Photoelectric Sensors

Explanation of Terms

Application and Data

(1)Relationship of Lens Diameter and Sensitivity to the Smallest Detectable Object

With a Through-beam Sensor, the lens diameter determines the size of the smallest object that can be detected.

With a Through-beam Sensor, a small object can be more easily detected midway between the Emitter and the Receiver that it can be off center between the Emitter and Receiver.

As a rule of thumb, an object 30% to 80% of the lens diameter can be detected by varying the sensitivity level.

Check the Ratings and Specifications of the Sensor for details.

The size given for the smallest object that can be detected with a Reflective Photoelectric Sensor is the value for detection with no objects in the background and the sensitivity set to the maximum value.

(2) Detecting Height Differences

Selecting Sensors Based on Detectable Height Differences and Set Distances (Typical Examples)

(3) MSR (Mirror Surface Rejection) Function

Principles

This function and structure uses the characteristics of the Retroreflector and the polarizing filters built into the Retro-reflective Sensors to receive only the light reflected from the Retroreflector.

The waveform of the light transmitted through a polarizing filter in the Emitter changes to polarization in a horizontal orientation.

The orientation of the light reflected from the triangular pyramids of the Retroreflector changes from horizontal to vertical.

This reflected light passes through a polarizing filter in the Receiver to arrive at the Receiver.

Purpose

This method enables stable detection of objects with a mirror-like surface.
Light reflected from these types of objects cannot pass through the polarizing filter on the Receiver because the orientation of polarization is kept horizontal.

Examples

A sensing object with a rough, matte surface (example (2)) can be detected even without the MSR function. If the sensing object has a smooth, glossy surface on the other hand (example (3)), it cannot be detected with any kind of consistency without the MSR function.

Caution

Stable operation is often impossible when detecting objects with high gloss or objects covered with glossy film. If this occurs, install the Sensor so that it is at an angle off perpendicular to the sensing object.

Retro-reflective Sensors with MSR function

Note:When using a Sensor with the MSR function, be sure to use an OMRON Reflector

Retro-reflective Sensors without MSR Function

When detecting a glossy object using a Retro-reflective Sensor without the MSR function, mount the Sensor diagonally to the object so that reflection is not received directly from the front surface.

(4) Surface Color and Light Source Reflectance

Surface Color Reflectance

Reflectance of Various Colors at Different Wavelengths of Light

Identifiable Color Marks

Applicable Sensor Light Colors: : Red light source : Green light source : Blue light source
Sensors with a RGB light source can detect all combinations.

These figures represent typical examples of ratios for light reflected by the back and mark.

Sensor light color	Product classification	Model
Red light source	Optical Fiber Sensors	E3X-HD
		E3X-SD
		E3X-NA
		E3X-DA-S
		E3X-MDA
	Separate Amplifier Sensors	E3C-VS3R E3C-VM35R E3C-VS7R
Blue light source	Optical Fiber Sensors	E3X-DAB-S
Green light source	Optical Fiber Sensors	E3X-DAG-S
		E3X-NAG
	Separate Amplifier Sensors	E3C-VS1G
White light source	Optical Fiber Sensors	E3X-DAC-S

(5) Self-diagnosis Functions

The self-diagnosis function checks for margin with respect to environmental changes after installation, especially temperature, and informs the operator of the result through indicators and outputs. This function is an effective means of early detection of product failure, optical axis displacement, and accumulation of dirt on the lens over time.

Principles

These functions alert the operator when the Sensor changes from a stable state to an unstable state. The functions can be broadly classified into display functions and output functions.

Stability Indicator (green LED)
The amount of margin with respect to environmental changes (temperature, voltage, dust, etc.) after installation is monitored by the self-diagnosis function and indicated by an indicator. (Illuminates steadily when there are no problems.)

Operation Indicator (Orange LED)
Indicates the output status.

The margin is indicated by an indicator light, and the state is output to alert the operator.

Purpose

Self-diagnosis functions are effective in maintaining stable operation, alerting the operator to displacement of the optical axis, dirt on the lens (Sensor surface), the influence from the floor and background, external noise, and other potential failures of the Sensor.

Example: Light-ON Operation

Applicable Models

Safety Standards for Laser Beams

Safety Standards for Laser Beams

The laser beams that are emitted from lasers have a high power density and can cause damage to the human body, even if the quantity of light is small. In Japan, in order to prevent injury to users of laser products, a Japanese Industrial Standard, Radiation Safety Standards for Laser Products (JIS C 6802), has been established. It is based on the corresponding International Electrotechnical Commission (IEC) standard.
The JIS C 6802 standard divides laser products into different classes according to the degree of the hazard, and specifies the required safety measures for each class.
An overview of the classifications is given on the right.

