JP4949989B2 - Optical space transmission module - Google Patents

Description

  The present invention relates to an optical space transmission module for transmitting an optical signal through a space as a medium.

  In recent years, optical space transmission technology using light waves instead of radio waves has begun to attract attention as a method for speeding up wireless transmission. In addition to high speed using the broadband property, the light wave has security by straightness / light shielding. A light source diode (LED) or a semiconductor laser diode (LD) is used as a light source used for this spatial light transmission, and an LD capable of high-speed modulation is advantageous for improving the transmission speed.

  However, the LD has a light source size smaller than that of the LED and has high coherence of output light. For this reason, when the output light of the LD is emitted into the space as it is, if the light beam stops and enters the eye, a high energy density image is formed on the retina, and the retina may be damaged. In order to obtain the same safety as an LED with an LD, the light output intensity is reduced, or the coherence of the output light is reduced using an optical component such as a diffusion plate, and then the virtual secondary light source size is reduced. Must be expanded. In the latter case, the size of the image formed on the retina depends on the secondary light source size. In order to obtain a larger light output while maintaining the safety of the optical transmitter, the secondary light source size may be increased. As an optical system for ensuring the safety of such a laser, for example, there is an optical transmitter disclosed in Patent Document 1. FIG. 10 is a schematic diagram illustrating an example of a configuration of a conventional optical transmitter disclosed in Patent Document 1. In FIG.

In FIG. 10, the conventional optical transmitter includes a laser 900, a condenser lens 910, a lens 920, a reflection type diffusing unit 921, a reflecting unit 922, an opening 923, and a light receiving unit 930. The condensing lens 910 condenses the laser beam A output from the laser 900 and irradiates the reflection type diffusing unit 921 through the opening 923. The reflection type diffusing unit 921 converts the irradiated laser beam A into diffused light B and reflects it. The reflector 922 reflects the diffused light B. The lens 920 distributes the diffused light B reflected by the reflecting unit 922 in a certain direction and outputs it as transmission light C. The light receiving unit 930 receives the signal light output from the facing optical transmitter. In this conventional optical transmitter, the coherence of the laser beam A is disturbed by the reflective diffuser 921, and a virtual secondary light source having a Lambertian distribution is formed on the reflective diffuser 921. Therefore, it is possible to improve safety as compared to using the laser alone.
JP 2004-165957 A

  However, in the conventional optical transmitter, since the laser beam A is directly applied to the reflection type diffusing unit 921, the reflected diffused light B returns to the laser 900, and the return light may cause unstable operation of the laser 900. There is. In addition, since the conventional optical transmitter uses a reflection mechanism, the thickness can be reduced, but the diameter of the reflection portion 922 is increased, and the total occupied area including the light receiving portion 930 is increased. There are also challenges.

  Therefore, the present invention solves the above-described conventional problems, and relaxes the upper limit value of the light output based on the safety standard of the laser, reduces the return light to the laser, and can be downsized. An object is to provide a spatial transmission module.

  The present invention is directed to an optical space transmission module for transmitting an optical signal through a space as a medium. In the first aspect, the space optical transmission module converts the transmission light reflected by the reflection unit into a diffused light by reflecting a light emitting unit that outputs the transmission light, a pedestal unit having a reflection unit that reflects the transmission light, and reflecting And a reflective diffusion part. The reflection unit has a function of expanding the beam diameter after reflection of the transmission light.

  According to the first aspect, the secondary light source having a larger diameter can be made by expanding the beam diameter of the transmitted light at the reflecting portion and then converting the light to diffused light, which is based on laser safety standards. The upper limit of light output can be relaxed.

  In the second aspect, the reflecting portion is a convex mirror.

  According to the second aspect, by setting the inclination angle in the convex cross section to a certain value or more, there is an effect of preventing the transmission light from returning to the light emitting section again after being reflected by the reflecting section.

  In the third aspect, the reflecting portion is configured by a Fresnel mirror having a function equivalent to that of a convex mirror.

  According to the said 3rd aspect, the thickness of a reflection part can be made thin by using a Fresnel mirror.

