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3D scanner buying guide: what’s in a datasheet?


This 3D scanner buying guide explains how to compare 3D scanners by technical specifications. These tech specs include accuracy, resolution, scan speed, field of view, mobility and colors (textures).

By Thomas Tong, President of Polyga, Inc.

What’s in a 3D scanner datasheet?

When looking to buy a 3D scanner, product brochures list technical specifications to give you general impressions about the performance of the systems. You can also use them to compare 3D scanners to determine which system is right for you.

However, at times it can leave you wondering:

  • What do these terms really mean?
  • How relevant are they when it comes to finally using the device for 3D scanning?
  • Which technical specifications are the most important for your particular application and how would they affect your buying decision?

In this guide, we’ll answer all these questions by looking into these terms. We’ll use real-life examples taken from datasheets for comparison.




Resolution

How fine of a detail the 3D scanner can capture in one scan.

A 3D scanner initial output is to capture measurement points in 3D space. A cluster of these points creates a point cloud, which represent the surface geometry of a physical object.
3D scanner mesh point cloud
Original object used to 3D scan and generate a mesh point cloud

Point cloud of a rabbit scan (left) of the infamous Stanford Bunny (right). It has been used in various research projects in computer graphics. Source: Stanford 3D Scanning Repository

Point-to-point distance

There are a number of different ways to measure resolution, but the easiest way to think about resolution is to look at the point-to-point distance (usually expressed in points per mm or inches). It’s the distance between two points in a 3D model.

DATASHEET EXAMPLE
Lower resolution Higher resolution
0.1mm point-to-point distance 0.03mm point-to-point distance
The smaller the number, the higher the resolution. Lower resolution means points are more spaced out.

Higher resolution means points are denser, therefore providing more details. For scanning small objects, you want a smaller point-to-point distance to ensure details are captured. For large objects, a lower point to point distance is usually acceptable.

Points per scan

Another way to think about resolution is it indicates how many points the 3D scanner will give you across a certain fixed distance or a scan. For certain applications, you might need to capture fine details which would require a high resolution 3D scanner.

DATASHEET EXAMPLE
Lower resolution Higher resolution
985,000 points per scan 2 million points per scan
The higher the number, the higher the resolution. More points give you more detail.

Low resolution would be acceptable for 3D printing an object if you are using a low-cost, consumer grade 3D printer that doesn’t print in high resolution quality. However, you might need high resolution if you are inspecting a part and need the high level of detail to determine if the manufactured part meets quality assurance standards.

3D scanner buying guide: sneaker sole 3D scan

High resolution scan of a sneaker sole using the HDI Advance 3D scanner.

3D scanner buying guide: sneaker sole 3D scan

The mesh density demonstrates how much detail is captured from the scan data.

Accuracy

How close a 3D measurement is to the true or accepted value.

Visually, the data from an entry level 3D scanner might look similar to a professional one; but if the results aren’t accurate, then it’s not particularly useful for some applications like quality inspection where accuracy matters the most.

 

There are many different ways to measure accuracy and at various stages of the 3D scanning processing. However, the simplest way is to look at the accuracy of any two points (distance) and how it compares to the true or accepted value.

DATASHEET EXAMPLE
Lower accuracy Higher accuracy
Up to 0.040mm (0.0016 inch) Up to 0.030mm (0.0012 inch)
The smaller the number, the higher the accuracy. Normally expressed in mm, inches, or microns.

 

Professional grade 3D scanners use gauge blocks or other objects with certified known measurement(s) to determine the accuracy number of a 3D scanner.

Professional grade 3D scanners use gauge blocks or other objects with certified known measurement(s) to determine the accuracy number of a 3D scanner.

The accuracy of the scanner generally determines how many applications the device is able to solve. The higher the accuracy of the scan data, the more applications you can use it for. It’s also what separates the difference between a consumer/hobbyist 3D scanner and a high-end professional 3D scanner. The former is substantially less expensive than a professional one.

Accuracy vs. volumetric accuracy

When the term accuracy is used, it usually refers to the accuracy of a single scan. Volumetric accuracy, on the other hand, usually means what the accuracy is when the scans are aligned and merged into a complete digital 3D model. This number can be mysterious as it’s difficult to tell how many scans were used when the manufacturer determined this number. Therefore, it is easier to compare 3D scanners using the accuracy of a single scan rather than volumetric accuracy.

Scan speed (measurement rate)

Rate at which the 3D scanner captures a single scan.

Scan speed only accounts for how long it takes the scanner to take a scan. It usually does not include processing time. It is sometimes difficult to compare scan speed across 3D scanners when manufacturers use different ways to express this term. However, most of the time scan speed is not particularly crucial.

 

DATASHEET EXAMPLE
EXPRESSED IN MEASUREMENT POINTS PER SECOND
Slower scan speed Faster scan speed
205,000 measurements/second 480,000 measurements/second
A higher number means faster scan speed.
DATASHEET EXAMPLE
EXPRESSED IN SPEED AT WHICH THE SCANNER TAKES A SINGLE SCAN
Slower scan speed Faster scan speed
1.5 seconds/scan 1 second/scan
A lower number means faster scan speed.
DATASHEET EXAMPLE
EXPRESSED IN FRAMES PER SECOND
Slower scan speed Faster scan speed
7.5 frames/second 16 frames/second
A handheld 3D scanner’s scan speed can be expressed in frames per second because it captures scans like a video recorder. A higher frame rate indicates faster scan speed.

