JP2019186595A - Photoreceiver for optical communication device - Google Patents

Abstract

To provide a photoreceiver for an optical communication device that can condense light and perform filtering for an intended wavelength.SOLUTION: A photoreceiver includes: a condenser lens 3 for condensing incident light; a collimator lens 4 that has a focal length shorter than the focal length of the condenser lens 3 and converts the light from the condenser lens 3 into parallel light; a bandpass filter 5 that causes the parallel light from the collimator lens 4 to enter a filter surface 5a perpendicularly and transmits only the wavelength of the incident light; and a photodetector element 6 for detecting the light transmitted by the bandpass filter 5.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light receiving device of an optical communication device that performs communication between points separated by an optical signal.

  The optical communication device includes a light source disposed on the transmission side and a light receiving unit disposed on the reception side so as to be separated from the light source. According to this optical communication device, communication between the transmission side and the reception side is performed when the light receiving unit receives the modulated optical signal from the light source.

  For example, the optical communication device described in Patent Document 1 converts laser light from a semiconductor laser, which is a light source, into parallel light by a collimator lens and sends an optical signal to space. The transmitted optical signal is received by the light receiving unit through the condenser lens and the band pass filter.

  Furthermore, underwater optical wireless communication technology is known. Patent Document 2 discloses an underwater communication system that performs transmission and reception of various data between underwater devices using optical signals. Patent Literature 3 discloses an underwater visible light communication system that transmits observation data to an underwater moving body from an observation device installed underwater using visible light communication.

The light receiving technology of optical wireless communication has the following three problems.
(1) As the distance between the light source and the light receiving portion increases, the light is absorbed and diffused by fine particles in the air and water, water and rain, and the amount of light is attenuated. (2) Further, since the light receiving container is used in water or in the sea where high water pressure is applied, the light receiving container window cannot be enlarged. (3) Furthermore, since optical noise such as sunlight greatly affects the optical signal reception sensitivity, noise removal is necessary.

  (1) For the problem of (2), it is effective to use a condensing lens because the limited light transmitted through the window of the light receiving container can be effectively condensed on the light receiving part. For the problem (3), it is effective to use a band-pass filter that transmits only the wavelength used for optical communication.

  In order to take advantage of the single wavelength property of laser light, it is effective to use a filter that transmits only a narrow wavelength width. For this reason, a dielectric multilayer filter is used for the narrow band-pass filter. In Patent Document 1, a condensing lens and a bandpass filter are used to solve the above three problems.

Japanese Patent Laid-Open No. 07-177090 JP 2009-55408 A JP 2009-278455 A

  However, when a bandpass filter using a dielectric multilayer filter is used, there is an angle dependency of the dielectric multilayer filter. As described in Patent Document 1, when a band-pass filter is disposed after the condenser lens, the angle dependency of the dielectric multilayer film filter is generated depending on the condensing angle. That is, light from the center of the condenser lens is incident on the bandpass filter perpendicularly, but light from other than the center of the condenser lens is not incident on the bandpass filter perpendicularly. For this reason, there has been a problem that filtering cannot be performed with respect to the intended wavelength.

  The subject of this invention provides the light-receiving device of the optical communication apparatus which can condense light and can perform filtering with respect to the intended wavelength.

  In order to solve the above problems, a light receiving device of an optical communication device according to the present invention has a first condensing lens that condenses incident light and a focal length shorter than the focal length of the first condensing lens. A collimating lens that converts the light from the first condenser lens into parallel light, and a bandpass filter that allows the parallel light from the collimating lens to enter the filter surface perpendicularly and transmit only the wavelength of the incident light. And a light receiving element for detecting light transmitted by the band pass filter.

  The light receiving device of the optical communication device according to the present invention includes a concave lens that converts incident light into parallel light, and makes the parallel light from the concave lens incident perpendicularly to the filter surface and transmits only the wavelength of the incident light. A bandpass filter to be collected; a condenser lens that condenses the light transmitted by the bandpass filter; and a light receiving element that detects the light collected by the condenser lens.

  According to the present invention, the light from the first condenser lens is converted into parallel light by the collimating lens, and the parallel light from the collimating lens is vertically incident on the bandpass filter. Can be filtered.

  In addition, since the incident light is converted into parallel light by the concave lens and the parallel light from the concave lens is vertically incident on the bandpass filter, the light can be collected and filtering for the intended wavelength can be performed.

