System and Method of Providing a Thermally Stabilized Fixed Frequency Piezoelectric Optical Modulator

• US 20090001908A1
• Filed: 06/27/2008
• Published: 01/01/2009
• Est. Priority Date: 06/27/2007
• Status: Active Grant

• Current Assignee: Fluke Corporation (Fortive Corp.)
• Original Assignee: Fluke Corporation (Fortive Corp.)
• Inventors: Pint, Charles S., Shubinsky, Gary D.
• Granted Patent: US 8,008,839 B2
• Time in Patent Office: Days
• US Class Current: 318/116
• CPC Class Codes: B06B 1/0603 using a piezoelectric bender, e.g. bimorph
• CPC Class Codes: G02B 26/04 by periodically varying the intensity of light, e.g. using choppers shutters, diaphragms for cameras G03B9/00; devices for eliminating or reducing the effect of flicker in projection systems G03B21/40
• CPC Class Codes: H10N 30/2042 Cantilevers, i.e. having one fixed end
• CPC Class Codes: H10N 30/802 Drive or control circuitry or methods for piezoelectric or electrostrictive devices not otherwise provided for

Abstract

A device for generating controlled vibration in an uncontrolled temperature environment includes a driving circuit that generates a signal having a first frequency and has a temperature-sensitive driving unit, a vibratory element coupled to the driving unit that vibrates at the first frequency according to the generated signal, and a temperature control circuit to control the temperature of the driving unit.

Claims

1. A device for generating controlled vibration, the device comprising:

a driving circuit that generates a signal having a first frequency;

wherein the driving circuit includes a temperature-sensitive driving unit;

a vibratory element coupled to the driving unit that vibrates at the first frequency according to the generated signal; and

a temperature control circuit to control the temperature of the driving unit.

2. The device of claim 1, further comprising an encasement having high thermal conductivity that substantially surrounds the driving unit, wherein the temperature control circuit maintains the encasement at a controlled temperature to thereby control the temperature of the driving unit.

3. The device of claim 2, wherein the encasement is made of copper.

4. The device of claim 1, further comprising:

a temperature sensing circuit that generates a signal indicative of the temperature of the driving unit.

5. The device of claim 4, further comprising a controller coupled to the driving circuit, to the temperature circuit, and to the temperature control circuit;

wherein

the controller controls the driving circuit based on the signal generated by the temperature sensing circuit.

6. The device of claim 4, wherein the temperature sensing circuit includes a thermistor having a margin of error of approximately 0.1°

C. or less.

7. The device of claim 1, wherein the temperature control circuit includes:

a resistor that generates heat when voltage is applied across the resistor; and

an electric switch that controls the resistor by applying voltage to the resistor in a first operational state and not applying voltage to the resistor in a second operational state.

8. The device of claim 1, wherein the driving unit is a piezoelectric transducer including a pair of piezoelectric crystals shaped as substantially flat plates such that the vibratory element resides between the piezoelectric crystals;

and wherein the driving circuit applies opposite voltage polarities to each of the pair of piezoelectric crystals during operation of the device.

9. The device of claim 8, wherein the piezoelectric crystals are manufactured from one of lead-zirconate-titanate (PZT), lead-titanate (PbTiO₂), lead-ziconate(PbZrO₃), or Barium Titanate (BaTiO₃).

10. The device of claim 8, wherein the first frequency is determined according to the formula

F_operational=F₀−

F_offset, wherein

F_operational is the first frequency;

F₀ is the resonant frequency of the driving circuit when the vibratory element is coupled to the driving circuit and associated with an operational temperature; and

F_offset is a value corresponding to a small change in the amplitude of the vibratory element when the driving circuit operates at F_operational.

11. The device of claim 10, wherein F_offset is between 1 Hz and 3 Hz;

and wherein the operational temperature is approximately 65°

C. with a margin of error of 1°

C.

12. A method of vibrating a vibratory element at a controlled frequency, comprising:

obtaining a resonant frequency of a first circuit including a piezeolectric transducer, wherein the vibratory element is coupled to the piezeolectric transducer;

calculating an operational frequency of the first circuit, wherein the operational frequency is distinct from the resonant frequency;

maintaining the piezeolectric transducer within a first temperature range; and

driving the circuit at the operational frequency.

13. The method of claim 12, wherein calculating the operational frequency of the circuit includes subtracting a small offset value from the resonant frequency.

14. The method of claim 13, wherein calculating the operational frequency includes selecting the offset value based on the frequency response characteristic of the first circuit, such that driving the circuit at the operational frequency results in a small change in amplitude of vibration of the vibratory element relative to driving the circuit at the resonant frequency.

15. The method of claim 12, wherein obtaining the resonant frequency of the first circuit includes obtaining the resonant frequency at a temperature within the first temperature range at which the piezeolectric transducer is maintained.

16. The method of claim 12, wherein maintaining the temperature of the piezeolectric transducer within the first temperature range includes:

obtaining a temperature reading indicative of the temperature of the piezoelectric transducer;

comparing the temperature reading to a target temperature value within the first temperature range; and

generating a temperature control signal according to a result of comparing the temperature reading to the temperature value.

17. The method of claim 16, wherein the first circuit operates in an environment associated with a second temperature range;

and wherein the first temperature range is associated with higher temperatures than the second temperature range.

18. The method of claim 16, wherein obtaining the temperature reading includes obtaining the temperature reading from a second circuit including a thermistor.

19. The method of claim 18, wherein comparing the temperature reading to the target temperature value includes:

storing the target temperature value in a memory of a controller coupled to at least the first circuit, the second circuit, and a third circuit including a thermal element; and

wherein

generating the temperature control signal includes generating the temperature signal at the controller to control the thermal element.