JP2000346615A - Optical displacement sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a small and lightweight optical displacement sensor having resolution insusceptible of the distance between a light source and a light receiving element by taking out the output independently from a plurality of light receiving areas of a photodetector. SOLUTION: A vertical resonator type surface emission laser 12 is secured to a heat sink 48 while directing the light emitting surface upward and the light receiving surface of a photodiode 32 is secured to the lower surface of a supporting plate 60 while facing the light emitting surface of the surface emission laser 12. The photodiode 32 is connected with a light receiving system power supply 74, and an operating unit 76. An object for measuring relative displacement, i.e., a moving object fixing part 56, is secured with the supporting plate 60 through a supporting rod 58. Furthermore, the photodiode 32 is supported to move on the optical axis of a beam up and down while keeping the light receiving surface perpendicular to the optical axis. A light receiving areas selector connected with a plurality of light receiving areas of the photodiode 32 delivers the output from each area to the operating unit 76. The operating unit 76 calculates the relative distance between the surface emission laser 12 and the photodiode 32 based on the ratio of maximum and minimum outputs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a displacement sensor,
In particular, it relates to an optical displacement sensor using optical means.

[0002]

2. Description of the Related Art Conventionally, as an example of an optical displacement sensor,
A light source and a light receiving element are provided, one of which is fixed to the moving body, and is configured to receive the light emitted from the light source by the light receiving element and detect a change in the light intensity to obtain a displacement of the moving body. Are known.

Such an optical displacement sensor is, for example,
It is disclosed in JP-A-7-270120.

FIG. 5 shows a basic configuration of an optical displacement sensor disclosed in Japanese Patent Application Laid-Open No. 7-270120.

As shown in FIG. 5, this displacement sensor has a surface emitting laser 12 and a photodiode 32.
The surface emitting laser 12 is connected to the housing 50 via the heat sink 48.
Is fixed with the light-emitting surface facing upward.

[0006] An LD drive power supply 62 for supplying a constant current is connected to the surface emitting laser 12 through an electric wiring 64 passing through a through hole 66 provided in the housing 50.

A support rod guide hole 52 is provided on the upper surface of the housing 50.
Is provided.

The support rod 58 passes through the support rod guide hole 52, and at the upper end thereof, a mounting portion 56 for detecting a displacement is fixed, and at the lower end, a support plate 60 is fixed.

The mounting portion 56 is supported by an elastic body 54 provided around the support rod guide hole 52 on the upper surface of the housing 50.

Thus, the support rod 58 and the support plate 60
Are supported so that they can move in the vertical direction in the figure.

The photodiode 3 is provided on the lower surface of the support plate 60.
2 is fixed so that its light receiving surface faces the light emitting surface of the surface emitting laser 12.

When a force acts on the mounting portion 56 in the vertical direction in the figure, the elastic body 54 is deformed in accordance with the force.

As a result, the photodiode 32 moves up and down, and the surface emitting laser 12 and the photodiode 32
Is changed.

The output of the photodiode 32 changes with the change of the distance z.
For example, the distance z between the surface emitting laser 1 and the photodiode 32 can be calculated by using a calibration curve obtained logically or experimentally.

[0015]

However, the above-mentioned displacement sensor has the following problems.

FIG. 3 shows the relationship between the distance z between the surface emitting laser 12 and the photodiode 32 and the output of the photodiode 32.

That is, in FIG. 3, the horizontal axis represents the distance z,
When the ordinate represents the ratio η of light emitted from the light source to the light receiving element, the η-z characteristic curve shows a curve as shown in FIG.

The parameter Wp is the width of the light receiving element, and Wo is the beam waist, which is approximately equal to the width of the emission window of the surface emitting laser.

The resolution as a sensor depends on the gradient of the η-z characteristic curve. A high gradient indicates a high resolution, and a low gradient indicates a low resolution.

FIG. 4 shows a dη / dz-z curve, and the region of z showing high resolution and good resolution is W
It can be seen that p differs greatly depending on p.

That is, when Wo = 2 μm, Wp = 2
In the case of μm, high resolution is shown in the region of z = 150 μm or less, but in the case of Wp = 40 μm, z = 300 μm to 500 μm.
Good resolution is shown in the range of m.

That is, assuming that Wo and Wp are constant, a high-resolution sensor can be manufactured only in a specific range.

Another problem is that, in the displacement sensor having the configuration shown in FIG. 5, when the optical axis of the beam of the surface emitting laser 12 does not coincide with the center of the light receiving area of the photodiode 32. In addition, the output of the photodiode does not match the calibration curve corresponding to FIG. 3, and a measurement error of the distance z occurs.

For this reason, it is necessary to match these two with high accuracy. However, for this purpose, a high level of assembling technique is required, which causes a problem that assembling cost and assembling time increase.

Further, as another problem, many light sources used for sensors are affected by environmental temperature and power supply stability.
It is known that the optical power fluctuates.

The fluctuation of the optical power causes the fluctuation of the optical power incident on the light receiving element. As a result, the output from the light receiving element fluctuates.

Therefore, when the output of the light receiving element changes,
There is a problem that it becomes impossible to distinguish whether the change is due to the fluctuation of the optical power or the change in the displacement z.

The present invention has been made in view of the above circumstances, and has a small number of parts, is easy to assemble, is small and lightweight, and is hardly affected by the distance z between the light source and the light receiving element. It is another object of the present invention to provide an optical displacement sensor having a small measurement error due to fluctuations in the optical power of a light source.

[0029]

According to the present invention, in order to solve the above-mentioned problems, (1) a light source for emitting a predetermined light beam, and a photodetector for receiving the light beam emitted from the light source are provided. In the optical displacement sensor for detecting a change in the optical path length between the light source and the photodetector, the photodetector has a plurality of light receiving regions arranged at predetermined positions, The optical displacement sensor is configured to be able to take out the output independently from the light receiving area of the optical displacement sensor.

