Dial indicators, optical comparators, micrometers, calipers, etc are a few dimensions measuring instruments in the manufacturing and construction industry. These tools ensure that all the manufactured products meet with required dimensions.
An optical comparator, often known as a profile projector, is a precise measuring device extensively used in industries’ dimensional inspection and quality control. In this article, you will learn about optical comparators’ various aspects, including working principles, advantages, and applications.
The history of this device goes back to 1922 when James Hartness invented it to measure the dimensional variations of laboratory workpieces. This apparatus projects a workpiece’s image onto an LCD monitor for amplification without making physical contact with it.
Optical Comparator Working Principle
The reflection of light and magnification is the basic working principle of an optical comparator. A light source like a diffuser is used to illuminate the workpiece to create a uniform sheet of light. Due to the strike of light with the workpiece, it creates a magnified image projection on the LCD screen with the help of lenses and mirrors.
- Light Source Creation: To generate a uniform sheet of light, start with a high-intensity lamp or diffuser. Place this light source beneath the stage and direct it through a diffuser. This process scatters the rays, producing a homogeneous sheet of illumination.
- Workpiece Placement: The workpiece that needs to be inspected, is placed on the stage in such a way that it can make precise movement in both horizontal and vertical directions.
- Image Formation: This is the most important step where the actual work of the optical comparator starts. Workpiece which is placed on the stage, effectively propels an image due to the light beaming from beneath. By illuminating any characteristics that obstruct light, this shadow depicts the part’s profile.
- Magnification and Projection: The formed image is now captured and magnified through various lenses and mirrors. The magnified image is then directed to the LCD screen where further measurements are done.
- Dimension Measurements: The image on the LCD screen has various markings and etched lines that tell the corresponding dimensions of the workpiece. There is no physical touch involved as the measured readings and data are displayed on the advanced monitoring devices.
Important Components of Optical Comparator
- Base – The entire setup
- Table – To stage the workpiece
- Plunger – A sensing perimeter
- Pivoted lever – Connect plunger and mirrors
- Mirror – Reflects the light rays
- Condenser lens – Convert divergent light rays to parallel
- Projection lens – Condensed parallel light rays
- Light source – Like a lamp
- Scale and Screen – To analyze the workpiece
Optical Comparator Advantages and Disadvantages
Advantages
Contactless Measurement
Right from placing a workpiece to making the final measurement, an optical comparator is completely contactless. Contactless devices have fewer errors because they do not involve physical touch.
A Few Moving Parts
Except for the stage for workpiece placement, this dimensions measuring instrument has no moving part. Lesser moving parts mean fewer errors and higher accuracy throughout the measuring process.
2-dimensional Measurement
Optical comparators may evaluate in two dimensions, in contrast to other instruments like micrometers, which are capable of measuring a single dimension at a time. It saves time and enhances accuracy by measuring different dimensions in a single setup.
Ergonomically Designed
The operator must hold a uniform posture and make tool adjustments while assessing the dimensions of the workpiece in a traditional comparator. On the other hand, an optical comparator allows the user to take readings while standing or sitting comfortably in any position.
More Safe Measurement
One more great benefit of optical comparators is that there is less chance of damaging more sensitive parts because only light contacts the component being measured.
Disadvantages
- Required a separate power source
- An advanced model of optical comparator is expensive
- Though the measurement is easy and accurate, it can only work in the darkroom
- Continuous release of heat rays might cause drifts of other components
Conclusion
Optical comparators are dimensions measuring instruments that precisely measure the dimensions of various products and workpieces. No moving part, contactless measurement, multi-dimensional working, and ergonomically designed are the few advantages of an optical comparator that make it a vital tool for industries.
