JPS59182419A - Acoustic optical element - Google Patents

Abstract

PURPOSE:To monitor by a real time a state of an ultrasonic wave which is contributed to an optical diffraction in an acoustic optical medium by providing an ultrasonic wave receiving transducer on a part of an opposed surface of an ultrasonic wave transmitting transducer. CONSTITUTION:An acoustic optical medium 11 has two parallel main surfaces and incident and emitting surfaces of a light, which cross said surface, and is made of glass or a single crystal material. An ultrasonic wave transmitting transducer 12 is provided on the main surface of the medium 11, and an input terminal 14 of an ultrasonic exciting energy is connected through an impedance matching part 13. An ultrasonic wave receiving transducer 15 is provided selectively on a part opposed to the transducer 12, on the other surface of the medium 11, and also an ultrasonic wave absorbing layer 16 for preventing an ultrasonic reflection is provided. The layer 16 absorbs an ultrasonic flux 17 from the transducer 12. An output terminal 18 is connected to the transducer 15 through an impedance matching part 19.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an acousto-optic device.

Conventional Structure and Problems In recent years, acousto-optic devices have attracted attention as laser light control devices. As an example of its use, the use of the optical frequency shift effect due to drag-grafting is being studied. This is the frequency ν of the light incident on the acousto-optic element. is diffracted by the acousto-optic element, and shifted by the ultrasonic frequency ν8 that contributed to the diffraction, and becomes the frequency of the diffracted light ν. ±ν
8 is the effect obtained. By utilizing this effect, changes in the area through which the laser beam passes can be easily measured.

In other words, laser light weight. is incident on the acousto-optic element, the light obtained as diffracted light is extracted, and is passed through the space to be measured, whereby 11 is affected as a change in frequency or phase. Next, if the light affected by this is mixed with light 1' taken out for reference from the original light and caused to interfere, the beat signal will be a Doppler shift signal due to superacoustics and a disturbance signal received in the measured space. It is possible to obtain a signal that is the sum of Practical applications are being researched in a wide range of fields based on such basic measurement principles.

FIG. 1 shows a schematic diagram of a conventionally used acousto-optic element. 1 is an input terminal for ultrasonic excitation energy, and 2 is an impedance matching unit for efficiently sending the ultrasonic excitation energy 1 applied from the input terminal 1 to the ultrasonic wave transmission transducer 3. 4 is an acousto-optic medium, on which an ultrasonic wave transmission transducer 3 is pasted, optical surfaces ea, e, b for inputting and outputting light, and an ultrasonic unnecessary reflection provided to prevent ultrasonic waves from being reflected in the same path. A prevention surface 7 is provided. 6 is the area where ultrasonic waves exist (ultrasonic bundle)
It shows.

Now, consider a case where incident light 8 such as a laser beam is incident from the light entrance surface 6a. If the light incident direction is selected appropriately, if the ultrasonic excitation energy is not applied from input terminal 1,
Only transmitted light 10 exists, but when ultrasonic excitation energy is applied to input terminal 1, a part of transmitted light 10 is diffracted by the acousto-optic effect, and diffracted light 9 is generated. The frequency ν1 of this diffracted light is the frequency ν of the incident light. , if the frequency of the ultrasonic wave is ν8, then ν1-ν. ±νa (decoding takes either one depending on the direction of light incidence). When the ultrasonic waves emitted from the ultrasonic wave transmitting transducer 3 reach the opposite surface of the acousto-optic medium 4 to which the ultrasonic wave transmitting transducer 3 is bonded, the ultrasonic waves are transmitted to the pair so that the input and output directions of the ultrasonic waves are different. An unnecessary anti-reflection surface 7 is provided to prevent the incident light 12 from being diffracted again by reflected ultrasonic waves.

When trying to configure a measurement system or the like using an acousto-optic element as described above as an optical frequency shifting device, no matter how strictly the generated ultrasonic waves are controlled on the ultrasonic transducer 3 side, the acousto-optic medium 4 Since the ultrasonic wave is subjected to disturbance while propagating inside, it has the disadvantage that the measurement accuracy cannot be lowered below the disturbance noise.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention provides the above-mentioned laser measurement system, which has a structure that enables the control of ultrasonic waves handled within an acousto-optic element and allows easy monitoring of changes in the ultrasonic waves due to disturbances in the acousto-optic medium. The aim is to dramatically improve the accuracy of

Structure of the Invention To achieve this object, the acousto-optic device of the present invention comprises an acousto-optic medium, an ultrasonic transmitting transducer for emitting ultrasonic waves, and a portion of the ultrasonic waves emitted from the ultrasonic transmitting transducer. This device includes an ultrasonic receiving transducer that receives ultrasonic waves, and an ultrasonic absorbing layer provided to prevent incident light from being re-diffracted by reflected ultrasonic waves.

