JPH07202256A - Optical integrated sensor - Google Patents

Abstract

PURPOSE:To easily accurately position-detect with parallelism of emitting beams of a surface emitting laser and stability of an oscillating wavelength by disposing a surface light receiving laser (including the emitting laser) on one crystalline surface of a semiconductor substrate and a photodetector on the other crystalline surface. CONSTITUTION:Surface light emitting laser diodes LD1, LD2 with a distributed reflector as light sources are respectively formed on mesa oblique surfaces 111a, 111b, and symmetrically disposed on the two opposed oblique surfaces 111a, 111b. According to such a disposition, primarily diffracted optical beams emitted from the diodes LD1, LD2 and diffracted by a diffraction grating of a scale 10 are interfered, and incident to a top surface 100. Accordingly, when a photodetector is provided at an incident position of the surface 100, a variation in the diffracted light intensity responsive to movement of the scale 10 can be detected. Thus, accurate positional detection can be easily realized.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to optical sensors, and in particular
The present invention relates to an integrated optical sensor in which a laser light source and a sensor that detects reflected light from a target of light emitted from the laser light source are integrally formed on a substrate.

[0002]

2. Description of the Related Art As a conventional position detecting optical sensor or a micro encoder for optically detecting the position of an object using coherent light, as shown in FIG. There is one disclosed in the issue.

The microencoder 20 includes a semiconductor laser diode 22 integrally formed on a substrate 21, a first photodiode 23 as a photodetector, second and third photodiodes 24 and 25 for monitoring, and It includes five microlenses 26a to 26e.

The semiconductor laser diode 22 has a pair of symmetrical total reflection surfaces 22a and 22b in the middle of its excitation direction, and a pair of symmetrical output end surfaces 22c and 22d located on the optical axis of these total reflection surfaces. The optical axes are arranged so as to intersect at a predetermined position.

In the first photodiode 23, between the output end faces 22c and 22d of the semiconductor laser diode 22, the two light beams emitted from these end faces are diffracted by the scale 30 located at the proper position in the vertical direction Z. It is located at the intersecting position.

A pair of monitoring photodiodes 24, 25
Are both end faces 22c, 22 of the semiconductor laser diode 22.
On the outside of d, the two light beams emitted from both end surfaces are arranged at positions where they respectively receive the light components reflected by the scale 30 at the appropriate positions in the horizontal direction X.

Five microlenses 26a to 26e
Are both end faces 22c, 22 of the semiconductor laser diode 22.
d, first to third photodiodes 23, 24, 25
Are arranged at a total of five places in the vicinity of the light receiving surface.

The scale 30 is a micro encoder 20.
Extending in the horizontal direction X perpendicularly to the substrate 21. The scale 30 includes a substrate 31 and a large number of diffraction gratings 32 formed on one surface 31a of the substrate along the horizontal direction X at equal pitches. A reflection film (not shown) made of metal or the like is formed on the surface 31 a of the substrate 31 on which the diffraction grating 32 is formed so as to cover the diffraction grating 32.

Both end faces 22 of the semiconductor laser diode 22
The light beams 41 and 42 emitted from c and 22d are converged by the microlenses 26a and 26b, then intersect once and enter the scale 30. The light beams 41 and 42 incident on the scale 30 are diffracted by the diffraction grating 32 to become diffracted lights 43 and 44.

The diffracted lights 43 and 44 are transmitted to the microlens 26.
After passing through c, they interfere with each other to become interference light. The interference light is received by the first photodiode 23, and its light intensity is detected.

The first photodiode 23 generates a current according to the light intensity of the interference light, and the light intensity is between the light beams 41 and 42 and the diffraction grating 32, that is, the encoder 20 and the scale 30. Changes in proportion to the relative movement amount x in the horizontal direction X between.

FIG. 8 shows the relationship between the relative movement amount x and the output current value of the photodiode 23. As is apparent from FIG. 8, the current value shows a change represented by two sine waves with respect to the movement amount d of one pitch of the diffraction grating 32.

Therefore, if the number of peaks and troughs of the sine wave signal is counted, the movement amount can be measured with an accuracy of ¼ of the pitch of the diffraction grating 32. Further, if the current value is divided into N pieces for one sine wave, the resolution V is n times the number of diffractions.
Then, V = d / (2 · N · n) (1)

For example, when n = 1, N = 40 and d =
If it is 1.6 μm, the resolution V is 0.02 μm,
Highly accurate position detection becomes possible. On the other hand, there is the following relationship between the incident angle θ ₀ and the diffraction angle θ ₁ with respect to the scale.