According to the present invention, in order to solve the above-mentioned problems, (2) a signal processing means for performing signal processing on an output selected by a predetermined method from each output from the plurality of light receiving areas. The optical displacement sensor according to (1) is further provided.

According to the present invention, in order to solve the above-mentioned problems, (3) a signal processing means for obtaining a ratio between a plurality of outputs selected by a predetermined method from each output from the plurality of light receiving areas. The optical displacement sensor according to (1), further comprising:

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an outline of an optical displacement sensor according to the present invention will be described.

An optical displacement sensor according to the present invention comprises a light source, a photodetector having a plurality of light receiving areas, and means for detecting a change in a relative position of a displacement detection target based on an output from the photodetector. It is characterized by having.

Hereinafter, the principle of the present invention will be described with reference to the drawings.

As shown in FIG. 1, consider a surface emitting laser SEL and a light receiving element PD which are opposed to each other at a distance z.

Here, the light receiving element PD has a width in the y direction Wp.
And is disposed on the central axis of the emission surface of the surface emitting laser SEL.

In the following description, it is assumed that the beam spread of the surface emitting laser SEL in the x direction is designed to be small in advance and is within the light receiving area of the light receiving element.

Considering the case where the surface emitting laser SEL has a refractive index waveguide structure, the laser light is emitted from the surface emitting laser SEL.
Considering the case where the refractive index guide is guided in the waveguide of the above, a plane wave is generated, and therefore, the laser light emitted to the outside can be regarded as a Gaussian beam having a beam waist Wo on the emission surface of the laser in the y-axis direction. .

The beam diameter W (z) of the Gaussian beam at a point at a distance z from the exit surface is defined as W (z) defined as the width (from the main axis) at which the intensity of the laser beam becomes 1 / e ² . It is expressed by the following equation using the wavelength λ of the laser light.

[0040]

(Equation 1)

FIG. 2 shows the result of trial calculation of the relationship between the distance z and the beam diameter W (z) using Wo as a parameter by using the equation (1).

Since the beam waist Wo of the surface emitting laser is approximately equal to the size of the emission surface of the laser, the beam spread of the laser light can be designed over a wide range by changing the width of the emission surface of the surface emitting laser as shown in FIG. I understand.

Further, by applying the result of FIG. 2 to a two-dimensional light beam diameter design, (x,
It can be seen that the spread of the laser beam about the y) axis can be designed independently.

On the other hand, it is known that the beam spread cannot be designed by such a method in a usual stripe type semiconductor laser (LD) or semiconductor light emitting device (LED) due to the structure of the device.

In FIG. 1, the distance from the principal axis of the circular Gaussian beam is r, and the real part of the electric field excluding the time and phase terms is E.
Assuming that (r, z), E (r, z) is represented by the following equation.

[0046]

(Equation 2)

Accordingly, the light emitted from the surface emitting laser SEL was emitted.
The ratio of light entering the light receiving element PD η (to the output of the light receiving element
Is proportional to the reflectance from the light receiving element._PD, Error function
To E _rfIs represented by the following equation.

[0048]

(Equation 3)

Here, FIG. 3 shows the result of calculating η for the distance z with R _PD = 0, Wo constant, and Wp as a parameter.

It can be seen from FIG. 3 that the above-mentioned η-z characteristic curve changes when Wp is changed.

Here, the reason why R _PD = 0 is set in consideration of preventing return light to the laser section from causing a change in laser output. For example, the light receiving element PD facing the surface emitting laser SEL is used. This is realized by forming a non-reflective film on the surface of the.

FIG. 4 shows an index of the sensitivity of the displacement sensor.
The relation between dη / dz and the displacement z is shown.

If the total SN ratio including the detection circuit of the light receiving element PD is 30 dB, a fluctuation of the optical output of 0.1% can be detected. Therefore, if the required displacement resolution is 1 μm, the light receiving Change rate dη of output of element PD
/ Dz needs to satisfy the following condition: dη / dz> 0.1% / μm.

As shown in FIG. 4, dη / dz depends on the displacement z and the width Wp of the light receiving element PD. Therefore, if the size of the light receiving area is appropriately adjusted according to the displacement z, the high resolution area can be widened. You can see that it can be done.

Here, the same effect can be obtained by the following method without changing the width Wp of the light receiving area.

That is, a plurality of light receiving areas are arranged as a photodetector, and the output ratio between the light receiving area having the strongest incident light and the light receiving area arranged at a predetermined distance d from the light receiving area is determined. By changing according to the amount z, it is possible to widen the high-resolution region.

As another problem, FIG.
As shown in (b), the light source for the sensor has a problem that the optical power changes under the influence of a change in the environmental temperature or the like.
The ratio of the optical power at a point at a distance d from the optical axis is constant.

Therefore, by taking the ratio of the outputs from the two appropriate light receiving elements at a distance d, an optical displacement sensor that is not affected by fluctuations in the optical power can be manufactured.

Further, the problem of adjusting the optical axes of the light source and the photodetector can be solved as follows.

That is, as shown in FIG. 7, a light receiving element 3 in which a plurality of light receiving areas 33 are arranged in parallel at equal intervals.
Consider 2.

Here, 110 is a beam spot on the light receiving element 32, and 77 is a light receiving area selecting device.

When the light from the light source enters the light receiving element 32, the light axis of the light source exists on the light receiving area 100 where the output is the largest, and the ratio of the output to the light receiving area 102 separated by a predetermined distance d is obtained. , The displacement z can be accurately measured.

That is, a displacement sensor capable of accurately measuring a displacement amount without aligning the optical axis can be manufactured.

