Combined laser handprint searching and photographing instrument

Abstract

The utility model provides a combined laser handprint search and photographing instrument, through single person operation, not only realizes independent search handprint material evidence, can realize handprint photographing again, and can improve the evenness while increasing unit area light intensity, and effectively eliminate the shadow effect of the surface uneven object caused by the inclined irradiation, including laser, beam splitter and photographic equipment, the beam splitter includes the box, is equipped with the light inlet hole, the light outlet hole and the imaging hole on the box, the optical axis of light inlet hole and the optical axis of light outlet hole are perpendicular and intersect, the light outlet hole and the imaging hole are coaxially arranged, the laser can be detachably assembled on the box, and the laser emitted by the laser passes through the light inlet hole and enters the box, the box is detachably assembled with the beam splitter between the imaging hole and the light outlet hole, then the laser in the box is reflected to the handprint on the bearing object below the light outlet hole through the beam splitter, and the fluorescence emitted by the handprint after laser irradiation is imaged through the light outlet hole, the beam splitter, the imaging hole and the photographic equipment in turn.

Description

Technical Field

[0001] This utility model relates to the field of forensic science technology, specifically a combined laser fingerprint search and capture device. Background Technology

[0002] In crime scene investigation, different wavelengths of light, such as blue, green, and red light, can be used to search for various untreated traces and physical evidence, as well as traces and physical evidence treated with reagents or fluorescent powders, and then photographically preserved. These traces and physical evidences include fingerprints, biological evidence, and trace evidence, with fingerprints being a typical example. Compared to other light sources, lasers have advantages such as good monochromaticity, strong directionality, and high optical power. They can not only more effectively excite the fluorescent substances inherent in fingerprint evidence itself, but also more effectively excite the fluorescent substances produced by reagent treatment and fluorescent powder particles, making it easier for crime scene investigators to find and photograph these pieces of evidence. Therefore, lasers are a powerful tool for crime scene investigation.

[0003] When on-site investigators use lasers to search for fingerprint evidence, they must wear appropriate protective goggles. For example, when using a blue laser, they must wear blue light blocking goggles, and when using a green laser, they must wear green light blocking goggles. Wearing goggles can block specific wavelengths of laser light from entering the eyes while allowing longer wavelengths of fluorescence to pass through. This allows them to clearly see whether there is any fluorescent material in the area illuminated by the laser. Once fluorescent material is found, for example, a fingerprint on a white wall discovered using a blue laser, if analysis suggests it may be related to the facts of the case, it needs to be photographed for preservation. However, photographic preservation is difficult for a single person to operate and usually requires two people working together. One person holds the laser and illuminates the fingerprint, while the other uses a professional camera with a color filter to take the picture. This is time-consuming, labor-intensive, and has low work efficiency. Furthermore, for some fingerprint evidence, if the content of fluorescent material is extremely low, the light intensity per unit area illuminating the fingerprint evidence becomes very important. Therefore, only by reaching a certain light intensity per unit area can the fluorescent material be effectively activated, thereby effectively revealing these traces of evidence. Generally, lasers used for evidence search can emit uniform laser beams with a certain divergence angle. The intensity per unit area of ​​the laser beam illuminating the surface of the object bearing the fingerprint is closely related to three factors: the laser's optical power, the distance between the light source and the object, and the angle at which the light source illuminates the object. However, the following problems still exist: (1) The maximum optical power of a laser is fixed, and the light intensity per unit area cannot be increased by infinitely increasing the maximum optical power of the laser. (2) In order to record the true form of the fingerprint evidence and avoid image distortion when taking pictures, the camera must be perpendicular to the plane where the fingerprint evidence is located. This requires that the laser output port cannot be too close to the fingerprint evidence and must be tilted at a certain angle. Otherwise, the laser will block the trace evidence and make it impossible to take pictures. However, under the premise that the laser output port is the same distance from the fingerprint evidence, the light intensity per unit area of ​​tilted illumination is definitely less than the light intensity per unit area of ​​vertical illumination, so it is impossible to achieve the purpose of effectively displaying trace evidence by increasing the light intensity per unit area. (3) When the laser is irradiated at a certain angle, the light intensity of the spot on the object will be uneven. That is to say, the closer the part is to the laser, the stronger the light intensity per unit area, which will cause the fingerprint fluorescence in that part to be stronger; while the farther the part is from the laser, the weaker the light intensity per unit area, which will also cause the fingerprint fluorescence in that part to be weaker; more seriously, if the surface of the trace evidence is uneven, the tilted irradiation will form a shadow in a local area, which will cause the fingerprint fluorescence in that area to be unable to be effectively excited.