Sin θ ₀ + sin θ ₁ = λ / d (2) where λ is the wavelength of the light beam emitted from the semiconductor laser diode. Second and third photodiode 2
Reference numerals 4 and 25 detect reflected light components of the light beams 42 and 41, respectively, and generate currents corresponding to their intensities. This light intensity is
Although it changes according to the distance between the encoder 20 and the scale 30 in the vertical direction Z, the diffracted light of the light beam emitted from the semiconductor laser diode 22 is properly incident on the photodiode 23 in advance when the light intensity is maximum. It is set. Further, the position of the encoder 20 or the scale 30 is controlled by a positioner or the like so that the light intensity becomes maximum.

In the encoder 20 described above, the light beams emitted from both end faces of the semiconductor laser diode can be effectively used as they are as two coherent light beams.
0 can be made extremely small.

[0017]

However, in the conventional encoder 20 described above, the oscillation wavelength of the semiconductor laser diode fluctuates from the viewpoint of its operation, and therefore the incident angle must be changed accordingly. There's a problem.

Next, the difficulty in manufacturing the conventional encoder 20 will be examined. The semiconductor laser diode 22 of the encoder 20 has a left-right symmetrical U-shape, and the phases and wavelengths of the beams emitted from both end faces 22c and 22d are matched. However, the total reflection mirrors 22a, 2
In order to form 2b, it is necessary to control center deviation and angular deviation with high accuracy. In addition, the end face 22 of the laser 20
In order to form c and 22d, it is necessary to form a mirror exactly perpendicular to the waveguide direction. Further, the microlenses 2 arranged near the laser end faces 22c and 22d.
A high-precision etching technique is required for aligning the optical axes of 6a and 26b.

On the other hand, from the viewpoint of the detection accuracy of the conventional encoder 20 described above, since the output fluctuation of the photodiode 23 with respect to the inclination of the scale 31 is large, the signal of the scale 31 must be within ± 1 ° from the horizontal direction X. Cannot be distinguished from noise, and there is a risk of erroneous detection, making accurate position detection difficult. SUMMARY OF THE INVENTION An object of the present invention is to provide an optical integrated optical sensor that easily realizes highly accurate position detection in view of the problems of the conventional optical integrated optical sensor described above.

[0020]

According to the present invention, in order to achieve the above object, a laser light source and a sensor for detecting reflected light of an emitted light of the laser light source from an object are integrally formed on a substrate. In the integrated optical sensor, the first surface is made of a single crystal, and has a first surface formed along a first crystal surface thereof and a second surface formed along a second crystal surface thereof. A semiconductor substrate arranged such that the normals of these two surfaces intersect with each other, and a surface emitting laser or laser diode formed on one of the first and second surfaces by vapor phase epitaxy. And an optical integrated sensor having a light receiving element formed on the other surface by a vapor phase growth method.

[0021]

In a normal semiconductor laser diode close to a point light source, the phenomenon of "laser oscillation mode jumping", so-called "mode hopping" occurs due to an increase in optical output and returning light. Moreover, since the emission spot is about 2 μm × 4 μm, the light beam emitted from the laser end face spreads,
It is necessary to reduce the beam diameter with a lens.

On the other hand, in the surface emitting laser light source with a distributed reflector, the distributed reflector plays the role of a wavelength filter, and the wavelength fluctuation can be suppressed to about two orders of magnitude lower than that of an ordinary semiconductor laser diode. Since the end face has a high reflectance of at least 90% with respect to the return light,
The fluctuation of the wavelength in the resonator due to the returning light is suppressed.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the position detecting optical sensor of the present invention constitutes a monolithic optical integrated circuit chip 50a. In the vicinity of the tip 50a, the mesa top surface 10 described later is formed.
A scale 10 that is substantially parallel to 0 is arranged, and a plurality of diffraction gratings 10a are arranged on this scale 10 at equal intervals along the extending direction. One of the scale 10 and the chip 50a is attached to the object whose position is to be detected.

