Inspection Training

Class Information
Inspection Training Tooling U-SME classes are offered at the beginner, intermediate, and advanced levels. The typical class consists of 12 to 25 lessons and will take approximately one hour to complete.
Class Name:Inspecting with Optical Comparators 230
Description:This class compares different types of optical comparators and explains how they work best under different conditions.
Prerequisites: 350115  350130 
Number of Lessons:19
Language:English, Spanish
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Class Outline
  • Objectives
  • Measuring with Optical Comparators
  • Using Different Optical Systems
  • Optical System Quality
  • Illuminating the Part
  • Types of Optical Comparators
  • Manually Operated Optical Comparators
  • Digitally Controlled Optical Comparators
  • Software-Driven Optical Comparators
  • Optical Comparator Charts
  • Physical and Digital Scales
  • Edge Detection
  • Locating Points in Space
  • Measurement by Comparison
  • Measurement by Screen Rotation
  • Measurement by Motion
  • Reducing Variation With Optical Comparators
  • Optical Comparator Maintenance
  • Summary
Class Objectives
  • Describe the benefits of understanding how optical comparators work.
  • Match an optical system with its resulting display type.
  • Describe factors that affect optical system quality.
  • Describe common methods for improving part illumination.
  • Describe the relationship between optical comparator complexity and operator involvement.
  • Describe characteristics of manually operated optical comparators.
  • Describe characteristics of digitally operated optical comparators.
  • Describe characteristics of software-driven optical comparators.
  • Distinguish among different types of screen charts.
  • Distinguish between physical and digital scales.
  • Match common methods of edge detection with their characteristics.
  • List in order the sequence of steps for finding the center of a hole.
  • Describe methods of measurement by comparison.
  • Describe methods of measurement by screen rotation.
  • Describe methods of measurement by motion.
  • Describe ways to reduce variation when measuring with optical comparators.
  • Describe the proper maintenance of an optical comparator.

Class Vocabulary

Vocabulary TermDefinition
automatic edge detection A method of edge detection that uses an electronic or fiber-optic device to locate differences between light and dark.
computer numeric control CNC. The use of computers and special programs to automatically carry out various machine operations.
computer-aided design CAD. The use of computer software to aid in the design of a part and the generation of the part program.
corrected optics An optical system that projects a partially corrected image of the feature on the screen. The image appears right side up but backwards.
crosshairs A pair of fine lines on the screen of an optical comparator that represent the X- and Y-axes.
digital micrometer A U-shaped measuring device that displays measurements of length on a small screen.
digital readout A display system for showing numbers or values. On a digitally controlled optical comparator, digital readout refers to the panel that includes the display and the controls.
digital scale An electronic measuring device that uses fiber optics to detect and transmit its position to a digital or computer readout for display.
edge detection One of the primary means of measurement employed by optical comparators. A variety of edge detection methods may be used to find the difference between light and dark, and thus the edge of a part.
electronic scale A series of fine lines that, when read by a sensor, tells the optical comparator the axis coordinates.
fiber-optic scale Part of an electronic measuring device made of glass strands that uses light to read and transmit the position of features.
fixture A dedicated workholding device used to locate and hold a part during machining or inspection.
fully corrected optics An optical system that projects a fully corrected image of the feature on the screen. The image has exactly the same orientation as the part.
glass chart A circular piece of glass that contains fine measurement markings for use on an optical comparator.
go-no go gaging The use of a gage to determine whether a part feature simply passes or fails inspection. No effort is made to determine the exact degree of error.
indexing A method of part locating that translates circular motion into linear movement. One whole rotation of a large dial on a machine table might translate into one millimeter of movement for the table.
joystick control A vertical handle or lever that allows remote, but hands-on, operation of a machine.
measurement by motion A measurement method in which the part is indexed, or moved linearly. Measurement by motion is usually used when the whole part or feature is too large to fit on the screen at the same time.
operator error A mistake that may be traced to the technique or practices of the person doing the measuring. The purpose of automated measurement is to reduce or eliminate operator error.
optical comparator An instrument that projects a magnified image of a part feature onto a screen for inspection. It is also known as an optical projector.
optical system The combination of mirrors and lenses in an optical comparator that make image projection possible. The optical system is also referred to as the optics.
optics A common name for the system of lenses and mirrors in an optical comparator.
paper chart A circular piece of paper that contains fine measurement markings for use on an optical comparator.
physical scale A tangible, visible scale that is present on the edge of the screen and often on the chart overlays.
plane of sharpness The area on the screen of an optical comparator where the projected image has the most detail. The plane of sharpness is usually in the center of the screen.
resolution The fineness of detail in an image that has been reproduced.
rotary encoder A device that translates rotary motion into a series of electronic pulses. The total pulse count indicates the measurement.
screen protractor Another name for the screen ring when it has a scale marked in its perimeter.
screen ring The circular opening on an optical comparator that surrounds the glass screen.
screen rotation The rotation or turning of the optical comparator screen used to line up chart markings with part features.
shop scale A common screen chart that contains frequently used arc and radius markings.
simple optics An optical system that projects an uncorrected image of the feature on the screen. The image appears upside down and backwards.
static scale An immovable measuring scale, similar to a ruler, that is attached to the edge of an optical comparator screen.
translation Linear part movement on an optical comparator.
turret A rotating device on the optical comparator that holds multiple lenses.
vellum A type of high-quality, heavy paper that is comparable to parchment.
vernier scale A type of scale consisting of two opposing line markings with different divisions. A screen ring with a scale opposite a static scale on the machine creates a vernier scale.
vinyl chart A circular piece of vinyl or plastic that contains fine measurement markings for use on an optical comparator.
X-axis When facing the vertical screen of an optical comparator, the linear axis representing motions and positions along a line parallel to the horizon and to the left and right of the observer.
Y-axis When facing the vertical screen of an optical comparator, the linear axis representing motions and positions above and below the horizon line.