Profile Projector

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Also known as an optical comparator, a profile projector is an optical instrument that can be used for measuring. It is a useful item in a small parts machine shop or production line for the quality control inspection team.

Profile projector, also known as contour comparator, is widely used to measure 2-dimensional data.


Profile projector is widely used for complex shape stampings, gears, cams, threads and comparing the measured contour model. It's easy to use and highly efficient.
It is a commonly used measurement of optical instruments. Thus, profile projector is widely used in major machinery manufacturing including aviation, aerospace industry, watches and clocks, electronics, instrumentation industry, research institutes and detection metering stations at all levels and etc.

Work Principle[edit]

Profile projector working structure

The projector magnifies the profile of the specimen, and displays this on the built-in projection screen. On this screen there is typically a grid that can be rotated 360 degrees so the X-Y axis of the screen can be aligned with a straight edge of the machined part to examine or measure. This projection screen displays the profile of the specimen and is magnified for better ease of calculating linear measurements.
An edge of the specimen to examine may be lined up with the grid on the screen. From there, simple measurements may be taken for distances to other points. This is being done on a magnified profile of the specimen. It can be simpler as well as reduce errors by measuring on the magnified projection screen of a profile projector.
The typical method for lighting is by diascopic illumination, which is lighting from behind. This type of lighting is also called transmitted illumination when the specimen is translucent and light can pass through it. If the specimen is opaque, then the light will not go through it, but will form a profile of the specimen.
Measuring of the sample can be done on the projection screen. A profile projector may also have episcopic illumination (which is light shining from above). This useful in displaying bores or internal areas that may need to be measured.


  • Multi-point collection to determine the line and circle;
  • Preset the geometry elements;
  • Determine the combination of various geometric elements;
  • Coordinate rotation and translation;
  • Z-axis can be set as length of the sensor or angle value of the encoder;
  • User self-programming function;
  • Polar / rectangular coordinates conversion;
  • Grating linear correction, section linear correction;
  • RS232 input function;
  • Print page input function;
  • Power-off memory function;
  • The geometric elements can be stored and call on.

How To Select[edit]

Choose the projection method[edit]

a) Vertical projectors: The main axe is parallel to the plane of the screen. They're most common, and suitable for flat parts or smaller work-pieces. b) Horizontal Projector: The main axis is perpendicular to the plane of the projection screen. They are mainly medium and large, and suitable for shaft parts or heavy work-pieces with large volume.

Select the positive or inverted image[edit]

For the simplest profile projector, the product's inverted image, also known as mirror image, will be displayed on the screen.
In order to facilitate the measurement, sometimes we will deliberately add a plus-image system, changing the inverted image into a positive one, but it will undoubtedly increase the cost and reduced the measurement accuracy.

Select screen size[edit]

As for selection of screen size, you should carefully consider whether the entire part must be appeared on the screen. If it can achieve the purpose via segment observation, it's no need for large screen. Every projector manufacturer has a wide range of screen sizes to choose.

Choose magnification[edit]

The magnification of lens is fixed. Different part of measured piece often request different magnification. But the projector factory standard configuration is usually with only one lens, you must purchase according the real needs.

Select the appropriate work table and accessories.[edit]

Work table is used to place and hold the measured piece. Its own volume, X, Y travel and carrying capacity are critical. Meanwhile, for the convenience of holding workpiece, it will be need to buy a rotary table, V-holder and other accessories.
Besides, the projector must also have a flexible and stable focusing mechanism and large working distance (the top surface of the workpiece and the lens pitch). Select appropriate data processing mode: all optical measuring projectors on market, without exception, have been digitized. We must focus on its data processing capabilities.

Select the appropriate precision.[edit]

Current commercially available optical measuring projectors' theory accuracy, because the optical lens and gratings are on similar quality, are also similar. Therefore, it's no need to deliberately pursue the high precision.



  1. ^ Leung, Sonny. "What Is Profile Projector". Vision Measuring Machine and Profile Projector. Retrieved 8 December 2016.