JPS6252282B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for optically scanning an object to be measured, and in particular to an optical apparatus in which a scanning mirror is configured to stably self-oscillate at its own frequency of a vibration system. This aims to improve the startability of the scanning device.

As is well known, infrared cameras that measure temperature patterns reflect radiation from an object using a two-dimensionally moving scanning reflector (hereinafter referred to as a scanning mirror) installed behind the camera's entrance window. In addition, this device focuses infrared light onto an infrared detector using a Cassegrain optical system consisting of two scanning mirrors, and obtains an image of the surface temperature distribution of the subject on a display device.

The means for scanning the object used in such devices generally vibrates a scanning mirror using a scanning mechanism composed of gears, cams, electric motors, etc.
Since the scanning mechanism forcibly vibrates the scanning mirror by the rotation of the cam, the vibration of the scanning mirror may become unstable due to poor machining accuracy of the cam, etc., or the scanning speed may be limited. Furthermore, this method has disadvantages such as an increase in the size of the device.

Recently, a scanning device has been proposed in which a scanning mirror is attached to a rotating shaft, an elastic body is interposed between the rotating shaft and a fixed member, and the scanning mirror is self-excited to vibrate at the natural frequency of the vibration system. Ta. However, since such a device generates self-excited vibration, there is a problem particularly in starting it from a stationary state.

The present invention has been made in view of the above-mentioned problems, and will be described in detail below based on an embodiment shown in the drawings.

FIG. 1 shows an embodiment of the optical scanning mechanism used in the present invention. Reference numeral 1 denotes a scanning mirror using a flat reflecting mirror, which is fixed to a rotating shaft 2 by a desired member (not shown). ing. The rotating shaft 2 is rotatably supported by a bearing 4 interposed at the upper center of the frame 3, and is fixed to one end of a spiral spring 5 as shown in FIG. The other end of the spiral spring 5 is fixed at a desired position on the frame 3. The lower part of the rotating shaft 2 is fixed to one member 6a of the coupling device 6. The coupling device 6
The other member 6b is fixed to a drive shaft 8 connected to a pulse motor 7. The pulse motor 7 is attached to the frame 3, and is supplied with a start pulse of a desired frequency from a start pulse generator 12 shown in FIG. Moreover, the frame body 3
A detector 10 is mounted on a holding table 9 at a desired location.

The position detector 10 is a converter for converting the mechanical vibration of the scanning mirror 1 into an electrical quantity, and generally uses a magnet sensor using a well-known magnetoresistive element, a moiré fringe detector, or the like. be able to. In one embodiment of the invention, a magnetic sensor is illustrated as the position detector 10. The magnetic sensor has two magnetoresistive elements connected in series, and a magnetic protrusion 11 is attached to the rear of the scanning mirror 1. This method utilizes the fact that the difference in magnetic flux causes a change in resistance value, and detects a voltage signal (hereinafter referred to as a position signal) corresponding to the amount of movement of the protrusion 11, that is, the amplitude and frequency of vibration of the scanning mirror 1. .

FIG. 3 shows an embodiment of the electric circuit of the optical scanning mechanism shown in FIG.
1 is a start pulse generator that generates a start pulse having the same or almost the same frequency as the natural frequency of the vibration system made up of the scanning mirror 1, rotating shaft 2, spiral spring 5, etc. shown in FIG. 1, and 13 is a position detector. an amplifier for amplifying the position signal detected at 10;
Reference numeral 14 denotes a control signal generation circuit that processes the position signal to generate a control signal, and includes a rectifier circuit 15 and a comparator 16 equipped with a reference signal source that can set a desired reference value.
It consists of 17 is the resonance frequency of the inertia of the scanning mirror 1 and the vibration system of the spiral spring 5;
This is a signal generation circuit that generates a drive signal with the same waveform as the start signal, and is composed of a phase adjustment circuit 18 and a pulse width adjustment circuit 19. The phase adjustment circuit 1
8 and the pulse width adjustment circuit 19, monostable multivibrator circuits are used, respectively. 20
2 is a switching signal generator that generates a switching signal when the drive signal reaches a desired level; 21 is a switching circuit operated by the switching signal; and 22 is for supplying exciting current to the exciting coil 7a of the pulse motor 7. In this drive circuit, for example, an amplitude control element, the excitation coil 7a, and a switch element are connected between the B power supply and ground, respectively. Incidentally, reference numeral 22a indicates an input terminal of the switch element, to which a start signal or drive signal sent through the switching circuit 21 is supplied, and reference numeral 22b indicates an input terminal of the amplitude control element. A control signal obtained by a control signal generation circuit 14 is supplied.