On the surface of the GaAs compound semiconductor substrate (wafer) 1 of the optical integrated circuit chip 50a, a mesa type (plateau type) region 200 which is substantially perpendicular to the extending direction of the surface of the substrate 1 is etched. It is formed by. The side surfaces of the mesa region 200 extend from the mesa top surface 100 and both ends of the mesa top surface 100 as viewed from the direction normal to the paper surface of FIG. 1, and are inclined with respect to the mesa top surface 100. 1st and 2nd mesa inclined surface (crystal surface) 111a, 111
and b. The first and second mesa inclined surfaces 111a and 111b are arranged so that their normal directions intersect with each other. Specifically, the inclined surface 1
11a and 111b are 5 with respect to the top surface 100, respectively.
It has an inclination of 4.7 °.

Surface emitting laser diodes LD1 and LD2 as a light source are formed on the mesa inclined surfaces 111a and 111b, respectively, as light sources. These two laser diodes LD1 and LD2 are symmetrically positioned on the two inclined surfaces 111a and 111b facing each other. With this arrangement, the first-order diffracted light beams emitted from the laser diodes LD1 and LD2 and diffracted by the diffraction grating of the scale 10 interfere with each other and enter the top surface 100. Therefore, if a light receiving element is provided at the incident position on the top surface 100 as described later, a change in the diffracted light intensity according to the movement of the scale 10 can be detected. This change has a sine wave shape, and two cycles of sine waves can be detected for one pitch of the diffraction grating arranged on the scale 10.

In the following description, the first mesa sloped surface 111
The upper and lower reflectors of the surface emitting laser diode LD1 on a are denoted by reference numerals 2a and 7a, respectively, and the second mesa inclined surface 11 is provided.
The upper and lower reflectors of the surface emitting laser diode LD2 on 1b are designated by reference numerals 2b and 7b, respectively.

Surface-emitting laser diode LD with distributed reflector
1, LD2 are formed as follows. Mesa surface 10
For 0, 111a, 111b, the plane orientation is maintained by the vapor phase growth method, and the epi growth is performed by, for example, the MOVPE method. By confirming the growth rate on the mesa top surface 100 and the mesa inclined surfaces 111a and 111b in advance, the inclined surface 1
It is possible to stably form the multi-layer epi layer except for the edges of 11a and 111b and the boundary between the mesa top surface 100 and the mesa inclined surfaces 111a and 111b. The surface emitting laser diodes LD1 and LD2 are formed by performing selective dry etching on the multilayer epi layer.

In this case, the laser diodes LD1 and LD
The emission angle of the laser beam of 2 is relative to the surface of the substrate 1.
It is inclined 54.7 °. Surface emitting laser diode LD
1, the lower distributed reflectors 2a and 2b of LD2 are n-type Al
_{A 0.1} Ga _0.9 As layer and an n-type AlAs layer are formed in 30 periods with a layer thickness of 61.6 nm and 73.0 nm, respectively. When the oscillation wavelengths of the surface emitting laser diodes LD1 and LD2 are 0.87 μm, the reflectance of the lower distributed reflectors 2a and 2b is 99.9%.

The active layer 4 has a triple quantum well structure composed of a 10 nm GaAs quantum well and a 5 nm Al _0.3 Ga _0.7 As quantum well barrier layer. The active layer 4 has a layer thickness of 0.
11 μm n-type Al _0.45 Ga _0.55 As cladding layer 3 and p
It is sandwiched between the Al _0.45 Ga _0.55 As clad layer 5.

A p-type InGaP cap layer 6 having a layer thickness of 0.39 μm is formed on the p-type Al _0.45 Ga _0.55 As clad layer 5.
The upper distributed reflectors 7a and 7b are formed in 18 cycles via the. The structure of the upper distributed reflectors 7a and 7b is similar to that of the lower distributed reflectors 2a and 2b. However, the reflectance is
It is 95.6%.

The p-side electrode 9 is composed of upper distributed reflectors 7a and 7b.
Is formed on the outer periphery of the p-type InGap cap layer, and the n-side electrode 8 is formed on the outer periphery of the n-type cladding layer 5 and on the lower distributed reflectors 2a and 2b.

The diameter of the emission window of the surface emitting laser diode is
The diameter of the mesa is 15 μm and the diameter of the mesa is 20 μm. The protrusion distance from the surface of the semiconductor substrate 1 to the upper edge of the mesa region 10, that is, the depth of the mesa groove is set to 20 μm, and the width of the mesa bottom (the open end of the mesa slope 101a and the open end of the mesa slope 101b) is set. The width) is 100 μm.