When a surface emitting laser is used as a light source,
By changing the size of the emission surface of the surface emitting laser, the beam spread of the laser light can be appropriately designed.
By appropriately designing the size of the emission window of the laser for the (x, y) axes perpendicular to each other, the spread of the laser beam can be independently designed for the (x, y) axes.

Therefore, in the conventional light source, as shown in FIG. 8A, when the distance z between the light source and the photodetector changes, the beam spot on the photodetector also changes in the x and y axes. The light receiving area 33 cannot be used effectively.

However, as shown in FIG. 8B, when a surface emitting laser is used as the light source, the spread of the beam is reduced in the x-axis direction and is adjusted to an appropriate size in the y-axis direction. The beam spot shape on the area 33 can be appropriately designed.

That is, the light receiving area 33 can be effectively used over a wide range of the distance z.

Next, an embodiment of the present invention based on the above outline will be described with reference to the drawings.

(First Embodiment) A first embodiment of the present invention will be described with reference to FIGS.

FIG. 9 is a diagram showing the configuration of the optical displacement sensor according to the first embodiment of the present invention.

As shown in FIG. 9, the vertical cavity surface emitting laser 12 is fixed on a heat sink 48 with its light emitting surface facing upward.

An LD drive power supply 62 for supplying a constant current to the surface emitting laser 12 via an electric wiring 64 is connected to the surface emitting laser 12.

On the other hand, the photodiode 32 has its light receiving surface facing the light emitting surface of the surface emitting laser 12.
It is fixed to the lower surface of the support plate 60.

A power supply 74 of a light receiving system and an arithmetic unit 76 for calculating a relative distance z between the photodiode 32 and the surface emitting laser 12 from the output of each light receiving area are connected to the photodiode 32 via an electric wiring 70. Have been.

The mounting portion 56 of the moving object whose relative displacement is to be measured is fixed to a support plate 60 via a support rod 58, and the photodiode 32 is
2 is supported so as to be able to move up and down on the optical axis of the beam while keeping its light-receiving surface substantially perpendicular to the optical axis of the beam emitted from the beam 2.

FIG. 10 is a diagram showing a surface of the photodiode 32 facing the surface emitting laser.

The photodiode 32 is provided with a plurality of light receiving areas 33, and these light receiving areas 33 are arranged at equal intervals in parallel with each other.

The light receiving area 33 is connected to a light receiving area selecting device 77.
Can be output to the arithmetic unit 76 independently.

Some examples of a method of selecting a light receiving area to be used from each light receiving area 33 will be described with reference to FIG.

First, the light receiving area 100 having the largest output
Select

Next, a method of selecting a light receiving area 102 in which another light receiving area has a certain output, for example, the smallest output exceeding 1 / e ² , or a photo depending on the measurement distance z. A method of calculating the beam diameter on the diode 32 and selecting the light receiving area 100 having the largest output and the light receiving area 102 separated by an optimum distance d from the light receiving area 100, and selecting a light receiving element from the distance z, for example, 4 can be determined logically or experimentally with reference to the graph corresponding to FIG. 4 and can be programmed.

From these outputs, the arithmetic unit 76 calculates the ratio of the outputs of the light receiving area 100 and the light receiving area 102,
Relative distance z between surface emitting laser 12 and photodiode 32
Is calculated from the calibration curve corresponding to FIG.

The light receiving area selecting device 77 continuously outputs the outputs from all the light receiving areas 33 to the arithmetic device 76, and the arithmetic device 76 outputs the light receiving area 10 having the largest output.
The ratio of 0 to the output of all the light receiving areas sandwiched between the light receiving area 100 and the light receiving area 102 selected by any of the above methods is calculated, and the ratio is determined from the plurality of calculation results by the relative distance Z. The optimum ratio between the two light receiving areas is extracted, and the relative distance z can be calculated from the calibration curve corresponding to FIG.

The surface emitting laser 12 has various structures. FIG. 11 shows an example of the structure.

In the surface emitting laser shown in FIG. 11, an n-type semiconductor buffer layer 16, an n-type semiconductor multilayer mirror 18, an n-type semiconductor clad layer 20, an active layer 2
2, p-type semiconductor cladding layer 24, p-type semiconductor multilayer mirror
26, and the n-type semiconductor cladding layer 2
0, and the p-type semiconductor multilayer mirror layer 26 and the n-type
The configuration is such that a mold electrode 28 and an n-type electrode 30 are provided.

The photodiode 32 for monitoring the intensity of the laser beam has, for example, a structure in which an n-type layer 36 is laminated on an n + -type semiconductor substrate 34 as shown in the sectional structure of FIG. A p-type region 38 is formed by ion implantation or the like, an antireflection film 40 is laminated on the surface thereof, and after patterning, a p-type electrode 42 is formed, and an n-type electrode 46 is laminated on the n + type semiconductor substrate 34. It has a configuration.

According to the displacement sensor having the above-described configuration, the distance z can be accurately measured without adjusting the optical axis of the light emitted from the surface emitting laser 12 and the central axis of the photodiode 32 to be coincident.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIG.

In FIG. 13, the same members as those described in the first embodiment are denoted by the same reference numerals.

For details of these members, reference is made to the description of the first embodiment, and the following description focuses on differences from the first embodiment.

As shown in FIG. 13, the surface emitting laser 12 is fixed at a position opposite to the light receiving area 33 on the photodiode 32 via a heat sink 48.

As shown in FIG. 10, the photodiode 32 has a plurality of light receiving areas 33 and a light receiving area selecting device 7.
7 are provided, and the light receiving areas 33 are arranged at equal intervals in parallel with each other.

The photodiode 32 is fixed to a spacer 82 having a slope with an angle θ by an adhesive layer 80.

