Portable fingerprint camera device with horizontal multi-stage reflection of beamsplitter

Abstract

The application provides a portable fingerprint photographing device with horizontal multi-stage reflection of a beamsplitter and reflection imaging, which can further increase the optical path of an imaging light path and reduce the volume, obtain a higher quality fingerprint image, and has better portability and ease of use; a light source assembly and a beamsplitter are arranged in a box body, the light source assembly comprises a light source, a photographing hole and a sample hole are formed in the box body, light emitted by the light source is transmitted through the beamsplitter to form an illumination light path, the illumination light path further comprises a first reflector, the light transmitted through the beamsplitter is reflected to the sample hole at the end of the illumination light path through the first reflector; the light reflected by a fingerprint object located at the sample hole after being irradiated is reflected through the first reflector and the beamsplitter to form an imaging light path, and the imaging light path passes through a second reflector and a third reflector arranged on the imaging light path to be reflected to the photographing hole at the end of the imaging light path, and the light path between the light source and the first reflector and the light path between the first reflector and the third reflector are both located in a horizontal direction.

Description

Technical Field

[0001] This invention relates to the field of forensic science technology, specifically to a portable fingerprint camera with horizontal multi-level reflection beam splitter reflection imaging. Background Technology

[0002] Photography is a crucial step in the examination of fingerprints and other trace evidence. If visible fingerprints are found at the scene or on the sample, or if fingerprints have undergone physical or chemical treatment, they should be photographed and recorded as soon as possible to prevent fading or accidental destruction. Photochromism involves selecting a white light source or other wavelengths and adjusting the angle and direction of the illumination to control the brightness distribution of reflected light from the sample. This enhances the contrast between the fingerprint ridges and the background pattern, while reducing or eliminating interference from the background pattern. Various photochromic methods exist. For fingerprints adhering to smooth, non-porous, or semi-porous planar surfaces, bright-field photography, specifically directional photography, is most commonly used. In reflective photography, the most commonly used dark-field photography is dark-view photography. However, the types and conditions of fingerprints and their objects vary in different locations, requiring different light distribution methods to effectively reveal fingerprint ridges and details. However, different light distribution devices often have limited applications. For example, directional reflector devices commonly used in fingerprint photography can only perform bright-field directional reflective photography; dark-view light distribution devices can only perform dark-view photography. Furthermore, existing light distribution devices and their associated light-shielding components are large, making them difficult for single-person operation and challenging to use during complex and variable environmental conditions such as space and lighting during on-site investigations, thus failing to achieve good results. For bright-field fingerprint images obtained using directional reflective light distribution devices, when the camera lens is far from the fingerprint object (i.e., the optical path of the imaging light is long), the contrast between the fingerprint ridges and the object background is greater, background pattern interference is less, and the fingerprint display quality is better. However, this requires a relatively tall device, making miniaturization difficult.

[0003] To address the aforementioned issues, existing patent number ZL202021197355.1, titled "Portable Fingerprint Camera with Reflective Imaging," integrates a light distribution device into a miniaturized portable device. Compared to traditional devices, its reduced size and height enable miniaturization. However, there is still room for improvement in the following aspects: increasing the optical path of the imaging optical path to obtain a higher quality fingerprint image, while further reducing the size, especially the height, to achieve better portability and ease of use. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a portable fingerprint imaging device with horizontal multi-level reflection beam splitter, which can further increase the optical path of the imaging optical path and reduce the volume, thereby obtaining higher quality fingerprint images, and has better portability and ease of use.

[0005] The technical solution is as follows: a portable fingerprint camera with horizontal multi-level reflection beam splitter imaging, comprising a housing, wherein a light source assembly and a beam splitter are provided inside the housing, the light source assembly includes a light source, and the housing has a photographic aperture and a sample aperture. The light emitted by the light source is transmitted through the beam splitter to form an illumination light path. The illumination light path further includes a first reflector, and the light transmitted through the beam splitter is reflected by the first reflector to the sample aperture at the end of the illumination light path. The light reflected by the fingerprint object located at the sample aperture after being illuminated is reflected by the first reflector and the beam splitter to form an imaging light path, and is reflected by a second reflector and a third reflector to the photographic aperture at the end of the imaging light path. The light path from the light source to the first reflector and the light path from the first reflector to the third reflector are both located in the horizontal direction.

