Quiz 1

Correct answer:A.Fully close the lens aperture.

The conditions for a larger depth of field are:

1. A lens with a shorter focal distance
2. A larger working distance
3. A narrower aperture.

If you need a greater depth of field, check whether the conditions above are applicable.

Correct answer:A.1.2 mm (0.047")

The field of view when using a macro lens can be calculated with the following formula:
CCD size (Y) / optical magnification (3.6 (0.14")/ 3 = 1.2 mm (0.047").

Correct answer:A.F-number of 1.4

An F-number (F No) is a value to indicate the light-gathering ability of a lens.
The faster a lens is, the smaller the F-number.

Correct answer:B.Low-angle illumination

Low angle lighting emits light onto the surface that will reflect the emitted light at the same angle back to the camera. Therefore, a camera mounted directly over the top of the target receives a diffuse reflection from the flaws on the surface, causing them to appear as a different shade then the rest of the target surface.

Flaw

Correct answer:A.Yes

LED light sources generally have a long lifespan and stable switching characteristics. Since overheating is a major cause of reduced lifespans of LEDs, it is advisable to strobe the LED illumination unit in order to dissipate between each inspection.

Correct answer:B.Polarizing filter

A dark filter simply reduces the amount of light received. This does not have a positive effect for inspections through plastic film. On the other hand, polarizing filters reduce glare by lining up the direction of light from the illumination source and the lens. The example images to the right show that the image of an electronic component through film is more clearly captured.

Correct answer:B.Indirect illumination

When light is emitted directly on the glossy cylindrical-shaped target, the light is reflected irregularly as shown in the left image. On the other hand, when light is indirectly emitted, an evenly lit image can be captured as shown in the right image.

Correct answer:A.0.1 mm (0.004")

Resolution refers to a value indicating how many mm a pixel represents when capturing an image in a certain FOV. This value can be obtained using the following formula: = FOV (mm) / the number of pixels.
The resolution is 0.1 mm (0.004"), 48 mm (1.89")/ 480 pixels.

Correct answer:A.2.5 μm (0.1 mil)

Based on the formula in Question 11, it is 5 mm (0.2") / 2000 pixels = 0.0025 mm (0.0001") = 2.5 μm (0.1 mil)

Correct answer:B.600 m (1969’)/min.

The fastest speed of a production line (the fastest speed at which an inspection can be performed) is determined by the necessary area to be measured (100 mm in this example). In order to cover the FOV of 100 mm (3.94") at the processing speed of 10 ms, the highest speed of the production line (min.) can be obtained from the following formula:100 mm (3.94")/ 0.01 sec. × 60 sec. = 600,000 mm (23,640") 600 m (1970’)

Correct answer:B.1/10000 sec.

In order to determine the fastest shutter speed (the exposure time required to capture the target), it is necessary to know the acceptable amount of blur (0.1 mm in this example) and the production line speed (1000 mm/sec. in this example).
Minimum shutter speed = 0.1 mm (0.004") / 1000 mm (39.37") = 1/10000 sec.

Correct answer:A.Geometry search

This is generally called geometry search or profile shape search. Geometry search searches for targets based on profile information. Even if a part of the target is missing, it allows accurate search by using the remaining information. As a result, it has become a mainstream of search processing in recent years. Normalized correlation search has been used for a long time. Although it may be affected when a part of the target is missing, it is the most commonly used method because it allows accurate search without being affected by variations in ambient brightness.

Correct answer:A.Expansion filter

By using the Expansion filter, the intensity of the center of a 3 × 3 area is replaced with the maximum intensity among those 9 pixels including the center pixel. As a result, the pixels with lower intensity (fine black noise) are replaced with the value of the surrounding higher intensity pixels. In contrast, the Shrink filter replaces the intensity of the center pixel with the minimum intensity (the darkest value).

Correct answer:B.Mechanical vignetting

Mechanical vignetting is a phenomenon that occurs when the lens is too small for the camera’s CCD. Recent high-resolution cameras tend to have large CCD elements, which makes it necessary to confirm the appropriate size of the lens used in advance.

Correct answer:A.Checks whether printed characters correspond with the originally intended content.

With OCV, the correct character strings are programmed in advance, and verification is performed on images captured by the machine vision system. OCV is commonly used for inspections of expiration dates. OCR reads marked characters and then outputs to external devices for classification, verification, and other control processes.

Correct answer:C.Dependant on the FOV

The minimum detectable object is determined by two factors, the X-Y range needed to be measured by the camera (the FOV) and the number of pixels of the camera to be used. It can be derived with the following formula: the Y-direction of the FOV (mm) / the number of pixels the CCD has in the Y direction.

Correct answer:B.Illumination

There are some situations where A and C are just as important as illumination. However, without the proper illumination, inspections cannot be stably performed with machine vision. Recent advancements in pre-processing filters have aided in stabilizing inspections when lighting is not 100% repeatable, but choosing the correct light source is still the most important.