  In the fourth aspect, the reflective diffusing portion has a concave shape.

  According to the fourth aspect, the directivity angle of the diffused light output from the optical space transmission module is controlled by controlling the inclination angle or the curvature of the cross section of the reflective diffusing section, and the transmitted light is efficiently transmitted. Can do.

  In the fifth aspect, the optical space transmission module further includes a light receiving unit that receives an optical signal, and the light receiving unit is disposed on a different surface from the reflection unit included in the pedestal unit.

  According to the fifth aspect, by arranging the light receiving unit on a surface different from the reflecting unit of the pedestal unit, the entire transmitter / receiver can be reduced in size by integrating the light receiving unit with the transmitter.

  In the sixth aspect, the optical space transmission module further includes a lens unit disposed so as to cover the reflective diffusion unit.

  According to the sixth aspect, the directional angle of the diffused light can be controlled by condensing the diffused light at the lens unit, and the transmitted light can be transmitted efficiently.

  In the seventh aspect, the lens unit includes a plurality of lens regions, and the plurality of lens regions includes a first lens region that distributes at least diffused light, and a second lens that condenses the optical signal to the light receiving unit. And a lens region.

  According to the seventh aspect, the first lens region and the second lens region are separated, and the light signal is more efficiently collected on the light receiving unit by optimizing the light collection characteristics in each region. can do.

  In the eighth aspect, the lens unit is composed of a Fresnel lens.

  According to the eighth aspect, the thickness of the optical system can be reduced.

  In the ninth aspect, the reflecting portion is located between the light emitting portion and the light receiving portion, and the reflecting portion, the light emitting portion, and the light receiving portion are arranged on a substantially straight line.

  According to the ninth aspect, after being output from the light emitting unit, it is possible to prevent light reflected by the reflecting unit from being directly coupled to the light receiving unit.

  In the tenth aspect, the light emitting unit is configured by a semiconductor laser.

  According to the tenth aspect, high-speed modulation is possible.

In the eleventh aspect, the reflecting section has a specific inclination angle α with respect to a plane perpendicular to the light beam vertically emitted around the light beam vertically emitted from the light emitting section, and is reflected from the light emitting section and the light reflecting portion. When the distance between the light emitting portions is D and the light emitting region diameter of the light emitting portion is φ, the specific inclination angle α is set so as to satisfy the relationship of Expression (1).
D · tan (2α)> φ / 2 ··· Formula (1)

  According to the eleventh aspect, it is possible to reduce coupling of light rays emitted vertically from the light emitting portion to the light emitting region after being reflected by the reflecting portion.

  As described above, according to the optical space transmission module according to the present invention, the beam diameter of the transmission light output from the light emitting unit is expanded by the reflecting unit, and then converted into diffused light by the reflective diffusing unit. A secondary light source having a large size can be produced, and the upper limit value of the light output based on the safety standard of the laser can be relaxed. Furthermore, the amount of light returning from the reflecting unit to the light emitting unit can be reduced by reflecting the transmitted light in a direction other than the light emitting unit at the reflecting unit and then diffusing. Moreover, by arranging the light receiving portion on the pedestal portion having the reflecting portion, the light receiving and emitting portions can be integrated, and the size can be reduced.

(First embodiment)
Hereinafter, an optical space transmission module according to a first embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing an example of a configuration of an optical space transmission module according to the first embodiment of the present invention. In FIG. 1, the optical space transmission module includes a light emitting unit 100, a pedestal unit 110, a reflection unit 111, and a reflection type diffusion unit 120. The light emitting unit 100 outputs transmission light A that is modulated in accordance with a signal input to the light emitting unit 100. The reflecting portion 111 is a convex mirror provided on a part of the pedestal portion 110 so as to face the light emitting portion 100, and specifically has a conical shape. The reflection unit 111 reflects the transmission light A so that the beam diameter of the transmission light A widens. The reflective diffuser 120 having a concave shape converts the reflected light B reflected by the reflector 111 into diffused light C and reflects it.

