A planar footprint collection device and its use method

Abstract

The present invention discloses a planar footprint collection device and a method of using the same, and belongs to the field of criminal investigation equipment. The collection device includes a base frame, a load-bearing plate, a liquid crystal diaphragm, an image sensor, a light distribution source, and a belt transmission mechanism; a load-bearing plate is laid on the base frame, and a liquid crystal diaphragm is tightly attached to the load-bearing plate. An image sensor that can move in its length direction is provided above the liquid crystal diaphragm, and a light distribution source is provided next to the image sensor. The image sensor is fixed to the bottom of the moving beam of the belt transmission mechanism, and the belt transmission mechanism is installed on both sides of the base frame. The present application accurately converts footprint pressure information into image information and truly restores the footprint image; an effective collection area can be constructed on a large scale according to demand, and the liquid crystal diaphragm used has no splicing breakpoints, and the footprint information is completely retained.

Description

Technical Field

[0001] The invention relates to the field of criminal investigation equipment, and in particular to a planar footprint collection device and a use method thereof. Background Art

[0002] As an important trace information reflecting human biological characteristics, footprints have received widespread attention at home and abroad. Especially since the 1980s, footprint inspection technology has been continuously developing in the direction of quantification and automation, playing an important role in actual case handling. In the field of criminal investigation, the study of flat footprints is extremely critical, but there is currently no device that can fully collect and obtain long-format footprints. Summary of the invention

[0003] The purpose of this application is to provide a planar footprint collection device and a method of using the same, which can construct a large-scale effective collection area according to demand. The liquid crystal film used has no splicing breakpoints and completely retains the footprint information.

[0004] To achieve the above-mentioned purpose, the technical solution of the present application is: a planar footprint collection device, including a base frame, a load-bearing plate, a liquid crystal diaphragm, an image sensor, a light distribution light source, and a belt transmission mechanism; a load-bearing plate is laid on the base frame, and the liquid crystal diaphragm is tightly attached to the load-bearing plate, an image sensor that can move in its length direction is provided above the liquid crystal diaphragm, and a light distribution light source is provided next to the image sensor, the image sensor is fixed to the bottom of the moving beam of the belt transmission mechanism, and the belt transmission mechanism is installed on both sides of the base frame.

[0005] Furthermore, the liquid crystal film comprises an upper substrate, a bistable cholesteric liquid crystal and a lower substrate which are arranged in sequence from top to bottom, and the upper substrate and the lower substrate may be polyester films PET.

[0006] Furthermore, electrodes made of copper foil are respectively provided at two ends of the bistable cholesteric liquid crystal, and the electrodes are connected to a voltage conversion circuit.

[0007] Furthermore, the image sensor is a large-format CIS image sensor.

[0008] Furthermore, the light distribution light source includes a grazing light source and a diffuse reflection light source, the wavelength band of the grazing light source is red light 600nm-670nm, and the diffuse reflection light source has the same length as the large-format CIS image sensor and is also installed at the bottom of the moving beam.

[0009] Furthermore, step shells for shielding the large-format CIS image sensor are provided on both sides of the base frame in the width direction, and side shells are provided on both sides of the base frame in the length direction.

[0010] Furthermore, the belt transmission mechanism includes a motor, which is located on one side of the base frame, and the motor output shaft is connected to the synchronous shaft a through a coupling. Transmission gears a are respectively provided at both ends of the synchronous shaft a, and each transmission gear a is connected to the corresponding transmission gear b through a belt, and the transmission gear b is located at both ends of the synchronous shaft b. The synchronous shaft a and the synchronous shaft b are respectively rotatably connected to the fixed blocks through bearings, and the fixed blocks are installed on the base frame; the two sides of the moving beam are connected to the corresponding belts through belt locking blocks, and the two ends of the bottom of the moving beam are connected to the corresponding guide rails through sliders, and the guide rails are symmetrically arranged on the base frame and located between the two belts; a grazing light source is installed on the inner side of each slider, and a magnetic scale is installed on the outer side.