[0004] Therefore, it is necessary to provide a combined laser fingerprint scanner to solve the above-mentioned technical problems. Utility Model Content

[0005] To address the aforementioned problems, this utility model provides a combined laser fingerprint search and capture device, which can be operated by a single person. It can not only independently search for fingerprint evidence but also capture fingerprint images. Furthermore, it can increase the uniformity of light intensity per unit area while effectively eliminating the shadow effect on uneven surfaces caused by tilted illumination.

[0006] The technical solution of this utility model is as follows: a combined laser fingerprint scanner, including a laser, a beam splitter, and a photographic device; the beam splitter includes a housing, on which are provided an entrance hole, an exit hole, and an imaging hole. The optical axis of the entrance hole intersects perpendicularly with the optical axis of the exit hole, and the exit hole and the imaging hole are coaxially arranged. The laser is detachably mounted on the housing, allowing the laser emitted by the laser to pass through the entrance hole and enter the housing. A beam splitter is detachably mounted in the housing between the imaging hole and the exit hole. The laser entering the housing is reflected by the beam splitter onto a fingerprint on a carrier object located directly below the exit hole. The fluorescence emitted by the fingerprint after being irradiated by the laser passes sequentially through the exit hole, the beam splitter, the imaging hole, and the photographic device to form an image.

[0007] Furthermore, the light inlet is located on the side of the housing, and an extension is provided on the outer periphery of the housing located at the light inlet. The extension on the outer periphery forms an open light source cavity. The laser is detachably assembled into the light source cavity, and the laser's emission port faces the light inlet. Furthermore, the laser is used to output laser beams of different wavelengths, including blue or green light; Furthermore, the light-emitting aperture is located at the bottom of the housing, the imaging aperture is located at the top of the housing, and the beam splitter is a dichroic beam splitter; Furthermore, the beam splitter faces the entrance aperture and is set at a 45° angle to the horizontal direction; and the beam splitter is located at the intersection of the optical axis of the entrance aperture and the optical axis of the exit aperture, so as to reflect the horizontal laser light incident through the entrance aperture downward and pass through the exit aperture to vertically irradiate the carrier object located directly below the exit aperture; Furthermore, the housing has a slot, through which the beam splitter is inserted into the housing; the fluorescence is transmitted through the beam splitter to the imaging aperture, and the wavelength of the fluorescence is longer than the wavelength of the laser emitted by the laser. Furthermore, the photographic device includes a camera located at the end of the imaging optical path formed by the beam splitter and the imaging aperture, and a color filter is mounted on the imaging optical path between the camera and the beam splitter via a tray; Furthermore, the tray is disposed at the imaging aperture, the photographic device is adapted and connected to the beam splitter, and the camera is positioned directly facing the imaging aperture; Furthermore, an imager is provided between the photographic device and the beam splitter. The imager includes a housing and an imaging objective, a first reflector, and a second reflector disposed within the housing. The housing has a photographic aperture, and the tray is disposed at the photographic aperture. The photographic device is adapted to and connected to the imager, with the camera facing the photographic aperture and the camera lens located at the focal point of the imaging objective. The first reflector and the second reflector are arranged parallel to each other. The imager is adapted to and connected to the beam splitter, with the imaging objective positioned directly above the imaging aperture to receive fluorescence passing through the imaging aperture. The light passing through the imaging objective then passes sequentially through the first reflector, the second reflector, and a color filter before reaching the camera to form an image.

