Radial divisions and an angular scale provide a reference around a defined centre. Full-circle and sector layouts serve different viewing tasks.
Specify optical glass or fused silica, overall dimensions, thickness, pattern-side orientation and the clear aperture. Define transmission, reflectance or optical density at the working wavelength when optical contrast is critical.
A protractor pattern compares edges or axes in the observed image with an angular reference. It is useful for measuring microscopes and profile comparison when the feature and reference share a defined viewing plane.
Optical references in measuring instrumentsAn in-plane angle can be preserved by uniform magnification, but tilted objects and unequal X/Y scaling change the projected angle. Zero direction, image rotation and optical distortion must be checked independently of graduation spacing.
Check alignment in the complete instrumentRadial divisions and an angular scale provide a reference around a defined centre. Full-circle and sector layouts serve different viewing tasks.
Use a protractor pattern when orientation or an included angle is the observation of interest, such as comparing edges and aligning a visible feature to an angular reference.
A protractor reads direction or included angle in an image plane. A length scale reads distance after calibration; concentric rings compare centre and radial extent. Out-of-plane tilt can change the projected angle.
Line geometry, graduations, labels, field diameter, substrate thickness and mounting outline can be matched to the instrument. Contrast and line density should allow the reference and the specimen to remain visible together.
A patterned glass reference component with the selected graduations, outline and mounting dimensions, accompanied by the specified inspection records.
Angular divisions for orientation comparison.
Angular graduation reference around a defined centre.
Protractor reticles use radial lines and angular graduations as references for direction and included angles.
Define the angular range, smallest graduation, numbering direction and centre location relative to the instrument mount.
Angular range, division spacing, zero direction, labels, centre and substrate dimensions.
The workpiece and scale must share the intended viewing geometry, centre and zero direction. Interpret the reading in the instrument configuration.