  Here, the relationship between the shape of the reflecting portion 111 of the present invention and the reflected light B will be described using FIGS. 2A to 2B and FIGS. 3A to 3B while comparing with the conventional method. FIG. 2A is a diagram illustrating a relationship between the shape of the reflective diffusion portion 921 and the reflected light B in the conventional method described in Patent Document 1. FIG. 2B is a diagram showing a relationship between the shape of the reflection type diffusing unit 921 and the reflected light B when the lens 150 in the conventional method is not provided for comparison with the present invention. FIG. 3A is a diagram showing the relationship between the shape of the reflecting portion 111 and the reflected light B in the first embodiment of the present invention. FIG. 3B is a diagram showing the relationship between the shape of the reflecting portion 111 and the reflected light B when the lens 150 according to the first embodiment of the present invention is provided for comparison with the conventional method. 2A and 2B and FIGS. 3A and 3B, the light emitting unit 100 is configured to include a laser light source that outputs the transmission light A at a radiation angle θ. The reflection unit 111 has a conical mirror with an inclination angle α.

  The conventional method in FIG. 2A is a method in which the transmission light A output from the light emitting unit 100 is condensed by the lens 150 and then diffused by the opposing reflective diffusion unit 921. 2B is a method in which the transmission light A output from the light emitting unit 100 is diffused by the reflection type diffusion unit 921 that directly faces. In these methods, since the transmission light A is diffused and reflected at a wide angle range by the reflection-type diffusing unit 921 located at the position facing the light emitting unit 100, a part of the diffused light B returns to the light emitting unit 100. There is a problem that.

  On the other hand, in the present invention shown in FIG. 3A, the reflected light B tilted by 2α with respect to the incident angle can be obtained even with the transmission light A output almost vertically from the light emitting unit 100. When the distance between the light emitting unit 100 and the reflecting unit 111 is D, the reflected light B reaches a position away from the light emitting unit 100 by D × tan 2α. For this reason, it is possible to significantly reduce the amount of light returning to the light emitting unit 100 (hereinafter referred to as return light amount) more than the conventional method in which the reflection type diffusing unit 921 is directly irradiated with laser light. In addition, a large diffused light source (secondary light source) can be produced, and the upper limit value of the light output based on the safety standard of the laser can be relaxed. Further, even when the lens 150 is provided as shown in FIG. 3B, the amount of light returning to the light emitting unit 100 can be reduced by setting the inclination angle α to a certain level or more.

  Next, FIG. 4 and FIG. 5 show an example of the result of calculating the return light ratio between the conventional method and the present invention. Here, the return light ratio indicates a ratio at which the transmission light A output from the light emitting unit 100 is reflected and diffused and reaches the light emitting region. That is, the return light ratio = return light quantity / transmission light quantity. FIG. 4 is a diagram showing a calculation result of the return light ratio between the present invention shown in FIG. 3A and the conventional method shown in FIG. 2B. That is, FIG. 4 is a diagram showing the calculation results of the return light ratio between the present invention and the conventional method when the lenses 150 are not provided. In FIG. 4, the inclination angle α of the reflecting part 111 is a variable parameter, the emission angle θ of the light emitting part 100 is 20 degrees, the size of the light emitting area of the light emitting part 100 is 80 μmφ, and the distance D between the light emitting part 100 and the reflecting part 111 is The calculation was performed on the assumption that the 0.5 mm reflection type diffusion unit 921 performs Lambert diffusion.

  FIG. 5 is a diagram showing a calculation result of the return light ratio between the present invention shown in FIG. 3B and the conventional method shown in FIG. 2A. That is, FIG. 5 is a diagram showing a calculation result of the return light ratio between the present invention and the conventional method when the lenses 150 are provided. In FIG. 5, the inclination angle α of the reflecting portion 111 is a variable parameter, the emission angle θ of the light emitting portion 100 is 20 degrees, the lens 150 is a biconvex lens with a focal length of 1.6 mm, and the size of the light emitting region of the light emitting portion 100 is 20 μmφ, The reflection-type diffusing unit 921 is calculated assuming that Lambertian diffusion is performed.