The lower surface of the support plate 60 is mirror-finished, and the light emitted from the surface emitting laser 12 is reflected by the lower surface of the support plate 60 and enters the photodiode 32.

When a force acts in the vertical direction in the figure on the mounting portion 56 for attaching the moving object whose relative displacement is to be detected, the support plate 60 moves in the vertical direction according to the magnitude of the force.

For this reason, the surface emitting laser 12 is
The distance z on the optical axis to the lower surface of 0 changes, and the intensity of light incident on the photodiode 32 changes.

Each light receiving area 3 on the photodiode 32
According to the output of 3, the light receiving area selection device 77 selects the light receiving areas to be used, and outputs the ratio of the outputs of those light receiving areas to the arithmetic unit 76.

The arithmetic unit 76 calculates the distance z between the surface emitting laser 12 and the photodiode 32 using a calibration curve corresponding to FIG. 3 obtained logically or experimentally.
Is obtained by calculation.

According to the displacement sensor having the above configuration, even if the positional relationship between the optical axis of the light emitted from the surface emitting laser 12, the center axis of the photo-tiode 32, and the lower surface of the support plate does not match the design value, the distance is not changed. z can be measured accurately.

(Third Embodiment) A third embodiment of the present invention will be described with reference to FIGS. 9 and 14A and 14B.

In FIG. 14, the same members as those described in the first embodiment are denoted by the same reference numerals.

For details of these members, reference is made to the first embodiment, and the following description will focus on differences from the first embodiment.

The overall configuration is as shown in FIG. 9, and the positional relationship between the surface emitting laser 12 and the light receiving area 33 of the photodiode 32 is arranged as shown in FIG. I have.

As shown in FIG. 14 (b), the beam spread of the surface emitting laser 12 is designed to be small in the x direction and large in the y direction. Are arranged in parallel at equal intervals.

The beam emitted from the surface emitting laser 12 forms a beam spot 110 on the photodiode 32.

As shown in FIG. 8B, the size of the beam spot 110 greatly changes in the y direction depending on the relative distance z between the surface emitting laser 12 and the photodiode 32. , In the x direction.

Therefore, since the width of the light receiving area can be effectively used, even if the relative distance z changes over a wide range, the displacement can be measured efficiently.

Further, since it is not necessary to increase the light receiving area, that is, the width of the photodiode 32 in the x direction more than necessary, the size of the photodiode 32 can be reduced.

Therefore, according to the third embodiment,
Distance z between surface emitting laser 12 and photodiode 32
Can be configured over a wide range with high accuracy.

(Fourth Embodiment) A fourth embodiment of the present invention will be described with reference to FIGS.

In FIG. 15, members equivalent to those described in the first embodiment are denoted by the same reference numerals.

For details of these members, reference is made to the first embodiment, and the following description will focus on differences from the first embodiment.

The overall configuration is as shown in FIG. 9, and the positional relationship between the surface emitting laser 12 and the light receiving area 33 of the photodiode 32 is arranged as shown in FIG.

As a light source, a surface emitting laser 12 having a plurality of emission windows is arranged, and an LD selecting device 63 is arranged between the surface emitting laser 12 and an LD driving power supply 62.

The light receiving area 33 of the photodiode 32 is formed sufficiently long in the direction in which the plurality of surface emitting lasers 12 are aligned.

In the present embodiment, the three surface emitting lasers 12 are not used by simultaneously emitting light, but three spots 110 are drawn on the photodiode 32 for convenience.

The measurement procedure is as follows.

First, the LD selecting device 63 selects the surface emitting laser 12 having the smallest emission window, that is, the one having the largest beam spread.

Next, the arithmetic unit 76 tentatively calculates the distance z between the surface emitting laser 12 and the photodiode 32 using a calibration curve corresponding to FIG. 3 obtained logically or experimentally. The provisionally obtained distance z is output to the LD selecting device 63.

The LD selecting device 63 selects the surface emitting laser 12 having the optimum emission window from the relationship between the distance z and the resolution corresponding to FIG. 4 obtained logically or experimentally, for example.

Then, the selected surface emitting laser 12
The measurement is performed again using
The distance z between the surface emitting laser 12 and the photo diode 32 is calculated in detail by using a calibration curve corresponding to FIG. 3 obtained logically or experimentally.

Since these series of measurements are performed continuously, it is not necessary to always perform the provisional measurement of the distance z as described above, and the selecting device 63 performs the measurement based on the value of z measured immediately before. The light receiving area 33 can be selected.

Therefore, according to the fourth embodiment,
Distance z between surface emitting laser 12 and photo diode 32
Can be configured as a displacement sensor capable of measuring a wide range with high resolution.

(Fifth Embodiment) A fifth embodiment of the present invention will be described with reference to FIG. 9 and FIGS.

In FIGS. 16 to 18, members equivalent to those described in the first embodiment are denoted by the same reference numerals.

For details of these members, reference is made to the first embodiment, and the following description will focus on differences from the first embodiment.

The overall configuration is as shown in FIG. 9, and the light emitting surface of the surface emitting laser 12 and the light receiving surface of the photodiode 32 are arranged as shown in FIG. .

The light receiving areas 33 of the photodiode 32 are arranged in a matrix as shown in FIG.

For this photodiode 32, two sets of light receiving areas 33 on a straight line to be used are selected based on the output of each light receiving area 33, and the ratio of the output of the selected light receiving area is calculated and output. The selection device 77 is connected to an arithmetic device 76 for calculating the distance z between the surface emitting laser 12-and the photodiode 32 based on the output of the light receiving area selection device 77.

The size of the exit window of the surface emitting laser 12 is determined by the value of x. It is different in the y direction, wider in the x direction and narrower in the y direction.

