JP3704816B2 - Optical axis adjustment method for optical wireless transmission apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical axis adjustment method for an optical wireless transmission apparatus for aligning optical axes of a light transmitting apparatus and a light receiving apparatus in an optical wireless transmission apparatus that transmits an optical wireless signal from a light transmitting apparatus to a light receiving apparatus.
[0002]
[Prior art]
Conventionally, an optical axis adjustment method for this type of optical wireless transmission apparatus is disclosed in Japanese Patent Laid-Open No. 6-224858. In this conventional example, a light receiving device having a narrow directivity half-value angle is scanned in the horizontal direction by rotating the stepping motor, for example, from left to right every 1 °, and when the horizontal scanning is completed, the light receiving device is moved to 1 °. After rotating downward, scanning in the horizontal direction is performed to search for a point where the maximum light receiving level is obtained in the two-dimensional coordinates.
[0003]
In this case, the reception level detected at each step is A / D converted, and the step number and the reception level are written in the memory by the processing of the microprocessor, and stored in the memory when a series of two-dimensional searches are completed. The step number corresponding to the maximum value of the reception level is specified, and the optical axis of the light receiving device is aligned with the position corresponding to the step number.
[0004]
[Problems to be solved by the invention]
Here, when long-distance transmission is performed by optical radio, it is desirable that the transmission light has a beam shape as thin as possible. In addition, when performing bidirectional communication by optical wireless, it is necessary to narrow the directivity of the light receiving device, and when performing a search based on the level of the light receiving device, the half-value angle of the directivity of the light receiving device is light emission. It is required to be narrower than the half-value angle of the directivity of the apparatus (the width of the half-value angle is referred to as the directivity width). For example, when the directivity angle of the light receiving device is 1.42 ° or more, if 30 steps in the horizontal direction and 30 steps in the vertical direction are required, the total is 900 steps. Further, if it takes 10 mS per step, it takes 9 seconds in total, and if the directivity angle of the light receiving device is 0.142 °, it takes 900 seconds to perform a series of searches. Therefore, the conventional example has a problem that when applied to a system that performs long-distance transmission by optical radio, the search time for aligning the optical axis becomes extremely long.
[0005]
By the way, in order to shorten the optical axis alignment time, the above-described search (scanning) is not performed, and a video camera is provided on the light receiving device side to image the vicinity of the light transmitting device in two dimensions. A method of recognizing by pattern recognition and specifying the direction in which the light receiving device faces based on the coordinates of the screen can be considered. However, this method has a problem that pattern recognition is uncertain simply by imaging the vicinity of the light transmitting device, and pattern recognition becomes more difficult when the light transmitting device is located far away. There is a problem.
[0006]
In view of the above problems, the present invention can shorten the time for aligning the optical axes of the light transmitting device and the light receiving device in the optical wireless transmission device that transmits the optical wireless signal from the light transmitting device to the light receiving device. It is an object of the present invention to provide an optical axis adjustment method for an optical wireless transmission apparatus capable of accurately aligning an optical axis.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention includes a two-dimensional image sensor that images the optical transmission device on the optical receiver side, and blinking light synchronized with the frame of the image sensor from the optical transmission device to the optical receiver device. The two-dimensional coordinates of the optical transmission device are calculated by imaging the blinking light with an image sensor and calculating the difference between the video signal in the on state and the off state.
[0009]
That is , according to the present invention, an optical transmission device including a transmitter that transmits an optical wireless signal with a relatively wide directivity, and a light receiving device that receives the optical wireless signal from the transmitter with a relatively narrow directivity. An optical axis adjustment method for an optical wireless transmission device that performs optical wireless transmission to and from an optical reception device equipped with an optical device,
The optical receiver includes a two-dimensional image sensor that images the optical transmitter,
The optical transmission device performs ASK modulation on a pulse signal having the same frequency as the frame pulse of the image sensor at a higher carrier frequency than the frequency at which the image sensor can recognize the signal as a blink signal, and causes the light transmitter to emit light by blinking light. Flash
When receiving the blinking light from the transmitter, the optical receiver generates an ASK demodulated pulse signal having the same frequency as the frame pulse, and drives the imaging device based on the generated pulse signal. The flashing light is imaged, and a two-dimensional coordinate of the optical transmitter is calculated by detecting a difference between temporally different frames, and the light receiver is directed in the direction of the light transmitter based on the two-dimensional coordinate. An optical axis adjustment method for an optical wireless transmission device, characterized by performing optical axis alignment, is provided.
