JP2003008515A - Photodetector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photodetector that can correctly adjust a direction of a light receiving element and an emission direction of an emission light depending on the position of a light emitting unit of an opposite party. SOLUTION: In a light receiving/light emitting device that applies emission direction control to a luminous flux depending on positions between a light receiving element and a light emitting element in 2-way communication by the collimated luminous flux with a small diameter, a diffraction lens generates a ± linear diffraction light coaxially and the device receives the lights at a position at which the both lights are overlapped with the same diameter to eliminate a detection error caused by deviation in the luminous intensity distribution in the luminous flux and the vignetting of luminous flux so as to conduct stable attitude control in the 2-way communication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting / receiving unit used for optical communication.

[0002]

2. Description of the Related Art In recent years, an optical wireless LAN has been proposed as a LAN system for connecting a plurality of computers to each other in a premises. In this optical wireless LAN, a transmitting / receiving device (or a light emitting / receiving device) capable of receiving / transmitting or receiving / emitting a light signal is connected to, for example, a master computer and a slave computer, respectively, and the light emitting / receiving device is connected between these devices. Transmits and receives optical signals. More specifically, the light emitting / receiving device emits and receives a visible light beam modulated by an information signal.

Such a light emitting / receiving device or a light emitting / receiving unit has a light receiving element for receiving incident light. The light receiving element must be oriented in the correct direction for the incident light in order to properly receive the incident light. More specifically, for example, the orientation of the light receiving element must be adjusted so that the optical axis of the light receiving element (a straight line orthogonal to the light receiving element and passing through the center of the light receiving element) matches the optical axis of the incident light.

Further, when the light beam is emitted, the direction of the light beam must be properly adjusted with respect to the receiving and emitting unit of the other party.

In this case, for example, the incident angle of the incident light or the light spot position on the light receiving element is detected, and the direction of the light receiving element is adjusted based on the detection result.
Adjust the emission direction of the light beam.

[0006]

However, in two-way optical communication using a small-diameter parallel light beam (small-diameter parallel light beam), deviation of the light intensity distribution or aperture in the light beam is detected in detecting the incident angle of the light beam. If an error occurs due to "vignetting", the control of the light receiving element and the emitting direction becomes difficult.

An object of the present invention is to solve the above-mentioned problems, and the direction of the light receiving element and the emission direction of the emitted light are
An object of the present invention is to provide a photodetector that can be adjusted correctly according to the position of the light emitting unit of the other party.

Alternatively, even if the light beam from the other light emitting unit has a deviation in the light intensity distribution or "vignetting" occurs due to the aperture, the light receiving element and the light detecting direction can be adjusted appropriately. It is to provide a device.

[0009]

A photo-detecting device of the present invention is a photo-detecting device for detecting an incident position or an incident angle of an incident light beam based on an incident position or an incident spot shape of the incident light beam. Means, diffractive means, and light receiving element, the condensing means, diffractive means, and light receiving element are arranged on the same optical axis, and the diffractive means is substantially equal to ± first-order diffracted light generated by diffraction. The light receiving element has a diffraction efficiency and has the property of a lens which is approximately axisymmetric so as to impart lens power to the ± 1st-order diffracted light so that both the ± 1st-order diffracted light are condensed on the optical axis. Is arranged at a predetermined position on the optical axis where the beam diameters of the ± 1st-order diffracted lights substantially match.

Further, the light emitting and receiving device of the present invention is a light emitting and receiving device which transmits and receives an optical information signal and detects the incident position and the incident angle of an incident light beam from another light emitting and receiving device. A light splitting element, a condensing means, a diffracting means, and a light receiving element, wherein the condensing means, the diffracting means, and the light receiving element are arranged on the first optical axis, and the second light is defined by the light emitting element. The axis is branched from the first optical axis by the light branching element, the diffracting means has a diffraction efficiency substantially equal to the ± first-order diffracted light generated by diffraction, and both the ± first-order diffracted light are The light receiving element has a property of a substantially axially symmetric lens that imparts lens power to the ± 1st-order diffracted light so that the light is converged on the optical axis. It is arranged at a predetermined position on the shaft.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. In the drawings, the same or similar members or elements are given the same or similar reference numerals.