It is a block diagram of the light-receiving device of the optical communication apparatus of Example 1 of this invention. It is a block diagram of the light-receiving device of the optical communication apparatus of Example 2 of this invention. It is a block diagram of the light-receiving device of the optical communication apparatus of Example 3 of this invention. It is a block diagram of the light-receiving device of the optical communication apparatus of Example 4 of this invention. It is a block diagram of the light-receiving device of the optical communication apparatus of Example 5 of this invention. It is a block diagram of the light-receiving device of the optical communication apparatus of Example 6 of this invention. It is a block diagram of the light-receiving device of the optical communication apparatus of Example 7 of this invention.

Example 1
Hereinafter, a light receiving device of an optical communication device according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of a light receiving device of an optical communication device according to a first embodiment of the present invention. The light receiving device of the optical communication device according to the first embodiment illustrated in FIG. 1 includes a light receiving container 1 that receives incident light 11. Incident light 11 is signal light emitted from a light source such as a semiconductor laser (not shown). It is assumed that it does not enter at a certain angle through underwater propagation.

  The light receiving container 1 is formed of a cylindrical body made of aluminum or the like that is long in the lateral direction (horizontal direction), and an optical window 2 for entering incident light 11 is formed on the left side surface of the cylindrical body. The optical window 2 is made of glass, acrylic or the like.

  In the cylindrical body of the light receiving container 1, a condenser lens 3, a collimating lens 4, a band pass filter 5, and a light receiving element 6 are arranged. The optical window 2, the condenser lens 3, the collimator lens 4, the band pass filter 5, and the light receiving element 6 are disposed on the optical axis of the incident light 11.

  The condensing lens 3 corresponds to the first condensing lens of the present invention, is composed of a convex lens having a first focal length, etc., is disposed in the vicinity of the optical window 2, and receives incident light 11 incident from the optical window 2. Condensed to one focal length. The condensed light beam is a light beam 12.

  The collimating lens 4 has a second focal length shorter than the first focal length of the condenser lens 3, and converts the divergent light after being condensed at the first focal length by the condenser lens 3 into parallel light.

  The bandpass filter 5 is a bandpass filter that allows only a predetermined frequency band to pass therethrough, and is formed of, for example, a dielectric multilayer filter and has an angle dependency. The bandpass filter 5 allows the parallel light from the collimating lens 4 to enter perpendicularly to the filter surface 5a and transmit only the wavelength of the incident light 11.

  The light receiving element 6 is, for example, a photodiode and detects light transmitted by the band pass filter 5.

  The condensing lens 3 and the collimating lens 4 may be arranged outside the light receiving container 1 and the optical window 2.

  As described above, according to the light receiving device of the optical communication device of the first embodiment, the incident light 11 passes through the optical window 2 and is condensed at the first focal length by the condenser lens 3. Furthermore, the collimating lens 4 converts the light from the condensing lens 3 into parallel light, and the parallel light from the collimating lens 4 is vertically incident on the surface 5a of the bandpass filter 5, thereby effectively filtering the limited light. To the light receiving element 6.

  That is, both the light from the center of the collimating lens 4 and the light from other than the center are parallel light, and are incident perpendicularly on the surface 5 a of the bandpass filter 5. For this reason, the angle dependency of the dielectric multilayer filter caused by the light collection angle can be eliminated. Therefore, light can be collected and filtering for the intended wavelength can be performed.

(Example 2)
FIG. 2 is a configuration diagram of a light receiving device of the optical communication device according to the second embodiment of the present invention. The light receiving device of the optical communication device according to the second embodiment is different from the light receiving device of the optical communication device according to the first embodiment shown in FIG. The optical lens 7 is arranged.

  The condensing lens 7 corresponds to the second condensing lens of the present invention, and is composed of a convex lens or the like. The condensing lens 7 condenses the light transmitted by the band pass filter 5 and guides it to the light receiving element 6.

  As described above, according to the light receiving device of the optical communication device of the second embodiment, when the parallel light transmitted through the collimator lens 4 is larger than the light receiving surface of the light receiving element 6, the light once transmitted through the band pass filter 5. Is condensed by the condenser lens 7 and guided to the light receiving element 6. Accordingly, the limited light can be effectively detected by the light receiving element 6.

(Example 3)
FIG. 3 is a configuration diagram of a light receiving device of the optical communication device according to the third embodiment of the present invention. The light receiving device of the optical communication device of Example 3 shown in FIG. 3 is further different from the light receiving device of the optical communication device of Example 1 shown in FIG. And an aperture 8 disposed at the focal position of the condenser lens 3.

  The aperture 8 has an opening 8a, passes only the light collected at the focal position of the condenser lens 3 through the opening 8a, and blocks light that is not condensed at the focal position of the condenser lens 3.

