Ultrasonic lens cleaning system with foreign material detection

Patent metadata

Field	Value
Publication number	US-11237387-B2
Application number	US-201715583057-A
Country	US
Kind code	B2
Filing date	May 1, 2017
Priority date	Dec 5, 2016
Publication date	Feb 1, 2022
Grant date	Feb 1, 2022

Abstract

Disclosed examples include lens cleaning systems, drivers and operating methods, including a transducer mechanically coupled to a lens, a driver to provide an oscillating drive signal to the transducer and a controller to control the drive signal frequency to vibrate the lens at frequencies in a range of interest. The controller determines a measured resonant frequency of the lens cleaning system in the range of interest according to a transducer feedback signal and selectively performs a lens cleaning operation if the measured resonant frequency differs from a baseline resonant frequency of the lens cleaning system for a clean lens.

First claim

The following is claimed:

1. Apparatus comprising:
a driver having a driver output adapted to be coupled through a transducer to a lens, the driver including:
a feedback circuit having a feedback input and a feedback output, the feedback input coupled to the driver output, and the feedback circuit configured to provide a feedback signal at the feedback output responsive to the feedback input, the feedback signal representing an electrical property of the transducer; and
a controller coupled between the feedback output and the driver output, the controller configured to:
provide an oscillating drive signal at the driver output for causing the transducer to vibrate the lens at frequencies within a frequency range;
responsive to the feedback signal, determine a resonant frequency of the lens within the frequency range; and
responsive to a difference between the determined resonant frequency and a baseline resonant frequency of the lens, selectively provide the drive signal at the driver output for causing the transducer to vibrate the lens in a lens cleaning operation.

2. The apparatus of claim 1 , wherein:
the feedback signal includes: a current feedback signal representing a current flowing in the transducer; and a voltage feedback signal representing a voltage of the transducer; and
the controller is configured to:
while causing the transducer to vibrate the lens at the frequencies within the frequency range, determine frequency response values responsive to the current feedback signal and the voltage feedback signal;
responsive to the frequency response values, determine the resonant frequency of the lens within the frequency range;
compute an absolute value of the difference between the determined resonant frequency and the baseline resonant frequency; and
determine whether the lens has a threshold amount of contaminants responsive to whether the absolute value of the difference is greater than a non-zero frequency threshold value.

3. The apparatus of claim 2 , wherein the controller is configured to:
determine a frequency response profile of the lens responsive to the frequency response values; and
determine the resonant frequency as a local minima or a local maxima of the frequency response profile.

4. The apparatus of claim 2 , wherein the frequency threshold value is a first frequency threshold value, and the controller is configured to determine a cleaning phase, a voltage level of the cleaning phase, a frequency sweep range of the cleaning phase, and a frequency sweep rate of the cleaning phase, responsive to the absolute value of the difference and to a second frequency threshold value, the second frequency threshold value being greater than the first frequency threshold value.

5. The apparatus of claim 1 , wherein the controller is configured to selectively provide the drive signal at the driver output for causing the transducer to vibrate the lens in the lens cleaning operation using a cleaning power level or a cleaning duration, responsive to the determined resonant frequency.

6. The apparatus of claim 5 , wherein the controller is configured to:
while causing the transducer to vibrate the lens at the frequencies within the frequency range, determine frequency response values responsive to the feedback signal;
determine a frequency response profile of the lens responsive to the frequency response values; and
determine the resonant frequency as a local minima or a local maxima of the frequency response profile.

7. The apparatus of claim 1 , wherein the controller is configured to:
while causing the transducer to vibrate the lens at the frequencies within the frequency range, determine frequency response values responsive to the feedback signal;
determine a frequency response profile of the lens responsive to the frequency response values; and
determine the resonant frequency as a local minima or a local maxima of the frequency response profile.

8. The apparatus of claim 1 , wherein the controller is configured to:
while causing the transducer to vibrate the lens at the frequencies within the frequency range, determine frequency response values responsive to the feedback signal for a clean lens;
determine a baseline frequency response profile of the lens responsive to the frequency response values;
store the baseline frequency response profile; and
identify the baseline resonant frequency as a local minima or a local maxima of the baseline frequency response profile.

9. The apparatus of claim 1 , wherein the driver output, the feedback circuit, and the controller are part of a single integrated circuit.

10. A lens cleaning system, comprising:
a lens;
a transducer mechanically coupled to the lens;
a driver having a driver output coupled to the transducer, the driver including:
a feedback circuit having a feedback input and a feedback output, the feedback input coupled to the driver output, and the feedback circuit configured to provide a feedback signal at the feedback output responsive to the feedback input, the feedback signal representing an electrical property of the transducer; and
a controller coupled between the feedback output and the driver output, the controller configured to:
provide an oscillating drive signal at the driver output for causing the transducer to vibrate the lens at frequencies within a frequency range;
responsive to the feedback signal, determine a resonant frequency of the lens within the frequency range; and
responsive to a difference between the determined resonant frequency and a baseline resonant frequency of the lens, selectively provide the drive signal at the driver output for causing the transducer to vibrate the lens in a lens cleaning operation.

11. The lens cleaning system of claim 10 , wherein:
the feedback signal includes: current feedback signal representing a current flowing in the transducer; and a voltage feedback signal representing a voltage of the transducer; and
the controller is configured to:
while causing the transducer to vibrate the lens at the frequencies within the frequency range, determine frequency response values responsive to the current feedback signal and the voltage feedback signal;
responsive to the frequency response values, determine the resonant frequency of the lens within the frequency range;
compute an absolute value of the difference between the determined resonant frequency and the baseline resonant frequency; and
determine whether the lens has a threshold amount of contaminants responsive to whether the absolute value of the difference is greater than a non-zero frequency threshold value.

12. The lens cleaning system of claim 11 , wherein the controller is configured to:
determine a frequency response profile of the lens responsive to the frequency response values; and
determine the resonant frequency as a local minima or a local maxima of the frequency response profile.

13. The lens cleaning system of claim 11 , wherein the frequency threshold value is a first frequency threshold value, and the controller is configured to determine a cleaning phase, a voltage level of the cleaning phase, a frequency sweep range of each cleaning phase, a frequency sweep rate of the cleaning phase, and a duration of the cleaning phase, responsive to the absolute value of the difference and to a second frequency threshold value, the second frequency threshold value being greater than the first frequency threshold value.

14. The lens cleaning system of claim 10 , wherein the controller is configured to selectively provide the drive signal at the driver output for causing the transducer to vibrate the lens in the le

Assignees

• Texas Instruments Inc

Inventors

• Magee David Patrick
• Fedigan Stephen John

Classifications

• G02B13/06

  Panoramic objectives; So-called "sky lenses" {including panoramic objectives having reflecting surfaces} · CPC title

• G02B13/16

  for use in conjunction with image converters or intensifiers {, or for use with projectors, e.g. objectives for projection TV} · CPC title

• G02B27/0006 Primary

  with means to keep optical surfaces clean, e.g. by preventing or removing dirt, stains, contamination, condensation (G02B1/18 takes precedence; cleaning in general B08B) · CPC title