Retroreflective Photo Eyes vs. Thru Beam Photo Eyes

Compare Pros and Cons to Find the Right Detection Solution

retroreflective photo eye vs thru beam photo eye

Along with other types of access control systems, photo eyes are a specialized type of equipment for monitoring gates, doors, and other barriers. These systems help to protect people, vehicles, and facilities as vehicles and other objects move through or become entrapped (stopped) in their beams. A variety of different types of photo eyes are available depending on the application and environment, but in this post, we’ll be exploring two of the most common types. These include the retroreflective photo eye and the thru beam photo eye.

While both types of photo eyes utilize an infrared beam to monitor potentially hazardous areas of gate and door installations, there are key configurational and functional differences that should be considered when deciding which one to install in your facilities or spaces.

  • A thru beam photo eye consists of a two-piece unit with a separate transmitter and receiver. These are mounted opposite each other with the transmitter emitting an infrared beam that is detected by the receiver.
  • A retroreflective photo eye combines the transmitter and receiver in one unit. However, a separate reflector (typically a white plastic reflector around 3” in diameter) is also installed with the unit to bounce the infrared beam back to the receiver.

Retroreflective Photo Eyes


One immediate advantage of a retroreflective photo eye is that it requires running fewer cables. Because this style combines the receiver and transmitter in a single unit, installers don’t have to deal with the time and hassle of running cabling to two separate components. This saves time on the installation and keeps the associated cost lower since less material (wiring) is needed. Related, a retroreflective eye is also ideal for facilities and spaces with thinner or smaller roadways and entrances. Between these two photo eye types, a retroreflective photo eye is generally the less expensive choice. And last but not least, due to the optics used, retroreflective photo eyes are less susceptible to interference from the sun.


Because a retroreflective photo eye has roughly half the operating range as a thru beam photo eye, this style might not work for your facility or space. If you have a particularly wide entryway or roadway, its beam may not be able to accurately detect all obstructions.

Find your solution now: EMX Industries, Inc. offers a full range of retroreflective photo eyes for different applications. Explore all of our options and connect with us to find the right one for your space.

Thru Beam Photo Eyes


Thru beam photo eyes also have a few key installation benefits. The transmitter and receiver, while separate, are easier to align because the angle of the infrared transmitter is much wider. While installers do have to implement two separate devices, reliability will be better due to the stronger beam. Thru beam photo eyes are also more useful for wider spaces. This particular photo eye is also highly recommended for more dynamic and harsh conditions and environments where snow, rain, and harsh sunlight are present.


Installation will take a bit more time since two units must be implemented. Additionally, wiring will be needed to power both units as well. The cost of a thru beam photo eye will also be higher, though the investment in greater performance and reliability proves this photo eye’s value in the long term.

Browse thru beam solutions: We offer a complete portfolio of thru beam photo eyes to ensure you have the ideal detection solution for your space. Explore our available photo eyes here.

See the Difference with Photo Eyes from EMX

EMX Industries, Inc. has been designing, manufacturing, and supporting industry-leading photo eyes for years. Our line of retroreflective photo eyes and thru beam photo eyes are used in countless applications including gate sensing, overhead door environments, and security. Every photo eye kit we offer comes complete with all of the accessories needed for installers to quickly and easily configure and integrate our photo eyes into your facilities and spaces, such as protective hoods, plastic reflector hoods, mounting brackets, receiver sunshields, and more.

Above all, we work with each client closely to understand the environments in which they’re looking to implement our photo eyes and sensors as well as the dynamics of those spaces to ensure our recommendations will deliver lasting performance. We also offer a variety of solutions for UL325-2018 compliance, including:

  • IRB-RET retroreflective photo eye
  • IRB-MON thru beam photo eye
  • IRB-315 infrared photo eye
  • NIR-50-325 retroreflective photo eye

Whether you already have a solution in place and are looking to upgrade, or are looking to implement a completely new photo eye kit for high performance from the start, our photo eyes ensure complete security and operational reliability in your spaces.

Get in touch today to learn more and to find the right one for your environment.

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