[0011] Furthermore, the base frame is symmetrically mounted with infrared sensors in the length direction.

[0012] The present application also provides a working method of a planar footprint collection device, which specifically includes the following steps:

[0013] The person whose footprints are collected walks from one end of the liquid crystal membrane to the other end, leaving liquid crystal footprints and dust footprints on the surface of the liquid crystal membrane during the walking process;

[0014] When the surface of the liquid crystal film is under pressure, the liquid crystal molecules flip, and the light emitted by the light distribution light source shines on the flipping area. Only the light with the same wavelength as the liquid crystal thread distance is reflected, and the rest of the colors are absorbed, forming an indentation of the corresponding color;

[0015] The acquisition instructions are transmitted to a main control board installed inside the step housing, and the main control board controls the rotation of the motor;

[0016] When the motor rotates, it drives the synchronous shaft a and the transmission gear a to rotate together, and the transmission gear a drives the belt and then drives the transmission gear b and the synchronous shaft b to rotate, and the belt drives the large-format cis image sensor to move and scan above the liquid crystal diaphragm; the magnetic scale generates a synchronous trigger signal during the movement, and the trigger signal is processed by the main control board and sent to the large-format cis image sensor to synchronize the scanning frequency;

[0017] The infrared sensors are respectively fixed at the starting and ending positions of the scanning area. When the large-format cis image sensor moves forward, the grazing light source is turned on to show the dust footprint. When it approaches the end infrared sensor, the end infrared sensor signal jumps. After receiving the signal, the main control board controls the motor to stop rotating, and then the large-format cis image sensor completes the collection of dust footprints; when the large-format cis image sensor moves reversely, the diffuse reflection light source is turned on to show the liquid crystal footprint. When it approaches the starting infrared sensor, the starting infrared sensor signal jumps. After receiving the signal, the main control board controls the motor to stop rotating, and then the large-format cis image sensor completes the collection of liquid crystal footprints.

[0018] Furthermore, when the collection of dust footprints and liquid crystal footprints is completed, the main control board sends a high-voltage signal to the transformer circuit, and the transformer circuit is connected to the liquid crystal membrane through electrodes. After the liquid crystal membrane receives the high-voltage signal, the liquid crystal material molecules inside are rearranged, the flipped area is restored, the indentation footprint is cleared, and the next collection is waited for.

[0019] By adopting the above technical scheme, the present invention can achieve the following technical effects: the present application accurately converts the footprint pressure information into image information and truly restores the footprint image; the effective collection area can be constructed in a large format according to the needs, and the liquid crystal diaphragm used has no splicing breakpoints and completely retains the footprint information.

[0020] Through this application, the work intensity of police officers can be reduced and work efficiency can be improved. Footprints on the liquid crystal diaphragm can be automatically cleaned, which is easy to use. It can be used in laboratories to collect footprints in batches. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is an appearance diagram of a flat trip footprint collection device;

[0022] Figure 2 It is a schematic diagram of the internal structure of a planar footprint collection device;

[0023] Figure 3 for Figure 2 A partial structural enlargement of the

[0024] Figure 4 for Figure 2 A partial structural enlargement of the

[0025] Explanation of the serial numbers in the figure: 1. Step housing, 2. Liquid crystal diaphragm, 3. Side housing, 4. External power supply interface, 5. USB serial port control interface, 6. Power switch, 7. Large format CIS image sensor, 8. Transmission gear A, 9. Bearing, 10. Coupling, 11. Motor, 12. Belt locking block, 13. Grazing light source, 14. Belt, 15. Tank link, 16. Synchronous shaft A, 17. Guide rail, 18. Slider, 19. Infrared sensor, 20. Magnetic scale. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments: this example is used to further describe the present application.