FIG. 1 shows an example of a light emitting / receiving unit as a light emitting / receiving device used for optical communication such as a local optical wireless LAN.

As shown in FIG. 1, the light emitting / receiving unit has a base unit side light emitting / receiving unit 21 connected to the base unit computer and a handset unit side light emitting / receiving unit 23 connected to the handset computer. In the example shown in FIG. 1, the master side light emitting / receiving unit 21 is installed, for example, on a ceiling, and the slave side light emitting / receiving unit 23 is installed on a table or the like of a user who is a user of the slave side computer.

FIG. 1A shows an initial state in bidirectional communication, in which the modulated light beam L'from the base unit 21 is transmitted.
Is transmitted to the slave unit 23.

As shown in FIG. 1B, when the slave unit 23 detects the incident direction or the incident position of the light beam L ', the light L emitted to the master unit 21 is detected based on the detection result. Adjust the direction of.

Thus, the light emitting / receiving unit 21 and the light emitting / receiving unit 23 mutually transmit and receive the modulated light beams, so that the master computer and the slave computer can mutually perform optical communication or optical information transmission.

FIG. 2 shows, for example, a slave side light emitting / receiving unit 23.
The configuration of is schematically shown.

As shown in the figure, the light emitting / receiving unit 2
3 includes a fisheye lens 25, a biaxial rotation frame 27, a light receiving element 29, a converging convex lens 31, a light emitting laser 33, a collimator convex lens 35, a half mirror 37, and a light shielding portion 39.

The fish-eye lens 25 enables transmission / reception of a light beam to / from the base unit 21 arranged at an arbitrary position on the ceiling that spreads over a large angle of view with respect to the light emitting / receiving unit 23. More specifically, for example, the incident light from the main unit side unit 21 that is incident at a large incident angle is converted into an incident angle within an appropriate range and is emitted to the light receiving element 29.
Further, the emitted light from the light emitting laser 33 having an emission angle within a predetermined range is emitted toward the master unit side unit having an arbitrary angle.

The biaxial rotation frame 27 has a rotation center o.
It is provided on the fixed frame 41 so as to be rotatable about 1 along two axes. Further, the light receiving element 29, the condenser convex lens 31, the light emitting laser 33, the collimator convex lens 35,
The half mirror 37 and the light shielding portion 39 are the rotating frame 27.
Substantially fixed to. Therefore, the frame 27
Rotation of the incident light L'to change the direction of the light receiving element 29, for example.
Can be appropriately adjusted according to the orientation of the.

The converging convex lens 31 condenses the incident light L'from the base unit 21 on the light receiving element 29, for example.

The light emitting laser 33 emits a modulated light beam for communication with the base unit 21.

The collimator convex lens 35 is used for the light emitting laser 3
The light beam from 3 is converted into parallel light.

The half mirror 37 includes a collimator lens 3
The light beam from 5 is emitted toward the base unit 21 (via the fisheye lens 25) and the base unit 2
The incident light L ′ from 1 is transmitted to the light receiving element 29.

The light-shielding portion 39 has an aperture 39a having a predetermined diameter.
And narrows the incident light L ′ from the base unit 21 to generate a light beam L having a small diameter.

Here, the aperture 39a is arranged at the following predetermined position with respect to the light receiving area of the light receiving element 29. That is, for the incident light L ′, the light receiving element 2
9 is in the right direction (for example, the incident light L '
Is vertically incident on the light receiving element 29), the center of the light spot formed on the light receiving element by the light beam L is arranged so as to coincide with the center o (FIG. 4) of the light receiving area a1-d1.

With the above construction, as will be described later, the biaxial rotation frame 27 is not oriented in the correct direction and the incident light L'is not.
When is incident on the light receiving element 29 with an inclination, this inclined incident state can be easily detected. In addition,
As long as the incident light L ′ is vertically incident on the light receiving element 29, the incident position of the incident light L ′ on the aperture 39a does not matter. That is, even if the incident position shifts laterally with respect to the aperture 39a, the position and shape of the small-diameter light beam L do not change, and the detection operation is not affected.

FIG. 3 shows a detailed structure of the light receiving element 29.

