JPH0423242B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for optically scanning an object to be measured, and in particular to a device for optically scanning an object to be measured, and in particular, a device for stably self-exciting vibration of a scanning mirror at its own frequency of a vibration system. The present invention relates to an optical scanning device configured as follows.

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. At the same time, the infrared light is focused onto an infrared detector using a Cassegrain optical system consisting of two reflecting mirrors, and an image of the surface temperature distribution of the subject is obtained 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.

The present invention has been made to eliminate the drawbacks of the conventional scanning device, and will be described in detail 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 at a desired location on the holding table 9.

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 attached to the rear of the scanning mirror 1. This method utilizes the fact that the difference in magnetic flux causes a change in the 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. do.

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 with the same or almost the same frequency as the natural frequency of the vibration system composed of the scanning mirror 1, rotating shaft 2, spiral spring 5, etc. shown in FIG. 1, and 13 is a position detection device. an amplifier that amplifies the position signal detected by the device 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 period 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 excitation current is controlled according to a control signal obtained by processing a position signal sent through the position detector 10 and amplifier 13 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 (t ₂ in Fig. 4a)
~t ₃ ), since no signal is supplied to the input terminal 22a of the drive circuit 22, the switch element becomes non-conductive and the drive circuit 22
Although the rotation of the pulse motor 7 is stopped without supplying an excitation current to the excitation coil 7a, 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 to cause reciprocating vibration. 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 undergoes a normal rotation action due to the rotation of the pulse motor 7 and the rotation of the spiral spring 5. The reversal action caused by the restoring force reaches a stable equilibrium state, and the scanning mirror 1 resonates at a resonant frequency determined by the inertia and spring constant of the vibration system of the scanning mirror 1.
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 to the above level 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. 4a.
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 _E1 of the phase adjustment circuit 18 is set in advance for the phase delay of the position signal when the vibration system resonates, the transmitted position signal exceeds the trigger level _E1 . Sometimes, the phase and pulse width are adjusted by the phase adjustment circuit 18 and pulse width adjustment circuit 19, respectively, to produce a pulse signal of a constant width (Fig. 4 e).
will be processed. 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, which causes the switching circuit 21 to be activated almost simultaneously with this signal.
makes the start signal generator 12 side non-conductive and the signal generator 17 side conductive, so the signal generator 1
The pulse signal shown in FIG. 4e obtained in step 7 is sent to the drive circuit 22 as a drive signal via the switching circuit 21
is supplied to the input terminal 22a of. By that,
The drive circuit 22 operates in the same manner as the start pulse at the time of startup, and the excitation coil 7a of the pulse motor 7 is activated.
It operates so that an excitation current flows into it. Therefore,
When the output of the position signal detected by the position detector 10 is at or above the trigger level _E1 in the signal generator 17, the start pulse at startup is automatically switched by the switching circuit 21, and the signal is Since the pulse signal sent from the generator 17 is supplied as a drive signal to the drive circuit 22, this circuit system forms a kind of oscillation circuit to vibrate the scanning mirror 1 at the self-resonant frequency of the vibration system. 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 may be caused by a start pulse that is continuously sent out, causing transient vibration in the process from startup to resonance, or even during resonance, the vibration system may be affected by vibrations of each component. Because the vibration is unstable due to temperature, humidity, changes over time, etc., the position signal detected by the position detector 10 is converted into a control signal by the control signal generation circuit 14, and the excitation coil of the pulse motor 7 is activated by the control signal. By automatically controlling the excitation current supplied to the scanning mirror 1
It is configured to vibrate stably. That is, when the position signal is supplied to the control signal generation circuit 14, the position signal is converted into a DC signal by the rectifier circuit 15 in the preceding stage and is supplied to the comparator 16 in the subsequent stage.
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 and calculates the difference signal. Drive circuit 2 as a control signal
2 input terminal 22b. 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 beyond a predetermined value, the position detector 1
The position signal obtained at 0 increases in accordance with its amplitude, so after being amplified by the amplifier 13, the rectifier circuit 1
The DC signal converted by 5 also increases 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 sends the signal to the drive circuit 22.
is supplied to the input terminal 22b of. The drive circuit 2
2 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 of the vibration system.

In the embodiment described above, the scanning mirror 1 is started by a start pulse sent from the start signal generator 12, but in another embodiment of the present invention, the scanning mirror 1 is started by a start pulse sent from the start signal generator 12. Scanning mirror 1 held on rotating shaft 2 instead of a mirror
can also be activated in one direction using, for example, magnetic absorption. In this case, position detector 1
The position signal obtained from 0 may be converted into a pulse signal by the signal generator 17, and the pulse signal may be directly supplied to the input terminal 22a of the drive circuit 22. Further, 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 embodiment, the drive circuit 22 drives only one coil of the pulse motor 7 used as a drive source;
Even a system having two coils can be implemented by replacing each coil with a drive circuit having a function of alternately turning on and off each coil.

As described above, the present invention includes a scanning mirror, a rotating shaft to which the scanning mirror is fixed and rotatably supported, and an elastic body having one end fixed to the rotating shaft and the other end fixed to a desired member. and a rotating device that applies rotational force to the rotating shaft, means for detecting a position signal corresponding to the amount of displacement of the scanning mirror, and means for intermittently driving the electric motor with a signal based on the position signal. As a result, the scanning mirror can be self-excited to vibrate at the unique vibration frequency of the vibration system, and it also enables higher-speed scanning than conventional scanning devices using gears, cams, etc., and also reduces the size of the device. , weight can be reduced. Furthermore, since the scanning mirror vibrates at a resonant frequency, it can be vibrated with a desired amplitude with a small amount of power, and therefore power consumption can be extremely reduced.
Furthermore, even if the vibration of the scanning mirror fluctuates due to changes in the material of each element of the mechanical vibration system due to temperature, humidity, changes over time, etc., the amplitude of the vibration of the scanning mirror will not be reflected in the position signal. Since the scanning mirror is controlled to be constant by the control signal based on the scanning angle, the fluctuation can be compensated for, and the scanning mirror has excellent effects such as improving the stability with which the scanning mirror vibrates.

[Brief explanation of drawings]

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... Unit,
10...Position detector, 11...Protrusion, 12...
Start signal generator, 13...Amplifier, 14...
Control signal generation circuit, 15... Rectifier circuit, 16...
Comparator, 17... Signal generator, 18... Phase adjustment circuit, 19... Pulse width adjustment circuit, 20... 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 fixed and rotatably supported, an elastic body having one end fixed to the rotating shaft and the other end fixed to a desired member, and an elastic body fixed to the rotating shaft. a drive source that applies rotational force; a means for detecting a position signal corresponding to the amount of displacement of the scanning mirror; and a means for generating an excitation current for intermittently driving the drive source based on the position signal; means for detecting the strength of the position signal; comparison means for comparing the output signal of the position signal strength detection means with a reference value; and an excitation current to be supplied to the drive source based on the output signal of the comparison means. An optical scanning device characterized in that it comprises means for controlling.