The principle of laser oscillation in such a position detecting optical sensor is as follows. The carrier injected from the p-side electrode 9 has its resistance restored by annealing in the p-type doping region in the Ga ⁺ ion implantation region 12. However, the resistance of the n-type cladding layer 3 is p
It is a high resistance region in a state of being raised by two to five orders of magnitude above the shaped clad layer 5. Therefore, the carriers can move freely in the p-type cladding layer 5, but can move only in the central portion and in the vicinity of the distributed reflector in the n-type cladding layer 3. Therefore, the carriers concentrate on the active layer 4 in the central portion of the mesa directly below the upper reflector 7b. In the radial direction of the light emitted by the recombination of carriers, the quantum well structure is disordered by Ga ⁺ ion implantation, and the refractive index thereof is lowered. for that reason,
The light emitted by recombination of carriers has a small spread and is converged in the central portion.

The light propagating in the direction perpendicular to the joint surface is
Since the reflectance of the lower distributed reflector 2a does not change and is 99.9%, most of it is reflected by the lower distributed reflector 2a.
Here, the reflectance of the lower distributed reflector 2b does not change because
This is because the spectrum spread in the lower distributed reflector 2b is considered to be about 40 meV, which is the full width at half maximum and the photoluminescence of a multi-quantum well structure at room temperature.

The light propagating in the vertical direction is amplified only by the wavelength-selected light because the active layer 4 is located at the antinode of the standing wave. Since the amplified light has a high reflectance in the range of 96 ± 1% in the upper distributed reflector 7b, most of the amplified light is reflected by the upper distributed reflector 7b and amplified again in the active layer 4.

In the upper and lower distributed reflectors, only light of a limited wavelength repeats optical feedback, and laser oscillation occurs when the loss coefficient and the gain coefficient during the propagation match.
Unlike a laser diode emitted from a normal cleavage plane, a surface emitting laser diode has a cavity length of several μm, so that the number of standing wave modes existing is small and mode hopping does not occur in normal temperature operation. . Further, the end face protective film is unnecessary.

In this embodiment, the surface emitting laser diode L
D1 and LD2 are the first and second mesa inclined surfaces 111a and 1a.
Since 11b is formed symmetrically by vapor phase growth, the laser beam emission angle θ ₁ of the laser diodes LD1 and LD2 is constant at 54.7 °.

The pitch of the diffraction grating arranged on the scale 10 is set so that the first-order diffracted light is diffracted perpendicularly to the surface of the substrate 1. For example, assuming that the oscillation wavelength λ of the light beams emitted from the laser diodes LD1 and LD2 is 0.87 μm, the first-order diffraction angle θ ₁ = 0 °, so sin θ ₀ + sin θ ₁ = λ / d = sin θ ₀ = 0 .87 (μm) / d (3) is obtained. Here, the laser diodes LD1 and LD2
Incident angle θ ₀ of the emitted laser beam with respect to the scale 10
Is 54.7 °, d = λ / sin θ ₀ = 0.87 (μm) /0.816 = 1.066 (μm) is obtained from the equation (3). In this case, the diffracted light beam has a top surface 100
Is diffracted perpendicular to.

Surface emitting laser diodes LD1 and L on both sides
The beams emitted from D2 cross each other in front of the scale 10 and the first-order diffracted light beam diffracted by the surface of the diffraction grating of the scale 10 is incident on the light receiving element PD formed on the mesa top surface 100. The structure of the light receiving element PD and its forming method are the same as those of the laser diodes LD1 and LD2 from which the upper distributed reflector 7b is removed.

At this time, if the scale 10 is moving,
The intensity of the diffracted light beam changes sinusoidally in accordance with one pitch d of the scale 10. In the present embodiment, since the laser beams are incident on the scale 10 from the left and right sides in the drawing, the in-phase first-order diffracted light beams move in opposite directions and interfere with each other, so that the diffraction grating of the scale 10 has one pitch. On the other hand, a 2-cycle sinusoidal light receiving signal can be observed, and the accuracy of the moving distance is improved.