In such a device, when the start pulse shown in FIG.
Supply to a. During the high-level half cycle of the start pulse (t ₁ to t ₂ in FIG. 4a), the internal switch element of the drive circuit 22 is driven and supplies an excitation current to the excitation coil 7a of the pulse motor 7. , the exciting current is supplied to the position detector 10 and the amplifier 13.
The control signal is controlled in accordance with a control signal processed by a control signal generation circuit 14 which will be described later. When the excitation current is supplied to the pulse motor 7, the rotating part 7b of the pulse motor 7 rotates, and this rotation causes the rotating shaft 2 to spiral through the drive shaft 8 of the vibration system and the members 6b and 6a of the coupling device 6. The spring 5 is rotated in the direction of contraction, that is, in the normal rotation direction. Also, the half period of the low level of the start pulse (from t ₂ in Figure 4 a)
t ₃ ), the input terminal 2 of the drive circuit 22
Since no signal is supplied to 2a, the switch element becomes non-conductive and the drive circuit 22
In this case, the rotation of the pulse motor 7 is stopped without supplying an excitation current to the excitation coil 7a, but the rotating shaft 2 is reversed by the restoring force stored in the spiral spring 5. Therefore, the rotating shaft 2 is alternately rotated forward and backward by the interaction between the rotation of the pulse motor 7 and the restoring force of the spiral spring 15, and as a result, the rotating shaft 2
The scanning mirror 1 held in the mirror 1 is alternately rotated forward and backward, causing it to vibrate back and forth. The reciprocating vibration of the scanning mirror 1 undergoes an initial transient reciprocating vibration due to the start pulse of the start signal generator 12 that is continuously supplied, and then the forward rotation action due to the rotation of the pulse motor 7 and the spiral spring 5. The reversal action due to the restoring force of
vibrates in a sine wave.

On the other hand, when a position signal corresponding to the amplitude of vibration of the scanning mirror 1 is detected by the position detector 10, the position signal is supplied to each control signal generator 14 and signal generator 17 via an amplifier 13. , until the scanning mirror 1 resonates, the amplitude of the position signal is small and cannot reach the trigger point of the phase adjustment circuit 18 where the desired trigger level is set in advance, and the phase adjustment circuit 18 is not driven. Not done. However, scanning mirror 1
When reaches near resonance, the position signal has the desired level as shown in FIG. 4b;
The amplifier 13 adjusts the amplitude to the trigger level, e.g. E ₁ , at its rising edge as shown in FIG.
Since the position signal is amplified above and supplied to the phase adjustment circuit 18, when the position signal exceeds the trigger point, the phase adjustment circuit 18 outputs a constant width as shown in FIG. 4d.
A pulse signal of T ₁ is generated. When the pulse signal is supplied to the pulse width adjustment circuit 19, the pulse width adjustment circuit 19 is driven by the falling edge of the waveform, and a pulse signal with a constant width T ₂ is output to the output side as shown in FIG. 4e. is generated. That is, since the trigger level E ₁ of the phase adjustment circuit 18 is set in advance for the delay in the phase of the position signal during resonance of the vibration system, the transmitted position signal exceeds the trigger level E ₁ . When the pulse width is exceeded, the phase and pulse width are adjusted by the phase adjustment circuit 18 and pulse width adjustment circuit 19, respectively, and the pulse signal is processed into a constant width pulse signal (FIG. 4e). As a result, a pulse signal (FIG. 4e) having the same waveform as the start pulse shown in FIG. 4a is obtained from the signal generator 17. The pulse signals are supplied to a switching signal generator 20 and a switching circuit 21, respectively. The switching signal generator 20 processes the pulse signal to generate a switching signal, and the switching signal causes the switching circuit 21 to make the start signal generator 12 non-conductive almost at the same time as this signal. In order to conduct the generator 17 side, the pulse signal shown in FIG. Thereby, the drive circuit 22 operates in the same manner as the start pulse at the time of starting, and operates so as to cause an excitation current to flow into the excitation coil 7a of the pulse motor 7. Therefore, when the output of the position signal detected by the position detector 10 is at the trigger level _E1 or higher in the signal generator 17, the start pulse at startup is automatically switched by the switching circuit 21, and the start pulse at the time of startup is automatically switched. Thereafter, the pulse signal sent from the signal generator 17 is supplied as a drive signal to the drive circuit 22, so this circuit system forms a kind of oscillation circuit and vibrates the scanning mirror 1 at the self-resonant frequency of the vibration system. It can be done. Thus, the scanning mirror 1 can be vibrated with a large amplitude even if the power supplied to the drive circuit 22 is very small. In addition, the reciprocating vibration of the scanning mirror 1 causes vortex vibrations in the process from startup to resonance due to the continuously sent start pulses, or even during resonance, the parts constituting the vibration system The position signal detected by the position detector 10 is converted into a control signal by the control signal generation circuit 14, and the pulse motor 7 is excited by the control signal. The scanning mirror 1 is configured to stably vibrate by automatically controlling the excitation current supplied to the coil 7a. That is, the position signal is generated by the control signal generation circuit 14.
If the position signal is supplied to
However, since a desired reference value is set in advance in the comparator 16, the comparator 16 compares the reference value with the DC signal converted by the rectifier circuit 15. The difference signal is then supplied to the input terminal 22b of the drive circuit 22 as a control signal.
Therefore, the drive circuit 22 supplies an excitation current according to the magnitude of the control signal to the excitation coil 7a of the pulse motor 7, thereby automatically controlling the rotational torque of the pulse motor 7. For example, if we consider a case where the amplitude of vibration of the scanning mirror 1 increases from a predetermined value, the position signal obtained by the position detector 10 increases correspondingly to the amplitude, so after being amplified by the amplifier 13, the position signal is The DC signal converted by is also increased by that amount. When the increased DC signal is supplied to the comparator 16, the comparator 16 generates a negative signal corresponding to the increased amount and supplies this signal to the input terminal 22b of the drive circuit 22.
The drive circuit 22 reduces the excitation current supplied to the excitation coil 7a of the pulse motor 7, and as a result, the rotational torque of the pulse motor 7 is reduced and the amplitude of vibration of the scanning mirror 1 is kept constant. Furthermore, when the amplitude of vibration of the scanning mirror 1 decreases, the rotational torque of the pulse motor 7 increases by the decreased amount, in a completely opposite effect to that described above, so that the amplitude of the scanning mirror 1 returns to its original value.