  Referring to FIG. 4, the conventional method has a return light ratio of about −17 dB, but in the present invention, by setting the inclination angle α to a certain value or more (in this calculation condition, 2.4 deg or more), It can be seen that the return light ratio can be reduced to -30 dB or less. Referring to FIG. 5, the conventional method has a return light ratio of about −17 dB, but in the present invention, the inclination angle α is set to a certain value or more (in this calculation condition, 10 deg or more), It can be seen that the return light ratio can be reduced to -30 dB or less.

Here, the calculation method of the inclination angle α of the reflection unit 111 will be described in more detail with reference to FIG. FIG. 6 shows the relationship between the inclination angle α of the reflecting part 111, the distance D between the light emitting part 100 and the reflecting part 111, and the light emitting region diameter φ of the light emitting part 100. Referring to FIG. 6, among the light beams output from light emitting unit 100, the light beam emitted vertically (radiation angle 0 °) is generally high in intensity and has a great influence when returning to the light emitting region. Therefore, in order to reduce the coupling to the light emitting region after the light beam having the radiation angle of 0 ° is reflected by the reflecting portion 111, it is desirable to set the inclination angle α so as to satisfy the relationship of Expression (1).
D · tan (2α)> φ / 2 ··· Formula (1)

  As described above, according to the optical space transmission module according to the first embodiment of the present invention, the beam diameter of the transmission light A is expanded by the reflection unit 111 and then converted into the scattered light C by the reflection type diffusion unit 120. Thus, a secondary light source having a larger size can be produced, and the upper limit value of the light output based on the safety standard of the laser can be relaxed. Furthermore, the amount of light returning from the reflecting unit 111 to the light emitting unit 100 can be reduced by reflecting the transmission light A in a direction other than the light emitting unit 100 by the reflecting unit 111 and then diffusing it.

  Further, by making the convex mirror of the reflecting portion 111 larger than the beam diameter of the transmission light A, all the transmission light A can be reflected, which is efficient. Further, when a condensing lens (for example, the lens 150) is used between the light emitting unit 100 and the reflecting unit 111 and the beam diameter of the transmission light A is collimated or condensed, the convex mirror of the reflecting unit 111 is formed. The size can be reduced as compared with the case where there is no condenser lens.

  In this embodiment, the conical shape is shown as an example of the convex shape mirror. However, the shape is not limited to this shape. If the reflected light in the direction of the light emitting unit 100 can be reduced, a spherical shape or an aspherical shape is used. But you can.

(Second Embodiment)
Hereinafter, an optical space transmission module according to a second embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 7 is a schematic diagram showing an example of the configuration of an optical space transmission module according to the second embodiment of the present invention. Referring to FIG. 7, the optical space transmission module according to the second embodiment has a configuration in which a lens unit 130 and a light receiving unit 140 are added as compared with the first embodiment. Here, the same components as those in the first embodiment of the present invention are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 7, the lens unit 130 has a plurality of lens regions. Specifically, the lens unit 130 includes a first lens region 131 that distributes the diffused light and a second lens region 132 that condenses the light beam on the light receiving unit 140. The lens unit 130 is disposed so as to cover the reflective diffusion unit 120. The light receiving unit 140 is disposed on a different surface from the reflecting unit 111 of the pedestal unit 110.

  Since the reflecting portion 111 provided on the pedestal portion 110 is disposed so as to face the light emitting portion 100, a space is generated on the back surface of the reflecting portion 111. In view of this, it is possible to form a module in which the light receiving and emitting portions are integrated by using the space on the back surface of the reflecting portion 111 that is not normally used and arranging the light receiving portion 140 there. Further, the light receiving unit 140 is arranged so that the reflecting unit 111 is positioned between the light emitting unit 100 and the light receiving unit 140, and the three components are arranged on a substantially straight line, thereby devising the light emitting unit. It is possible to avoid the transmission light A output from 100 from being coupled to the light receiving unit 140.

  Further, by providing the lens unit 130 with the first lens region 131 and the second lens region 132, an optimum lens shape can be designed for each region, and the light distribution characteristics of the diffused light and the light receiving unit The light condensing characteristic to 140 can be improved.