[0027] Example 1

[0028] like Figure 1-4As shown, this embodiment provides a planar footprint collection device, which is a laboratory research equipment in the field of criminal investigation and is generally used in laboratories; specifically, it includes a planar footprint collection device, including a base frame, a load-bearing plate, a liquid crystal diaphragm, an image sensor, a light distribution light source, a belt transmission mechanism, and a main control board; a load-bearing plate is laid on the base frame, and a liquid crystal diaphragm is tightly attached to the load-bearing plate, an image sensor that can move in its length direction is provided above the liquid crystal diaphragm, and a light distribution light source is provided next to the image sensor, and the image sensor is fixed to the bottom of a moving beam of the belt transmission mechanism, and the belt transmission mechanism is installed on both sides of the base frame.

[0029] The liquid crystal membrane comprises an upper substrate, a bistable cholesteric liquid crystal and a lower substrate arranged in sequence from top to bottom, and the upper substrate and the lower substrate can be polyester film PET; when the foot steps on the liquid crystal membrane, the liquid crystal is squeezed and flipped by pressure, forming an indentation of the corresponding color. Electrodes made of copper foil are respectively provided at both ends of the bistable cholesteric liquid crystal, and the electrodes are connected to a transformer circuit, which can adjust the voltage difference applied to the electrodes at both ends. When the voltage reaches the threshold value of liquid crystal flipping, a path is formed inside the liquid crystal, and the flipped liquid crystal will be restored, achieving the purpose of clearing the indentation.

[0030] The image sensor is a large-format cis image sensor, which has no distortion in image acquisition and can accurately acquire image data. The cis image sensor is a linear array scanning imaging structure, which is driven by a stable belt transmission mechanism to perform linear scanning at a fixed focal length position above the liquid crystal film, and finally completes image acquisition. The acquired image will be displayed on the host computer.

[0031] The light distribution light source includes a grazing light source and a diffuse reflection light source. According to the polarization characteristics of the liquid crystal material, the wavelength band of the grazing light source is preferably red light 600nm-670nm, which can be an LED light source for illumination to reduce the influence of interference information on the collection results. The grazing angle is adjustable to display the dust footprint information on the surface of the liquid crystal membrane. The length of the diffuse reflection light source is the same as that of the large-format CIS image sensor and is also installed at the bottom of the moving beam. The diffuse reflection light sources are arranged linearly to ensure the uniformity of the illumination of the linear scanning image.

[0032] The belt transmission mechanism ensures the smooth operation of the large-format cis image sensor and the unchanged focal length of the large-format acquisition. Specifically, it includes a motor, which is located on one side of the base frame. The motor output shaft is connected to the synchronous shaft a through a coupling. The two ends of the synchronous shaft a are respectively provided with transmission gears a. Each transmission gear a is connected to the corresponding transmission gear b through a belt. The transmission gear b is located at both ends of the synchronous shaft b. The synchronous shaft a and the synchronous shaft b are respectively rotatably connected to the fixed block through bearings. The fixed block is installed on the base frame; the two sides of the moving beam are connected to the corresponding belt through a belt locking block, and the two ends of the bottom of the moving beam are connected to the corresponding guide rail through a slider. The guide rail is symmetrically arranged on the base frame and located between the two belts. In order to maintain the stability of the belt transmission, a limit roller is installed under the belt; a grazing light source is installed on the inner side of each slider, and a magnetic scale is installed on the outer side to accurately measure the displacement distance of the large-format cis image sensor and trigger the image synchronization acquisition signal. In order to ensure accurate scanning movement, the two sides of the large-format cis image sensor are respectively connected to the corresponding sliders.

[0033] The base frame is made of a metal frame to ensure the flatness and stability of the equipment. Step housings are provided on both sides of the width direction of the base frame. The large-format CIS image sensor is hidden in the step housing when in standby mode, and the entire liquid crystal film area is scanned when in operation. Side housings are provided on both sides of the length direction of the base frame, and a tank connection fixed to the base frame is provided inside one of the side housings to accommodate the power cords of the large-format CIS image sensor and the magnetic scale. An external power supply interface, a USB serial port control interface, and a power switch are provided on the side of one of the step housings; infrared sensors are symmetrically installed on the base frame in the length direction to detect whether the large-format CIS image sensor touches both ends during movement.