Surface emitting laser 12 and photodiode 32
FIG. 17 shows a method for measuring the distance z of FIG.
This will be described with reference to FIG.

The area selecting device 77 first selects one or a plurality of appropriate light receiving areas 33 and outputs the output to the arithmetic unit 76.

Based on this output, the arithmetic unit 76 calculates a provisional distance z.

On the basis of the distance z, the area selecting device 7
7 shows light receiving areas 100 and 102 on a straight line in the y direction as shown in FIG. 17 when z is small, and light receiving areas 1 and 2 on a straight line in the x direction as shown in FIG. 18 when z is large.
00 and 104 are selected.

The light receiving areas 3 arranged on the two sets of straight lines
According to the output from 3, the arithmetic unit 76 calculates the distance z between the surface emitting laser 12 and the photodiode 32 in detail by using a calibration curve corresponding to FIG. 3 obtained logically or experimentally, for example.

A case in which the distance z changes will be described with reference to FIGS.

First, at the distance z, the light receiving area 10
It is assumed that 0 and 102 have been selected.

As the distance z changes in the direction of decreasing, the area selecting device 77 eventually selects 100 and 102a as an optimal set of light receiving areas.

As the distance z further decreases, the area selecting device 77 selects the light receiving areas 100 and 102b as an optimal set of light receiving areas.

Conversely, when the distance z increases, the light receiving areas to be selected are changed in the reverse order, and finally 100 and 102c are selected.

When the distance z is further increased, the light receiving areas 100 and 104a shown in FIG. 18 in which the selected light receiving areas are arranged in the x direction are selected.

In FIGS. 17 and 18, the light receiving areas 100, 102, 104, etc. do not indicate one light receiving area, but a set of light receiving areas in a line on a straight line in the vertical (Y) or horizontal (X) direction. Pointing to.

In this method, by designing the beam spread of the surface emitting laser 12 independently in the x and y directions, a function equivalent to using two surface emitting lasers 12 can be provided.

In this embodiment, the unit light receiving area 3
Although 3 is a square, a rectangular shape is also effective depending on the beam spread angle of the surface emitting laser 12.

Therefore, according to the fifth embodiment,
A displacement sensor capable of measuring the distance z between the surface emitting laser 12 and the photo diode 32 with high resolution over a wide range can be configured.

In each of the above embodiments of the present invention, one or more of the LD drive power supply 62, LD selection device 63, light receiving power supply 74, arithmetic device 76, area selection device 77, etc. It is possible to integrate them on or on a photodiode chip.

The surface emitting laser 12 and the photodiode 32 can be formed on the same chip.

The third to fifth embodiments will be described with reference to FIG. 9 when the light emitting surface of the surface emitting laser 12 and the light receiving surface of the photodiode 32 face each other. However, the same effect can be obtained in the case of the reflection type as shown in FIG.

The present invention can be variously modified or modified without departing from the scope of the invention, and the above-described embodiments are merely examples.

The present specification described in the above embodiments includes the inventions described in the following supplementary notes 1 to 28 in addition to the claims 1 to 3 described in the claims. ing.

(Appendix 1) The optical character displacement sensor according to claim 1 or 2, wherein the signal processing means changes an output to be selected according to the optical path length.

(Supplementary note 2) The signal processing circuit according to claim 2 or claim 1, wherein in determining the ratio between a plurality of outputs, one of the signals selects an output from a light receiving region having the largest amount of received light. An optical displacement sensor according to claim 1.

(Supplementary Note 3) The plurality of light-receiving regions of the photodetector are arranged in a matrix at predetermined intervals.
The optical displacement sensor according to any one of the above.

(Supplementary Note 4) The light beam from the light source is
The length of the short axis and the long axis are different in the plane perpendicular to the optical axis,
3. The optical character type according to claim 1, wherein the plurality of light receiving areas of the photodetector are arranged at predetermined intervals in the direction of the long axis. Displacement sensor.

(Supplementary Note 5) The optical displacement sensor according to any one of Claims 1 to 3 or Claims 1 to 3, wherein the light source is a surface emitting laser.

(Supplementary Note 6) The optical path length is changed by relatively displacing the positions of the light source and the photodetector, according to any one of Claims 1 to 3 or Supplementary notes 1 to 5. Optical displacement sensor.

(Supplementary Note 7) The light source further includes a reflecting member that reflects the light beam emitted from the light source toward the photodetector, and the positions of the light source and the photodetector are relatively fixed. 4. The optical path length changes when the position of the reflection member is displaced.
Alternatively, the optical displacement sensor according to any one of supplementary notes 1 to 5.

(Supplementary Note 8) Light emitting means comprising a plurality of light sources for emitting light beams having different thicknesses from each other, and light receiving means comprising a photodetector for receiving the light beams emitted from the plurality of light sources are provided. An optical displacement sensor that detects a change in an optical path length between the light emitting unit and the light receiving unit,
An optical displacement sensor further comprising light source selection means for selecting a light source used for detecting the change in the optical path length under predetermined conditions.

(Supplementary Note 9) A light source that emits a predetermined light beam, and a photodetector that is disposed near the optical axis of the light beam and that has a light receiving surface that is substantially perpendicular to the optical axis, the light source includes: A displacement sensor configured to change a relative distance between the light source and the photodetector while keeping a direction of the photodetector substantially constant, and to detect a change in the relative distance based on an output from the photodetector; 3. The optical displacement sensor according to claim 1, wherein a plurality of light receiving areas of the light detector are formed at predetermined intervals, and the light detector can independently output respective outputs from the plurality of light receiving areas.

(Function and Effect) By forming a plurality of light receiving areas of the photodetector at predetermined intervals and enabling each output from the plurality of light receiving areas to be output independently, a plurality of light receiving areas of the photodetector can be obtained. Since the output of the light receiving area can be detected independently, the optical axis of the light source can be detected from the light receiving area having the strongest output, so that the optical axis of the light source and the central axis of the light receiving area do not need to be strictly aligned.