[0006] Furthermore, the housing is also equipped with a condenser lens and an imaging objective lens. The condenser lens is disposed in the illumination optical path between the light source and the beam splitter, and the imaging objective lens is disposed in the imaging optical path between the beam splitter and the camera aperture.

[0007] Furthermore, the optical distance between the condenser lens and the light source is the same as the focal length of the condenser lens; the imaging objective lens is disposed on the imaging optical path between the beam splitter and the second reflecting mirror, the optical axis of the imaging objective lens and the optical axis of the condenser lens are both parallel to the bottom plane of the housing, and the two optical axes intersect perpendicularly; the beam splitter is disposed on the angle bisector of the right angle formed by the intersection of the two optical axes, and the beam splitter is perpendicular to the bottom plane of the housing;

[0008] Furthermore, the inspection hole is located at the bottom of the housing, the first reflector is located directly above the inspection hole, and the beam splitter is located to the horizontal side of the first reflector; the optical axis of the condenser is perpendicular to the central axis of the inspection hole; the first reflector is located at the intersection of the two axes and is perpendicular to the angle bisector of the right angle formed by the intersection of the two axes;

[0009] Furthermore, the second reflector is disposed on the imaging optical path between the imaging objective lens and the third reflector, and the second reflector is disposed parallel to the beam splitter; the camera aperture is disposed on the top of the housing directly above the third reflector, and the central axis of the camera aperture intersects perpendicularly with the optical axis of the imaging objective lens after reflection by the second reflector at intersection point one; the third reflector is disposed on intersection point one, and the third reflector is disposed parallel to the first reflector;

[0010] Furthermore, the light source assembly adopts a single light source structure and also includes a housing and a light transmission adjustment component. The light source is assembled inside the housing, and the light transmission adjustment component is disposed at the light-emitting end of the light source, and the light transmission adjustment component is coaxially disposed with the light source.

[0011] Furthermore, the housing includes an upper shell and a lower shell connected to each other to form an inverted T-shaped structure. The light source includes a light-diffusing plate, LED beads, and a metal substrate. The metal substrate is installed in the upper shell, and a fixed shell is installed inside the lower shell. The light-diffusing plate is installed on the fixed shell and is positioned opposite to the LED beads arranged on the metal substrate through a through hole on the fixed shell. The wires connected to the metal substrate are led out from the upper shell and connected to an external power source.

[0012] Furthermore, the light transmission adjustment component adopts an adjustable aperture, which is installed at the bottom of the lower shell. An aperture gear is rotatably connected to the outside of the upper shell. A shift fork is mounted on the aperture gear, and the bottom of the shift fork is connected to a handle extending from the adjustable aperture. An aperture motor is provided on the outside of the shell, and the aperture motor is connected to a gear, which meshes with the aperture gear.

[0013] Furthermore, the housing is equipped with a driving mechanism to ensure that the light emitted by the light source illuminates the fingerprint sample at the sample hole at a vertical angle or at a certain angle.

[0014] Furthermore, the driving mechanism adopts a moving mechanism, the light source assembly is connected to the moving mechanism, and the light source is moved on the focal plane of the condenser lens by the driving of the moving mechanism, so that the light emitted by the light source can be perpendicularly irradiated or obliquely irradiated at a certain angle onto the fingerprint object at the inspection hole;

[0015] Furthermore, the moving mechanism includes an assembly moving frame mounted inside the housing, the light source assembly and the aperture motor are both mounted on the assembly moving frame, the screw is threadedly connected to the assembly moving frame, the two ends of the screw are rotatably connected to the inner wall of the housing, the inner wall of the housing is equipped with a moving frame motor and a worm gear connected to the moving frame motor, the screw and the worm gear are both connected to a worm wheel, and slide rod one and slide rod two both pass through the assembly moving frame and are connected to the inner wall of the housing;

[0016] Furthermore, the driving mechanism adopts a rotating mechanism, and a light source reflector is also provided inside the housing. The light source reflector is disposed in the illumination light path between the light source and the condenser lens. The light source reflector is connected to the rotating mechanism, and the angle of the light source reflector is adjusted by rotating it through the driving mechanism, so that the light emitted by the light source can be vertically irradiated or tilted at a certain angle to irradiate the fingerprint object at the inspection hole.

