LED light source application advantages in criminal technology

The light source equipment plays a huge role in the search of potential traces of crime scenes, physical evidence test identification and criminal photography. It can not only effectively improve the extraction rate and utilization rate of on-site trace evidence, but also provide more reliable technology for the detection of cases. Means and accurate evidence information.

Application of light source equipment in criminal technology

1. 1 The appearance of potential traces of evidence at the crime scene

As a place and place for carrying criminal facts, the crime scene contains a large amount of criminal information and evidence. The quality of crime scene investigation and the complete extraction of potential trace evidence on the spot are the key to whether the case can be successfully detected. The use of specific light source equipment can effectively stimulate the inherent fluorescence of fingerprints, footprints, bloodstains and fiber traces left on the crime scene, so that different traces of evidence can respond under the illumination of specific wavelengths, which is convenient for the discovery and search of on-site trace evidence. Improve the visibility and collection rate of potential trace evidence on site.

1. 2 Application in the identification and identification of physical evidence

The use of optical inspection has high sensitivity and does not impair the characteristics of the sample. At present, the use of criminal technology light source equipment in the verification of physical evidence has expanded from fingerprint inspection, document inspection, textile inspection to body fluid inspection and ammunition residue inspection.

1. 3 Criminal photography applications

The light source is also an important part of the criminal photography equipment. A good physical evidence source is also very important for solving the extraction and preservation of the traces of the traces of potential and difficult objects. Photographic photography, color separation photography, and polarized light photography from visible light. , to the special camera infrared reflection, ultraviolet reflection, infrared fluorescence, ultraviolet fluorescence photography, can use different light sources to get a good test photo effect.

Criminal technology light source equipment requirements

The promulgation of the new Criminal Procedure Law has stricter requirements on the standardization and scientific nature of the on-site investigation of criminal technicians in public security organs. The high-quality on-site investigation standards and the updating of inspection equipment also put forward higher requirements on the performance of light sources, so the existing criminals The problems of low accuracy, large volume and incomprehensibility of technical light source equipment have also become prominent, which has become an important issue restricting the development of criminal technology.

To solve this problem, we must first improve the practicality and accuracy of the inspection equipment, which will be the main direction of equipment development. Secondly, the miniaturization and multi-functional integration of the equipment in the grassroots work can reduce the quality and efficiency of the survey. The labor intensity of small technicians; and the popularized and popularized equipment with simple operation and wide application will be the trend of development in the future. At present, the existing light source equipment is not enough to meet the needs of current high-quality on-site exploration and inspection and identification technology. Therefore, the technical means and device performance are continuously improved and enhanced, and the development of energy-saving and high-efficiency new light source equipment is used to improve the grassroots criminal technical department. The ability and level of on-site investigation, inspection and identification of physical evidence will have a great effect.

Spectral characteristics of LED spectrum modulated light source technology

Common lighting LEDs are based on the basic chromaticity theory that produces white light. The weakness is that the color coverage that can be expressed is incomplete, and conventional LED light sources are difficult to handle in environments where a specific spectrum is required or even multiple spectral transformations are required. Light source and equipment requirements in the field of criminal technology enable people to highlight the response of specific materials to light colors. The use of spectrally modulated light sources for on-site illumination, the use of purely physical methods for full-spectrum acquisition of the target, and the reproduction of the acquired spectral information in an appropriate manner, this method can theoretically achieve perfect on-site record preservation and reproduction, and ultimately Realize the integrity of on-site image information. The research of this technical solution may be able to establish a complete set of technical tools in criminal science and technology research practice in the future.

In terms of spectral acquisition, image data with high spectral resolution accuracy can be obtained due to the presence of high-selective visible light-narrow filter, and image data can be acquired at different wavelength intervals in the visible range. However, the modulation of the spectrum of the light source is limited by the lack of the basic spectrum. The experimental research is still relatively few. The wavelength range covered by the current LED technology is as shown in the figure below. The luminous efficiency of the LED near the yellow-green light is relatively low, and the optional types are not complete.

LED light source application advantages in criminal technology

At present, the traditional criminal technology light source needs to be equipped with a huge power system, a light source system (halogen lamp, fluorescent lamp, high pressure sodium lamp or xenon lamp), a filter system (filter lens filter), etc., so such a light source device is generally unsatisfactory. The shortcomings of light selectivity, low light-filling efficiency, short life, high heat generation, high power consumption cost, and high maintenance cost have caused great troubles for grassroots case handlers, and as a new type of criminal technology light source, Compared with traditional light sources, LED light sources have incomparable advantages:

(1) The spectrum is narrow, the energy utilization rate of the light source can exceed 36%; no filter system is needed, and only different combinations of LED light sources of different wavelengths can be selected for different conditions, and the spectrum can cover red, yellow, green, blue, purple and ultraviolet ranges. Light intensity, light quality, and photoperiod can be adjusted;

(2) High photoelectric conversion efficiency, low cooling load, energy saving, energy saving and environmental protection;

(3) As a cold light source, it can be irradiated at a close distance, which improves the space utilization rate;

(4) Using LED as the light source for on-site survey, it also has the advantages of maintenance-free and long life. The service life is over 50,000 hours. It does not need to be warmed up when it is used.

(5) Using ultra- high - power LED light-emitting diode array manufacturing technology, it can also realize ten-hundred-watt-level intensity-adjustable light source module, which can effectively excite weak fluorescence, and can be realized through basic materials, chip design and packaging technology. Higher light purity, improved evidence discovery rate and differentiation ability. The introduction of new packaging and thermal management technology can not only provide integrated application of single-source multi-spectral, but also optimize the design of spot shape and intensity distribution through optical path design, combined with large output power to achieve fast on-site search;

(6) The LED light source avoids the potential danger caused by the fragile power system, the light source system and the filter system, has wider adaptability to the ambient temperature, greatly reduces and reduces the weight and volume, and has the advantages of convenient carrying and vibration resistance. It is more suitable for the actual needs of long-term outdoor site surveys. The new technical solution can make the LED light source system have higher integration, lower cost and high security. It is also more conducive to the design of the light source structure, while retaining the biometric information such as DNA of the physical evidence, and at the price. , operability and other aspects have obvious advantages.

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