In this way, when the amplitude of the scanning mirror 1 increases, it works to decrease it, and when the amplitude decreases, it works to increase it, so the scanning mirror 1 is automatically controlled. The vibration system is always vibrated at a constant amplitude and at a unique vibration frequency that the vibration system has.

Note that the drive source for applying rotational force to the drive shaft 8 is not limited to the pulse motor 7 alone, and in the present invention, an ordinary electric motor or one constructed of a coil and a magnet can be used. Furthermore, the spiral spring 5 can be replaced with a normal elastic body.
Furthermore, in the above-mentioned embodiment, the drive circuit 22 drives only one coil of the pulse motor 7 used as a drive source, but even if it has two coils, each coil may be driven alternately. This can also be implemented by replacing it with a drive circuit that has the function of turning on and off.

Further, in the above embodiment, the displacement of the scanning mirror 1 is directly detected using a position detector, but the present invention is not limited to this, and it is sufficient to detect a signal corresponding to the displacement of the scanning mirror. For example, it is possible to detect vibrations of the rotating shaft. It's okay.

As described above, according to the present invention, a start pulse having a frequency based on the natural vibration frequency of the vibration system, for example, a frequency equal to or almost equal to the natural vibration frequency, is sent to the pulse motor 7 to forcibly vibrate the scanning mirror. After the vibration system approaches a resonant state and the amplitude becomes sufficiently large, the drive signal created based on the position signal in the signal generation circuit 17 is sent to the pulse motor instead of the start pulse, so the device can quickly operate in any case. is started.

[Brief explanation of the drawing]

FIG. 1 is an embodiment of the optical scanning mechanism used in the present invention, FIG. 2 is a sectional view taken along line A-B in FIG. FIG. 4 is an electrical system diagram for explaining the operation of FIG. 3. 1: Scanning mirror, 2: Rotating shaft, 3: Frame, 4: Bearing, 5: Spiral spring, 6: Coupling device, 7: Pulse motor, 8: Drive shaft, 9: Stand, 10: Position detector, 11 : protrusion, 12: start signal generator,
13: Amplifier, 14: Control signal generation circuit, 15:
Rectifier circuit, 16: Comparator, 17: Signal generator, 1
8: Phase adjustment circuit, 19: Pulse width adjustment circuit, 2
0: switching signal generator, 21: switching circuit, 22: drive circuit.

Claims (1)

[Claims] 1. A scanning mirror, a rotating shaft to which the scanning mirror is attached and rotatably supported, an elastic body having one end attached to the rotating shaft and the other end attached to a fixed member, and a rotational force applied to the rotating shaft. A start signal generator that generates a start signal having a frequency based on the natural vibration frequency of a vibration system consisting of a drive source that provides a drive source, the scanning mirror, a rotating shaft, and an elastic body, and supplies the start signal to the drive source at the time of startup. a circuit, and means for detecting a position signal corresponding to the displacement of the scanning mirror;
means for waveform shaping the position signal to create a drive signal for driving the drive source having the same frequency as the position signal and having an adjusted phase relationship with the position signal;
An optical scanning device characterized by comprising a switching means for switching the signal supplied to the driving means from a start signal to an output signal of the signal generating means when the intensity of the position signal exceeds a predetermined level.