Alignment indicator for photoelectric sensors

• US 6,285,017 B1
• Filed: 06/18/1999
• Issued: 09/04/2001
• Est. Priority Date: 06/18/1999
• Status: Expired due to Term

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Brickell, Christopher Gavin
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Punnoose, Roy M.
• Application Number:
  US09/336,519
• Time in Patent Office: 809 Days
• Field of Search: 250/221, 250/214.A, 250/214.AL
• US Class Current: 250/214.00A
• CPC Class Codes: G01S 7/486 Receivers
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

A mechanism for indicating the degree of alignment of a photoelectric sensing system produces a pulse width modulated signal in response to the intensity of light received by the sensing system. That signal has pulses which occur at a fixed frequency, but which vary in duration in response to the received light intensity. The pulse width modulated signal drives an indicator, such as a sound or light emitter. With this technique, the output of the indicator is pulse width modulated to indicate the intensity of the received light and thus the degree of alignment of the sensing system.

Claims

1. A photoelectric detecting and indicating apparatus, comprising:

a light detector to receive light and respond by producing a detector signal indicative of intensity of the received light;

a control circuit connected to receive the detector signal and operative in response thereto to produce an output signal having a constant frequency and pulses which vary in duration with the intensity of the received light; and

an indicator connected to receive the output signal and operative in response thereto to produce a repetitive, human perceptible indication whereby the intensity of the received light may be discerned.

2. The apparatus as recited in claim 1 wherein the light detector comprises at least one photodetector in series with an amplifier circuit which operates to increase the detector signal to an operable level.

3. The apparatus as recited in claim 1 wherein the indicator comprises a light emitter which flashes at constant frequency with each flash having a length indicative of the intensity of the received light.

4. The apparatus as recited in claim 1 wherein the indicator is a light emitter which illuminates in response to the output signal, whereby the intensity of the received light, and thus alignment of the photoelectric sensor, is indicated by luminance of the light emitter.

5. The apparatus as recited in claim 1 wherein the indicator is a sound emitter which produces audible pulses at constant frequency with each pulse having a length indicative of the intensity of the received light.

6. The apparatus as recited in claim 1 wherein the control circuit comprises a pulse width modulator operable in response to the intensity signal to produce the output signal.

7. The apparatus as recited in claim 1 further comprising an emitter to produce a light beam which impinges the light detector.

8. The apparatus as recited in claim 1 further comprising an emitter to produce a light beam which impinges the light detector, wherein the emitter is operated by the control circuit.

9. A photoelectric sensor having an alignment indicating mechanism, the photoelectric sensor comprising:

a light detector to receive light pulses and produce an detector signal indicative of intensity of the received light pulses;

an amplifier connected to the light detector to increase the detector signal to an operable level;

a control circuit connected to the amplifier and responsive to the increased detector signal to produce an output signal having a constant frequency and pulses which vary in duration with the intensity of the received light; and

an indicator connected to the control circuit and producing a human perceptible indication upon activation by the pulses of the output signal, whereby the intensity of the received light and thus alignment of the photoelectric sensor.

10. The photoelectric sensor as recited in claim 9 wherein the light detector comprises at least one photodetector operative to produce a modulated intensity signal, the amplitude of which is indicative of the intensity of the light pulses received.

11. The photoelectric sensor as recited in claim 9 wherein the indicator comprises a light emitter.

12. The photoelectric sensor as recited in claim 9 wherein the control circuit comprises a pulse width modulator that is operable in response to voltage of the increased intensity signal to produce the output signal having a constant frequency and pulses which vary in duration with the voltage of the increased intensity signal.

13. An alignment indicating apparatus for a photoelectric sensor, wherein the alignment indicating apparatus comprises:

a light detector for receiving light pulses from the photoelectric sensor and producing a detector signal indicative of intensity of the received light pulses;

an amplifier connected to the light detector to increase the detector signal to an operable level;

a control circuit connected to the amplifier to receive an amplified detector signal and operative in response thereto to produce an output signal which has a constant frequency and has pulses which vary in duration with the intensity of the received light; and

an indicator connected to the control circuit and illuminating in response to the output signal, whereby the intensity of the received light, and thus alignment of the photoelectric sensor, is indicated by luminance of the indicator.

14. The apparatus as recited in claim 13 wherein the light detector comprises at least one photodetector in series with an amplifier which operates to increase the detector signal to an operable level.

15. The apparatus as recited in claim 13 wherein the output comprises a PWM generating pulses having a duration at constant frequency that varies in response to the intensity signal.

16. The apparatus as recited in claim 13 wherein the control circuit comprises a filter that is operative in response to the detector signal to produce a DC voltage which is converted to a current level by a voltage to current converter.

17. The apparatus as recited in claim 16 wherein luminance of the indicator is in response to the current.

18. The apparatus as recited in claim 13 wherein the indicator comprises a light emitting diode producing a luminance indicative of the intensity of the received light.