  As described above, according to the optical space transmission module according to the second embodiment of the present invention, in addition to the effects described in the first embodiment, the light receiving unit 140 and the reflecting unit 111 provided on the pedestal unit 110 and By arranging them on different planes, transmission and reception can be integrated, and the entire transceiver can be miniaturized. Further, by providing the lens unit 130 with the first lens region 131 that distributes the diffused light and the second lens region 132 that collects the light beam on the light receiving unit 140, the light distribution characteristic of the diffused light Condensing characteristics to the light receiving unit 140 can be improved.

(Third embodiment)
Hereinafter, an optical space transmission module according to a third embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 8 is a schematic diagram showing an example of an optical space transmission module configuration according to the third embodiment of the present invention. In FIG. 8, the optical space transmission module is obtained by realizing the reflection unit 211 and the lens unit 230 with different configurations as compared with the second embodiment. Here, the same components as those of the second embodiment of the present invention are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 8, the reflection unit 211 is composed of a Fresnel mirror having the same function as a convex mirror provided so as to correspond to the light emitting unit 100. The lens unit 230 is configured by a Fresnel lens having a plurality of lens regions. Specifically, the lens unit 230 includes a first Fresnel lens region 231 that distributes diffused light, and a second Fresnel lens region 232 that collects light rays on the light receiving unit 140.

  As described above, according to the optical space transmission module according to the third embodiment of the present invention, in addition to the effects described in the second embodiment, the reflection unit 211 is a Fresnel mirror and the lens unit 230 is a Fresnel lens. By configuring, the entire optical space transmission module can be reduced in weight and thickness by reducing the weight and thickness of the lens unit 230 and reducing the weight of the reflection unit 211.

(Fourth embodiment)
Hereinafter, an optical space transmission module according to a fourth embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 9 is a schematic diagram showing an example of a configuration of an optical space transmission module according to the fourth embodiment of the present invention. In FIG. 9, the optical space transmission module is realized by configuring the reflection type diffusing unit 320 and the lens unit 330 in different configurations as compared with the third embodiment. Here, the same components as those of the third embodiment of the present invention are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 9, the lens part 330 is comprised with the resin mold which accommodates the light-receiving part 140 and the base part 110, and has a some lens area | region on the surface. Specifically, the lens unit 330 includes a first Fresnel lens region 331 that distributes diffused light, and a second Fresnel lens region 332 that collects light rays on the light receiving unit 140. The lens portion 330 is provided with a convex opening 333. The reflective diffusing unit 320 is formed on the curved side surface of the lens unit 330. Here, the transmission light output from the light emitting unit 100 is incident on the reflection unit 211 after entering from the opening 333.

  The first Fresnel lens region 331, the second Fresnel lens region 332, and the opening 333 are created at the same time as the lens unit 330 by creating a shape in advance on a mold for creating the lens unit 330. Can do. The reflection type diffusing unit 320 can be created by applying a white paint after the curved side surface of the lens unit 330 is sanded.

  Since the opening 333 has a convex shape, it has the effect of a condensing lens, and the beam diameter irradiated to the reflecting part 211 can be reduced. Therefore, the processing area of the reflection part 211 can be reduced, and the processing cost and processing time of the reflection part 211 can be shortened.

  As described above, according to the optical space transmission module according to the fourth embodiment of the present invention, the first Fresnel lens region 331, the second Fresnel lens region 332, the reflection type diffusion are formed simultaneously with the creation of the lens unit 330. Since components such as the section 320 and the opening 333 can also be created, the number of parts and man-hours of the optical space transmission module can be reduced, and the cost of the module can be expected to be reduced.

  Note that the side surface of the lens unit 330 is not limited to the curved structure as shown in FIG. 9, but may be an inverted conical structure. The lens unit 330 is not limited to a Fresnel lens, and may be a convex lens. The opening 333 is not limited to a convex shape, and may be a Fresnel lens.

