 81, and P.
An upper distributed Bragg reflector 85 composed of a P-type semiconductor clad layer 83 and a P-type semiconductor multilayer film is laminated. And
Etching is performed to the depth of the N-type semiconductor clad layer 79 leaving the resonator portion, the electrode contact portion of the silicon dioxide film 87 covering the surface is opened, and the upper distributed Bragg reflector 85 and the N-type semiconductor clad layer are opened. P-type and N-type electrodes 89 and 91 are formed at 79, respectively.

In order to suppress the reflection of the laser light 49 from the back surface of the substrate, it is desirable to select a material capable of absorbing the laser light for the N-type semiconductor substrate 73 and the N-type semiconductor buffer layer 75.

The laser light 49 is converted into an electric signal by the light receiving element 47, is input to the counting device 69 via the current detecting means 65, and the number of fluctuations of the light intensity is counted. The counted data is input to the arithmetic unit 71, and is arithmetically operated based on the above-mentioned equation (1).

As a result, the vertical cavity surface emitting laser 37
And the relative displacement amount (ΔL) between the external mirror 43 and the external mirror 43 is calculated. As described above, since the surface emitting laser applied to this embodiment has a small beam emission angle, it is not necessary to dispose another optical system (for example, a lens) between the surface emitting laser and the external mirror. Further, since the surface emitting laser can always maintain a single oscillation mode without being affected by the return light, it is possible to dispose a light shielding optical system such as an optical isolator.
It is possible to suppress fluctuations in optical output and oscillation wavelength due to mode hopping due to return light, which is a problem in general semiconductor lasers.

Therefore, the output change of the laser oscillation light based on the relative displacement of the external mirror and the surface emitting laser can be measured with high accuracy while covering a wide displacement range. As a result, it is possible to provide a compact optical displacement sensor capable of highly accurate displacement measurement with an extremely simple configuration.

Next, an optical displacement sensor according to the second embodiment of the present invention will be described with reference to FIGS. In the description of this embodiment, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 5A, the external mirror 93 applied to this embodiment is a semi-transmissive mirror, and the light receiving element 47 is provided on the rear surface side of the external mirror 93 (on the side opposite to the main surface). ) Is attached to.

In the case of this embodiment, it is not necessary to consider the influence of the reflected light from the light receiving element 47 on the laser light intensity, so that the installation position of the light receiving element 47 can be set arbitrarily.

The shape of the external mirror 93 is formed, for example, by obliquely cutting the upper surface in order to prevent the influence of reflected light from the upper surface (the surface opposite to the main surface) thereof. .

As shown in FIG. 5B, in this embodiment,
A light receiving element 95 formed of a semiconductor substrate is provided instead of the external mirror. As shown in FIG. 7C, the structure of the light receiving element 95 is such that an N-type semiconductor buffer layer 75, a low-concentration light absorption layer 97, and P are formed on an N-type semiconductor substrate 73 on which an N-type electrode 91 is formed. A type contact layer 99 is laminated, an electrode contact portion of the silicon dioxide layer 87 formed on the P type contact layer 99 is opened, and a P type electrode 89 is connected to the P type contact layer 99.

The silicon dioxide layer 87 is a protective film for the portion other than the P-type electrode 89, but also has a function as a means for adjusting the reflectance. For example, when the thickness of the silicon dioxide layer 87 corresponds to 1/2 of the light wavelength, the reflection mirror as a whole has a reflectance similar to that of the semiconductor substrate, or when it corresponds to 1/4 of the light wavelength, the minimum reflectance. It becomes the reflectance.

Further, in order to suppress reflection from the back surface of the light receiving element 95 (that is, the surface not facing the vertical cavity surface emitting laser 37), the N type semiconductor substrate 73 and the N type semiconductor buffer layer 75 are provided. It is preferable that the band gap of the band is smaller than the light energy so as to absorb the laser light.

