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How Does an Optical Rangefinder Work? Basics Explained

How does an optical rangefinder work
Written by Dan Goldsmith
Last Update: August 11, 2023

Optical rangefinders are devices used to measure the accurate distance between two points. They use light or laser beams to detect objects and calculate distances with high accuracy.

Rangefinders have many applications, from surveying and navigation to military operations and photography. Understanding how an optical rangefinder works can help you make better use of this powerful tool.

Using this technology, engineers and surveyors can quickly and easily measure distances for various purposes. But, how does an optical rangefinder work? Well, that’s what we’re going to explore today.

In this article, we will explain how optical rangefinders work and discuss their pros and cons over other measuring tools. Let’s get started!

What Is an Optical Rangefinder?

An optical rangefinder is a device that uses light or laser beams to measure distances. It works by sending out and detecting a beam of infrared, visible light, or a laser. The time it takes for the beam to reflect back from the object is used to calculate its distance.

When these devices are used in surveying and navigation, they are usually equipped with lenses and other optics components to help them focus on their targets accurately.

An optical rangefinder consists of two main parts: the emitter and the detector. The emitter sends out a beam of light or laser, while the detector receives it after reflecting off an object and measures its return time.

This device is most commonly used in engineering, surveying, and military applications.

Types of Optical Rangefinders

Now, let’s take a look at the different types of rangefinders. There are 3 main types of optical rangefinders.

1. Stereoscopic Rangefinders

Stereoscopic rangefinders use a camera pair to measure the distance of an object. The camera is often equipped with two lenses that are positioned at different angles and distances so they can accurately capture and compare images from both sides.

This type of rangefinder is commonly seen in military operations, where it is used to determine the distance between a target and a shooter.

2. Laser Rangefinders

Laser rangefinders are similar to stereoscopic rangefinders in that they use beams of light or laser to measure distances. However, instead of using two cameras, these devices use a single laser beam that is sent out and reflected back from an object to measure its distance.

The advantages of using a laser rangefinder are that it can provide more accurate results than a stereoscopic rangefinder, and it is faster since there’s no need to compare two images. Also, laser rangefinders work really well in long-range shooting and sports.

3. Coincidence Rangefinders

Coincidence rangefinders measure the distance between two objects by superimposing two images of the same object onto one screen. This allows them to calculate the difference in distance between the two objects.

You’ll find this type of rangefinder mostly used in surveying and navigation applications.

How Does an Optical Rangefinder Work?

Optical rangefinders work by emitting either an infrared, visible light beam or a laser. These beams can be sent as single pulses or at predetermined intervals until they hit an object and are reflected back to the optical rangefinder. The time it takes for the beam to be reflected back helps to calculate the distance between two points.

The optical rangefinder can also measure the angle of an object and its size, making it a valuable tool for surveying, navigation, and photography applications.

So, how does a laser rangefinder work?

Laser rangefinders work similarly to optical rangefinders, but they use a single laser beam that is sent out and reflected back from an object to measure its distance. This makes them faster and more accurate than optical rangefinders.

Now, what about golf rangefinders, you may ask. Golf rangefinders are optical rangefinders that have been specifically designed for golf courses. They provide accurate distance readings so that you can select the right club for your next shot.

Their speciality includes optical zoom capability, for accurate readings from farther away, and a flagstick mode, which allows you to zero in on the hole with precision.

Hunting rangefinders, on the other hand, are designed for big game hunting. They offer features like night vision capabilities, wind-speed reading and ballistic compensation to help you accurately measure your target from long distances.

Pros and Cons of Optical Rangefinders

Now that we’ve known enough about rangefinder functionalities, It’s time to explore what exactly they can and can’t do. Here, let’s explore the pros and cons of an optical rangefinder.


Optical rangefinders provide several advantages over other measuring tools. They are relatively inexpensive, easy to use, and can be used in a variety of applications such as surveying, navigation, engineering, photography, military operations and more.

Additionally, they offer high accuracy and short response time which makes them ideal for quickly determining distances. Optical rangefinders take less than a second to measure distances accurately.

What’s more, they don’t need any batteries to function properly (not the laser ones) so you can use them in almost any condition. However, the visibility will significantly impact the device’s accuracy.


One of the main disadvantages of optical rangefinders is that they are limited by the weather conditions.

For example, if there is too much light or fog present, hindering the line of sight, it can be difficult for the beam to get accurate readings on the distance of any object.

Additionally, these devices are sensitive to vibrations and other external factors which can affect its accuracy.

Who Can Use an Optical Rangefinder

Optical rangefinders are used by a variety of people for different applications.

Civil engineers, surveyors, geographers, military personnel and golf players are some of the most common users of these devices. Photographers can also use them to measure distances accurately from their camera lenses.

The wide range of applications makes them a useful tool for many professionals and hobbyists alike.

How Accurate Are Optical Rangefinders?

Optical rangefinders are known to offer accurate readings, with an average error rate of 0.3%. However, this varies depending on the type of optical rangefinder you are using and other external factors such as weather or light conditions.

They’re even more accurate than many GPS devices and are considered much more reliable.

An optical rangefinder is a useful tool for measuring distances accurately between two points in any environment. Laser rangefinders are more accurate and faster than their optical counterparts making them ideal for more precise applications such as golfing or surveying.

Despite their advantages, these devices have some limitations such as being affected by external factors like weather or light conditions.

Overall, rangefinders remain reliable tools and provide accurate measurements in most applications. This makes them a great choice for professionals and hobbyists alike who need to measure distances accurately and quickly.

And with this, we’re at the end of our today’s discussion. This blog provided a basic overview of the optical rangefinder working principle and choosing guide. I hope that answers your question, “how does an optical rangefinder work?”

If you have any thoughts and experiences, feel free to let us know in the comment section below. Thanks for reading this far, and I wish you a great weekend ahead!


How Long Does A Rangefinder Last?

Ans: The life span of an optical rangefinder can vary depending on the model and manufacturer. However, with regular maintenance and proper usage, a rangefinder can last for several years.

Do Rangefinders Need Calibration?

Ans: Yes! Rangefinders should be calibrated at least once a year to ensure accurate readings. This is especially important if the rangefinder is used in different environments or temperatures.

Are Rangefinders More Accurate Than GPS?

Ans: Yes, rangefinders are more accurate than GPS. This is because they measure distances directly from the device to an object, instead of relying on satellites in space.

About the author

Dan Goldsmith

Hi, this is Dan. We all know firearms are dangerous, but only when one doesn’t know how to use and care for them. I have 30+ years of experience with different types of guns and for the last 10 years, I have taught numerous people how to hold and shoot a gun while staying safe and keeping the surroundings unharmed.

My neighbors are some of my biggest admirers who enjoy talking to me about their guns, firearms safety and maintenance.

Whenever I am able to catch a moment of free time, you will find me enjoying my family or heading to the range on my motorcycle. I have enjoyed shooting sports ever since my dad introduced them to me as a child.

I like to think of myself as an outdoorsman who lives his life to the fullest. I hope you will benefit from my efforts to create valuable resources on this website. Happy reading!

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