Photoelectric sensor unit

• US 20030136895A1
• Filed: 01/10/2003
• Published: 07/24/2003
• Est. Priority Date: 01/15/2002
• Status: Active Grant

• Current Assignee: Keyence Corporation (Keyence)
• Original Assignee: Keyence Corporation (Keyence)
• Inventors: Ogawa, Yuji
• Granted Patent: US 6,891,142 B2
• Time in Patent Office: Days
• US Class Current: 250/205
• CPC Class Codes: G01J 1/32 adapted for automatic variation of the measured or reference value regulation of light intensity G05D25/00

Abstract

A photoelectric sensor unit comprises a light emitting section for emitting light to a detection area, a light receiving section for receiving light from the detection area, and a signal processing section for amplifying and processing an electric signal corresponding to the light reception amount output from the light receiving section. A four-element, high-brightness type LED is used as a light emitting element forming a part of the light emitting section and a drive circuit comprises an automatic control circuit for reducing fluctuation in the light emission amount relative to change in the ambient temperature of the LED.

Claims

1. A photoelectric sensor unit comprising:

a light emitting section for emitting light to a detection area, the light emitting section including a light emitting element having a four-element, high-brightness type LED;

a light receiving section for receiving light from the detection area;

a signal processing section for amplifying and processing an electric signal corresponding to a light reception amount output from said light receiving section; and

an automatic control circuit for reducing fluctuation in a light emission amount of the light emitting element relative to change in ambient temperature of the LED.

2. The photoelectric sensor unit as claimed in claim 1, wherein the four-element, high-brightness type LED has pn junction of a semiconductor consisting of AlGaInP and comprises an optically transparent substrate replacing a substrate of GaAs.

3. The photoelectric sensor unit as claimed in claim 2, wherein the optically transparent substrate is a GaP substrate.

4. The photoelectric sensor unit as claimed in claim 2, wherein the optically transparent substrate is an optically transparent sapphire substrate.

5. The photoelectric sensor unit as claimed in claim 1, wherein the four-element, high-brightness type LED has pn junction of a semiconductor consisting of AlGaInP and comprises a layer containing a metal thin film having a high light reflection factor replacing a substrate of GaAs.

6. The photoelectric sensor unit as claimed in claim 1, wherein the automatic control circuit comprises an APC circuit having a monitor light receiving element for receiving light from the light emitting element to monitor the light emitting element, the APC circuit controlling a drive current of the light emitting element based on an electric signal corresponding to a light reception amount provided from the monitor light receiving element.

7. The photoelectric sensor unit as claimed in claim 6, wherein the automatic control circuit further comprises an ACC circuit for controlling the drive current of the light emitting element based on a voltage signal fed back from a resistor inserted in a drive circuit of the light emitting element and wherein when an operation of the APC circuit is stopped, the ACC circuit is operated.

8. The photoelectric sensor unit as claimed in claim 1, further comprising:

a digital display for displaying a numeric value corresponding to the light reception amount output from said signal processing section.

9. The photoelectric sensor unit as claimed in claim 1, further comprising:

a light emitting optical fiber having a base end part connected to said light emitting section; and

a light receiving optical fiber having abase end part connected to said light receiving section,

wherein light emitted from the light emitting element is made incident directly on a base end face of the light emitting optical fiber.