Mitutoyo - Полный каталог инструмента - 2014 Английский язык
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High-Resolution Measurement Composite Coordinates of a Point
When enlarged... Machine coordinate system Vision coordinate system
M
Mz Vx
My V
Vy
Greyscale Mx
Greyscale
Tool position Tool position
A position the system recognizes as an edge Measuring machine stage Detected edge position (from
may be in error by up to one pixel width using position the centre of vision)
normal image processing. This will prevent the M = (Mx, My, Mz) V = (Vx, Vy)
execution of high-resolution measurement.
To increase the accuracy in edge detection, sub-pixel image processing Actual coordinates are given by X = (Mx + Vx), Y = (My + Vy),
is used. An edge is detected by determining an interpolation curve and Z = Mz, respectively.
between adjacent pixel data as shown below. This technique allows
measurement with a resolution higher than 1 pixel. Since measurement is performed while individual measured positions
are stored, the system can measure dimensions that cannot be included
in one screen.
Greyscale Tool position The image signal profile Principle of Auto Focusing
GreyscaleImage signal withoutapproaches an analog
sub-pixel processing waveform like this. The system can perform XY-plane measurement, but cannot perform
Tool position height measurement using only the CCD camera image. The system
is commonly provided with the Auto Focus (AF) mechanism for height
measurement. The following explains the AF mechanism that uses a
common image, although some systems may use an AF laser.
Image signal with sub-pixel processing The AF system analyzes an image while CCD Z
moving the CCD up and down in the Z coordinate
Measurement Along Multiple Portions of an axis. In the analysis of image contrast, In-focus
Image an image in sharp focus will show a height
peak contrast and one out of focus
Large features that cannot be contained on one screen have to be will show a low contrast. Therefore, Contrast
measured by precisely controlling the position of the CCD sensor and the height at which the image contrast
stage so as to locate each reference point within individual images. By peaks is the just-in-focus height.
this means the system can measure even a large circle, as shown below,
by detecting the edge while moving the stage across various parts of K
the periphery.
Variation in Contrast Depending on the Focus
Condition
Edge contrast is low due to Edge contrast is high due to
out-of-focus edges. sharp, in-focus edges.
High High
Low Low
Contrast in the scanning direction Contrast in the scanning direction
K-18
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