As shown in FIGS. 6A and 6B, the vertical cavity surface emitting laser 101 in which the light receiving elements are integrated is applied to this embodiment. In the vertical cavity surface emitting laser 101, a surface emitting laser region T is formed in the center thereof, and light receiving regions E for receiving light from the external mirror 43 are formed on both sides thereof. Outside the surface emitting laser
Although the emission angle of the light that goes to the partial mirror is small, the full width at half maximum
Since it has a spread of about 5 deg.
Measuring part of the light reflected by the external mirror
You can

With this structure, the electric wiring 61 extending from the light receiving element 47 provided on the external mirror 43 (see FIG. 4).
And FIG. 5) is not deformed, the degree of freedom in designing the external mirror 43 is improved, and the external mirror 43 is easily made compact.

As shown in FIG. 4B, the vertical cavity surface emitting laser 101 has a semiconductor similar to that shown in FIG.
After the multilayer films are stacked, the contact portion of the N-type electrode 91 is etched from the surface to the N-type semiconductor clad layer 79, and the light receiving region E is etched from the surface to the P-type semiconductor clad layer 83. ing.

Next, an optical displacement sensor according to the third embodiment of the present invention will be described with reference to FIG. In addition,
In the description of this embodiment, the same components as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted.

The present embodiment shows a configuration in which the distance between the external mirror 43 and the vertical cavity surface emitting laser 101 is large. In FIG. 7A, the external mirror 43 is formed in a concave shape so that the laser beam 49 has a converging property and the laser beam is reliably fed back onto the emission end face.

In FIG. 2B, the lens mounting portion 1 is provided between the external mirror 43 and the vertical cavity surface emitting laser 101.
A collimating lens 105 is arranged via 03. In each case, a fixed reference mirror or external
Light to prevent mode hop due to reflected light from the mirror
Unlike the conventional method, it does not require an isolator.
It

In this embodiment, the vertical cavity surface emitting laser 101 in which light receiving elements are integrated is applied.
It is also possible to apply the light receiving element as shown in FIG. 4 and FIG.

Next, an optical displacement sensor according to the fourth embodiment of the present invention will be described with reference to FIG. In addition,
In the description of this embodiment, the same components as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted.

The optical displacement sensor of this embodiment is provided with first and second casings 35a and 35b which are optically connected via the single mode fiber 107. Specifically, in the first and second casings 35a and 35b, respectively,
The first and second collimating lenses 105a and 105b are arranged at positions facing the end of the single mode fiber 107, and laser light is emitted between the vertical cavity surface emitting laser 101 and the external mirror 43. Will be resonated via the first and second collimating lenses 105a and 105b and the single mode fiber 107.

In this case, the displacement detecting portion, that is, the second casing 35b can be further miniaturized. Although the vertical cavity surface emitting laser 101 in which the light receiving elements are integrated is applied in the present embodiment, the light receiving elements as shown in FIGS. 4 and 5 can also be applied.

Next, an optical displacement sensor according to the fifth embodiment of the present invention will be described with reference to FIG. In addition,
In the description of this embodiment, the same components as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the process of assembling the optical displacement sensor, when the semi-transmissive external mirror 93 has a large inclination and a large number of interference fringes are formed on the effective emission surface of the laser light, the output of the light receiving element 47 is output. Are averaged with respect to the phase, which makes it difficult to detect the displacement amount. _Assuming that the effective diameter of the emission end face of the vertical cavity surface emitting laser (not shown) is W _SEL , when the external mirror 93 is tilted by θ , the external mirror
The light reflected once by the laser resonates in the surface emitting laser.
Interfere with the light, conditions that one interference fringe on the laser emission surface, can be expressed as _{W SEL · tan θ = λ 0} /4.

For example, W _SEL = 5 μm, λ ₀ = 0.97 μm
Then, θ = 2.7deg, so the laser emission surface
Considering the multiple reflection between the external mirror and the external mirror, the inclination of the external mirror 93 needs to be maintained so as to be equal to or less than a fraction thereof.

The external mirror 93 applied to this embodiment is
It is adhered to the light receiving element 47 through the piezoelectric elements 109 arranged at the four corners. Electrodes 111 are formed on both sides of each of these piezoelectric elements 109.
By applying a predetermined amount of voltage to the piezoelectric element 1 via the piezoelectric element control terminal 113, the thickness of the element can be controlled to expand and contract.