As shown in the figure, the light receiving element 29 has error detection areas a1, a2, b1, b2, c1, c for detecting whether or not the incident light beam is applied to a predetermined position.
2, d1 and d2, and an information signal detection area a2 which is provided at the irradiation position of the incident light beam when the incident light beam is incident on the predetermined position and which has substantially the same spread as the irradiation area of the incident light beam. , B2, c2, d2.

More specifically, the information signal detecting area a
2, b2, c2, d2 are error detection areas a1, a2,
It has an area smaller than b1, b2, c1, c2, d1, d2 and is formed inside the error detection region. Here, the light receiving areas a2 and b as the information signal detecting areas are provided.
2, c2 and d2 are preferably shared as an information signal detecting area and an error detecting area.

Further, the error detecting area is a plurality of light receiving areas a1, b1, c surrounding the information signal detecting area.
1 and d1. More specifically, the error detection area has a plurality of light receiving areas a1, b1, c1, d1 that surround the information signal detection area from four sides.

Light receiving area a as the error detecting area
1, a2, b1, b2, c1, c2, d1, d2 are 8
Number of divided areas a1, a2, b1, b2, c1, c2, d
1, d2. The eight light receiving regions are formed by dividing, for example, a rectangular light receiving region 291 formed on a semiconductor substrate into two crossing axes 43 and 45 which are orthogonal to each other, and an intersection o of the splitting axes 43 and 45. It is formed by dividing the circle C as the center.

The light receiving / emitting unit 23 has light receiving areas a1, a2, b1, b2, c1, c2, d1, d2.
X-direction (horizontal direction) angle deviation error signal based on the output from TLEx = (a1 + a2 + d1 + d2)-(b1 + b2
+ C1 + c2) X direction angle deviation error signal detection circuit (not shown) and Y direction (vertical direction) angle deviation error signal, TLEy = (a1 + a2 + b1 + b2)-(c1 + c2
A Y-direction angle deviation error signal detection circuit (not shown) that outputs + d1 + d2) is provided. Where a1, a2, b1, b2
c1, c2, d1 and d2 are light receiving areas a1, a2 and b
The output of 1, b2, c1, c2, d1, d2 is shown.

The light emitting / receiving unit 23 also outputs an information signal (or a modulation signal or a main signal), SIG = a2 + b2 + c2 + d2, based on the outputs from the light receiving areas a2, b2, c2, d2. (Not shown).

The light emitting / receiving unit 23 is further provided with the rotating frame 2 based on the output from each of the error detecting circuits.
A servo drive circuit for servo-driving 7 is provided (not shown).

Next, the operation of the light emitting / receiving unit 23 will be described.

FIG. 4 is an explanatory view showing a normal operation of the light emitting / receiving unit 23.

As shown in FIG. 4A, when the incident light L'is incident on the light receiving and emitting unit 23, the incident direction is inclined with respect to the optical axis n of the light receiving element 29 and the aperture 39a. The light spot S1 of the incident light L is formed at a position deviated from the center o of the light receiving element.

FIG. 4B shows the position of the light spot S1 on the light receiving element 29 in detail. As shown in the figure, the optical axis of the incident light L or the center of gravity SW of the light spot S1 is located at a position displaced from the center o of the light receiving element.

At this time, the error detection circuit outputs error signals TLEx and TLEy different from zero according to the deviation amount. A servo drive circuit that servo-drives the rotating frame 27 operates based on the error signals TLEx and TLEy, and the rotating frame 2 is adjusted so that the center SW of the light spot S1 coincides with the center o of the light receiving element 29.
7 is rotated along the two axes (FIG. 4 (c)).

At this time, as described above, the light spot S
The outer periphery of 1 corresponds to the outer peripheral edge C of the regions a2 to d2.
Therefore, the information signal or the modulation signal, SIG = a2 + b2 + c2 + d2, added to the light beam L ′ based on the outputs from the light receiving regions a2 to d2, is output from the information signal detection circuit.

Further, as shown in FIG. 1B, the emitted light L ″ from the light emitting laser 33 is emitted toward the base unit 21 through the lens 35, the mirror 37 and the fisheye lens 25. It

As a result, the light emitting / receiving unit 21 and the light receiving / emitting unit 23 mutually receive and emit light beams, and the master computer and the slave computer can perform optical communication.