  The optical space transmission module according to the present invention can realize an eye-safe laser light source and integration of a light emitting / receiving module with a simple configuration, and is useful as a configuration for achieving safety and miniaturization of the optical space transmission system.

  Although the present invention has been described in detail above, the above description is merely illustrative of the present invention in all respects and is not intended to limit the scope thereof. It goes without saying that various improvements and modifications can be made without departing from the scope of the present invention.

1 is a schematic diagram showing an example of a configuration of an optical space transmission module according to a first embodiment of the present invention. The figure which shows the relationship between the shape of the reflection-type spreading | diffusion part 921 and the reflected light B in a conventional system. The figure which shows the relationship between the shape of the reflection-type spreading | diffusion part 921 when not providing the lens 150 in a conventional system, and the reflected light B The figure which shows the relationship between the shape of the reflection part 111 and the reflected light B in the 1st Embodiment of this invention. The figure which shows the relationship between the shape of the reflection part 111 at the time of providing the lens 150 in the 1st Embodiment of this invention, and the reflected light B The figure which shows the calculation result of the return light ratio of this invention shown to FIG. 3A, and the conventional system shown to FIG. 2B The figure which shows the calculation result of the return light ratio of this invention shown to FIG. 3B, and the conventional system shown to FIG. 2A The figure explaining the calculation method of inclination-angle (alpha) of the reflection part 111 The schematic diagram which shows an example of a structure of the optical space transmission module which concerns on the 2nd Embodiment of this invention. The schematic diagram which shows an example of the space optical transmission module structure which concerns on the 3rd Embodiment of this invention. The schematic diagram which shows an example of the space optical transmission module structure which concerns on the 4th Embodiment of this invention. Schematic diagram showing an example of the configuration of a conventional optical transmitter

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Light emission part 110 Base part 111, 211 Reflection part 120, 320 Reflection type diffuser part 130, 230, 330 Lens part 131 1st lens area 132 2nd lens area 231, 331 1st Fresnel lens area 232, 332 1st 2 Fresnel lens region 140, light receiving unit 150 lens 333 opening 900 laser 910 condenser lens 920 lens 921 reflection type diffusion unit 922 reflection unit 923 opening 930 light receiving unit

Claims (7)

An optical space transmission module that transmits an optical signal to space through a medium,
A light emitting unit for outputting transmission light;
A pedestal having a reflecting part for reflecting the transmitted light;
A reflective diffusion unit that converts the transmission light reflected by the reflection unit into diffused light and reflects it; and
A lens unit arranged to cover the reflective diffusion unit;
A light receiving portion for receiving an optical signal,
The reflection unit has a convex mirror that enlarges the beam diameter after reflection of the transmission light,
The light receiving portion is disposed on a different surface from the reflecting portion of the pedestal portion ,
The lens unit has a plurality of lens regions,
Wherein the plurality of lens regions is characterized Rukoto that Yusuke a first lens region which light distribution at least the diffused light, and a second lens region for focusing the optical signal to the light receiving portion, the light space Transmission module.   2. The optical space transmission module according to claim 1, wherein the reflection unit is configured by a Fresnel mirror having a function equivalent to that of a convex mirror.   The optical space transmission module according to claim 1, wherein the reflection-type diffusion unit has a concave shape. The optical space transmission module according to claim 1 , wherein the lens unit is configured by a Fresnel lens. The reflecting portion is located between the light emitting portion and the light receiving portion,
The optical space transmission module according to claim 1, wherein the reflection unit, the light emitting unit, and the light receiving unit are arranged on a substantially straight line.   The optical space transmission module according to claim 1, wherein the light emitting unit is a semiconductor laser. The reflecting portion has a specific inclination angle α with respect to a plane perpendicular to the optical axis of the light beam, with the optical axis of the light beam emitted perpendicularly from the light emitting portion as the center,
When the distance between the light emitting part and the reflecting part is D and the light emitting region diameter of the light emitting part is φ, the specific inclination angle α is set so as to satisfy the relationship of Expression (1). The optical space transmission module according to claim 1, wherein the optical space transmission module is characterized.
D · tan (2α)> φ / 2 ··· Formula (1)

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