[0008] The beneficial effects of this utility model are that, through its modular design, the laser can be detached to independently search for fingerprint evidence, or it can be installed to photograph fingerprints. Furthermore, the coaxial alignment of laser illumination and fluorescence imaging increases the light intensity per unit area of ​​the fingerprint while improving uniformity. It also effectively eliminates the shadowing effect caused by tilted illumination on uneven surfaces. Not only can it be operated by a single person, but it also eliminates the need for other professional cameras or equipment, effectively saving manpower and resources. This makes the discovery and photographic preservation of trace evidence at crime scenes more convenient, and it effectively improves the quality and rate of trace evidence collection, which is of great significance for criminal investigation. Attached Figure Description

[0009] Figure 1 This is a cross-sectional structural diagram of Embodiment 1 of this utility model; Figure 2 This is a schematic diagram of the lighting optical path according to Embodiment 1 of this utility model; Figure 3 This is a schematic diagram of the imaging optical path of Embodiment 1 of this utility model; Figure 4 This is a cross-sectional structural diagram of Embodiment 2 of this utility model; Figure 5 This is a schematic diagram of the lighting optical path according to Embodiment 2 of this utility model; Figure 6 This is a schematic diagram of the imaging optical path of Embodiment 2 of this utility model; Figure 7 The image shows a green fluorescent handprint on the back of a tile, illuminated at an angle by a blue laser. Figure 8 This utility model uses a blue laser to vertically illuminate the back of a tile, resulting in a green fluorescent photograph of a handprint.

[0010] Figures 1-6 In Chinese: 1. Laser; 2. Beam splitter; 3. Housing; 4. Camera; 5. Carrier; 6. Handprint; 7. Box; 8. Light entrance aperture; 9. Light exit aperture; 10. Imaging aperture; 11. Light source cavity; 12. Beam splitter; 13. Color filter; 14. Slot; 15. Tray; 16. Imaging objective lens; 17. First mirror; 18. Second mirror; 19. Camera aperture; 20. Photographic equipment; 21. Imager Detailed Implementation The technical solutions and beneficial effects of the embodiments of this utility model will be described in detail below with reference to the accompanying drawings. The described embodiments are merely some embodiments of this utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the protection scope of this utility model.

[0011] Example 1 like Figure 1 As shown, this utility model discloses a combined laser fingerprint scanner, comprising a laser 1, a beam splitter 2, and a photographic device 20. The laser 1 outputs a uniform laser beam with different wavelengths, including blue or green light, and a certain divergence angle. This is because different wavelengths of light sources are selected according to different fingerprints, objects, and fluorescent reagents. Blue and green light are the most commonly used, and other wavelengths of laser light may be used in special cases. The beam splitter 2 includes a housing 7, on which a light inlet 8, a light outlet 9, and an imaging aperture 10 are provided. The optical axis of the light inlet 8 is aligned with that of the light outlet 9. The optical axes of the 9 are perpendicularly intersecting, and the light output hole 9 and the imaging hole 10 are coaxially arranged. The laser 1 is detachably mounted on the housing 7, and the laser emitted by the laser 1 passes through the light entrance hole 8 and enters the housing 7. A beam splitter 12 located between the imaging hole 10 and the light output hole 9 is detachably mounted in the housing 7. The laser entering the housing 7 is reflected by the beam splitter 12 to the handprint 6 on the carrier 5 located directly below the light output hole 9. The fluorescence emitted by the handprint 6 after being irradiated by the laser passes through the light output hole 9, the beam splitter 12, the imaging hole 10, and the photographic device 20 in sequence to form an image.

[0012] The light inlet 8 is located on the side of the housing 7. The housing 7 located at the light inlet 8 has an extension on its outer periphery, and the extension on the outer periphery forms an open light source cavity 11. The laser 1 is detachably assembled into the light source cavity 11, and the emission port of the laser 1 is directly facing the light inlet 8.