With this configuration, the ultrasonic waves emitted from the transmitting transducer into the acousto-optic medium can be made acoustic even if the ultrasonic waves are affected by changes in the acousto-optic medium due to disturbances, the frequency two phases of the ultrasonic waves, the speed of sound, etc. After propagation through the optical medium, the fluctuation can be detected by the ultrasonic transducer, so by subtracting the disturbance signal of the acousto-optic medium from the beat signal obtained as the output signal of the laser measurement system,
Highly accurate measurements can be achieved. In addition, by feeding back the signal of the ultrasonic receiving transducer to the drive unit of the ultrasonic transmitting transducer, a sufficiently accurate measurement system can be realized without the need to correct the beat signal obtained from the laser measurement system. can.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a schematic structural diagram of an acousto-optic element in an embodiment of the present invention.

In FIG. 2, reference numeral 11 denotes an acousto-optic medium, which has two parallel main surfaces, and a light entrance surface and an exit surface that intersect with these main surfaces. This acousto-optic medium 11 is made of, for example, a light-transmitting glass material or a single crystal material. Reference numeral 12 denotes an ultrasonic wave transmission transducer, which is arranged on one main surface of the acousto-optic medium 11, and an input terminal 14 for ultrasonic excitation energy is connected to this via an impedance matching section 13. . Reference numeral 15 denotes an ultrasonic receiving transducer, which is selectively provided on a portion of the other main surface of the acousto-optic medium 11 facing the ultrasonic transmitting transducer 12. 16 is an ultrasonic absorption layer for preventing ultrasonic reflection;
It is provided on the other main surface of the acousto-optic medium 11. Note that this ultrasonic absorbing layer 16 is only intended to absorb the ultrasonic beam 17 from the ultrasonic wave transmitting transducer 12, and is placed over an area where reflection of the ultrasonic beam 17 on the other main surface can be sufficiently prevented. It is provided for. Reference numeral 18 denotes an ultrasonic reception signal output terminal, which is connected to the ultrasonic reception transducer 16 via an impedance matching section 19 . Regarding the impedance matching section 13゜19, if it is not necessary,
Needless to say, it can be omitted.

The operation will be explained below.

First, when ultrasonic excitation energy is injected from the ultrasonic excitation energy input terminal 14, it is converted into a state that is easily absorbed by the ultrasonic wave transmission transducer via the impedance matching section 13 of the ultrasonic wave transmission transducer. Ultrasonic transmitting transducer 12 emits an ultrasound beam 17 into acousto-optic medium 11 . When the incident light 2o is incident on this, a part of the transmitted light 21 is diffracted and a diffracted light 22 whose frequency has been shifted is output. The emitted ultrasonic flux 17 is subjected to disturbance while propagating through the acousto-optic medium 11, and a part of it is received by the ultrasonic receiving transducer 15, and transmitted from the received signal output terminal 18 via the impedance matching section 19. A sound wave monitor signal is output. Further, the remaining ultrasonic flux emitted from the ultrasonic transmitting transducer 12 is absorbed by the ultrasonic absorbing layer 16 and becomes a reflected ultrasonic wave, so that the incident light 20 is not diffracted again.

As described above, according to this embodiment, by providing the ultrasonic receiving transducer, it is possible to monitor the influence of the ultrasonic bundle 17 in the acousto-optic A body. By feeding back to the excitation drive section, it becomes possible to construct an accurate and stable optical frequency shifter.

Effects of the Invention According to the present invention, by providing an ultrasonic receiving transducer on a part of the opposing surface of an ultrasonic transmitting transducer, the state of ultrasonic waves that contribute to optical diffraction in an acousto-optic medium can be monitored in real time. When applying an acousto-optic element to a laser measurement system, etc., the practical effects of improving its accuracy are significant.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the structure of a conventional acousto-optic device, and FIG. 2 is a schematic diagram of the structure of an acousto-optic device according to an embodiment of the present invention. 11...Acousto-optic medium, 12...Ultrasonic transmitting transducer, 15...Ultrasonic receiving transducer, 16...Ultrasonic absorbing layer, 1
8... Received signal output terminal, 19... Impedance matching section. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (1)

[Claims] an acousto-optic medium, an ultrasonic transmission transducer disposed on one principal surface of the acousto-optic medium, and a portion of the other principal surface of the acousto-optic medium parallel to the principal surface on which the ultrasonic transducer is disposed; An acousto-optic element comprising: an ultrasonic receiving transducer; and an ultrasonic absorption layer for preventing ultrasonic reflection provided on the remaining portion of the other surface of the acousto-optic medium.