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Multi-Band Police Light Source System: Top China Suppliers & Factory for Fingerprint Detection and Testing
Basic Structure and Principle of Multi-Band Light Source
🔌 A multi-band light source divides white light into different bands via color filters and outputs it through a light guide — consisting of five core parts: light source, filter system, output system, control display system, and cabinet.
A multi-band light source is an optical system that divides the white light emitted by the light source into different bands by one or two sets of color filters, and then outputs it through a light guide. It mainly consists of five parts: light source, filter system, output system, control display system, and cabinet. Among them, the light source, filter system, and output system are the core parts of the multi-band light source, which determine the performance of the light source.
The light source generally adopts xenon lamp, indium light or other metal halide lamps with high luminous efficiency. The filter system mainly refers to the color filter — there are ordinary coated color filters or high-quality band-pass interference color filters. The performance of the latter is much better than that of the former, which mainly reduces the cut-off bandwidth of the colored light, meaning the monochromaticity of the colored light is greatly improved.
The usual output wavelength coverage is 350–1000 nm, including most of the spectral lines in the long-wave ultraviolet, visible light, and near-infrared regions.
Application Principle of Multi-Band Light Source
1. Fluorescence and Multi-Band Light Sources
When the extranuclear electrons are excited and jump to the excited state, the electrons in the excited state are unstable and always jump back to the ground state with lower energy. During the jump, the received energy will be released in the form of photons. The phenomenon that a substance is excited to an excited state after being irradiated by a photon of a certain wavelength, and then jumps back to a lower energy level by releasing a photon of another specific wavelength is called the photoluminescence phenomenon.
⚡ Fluorescence: photon lifetime < 0.000001 second | Phosphorescence: between 0.0001 and 0.1 second
If a substance can self-excite and produce fluorescence without external light excitation, it is said that the substance has intrinsic fluorescence. Another situation of fluorescence is to generate light waves with different wavelengths from the original light waves (usually short-wave excitations to generate long waves) under the excitation of an external light source, and the macroscopic manifestation is to emit another color light. The multi-band light source can provide not only an inverse light source for observing intrinsic fluorescence, but also an excitation light source.
2. Color Separation Principle
The principle of color separation is the prerequisite for the correct selection of the wavelength band (color light) and color filter of the multi-band light source. It means that by selecting shades, the appropriate spectral band can be isolated for precise forensic and scientific applications.
Forensic Multiband Light Source Filters
Filter Specifications
| Process | (IAD Hard Coating) |
| Substrate | Pyrex, Fused Silicon |
| FWHM | 30 ± 5 nm |
| CWL (nm) | 365, 415, 450, 470, 490, 505, CSS510, 530, 555, 570, 590, 610 |
| T avg. | >80% |
| Slope | 50% ～ OD5 < 10 nm |
| Blocking | OD = 5–6 @ 200–800 nm |
| Dimension (mm) | Φ15, Φ21.2, Φ25, Φ55, etc. |
Production Process
Frequently Asked Questions (FAQ)
Q
What is a multi-band light source and how does it work?
A multi-band light source is an optical system that splits white light into specific wavelength bands using one or two sets of color filters, then delivers the filtered light through a light guide. It covers a wavelength range of 350–1000 nm, spanning UV, visible, and near-infrared regions.
Q
What types of light sources are used in multi-band systems?
Multi-band light sources typically use high-luminous-efficiency lamps such as xenon lamps, indium lamps, or other metal halide lamps. These provide a broad and stable spectrum suitable for forensic and scientific applications.
Q
What is the difference between ordinary color filters and band-pass interference filters?
Ordinary coated color filters provide basic wavelength separation, while high-quality band-pass interference filters offer significantly improved monochromaticity by narrowing the cut-off bandwidth. This results in purer, more precise color light output for demanding forensic investigations.
Q
What is the difference between fluorescence and phosphorescence?
Fluorescence occurs when a substance releases photons with a lifetime of less than 0.000001 seconds after excitation, while phosphorescence has a photon lifetime between 0.0001 and 0.1 seconds. Multi-band light sources can serve as both excitation and inverse light sources for observing these phenomena.
Q
What are the key specifications of forensic multiband light source filters?
These filters feature IAD hard coating, Pyrex or fused silicon substrates, a FWHM of 30 ± 5 nm, average transmission greater than 80%, blocking of OD 5–6 across 200–800 nm, and are available in multiple center wavelengths (365–610 nm) and standard dimensions.
Q
Why is the color separation principle important when using a multi-band light source?
The color separation principle is essential for correctly selecting the appropriate wavelength band and corresponding filter for each specific application. Proper selection ensures accurate illumination and maximizes the contrast and visibility of evidence or target materials under examination.