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Novel latent fingerprint displaying method

A technology of latent fingerprints and fingerprints, which is applied in the field of electron beam evaporation metal films to show latent fingerprints, which can solve the problems of excessive thickness of the coating and restricting applications.

Inactive Publication Date: 2013-12-25
CHINA MARITIME POLICE ACADEMY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Due to the lack of precise control and quantitative devices in the resistance heating evaporation coating method, it is easy to cause the coating to be too thick and cover the fingerprint lines without seeing the lines
In addition, many working conditions are set by the operator's experience, such as the size of the evaporation current, the metal deposition time, the distance and angle between the fingerprint object and the evaporation source, the amount and time of the evaporated metal, etc., which largely restrict the Application of this technology in fingerprint inspection

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0020] This embodiment provides a method of evaporating Cu (25nm) on a glass substrate to reveal 24h internal sweat latent fingerprints.

[0021] Step 1. Press the sweat submerged fingerprint on the glass substrate, put the sample into the vacuum chamber, put the copper target into the crucible at the same time, and close the vacuum chamber;

[0022] Step 2 Turn on the vacuum pump and pump the vacuum in the vacuum chamber to 10 -3 below pa. The substrate temperature is at room temperature, turn on the electron gun, and use electron beam to evaporate Cu;

[0023] Step 3: Open the baffle in front of the sample, the substrate temperature is at room temperature, start to deposit Cu film on the surface of the sample, use crystal controller to monitor the film thickness in real time, when the Cu film thickness is 25nm, close the baffle, and turn off the electron gun;

[0024] Step 4 Observe the fingerprint display effect from the observation window, turn off the vacuum pump, and f...

Embodiment 2

[0027] This embodiment provides a method for evaporating Au(5nm) / Cu(20nm) on a ceramic substrate to display sweat latent fingerprints left for 30 days.

[0028] Step 1: put the sample that was pressed on the ceramic substrate 30 days ago into the vacuum chamber, put the gold target and the copper target into the two crucibles at the same time, and close the vacuum chamber door;

[0029] Step 2 Turn on the vacuum pump and pump the vacuum in the vacuum chamber to 10 -3 Below pa, the substrate temperature is room temperature. First turn the crucible with the gold target under the electron gun, turn on the electron gun, evaporate the gold film with the electron beam, open the baffle in front of the sample, start depositing the gold film on the surface of the sample, and monitor the film thickness with an electronic crystal controller. When the film reaches 5nm, close the baffle in front of the sample and close the electron gun;

[0030] Step 3 Transfer the crucible with the copp...

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Abstract

The invention discloses a method for displaying a latent fingerprint by using an electron beam vapor plating metal film, and belongs to the forensic science field. The method is characterized in that the electron gun vapor plating metal film is mainly adopted, and a difference between the deposition rates of the metal film on fingerprint lines and an object is utilized to form a contrast between the fingerprint and a background, so the fingerprint can be displayed. Electron beam vapor plating gold and copper films can be adopted to display new or old sweat latent fingerprints on smooth non-permeable objects comprising glass, ceramic, photograph paper, plastics and the like. The method can realize the nontoxic lossless controllable low-background-interference display of the latent fingerprint, and is in favor of researches after the display of the fingerprint, for example whether forbidden medicines, drugs or explosives are contained in the fingerprint or not, and the researches will have important application values.

Description

technical field [0001] The invention relates to the field of forensic science, in particular to a method for displaying latent fingerprints by evaporating metal films with electron beams. Background technique [0002] With the development of vacuum technology in the electronics industry, the research on applying vacuum coating technology to fingerprint display has also attracted widespread attention. At present, the vacuum coating technology applied to fingerprint display mainly adopts the resistance heating evaporation method. The deposition effect of the evaporated metal material on the fingerprint line and the object is different, so that the fingerprint and the background form a contrast, and the fingerprint can be displayed. However, the temperature that can be reached by resistance heating evaporation coating is low, so the metal that can be evaporated is also limited. In addition, some metals are easy to form alloys with the heating wire, which shortens the life of t...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23C14/30C23C14/14A61B5/117G06K9/00
Inventor 王海平
Owner CHINA MARITIME POLICE ACADEMY
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