Application of multi-band light source in the crime scene investigation 2

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3,Change the output wavelength, multiple search if there is a new discovery. For the fingerprint manifest, it could be better to bring the evidence materials back to the laboratory to examine if possible; if not easy to carry back, using fluorescent powder, fluorescent magnetic powder or other method to manifest the fingerprints, brush color powder should be according to the characteristics of the powder and select excitation wavelength, one side we must observe, one side brush, if strong fluorescence background, interference fluorescence fingerprint, should change another kind of powder and excitation wavelength.

Application of multi-band light source in the crime scene investigation 1

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1. First searching: enter the crime scene, with the white light of multi-band wavelengths for the first investigation, the purpose is to explore if there is any footprints, fingerprints, hair, fiber, or glass pieces, etc. trace evidence, which is based on the material evidence of light scattering principle.
2. Second search: after the white light searching, it will be scene as possible shading, it will be better to search again, with blue and green light output of multi wave band light source, by wearing orange glasses for the second round of the crime scene investigation, because many suspicious substances will emit a inherent fluorescent, such as body fluids, fiber, fat and so on. If there is a dead body, using blue and green light on the body and clothes to check the semen stains, saliva, hair, fiber, scars or bite marks.
   

   

multi-wavelengths light source features 2

The application of optical technology is used widely in the field of criminal science widely, for a lot of material evidence detection, various optical detection method is routine first step, it has the characters of high sensitivity and no damage to the test materials, with the continuous application of laser in the field of material evidence detection, various kinds fluorescence methods gradually recognized by the people. The laser is used as excitation light source, which is characterized by high intensity and high monochromaticity. But the disadvantage is that it has only 1 band or 2-3 bands, including UV, blue laser, green and red, etc. The main advantage of the multi wave band light source is that it has multi-wavelength output, the wave bands setting according to various fingerprint substance absorption spectrum, so you can more effectively stimulate the fluorescence fingerprint. In addition, the multi band light source is low in price and easy to carry, suitable for using at crime scene, compared to the laser, the multi band light source intensity is low, but because of higher wavelength selectivity, and its perfect excitation effect.

multi-wavelengths light source features

Multi-wave band light source: in nature, various substances of light absorption and emission properties are different, especially some fluorescent substances, they only produced in certain specific wavelengths of fluorescence excitation of certain wavelengths of light. If according to the absorption and emission spectra of different substances to choose the appropriate wavelength of the excitation light, which can effectively stimulate the substance that itself has the fluorescent substance or drug show fluorescence, so as to form a strong contrast with the background, highlighting the apparent effect. Multi wavelength light source that according to this principle to design and develop, it will be the source of high intensity light a full spectrum line light, through the special interference filter, the output monochromatic light with different wavelengths, effectively stimulate fluorescent substances, as far as possible to reduce the influence of the background object materials of traces, in order to achieve the purpose of evidence search and detection.

What is the forensic multi-wavelengths light source?

Multi-band light source is usually caused by one or two groups of specially designed optical filters, white light emitted from the light source ( full spectrum ) into different bands of monochromatic light, then the light output by the light pipe, such an optical system to be known as multi-band light source. The system consists of light source, optical filter and the light pipe. The light source is generally divided into metal halide lamp or xenon lamp, sufficient intensity light output; And usually use high-quality and band-pass interference filters, ensure that the output light monochrome; The light pipe can be divided into two kinds of optical fiber and liquid light guide, to facilitate on-site related evidence search, inspection and photographic evidence with the help of light. Searching and detecting of latent fingerprint by multi-band light source at the crime scene, the most important is the choice of excitation bands and receiving bands.

Fornesic light source Outline

Forensic Light Source

Multi-band scene investigation emerged in recent years is a new forensic light source , it is ideal for scene investigation and evidence examination, it has become an essential equipment for criminal investigation department in recent years. Multi-band light source used in the fingerprint detection , but also for detecting and searching on-site footprints , blood, semen stains , body fluids, narcotics, fiber, and trace evidence of gunpowder residue, and, for inspecting the disappears, altered handwriting or other documents are also very effective.