Photomicrosensor Basics: Introduction

What is a Photomicrosensor?

Photomicrosensor is a term that is exclusive to OMRON. Generally, Photomicrosensors are called photointerrupters. Photomicrosensors are compact optical sensors that sense objects or object positions with an optical beam. The transmissive and reflective Photomicrosensors are typical configurations.

Transmissive Photomicrosensors (photointerrupters) incorporate an emitter and a detector that face each other as shown in Figure 1. When an object is located in the sensing position between the emitter and the detector, the object intercepts the optical beam of the emitter, thus reducing the amount of optical energy reaching the detector.

Reflective Photomicrosensors incorporate an emitter and a detector as shown in Figure 2. When an object is located in the sensing area of the sensor, the object reflects the optical beam of the emitter, thus increasing the amount of optical energy reaching the detector.

Figure 1. Transmissive Photomicrosensor

Figure 2. Reflective Photomicrosensor

Photomicrosensor Types & Classifications

Photomicrosensor Structures & Principles

Transmissive (slotted) Photomicrosensors (photointerrupters) detect the presence of objects as they pass through the slot by interrupting the emitter’s optical beam after it passes through an aperture. This sensor design is ideal for small object detection applications and can facilitate accurate position sensing.

A reflective Photomicrosensor detects the presence and absence of objects but also can detect printed marks on boards (papers). This type is effective for realizing a low-profile design of a device / equipment.

Here are the structural differences and principles of transmissive (slot) and reflective Photomicrosensors.

Transmissive (Photointerrupter)

Objects are sensed as the light beam is blocked by an object.

Stable sensing of opaque objects
High accuracy in positioning

Reﬂective (Photoreﬂector)

Objects are sensed by the reflected light on the object.

Photomicrosensor Connection / Mounting

Choose from multiple mounting styles, including PCB Mount, Snap-In Panel Mount and Screw Mount.
There are also multiple choices for connecting the Photomicrosensors to a circuit: Surface Mount PCB and Through-Hole PCB terminations, plus versions with Lead Wires and Connectorized versions are available.

Photomicrosensors