[0013] The light exit aperture 9 is located at the bottom of the housing 7, the imaging aperture 10 is located at the top of the housing 7, and the beam splitter 12 is a dichroic beam splitter 12. The beam splitter 12 faces the light entrance aperture 8 and is set at a 45° angle to the horizontal direction. The beam splitter 12 is located at the intersection of the optical axis of the light entrance aperture 8 and the optical axis of the light exit aperture 9, so as to reflect the horizontal laser light incident through the light entrance aperture 8 downward and pass through the light exit aperture 9 to vertically illuminate the carrier 5 located directly below the light exit aperture 9.

[0014] The housing 7 has a slot 14, through which the beam splitter 12 is inserted into the housing 7. This means that different specifications of beam splitters 12 can be replaced by inserting and removing them through the slot 14 to accommodate different wavelengths of laser light. This allows for the reflection of most of the laser light from the laser 1 while transmitting most of the longer-wavelength fluorescence from the handprint 6. The fluorescence is transmitted through the beam splitter 12 to the imaging aperture 10, and the wavelength of the fluorescence is longer than the wavelength of the laser light emitted by the laser 1.

[0015] The photographic device 20 includes a camera 4, which is located at the end of the imaging optical path formed by the beam splitter 12 and the imaging aperture 10. A color filter 13 is mounted on the imaging optical path between the camera 4 and the beam splitter 12 via a tray 15. The tray 15 is located at the imaging aperture 10. The photographic device 20 is adapted to the beam splitter 2, and the camera 4 is positioned directly opposite the imaging aperture 10. The tray 15 can hold the color filter 13 for easy replacement. The selected color filter 13 can filter out laser light and other interfering light while allowing the fluorescence of the handprint 6 to pass through.

[0016] The working principle of Embodiment 1 of this utility model is as follows: Laser 1 can be used alone for fingerprint search. When a fingerprint is detected, laser 1 is inserted into the light source cavity 11 of beam splitter 2 to photograph and fix the fingerprint, such as... Figure 2 and Figure 3 As shown, the laser emitted by laser 1 enters the entrance aperture 8, is reflected by the dichroic beam splitter 12, and exits vertically downwards from the exit aperture 9, illuminating the carrier object 5 and the fingerprint 6 perpendicularly. The fluorescent material in the fingerprint 6 emits fluorescence under the illumination of a specific wavelength of laser light. This fluorescence passes through the exit aperture 9, then through the dichroic beam splitter 12, and finally through the color filter 13 at the imaging aperture 10, ultimately allowing the fluorescence of the fingerprint 6 to enter the camera 4 for imaging. For different colors of laser light sources, a suitable dichroic beam splitter 12 is selected to achieve the goal of not only reflecting most of the laser light but also allowing most of the fluorescence emitted by the fingerprint 6 to pass through. For different wavelengths of fluorescence and different wavelengths of interfering light, appropriate filters can be selected accordingly to achieve the goal of not only allowing the fingerprint fluorescence to pass through but also blocking interfering light, thus achieving the beneficial effect of clearly displaying the fingerprint lines.

[0017] Example 2 The difference between Embodiment 2 and Embodiment 1 is that Embodiment 1 only uses the photographic device 20 and does not include the imager 21; while Embodiment 2, in addition to the photographic device 20, also includes the imager 21, so as to achieve the purpose of keeping the optical magnification (the size ratio of the image to the object) constant as the shooting distance changes. like Figure 4As shown, specifically, an imager 21 is provided between the photographic device 20 and the beam splitter 2. The imager 21 includes a housing 3 and an imaging objective lens 16, a first reflector 17, and a second reflector 18 disposed within the housing 3. The housing 3 is provided with a photographic aperture 19, and a tray 15 is disposed at the photographic aperture 19. The photographic device 20 is adapted to and connected to the imager 21, and the camera 4 is positioned directly opposite the photographic aperture 19. The lens of the camera 4 (not shown in the figure) is located at the focal point of the imaging objective lens 16. The first reflector 17 and the second reflector 18 are arranged in parallel. The imager 21 is adapted to and connected to the beam splitter 3, and the imaging objective lens 16 is positioned directly above the imaging aperture 10 to receive the fluorescence passing through the imaging aperture 10. The light passing through the imaging objective lens 16 then passes sequentially through the first reflector 17, the second reflector 18, and the color filter 13 before reaching the camera 4 to form an image.