In FIG. 5A, an error occurs in the angle control of the light beam L ′ emitted from the master unit side unit 21 to the slave unit side unit 23, and the light beam L ′ from the master unit side unit 21 is generated.
The case where the contour F ′ does not enter the entire aperture 39a of the light shielding unit 39 is shown.

In this case, the light spot S2 is formed only on the shaded portion in the aperture image 39b on the light receiving element 29.

FIG. 5B shows the positional relationship between the aperture image 39b and the light spot S2 and the center o of the light receiving element 29. As shown in the figure, in this case, the center of the aperture image 39b and the center o of the light receiving element 29 are separated from each other, and the light emitting / receiving unit 23 is not oriented in the correct direction. In other words, the aperture 39a and the light receiving element 2
The optical axis of 9 does not coincide with the optical axis of the incident light L '(or is not correctly oriented in the direction of the base unit 21).

However, in this case, the aperture image 39
Since only the light spot S2 in b is irradiated, the posture of the light emitting / receiving unit 23 is not properly controlled. More specifically, the outputs TLEx and TLEy from the error detection circuit do not reflect the error between the optical axis of the aperture 39a and the light receiving element 29 and the optical axis of the incident light L '. Therefore, it becomes impossible to control the attitude of the light emitting / receiving unit 23 based on the outputs TLEx and TLEy from the error detection circuit.

Therefore, in this case, as shown in FIG. 5C, the light beam L ″ from the slave unit 23 does not reach the master unit 23 and causes an angle error, and the slave unit 2 does not reach the master unit 23.
The communication from the unit 3 to the base unit 21 is not performed.

FIG. 6 shows an embodiment of the light emitting / receiving unit of the present invention.

The light emitting / receiving unit 123 can control its posture even when the phenomenon of FIG. 5 occurs.

The light emitting / receiving unit 123 transmits / receives an optical information signal and detects an incident position or an incident angle of an incident light beam from another light emitting / receiving device. The light emitting element 133 and the light branching element 137. And the light collecting means 131
And a diffracting means 147 and a light receiving element 129. The condensing means 131, the diffracting means 147, and the light receiving element 1 are provided.
29 is arranged on the first optical axis, the second optical axis defined by the light emitting element 133 is branched from the first optical axis by the light branching element 137, and the diffracting means 147 causes ± 1 generated by diffraction. A lens having substantially the same diffraction efficiency with respect to the first-order diffracted light and imparting lens power to the ± first-order diffracted light so that both the ± first-order diffracted light are condensed on the first optical axis. And the light receiving element is arranged at a predetermined position on the optical axis where the luminous flux diameters of the ± first-order diffracted lights substantially match.

The details are as follows.

As shown in FIG. 6, this light emitting / receiving unit 1
23 is a fish-eye lens 125 and a biaxial rotation frame 127.
, A light receiving element 129, a converging convex lens 131, a diffractive lens 147, a light emitting laser 133, a collimator convex lens 135, a half mirror 137, and a light shielding portion 139.
And.

Here, the fisheye lens 125, the biaxial rotation frame 127, the light receiving element 129, the condenser lens 131, the light emitting laser 133, the convex lens 135 for the collimator, the half mirror 137, and the light shielding portion 139 are respectively the fisheye lens 25 shown in FIG. The biaxial rotation frame 27, the light receiving element 29, the condenser convex lens 31, the light emitting laser 33, the collimator convex lens 35, the half mirror 37, and the light shielding portion 39 have the same structure and function. The light blocking portion 139 is provided with the aperture 39.
It has an aperture 139a similar to a.

The diffractive lens 147 is composed of a diffraction grating or a hologram lens. The diffractive lens 147 has substantially the same diffraction efficiency as the ± 1st-order diffracted light generated by the diffraction, and the ± 1st-order diffracted light is converged on the first optical axis together. It has the property of a lens which is almost axisymmetric and gives lens power to the folded light. Further, the diffractive lens 147 is designed so that the intensity of the 0th-order diffracted light becomes almost zero.

FIG. 7 shows the converging convex lens 131 and
The configuration and operation of the diffractive lens 147 and the light receiving element 129 are shown.

