Photoelectric sensor for detecting presence/absence of object

• US 7,247,834 B2
• Filed: 10/15/2003
• Issued: 07/24/2007
• Est. Priority Date: 11/08/2002
• Status: Expired due to Fees

• Current Assignee: Hosiden Corporation
• Original Assignee: Hosiden Corporation
• Inventors: Fujita, Kouji
• Primary Examiner(s): Epps; Georgia
• Assistant Examiner(s): ELLIS, SUEZU Y
• Application Number:
  US10/684,484
• Publication Number:
  US 20040089791A1
• Time in Patent Office: 1,378 Days
• Field of Search: 250/221, 250/222.1, 250/205, 250/559.4, 250/341.1, 250/341.7, 250/349, 250/342, 250/353, 340555-557
• US Class Current: 250/221
• CPC Class Codes: G01V 8/10 Detecting, e.g. by using light barriers by reflection from the object G01S17/00

Abstract

An object of the present invention is to enable the detection of the presence/absence of an object over a plurality of detection areas without using a plurality of light-receiving devices and light-emitting devices. A sensor detects the presence/absence of an object in a detection area where a light-emitting area of a light-emitting device and a light-receiving area of a light-receiving device are overlapped with each other, and includes: a power supply unit that outputs a driving current I of the light-emitting device such that its current value is variable; a control unit that has the function of controlling the power supply unit to change in magnitude of the driving current I of the light-emitting device, and determining the presence/absence of an object based on an output from the light-receiving device to output the result of determination as a detection signal; and an output signal 50 that converts the detection signal into an analog signal to output the converted signal as a signal α.

Claims

1. A photoelectric sensor for detecting the presence/absence of an object in a plurality of detection areas where a plurality of light-emitting areas of a light-emitting device and a single light-receiving area of a light-receiving device are overlapped with each other, the photoelectric sensor comprising:

a power supply unit for outputting a plurality of different values of driving current to the light-emitting device; and

a control unit for outputting a plurality of different control signals to the power supply unit so as to make the power supply unit output said plurality of values of driving current, wherein

during a period of outputting one of said plurality of control signals, the control unit determines whether or not an output level of said light-receiving device is equal to or larger than a reference value, and if the output level is determined to be equal to or larger than the reference value, the control unit determines that an object is present in one of the detection areas where one of the light-emitting areas and the light-receiving area are overlapped with each other and outputs a digital or analog detection signal.

2. The photoelectric sensor according to claim 1, wherein the control unit is configured to have the function of repeatedly changing said plurality of control signals in a predetermined pattern.

3. A photoelectric sensor for detecting the presence/absence of an object in a detection area where a light-emitting area of a light-emitting device and a light-receiving area of a light-receiving device are overlapped with each other, the photoelectric sensor being configured to allow the light-emitting device to emit light, compare an output level of the light-receiving device with a plurality of reference values different from one another, and output the result of comparison as a digital or analog detection signal in order to detect the presence/absence of the object over a plurality of detection areas, wherein in order to produce the detection signals based on the output levels of the light-receiving device, said plurality of reference values are repeatedly changed in a predetermined pattern and compared with the output level and the results of comparison are outputted in sequence.