JPH0618258Y2 - Photo detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a photodetector for receiving and detecting continuous light or modulated light supplied from a light source, for example.

[Prior Art] Generally, a photodiode is used for the measurement of an optical power meter. However, since the minimum light receiving level is determined by the drift due to the dark current of the photodiode, the AC voltage is low when the low level measurement is performed. Detection is required.

[Problems to be solved by the invention] By the way, there are a feed modulation method and a reception modulation method in the optical power measurement method by this type of AC detection, and it is necessary to connect a dedicated photodetector according to the measurement method. was there.

That is, since the feed modulation type photodetector is equipped with an AC detection circuit, it was impossible in principle to measure continuous light.

In addition, the receiving modulation type photodetector uses incident light, that is,
Since a mechanism for modulating continuous light with a tuning fork vibrator is provided, there is a problem that the signal after detection becomes unstable when the incident light is modulated light.

Therefore, the present invention has been made in view of the above-mentioned problems, and its purpose is to detect and stabilize these lights regardless of whether the incident light is continuous light or modulated light. It is to provide a photodetector that can obtain a signal.

[Means for Solving the Problems] In order to achieve the above object, the photodetector according to claim 1 of the present invention is a photodetector for detecting the optical power of continuous light or modulated light output from a light source on an optical path. A tuning fork oscillator for chopping the light on the optical path by vibration of a natural frequency, and a moving block for moving an end of the tuning fork oscillator forward and backward with respect to the optical path, wherein the light source emits continuous light. While outputting, while controlling the movement of the moving block so as to guide the end portion of the tuning fork vibrator to the optical path, when the light source is outputting modulated light, And a drive mechanism for controlling the movement of the moving block so as to avoid the end portion from the optical path.

The photodetector according to claim 2 further includes a processing circuit for detecting the optical power of continuous light or modulated light output from the light source onto the optical path, a tuning fork oscillator for chopping the light on the optical path, An oscillation circuit that oscillates the tuning fork oscillator at a natural frequency, a drive mechanism that advances and retracts the end of the tuning fork oscillator with respect to the optical path, and the tuning fork when receiving a detection signal indicating continuous light from the processing circuit. A command signal for vibrating the tuning fork vibrator by guiding the end portion of the vibrator onto the optical path is output to the oscillation circuit and the drive mechanism, and a detection signal indicating modulated light is received from the processing circuit. The control circuit is configured to output a command signal for avoiding the end of the tuning fork vibrator from the optical path to the drive mechanism.

[Operation] In the photodetector according to claim 1, when the light source outputs continuous light, the moving block guides the end of the tuning fork vibrator to the optical path by the driving mechanism, and vibrates the tuning fork vibrator at a natural frequency. Let's chop the continuous light. When the light source outputs the modulated light, the moving block causes the moving block to avoid the end of the tuning fork vibrator from the optical path, and cancels the chopping of the tuning fork vibrator on the optical path.

In the photodetector of claim 2, the processing circuit detects the optical power of continuous light or modulated light output from the light source on the optical path. When the control circuit receives the detection signal indicating continuous light from the processing circuit, it outputs a command signal to the drive mechanism and the oscillation circuit,
The end of the tuning fork vibrator is guided to the optical path, and the tuning fork vibrator is controlled to vibrate at its natural frequency. As a result, the continuous light from the light source is chopped by the vibration of the tuning fork vibrator, and the chopped light is detected by the processing circuit. In addition, when the control circuit receives the detection signal indicating the modulated light from the processing circuit, it outputs a command signal to the drive mechanism to control the end of the tuning fork vibrator to avoid the optical path and release the chopping of the tuning fork vibrator. To do. As a result, the modulated light from the light source is directly detected by the processing circuit without being chopped by the tuning fork vibrator.

[Embodiment] FIG. 1 is a view showing a schematic configuration of an embodiment of a photodetector according to the present invention.