[0010]
Further, according to the present invention, an optical transmission device including a light transmitter that transmits an optical wireless signal with a relatively wide directivity, and a light receiving device that receives the optical wireless signal from the light transmitter with a relatively narrow directivity. An optical axis adjustment method of an optical wireless transmission device irradiated with illumination light for performing optical wireless transmission with an optical receiving device provided with an instrument,
The optical receiver includes a two-dimensional image sensor that is driven by a frame pulse having the same frequency as the emission frequency of the illumination light for imaging the optical transmitter,
The optical transmission device receives the illumination light, generates a pulse signal having the same frequency as the emission frequency, and performs ASK modulation at a higher carrier frequency that can be recognized as a blinking signal by the imaging element than the emission frequency. Blinking the transmitter with a blinking light;
When receiving the blinking light of the transmitter, the optical receiver generates ASK signal with the same frequency as the emission frequency by performing ASK demodulation, and drives the imaging device based on the generated pulse signal. The flashing light is imaged, and a two-dimensional coordinate of the optical transmitter is calculated by detecting a difference between temporally different frames, and the light receiver is directed in the direction of the light transmitter based on the two-dimensional coordinate. An optical axis adjustment method for an optical wireless transmission device, characterized by performing optical axis alignment, is provided.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a transmitting device and a light receiving device that realize one embodiment of an optical axis adjusting method of an optical wireless transmission device according to the present invention.
[0012]
In the example illustrated in FIG. 1, after the transmission device 100 and the reception device 200 adjust the optical axis, the transmission device 100 is configured to transmit a video signal as a main signal to the reception device 200 by optical wireless. The transmission apparatus 100 has an optical system including a light transmitter 103 including an LED (light emitting diode) 101 and a lens 102 for transmitting an optical wireless signal with a relatively wide directivity, and a reception apparatus 200 for optical axis adjustment. A light receiver 105 having a PD (photodiode) 104 is provided to receive the transmitted light.
[0013]
The video signal transmitted to the receiving apparatus 200 is FM-modulated by the modulator 106 with a 10 MHz carrier in the transmitting apparatus 100, and then transmitted via the switch SW, the LED driver 107, and the light transmitter 103. The optical signal for optical axis adjustment from the receiving device 200 is photoelectrically converted by the light receiver 105, and this electric signal passes through the light receiving circuit 108, demodulator 109, switch SW, LED driver 107, and light transmitter 103. Feedback is provided to the receiving apparatus 200. The input side of the switch SW is connected to the light receiver 105 side during the optical axis adjustment, and is connected to the modulator 106 side during operation after completion of the optical axis adjustment.
[0014]
The receiving apparatus 200 has an optical system as a main signal receiving narrow directional light receiver 203 including a lens 201 and a PD 202 for receiving light from the light transmitter 103 on the transmitting apparatus 100 side with a relatively narrow directivity. A CCD 204 that images the transmission device 100 in two dimensions and a light transmitter 231 that includes an LED 205 to transmit an optical signal for optical axis adjustment to the transmission device 100 with a relatively wide directivity.
[0015]
In order to adjust the optical axis, the light receiver 203, the CCD 204, and the LED 205 are mounted on the main body 206, the main body 206 is mounted on the left / right rotation unit 207, and the left / right rotation unit 207 is mounted on the base 208. ing. The left / right rotation unit 207 can turn the main body 206 in the left / right direction by the driver 210 and the motor 211 based on the control of the microcomputer 209, and the base 208 is also controlled by the control of the microcomputer 209. The left and right rotating portion 207 and the main body 206 can be rotated in the vertical direction by the driver 212, the motor 213, and the cam 214.
