Forensic Optical Evaluation of Chinese Seal Impressions
Optical seal evaluation establishes chop authenticity through microscopic tool marks, spectral luminescence, and stroke intersection depth profiles before PRC courts.
Multispectral Illumination
Meaning
Advanced document analysis utilizing light across several discrete wavelengths is used to differentiate between distinct inks, paper fibers, and alterations on physical contracts. In industrial compliance audits, multispectral illumination exposes hidden layers, erased text, or composite stamps that are invisible to the naked eye under standard light. This technique allows examiners to evaluate the authenticity of corporate seals and signatures without causing any physical damage to the paper.
The scan identifies non-uniformity across the document’s surface.
Optical Mechanism
Varying the wavelength of light from ultraviolet to infrared excites different chemical compounds in the target substrate. When different light waves hit the paper, specific pigments fluoresce while others absorb the light or become transparent. For instance, infrared light penetrates many common ballpoint pen inks but is absorbed by carbon-based inks, revealing if a signature was modified or added later.
Ultraviolet light highlights regional differences in paper bleach, indicating where original text was mechanically or chemically erased.
Document Verification
Authentication of high-value trade documents relies heavily on the resulting spectral signatures to confirm the sequence of stamps and handwritten notes. When multiple inks or chops overlap on a disputed invoice, multispectral illumination helps separate the overlapping layers by filtering out specific wavelengths. This allows the examiner to capture separate images of each individual ink layer.
The analysis reveals whether the official seal was stamped before or after the handwritten text, exposing potential falsification of payment terms.
Forensic Admissibility
Procedural rules in administrative tribunals require standardized imaging protocols to ensure reproducibility. To be admitted as certified evidence in a contract dispute, the multi-wavelength scans must be captured by accredited forensic laboratories using calibrated equipment.