The photodetector according to this embodiment is applied to various measuring instruments such as an optical power meter, and includes a photodetector 2, a processing circuit 3,
The tuning fork vibrator 4, the oscillation circuit 5, the drive mechanism 6, and the control circuit 7 are included in the overall configuration.

The measured light source 1 is composed of, for example, a light emitting diode, and continuous light of a constant level in time or modulated light intermittently at a constant level at a predetermined frequency with the passage of time passes through a linear optical path 8 to the side of the light receiver 2. Is output to.

The light receiver 2 is composed of, for example, a semiconductor photodiode and receives and detects the continuous light or the modulated light supplied from the light source 1. The received light is an alternating current in an amplifier circuit including a capacitor forming the processing circuit 3. Only the signal is detected and output to the circuit side in the subsequent stage.

The tuning fork vibrator 4 provided on the optical path 8 between the light source 1 and the light receiver 2 is in a state where continuous light is supplied from the light source 1,
When the end portion 4aa of one vibrating piece 4a is in a predetermined position on the optical path 8 as shown in FIG. 2 (a) and is in a vibrating state, the time when the vibrating piece 4a blocks the incident light and the time when it does not block the incident light are the same. It is fixed to be. This gives an impact coefficient of 50%
Light is guided to the light receiver 2 side. Also,
The tuning fork vibrator 4 has a base portion 4b pivotally supported on the apparatus main body side and is rotatable by a driving mechanism 6, and is configured to vibrate at a natural frequency by driving an oscillation circuit 5.
When continuous light is supplied from, the continuous light is chopped at a predetermined cycle (corresponding to the natural frequency of the tuning fork vibrator) and guided to the light receiver 2 side.

The drive mechanism 6 as a moving unit has a moving block 6a having a lever 6aa for moving one of the vibrating reeds 4a of the tuning fork vibrator 4 at its tip, and a motor 6b for controlling the moving block 6a. Drive circuit 6c
The movement is controlled by the drive circuit 6c based on the command signal from the control circuit 7, the motor 6b is driven, and the rotational force of the motor 6b is transmitted to the movement block 6a via the central axis. Then, the moving block 6a moves back and forth in a direction orthogonal to the optical path 8, and the lever 6aa comes in contact with and separates from one (lower) vibrating piece 4a of the tuning fork vibrator 4. The moving state of the moving block 6a at this time is detected by two sensors 10 and 11 (including mechanical switches) provided in the cylindrical body 9, and this detection signal is output to the control circuit 7. .

The control circuit 7 outputs a command signal for controlling the drive of the oscillation circuit 5 and the drive circuit 6c according to a signal indicating the type of light output from the light source 1 (continuous light or modulated light) or a detection signal from the sensors 10 and 11. Output to each.

Next, the operation of the photodetector configured as above will be described.

First, when continuous light is supplied from the light source 1, the lever 6aa
The moving block 6a is stopped at an initial position that covers half of the spot on the optical path 8, the oscillation circuit 5 is driven based on the control command signal from the control circuit 7, and the tuning fork vibrator 4 vibrates at the natural frequency. Due to the vibration of the tuning fork vibrator 4, the continuous light is chopped by the one vibrating piece 4a and is received and detected by the light receiver 2. Then, the received light is processed by the processing circuit 3 and output to the circuit in the subsequent stage.

Subsequently, in the case where the modulated light is supplied from the light source 1, when the drive circuit 6c is drive-controlled by the command signal from the control circuit 7, the motor 6b rotates and the rotational force of the motor 6b moves about the central axis. It is transmitted to the moving block 6a via the moving block 6a, so that the moving block 6a advances along the inner wall surface of the cylindrical body 9, and the tip of the lever 6aa contacts one of the vibrating pieces 4a of the tuning fork vibrator 4 and pushes it up. Cancel chopping of the optical path 8. As a result, the modulated light is directly detected by the light receiver 2 and then processed by the processing circuit 3 and output to the circuit at the subsequent stage.

In the operation described above, when the moving block 6a is stopped at the middle position of the tubular body 9, the two sensors 1
Since no detection signal is output from the control circuit 7 to the control circuits 0 and 11, it is judged to be a malfunction and the control of the apparatus is stopped.