[0016]
The signal photoelectrically converted by the PD 202 of the light receiver 203 is applied to the demodulator 222 via the light receiving circuit 221, and the signal modulated by the modulator 106 on the transmission device 100 side is demodulated into a video signal by the demodulator 222. This video signal is output to the TV monitor 224 via the output terminal 223. The CCD 204 is driven by the CCD controller 225 when the optical axis is adjusted, and a signal photoelectrically converted by the CCD 204 is A / D converted by the A / D converter 226 and then stored in the frame memory 227. Then, the difference extraction unit 228 extracts the difference between each of the video signals in the lighting state and the extinguishing state of the blinking light from the transmission device 100, and the frame and frame memory 227 that are A / D converted by the A / D converter 226. Is extracted and output to the microcomputer 209, and the microcomputer 209 calculates the two-dimensional coordinates where the transmitting apparatus 100 is located based on this difference.
[0017]
Further, in order to transmit the optical signal for adjusting the optical axis to the PD 104 on the transmission apparatus 100 side, the frame pulse when driving the CCD 204 is FM-modulated by the carrier of 2 MHz by the FM modulator 229, and based on this FM modulation signal. Thus, the LED 230 of the light transmitter 231 is driven by the driver 230.
[0018]
The optical axis adjustment method having the above configuration will be described. When the CCD 204 of the receiving apparatus 200 is driven by the CCD controller 225 and the LED 205 of the light transmitter 231 blinks at 2 MHz based on the frame pulse from the CCD controller 225, this blinking is performed. Since light is transmitted with a relatively wide directivity by the light transmitter 231, it is received by the light receiver 105 of the transmission device 100, applied to the demodulator 109 via the light receiving circuit 108, and demodulated into frame pulses by the demodulator 109. The This frame pulse is applied to the light transmitter 103 via the switch SW and the LED driver 107. Therefore, the LED 101 of the light transmitter 103 blinks at the cycle of the frame pulse.
[0019]
Further, since the light transmitter 103 has a relatively wide directivity, the blinking light is received and photoelectrically converted by the CCD 204 on the receiving device 200 side, and a difference extraction unit 228 extracts a difference between frames. In this case, since the CCD 204 images the same position in two frames, the background portion of the transmitter 100, particularly the light transmitter 103, is dark, and the position of the light transmitter 103 is, for example, about twice as bright. By blinking, the coordinates of the blinking position can be easily detected. Then, the optical axis is adjusted by rotating the main body 206 and the left and right rotation unit 207 so that the light receiver 203 is directed to this position.
[0020]
Next, a second embodiment will be described with reference to FIG. In the configuration of the transmission device 100a, an oscillator that generates a 50 Hz rectangular wave having the same frequency as the frame pulse of the CCD 204 on the reception device 200a side, instead of the light receiver 105, the light reception circuit 108, and the demodulator 109 shown in FIG. OSC) 110 and an ASK modulator 111 for ASK modulating this rectangular wave with a carrier of 1 MHz are provided, and an optical signal for optical axis adjustment is transmitted from the transmitting device 100a to the receiving device 200a. The receiving device 200a receives an optical signal for adjusting the optical axis from the transmitting device 100a with a relatively wide directivity instead of the FM modulator 229, the driver 230, and the light transmitter 231 (LED 205) shown in FIG. For this purpose, a light receiver 241 provided with a PD 240, a light receiving circuit 242, and an ASK demodulator 243 are provided. Other configurations are the same for both the transmitting apparatus 100a and the receiving apparatus 200a.
[0021]
When optical axis adjustment is performed in such a configuration, 50 Hz rectangular wave “1” and “0” are ASK modulated by a 1 MHz carrier in the transmission device 100a, and the ASK modulation signal is transmitted to the switch SW, the LED driver 107, and the transmission. It is transmitted via the optical device 103. Since the light transmitter 103 has a relatively wide directivity, the ASK modulated light is received and photoelectrically converted by the PD 240 on the receiving device 200a side.
[0022]
The signal photoelectrically converted by the PD 240 is applied to the ASK demodulator 243 via the light receiving circuit 242, and the ASK demodulated signal is demodulated into a 50 Hz rectangular wave by the ASK demodulator 243. To be applied. Similarly, the ASK modulated light from the transmitting device 200a is received by the CCD 204, but is photoelectrically converted as a blinking signal because the response characteristics of the CCD 204 are relatively slow, and therefore the blinking light from the transmitting device 200a and the CCD 204 are Since the frame period is synchronized, the coordinates of the blinking position can be detected.
