What is an Optical Comparator?

Optical comparators (also called comparators or profile projectors) are measurement tools used in the manufacturing industry. Comparators inspect, measure, and compare the dimensions of manufactured parts. These measurement tools function using the principles of optics by utilizing illumination, lenses, and mirrors to project a magnified silhouette of a part upon a screen. Doing this compares the part to its prescribed limits.

Optical comparators are used to check for both dimensional accuracy and surface defects, such as scratches and indentations. In short, they allow for non-contact measurement and observation, minimizing handling while still allowing for close inspection.

Digital Optical Comparators

Where traditional optical comparators fall short, digital models pick up the slack. Manual comparator technology is highly useful in small-quantity applications, but with the rise of more complex parts and large-scale manufacturing, automation is necessary. Digital optical comparators present the solution.

Digital optical comparators offer the following advantages:

  • Automation capabilities: These models use software and cameras instead of human eyes to analyze and measure parts. The software automates the measuring process and completes it more quickly than a human can.
  • 3D capabilities: Digital optical comparators can use multiple lighting techniques and 3D inspection methods to analyze parts in all three dimensions.
  • Quantity management: The automated nature of digital optical comparators means they can analyze multiple parts automatically without human intervention.
  • Accuracy: By removing the potential for human error, digital optical comparators are extremely accurate in their measurements, which is necessary for many modern industries and technologies.

These advantages effectively maximize the accuracy of optical comparator measurements while reducing labor.

For SaleUsed$95,000

VisionGuage® VG700DOC-30V-XT1-20X Digital Optical Comparator

Base Machine Specifications

5-Axis Inspection and Measurement System (motorized X, Y, Z, A & B axes). 

  • X axis travel: 24″ 
  • Y axis travel: 24″ 
  • Z axis travel: 24″ 
  • A (tilt) axis range from -100 deg to +100 deg.
  • B (rotary) axis range from 0 deg to +360 deg. 

Axis configuration: the camera moves in X and Z (above the part) and the part is mounted on the dual rotary stages (i.e. rotary / tilt) that move in Y. 

All 5 Axes have closed-loop encoder feedback. 

  • X axis encoder resolution: 0.25μm 
  • Y axis encoder resolution: 0.25μm 
  • Z axis encoder resolution: 0.25μm 
  • A axis encoder resolution: 0.005 deg 
  • B axis encoder resolution: 0.005 deg 

20X single magnification optical system with extended working distance and extended depth-of-field. 

  • Working distance: 9.0″ (228 mm) 
  • Depth-of-field: 1.8″ (45 mm) 
  • Field of view: 1.7″ (43mm) x 1.2″ (30 mm) = 2.1″ (53 mm) diag. 
  • Optical system accuracy: better than +/- 0.00015″ (4 μm) 

Includes general-purpose dual-source reflected (i.e. front) LED illumination.

The system’s illumination: 

  • Is all LED-based (for stable and repeatable illumination conditions & results as well as long life) 
  • Is fully computer-controlled & programmable 
  • Provides very high brightness to easily handle even difficult-to-image areas 
  • The system’s dual-source illumination module provides lighting at different angles of incidence (i.e. both near-vertical and low-oblique) for wide applicability across a very broad range of part geometries. 

The entire system is run by the VisionGauge® software package: 

  • Powerful and easy-to-use 
  • Full 5-axis transforms 
  • Advanced software corrections with full 3D mapping across the system’s entire work envelope 
  • Includes a wide range of powerful inspection and measurement tools 
  • Robust & field-proven, with a broad installed base (over 3500 license in use worldwide) 

By default, the machine comes with a standard 3R pallet mounting system. Other mounting systems are also available upon request to allow you to use your existing workholding (thereby eliminating the need for re-fixturing and minimizing stack-up error, etc.) 


Model # VG700DOC-30V-XT1-20X 5-Axis Inspection and Measurement System, base machine with 24″ x 24″ x 24″ XYZ travel

Optional equipment (included)


  • Adapted NIST-Traceable Stage Micrometer with Certificate of Calibration 


  • Optional Standalone “Desktop” Software License
  • Allows you to remotely view your CAD files, setup tolerances, create automated inspection and measurement programs, etc. 


More information

Contact Blackbird at (716) 632-1000 for more information, or to make a purchase offer.