Therefore, in the photodetector described above, when the continuous light is supplied as the incident light from the light source 1, the tuning fork vibrator 4 chops the optical path 8, and when the modulated light is supplied as the incident light, the tuning fork vibration is generated. Since the child 4 is controlled so as to avoid from the optical path 8, continuous light can be efficiently emitted by one detector without the troublesome work of changing the connection of the dedicated photodetector on the measurement side as in the conventional case. And the modulated light can be measured.

When selecting continuous light or modulated light as incident light, either (a) or (b) below is selected.

(B) In the case of automatic switching control, the detection circuit 14 detects a signal and sends the result to the control circuit 7.

(B) For manual control, the panel 12 shown in FIG.
This is performed by the switch 13 for changing the mode.

This enables measurement corresponding to the incident light.

Further, since this photodetector is configured not to move the entire tuning fork vibrator 4 for chopping light but to be rotatable about the base 4b as a fulcrum, the tuning fork vibrator 4 can be positioned reliably and with high accuracy. In addition, the shock coefficient of the received optical signal is maintained at 50%, and high accuracy can be obtained.

Further, since the tuning fork vibrator 4 is used to chop the continuous light, the light can be chopped at the natural frequency, and for example, it is directly affected by the rotation unevenness of the drive system like a rotating plate. In comparison, the accuracy of chopping can be improved, and the mechanism itself can be downsized to facilitate handling.

Furthermore, when measuring the optical loss of a multi-core optical fiber consisting of multiple optical fibers, measurement with modulated light is performed by changing the modulation frequency of the light incident on each fiber, and measurement with chopped continuous light with high sensitivity. Can be performed by one detector.

By the way, in the above-mentioned embodiment, the example in which the tuning fork vibrator 4 is used as the means for chopping the light has been described. However, if the tuning fork vibrator can vibrate at a natural frequency, the tuning fork vibrator may be used instead. You may use it.

[Effects of the Invention] As described above, according to the photodetector of the present invention, measurement of both continuous light and modulated light that propagates on the optical path and is incident is accurately received by one detector. Can be detected.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of a photodetector according to the present invention, and FIGS. 2 (a) and 2 (b) are diagrams for explaining the operation of the detector. 1 ... Light source, 2 ... Receiver, 4 ... Tuning fork oscillator, 5 ...
Oscillation circuit, 6 ... Driving mechanism (moving means), 7 ... Control circuit, 8 ... Optical path, 12 ... Panel, 13 ... Switch,
14 ... Detection circuit.

Claims (2)

[Scope of utility model registration request] 1. A photodetector for detecting the optical power of continuous light or modulated light output from a light source on an optical path, and a tuning fork oscillator for chopping the light on the optical path by vibration of a natural frequency, A moving block for moving the end of the tuning fork vibrator forward and backward with respect to the optical path, and guiding the end of the tuning fork vibrator onto the optical path when the light source outputs continuous light. A drive mechanism that controls the movement of the moving block and also controls the movement of the moving block so as to avoid the end portion of the tuning fork vibrator from the optical path when the light source outputs the modulated light. A photodetector characterized by being provided. 2. A processing circuit for detecting the optical power of continuous light or modulated light output from a light source on an optical path, a tuning fork oscillator for chopping the light on the optical path, and a tuning fork oscillator having a natural frequency. An oscillation circuit that vibrates at, a drive mechanism that moves the end of the tuning fork vibrator forward and backward with respect to the optical path, and an end of the tuning fork vibrator when the detection signal indicating continuous light is received from the processing circuit. The tuning fork vibrator is configured to output a command signal for guiding the light on the optical path to vibrate the tuning fork vibrator to the oscillation circuit and the driving mechanism, and to receive the detection signal indicating the modulated light from the processing circuit. A photodetector, comprising: a control circuit configured to output a command signal for avoiding the end of the child from the optical path to the drive mechanism.