Back in the days, completing a single 3D scan and processing the data could take an hour or more. Fast forward to now, almost all 3D scanners can acquire and process a 3D scan in 10 to 20 seconds, and creating a combined, full digital 3D model can be done within a few minutes. The only time where you need very high scan speed is:

  • If you need to scan objects that are moving (for example, parts moving at production speed on a conveyor belt in a factory, face scanning, or body scanning)
  • Using a handheld 3D scanner, which allows you to complete your scans faster

 




Field of View (scanning area or scan range)

The area or volume that the 3D scanner can “see” in order to capture a 3D scan.

Usually the field of view of a 3D scanner is fixed, but many structured-light systems can be adjusted to have multiple fields of view. This is done with simple hardware reconfiguration and by re-calibrating the system for accuracy.

Unless you really need flexible field of views, it’s much easier to buy a scanner that specifically targets the size and types of objects that you’re interested in scanning. You can get plug-and-play devices that are already factory calibrated so you can get started 3D scanning right away.

Field of view 3D scanner buying guide

Three 3D scanners with varying field of views (from smallest to biggest).
The size of the object is the same.

Get the right field of view for your application

If you’re primarily going to be 3D scanning small objects, don’t get a scanner that’s built for scanning large objects, and vice versa. This is because getting ill-fitted field of view for the objects you were scanning will affect the scan data quality that comes out of the 3D scanner.

Mobility

The portability of a 3D scanner.

One of the biggest debates revolving around the selection of 3D scanners is handheld versus stationary.

Almost in all cases, a stationary scanner will be more accurate than a handheld or mobile 3D scanner since the latter takes moving frames instead of still photos to compose a 3D scan. If accuracy is important, a stationary 3D scanner is one that returns clean raw scan data. It is often easier and quicker to use.

A handheld scanner is great for quickly scanning objects at slightly lower accuracy. However, its strength lies in the ability to get to areas that might be difficult for a stationary scanner to get into.

THE DIFFERENCE
Stationary 3D scanner Handheld 3D scanner
A stationary system scans like a camera on a tripod. The scanner is stationary while capturing a scan. A handheld scans like a video recorder. The capturing process is like painting with a brush.
Strength: higher accuracy Strength: convenience

 

There are always trade-offs— strengths and drawbacks— to each system. Select the one you need for your application.

Product weight and dimension considerations

The weight and size of the 3D scanner is often completely ignored, but you’ll sure notice when you’re lugging a giant travel case through the airport. Most 3D scanners tend to be large and bulky, with convenience being at the bottom of the feature checklist. Be sure to pay special attention to this metric so you can get a storage case in the right size for your valuable device. The scanners are generally larger than you expect, so plan for storage space for them.

Color (textures)

Whether scans produced by a 3D scanner represents the exact likeness of the physical object.

Color is actually not a binary option. It consists of four options:

  • Geometry (no color, just mesh or points)
  • Black and white (monochrome)
  • Low quality color
  • High resolution color

Usually you only need color scans for 3D visualization applications (such as product display for online retail applications) or medical applications (such as skin analysis for plastic surgery). Generally, colors sensors are less accurate than 3D scanners that generate pure black and white scans.

Color option will cost you

If you don’t need color, then there’s no need to pay for it because it is usually an added cost.

Also, many 3D scanners return color as color per vertex (every point has a color value for handheld 3D scanners) whereas other scanners return a full color map (every point is a reference position to a full-color image for stationary 3D scanners).
Rhino 3D model

High resolution 3D digital model from HDI Advance 3D scanner courtesy of 4DGate.
View the color 3D model on Sketchfab.

Rhino 3D model texture

Color texture map for the 3D model.

In general, getting a color map gives you much higher accuracy and a better range of colors with more options for additional processing. A color map can always be simplified to color-per-vertex, but not the other way around.

The importance of technical specifications by applications

In reality, there’s no single metric that will best guide you when choosing a 3D scanner.

 

At the end of the day it depends on:

  • your application
  • what you need the 3D scanner for
  • your budget

These are the best drivers to help you decide which 3D scanner to pick.

In summary, here is a table to show which factors are most important for each use case:

TECHNICAL SPECIFICATIONS IMPORTANCE BY APPLICATION
APPLICATIONS
SPECS Visual effects 3D printing Reverse engineering 3D inspection
Resolution 2 3 3 1
Accuracy 5 4 2 1
Scan speed 1 3 4 4
Field of view 3 3 2 1
Mobility 2 2 2 3
Weight/dimensions 3 1 2 4
Color 1 2 5 4

Scale from 1 (high importance) to 5 (low importance).

 

For more information, please visit polyga.com.

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About this author

Thomas Tong

Thomas Tong is the President of Polyga Inc., a manufacturer of 3D scanning technologies and related software. Products with fewer features, executed exceptionally well, create the best experience. Polyga’s goal is to build simple, user-friendly tools that take 3D scan data to its full potential for a multitude of industry applications: 3D modeling, reverse engineering, and 3D inspection. For more information, please visit polyga.com.