High Precision Transparent Film Ruler for Dimensional Inspection and Accuracy Verification

The Film Ruler is a high-precision optical reference tool commonly used for dimensional inspection, alignment calibration, and accuracy verification. In simple terms, it can be understood as a "transparent ruler with precise scales," but its precision and manufacturing process far exceed those of ordinary rulers.

Professional customization is supported to meet specific application requirements.

Film rulers are typically made of high-precision film or glass substrates, with micron-level or even submicron-level engraved line patterns fabricated on the substrate surface through photolithography or laser direct writing processes. The core principles mainly include the following three aspects:

1. Optical Contrast Principle: A distinct optical contrast (light transmission / light blocking) is formed between the engraved line area and the transparent area, allowing the scale position to be clearly identified under a microscope or visual inspection system.
2. Precision Pattern Transfer Principle: Using technology similar to semiconductor photolithography, the designed standard scale patterns are accurately transferred onto the film or glass, thereby ensuring high consistency and traceability of dimensions.
3. Visual Measurement Benchmark: In inspection equipment, the film ruler serves as a "standard reference" and compares the actual product dimensions through image recognition algorithms to achieve calibration or error measurement.

1. High Precision: Engraving accuracy can reach ±1 μm or even higher, making it suitable for precision inspection scenarios.
2. Good Dimensional Stability: Glass film rulers offer a low thermal expansion coefficient and better stability; PET / film rulers offer good flexibility but slightly lower stability.
3. High-Resolution Engraved Lines: Engraved line width can be as small as several microns, suitable for recognition by high-magnification visual systems.
4. Lightweight and Easy to Use: Compared with traditional metal or glass rulers, film rulers are light in weight and easy to carry.
5. Relatively Low Cost: Especially for film materials, they offer higher cost performance compared with grating rulers or laser interferometers.
6. Strong Customizability: Can be customized according to requirements — different scale intervals (such as 0.01 mm, 0.02 mm), cross targets, alignment marks, and special patterns such as grids, circles, and concentric rings.

The film ruler is effectively an "invisible ruler" in many precision industries. Common applications include:

1. PCB and FPC Industry: Circuit board dimensional inspection, exposure alignment calibration, graphic scaling error verification.
2. Display Panels (LCD / OLED): Mask alignment inspection, pixel pitch calibration, AOI visual system calibration.
3. Semiconductor and Photolithography Field: Photomask accuracy verification, alignment system calibration.
4. Machine Vision and Automation Equipment: Camera calibration (conversion between pixels and actual dimensions), accuracy verification.
5. Precision Printing and Plate-making Industry: Screen printing alignment, printing registration inspection.
6. Laboratory and Metrological Inspection: Microscope scale calibration, optical measurement system benchmark.