[0018] The working principle of Embodiment 2 of this utility model is as follows: Laser 1 can be used alone for fingerprint search. Once a fingerprint is detected, laser 1 is inserted into beam splitter 2 to photograph and fix the fingerprint, such as... Figure 5 and Figure 6 As shown, the laser emitted by laser 1 enters the entrance aperture 8, is reflected by the dichroic beam splitter 12, and exits vertically downwards from the exit aperture 9, illuminating the carrier object 5 and the fingerprint 6. The fluorescent material in the fingerprint 6 emits fluorescence under the illumination of the laser at a specific wavelength. The fluorescence passes through the exit aperture 9, then through the dichroic beam splitter 12, then through the imaging aperture 10, and then into the imaging objective lens 16. After two reflections by the first reflector 17 and the second reflector 18, it is finally filtered by the color filter 13 at the imaging aperture 19, allowing the fluorescence of the fingerprint 6 to enter the camera 4 for imaging. For different colors of laser light sources, a suitable dichroic beam splitter 12 is selected to achieve the goal of not only reflecting most of the laser light but also allowing most of the fluorescence emitted by the fingerprint 6 to pass through. For different wavelengths of fluorescence and different wavelengths of interfering light, appropriate filters can be selected accordingly to achieve the goal of not only allowing the fingerprint fluorescence to pass through but also blocking interfering light, thus achieving the beneficial effect of clearly displaying the fingerprint lines. By using the imager 21, the lens of the camera 4 is positioned at the focal point of the imaging objective lens 16, so that the size of the handprint image does not change with the shooting distance (the distance between the light outlet 9 and the carrier object 5).

[0019] In both Embodiment 1 and Embodiment 2 of this utility model, the same illumination optical path is used. Regardless of whether Embodiment 1 or Embodiment 2 is used, the camera can be disassembled according to actual conditions, a suitable color filter can be placed on the tray, and then the camera can be reassembled to take pictures of the image after the color filter has been applied. Therefore, any embodiment can be selected for verification and explanation. In this utility model embodiment, the technical solution of Embodiment 2 is selected for vertical illumination to specifically verify that it can effectively eliminate the shadow effect on the surface of the object being supported by uneven surfaces. Figure 7The existing method involves using a blue laser to obliquely irradiate the back of a tile (i.e., the substrate) after it has been treated with a fluorescent reagent. As can be seen, the uneven texture of the tile's back creates the shadowed strip indicated by the white arrow in the image, resulting in the loss of the fingerprint lines. Figure 8 This invention uses a blue laser inserted into the light source cavity of a beam splitter to vertically illuminate the back of a ceramic tile (i.e., the substrate) after it has been treated with a fluorescent reagent, thus exciting a photograph of a handprint with green fluorescence. The shadow bands are visible, and the handprint lines are continuous and without gaps. Furthermore, in Embodiment Two, the imaging objective lens 16, the first reflector 17, and the second reflector 18, all located within the housing 3, ensure that the optical magnification (the ratio of image to object size) remains constant regardless of the photographing distance. This allows for on-site investigation personnel to photograph trace evidence at different distances while maintaining a consistent image size on the camera. This solves the problem of having to recalibrate the electronic ruler when the photographing distance changes, as was previously the case when using an electronic ruler instead of a physical ruler. This eliminates the need for electronic ruler calibration and prevents contamination or damage to potential evidence on the substrate, making on-site trace evidence photography more convenient, efficient, and safe.