[0034] The load-bearing plate is strong enough for several people to walk on it without deformation. The surface of the load-bearing plate is mirror-flat and can be a glass plate with a liquid crystal film attached to its surface.

[0035] The acquisition device is connected to the host computer through the camera link image transmission interface and the USB serial port control interface, and the matching acquisition software is used to enable the user to control it on the host computer side.

[0036] The present application also provides a working method of a planar footprint collection device, which specifically includes the following steps:

[0037] The person whose footprints are collected walks from one end of the liquid crystal membrane to the other end, leaving liquid crystal footprints and dust footprints on the surface of the liquid crystal membrane during the walking process;

[0038] When the surface of the liquid crystal film is under pressure, the liquid crystal molecules flip, and the light emitted by the light distribution light source shines on the flipping area. Only the light with the same wavelength as the liquid crystal thread distance is reflected, and the rest of the colors are absorbed, forming an indentation of the corresponding color;

[0039] At this time, the user clicks the acquisition button on the upper computer screen, and the acquisition instruction is transmitted to the main control board installed inside the step housing, and the main control board controls the motor to rotate;

[0040] When the motor rotates, it drives the synchronous shaft a and the transmission gear a to rotate together, and the transmission gear a drives the belt and then drives the transmission gear b and the synchronous shaft b to rotate, and the belt drives the large-format cis image sensor to move and scan above the liquid crystal diaphragm; the magnetic scale generates a synchronous trigger signal during the movement, and the trigger signal is processed by the main control board and sent to the large-format cis image sensor to synchronize the scanning frequency;

[0041] The infrared sensors are fixed at the beginning and end positions of the scanning area. When the large-format cis image sensor moves forward, the grazing light source is turned on to show the dust footprint. When it is close to the end infrared sensor, the end infrared sensor signal jumps. After receiving the signal, the main control board controls the motor to stop rotating, and then the large-format cis image sensor completes the collection of dust footprints. When the large-format cis image sensor moves in the opposite direction, the diffuse reflection light source is turned on to show the liquid crystal footprint. When it is close to the starting infrared sensor, the starting infrared sensor signal jumps. After receiving the signal, the main control board controls the motor to stop rotating, and then the large-format cis image sensor completes the collection of liquid crystal footprints. The final footprint image is uploaded to the host computer through the camera link image transmission interface. After the host computer obtains the footprint image, it can perform subsequent analysis.

[0042] When the collection of dust footprints and liquid crystal footprints is completed, the main control board sends a high-voltage signal to the transformer circuit, and the transformer circuit is connected to the liquid crystal diaphragm through electrodes. After the liquid crystal diaphragm receives the high-voltage signal, the liquid crystal material molecules inside are rearranged, the flipped area is restored, the indentation footprint is cleared, and the next collection is waited for.

[0043] The preferred model of the main control board is STM32F103C8T6, which is respectively connected to the serial port chip FT232, the motor controller, the transformer circuit, the LED constant current drive module (PT4121), two infrared sensors, the magnetic scale, and the large-format cis image sensor. The large-format cis image sensor is also connected to the host computer through the camera link to realize image transmission; the main control board is powered by 3.3v through the power supply module of the MIC5219 chip, and the large-format cis image sensor is powered by 5v through the power supply module of the XL4005E1 chip.