As a result, the inclination of the external mirror 93 can be adjusted . The actual preparation method is one piezoelectric element 1
After the voltage applied to 09 is varied to maximize the optical output, the other piezoelectric elements 109 are sequentially adjusted in the same manner. By uniformly stretching all piezoelectric elements 109, so that the adjustment if such maximum value of the light is obtained completed for each λ _0/2.

Next, an optical displacement sensor according to the sixth embodiment of the present invention will be described with reference to FIG. In the description of this embodiment, the same components as those in the above-described embodiment will be designated by the same reference numerals and the description thereof will be omitted.

In the present embodiment, the following means for measuring the displacement amount can be applied even when the moving direction of the external mirror 93 changes. The first method for determining the direction of movement of the external mirror 93 is to determine by the magnitude of the peak value of the laser output. That is, as shown in FIG. 3C, when the external mirror 93 moves away from the surface emitting laser, the peak value of the laser output decreases, and when the external mirror 93 approaches, the peak value increases. You can

As a second method for determining the direction of movement of the external mirror 93, FIG. 10 shows a configuration in which a phase shift is introduced into the reflected light from the mirror. In FIG. 10 (a),
The dielectric film 115 is configured to shift the phase of the reflected light by an amount corresponding to the phase 2φ on the main surface of the external mirror 93 (that is, the surface facing the vertical cavity surface emitting laser 37).
Are formed.

When the refractive index of the dielectric is n, the film thickness corresponding to the phase φ is φ · λ / (2π · n).

In FIG. 7B, the external mirror 93 is arranged so as to shift the phase of the reflected light by an amount corresponding to the phase 2φ.
The main surface of is etched. As a result, the light receiving element 47, as shown in FIG. (C), in response to a change in the distance L between the vertical cavity surface emitting laser 37 and the external mirror 93, in a cycle of lambda _0/2 Two sets of light intensity peaks shifted by 2φ in phase are observed.

As described above, by appropriately setting the position and area of the region provided with the phase shift, the relative magnitude of the laser light intensity corresponding to the region provided with the phase shift and the other region is changed. It becomes possible.

When the external mirror 93 moves in a fixed direction, the peak value of the light intensity signal detected by the light receiving element 47 alternately appears as large or small. However, when the moving direction of the external mirror 93 is reversed, it becomes large or small. The peak value appears continuously.

Therefore, when the moving direction of the external mirror 93 is reversed, the positive / negative of the counter numerical value is reversed in the counter 69 (see FIG. 4) to measure the displacement amount including the direction of the external mirror 93. It becomes possible.

Next, an optical displacement sensor according to the seventh embodiment of the present invention will be described with reference to FIG. In the description of this embodiment, the same components as those in the above-described embodiment will be designated by the same reference numerals and the description thereof will be omitted.

The present embodiment is an application example of the sixth embodiment, in which a light receiving element 95 formed of a semiconductor substrate is applied as an external mirror, and the light receiving element 95 and the vertical cavity surface emitting laser are applied. Two sets of 37 and 37 are prepared, and a phase shift is introduced into one of the sets, so that the direction of displacement can be determined.

When the light receiving element 95 moves in a fixed direction, the peak values of the light intensity detected in the light receiving area E of these light receiving elements 95 are alternately detected, but when the moving direction is reversed. In the counting device 69 (see FIG. 4), it is possible to measure the displacement amount including the direction of the light receiving element 95 by reversing the positive and negative of the counter numerical value.

Next, an optical displacement sensor according to the eighth embodiment of the present invention will be described with reference to FIGS. 12 to 16. In the description of this embodiment, the same components as those in the above-described embodiment will be designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, a vertical cavity surface emitting laser 101 in which light receiving elements are integrated is applied, and a pair of elastic bodies 117 are interposed between the surface emitting laser 101 and the external mirror 43. As a result, the pressure sensor is configured as a whole.