[0023]
Next, a third embodiment will be described with reference to FIG. Here, in the configuration shown in FIGS. 1 and 2, when the transmission devices 100 and 100a are arranged indoors and are illuminated with illumination light, the video signals picked up by the CCD 204 on the reception devices 200 and 200a side are beat-like. Stripes may appear. Therefore, the transmission device 100b of the third embodiment is configured to solve this problem by using the illumination light 112 attached to the ceiling or the like. The receiving device 200a is the same as that in the second embodiment.
[0024]
Here, the illumination light 112 is lit by, for example, a commercial AC power supply of 50 Hz, and the frame pulse of the CCD 204 is also 50 Hz. The illumination light 112 is received and photoelectrically converted by the PD 113 having a relatively wide directivity, and the signal photoelectrically converted by the PD 113 is shaped into a 50 Hz rectangular wave by the pulse reproduction circuit 115 via the light receiving circuit 114. . Then, “1” and “0” of the 50 Hz rectangular wave are ASK-modulated by the ASK modulator 111 with the carrier of 1 MHz as in the second embodiment, and the ASK modulated light from the transmitting device 100b is transmitted to the receiving device 200a side. Images are taken by the CCD 204.
[0025]
In such a configuration, the background of the transmission device 100b is illuminated by the illumination light 112 with light that increases or decreases with, for example, a commercial AC power supply of 50 Hz, but the power frequency of the illumination light 112 and the frame frequency of the CCD 204 may be matched. Therefore, it is possible to prevent beat-like stripes from appearing in the video signal imaged by the CCD 204 on the receiving device 200a side, and to extract the difference between frames to the maximum .
[0026]
Next, a fourth embodiment will be described with reference to FIG. In FIG. 4, a zoom lens 201a is provided in front of the CCD 204, and the microcomputer 209 shown in FIGS. 1 to 3 controls the zoom lens driving unit 201b to widen or narrow the field of view of the CCD 204. When optical axis alignment is performed in such a configuration, first, the zoom lens 201a is set to the widest field of view, and the coordinates of the blinking position are detected based on the modulated light from the transmission devices 100, 100a, 100b. Align the axis.
[0027]
Next, the zoom lens 201a is set to an intermediate field of view, and similarly, the coordinates of the blinking position are detected based on the modulated light from the transmission devices 100, 100a, 100b, and the optical axis is adjusted to an intermediate level. 201a is set to the narrowest field of view and the finest optical axis alignment is performed. Therefore, according to such a method, the optical axis can be aligned with a wide range of targets by changing the zoom ratio. Of course, the search may be performed by continuously changing the zoom ratio.
[0028]
The fifth embodiment shown in FIG. 5 shows a modification of the fourth embodiment, and a zoom lens 201a and a CCD 204 are provided in a main signal receiving narrow directional light receiver 203b. In the light receiver 203b, the reflective surface 250 is detachably disposed in the optical path of the zoom lens 201a, and the reflective surface 250 is retracted from the optical path during optical axis adjustment (search) as shown in FIG. The modulated light incident through the zoom lens 201a is picked up by the CCD 204 and, for example, coarse adjustment, medium adjustment, and fine adjustment are performed. Further, when the main signal is received after the optical axis adjustment is completed, the reflection surface 250 is inserted into the optical path, and the main signal incident through the zoom lens 201a is reflected by the reflection surface 250 and received by the PD 202. In this case, since the fine adjustment is performed, the resolution at the time of receiving the main signal can be improved.
[0029]
【The invention's effect】
As described above, according to the present invention, the two-dimensional imaging device that images the optical transmission device is provided on the optical reception device side, and the flashing light synchronized with the frame of the imaging device from the optical transmission device to the optical reception device. The two-dimensional coordinates of the optical transmission device are calculated by imaging the blinking light with the image sensor and calculating the difference between the lighted and unlit video signals. The optical axis can be accurately adjusted.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a transmitting device and a light receiving device that realize an embodiment of an optical axis adjusting method of an optical wireless transmission device according to the present invention.
