A reflective glass scale presents high- and low-reflectance regions to a source and detector on the same side. The matching readhead uses the changing reflected intensity to read position.
Choose it when the reader is designed for one-sided optical access and its wavelength, illumination angle and sensing window match the coating and pattern.
Reflective and transmissive are optical geometries, not encoding methods. Both can use a periodic grating or an absolute code when paired with a suitable reader.
High/low reflectance, track layout, active length, reference geometry and the mounting face are defined together with the reader collection geometry.
A patterned glass scale with the selected measuring length, code or grating layout, reference marks and component inspection records.
| Substrate | B270 / K9 / soda-lime glass; fused silica by request |
|---|---|
| Pattern medium | Chromium-on-glass or a specified clear/opaque pattern |
| Photolithographic line-width tolerance | ±0.2 µm |
| Mechanical cutting accuracy | ±0.02 mm |
| Thickness | ≥0.4 mm |
| Total thickness variation (TTV) | ≤2 µm |
| Surface figure | λ/4 |
| Optical mode | Reflective; source and detector on the same side |
| Active scale length | Defined by the approved drawing |
| Reference-mark position | Defined from the mounting datum |
A disc or scale is the passive optical reference inside a larger encoder system. The artwork, readhead and mounting datum must be designed together so that the manufactured pattern is read in the intended direction and at the intended contrast.
| Property | Specification |
|---|---|
| Position encoding | Incremental grating or approved absolute code sequence |
| Optical acceptance | High/low reflectance at the specified wavelength and incidence angle |
| Critical geometry | Pitch, duty cycle, active length, track width and pattern-to-datum position |
| Readhead interface | Patterned face, sensing window, reading direction and operating gap |
System resolution and system accuracy are separate from the manufactured CD and outline values. Interpolation, bearing runout, eccentricity, alignment and electronics contribute to the final error budget.
Custom reflective glass scales for optical linear encoders with the source and detector on the same side. High- and low-reflectance pattern regions are specified together with the readhead wavelength, angle and sensing gap.
Specify both reflectance levels at the intended wavelength and angle. The detector receives light through its aperture, so surface reflectance and usable signal contrast are related but distinct quantities.
Understand how optics and coating shape the signalTransparent areas can expose a rear surface or mounting background. Those reflections must be included when evaluating the installed signal.
Relate scale pitch to output resolutionInspect pattern dimensions, cumulative interval error and registration to the mounting datum. Measure both bright and dark reflectance under the agreed optical geometry, and examine scratches, contamination and coating defects in the read zone. Readhead signal validation belongs to the assembled system and should use the intended mounting gap and illumination.
| Property | Specification |
|---|---|
| Pattern dimensions | Measured CD at agreed locations; report nominal and measured values |
| Outline geometry | Outer diameter, bore or scale length checked to the mechanical drawing |
| Registration | Pattern origin, track-to-bore or pattern-to-datum position |
| Optical defects | Clear/opaque defects, broken lines, pinholes and contamination |
| Traceability | Drawing revision, lot identification, inspection method and report |
| Property | Specification |
|---|---|
| Geometry | Disc outer diameter and bore, or scale length, width and thickness |
| Pattern data | Approved artwork or code map, line count/pitch, polarity and revision |
| Optical interface | Transmissive or reflective mode, wavelength, contrast and readhead gap |
| Datum scheme | Mechanical datum, pattern origin, index/zero position and orientation |
| Acceptance record | CD measurement, cutting dimensions, registration, defects and report format |
Specify substrate material and geometry together with the operating wavelength. For transmissive reading, define clear-area transmission and opaque-track density. Reflective reading also needs the high/low reflectance pair and illumination geometry. Optical contrast must match the readhead, not only the appearance of the part.
Compare glass scale readout and encoding optionsQuality & Inspection PhotolithographyReflective patterns for compatible readheads on one side of the scale.
Reflective glass scales use surface reflectance differences to provide a position pattern to a head on the same side.
Specify wavelength, incidence angle, reading face and window together with the required contrast, then define pitch or code and datums.
Wavelength, incidence angle, reflective contrast, film side, pitch or coding and mounting margins.
The light received by the head depends on the optical arrangement. Angle and reading side connect the film requirement to the actual detector geometry.