The ratio between the light receiving area and each output from the light receiving area at a predetermined distance from the light receiving area is determined, so that the relative position between the light source and the photodetector is not affected by the fluctuation of the light power of the light source. A change in distance can be detected.

Therefore, by selecting a predetermined distance between the light receiving areas according to the relative distance between the light source and the photodetector, a displacement sensor capable of detecting displacement with high sensitivity over a wide measurement range can be manufactured.

In the case of this configuration, it is desirable that the light receiving surface of the photodetector and the optical axis of the light source are nearly perpendicular.

The details of this configuration have been described in the first embodiment.

(Supplementary Note 10) In the supplementary note 9, only the specific output may be selected and output according to the relative distance among the independent signal outputs from the plurality of light receiving areas in the photodetector. An optical displacement sensor comprising a signal line selection circuit capable of performing the above-described operation.

(Function and Effect) Since an output from a specific light receiving area can be selected and output according to the relative distance, an optimum light receiving area can be selected according to the displacement to be measured, and an optical system capable of performing high-resolution measurement over a wide range. A displacement sensor can be manufactured.

The details of this configuration are described in the first embodiment.

(Supplementary Note 11) The optical displacement sensor according to supplementary note 9, wherein the photodetector has a signal processing circuit that outputs a ratio of an output of a specific light receiving element among the plurality of light receiving elements.

(Function / Effect) Since a signal processing circuit for outputting the ratio of the output of a specific light receiving element is provided, even if the optical power of the light source fluctuates for some reason, an optical value which does not include an error in the measured value of the displacement amount. A displacement sensor can be manufactured.

The details of this configuration are described in the first embodiment.

(Supplementary Note 12) In Supplementary Note 11, only the output signals from a specific set of light receiving areas among the output signals from the plurality of light receiving areas are selected according to the relative distance, and are selected by the signal processing circuit. An optical displacement sensor having a signal line selection circuit capable of outputting.

(Effect) The width of the light receiving area is changed by selecting only output signals from a specific set of light receiving areas according to the relative distance and calculating and outputting the ratio by the signal circuit. The same effect as the above can be obtained.

That is, an optical displacement sensor having high resolution over a wide measurement range can be manufactured.

The details of this configuration are described in the first embodiment.

(Supplementary Note 13) In Supplementary Note 12, one of the signals from the pair of light receiving areas output from the signal line selecting circuit to the signal processing circuit by the signal line selecting circuit selects one of the output signals from the light receiving area having the strongest output. An optical displacement sensor characterized by being able to.

(Function and Effect) Since the light receiving area having the strongest output can be selected, the position of the optical axis of the light source can be detected.

Accordingly, it is possible to manufacture an optical displacement sensor capable of performing high-resolution measurement without having to strictly align the optical axis of the light source with the central axis of the light receiving element when assembling the sensor.

The details of this configuration are described in the first embodiment.

(Supplementary Note 14) In the supplementary note 13, the signal line selection circuit may select a signal line from the other light receiving area to be output to the signal processing circuit according to the relative distance. Optical displacement sensor.

(Operation and Effect) Since the ratio of the output of the light receiving area on the optical axis to the output of another light receiving area separated by the distance calculated by the relative distance can be output, the calibration curve corresponding to FIG. An optical displacement sensor capable of performing higher-resolution measurement over a wide measurement range can be manufactured.

The details of this configuration are described in the first embodiment.

(Supplementary Note 15) In Supplementary Note 9, the light receiving areas are formed in a matrix at regular intervals on the light receiving surface, and an output from a specific light receiving area is selected and output according to the relative distance. An optical displacement sensor comprising a signal line selection circuit capable of performing the above-described operation.

(Function and Effect) The distribution of the light intensity on the light receiving element is evaluated two-dimensionally, and the light receiving area on the optical axis and the output from a specific light receiving area separated by an optimum distance according to the relative distance are evaluated. By outputting the ratio, an optical displacement sensor capable of performing high-resolution measurement over a wide range can be manufactured.

The details of this configuration are described in the fifth embodiment.

(Supplementary Note 16) In the supplementary note 9, the light source may be formed so as to have a beam spread having a short axis and a long axis in a specific direction in a plane perpendicular to the optical axis, and a light receiving area of the photodetector. The optical displacement sensors are arranged at predetermined intervals in the direction of the major axis of the beam spread.

(Effect) By arranging the light receiving areas at predetermined intervals in the major axis direction of the spread of the beam, it is possible to use a photodetector having a narrow width in the minor axis direction of the beam. Can be used efficiently, and the outer shape of the sensor can be reduced in size.

The details of this configuration are described in the third embodiment.

(Supplementary Note 17) The optical displacement sensor according to supplementary note 9, wherein the light source that emits the predetermined light beam is a surface emitting laser.

(Function and Effect) By using a surface emitting laser as the light source, the beam divergence angle can be designed independently and inexpensively in the x-axis and y-axis directions. can do.

Therefore, since the photodetector can be narrow in the short axis direction of the beam, the power of the beam can be used efficiently and the outer shape of the sensor can be reduced.

The details of this configuration are described in the first,
This is described in the third to fifth embodiments.

(Supplementary Note 18) The light source includes a light source that emits a predetermined light beam, and a reflection surface that is disposed on an optical axis of the light beam and that is disposed to have a predetermined angle with respect to the optical axis. A mirror that reflects the light beam, and a light detector having a light receiving surface arranged to have a predetermined angle with respect to the optical axis of the reflected light beam, the light source and the light detector and The relative distance between the light source or the photodetector and the mirror is configured to be variable while keeping the orientation of the mirror substantially constant, and the relative distance between the light source and the photodetector and the mirror is changed. A plurality of light receiving areas of the light detector are formed at predetermined intervals, and the light detector can independently output each output from the plurality of light receiving areas. It is characterized by Optical displacement sensor.

