JPH05167446A - A/d converter - Google Patents

Abstract

PURPOSE:To provide a stable optical A/D converter against noise or the like. CONSTITUTION:The A/D converter is provided with an optical deflection element 1 having an acousto optic medium 1a made of a single crystal made of a tellurium oxide or a glass and a piezoelectric element 2 propagating an ultrasonic wave into the acousto optic medium 1a, and a voltage controlled oscillator 8 gives a drive signal with a frequency in response to the level of an analog input signal to the piezoelectric element 2 to generate an ultrasonic wave from the piezoelectric element 2 and it is propagated in the acousto optical medium 1a to diffract a laser beam from a laser light source 3. Then a light receiving element 4 receives the deflected light and its output is converted into binary data at a signal conversion circuit such as a comparator encoder 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an A / D converter,
More specifically, the present invention relates to an A / D converter that converts an analog signal into a digital signal by using a light deflection element.

[0002]

2. Description of the Related Art If existing A / D converters are classified based on their basic principles, they are roughly classified into an integration system and a comparison system.

Among these, the integration method includes a VT (voltage-time) conversion type in which a gate time T proportional to the input analog voltage V is generated and generated, and a reference clock is counted only during the period T, and an input analog voltage. There is a VF (voltage-frequency) conversion type in which a pulse number F proportional to V is generated, the gate is opened for a fixed time Tc, and the pulse number is counted.

On the other hand, in comparison, there are a feedback comparison type and a non-feedback comparison type in principle. That is, the feedback comparison type has a D / A converter inside and operates so as to compare the input analog signal with the output of the D / A converter and to make the outputs of the D / A converter coincide. This includes a follow-up comparison type and a successive comparison type.

Further, in the non-feedback comparison type, when digitizing an input analog signal, the level of the analog signal is subdivided into a number sufficient to satisfy the required resolution, and A- is fed-forwardly according to this level. D
It performs conversion, and includes parallel comparison type, continuous comparison type, and serial / parallel comparison type.

[0006]

Each type has its own characteristics, but in any case, since its conversion depends on electric operation, there is a problem that it is susceptible to noise and the like. ..

Under these circumstances, the present invention was made by paying attention to a recently developed optical polarization element, and its purpose is to provide a highly reliable A / A device that is not affected by noise or the like. It is to provide a D converter.

[0008]

In order to achieve the above object, the present invention has an acousto-optic medium made of single crystal such as tellurium dioxide or glass and a piezoelectric element for propagating ultrasonic waves in the acousto-optic medium. A light deflection element, a laser light source for irradiating light toward the acousto-optic medium, a voltage control oscillator for outputting a drive signal corresponding to the magnitude of an analog input signal to the piezoelectric element, and the acousto-optic medium. It is characterized by comprising a plurality of light receiving elements arranged on the side of the outgoing light surface and a signal conversion circuit for receiving an output signal of the light receiving element and outputting a predetermined digital signal corresponding thereto.

[0009]

When a drive signal having a frequency proportional to the magnitude of the analog input signal is applied from the voltage controlled oscillator to the piezoelectric element, the piezoelectric element generates an ultrasonic wave proportional thereto.

By propagating this ultrasonic wave in the acousto-optic medium, the laser beam passing through the medium is diffracted by a predetermined angle, and the emitted light is received by the light receiving element corresponding to the diffraction angle.

That is, the analog input signal is converted into optical angle information. Then, based on the output from the light receiving element, the signal conversion circuit outputs a digital signal corresponding to the analog input signal.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, this A / D converter is equipped with a light deflection element 1 having an acousto-optic effect (for example, a light polarization element EFL-D manufactured by Matsushita Electric Industrial Co., Ltd.). ..

The light deflection element 1 is made of tellurium dioxide (Te).
O ₂ ), lead molybdate (PbMoO ₄ ), or the like, which has an acousto-optic medium 1a made of a single crystal or glass, and a piezoelectric element 2 is integrally attached to a predetermined portion of the acousto-optic medium 1a with an adhesive or the like. ing.

On the incident light surface side of the acousto-optic medium 1a, a laser light source 3 which irradiates light toward the acousto-optic medium 1a.
Is provided. Further, a plurality of light receiving elements 4 and a signal conversion circuit 5 paired with the light receiving elements 4 are arranged on the emission light surface side.

