A reticle is an internal reference
An internal reticle is seen with the instrument image. An external test target is placed in the object scene. Choose the product around that optical role before selecting a pattern.
Classify the function before choosing geometry
Match the visible reference to the quantity being read: a centre, length, angle, sampled area or comparison class.
| Pattern function | Primary output | Product choices |
|---|---|---|
| Aiming and alignment | Centre, axis or offset | Crosshairs, quadrants and concentric circles |
| Measurement and scale | Length or angle after calibration | Micrometer scales, crossed scales and protractors |
| Counting and sampling | Defined fields or method-specific estimates | Counting grids, points and test lines |
Define the focal plane and substrate stack
The patterned film, glass thickness, seat and any bonded cover form one optical stack. Its reference plane determines how the pattern is seen with the target image.
Position accuracy and line width are different
Line width governs visibility; pitch governs repeated intervals; placement locates the pattern to the instrument datum. State and inspect these quantities separately.
Eliminate parallax at the instrument
A clear pattern and a clear target can still move relative to one another when the eye moves. Eyepiece focus and target-plane alignment address different conditions.
Calibrate measurement and counting patterns
Length scales need an instrument-specific conversion. Volume counting also needs the sampled area, chamber depth and dilution. The reference geometry and the reported result are connected by the measurement method.
Specify illumination and polarity
Choose clear or opaque features for the actual wavelength, viewing side and illumination geometry. Transmission density and reflected contrast describe different optical behaviour.
Use a release checklist
Connect the drawing revision, pattern dimensions, mounting datums and inspection record. Then verify focus, orientation and readout in the assembled instrument.