Since the incident angle of the incident beam is determined by the crystal plane, the first-order diffracted light can be returned perpendicularly to the surface of the mesa top surface 100 by matching the pitch of the diffraction grating with the diffraction condition. . If the diffracted light can be returned vertically to the light receiving surface in this manner, the distance between the scale 10 and the chip 50 is relatively wide (50 μm to 300 μm).
Can be set. Surface emitting laser diode LD
Since the area of the exit window of LD 1 and LD 2 can be ensured to be wide within the fundamental mode oscillation, the half-width can be suppressed to a spread of 2 to 3 degrees in the far field pattern, and the distance between the scale 10 and the chip 50a is relatively wide. Therefore, it is not necessary to focus the beam by the microlens.

Further, the laser diodes LD1 and LD2
Are disposed so that their emission beams intersect in front of the scale 10, so that the emission beams of one laser diode are not directly reflected by the other laser diode.

FIG. 2 shows a second embodiment of the present invention. The purpose of this embodiment is to scale 10 and optical integrated circuit chip 50b.
The signal output of the light receiving element at the bottom of the mesa is increased by controlling the distance y between and. The same components as those in the first embodiment are designated by the same reference numerals.

Left and right surface emitting laser diodes L in the X direction
The beams emitted from D1 and LD2 need to cross each other just before the scale 10. Therefore, in the optical integrated circuit chip 50b of the second embodiment, a pair of light receiving elements P is provided on the left and right of the surface emitting laser diodes LD1 and LD2, respectively.
D1, PD2, PD3 and PD4 are formed. The structure of these light receiving elements PD1, PD2, PD3, PD4 is
Surface emitting laser elements LD1 and LD2 to upper distributed reflector 7
It is the same as that in which b is removed.

Surface emitting laser diode LD1 (LD2)
And the left and right light receiving elements PD1 and PD2 (PD3, PD
4) is electrically isolated from the Ga ⁺ ion implantation region 12. Ga ⁺ ion implantation (dose amount 4 × 10
^{At 14} cm ⁻² ), the resistivity of the p-side epilayer after annealing returns to that before ion implantation. This is because the n-side region becomes a high-resistance region having a resistivity that is 2 to 5 orders of magnitude higher than that of the p-side region, and the quantum well structure is disordered.

When the value of the distance y between the scale 10 and the chip 50b is increased, the surface emitting laser diode LD1 (LD2) is changed from the state where the reflected laser beam (B) is received by the light receiving element PD1 (PD3). The emitted laser beam (A) is the surface emitting laser diode LD2 (L
Incident on the reflected beam (B) of D1) causes interference, which causes output fluctuation. As a result, the light receiving element P
A signal of the reflected beam (B) is obtained by D2 and PD4. The distance between the exit window end of the surface emitting laser diode LD1 (LD2) and the lower part of the light receiving window of the upper light receiving element PD2 (PD4) is set to 10 μm, and the amount of movement of the beams from the left and right from the crossing position is reduced to 1 A large signal-to-noise ratio of the second-order diffraction interference beam signal can be obtained. Therefore, since the light beam output of the surface emitting laser diodes LD1 and LD2 can be small, the diode LD accompanying the laser beam generation
1, the amount of wavelength shift due to heat generation of the LD 2 can be suppressed as much as possible.

The surfaces of the light receiving elements PD1 to PD4 are p-
Since it is protected by the InGaP layer 5, it is strong against oxidation, and ohmic resistance is easier than that of AlGaAs material. On the other hand, when the surface of the scale 10 that moves with respect to the optical integrated circuit chip 50b is inclined, the signals of the light receiving elements PD1 to PD4 have a significantly deteriorated signal-to-noise ratio. For example, the encoder 20 of the conventional example (see FIG. 7) cannot detect a signal unless the tilt of the diffraction grating is controlled within ± 1 degree.

However, as shown in FIG. 3, when the pitch and aspect ratio of the diffraction grating are optimized to 1.5 or more, the intensity of the diffracted light beam with respect to the incident light beam is 80%.
That is all. Therefore, the scale 10
It is more effective to detect the inclination of.

For example, the distance y is 100 μm, the light receiving element P is
The distance between the centers of the light receiving surfaces of D1, PD2 and PD3 is 5 μm,
Assuming that the light receiving surface is 3 μm × 3 μm and the beam spread is ± 1 degree, the center of the diffracted light beam is inclined by 2 degrees when the scale 10 is inclined by 1 degree. Therefore, the center of the diffracted light beam moves to one end of the light receiving surface of the light receiving element PD2 in the vertical direction (Z direction) of FIG. 3, and the beam does not reach the center of this light receiving surface. As a result, the light receiving element P
The output of D2 decreases and the output of the light receiving element PD1 or PD3 increases. To which the scale 10 has moved,
The output of the light receiving elements PD1 and PD3 can be easily detected by comparing the outputs, so that the inclination of the scale 10 can be easily controlled.