[0020] Figure 2 and Figure 5 The arrows in the diagram indicate the direction of the laser beam; Figure 3 and Figure 6 The arrows in the diagram indicate the direction of the imaging rays.

[0021] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. For example, by modifying Embodiment 2 and placing the color filter 13 at any position on the imaging optical path between the imaging aperture 10 and the photographic aperture 19, the same effect as this invention can be achieved. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this invention is defined by the appended claims rather than the foregoing description, and thus all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0022] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A combined laser fingerprint scanner, characterized in that: The system includes a laser, a beam splitter, and a photographic device. The beam splitter includes a housing with an entrance aperture, an exit aperture, and an imaging aperture. The optical axis of the entrance aperture intersects perpendicularly with the optical axis of the exit aperture. The exit aperture and the imaging aperture are coaxially arranged. The laser is detachably mounted on the housing, allowing the laser emitted by the laser to pass through the entrance aperture into the housing. A beam splitter is detachably mounted inside the housing, located between the imaging aperture and the exit aperture. The laser entering the housing is reflected by the beam splitter onto a handprint on a support object located directly below the exit aperture. The fluorescence emitted by the handprint after being irradiated by the laser passes sequentially through the exit aperture, the beam splitter, the imaging aperture, and the photographic device to form an image.

2. The combined laser fingerprint scanner according to claim 1, characterized in that: The light inlet is located on the side of the housing. An extension is provided on the outer periphery of the housing located at the light inlet, and an open light source cavity is formed by the extension on the outer periphery. The laser is detachably assembled into the light source cavity, and the emission port of the laser is directly facing the light inlet.

3. The combined laser fingerprint scanner according to claim 1, characterized in that: The laser is used to output laser beams of different wavelengths, including blue or green light.

4. The combined laser fingerprint scanner according to claim 1, characterized in that: The light-emitting aperture is located at the bottom of the housing, the imaging aperture is located at the top of the housing, and the beam splitter is a dichroic beam splitter.

5. A combined laser fingerprint scanner according to claim 1, characterized in that: The beam splitter faces the entrance aperture and is set at a 45° angle to the horizontal direction; and the beam splitter is located at the intersection of the optical axis of the entrance aperture and the optical axis of the exit aperture, so as to reflect the horizontal laser light incident through the entrance aperture downward and pass through the exit aperture to vertically irradiate the carrier object located directly below the exit aperture.

6. The combined laser fingerprint scanner according to claim 1, characterized in that: The housing has a slot, through which the beam splitter is inserted into the housing; the fluorescence is transmitted through the beam splitter to the imaging aperture, and the wavelength of the fluorescence is longer than the wavelength of the laser emitted by the laser.

7. A combined laser fingerprint scanner according to any one of claims 1 to 6, characterized in that: The photographic device includes a camera located at the end of the imaging optical path formed by the beam splitter and the imaging aperture, and a color filter is mounted on the imaging optical path between the camera and the beam splitter via a tray.

8. A combined laser fingerprint scanner according to claim 7, characterized in that: The tray is positioned at the imaging aperture, and the photographic device is adapted and connected to the beam splitter, such that the camera is positioned directly facing the imaging aperture.

9. A combined laser fingerprint scanner according to claim 7, characterized in that: An imager is disposed between the photographic device and the beam splitter. The imager includes a housing and an imaging objective, a first reflector, and a second reflector disposed within the housing. The housing has a photographic aperture. The tray is disposed at the photographic aperture. The photographic device is adapted to and connected to the imager, with the camera facing the photographic aperture and the lens of the camera located at the focal point of the imaging objective. The first reflector and the second reflector are arranged in parallel. The imager is adapted to and connected to the beam splitter, with the imaging objective positioned directly above the imaging aperture to receive fluorescence passing through the imaging aperture. The light rays passing through the imaging objective lens then pass sequentially through the first mirror, the second mirror, and the color filter before reaching the camera, where they are used to form an image.

Images