  When the angular dispersion of incident light is large, the light may not be sufficiently collected by the condensing lens 3, and the collimating lens 4 may not be able to convert the light into parallel light.

  Further, in order to filter only a desired wavelength by the bandpass filter 5, it is necessary to make the light incident perpendicularly on the surface 5 a of the bandpass filter 5. For this reason, the aperture 8 is arranged between the condenser lens 3 and the collimating lens 4.

  Since the aperture 8 is disposed at the focal position of the condenser lens 3 and the incident angle to the condenser lens 3 such as stray light is greatly deviated, the light that is not condensed at the focal position of the condenser lens 3 8 is guided to the portion other than the opening 8 a of the 8, and is blocked by the aperture 8.

  On the other hand, the light condensed at the focal position of the condensing lens 3 and transmitted through the opening 8a of the aperture 8 becomes parallel light by the collimating lens 4, and this parallel light is perpendicular to the surface 5a of the bandpass filter 5. Is incident on.

  That is, even when the angular dispersion of incident light is large, the aperture 8 can be used to collect light at the focal position of the condensing lens 3, so that the collimating lens 4 can convert the light into parallel light, and the parallel light is converted into a bandpass filter. 5 can be perpendicularly incident on the surface 5a. Therefore, the same effect as that of the light receiving device of the optical communication device of the first embodiment can be obtained.

  In addition, you may combine the light-receiving device of the optical communication apparatus of Example 2, and the light-receiving device of the optical communication apparatus of Example 3. With this configuration, it is possible to obtain the effect of the light receiving device of the optical communication apparatus according to the second embodiment and the effect of the light receiving device of the optical communication apparatus according to the third embodiment.

Example 4
FIG. 4 is a configuration diagram of a light receiving device of the optical communication device according to the fourth embodiment of the present invention. In the light receiving device of the optical communication apparatus of Example 4 shown in FIG. 4, the light receiving container 1 c includes a concave lens 9, a band pass filter 5, a condenser lens 3, and a light receiving element 6. The concave lens 9, the band pass filter 5, the condenser lens 3, and the light receiving element 6 are disposed on the optical axis of the incident light 11 and on the central axis O of the light receiving container 1c.

  The concave lens 9 is disposed in the vicinity of the optical window 2 and converts incident light 11 incident from the optical window 2 into parallel light. The bandpass filter 5 allows the parallel light from the concave lens 9 to enter perpendicularly to the filter surface 5 a and transmits only the wavelength of the incident light 11.

  The condensing lens 3 condenses the light transmitted by the band pass filter 5. The light receiving element 6 detects the light collected by the condenser lens 3.

  As described above, in the light receiving device of the optical communication device of Example 1-3, the incident light 11 is converted into parallel light using the condenser lens 3 and the collimating lens 4, but the light receiving device of the optical communication device of Example 4 is used. Accordingly, when the incident light 11 is incident on the central axis O of the light receiving container 1c at a large angle, for example, 60 °, the incident light 11 can be converted into parallel light by the concave lens 9 at a time. For this reason, the optical system can be simplified. This is particularly effective when the incident light 11 is incident at a large angle with respect to the central axis O of the light receiving container 1c.

(Example 5)
FIG. 5 is a configuration diagram of a light receiving device of the optical communication device according to the fifth embodiment of the present invention. The light receiving device of the optical communication device of Example 5 shown in FIG. 5 has a configuration of the light receiving device of the optical communication device of Example 1 shown in FIG. 1, a holder 21 that covers the collimating lens 4, and one end of the holder 21. A bar 22 connected to each other and an XYZ stage 23 connected to the other end of the bar 22 are provided. The holder 21, the rod 22 and the XYZ stage 23 are provided in the light receiving container 1.

  The XYZ stage 23 corresponds to the movement mechanism of the present invention, and is driven by a control signal from the outside of the light receiving container 1 to move the collimating lens 4 in the holder 21 via the rod body 22 in the X-axis direction (left-right direction) and Y It is moved in three axial directions, ie, an axial direction (vertical direction) and a Z-axis direction (front-rear direction).

  Therefore, by driving the XYZ stage 23, the collimating lens 4 can be adjusted to an optimal position according to the light incident angle.

(Example 6)
FIG. 6 is a configuration diagram of the light receiving device of the optical communication device according to the sixth embodiment of the present invention. The light receiving device of the optical communication device of Example 6 shown in FIG. 6 has a structure of the light receiving device of the optical communication device of Example 2 shown in FIG. And an XYZ stage 23 connected to the other end of the rod 22. The holder 21, the rod 22 and the XYZ stage 23 are provided in the light receiving container 1.

