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Introduction & Features - Photoelectric Sensors

Introduction &
Features

Classification
methods &
Classification

Precautions for
prorer use

Principles of
particular optical
sensing systems

Functions

Introduction

Principles of operation

Photoelectric sensor is a generic name for sensors which detect an object by using light. The optical signal transmitted from the emitting part of the sensor is modified by being reflected, transmitted, absorbed, etc., by the sensing object and is then detected by the receiving part of the sensor to generate a corresponding output signal. Further, it can also be a sensor which detects light radiated from the sensing object to generate an output signal.
Fiber sensors and laser sensors are also one type of photoelectric sensor.

Thru-beam type

Retroreflective type

Reflective type

Emitting method

Pulse-modulated

Most of the photoelectric sensors emit a beam which is pulse-modulated.
In this method, a strong optical signal of fixed width is emitted at a fixed time interval.
This helps the receiver to distinguish the signal from extraneous light and to achieve a long sensing range.

Unmodulated

The high-speed fiber sensor FX2-A3R and the micro photoelectric sensor PM-64/24/44/54 series use an unmodulated beam.
In this method, the beam is emitted constantly at a fixed intensity. This enables high-speed response, although the sensors are a little susceptible to extraneous light as compared to the sensors using a modulated beam.

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Features

Non-contact detection

Detects an object without contact.
Non-contact sensing ensures longer life for the sensor and absolutely no damage to the object.

Long sensing range

The thru-beam type with a maximum sensing range of 50 m 164.042 ft (RX-M50), and the diffuse reflective type with a maximum sensing range of 5 m 16.404 ft (PX-26) are available. The long sensing range make the sensors suitable for a variety of applications.

Various objects detectable

The sensors can detect objects of any material provided they affect the optical beam.

Short response time

The use of an optical beam for detection and complete electronic circuitry makes the sensors respond so quickly that they can be easily used on a high-speed production line.

Color identification

This is a special feature of photoelectric sensors, which use light for detection.
Since the reflection and the absorption characteristics vary with the object color for a specified incident optical wavelength, various colors can be detected as the difference in optical intensity.

High accuracy detection

Advanced optical system and electronic circuit technology have achieved a sensing accuracy of up to 20 μm 0.787 mil (SH-82R).

*	Photoelectric sensors have the drawback that if the lens surface is covered with dust or dirt and light transmission is obstructed, detection may not be possible.

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