Optical detection apparatus for detecting light interruption

• US 5,698,845 A
• Filed: 04/23/1996
• Issued: 12/16/1997
• Est. Priority Date: 05/23/1995
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Stanley Electric Company Limited
• Inventors: Hibiya, Kazuyoshi, Kodama, Tomoaki
• Primary Examiner(s): Evans, F. L.
• Application Number:
  US08/636,394
• Time in Patent Office: 602 Days
• Field of Search: 356/375, 250/221, 250/221.1, 250/214 B
• US Class Current: 250/221
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

Abstract

The light selected by a selection circuit 3 at a light emitting side and emitted from a light emitting element 1 such as a LED is converted to a specifically modulated light by an oscillation circuit 11. The light received by a light receiving element 2 such as a phototransistor at the receiving side is amplified by an amplifier circuit 6, and a detection circuit 12 detects whether a specifically modulated light is received. The H/L detection circuit 13 determines the presence/absence of a light interruption to produce a signal of either H (high level) or L (low level). Also, the signal from the oscillator 11 of the emission side is received by the receiving side and compared with the received signal to determine whether the same signal as emitted from the emitting element has been actually received.

Claims

1. An optical detection apparatus for detecting light interruption comprising;

a light emitting element;

a modulation circuit having an output for causing said light emitting element to emit a modulated light output signal comprising a first plurality of pulses of a given first modulation waveform;

a light receiving element for receiving said modulated light output signal and for producing an output in response to said received modulated light output signal, said element output comprising a second plurality of pulses having a second given modulation waveform corresponding to the first modulation waveform of said first plurality of pulses;

a detection circuit for detecting the outputs of said modulation circuit and the light receiving element including means for determining the correspondence of the light output signal to that of the element output and for producing a further output signal having a first value manifesting the presence of said received modulated light and a second value different than the first value manifesting interruption of said received light;

wherein the presence of a light interruption between said light emitting element and said light receiving element is determined on the basis of the value of the output signal of the detection circuit.

2. An optical detection apparatus according to claim 1, wherein said modulation circuit includes means for causing said light emitting element to emit a modulated light modulated by a frequency higher than twice that of a commercial alternating current voltage supply.

3. An optical detection apparatus comprising;

a light emitting element;

an oscillator circuit for generating an output signal comprising a first plurality of pulses of a first frequency and pulse width and for causing said light emitting element to emit a light signal manifesting said output signal;

a light receiving element for receiving and responsive to said light signal for producing a further output signal corresponding to the oscillator circuit output signal; and

sensor means for comparing the further output signal of said light receiving element and of the output signal of said oscillator circuit for determining the presence of a light interruption between said light emitting element and said light receiving element.

4. An optical detection apparatus according to claim 3, wherein said sensor means comprising:

a synchronizing circuit for synchronizing the output signal of said oscillator circuit with an output signal of said light receiving element; and

a detection circuit for comparing said synchronized output signals.

5. A method of optical detection comprising:

emitting modulated light from a light emitting element, said emitted light being generated from a given first modulated waveform output signal comprising a first plurality of pulses having a pulse width and frequency;

receiving the emitted modulated light with a light receiving element and generating from the received light a further modulated waveform output signal comprising a further plurality of pulses having a second pulse width and frequency;

comparing the first and further modulated waveform output siqnals correspondinq to said emitted light and received light; and

from the comparing, determining the presence of light interruption between said light emitting element and said light receiving element.

6. A method according to claim 5, wherein said light emitting step includes emitting a modulated light modulated by a frequency higher than that of a commercial alternating power supply.