FIG. 4 shows a third embodiment of the present invention. The same components as those in the first embodiment are designated by the same reference numerals. In the third embodiment, it is assumed that the semiconductor substrate 1'of the monolithic optical integrated circuit chip 50c is a window substrate that does not absorb the oscillation wavelength of the surface emitting laser diode. In this case, as shown in FIG. 4, a beam is emitted from the back surface of the substrate 1 ', intersects it just before the scale 10, and the interference pattern of the diffracted light beam is again measured on the top surface 1 of the mesa of the substrate.
A method of receiving the position detection signal by the light receiving element PD of 00 'can be considered.

In FIG. 4, a forward mesa region is formed on the GaAs compound semiconductor substrate 1'by wet etching. Here, the mesa height is 20 μm, the width of the mesa top is 200 μm, and the width of the mesa bottom is 50 μm. The surface emitting laser diodes LD1 and LD2 and the light receiving elements PD1 ', PD2' and PD3 'are integrally formed by a vapor phase growth method, for example, a MOVPE method. That is, the mesa top surface 100 'and the mesa inclined surfaces 111a', 1
11b 'has 71.2 nm n-type GaAs and 84.8 nm.
A lower distributed reflector 101 is formed in which 14 pairs of nm with n-type AlAs are formed. This distributed reflector 10
The reflectance of 1 is 90%. An n-type Al _0.3 Ga _0.7 As clad layer 102 and a p-type Al _0.3 Ga _0.7 As clad layer 10 are formed on the distributed reflector 101 on the mesa top surface 100 ′.
4 are formed so as to sandwich the triple quantum well structure active layer 103.

Here, the thickness of the cladding layer 104 is one cycle (0.275) where the active layer 103 is the antinode of the standing wave.
μm). The structure of the active layer 104 is a triple strain quantum well structure including an In _0.2 Ga _0.8 As strain quantum well of 8 nm and a GaAs quantum well barrier layer of 5 nm.

Between the upper distributed reflector 106 of the laser diodes LD1 and LD2 and the p-type cladding layer 104, p-type In is formed in consideration of oxidation prevention and ohmic characteristics with the electrode.
The GaP layer 105 is provided for one wavelength (0.3 μm). .

The above-mentioned upper distributed reflector 106 has the same composition and the same thickness as the lower distributed reflector 101, is formed for 21 cycles, and is not particularly doped with impurities. The reflectance of this portion is 99% or more, and the surface emitting laser diodes LD1 and L
A light receiving element PD used as a light receiving element except D2
In 1 ', PD2', PD3 ', this upper distributed reflector 1
06 has been removed.

A pair of laser diodes LD1 (LD
2) and the light receiving element PD1 '(PD2') are separated as follows. That is, at least n-type Al a p-type Al _0.3 Ga _0.7 As cladding layer 104 surface _0.3 Ga _0.7
Until reaching the As cladding layer 102, implanting Ga ⁺ ions, it is electrically separated by the Ga ⁺ ion implanted n-type regions in a high resistance. .

The operating principle of the optical sensor 50c of FIG. 4 is as follows. A stable beam having a wavelength of 0.98 μm is incident on the moving scale 10 from the surface emitting laser diodes LD1 and LD2.

At this time, the two laser diodes LD1,
When the LD 2 is emitted from the center of the inclined surfaces 111 a ′ and 111 b ′, the focal point thereof is located 105 μm downward from the mesa top surface 100 ′ when viewed in the Z direction. Here, the thickness of the GaAs compound semiconductor substrate 1'is set to 8
Assuming 0 μm, the laser diodes LD1 and LD2 are
Through the substrate 1 ', the focal point will be 25 μm below the back surface of the substrate 1'. At this point, the emitted beams of the two laser diodes LD1 and LD2 are reflected toward each other's laser diodes LD1 and LD2. Therefore, the two laser diodes LD1 and LD2 cannot be used for position detection because of fluctuations in their laser outputs.