(Function and Effect) By forming a plurality of light receiving areas of the photodetector at predetermined intervals and enabling each output from the plurality of light receiving areas to be output independently, a plurality of light receiving areas of the photodetector can be output. Since the output of the light receiving area can be detected independently, the optical axis of the light source can be detected from the light receiving area having the strongest output, so that the optical axis of the light source and the central axis of the light receiving area do not need to be strictly aligned.

By calculating the ratio between the light receiving area and the output of the light receiving area separated by a predetermined distance, the change in the relative distance between the light source and the photodetector can be detected without being affected by the fluctuation of the light power of the light source. can do.

Therefore, by selecting a predetermined distance between the light receiving areas according to the relative distance between the light source and the photodetector, a displacement sensor capable of detecting displacement with high sensitivity over a wide measurement range can be manufactured.

In the case of this configuration, the light receiving surface of the photodetector and the optical axis of the light source are arranged at a predetermined angle, and it is desirable that both move relatively while maintaining this angle.

The details of this configuration are described in the second embodiment.

(Supplementary note 19) In Supplementary note 18, out of the independent signal outputs from the plurality of light receiving areas in the photodetector, only a specific output may be selected and output according to the relative distance. An optical displacement sensor comprising a signal line selection circuit capable of performing the following.

(Function and Effect) Since the output from a specific light receiving area can be selected and output based on the relative distance, an optimum light receiving area can be selected according to the displacement to be measured, and an optical element capable of performing high-resolution measurement over a wide range. A displacement sensor can be manufactured.

The details of this configuration are described in the second embodiment.

(Supplementary Note 20) The optical displacement sensor according to supplementary note 18, wherein the photodetector has a signal processing circuit that outputs a ratio of an output of a specific light receiving element among the plurality of light receiving elements.

(Function / Effect) Since the signal processing circuit for outputting the ratio of the output of the specific light receiving element is provided, even if the optical power of the light source fluctuates for some reason, the measured value of the displacement does not include an error. A displacement sensor can be manufactured.

The details of this configuration are described in the second embodiment.

(Supplementary note 21) In Supplementary note 20, according to the relative distance, only output signals from a specific set of light receiving areas among the output signals from the plurality of light receiving areas are selected and sent to the signal processing circuit. An optical displacement sensor having a signal line selection circuit capable of outputting.

(Function and Effect) According to the relative distance, only the output signals from a specific set of light receiving areas are selected, and the ratio between them is calculated and output by the signal processing circuit. It is possible to obtain the same effect as changing.

That is, a high-resolution optical displacement sensor can be manufactured over a wide measurement range.

The details of this configuration have been described in the second embodiment.

(Supplementary Note 22) In Supplementary Note 21, one of the signals from the pair of light receiving areas output from the signal processing circuit to the signal processing circuit by the signal line selection circuit selects one of the output signals from the light receiving area having the strongest output. An optical displacement sensor characterized by being able to.

(Function and Effect) Since the light receiving area having the strongest output can be selected, the position of the optical axis of the light source can be detected.

Accordingly, it is possible to manufacture an optical displacement sensor capable of performing high-resolution measurement without having to strictly align the optical axis of the light source with the central axis of the light receiving element when assembling the sensor.

[0211] Details of this configuration are described in the second embodiment.

(Supplementary note 23) In Supplementary note 22, the signal line selection circuit can select a signal line from the other light receiving area to be output to the signal processing circuit according to the relative distance. Optical displacement sensor.

(Function and Effect) Since the ratio of the output of the light receiving area on the optical axis to the output of another light receiving area separated by the distance calculated by the relative distance can be output, the calibration curve corresponding to FIG. An optical displacement sensor capable of performing higher-resolution measurement over a wide measurement range can be manufactured.

[0214] Details of this configuration are described in the second embodiment.

(Supplementary Note 24) In Supplementary Note 18, the light receiving areas are formed in a matrix at regular intervals on the light receiving surface, and an output from a specific light receiving area is selected and output according to the relative distance. An optical displacement sensor comprising a signal line selection circuit capable of performing the above-described operation.

(Function and Effect) The distribution of the light intensity on the light receiving element is evaluated two-dimensionally, and the light receiving area on the optical axis and the output of the light receiving area from the specific light receiving area separated by the optimum distance according to the relative distance are evaluated. By outputting the ratio, an optical displacement sensor capable of performing high-resolution measurement over a wide range can be manufactured.

The details of this configuration are described in the fifth embodiment.

(Supplementary note 25) In Supplementary note 18, the light source is formed so as to have a beam spread having a short axis and a long axis in a specific direction in a plane perpendicular to the optical axis, and a light receiving area of the photodetector. Are arranged at predetermined intervals in the direction of the long axis of the beam spread.

(Effect) By arranging the light receiving areas at predetermined intervals in the major axis direction of the spread of the beam, it is possible to use a photodetector having a narrow width in the minor axis direction of the beam. Can be used efficiently, and the outer shape of the sensor can be reduced in size.

The details of this configuration are described in the third embodiment.

(Supplementary note 26) The optical displacement sensor according to supplementary note 18, wherein the light source that emits the predetermined light beam is a surface emitting laser.

(Function and Effect) By using a surface emitting laser as the light source, the beam divergence angle can be designed independently and inexpensively and easily in the x-axis and y-axis directions. can do.

Accordingly, since the photodetector can be narrow in the short-axis direction of the beam, the power of the beam can be used efficiently and the outer shape of the sensor can be reduced.