A voltage controlled oscillator (VCO) 8 for driving the piezoelectric element 2 is provided, and an analog input signal to be converted is added to this voltage controlled oscillator 8.

Referring to FIG. 2, a photodiode is used as the light receiving element 4 in this embodiment, and the signal conversion circuit 5 is composed of a comparator 6 and an encoder 7.

Here, n photodiodes 4a-4
If n is provided, the corresponding n
A number of comparators 6a-6n are connected to each.

That is, the photodiodes 4a to 4n are connected to the non-inverting terminals of the comparators 6a to 6n, respectively, and the reference power supply 9 for setting the threshold voltage Vr is commonly connected to the inverting terminals thereof.

A signal "0" or "1" is output from each of the comparators 6a to 6n in accordance with the light receiving state of each of the photodiodes 4a to 4n, and the signal is output by the encoder 7.
Is converted to binary data.

For example, when there are 16 photodiodes and 16 comparators, the decoder 7 converts 16 decimal data into 4-bit binary data. Similarly, when there are 32 photodiodes and 32 comparators, the decoder 7 will convert 32 decimal data into 5-bit binary data.

An example of such a decimal-binary conversion circuit is a priority encoder SN74148 or SN74LS manufactured by Texas Instruments Incorporated.
148 and the like are used alone or connected in series.

When an analog input signal is applied to the voltage controlled oscillator 8, the voltage controlled oscillator 8 outputs a drive signal having a frequency proportional to the magnitude of the input signal to the piezoelectric element 2. As a result, an ultrasonic wave that is proportional to the frequency of the drive signal is generated from the piezoelectric element 2, and the ultrasonic wave propagates in the acousto-optic medium 1a, whereby the laser light emitted from the laser light source 3 is diffracted. It is deflected to a predetermined angle.

The deflected light is, for example, the photodiode 4b.
If the light is received at, the diode 4b becomes conductive,
A voltage of + V is applied to the non-inverting terminal of the comparator 6b.

As a result, the voltage + V of the comparator 6b is compared with the threshold voltage Vr supplied from the reference power source 9, and if + V> Vr, the output of the comparator 6b becomes "1". By the way, since the outputs of the other comparators are “0”, the encoder 7 has (01
A code signal representing a decimal number such as 00 ... 0) is input, and the corresponding encoder 7 outputs, for example, 4-bit binary data corresponding thereto.

Here, for example, when the polarized light of the laser is incident on two adjacent photodiodes, the output of the comparator that exceeds the threshold voltage Vr becomes "1".

Although the photodiode array is used as the light receiving element 4 in the above embodiment, it is replaced by C
A CD or the like may be applied. Further, glass fibers may be bundled at a high density on the light receiving surface, and the glass fibers may be deformed so as to guide the laser light to a light receiving element such as a photodiode.

On the other hand, in the above embodiment, the deflected light of the laser is received by the light receiving element 4. However, instead of the light receiving element, a predetermined number of condenser lenses are arranged and the light is transmitted by an optical fiber. A spectroscope is configured by taking out the analog voltage and changing the analog voltage input to the voltage controlled oscillator 8 in steps.

[0028]

As described above, according to the present invention, since the analog-to-digital conversion is optically performed, an insulated A / D converter that is stable against noise is provided. To be done.

Further, the light deflection element, the light receiving element, and the signal conversion circuit can be integrated to further reduce the size.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of an A / D converter according to the present invention.

FIG. 2 is a circuit diagram for explaining a light receiving element and a signal conversion circuit shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical deflection element 1a Acousto-optic medium 2 Piezoelectric element 3 Laser light source 4 Light receiving element 5 Signal conversion circuit 6 Comparator 7 Encoder 8 Voltage controlled oscillator 9 Reference power source

Claims (1)

[Claims] 1. An acousto-optic medium made of a single crystal such as tellurium dioxide or glass and a light deflection element having a piezoelectric element for propagating ultrasonic waves in the acousto-optic medium, and irradiating the acousto-optic medium with light. A laser light source, a voltage-controlled oscillator that outputs a drive signal corresponding to the magnitude of an analog input signal to the piezoelectric element, a plurality of light-receiving elements arranged on the emission light surface side of the acousto-optic medium, and the same light-receiving element. An A / D converter, comprising: a signal conversion circuit that receives an output signal of an element and outputs a corresponding predetermined digital signal.