FIG. 2 is a configuration diagram showing a transmitting device and a light receiving device that realize a second embodiment of the optical axis adjusting method of the optical wireless transmission device according to the present invention.
FIG. 3 is a configuration diagram illustrating a transmitting device and a light receiving device that realize a third embodiment of the optical axis adjusting method of the optical wireless transmission device according to the invention.
FIG. 4 is a configuration diagram showing a CCD that realizes a fourth embodiment of an optical axis adjustment method for an optical wireless transmission apparatus according to the present invention;
FIG. 5 is a block diagram showing a main signal receiving narrow directivity receiver that realizes a fifth embodiment of the optical axis adjustment method of the optical wireless transmission apparatus according to the present invention;
[Explanation of symbols]
100, 100a, 100b Transmitting device 101, 205 LED (light emitting diode)
102, 201 Lens 103, 231 Transmitter 104, 113, 202, 240 PD (photodiode)
105, 241 Light receiver 106 Modulator 107 LED driver 108, 114, 221, 242 Light receiving circuit 109, 222 Demodulator 110 Oscillator 111 ASK modulator 112 Illumination light 115 Pulse regeneration circuit 200, 200a Receiver 201a Zoom lens 201b Zoom lens drive 203, 203b Narrow directional light receiver 204 for receiving main signal CCD (image sensor)
206 Main body 207 Left / right rotation unit 208 Base 209 Microcomputer 210, 212, 230 Driver 211, 213 Motor 214 Cam 223 Output terminal 224 TV monitor 225 CCD controller 226 A / D converter 227 Frame memory 228 Difference extraction unit 229 FM modulator 243 ASK demodulator 250 Reflective surface

Claims (2)

An optical transmitter including a transmitter that transmits an optical wireless signal with a relatively wide directivity; and an optical receiver including a light receiver that receives an optical wireless signal from the transmitter with a relatively narrow directivity; An optical axis adjustment method for an optical wireless transmission device that performs optical wireless transmission between
The optical receiver includes a two-dimensional image sensor that images the optical transmitter,
The optical transmission device performs ASK modulation on a pulse signal having the same frequency as the frame pulse of the image sensor at a higher carrier frequency than the frequency at which the image sensor can recognize the signal as a blink signal, and causes the light transmitter to emit light by blinking light. Flash
When receiving the blinking light from the transmitter, the optical receiver generates an ASK demodulated pulse signal having the same frequency as the frame pulse, and drives the imaging device based on the generated pulse signal. The flashing light is imaged, and a two-dimensional coordinate of the optical transmitter is calculated by detecting a difference between temporally different frames, and the light receiver is directed in the direction of the light transmitter based on the two-dimensional coordinate. An optical axis adjustment method for an optical wireless transmission apparatus, characterized in that optical axis alignment is performed. An optical transmitter including a transmitter that transmits an optical wireless signal with a relatively wide directivity; and an optical receiver including a light receiver that receives an optical wireless signal from the transmitter with a relatively narrow directivity; An optical axis adjustment method for an optical wireless transmission device irradiated with illumination light for performing optical wireless transmission between
The optical receiver includes a two-dimensional image sensor that is driven by a frame pulse having the same frequency as the emission frequency of the illumination light for imaging the optical transmitter,
The optical transmission device receives the illumination light, generates a pulse signal having the same frequency as the emission frequency, and performs ASK modulation at a higher carrier frequency that can be recognized as a blinking signal by the imaging element than the emission frequency. Blinking the transmitter with a blinking light;
When receiving the blinking light of the transmitter, the optical receiver generates ASK signal with the same frequency as the emission frequency by performing ASK demodulation, and drives the imaging device based on the generated pulse signal. The flashing light is imaged, and a two-dimensional coordinate of the optical transmitter is calculated by detecting a difference between temporally different frames, and the light receiver is directed in the direction of the light transmitter based on the two-dimensional coordinate. An optical axis adjustment method for an optical wireless transmission apparatus, characterized in that optical axis alignment is performed.

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