The details of this configuration are described in the second to fifth embodiments.

(Supplementary Note 27) The optical displacement sensor according to supplementary note 17, wherein the light source is a plurality of surface emitting lasers having different beam divergence angles.

(Effects) By setting the light source to a surface emitting laser having different beam divergence angles, the measurement range of the distance z can be increased even if the interval between the plurality of light receiving areas of the photodetector is constant. can do.

The details of this configuration are described in the fourth embodiment.

(Supplementary note 28) The optical displacement sensor according to supplementary note 27, wherein the light source is a plurality of surface emitting lasers having different beam divergence angles.

(Function / Effect) By setting the light source to a surface emitting laser having different beam divergence angles, the measurement range of the distance z can be increased even if the interval between the plurality of light receiving areas of the photodetector is constant. can do.

The details of this configuration are described in the fourth embodiment.

[0231]

Therefore, as described above, according to the present invention, the number of parts is small, the assembling is easy, the device is small and light, and the resolution is affected by the distance z between the light source and the light receiving element. It is possible to provide an optical displacement sensor that is hard to measure and has a small measurement error due to fluctuations in the optical power of the light source.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of an optical displacement sensor according to the present invention.

FIG. 2 is a diagram showing a beam waist W using equation (1);
FIG. 9 is a diagram illustrating a result of trial calculation of a relationship between a distance z and a beam diameter W (z) using o as a parameter.

FIG. 3 is a diagram illustrating a relationship between a distance z between the surface emitting laser 12 and the photodiode 32 and an output of the photodiode 32;

FIG. 4 is a change rate dη / d of the output of the light receiving element PD;
FIG. 4 is a diagram illustrating a characteristic curve of z and a distance z.

FIG. 5 is a diagram showing a basic configuration of a conventional optical displacement sensor disclosed in Japanese Patent Application Laid-Open No. 7-270120.

6 (a) and 6 (b) show the optical power on the optical axis and the distance from the optical axis even when the optical power of the light source for the sensor changes due to the change of environmental temperature or the like. It is a figure showing that the ratio of the optical power of point d becomes constant.

FIG. 7 is a diagram showing a light receiving element 32 in which a plurality of light receiving areas 33 are arranged at equal intervals in parallel with each other.

FIG. 8A shows that the light receiving area 33 is effective because the beam spot on the photodetector changes in both the x and y axes when the distance z between the light source and the photodetector changes in the conventional light source. FIG. 8B shows that when a surface emitting laser is used as a light source, the spread of the beam is reduced in the x-axis direction and adjusted to an appropriate size in the y-axis direction. FIG. 7 is a diagram showing that a beam spot shape on a light receiving area 33 can be appropriately designed.

FIG. 9 is a diagram showing a configuration of an optical displacement sensor according to the first embodiment of the present invention.

FIG. 10 is a diagram showing a surface of the photodiode 32 of FIG. 9 facing a surface emitting laser.

FIG. 11 is a diagram illustrating a structure of an example of the surface emitting laser 12 of FIG. 9;

FIG. 12 is a diagram showing a cross-sectional structure of a photodiode 32 for monitoring the intensity of the laser beam in FIG. 9;

FIG. 13 is a diagram showing a configuration of an optical displacement sensor according to a second embodiment of the present invention.

FIG. 14 is a diagram showing a configuration of a main part of an optical displacement sensor according to a third embodiment of the present invention.

FIG. 15 is a diagram showing a configuration of a main part of an optical displacement sensor according to a fourth embodiment of the present invention.

FIG. 16 is a diagram showing a configuration of a main part of an optical displacement sensor according to a fifth embodiment of the present invention.

FIG. 17 is a diagram showing a configuration of a main part of an optical displacement sensor according to a fifth embodiment of the present invention.

FIG. 18 is a diagram showing a configuration of a main part of an optical displacement sensor according to a fifth embodiment of the present invention.

[Explanation of symbols]

 12 vertical cavity surface emitting laser, 48 heat sink, 64 electric wiring, 62 LD drive power supply, 32 photodiode, 60 support plate, 70 electric wiring, 74 light receiving system power supply, 76 arithmetic Apparatus, 56 ... Mounting portion for moving object, 58 ... Support rod, 33 ... A plurality of light receiving areas, 77 ... Light receiving area selection device, 100, 102 ... Light receiving area, 14 ... N-type semiconductor substrate, 16 ... N-type semiconductor buffer Layers: 18 ... n-type semiconductor multilayer mirror, 20 ... n-type semiconductor cladding layer, 22 ... active layer, 24 ... p-type semiconductor cladding layer, 26 ... p-type semiconductor multilayer mirror, 28 ... p-type electrode, 30 ... n Type electrode, 34 ... n + type semiconductor substrate, 36 ... n-type layer, 40 ... antireflection film, 42 ... p-type electrode, 46 ... n-type electrode, 78 ... Si substrate, 80 ... adhesive layer, 82 ... spacer, 110 ... Beam spot, 63 ... LD selection device.

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Claims (3)

[Claims] A light source that emits a predetermined light beam; and a photodetector that receives the light beam emitted from the light source, and detects a change in an optical path length between the light source and the photodetector. In the optical displacement sensor, the photodetector has a plurality of light receiving regions arranged at predetermined positions, and is configured so that outputs can be independently taken out from the plurality of light receiving regions. Optical displacement sensor. 2. The apparatus according to claim 1, further comprising signal processing means for performing signal processing on an output selected in a predetermined manner from each output from the plurality of light receiving areas.
An optical displacement sensor according to claim 1. 3. The apparatus according to claim 1, further comprising signal processing means for calculating a ratio between a plurality of outputs selected by a predetermined method from respective outputs from the plurality of light receiving regions.
An optical displacement sensor according to claim 1.