Specifically, the vertical cavity surface emitting laser 1
01 is a lower distributed Bragg reflector 77 made of a semiconductor multilayer film, an N type semiconductor clad layer 79, an active layer 81, a P type semiconductor clad layer 83, and a P type semiconductor multilayer film on an N type semiconductor substrate 73. In the state where the Bragg reflector 85 is laminated, these layers are connected to the P-type electrode 89 and the N-type electrode 9
It is sandwiched between 1.

It should be noted that the pair of elastic members 117 are the P-type electrodes 8
9, the external mirror 43 is supported on the vertical cavity surface emitting laser 101. External mirror 43
Since the relationship between the displacement amount and the pressure is proportional in the linear elastic region, the pressure can be calculated by measuring the displacement amount of the external mirror 43.

Here, the external force applied between the external mirror 43 and the vertical cavity surface emitting laser 101 is F (N),
When the contact width of the elastic body 117 with respect to the vertical cavity surface emitting laser 101 is W _G (m), the contact length is L _G , and the thickness is t ₀ , the thickness of the pair of elastic bodies 117 changes by Δt. In this case, there is a relationship of F / 2W _G L _G = EΔt / t ₀ . The Young's modulus of the elastic body 117 is
E (N / m ² ).

According to such a relationship, for example, W _G =
100 μm, L _G = 200 μm t ₀ = 100 μm, and the elastic body 117 is made of rubber (E to
Applying ^{3 × 10 6 N / m 2} ), the minimum resolution of the displacement, λ ₀ /2~0.49μm So, the resolution of the external force F delta
Fmin is ΔFmin = 5.9 × 10 ⁻⁴ (N) = 0.06
It can be estimated as 0 gf.

By appropriately selecting the material applied to the elastic body 117 and defining it to a desired elastic constant, the resolution of the external force can be set in a wide range. Next, a method for manufacturing the above-described pressure sensor (see FIG. 12) will be described with reference to FIGS.

First, as shown in FIG. 13, a lower distributed Bragg reflector 77 made of a semiconductor multilayer film, an N-type semiconductor clad layer 79, an active layer 81, and P are formed on an N-type semiconductor substrate 73.
The upper distributed Bragg reflector 85 including the type semiconductor clad layer 83 and the P type semiconductor multilayer film is laminated by a metal organic vapor phase epitaxial growth method (MOVPE method) or the like.

Next, in order to electrically separate the surface emitting laser region T and the light receiving regions E provided on both sides thereof, as shown in the drawing, a groove reaching the boundary between the active layer 81 and the N-type semiconductor cladding layer 79. Are formed by photoetching.

After that, the upper distributed Bragg reflector 85 remaining on the light receiving region E is removed by etching. 14
As shown in FIG.
Is deposited by a sputtering method or the like, and then a window is opened in the upper end surface of the surface emitting laser region T and the contact region of the light receiving region E by photoetching.

Next, the surface emitting laser region T and the light receiving region E.
After patterning the P-type electrode 89 as the upper electrode of the N-type semiconductor substrate 73 by a lift-off method or the like, the back surface of the N-type semiconductor substrate 73 is polished to deposit the N-type electrode 91, and then heat treatment is performed.

As shown in FIG. 15, next, a pair of elastic bodies 117 are formed. For example, when a material such as polyimide is applied, a laser beam is applied by spin coating and photoetching. The pattern of the pair of elastic bodies 117 is formed so that the cavity portion 119 is formed on the resonance region T and the light receiving region E.

As shown in FIG. 16, for example, a gold-deposited silicon substrate or the like is bonded as an external mirror 43 to the upper portion of the pair of elastic bodies 117 thus formed. It is also possible to apply an ultraviolet curable resin or the like for this adhesion. Further, the pressure sensor as shown in FIG. 12 is completed by performing cleavage of the chip, die bonding, wire bonding and the like.

Next, an optical displacement sensor according to the ninth embodiment of the present invention will be described with reference to FIG. In the description of this embodiment, the same components as those in the above-described embodiment will be designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 17A, in this embodiment, a vertical cavity surface emitting laser 1 having light receiving elements integrated therein is used.
No. 01 is applied, and this surface emitting laser 101 is fixed on a heat sink 33 partitioned by, for example, a red or square type casing 35 arranged around the surface emitting laser 101.