Definitions of Laser Classifications

The safety standards for laser beams are different for each country and region. The definitions for laser classifications in Europe and the United States are described below.

Europe (EN 60825-1)

The classification standards set forth in European Standard EN 60825-1:2007 is consistent with the JIS standard C6802:2005.
You should always check the original text of the standard when trying to attain conformance.

USA

* The following information was edited by OMRON based on the actual standard. OMRON assumes no responsibility for this information. You should always check the original text of the standard before implementing an actual application.

Measures for the Prevention of Damage due to Laser Beams

Regarding labor using lasers, the Industrial Safety and Health Law sets out specific details of safety measures for laser equipment that are classified as Class 3R or higher in Measures for the Prevention of Damage due to Laser Beams. The following table gives the criteria for the measures by each class.

Standards for Europe

Requirements for Laser-equipment Manufacturers

Europe (EN 60825-1)

* The following information was edited by OMRON based on the actual standard. OMRON assumes no responsibility for this information. You should always check the original text of the standard before implementing an actual application.

Note:
1. The above table is a summarization of the basic requirements. You should always check the original text of the standard to understand and apply the actual standards.
2. Laser equipment used for healthcare applications are subject to IEC 60601-2-22.
3. This is the allowed accessible emission limit (AEL) for the corresponding laser class. Referenced standards: ANSI Z136.1-1993, Section 2.

Precautions to Laser-equipment Users

Europe (EN 60825-1)

* The following information was edited by OMRON based on the actual standard. OMRON assumes no responsibility for this information. You should always check the original text of the standard before implementing an actual application.

*1. The above table is a summarization of the basic requirements. You should always check the original text of the standard to understand and apply the actual standards.
*2. This refers to Class 1M laser products that do not conform to condition 1 in Table 10 of the standard. Not required for Class 1M laser products that do not conform to condition 2 in Table 10 of the standard. Refer to the original text of the standard for details.
*3. This refers to Class 2M laser products that do not conform to condition 1 in Table 10 of the standard. Not required for Class 2M laser products that do not conform to condition 2 in Table 10 of the standard. Refer to the original text of the standard for details.

Standards for the USA

Requirements for Laser-equipment Manufacturers

USFDA (Compliance Guide for Laser Equipment, 1985, 21 CFR 1040.10)

* The following information was edited by OMRON based on the actual standard. OMRON assumes no responsibility for this information. You should always check the original text of the standard before implementing an actual application.

*1. Depends on accessible emission level during operation.
*2. Required for all classes access by personnel to Class I or higher levels of laser emissions is not required for the product to deliver its full performance.
*3. Required if access by personnel is not required at all times when the protective housing must be left open for operation or maintenance.
*4. The level of necessity for interlocks depends on the internal radiation of the laser class.
*5. The indications depend on the laser emission level and wavelength inside the protective housing.
*6. Warning explanatory label.
*7. "CAUTION" logotype.
*8. When the term "Required" is used, it refers to the act of measuring the laser emission level with the intent of irradiating the human body.
*9. "CAUTION" for 2.5 mWcm2 or less, and “DANGER” for 2.5 mWcm2 or more.
*10.A delay is required between the display and actual emission.
*11.The method that is required differs for the demonstration of a Class IIIb or Class IV laser product and just the laser beam itself.
*12."DANGER" logotype.
*13.Required after August 20, 1986.

Precautions to Laser-equipment Users

ANSI Z136.1: 1993

* The following information was edited by OMRON based on the actual standard. OMRON assumes no responsibility for this information. You should always check the original text of the standard before implementing an actual application.

Note:
1. Level of requirement Mandatory: Shall. Preferable: Should
2. Laser Safety Officer (LSO)
The LSO is given the responsibility and authority to monitor and execute laser hazard controls, use knowledge to evaluate sources for laser hazards, and make countermeasures effective. Refer to Section 1.3 of ANSI standard Z136.1993.

Classification of Sensors Using Lasers

* For details, refer to your OMRON website.

Precautions for Safe Use of Laser Beams

(1) Ensure that the laser beam does not enter the eye either directly or by reflection off a mirror surface.

(2) Labels of the type shown below are attached to Sensors that use lasers. (These are typical examples.) Observe the instructions given on the labels when handling the Sensors.

Class 1 Labels	Class 2 Labels	Class 3B Labels

(3) Adjust the optical axis with an IR scope or a fluorescent plate that converts infrared rays into visible light.

Attach the following labels, supplied with the product, if the equipment is being exported to Europe or the USA. Labels for the USFDA are only supplied with products that have been applied for and registered by the FDA.

Europe (EN Standard)

USA (FDA)