As shown in FIG. 7A, the converging convex lens 131, the diffractive lens 147, and the light receiving element 129 are arranged in series on substantially the same optical axis. Then, the light receiving element 12
Reference numeral 9 is arranged at the approximate focus position on the optical axis of the condenser lens 131 and perpendicular to the optical axis. In the figure, the light shielding portion 139
And apertures 139a are functionally described, in fact they are located above lens 131.

The incident light L incident on the condensing lens 131 is condensed by the condensing lens 131 and enters the diffractive lens 147. For example, the + 1st order diffracted light given a convex lens power by the diffractive lens 147. L + and, for example, −1st order diffracted light L− to which the concave lens power is added are generated.

The + 1st order diffracted light L + is received by the light receiving element 129.
In front of (or upward in FIG. 7A). Therefore, when the incident light on the diffractive lens 147 has an intensity distribution, a light spot (an inverted image) having an intensity distribution in the opposite direction to the intensity distribution of the incident light is formed on the light receiving element 129.

The -1st order diffracted light L- is focused behind the light receiving element 129 (or below in FIG. 7A). Therefore, when the incident light on the diffractive lens 147 has an intensity distribution, a light spot (an erect image) having an intensity distribution in the same direction as the intensity distribution of the incident light is formed on the light receiving element 129.

FIG. 7 (b) shows that the + 1st order diffracted light L +
A three-dimensional beam shape and a light spot S3 generated thereby on the light receiving element 129 are shown.

On the other hand, FIG. 7C shows the -1st order diffracted light L
-The three-dimensional beam shape and the light receiving element 129
The shape of the light spot S4 generated above is shown.

As described above, an inverted image of the intensity distribution of the incident light on the diffraction lens 147 is formed on the light spot S3, and an erect image of the intensity distribution of the incident light is formed on the light spot S4. To be done.

The inverted image and the erected image have the same intensity as the intensity distribution of the incident light on the diffraction lens 147 and have the same scale.

FIG. 8 shows a case where the light beam L'which is displaced with respect to the aperture 139a as shown in FIG.

More specifically, FIG. 8A shows a light spot S5 on the light receiving element 129 by the + 1st-order diffracted light L + when the light beam L'which has been displaced is incident on the light emitting / receiving unit 123.

Further, FIG. 8 (b) shows − in the above case.
The light spot S6 by the first-order diffracted light L- is shown.

In the figure, reference numeral 139b shows an image obtained by the lenses 131 and 147 of the aperture 139a.

9A and 9B show the light receiving element 129.
The top view of the upper light spots S5 and S6 is shown.

As described above, the light spot S5 of the + 1st order diffracted light is an inverted image of the intensity distribution of the light incident on the diffractive lens 147. Therefore, when the incident light L ′ is incident only on the upper right portion (in the figure) of the aperture 139a (FIG. 8A), the light spot S5 is the aperture 13
It is formed in the lower left part of the image 139b of 9a.

Further, the light spot S6 of the -1st-order diffracted light
Is an erect image of the intensity distribution of the light incident on the diffractive lens 147. Therefore, when the incident light L ′ is incident only on the upper right portion of the aperture 139a (FIG. 8B), the light spot S6 is formed on the upper right portion of the image 139b of the aperture.

As shown in FIG. 10, the light spots S5 and S6 are formed on the light receiving element 129 in a state where they are overlapped at the same time. As a result, the entire image 139b of the aperture is illuminated.

Therefore, it is proportional to the positional deviation between the center of the image 139b of the aperture and the center o of the light receiving element 29 (in other words, the optical axes of the aperture 139a and the light receiving element 129 and the optical axis of the incident light L '. The error signals TLEx and TLEy (which are proportional to the positional deviation of) are output from the error detection circuit.

Therefore, based on the output of this error signal,
The attitude of the light emitting / receiving unit 123 can be correctly controlled by servo-driving the rotating frame 127. More specifically, the optical axes of the aperture 139a and the light receiving element 129 and the optical axis of the incident light L'can be matched.

Further, as a result, the light emitted from the light emitting / receiving unit 123 can reach the base unit 121 (FIG. 1 (b)).