An elastic body 117 is arranged on the heat sink 33 partitioned by the casing 35 so as to surround the surface emitting laser 101, and the external mirror 43 is placed on the elastic body 117. .

Furthermore, on this external mirror 43, the housing 3
5, the piston 121 inserted through the outer mirror 43 is in contact with the piston 121.
It is sandwiched between and.

It is also preferable to fill the inside of the elastic body 117 with an inert gas such as N ₂ or He. Further, the piston 121 is processed with extremely high precision so that it can slide in a fixed direction with respect to the housing 35.

With this configuration, even when the piston 121 receives an external force, the inclination of the external mirror 43 is defined by the processing accuracy of the piston 121 and the casing 35, the width (thickness) of the piston 121, and the like. The parallelism of the external mirror 43 with respect to the surface emitting laser 101 can always be maintained.

FIG. 16B shows a modified example in which the casing 35 has a bottom portion and the pressure sensor having the above-mentioned structure is arranged in the casing 35. Next, an optical displacement sensor according to a tenth embodiment of the present invention will be described with reference to FIG.

In the description of this embodiment, the same components as those in the above-mentioned embodiment will be designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 18A, a vertical cavity surface emitting laser 101 in which light receiving elements are integrated is applied to this embodiment, and the surface emitting laser 101 is fixed on a heat sink 33. There is.

Further, the external mirror 43 and the surface-emitting laser 10
1, a ferroelectric material 123 is interposed between the ferroelectric material 123 and the surface emitting laser 101.
It resonates with the external mirror 43 via 23.

The refractive index of the ferroelectric 123 can be changed according to the magnitude of the external force, and for example, liquid crystal, ferroelectric liquid crystal, ferroelectric substance or the like can be applied.
With such a configuration, for example, a compact pressure sensor can be configured without using the elastic body 117, the piston 121 (see FIG. 17), or the like.

In particular, since PLZT is transparent in the visible light region and has excellent stability, it is possible to form a reliable sensor. FIG. 6B shows a modification in which the transparent conductive film 125 is interposed between the external mirror 43 and the ferroelectric 123, and the extraction electrode 127 is added from the transparent conductive film 125 and the ferroelectric 123. The configuration of such a pressure sensor is shown.

According to this structure, the extraction electrode 127
By applying a predetermined voltage to the ferroelectric body 123 via, it is possible to change the rate of change of the refractive index of the ferroelectric body 123, that is, the sensitivity to pressure.

That is, it is possible to perform offset control, reset control for returning to the initial state, or sensitivity control via the extraction electrode 127. The external mirror 4
It is also possible to reverse the order of 3 and the transparent conductive film 125, or to form the external mirror 43 and the transparent conductive film 125 with the same material.

Next, an optical displacement sensor according to the eleventh embodiment of the present invention will be described with reference to FIG. In the description of this embodiment, the same components as those in the above-described embodiment will be designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 19, a vertical cavity surface emitting laser 101 in which light receiving elements are integrated is applied to this embodiment, and the surface emitting laser 101 is fixed on a heat sink 33. There is.

An elastic variable substance 127 is formed on the heat sink 33 so as to surround the surface emitting laser 101. On the elastic variable substance 127, the transparent conductive film 12 is formed.
An external mirror 43 is provided via 5.

The elastic variable substance 127 is constructed so that the elastic modulus can be changed to a desired value by the voltage applied through the extraction electrode 127. For example, liquid crystal, ferroelectric liquid crystal, ferroelectric substance, etc. Is configured to be applicable.

[0117]

Since the vertical cavity surface emitting laser applied to the present invention has a small beam emission angle, another optical system (for example, a lens) is arranged between the surface emitting laser and the external mirror. No need. Further, since the vertical cavity surface emitting laser can maintain a single oscillation mode at all times without being affected by the returning light, there is a problem with a general semiconductor laser even if a light shielding optical system such as an optical isolator is not arranged. It is possible to suppress the fluctuation of the optical output and the oscillation wavelength due to the mode hopping due to the returning light.

