JPS63216019A - Scanning optical system - Google Patents

Abstract

PURPOSE:To control a scanning quantity with high accuracy by controlling a voltage applied to a piezoelectric actuator according to the detected temperature of a temperature sensor which detects the temperature of the piezoelectric actuator. CONSTITUTION:This system consists of the temperature sensor 9 which detects the temperature of the piezoelectric actuator 4 and a control means 10 which controls the output voltage amplitude of a piezoelectric actuator driving circuit 5 according to the detected temperature of the temperature sensor 9. The temperature sensor 9 detects the temperature of the piezoelectric actuator 4 and outputs it to the control means 10. The control means 10 consists of an amplifier 11 which amplifies the output signal of the temperature sensor 9, an A/D converter 12 which converts the output analog signal of the amplifier 11 into a digital signal, a storage part 13 which stores previously the driving voltage for the piezoelectric actuator for making a necessary scan according to the temperature of the piezoelectric actuator, and a D/A converter 14 which converts the driving digital signal read out of the storage part 13 into an analog signal. Consequently, the constant scanning quantity is obtained without being affected by ambient temperature.

Description

[Detailed Description of the Invention] [Summary] The present invention provides a scanning optical system using a piezoelectric actuator, in order to eliminate errors in the scanning amount caused by ambient temperature.
A temperature sensor that detects the temperature of the piezoelectric actuator and a control means that controls the voltage applied to the piezoelectric actuator in accordance with the temperature detected by the temperature sensor are provided, and the scanning amount is always kept constant by the temperature sensor and the control means. This is what I did.

[Industrial application field]

The present invention relates to a scanning optical system used in an imaging device, and particularly to a scanning optical system in which the amount of displacement of the scanning optical system using a piezoelectric actuator does not affect the ambient temperature.

A scanning optical system using a piezoelectric actuator performs desired optical scanning by slightly displacing a scanning mirror such as a mirror or prism using the piezoelectric actuator.The small size of the piezoelectric actuator allows for the compactness of the imaging device. However, since the optical system is slightly displaced, it is necessary to control this displacement ii (scanning amount) with high precision.

[Conventional technology]

FIG. 3 shows a block diagram of essential parts of an imaging device using a conventional scanning optical system.

In FIG. 3, the conventional scanning optical system includes a lens 2 that collects light emitted from a target object 1, and a scanning mirror 3 that reflects the light collected by the lens 2 and enters a solid-state image sensor 6. , a piezoelectric actuator 4 that repeatedly scans the scanning mirror 3 by a predetermined displacement amount at a predetermined period, and a piezoelectric actuator drive circuit 5 that drives the piezoelectric actuator.

The imaging device also includes a solid-state imaging device (CCD) 6 that detects light from a target object I that enters through a scanning optical system and converts it into an electrical signal, and a signal processing circuit that processes the detected electrical signal into an image. 7, and a display section (CRT) 8 for displaying the output image signal of the signal processing circuit 7.

Light emitted from the target object I is condensed by a lens 2 and is incident on a scanning mirror 3. Now, when an AC voltage is applied to the piezoelectric actuator 4 from the piezoelectric actuator drive circuit 5, the output end 4-1 of the piezoelectric actuator 4 vibrates back and forth in the direction of the arrow shown in the figure, and the output end 4-1 vibrates through the shaft 3-1 that supports the scanning mirror 3. The scanning mirror 3 is reciprocated (scanned) in the direction of the dotted arrow (horizontal direction) to make light from the target object 1 enter each pixel 6-1 to 6-n of the solid-state image sensor 6.

By reciprocating scanning of the scanning mirror 3, each pixel 6-1 to 6-n of the solid-state image sensor 6 detects light from the target object 1 with approximately twice the sensitivity in the horizontal direction, converts it into an electrical signal, and converts it into an electrical signal. The electrical signal is output to the signal processing circuit 7 via the CCD 6', and an image of the target object is displayed on the display section 8 as a video signal.

Note that the amount of displacement of the scanning mirror 3 is proportional to the amplitude of the drive AC voltage from the piezoelectric actuator drive circuit 5, and a highly accurate amount of displacement is obtained by finely adjusting the amplitude of the applied voltage. Further, the displacement period is controlled by the frequency of the applied AC voltage.