However, below the above-mentioned focal point, the interference light beam of the first-order diffracted light beam C of the two laser diodes LD1 and LD2 is the mesa top surface 100 '.
Is detected as a position detection signal by the light receiving element PD3 '. In this case, since the vertical incidence allows a large signal-to-noise ratio, a highly accurate position sensor can be realized.

Therefore, the surface emitting laser diode LD1
By providing the light receiving element PD1 '(PD2') adjacent to (LD2) below, the reflected light beam B from the scale 10 can be monitored and the distance y between the scale 10 and the chip 50c can be controlled.

By making the distance between the adjacent light receiving element and the surface emitting laser diode relatively narrow (5 μm), the distance from the focal length is made small. The area of the reflection surface of the upper reflector 106 of the surface emitting laser diode LD2 is 100 μm × 100 μm, and the fundamental mode oscillation of the beam on the emission side is maintained. On the other hand, the light receiving element PD
3'has a distance from the scale 10 of about 150 μm, so that the area of the light receiving surface is relatively widened (100 μm × 100 μm) so as to secure a wide light collecting area.

Since the reflectance of the lower distributed reflector 101 of the surface emitting laser diode LD1 is 90%, the amount of light passing through this region is 10% or less, so that the diameter of the light receiving element is made large. This is because it is desirable.

On the other hand, the light receiving element adjacent to the surface emitting laser can control the position of the distance y if only the peak value can be detected, so that the light receiving diameter is relatively narrow (5 μm).
m) has been done.

FIG. 5 shows a fourth embodiment of the present invention. The same components as those in the first embodiment are designated by the same reference numerals. The purpose of this fourth embodiment is a simple position detection monolithic optical integrated circuit chip 50 used when the required movement amount detection accuracy is relatively low (about several μm).
to provide d. In this embodiment, the change in intensity of the 0th-order diffracted light beam (reflected light beam) is used to detect the amount of movement of the object. In the fourth embodiment, the first and second mesa inclined planes (crystal planes) 111 of the mesa region 200 are formed.
A light receiving element PD 'and a surface emitting laser diode LD are formed on a and 111b, respectively.

Light receiving element P on the second mesa inclined surface 111b
The light receiving area of D'is relatively widened. Fourth
The scale 10 'of the embodiment is different from the scales 10 of the first to third embodiments in that the pitch spacing d of the diffraction grating 10a' is different.
Is a rough one of several μm or more.

The scale 10 'is designed so that the convex portion has a high reflectance, and the concave portion diffuses the incident light beam and reduces the amount of reflected light returning to the light receiving element PD' by an order of magnitude. In this way, by increasing the reflectance of the convex portion of the scale 10 'and irregularly reflecting (lowly reflecting) the concave portion, the intensity of the reflected light beam can be obtained. Therefore, depending on the amount of movement of the scale 10 ', the peaks and troughs of the reflected light beam can be detected one-on-one. In this case, scale 1
0 ', the surface emitting laser diode LD and the light receiving element PD'
If the distance between and is set to the peak value of the reflected light beam,
The amount of movement of the scale 10 'can be detected by measuring the number of peak values.

In the fourth embodiment, the laser diode L
When the diameter of the exit window of D is relatively large, for example, 15 μm, the divergence of the surface emitting laser beam is ±
It will be less than once. Further, since the quantum well structure is used for the upper and lower distributed reflectors and the active layer, the fluctuation of the oscillation wavelength is stable by two digits or more as compared with the usual semiconductor laser diode.

According to such a simplified optical sensor 50d, the scale 10 'is located at the focus position of the laser diode LD.
Can be controlled. Furthermore, since the device configuration is simple, an inexpensive optical sensor is provided.

In the case of a parallel light beam having a small beam divergence, the signal output of the light receiving element PD abruptly changes at the point of transition from the convex portion to the concave portion of the scale 10 ', and the peak of the signal corresponding to the pitch interval of the diffraction grating. The value is detected. In other words, the position detection accuracy depends on the pitch width.

FIG. 6 shows a fifth embodiment of the present invention. The purpose of this embodiment is to provide an optical sensor 50e in which the accuracy of the simplified position detecting optical sensor 50d of the fourth embodiment of FIG. 5 is further enhanced. The same components as those in the fourth embodiment are designated by the same reference numerals.