Therefore, it is possible to measure the output change of the laser oscillation light with high accuracy based on the relative displacement between the external reflection means and the vertical cavity surface emitting laser. As a result, it is possible to provide a compact optical displacement sensor capable of highly accurate displacement measurement with an extremely simple configuration.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a principle applied to the present invention.

FIG. 2 is a diagram showing a configuration of a composite resonator for explaining the operation of the principle shown in FIG.

FIG. 3 is a diagram showing the relationship among reflectance, phase conditions, and laser output in the composite resonator shown in FIG.

FIG. 4A is a diagram showing an overall configuration of an optical displacement sensor according to a first embodiment of the present invention, and FIG. 4B is a diagram showing a configuration of a vertical cavity surface emitting laser.

FIG. 5 is a diagram showing a configuration of an optical displacement sensor according to a second embodiment of the present invention, FIG. 5A is a diagram showing a case where a semi-transmissive mirror is applied as an external mirror, and FIG. ) Is
The figure which shows the case where the light receiving element formed of the semiconductor substrate is applied instead of an external mirror, (c) is a figure which shows the structure of the light receiving element shown to (b).

FIG. 6A is a diagram showing a configuration of an optical displacement sensor according to a second embodiment of the present invention, and FIG. 6B is a diagram showing an integrated light receiving element.
The figure which shows the structure of the vertical cavity surface emitting laser.

7A and 7B are diagrams showing a configuration of an optical displacement sensor according to a third embodiment of the present invention, FIG. 7A is a diagram showing a case where a concave external mirror is applied, and FIG. FIG. 6 is a diagram showing a case where a collimator lens is arranged on the optical path between an external mirror and a vertical cavity surface emitting laser.

FIG. 8 is a diagram showing a configuration of an optical displacement sensor according to a fourth embodiment of the present invention.

9A and 9B are views showing a configuration of an optical displacement sensor according to a fifth embodiment of the present invention, FIG. 9A is a sectional view of a portion of an external mirror, and FIG. 9B is a plan view thereof.

FIG. 10 is a diagram showing a configuration of an optical displacement sensor according to a sixth embodiment of the present invention, in which (a) shows a case where a dielectric film for shifting the phase of reflected light is formed. ,
(B) is a diagram showing a case where the main surface of the external mirror is etched so as to shift the phase of reflected light,
FIG. 6C is a diagram showing the relationship between the displacement of the external mirror and the received light intensity.

11A is a diagram showing a configuration of an optical displacement sensor according to a seventh embodiment of the present invention, and FIG. 11B is a diagram showing a relationship between displacement of a light receiving element as an external mirror and light receiving intensity. Fig.

12A is a sectional perspective view showing the configuration of an optical displacement sensor according to an eighth embodiment of the present invention, and FIG. 12B is a diagram showing a relationship between external pressure and received light intensity.

FIG. 13 is a diagram showing a manufacturing process of the sensor shown in FIG. 12;

FIG. 14 is a diagram showing a manufacturing process of the sensor shown in FIG. 12;

FIG. 15 is a diagram showing a manufacturing process of the sensor shown in FIG.

16 is a diagram showing a manufacturing process of the sensor shown in FIG.

17A is a diagram showing a configuration of an optical displacement sensor according to a ninth embodiment of the present invention, and FIG. 17B is a diagram showing a modification thereof.

18A is a diagram showing a configuration of an optical displacement sensor according to a tenth embodiment of the present invention, and FIG. 18B is a diagram showing a modification thereof.

FIG. 19 is a diagram showing a configuration of an optical displacement sensor according to an eleventh embodiment of the present invention.

FIG. 20 is a diagram showing a basic configuration of a Michelson interferometer.

FIG. 21 is a diagram showing a configuration of a conventional optical displacement sensor using a composite resonator structure.