As described above, according to this embodiment, even if the incident light beam has a small beam diameter and part of the light beam is kicked by the aperture arranged in front of the light receiving element, The posture can be appropriately controlled based on. In other words, in bidirectional communication using a small-diameter parallel light beam, when the emission direction of the light beam is controlled according to the position between the light emitting and receiving units, the light intensity distribution within the light beam is detected when the incident angle of incident light is detected. It is possible to eliminate the detection error caused by the deviation and the kicking of the light beam, and to realize stable bidirectional communication.

FIG. 11 shows a modification of the first embodiment.

As shown in the figure, in this modification, instead of the condenser lens 131 and the diffraction lens 147, a compound lens 249 having a condenser lens surface 231 and a diffraction grating surface 247 is used. Here, the diffraction grating surface 247 has the function described above for the diffraction lens 147.

FIG. 12 shows another modification of the first embodiment.

In this modified example, as shown in FIG. 12A, a light emitting laser 233 corresponding to the light emitting laser 133 is provided.
Are provided within the surface of the light receiving element 229. More specifically,
As shown in FIG. 12B, the surface emitting laser 233 is provided at the center of the light receiving element 229.

With the above structure, the collimator lens 135 and the half mirror 137 shown in FIG. 6 can be omitted.

FIG. 13 shows a second embodiment of the light emitting / receiving unit of the present invention.

In this embodiment, the slave side light emitting / receiving unit 323 includes a fisheye lens 325, a biaxial rotating mirror 351, a compound lens 349, a light shielding portion 339, and a light emitting / receiving element 329 having a light emitting laser 333. And
The light blocking portion 339 includes an aperture 339a having the same structure and function as the apertures 39a and 139a.

Here, the fisheye lens 327 has the same structure as the fisheye lens 125 in FIG.
Has the same structure as the compound lens 249 in FIG. 11, and the light receiving and emitting element 329 is the light receiving and emitting element 22 in FIG.
It has the same structure as 9, 233.

By rotating the biaxial rotation mirror 351 along two axes, incident light that enters the slave unit 323 (for example, from the master unit) from any direction is incident on the light emitting / receiving element 329. Is reflected in the direction of.

The light emitting / receiving unit 323 also has an X direction (horizontal direction) angle deviation error signal based on the outputs from the divided areas a1, a2, b1, b2, c1, c2, d1 and d2, TLEx = (a1 + a2 + d1 + d2). -(B1 + b2
+ C1 + c2) X direction angle deviation error signal detection circuit (not shown) and Y direction (vertical direction) angle deviation error signal, TLEy = (a1 + a2 + b1 + b2)-(c1 + c2
+ D1 + d2) Y-direction angle deviation error signal detection circuit (not shown). Where a2, b1, b2, c1, c
2, d1 and d2 are light receiving areas a1, a2, b1 and b
2, c1, c2, d1 and d2 are output.

Further, the light receiving and emitting unit 323 outputs an information signal (or modulation signal, main signal), SIG = a2 + b2 + c2 + d2, based on the outputs from the light receiving areas a2, b2, c2, d2, and an information signal detecting circuit (see FIG. (Not shown).

Further, the light emitting / receiving unit 323 has a servo drive circuit (not shown) for servo-driving the biaxial rotation mirror 351 based on the output from each error detection circuit.

Therefore, the second embodiment also has the same effects as the first embodiment. That is, even when the incident light beam has a small beam diameter and a part of the light beam is kicked by the aperture 339a arranged in front of the light receiving element, the direction of the light receiving element can be adjusted with respect to the incident light. .

[0090]

According to the present invention, particularly in bidirectional communication using a small-diameter parallel light flux, when the emission direction of the light flux is controlled according to the position between the light emitting and receiving elements, the light flux within the light flux is detected when the incident angle of the incident light flux is detected. It is possible to eliminate the deviation of the light intensity distribution and the detection error caused by the vignetting of the light flux, and to realize stable bidirectional communication.

[Brief description of drawings]

FIG. 1 shows an example of a light emitting and receiving unit as a light emitting and receiving device used for optical communication such as a local optical wireless LAN.

FIG. 2 schematically shows a configuration of a child device side light emitting / receiving unit 23.