  The XYZ stage 23 corresponds to the moving mechanism of the present invention, and is driven by a control signal from the outside of the light receiving container 1 to move the condenser lens 7 in the holder 21 via the rod body 22 in the X-axis direction (left-right direction). It is moved in three axial directions, ie, the Y-axis direction (vertical direction) and the Z-axis direction (front-rear direction).

  Therefore, by driving the XYZ stage 23, the condenser lens 7 can be adjusted to an optimum position in accordance with the light incident angle.

  The light receiving device of the optical communication apparatus according to the sixth embodiment and the light receiving device of the optical communication apparatus according to the fifth embodiment may be used in combination. If comprised in this way, the effect of the light-receiving device of the optical communication apparatus of Example 6 and the effect of the light-receiving device of the optical communication apparatus of Example 5 can be acquired.

(Example 7)
FIG. 7 is a configuration diagram of a light receiving device of the optical communication device according to the seventh embodiment of the present invention. The light receiving device of the optical communication device of the seventh embodiment shown in FIG. 7 has the structure of the light receiving device of the optical communication device of the third embodiment shown in FIG. 3 and a rod 22 connected to one end of the aperture 8; And an XYZ stage 23 connected to the other end of the body 22. The rod 22 and the XYZ stage 23 are provided in the light receiving container 1.

  The XYZ stage 23 corresponds to the moving mechanism of the present invention, and is driven by a control signal from the outside of the light receiving container 1 to move the aperture 8 through the rod 22 in the X-axis direction (left-right direction) and Y-axis direction (up-down direction). ) And the Z-axis direction (front-rear direction).

  Therefore, by driving the XYZ stage 23, the aperture 8 can be adjusted to an optimal position according to the light incident angle.

  The light receiving device of the optical communication device of the seventh embodiment, the light receiving device of the optical communication device of the sixth embodiment, and the light receiving device of the optical communication device of the fifth embodiment may be used in combination. If comprised in this way, the effect of the light-receiving device of the optical communication apparatus of Example 7, the effect of the light-receiving device of the optical communication apparatus of Example 6, and the effect of the light-receiving device of the optical communication apparatus of Example 5 can be acquired. .

  The present invention is applicable to laser processing and the like.

1, 1a, 1b, 1c Light receiving container 2 Optical window 3, 7 Condensing lens 4 Collimating lens 5 Band pass filter 6 Light receiving element 8 Aperture 9 Concave lens 11 Incident light 12 Light beam 13 Stray light beam 21 Holder 22 Rod body 23 XYZ stage

Claims (7)

A first condenser lens for condensing incident light;
A collimating lens having a focal length shorter than a focal length of the first condenser lens, and converting light from the first condenser lens into parallel light;
A bandpass filter that allows parallel light from the collimating lens to be incident perpendicularly to a filter surface and transmits only the wavelength of the incident light; and
A light receiving element for detecting light transmitted by the bandpass filter;
A light receiving device for an optical communication device.   2. A second condensing lens is provided between the band pass filter and the light receiving element, and condenses light transmitted by the band pass filter and guides the light to the light receiving element. A light receiving device of the optical communication device according to 1.   An aperture is provided between the first condenser lens and the collimator lens and disposed at a focal position of the first condenser lens, and blocks light that is not condensed at the focal position of the first condenser lens. The light receiving device of the optical communication device according to claim 1 or 2. A concave lens that converts incident light into parallel light;
A bandpass filter that allows parallel light from the concave lens to be incident perpendicularly to the filter surface and transmit only the wavelength of the incident light; and
A condensing lens that condenses the light transmitted by the bandpass filter;
A light receiving element that detects light collected by the condenser lens;
A light receiving device for an optical communication device.   2. A light receiving container that houses the collimating lens and a moving mechanism that moves the collimating lens in three axial directions, and the moving mechanism is driven by a control signal from the outside of the light receiving container. A light receiving device of the optical communication device described.   A light receiving container that houses the second condensing lens and a moving mechanism that moves the second condensing lens in three axial directions, and the moving mechanism is driven by a control signal from the outside of the light receiving container; The light receiving device of the optical communication device according to claim 2, wherein the light receiving device is a light receiving device. The light receiving container that houses the aperture and a moving mechanism that moves the aperture in three axial directions, and the moving mechanism is driven by a control signal from the outside of the light receiving container. Light receiving device for optical communication device.

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