This set of Engineering Metrology Multiple Choice Questions & Answers (MCQs) focuses on “Principle of Working”.
1. What is the use of a laser beam in image formation?
a) Triangulation system for measuring system
b) Reduce glare of image
c) Controls contrast of image
d) Controls brightness of image
View Answer
Explanation: Laser beam is used for triangulation system for measuring distance. Polarised or ultraviolet light is used to reduce glare or increase contrast. It is important that light source is placed correctly since it influences the contrast of the image.
2. Where is backlighting is best suited?
a) Simple silhouette image is required to obtain minimum image contrast
b) Certain key features on the surface of the object are to be inspected
c) Simple silhouette image is required to obtain maximum image contrast
d) Three-dimensional feature is being inspected
View Answer
Explanation: Backlighting is suited when a simple silhouette image is required to obtain maximum image contrast. When certain key features on the surface of the object are to be inspected, front lighting is used.
3. Which light is preferred if three dimensional features are being inspected?
a) Front lighting
b) Side lighting
c) Backlighting
d) Any lighting is suited
View Answer
Explanation: Side lighting or structured lighting may be required when a three-dimensional feature is being inspected. The proper orientation and fixturing of part also deserve full attention. Selection of proper illumination technique is important for any feature.
4. Why do CCD or CID cameras are used?
a) To generate the electronic signal representing the image
b) To generate image’s hard copy
c) To determine lighting of the image
d) To capture heat signature
View Answer
Explanation: CCD or CID cameras are used to generate the electronic signal that represents the image. The camera collects light from the image scene via lens and uses a photosensitive target to converts it into electronic signal.
5. Where is the Vidicon Camera used?
a) Open-circuit television systems
b) In Image processing
c) In image analysis
d) Closed-circuit television systems
View Answer
Explanation: Vidicon Camera used in closed-circuit television systems can be used for machine vision systems. An image is formed in camera by focussing the incoming light through a series of lenses onto the photoconductive faceplate of the vidicon tube.
6. What is used in solid state cameras?
a) Image sensor IC
b) CMOS image sensors
c) Charge coupled device (CCD) image sensors
d) Digital camera image sensor
View Answer
Explanation: Solid state cameras are generally used in machine vision systems. These uses charge injected device (CID) or charge coupled device (CCD) image sensors. They contain linear or matrix array of small, accurately spaced photo-sensitive elements fabricated on silicon chips using integrated circuit technology.
7. How many detector elements are present in a matrix array solid state camera?
a) 156 x 156 per array
b) 216 x 216 per array
c) 116 x 116 per array
d) 256 x 256 per array
View Answer
Explanation: A typical matrix array solid state cameras have 256 x 256 detector elements per array. Solid state cameras are small and rugged. Sensors of solid state cameras are do not wear out with use. There is very less image distortion in solid state cameras because of placement of photo detectors accurately.
8. What is the common rate of an image forming in a camera?
a) 20 images per second
b) 30 images per second
c) 25 images per second
d) 50 images per second
View Answer
Explanation: A camera may typically form an image 30 times per sec i.e. at 33 m sec intervals. At each time interval the entire image has to be captured and frozen for processing by an image processor. An analog to digital converter is used to convert analog voltage of each detector into digital value.
9. What is windowing?
a) Technique used to concentrate the processing in a desired area of an image
b) Technique used for image restoration
c) Technique for image analysis
d) Technique to describe and measure the properties of image features
View Answer
Explanation: Windowing is a technique used to concentrate the processing in a desired part of image and also ignoring the non-desired part or non-interested part of the image. In this, an electronic mask is created around a small area of an image.
10. Which of the following method is used to reduce processing of image?
a) Triangulation technique
b) Digital imaging technique
c) Run length encoding
d) Stereo vision
View Answer
Explanation: General techniques to reduce processing are edge detection and run length encoding. In run-length encoding, each line of the image is scanned, and transition points from black to white or vice versa are noted, along with the number of pixels between transitions.
11. What is stadimetry?
a) Direct imaging technique in which distance is judged by apparent object distance
b) Indirect imaging technique in which distance is judged by apparent object distance
c) Direct imaging technique in which distance is judged by actual distance of the object
d) Indirect imaging technique in which distance is judged by actual distance of the object
View Answer
Explanation: Stadimetry is a technique used to determine the object distance from a vision system camera. It is a direct imaging technique in which distance of the object is determined by the apparent size of object in the field of view of camera.
12. Which method is not used to determine object orientation?
a) Equivalent ellipse
b) Triangulation technique
c) Structured light method
d) Light intensity distribution
View Answer
Explanation: Measuring the distance of an object from a vision system camera, determining object orientation, and defining object position are three important tasks performed by machine vision systems. The object orientation can be determined by the methods of an equivalent ellipse, the connecting of three points method, light intensity distribution and structured light method.
13. Which method is used for interpreting images?
a) Light intensity distribution
b) Stereo vision
c) Optical computing
d) Template matching
View Answer
Explanation: Template matching and feature weighing are the most commonly used methods of interpreting images. In template matching a mask is generated electronically to match a standard image of an object.
14. What do you mean by image interpretation?
a) Identification of type of image
b) Identification of an object based on recognition of its image
c) Identification of color content of image
d) Identification of each pixel of image
View Answer
Explanation: Image interpretation involves identification of an object based on recognition of its image. These results are then compared with a presorted set of standard criteria and the various conclusions are drawn.
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