[0044] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A planar footprint collection device, characterized in that: It includes a base frame, a load-bearing plate, a liquid crystal film, an image sensor, a light distribution light source, and a belt transmission mechanism; the load-bearing plate is laid on the base frame, the liquid crystal film is tightly attached to the load-bearing plate, an image sensor that can move in the length direction of the liquid crystal film is arranged above the liquid crystal film, a light distribution light source is arranged next to the image sensor, the image sensor is fixed to the bottom of the moving beam of the belt transmission mechanism, and the belt transmission mechanism is installed on both sides of the base frame; The light distribution light source includes a grazing light source and a diffuse reflection light source. The wavelength of the grazing light source is 600nm-670nm for red light. The diffuse reflection light source has the same length as the large-format cis image sensor and is also installed at the bottom of the moving beam. The belt transmission mechanism includes a motor, which is located on one side of the base frame. The motor output shaft is connected to the synchronous shaft a through a coupling. Transmission gears a are respectively provided at both ends of the synchronous shaft a. Each transmission gear a is connected to the corresponding transmission gear b through a belt. The transmission gear b is located at both ends of the synchronous shaft b. The synchronous shaft a and the synchronous shaft b are respectively rotatably connected to fixed blocks through bearings, and the fixed blocks are installed on the base frame; the two sides of the moving beam are connected to the corresponding belts through belt locking blocks, and the two ends of the bottom of the moving beam are connected to the corresponding guide rails through sliders, and the guide rails are symmetrically arranged on the base frame and located between the two belts; a grazing light source is installed on the inner side of each slider, and a magnetic scale is installed on the outer side.

2. A planar footprint collection device according to claim 1, characterized in that: The liquid crystal film comprises an upper substrate, a bistable cholesteric liquid crystal and a lower substrate which are arranged in sequence from top to bottom.

3. A planar footprint collection device according to claim 2, characterized in that: Electrodes made of copper foil are respectively arranged at two ends of the bistable cholesteric liquid crystal, and the electrodes are connected to a voltage conversion circuit.

4. The device for collecting footprints on a plane according to claim 1, characterized in that: The image sensor is a large-format cis image sensor.

5. The device for collecting footprints on a plane according to claim 1, characterized in that: Step shells for shielding large-format cis image sensors are arranged on both sides of the base frame in the width direction, and side shells are arranged on both sides of the base frame in the length direction.

6. The device for collecting footprints on a plane according to claim 1, characterized in that: The base frame is symmetrically equipped with infrared sensors in the length direction.

7. A method for using a planar footprint collection device, characterized in that: The specific steps include: The person whose footprints are collected walks from one end of the liquid crystal membrane to the other end, leaving liquid crystal footprints and dust footprints on the surface of the liquid crystal membrane during the walking process; When the surface of the liquid crystal film is under pressure, the liquid crystal molecules flip, and the light from the light distribution light source shines on the flipping area. Only the light with the same wavelength as the liquid crystal thread distance is reflected, and the rest of the colors are absorbed, forming an indentation footprint of the corresponding color. The acquisition instructions are transmitted to a main control board installed inside the step housing, and the main control board controls the rotation of the motor; When the motor rotates, it drives the synchronous shaft a and the transmission gear a to rotate together, and the transmission gear a drives the belt and then drives the transmission gear b and the synchronous shaft b to rotate, and the belt drives the large-format cis image sensor to move and scan above the liquid crystal diaphragm; the magnetic scale generates a synchronous trigger signal during the movement, and the trigger signal is processed by the main control board and sent to the large-format cis image sensor to synchronize the scanning frequency; The infrared sensors are respectively fixed at the starting and ending positions of the scanning area. When the large-format cis image sensor moves forward, the grazing light source is turned on to show the dust footprint. When it approaches the end infrared sensor, the end infrared sensor signal jumps. After receiving the signal, the main control board controls the motor to stop rotating, and then the large-format cis image sensor completes the collection of dust footprints; when the large-format cis image sensor moves reversely, the diffuse reflection light source is turned on to show the liquid crystal footprint. When it approaches the starting infrared sensor, the starting infrared sensor signal jumps. After receiving the signal, the main control board controls the motor to stop rotating, and then the large-format cis image sensor completes the collection of liquid crystal footprints.

8. The method for using the planar footprint collection device according to claim 7, characterized in that: When the collection of dust footprints and liquid crystal footprints is completed, the main control board sends a high-voltage signal to the transformer circuit, and the transformer circuit is connected to the liquid crystal diaphragm through electrodes. After the liquid crystal diaphragm receives the high-voltage signal, the liquid crystal material molecules inside are rearranged, the flipped area is restored, the indentation footprint is cleared, and the next collection is waited for.

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