[Explanation of symbols]

19 ... Vertical cavity surface emitting laser, 21 ... External mirror,
23 ... Detecting means, 25 ... Light receiving element, 27 ... PN junction potential difference detecting means, 29 ... Counting device, 31 ... Arithmetic device.

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-4-195778 (JP, A) JP-A-4-120405 (JP, A) JP-A-64-59107 (JP, A) JP-A-5- 152674 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01B 11/00-11/30 G01B 9/02 G01D 5/26 H01S 3/18

Claims (14)

(57) [Claims] 1. A vertical cavity surface emitting laser, and external reflection means which are arranged so as to face the vertical cavity surface emitting laser without an optical system and which are combined with each other to form a compound resonator. Measuring a periodical change in laser output or a periodical change in mirror loss of the compound resonator caused by a relative positional change between the vertical cavity surface emitting laser and the external reflection means. Accordingly, the optical displacement sensor is provided with a detection unit configured to detect a relative positional change between the vertical cavity surface emitting laser and the external reflection unit. 2. The vertical cavity surface emitting laser comprises:
The optical displacement sensor according to claim 1, wherein the external reflection means is directly irradiated with a laser beam without passing through an optical system having a lens effect. 3. The optical displacement sensor according to claim 1, wherein a wavelength interval satisfying a phase condition of a laser resonator of the vertical cavity surface emitting laser is 30 nm or more. 4. The optical displacement sensor according to claim 1, wherein an effective cavity length of the laser cavity of the vertical cavity surface emitting laser is 3.5 μm or less. . 5. The effective cavity length of the laser cavity of the vertical cavity surface emitting laser is l _eff , and the distance between the light beam emitting surface of the vertical cavity surface emitting laser and the external reflection means is _defined as: When L is set, L> 10 × l _eff , The optical displacement sensor according to claim 1 or 2, wherein 6. The wavelength spacing satisfying the phase condition of the laser cavity of the vertical cavity surface emitting laser is 30 nm or more, and the effective cavity length of the laser cavity of the vertical cavity surface emitting laser. _Is L _eff and L is a distance between the light beam emitting surface of the vertical cavity surface emitting laser and the external reflection means, L> 10 × l _eff. 2. The optical displacement sensor according to 2. 7. The external reflection means has at least two reflection regions combined with the vertical cavity surface emitting laser so as to form at least two composite resonators. The optical displacement sensor according to claim 1, wherein at least one of them is provided with an optical phase shift means. 8. The optical phase shift means shifts the phase of a light beam in the composite resonator provided with the optical phase shift means and another composite resonator. Optical displacement sensor. 9. The optical phase shift means is provided on the external reflection means, and the optical phase shift means on the at least two reflection regions have different phase shift amounts. The optical displacement sensor according to claim 7, wherein: 10. The optical phase shift means comprises a dielectric film provided at a location corresponding to at least one reflection area of the at least two reflection areas of the external reflection means. The optical displacement sensor according to claim 7. 11. The optical phase shift means comprises a dielectric film provided at a position corresponding to at least one reflection area of the at least two reflection areas of the external reflection means. The optical displacement sensor according to claim 7. 12. At least two vertical cavity surface emitting lasers, which are formed on the same substrate, are arranged to face the vertical cavity surface emitting lasers without an optical system, and are combined with each other. External reflection means having at least two reflection regions forming at least two composite resonators, and optical phase shift means provided in at least one composite resonator for shifting the phase of a light beam, Periodic changes in two or more laser outputs caused by changes in the relative distance between the vertical cavity surface emitting laser and the reflection surface of the external reflection means, or the periodic mirror loss of the composite resonator. By measuring the change, a detecting means for detecting a change in the relative distance between at least two of the vertical cavity surface emitting lasers and the reflecting surface of the external reflecting means is provided. An optical displacement sensor having. 13. The optical phase shift means shifts the phase of a light beam in the composite resonator provided with the optical phase shift means and another composite resonator. Optical displacement sensor. 14. The optical phase shift means is provided on the external reflection means, and the optical phase shift means provided on the at least two reflection areas have different phase shift amounts, respectively. The optical displacement sensor according to claim 12, wherein: