(Last Updated On: February 16, 2020)

how do laser rangefinder work

If you are an astronomy lover and you enjoy taking pictures, then I bet you are familiar with rangefinders. For you to continue enjoying viewing fantastic objects, you must consider getting the rangefinders. Don’t panic if you are not an expert in rangefinder technology, because they are easy to use. Before describing how do rangefinders work? and the reasons why every golfer should use them, let us first define a rangefinder.

Generally, a rangefinder can be described as an instrument that aids in measuring the distance from the user to the target. Each pair of rangefinders has a small compact camera that is used to focus the target’s shot.

A rangefinder does not require a mirror or prism to take a chance. Rangefinders are not used by golfers only but also used by hunters, photographers, surveyors, and many more.

Laser, Optical, and GPS Rangefinder

Rangefinders come in different forms. Laser rangefinders, optical rangefinders, and GPS are among the popular available options. Optical rangefinders accurately measure the distance between the user and the target.

They purposely work by using the pre-loaded scale to convert the size of the object to the range. Hunters and golfers commonly prefer optical rangefinders because they are cheaper and efficient.

On the other hand, laser rangefinders work by accurately locating the target, and then display the number of meters to where the aim is. GPS rangefinders work by using the GPS location that has been pre-loaded to give accurate information on the distance in front, back, and middle.

It also provides flyover maps that allow you to know where you are going.

how do rangefinder work?


Different Uses of Rangefinders

It is essential to know how one can use rangefinders. In today’s world, people are using rangefinders to make their job easier. If you possess a rangefinder, you can practically use them to do the following

  • Golfing People who like golf find the tool very necessary since it accurately measures the target distance. It is essential to know some manufacturers design the rangefinders to do golfing purposely.
  • Hunting When hunting, it can be very challenging, especially if there are many obstacles involved. It is, therefore, vital to range the hunting ground. Getting top-notch rangefinders will improve on the accuracy, especially when a fast-moving target is involved.
  • Photography If you enjoy doing photography, rangefinders will sort you big. They help you accurately measure the distance between one object and the other, thus getting accurate information. It might be a bit tricky for novice users to understand the dynamics, but after practicing more often, the pair will give you rewarding results.

The history of rangefinders

The first laser rangefinder was developed in the twentieth century. The Romans come up with an idea of constructing a device that would measure the distance during a battle. After the Roman Empire, a new tool called Jacob’s staff was invented.

It was commonly used to measure angles and distances. Jacob’s staff was usually used in ancient war was used to launch large rocks. Since then, companies have made rangefinder cameras in all sizes and shapes.

However, the optical rangefinder has been in existence since the eighteenth century. They used old cameras for surveillance. The optical rangefinder was equipped with lenses and prisms on both ends. The eyepiece was placed at the center.

The parallax was strategically poisoned at the center so that it can effectively locate the target and estimate the distance between the target and the user. The user had to calculate the number of angles made by both ends.

The technology has advanced since today’s rangefinder can be used in hunting, golfing, and even for photography. Some rangefinders still rely on optics just like the ancient rangefinders.

The recent ones work accurately, also if the target is far away by measuring the energy impulses released. For example, laser rangefinder can work by merely measuring the delay taken to receive the signal reflected.

Today’s rangefinder can measure the speed of a moving target using the Doppler Effect.

how do rangefinders work?

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How Do Rangefinders work?

After giving you an overview, the next thing to do is understand how rangefinders work. Here is an insight into how different types of rangefinders work.

1. Laser Rangefinder

The basic concept of the most laser rangefinder is the same. Once you switch on the rangefinder, it emits laser beams. The beams emitted bounces off to the target object. The clock inside the rangefinder then measures the time taken by the rays to go and return.

The beams travel at the speed of the light, and the time measured is later displayed for the user to view it. Rangefinder in this category narrows the beam divergence, thus allowing it to spread and diverge out over long distances.

In other words, when the beams reach where the target is, the laser beams are spread widely, thus covering the goal and reflects other things. Laser rangefinders also reflect and deflect objects that are harder to measure.

 For your information, rangefinders can’t work correctly in all target objects. Some reflective objects like a mirror deflect the light away instead of bouncing it back to the receiver. The deflection makes it hard to range the object.

You may wonder why the rangefinder is not confused by the ambient light well; the answer is pretty simple. Always, the laser light emitted has a specific wavelength that is different from ordinary light. With that frequency, it becomes simple to filter all unnecessary light apart from the laser light being reflected in the target.

The finder, therefore, will only find the laser light.  Laser beams are fundamental since it helps in filtering the reflected outgoing light that is being reflected by the target. It is beneficial since it can capture a fraction of the original light that a human eye can’t achieve.

To choose a reading, laser rangefinders have a unique way of working exceptionally quickly by sending thousands of pulses to the target and use the sample range to determine the actual distance to report.

The report has all the readings that include the destination itself, the terrain in front and sides. It quickly takes all the readings and later considers the most sensible object and analyzes using a set algorithm to pick the most sensible distance.

Range finders have much variance in their performance, and here are some of the things to consider when looking for laser rangefinders

how do rangefinders work

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2. Optical Rangefinders

Optical rangefinders have been there since the eighteenth century. They were widely used, especially during World War II. These rangefinders do not require optics and reflective targets. The best thing about the pair is that they don’t get confused by the weather.

You should note that optical rangefinders are not as famous as they were in the past. You will spend a lot of time looking for a pair because laser rangefinders are cheaper and readily available.

They have a pre-loaded conversion chart, which is responsible for providing a graph that is used for distance reading. The eyepiece present measures the pin height. The two lenses current on the opposite sides focus on the objects while the focusing knob creates an overlay of the images.

The knob is responsible for marking the scale, which later converts the readings provided into the distance. Optical rangefinders use coincidence and stereoscopic principles to work. Images are reflected from two sources that are shown to the user, who view the images using one eye.

The user adjusts the knob until they match the right alignment. Aligning the images and the number of adjustments is the one that determines the distance to the target. The stereoscopic principle works by using both eyes of the user to find the range of the image.

The reflected images are aligned and marked inside the reticle to calculate the distance. Some rangefinder uses cheaper and simpler reticles called MilDot. You should be very careful when handling optical rangefinders since the way you adjust the knob will determine the accuracy.

Factors to consider when choosing a Rangefinder.

Ability to spot the target- When choosing laser rangefinders, you must look for those with a good magnification power and quality optics. It becomes challenging to range the target if the magnification power is reduced.

Rangefinder, with a magnification of 10X, offers the best range of the destinations. That means that you can fail to spot a target using rangefinder with a magnification of 5X but later find a goal using a rangefinder with a magnification of 8X or 10X. Getting one with a good glass can save you a great time.


Ability to analyze the results correctly– Rangefinders interpret the same readings differently. It is essential to consider the rangefinders that explain and gives you the best readings. For example, older models miss some crucial features because they will only display only the first reading that was reflected in the unit.

On the other hand, modern rangefinders have a unique multi-pulse technology that first emits thousands of laser pulses thus analyzing the target and ignore unnecessarily outliers thus giving out more accurate information that has a significant impact on how the user will interpret the findings


Ability to show how focused the beam is– When selecting a rangefinder, you should choose one that can get energy released on the target. Rangefinder with a smaller and tight beam divergence gives a clearer impulse compared to those with more extensive beam divergence.

You should also consider the quality of the laser impulses that are being transmitted. A good rangefinder should have an accurate wavelength and sharpness for you to get clear images.


The aperture size– The size of the opening should accurately capture the reading sent to the actual sensor. You should choose a rangefinder with a large aperture since it can capture, collect, and analyze the target that is far.


Other types of rangefinders

Apart from Laser and optic rangefinders that are common, other range-finding devices are used every day. First, there is Radio Detection and Ranging (RADAR) that is used to give impulses for the radio signals.

RADAR works like laser rangefinders, but it does not focus on laser light but focuses on the radio waves. Since radio waves move at a speed of light, RADAR calculates the distance taken for the wave to return to the target.

LIDAR rangefinder, on the other hand, uses the principle used by the laser rangefinders but works on a larger scale. Light pulses are spread over a wide range. Although it is expensive, LIDAR can detect smaller objects than RADAR.

However, LIDAR’s performance is affected by weather conditions such as rain, fog, and clouds. Ultrasonic range finding involves the use of high frequency for the sound waves that cannot be detected by human ears. When ultrasonic waves strike the target, the waves strike back at high speed, and one can calculate the speed taken to bounce back from the goal.

SONAR range-finding, on the other hand, uses sound pulses to measure the distance and time taken to travel to and from the target. This type of range-finding is often used in places where laser light can’t reach like underwater.

What Influences Measurement Range?

Several factors affect how a rangefinder performs. For example, the targeted object, rangefinder support, the atmospheric conditions can affect performance — also, the size of the target, vibration, and lighting conditions.

You should also note that even if the manufacturers advertise that a certain rangefinder can range 10X, but some unavoidable circumstances can change the accuracy.

That means the advertised maximum range can only work if the condition is ideal, like the weather is clear, the target is not very reflective, and there are no oblique surfaces. 

Some rangefinders have a red display while others have a black display. Rangefinders with the red display are preferred because of their ability to easily pops-out, making it easier to view the target, especially when the background is dark like when in a forest.

The black rangefinder, on the other hand, uses black color to display, thus making it quite challenging to view in the low light.

You should note that rangefinders work better on some objects than others. It is challenging to measure reflective things like water and glass.









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