[Problem that the invention seeks to solve]

In the above-mentioned scanning optical system, the amount of displacement of the piezoelectric actuator 4 is proportional to the amplitude of the drive voltage, and therefore the required amount of scanning can usually be obtained by driving with a constant voltage waveform. However, it is generally known that the amount of displacement by the piezoelectric actuator 4 changes not only depending on the amplitude of the drive voltage but also depending on the temperature.

Therefore, even when driven with a constant voltage waveform, if the ambient temperature changes significantly, an error will occur in the scanning amount, and the incident light on each pixel will be displaced, reducing the sensitivity and detection resolution of the imaging device. There is a problem that the image quality is degraded.

The present invention was created in view of these points, and an object of the present invention is to provide a scanning optical system that can obtain a constant scanning amount without being affected by ambient temperature.

[Means for solving problems]

FIG. 1 shows a principle block diagram of the scanning optical system of the present invention, in which a conventional scanning optical system includes a temperature sensor 9 that detects the temperature of the piezoelectric actuator 4, and a piezoelectric actuator that detects the temperature of the piezoelectric actuator 4 according to the temperature detected by the temperature sensor 4. The configuration includes a control means 10 for controlling the output voltage amplitude of the drive circuit 5.

[Effect]

The temperature sensor 10 detects the temperature of the piezoelectric actuator 10 and outputs it to the control means 10. The control means 10 stores in advance the driving voltage of the piezoelectric actuator for performing necessary scanning corresponding to the temperature of the piezoelectric actuator, and changes the driving voltage according to the output of the temperature sensor to control the ambient temperature. The scanning amount is kept constant regardless of the

〔Example〕

FIG. 2 shows a block diagram of a scanning optical system according to an embodiment of the present invention, in which the control means 10 includes an amplifier 11 that amplifies the output signal of the temperature sensor 10, and an analog signal output from the amplifier 11 into a digital signal. An A/D converter 12 for conversion, a memory unit (ROM) 13 that stores drive voltages for the piezoelectric actuator for performing necessary scanning in accordance with the temperature of the piezoelectric actuator, D/A converter 1 that converts the drive digital signal into an analog signal
It consists of 4.

As for the operation of the imaging device, light emitted from the target object 1 passes through the lens 2 and the scanning mirror 3 and enters the solid-state imaging device 6. The solid-state image sensor 6 detects incident light, converts it into an electrical signal, and outputs it to the signal processing circuit 7. Signal processing circuit 7
displays an image on a display unit (CRT) 8 using the input signal as a video signal.

At this time, optical scanning is performed by vibrating the scanning mirror 3 and changing the field of view of the solid-state image sensor 6.

On the other hand, the temperature sensor 9 detects the temperature of the piezoelectric actuator 4, and after the detection signal is amplified to a predetermined level by the amplifier 11, it is converted into a digital signal by the A/D converter 12.

The ROM 13 stores data for generating a driving voltage waveform for the piezoelectric actuator so that the displacement of the piezoelectric actuator is constant in response to the output of the temperature sensor 9, and the data is stored in the ROM 13 in accordance with the output of the temperature sensor 9. A digital signal of the actuator drive voltage corresponding to the signal is read out and output to the D/A converter 14. The D/A converter 14 is for converting the output of the ROM 13 into an analog voltage and inputting the analog voltage to the piezoelectric actuator drive circuit.

Now, if the ambient temperature changes and the temperature of the piezoelectric actuator 4 changes, the temperature sensor, A/D converter, R
The output of the piezoelectric actuator drive circuit is changed by the OM and D/A converter, and the amount of displacement (scanning) of the piezoelectric actuator 4 is always constant.

[Effects of the Invention] As described above, according to the present invention, the scanning amount of the scanning optical system using the piezoelectric actuator is constant regardless of the ambient temperature, so a highly accurate scanning optical system can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a principle block diagram of the scanning optical system of the present invention, Fig. 2 is a block diagram of the main parts of an imaging device using the scanning optical system of one embodiment, and Fig. 3 is an imaging using a conventional scanning optical system. FIG. 2 is a block diagram of main parts of the device.

Claims (1)

[Claims] In a scanning optical system that applies an alternating current voltage to a piezoelectric actuator (4) to vibrate it and displace a scanning mirror (3) by the vibration, the temperature sensor detects the temperature of the piezoelectric actuator (4). (9); and a control means (10) for controlling the AC voltage applied to the piezoelectric actuator according to the temperature detected by the temperature sensor (9).