FIG. 3 shows a detailed configuration of a light receiving element 29.

FIG. 4 is an explanatory diagram showing an operation of the light emitting / receiving unit 23.

5A and 5B show an error in the angle control of the light beam L ′ emitted from the master side unit 21 to the slave side unit 23, and the light beam from the master side unit 21. L
A light spot and the like in the case where the'contour F'is not incident on the entire aperture 39a of the light shielding portion 39 are shown.

FIG. 6 shows a first embodiment of a light emitting / receiving unit of the present invention.

FIG. 7 shows the operation of the diffractive lens 147 provided in the first embodiment of the present invention.

FIGS. 8A and 8B show light spots of ± first-order diffracted light when a light beam L ′ that is misaligned with respect to the incident aperture 139a of the light emitting / receiving unit 123 is incident.

9A and 9B show the positional relationship between the light receiving areas a1 to d1 of the light receiving element 129 and the spots S5 and S6.

FIG. 10 shows a state in which light spots S5 and S6 are superimposed.

FIG. 11 shows a modified example of the first embodiment.

FIG. 12 shows another modification of the first embodiment.

FIG. 13 is a second view of the light emitting and receiving unit of the present invention.
An embodiment is shown.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G01J 1/04 G01J 1/06 Z 1/06 H04B 9/00 R H04B 10/00 A 10/105 10 / 22 F term (reference) 2F065 AA01 AA03 AA31 AA51 FF48 GG04 HH04 HH12 HH13 LL00 LL10 LL30 QQ13 2G065 AA17 AA18 AB09 BA03 BB02 BB06 BB14 BB15 BB49 BC31 BC35 DA13 5K002 AA01 AA07 FA03 FA03

Claims (6)

[Claims] 1. A photodetector for detecting an incident position or an incident angle of an incident light flux based on an incident position or an incident spot shape of the incident light flux, comprising a condensing means, a diffracting means, and a light receiving element. The condensing means, the diffracting means, and the light receiving element are arranged on the same optical axis, the diffracting means has substantially equal diffraction efficiency with respect to ± 1st-order diffracted light generated by diffraction, and the ± 1st order The light receiving element has a property of an approximately axisymmetric lens that imparts lens power to the ± 1st-order diffracted light so that both the folded lights are condensed on the optical axis. A photodetector arranged at a predetermined position on the optical axis where the beam diameters of the ± 1st-order diffracted lights substantially match in the middle. 2. The photodetector according to claim 1, wherein the intensity of the 0th-order diffracted light of the diffracting means is substantially zero. 3. The photodetector according to claim 1, wherein the light receiving element has an error signal detection area for detecting whether or not the light beam is applied to a predetermined position, and the light beam is incident on the predetermined position. And an information signal detecting area which is provided at the irradiation position of the light flux and has substantially the same extent as the irradiation area of the incident light flux. 4. A light emitting and receiving device for transmitting and receiving an optical information signal and detecting an incident position and an incident angle of an incident light beam from another light emitting and receiving device, the light emitting element, a light branching element, and a condensing means. And diffractive means,
A light receiving element, the condensing means, the diffracting means, and the light receiving element are arranged on a first optical axis, and a second optical axis defined by the light emitting element is separated from the first optical axis by the light branching element. The diffracting means has substantially the same diffraction efficiency with respect to the ± 1st-order diffracted light generated by diffraction, and the ± 1st-order diffracted light is focused so that both the ± 1st-order diffracted light are focused on the optical axis. On the optical axis, which has the property of an approximately axisymmetric lens that imparts a lens power, the light receiving element is such that the beam diameters of the ± 1st-order diffracted lights are substantially equal to each other in the middle of the focal point of the ± 1st-order diffracted lights. The light emitting and receiving device arranged at a predetermined position. 5. The light emitting and receiving device according to claim 4, wherein the 0th order diffracted light of the diffraction grating is set to substantially zero. 6. The light emitting and receiving device according to claim 4, wherein the light receiving element has an error signal detection area for detecting whether or not the light beam is applied to a predetermined position, and the light beam is incident on the predetermined position. And a light emitting / receiving device provided at an irradiation position of the light flux and having an information signal detection area having substantially the same extent as the irradiation area of the incident light flux.