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User Manual S-23 HM 6 Vision functions Software Vers ion SR.405.xx 05/99 Iss ue 6.5 Teach Fiducial 211 6.5.5 Contrast Sensitivity Menu The Contrast sensitivity men u provid es options for optimiz ing the co ntrast bet we…

6 Vision functions User Manual S-23 HM

6.5 Teach Fiducial Software Version SR.405.xx 05/99 Issue

210

The uniqueness value appears as the measurement results. This may vary between 0 (= unsat-

isfactory) and 100 (= very good) differentiation capability. 6

Practice shows that a uniqueness value of at least 60 must be achieved for fiducials and ink dots. 6

È Repeat the teaching process a number of times with changed field sizes. In this way you can

optimize the uniqueness value.

È Press Esc to quit this option.

NOTE 6

If you wish to use a fiducial despite the fact that it has a low uniqueness value, you should

ensure that the fiducial has a good quality value (see Section 6.5.6.2 on page 221).

If the quality is bad as well, it would be better to select another fiducial (see Criteria for Cre-

ating Fiducials in Section 6.2.5 on page 176). 6

User Manual S-23 HM 6 Vision functions

Software Version SR.405.xx 05/99 Issue 6.5 Teach Fiducial

211

6.5.5 Contrast Sensitivity Menu

The Contrast sensitivity menu provides options for optimizing the contrast between the fiducial

and its surroundings. 6

NOTE 6

All of the options in this menu are only accessible if you have loaded a fiducial beforehand. If you

have done so, this will be indicated by the text on the button being black (rather than grayed out).

The fiducial number and fiducial name are displayed in the Fiducial display field.

If you have not loaded a fiducial you will only be able to select the Program transform 5 option. 6

Fig. 6.5 - 17 Contrast sensitivity menu, options

Each pixel of the video camera contains one unit of 8-bit gray-scale information. The significance

of the values is as follows: 6

0 = black and

255 = white

6 Vision functions User Manual S-23 HM

6.5 Teach Fiducial Software Version SR.405.xx 05/99 Issue

212

To make it easier for you to assess the range of brightness or the contrast, these gray-scale values

have been converted with the help of transformation tables into color as is shown below: 6

NOTE 6

In order to achieve a good uniqueness value the contrast difference between the fiducial and its

surroundings should be at least 75. For example, if the background is green the fiducial should be

orange. 6

If the contrast is unsatisfactory you can select in the menu between five pre-programmed trans-

formation tables in order to obtain a color image which is capable of supplying the necessary in-

formation. In addition, you can also program a transformation table yourself. 6

NOTE 6

When the color presentation is changed the fiducial will be taught at the same time. 6

Gray scale Allocated color

0black

30 violet

50 blue

77 blue-green

100 green

127 brown

150 red

175 orange

200 yellow

255 white

Tab. 6.5.1