In FIG. 6, a surface emitting laser diode L
D and the scale 10 ″ are the spot diameters when the emission beam of the laser diode LD is incident on the scale 10 ″.
It is designed to be about half the pitch width of the diffraction grating 10a ″ of the scale 10 ″.

On the other hand, the light receiving element PD "is composed of two divided elements PD1" and PD2 "whose light receiving diameter is divided into two, and the peak value of the signal for the scale 10" is 1/2 for the element PD1 "and the element PD2". It is designed to be delayed by 4 pitches. Further, the center of the light receiving element PD ″ is located at the center of the Ga ⁺ ion implantation region 12, and the dividing elements PD1 ″ and PD2 ″ are located.
And the light receiving surface are separated by 3 μm.

The mesa region 200 of FIG. 6 has a depth of 20 μm and a width of the mesa bottom of 100 μm, for example. In the center of the inclined surface 111b, a surface emitting laser diode LD that oscillates in the fundamental mode in a window region of 10 μmφ is formed.
The focus position of this laser diode LD is y = 32.5.
μm. Install a scale 10 "at this focal point,
By moving in the X direction and detecting the sum of the signals of the dividing elements PD1 ″ and PD2 ″, the position detection accuracy increases.

For example, assuming that the divergence angle of the emission beam of the laser diode LD is ± 1 degree, the spread of the beam spot on the scale 10 ″ surface is 4.5 μm. The pitch spacing of the diffraction grating of the scale 10 ″ is By making it narrower than 4.5 μm and wider than 1.1 μm where the first-order diffracted light beam is larger than the reflected light beam, the signals of the splitting elements PD1 ″ and PD2 ″ that receive the reflected light beam are detected. It can be delayed by 1/4 pitch.

Here, regarding the relationship between the pitch interval of the diffraction grating and the wavelength of the incident light, when the pitch interval of the diffraction grating and the wavelength are approximately the same length, the emitted light detected is mainly the diffracted light, As the pitch interval of the diffraction grating increases with respect to the wavelength, the reflected light component increases, and when the pitch interval becomes 5 times or more the wavelength, the diffracted light disappears and the reflected light is detected. Therefore, it is preferable that the pitch interval of the diffraction grating is at least 5 times or more the wavelength of the incident light.

[0075]

As described above, according to the optical integrated photosensor of the present invention, the surface emitting laser (including the surface emitting laser diode) is provided on one crystal face of the semiconductor substrate and the other crystal face is provided on the other crystal face. Since the light-receiving element is arranged with high precision in this, high-precision position detection can be easily performed in combination with the parallelism of the emitted beam of the surface-emitting laser and the stability of the oscillation wavelength.

[Brief description of drawings]

FIG. 1 is a schematic view showing a partially broken optical sensor for position detection according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a second embodiment corresponding to FIG.

FIG. 3 is a side view of the optical sensor of FIG. 2 viewed from the scale side.

FIG. 4 is a schematic diagram showing a third embodiment corresponding to FIG.

FIG. 5 is a schematic diagram showing a fourth embodiment corresponding to FIG.

FIG. 6 is a schematic view showing a fifth embodiment corresponding to FIG.

FIG. 7 is a configuration diagram showing a conventional optical encoder.

8 is a graph showing an example of an output signal of the device of FIG.

[Explanation of symbols]

1, 1 '... GaAs compound semiconductor substrate (semiconductor substrate), 50a, 50b, 50c, 50d ... Monolithic optical integrated circuit chip (optical integrated optical sensor), 111a, 1
11a '... first mesa inclined surface (first crystal surface), 111
b, 111b '... second mesa inclined surface (second crystal surface),
LD1, LD2 ... Surface emitting laser diode (surface emitting laser), PD, PD ', PD1, PD2, PD3, PD
4, PD1 ', PD2', PD3 ', PD1 ", PD
2 ″ ... light receiving element.

Claims (1)

[Claims] 1. An integrated optical sensor in which a laser light source and a sensor for detecting reflected light from an object of light emitted from the laser light source are integrally formed on a substrate, and the integrated light sensor comprises a single crystal. Having a first surface formed along the crystal plane of and a second surface formed along the second crystal plane, and arranged so that the normals of these two surfaces intersect with each other. A semiconductor substrate, a surface emitting laser or laser diode formed on one of the first and second surfaces by a vapor phase growth method, and a light-receiving device formed on the other surface by a vapor phase growth method. An integrated optical sensor including an element.