[0017] Furthermore, the central axis of the light source and the optical axis of the condenser lens are both parallel to the bottom plane of the housing and intersect perpendicularly at intersection point two; the light source reflector is disposed at intersection point two, and the light source reflector is perpendicular to the bottom plane of the housing;

[0018] Furthermore, the rotating mechanism includes a fixed frame, which is fixed to the bottom inner wall of the housing. The light source assembly and the aperture motor are both mounted on the fixed frame. A rotating frame is rotatably connected to the fixed frame via a rotating shaft. The light source reflector is mounted on the rotating frame. The rotating shaft is perpendicular to the bottom plane of the housing. A reflector gear is mounted at one end of the rotating shaft. A reflector motor is mounted on the fixed frame. The reflector motor is connected to a second gear, and the second gear meshes with the reflector gear.

[0019] The beneficial effects of this invention are that it utilizes a beam splitter for reflection imaging. By setting a first, second, and third reflector, it forms multi-level reflections in the horizontal direction on the imaging optical path, further increasing the optical path length of the imaging optical path. This not only enables various bright and dark field imaging of fingerprints, but also reduces the overall height and size of the device while better reducing background pattern interference and obtaining higher quality fingerprint images, making the device more portable and easier to use. Attached Figure Description

[0020] Figure 1 This is a three-dimensional structural schematic diagram of Embodiment 1 of the present invention;

[0021] Figure 2 This is a schematic diagram of the main structure of Embodiment 1 of the present invention;

[0022] Figure 3 yes Figure 2 AA-direction cross section;

[0023] Figure 4 yes Figure 2 BB-direction cross-section;

[0024] Figure 5 yes Figure 3 CC-direction cross-section;

[0025] Figure 6 This is a schematic diagram of the lighting optical path according to Embodiment 1 of the present invention;

[0026] Figure 7 This is a schematic diagram of the imaging optical path according to Embodiment 1 of the present invention;

[0027] Figure 8 This is a three-dimensional structural schematic diagram of Embodiment 2 of the present invention;

[0028] Figure 9 This is a schematic diagram of the main structure of Embodiment 2 of the present invention;

[0029] Figure 10 yes Figure 9 AA-direction cross section;

[0030] Figure 11 yes Figure 9 BB-direction cross-section;

[0031] Figure 12 yes Figure 10 CC-direction cross-section;

[0032] Figure 13 This is a schematic diagram of the illumination optical path according to Embodiment 2 of the present invention;

[0033] Figure 14 This is a schematic diagram of the imaging optical path according to Embodiment 2 of the present invention;

[0034] Figure 15 These are three-dimensional structural schematic diagrams of the light source assembly in Embodiments 1 and 2 of the present invention;

[0035] Figure 16 This is a cross-sectional view of the light source assembly in Embodiment 1 and Embodiment 2 of the present invention.

[0036] Figures 1 to 16 Components: 1. Housing; 2. Camera aperture; 3. Light source assembly; 4. Beam splitter; 5. Sample inspection port; 6. Condenser lens; 7. Imaging objective lens; 8. First reflector; 9. Second reflector; 10. Third reflector; 11. Light source; 12. Lower shell; 13. Upper shell; 14. Diffusion plate; 15. LED beads; 16. Metal substrate; 17. Adjustable aperture; 18. Handle; 19. Fixing shell; 20. Wire; 21. Aperture gear 22. Shift fork; 23. Assembly moving frame; 24. Screw; 25. Slide rod one; 26. Slide rod two; 27. Worm gear; 28. Moving frame motor; 29. ​​Worm; 30. Aperture motor; 31. Gear one; 32. Light source reflector; 33. Fixed frame; 34. Rotating frame; 35. Reflector gear; 36. Reflector motor; 37. Gear two; 38. Rotating shaft; 39. Through hole; 40. Intersection one; 41. Intersection two. Detailed Implementation

[0037] Example 1

[0038] like Figures 1 to 7 , Figure 15 , Figure 16As shown, a portable fingerprint camera with horizontal multi-stage reflection beam splitter imaging includes a housing 1. Inside the housing 1, there is a light source assembly 3 and a beam splitter 4. The light source assembly 3 includes a light source 11. The housing 1 has a camera aperture 2 and a sample aperture 5 for illuminating a fingerprint object (not shown in the figure). The light emitted by the light source 11 is transmitted through the beam splitter 4 to form an illumination light path. The illumination light path also includes a first reflector 8. The light transmitted through the beam splitter 4 is then reflected by the first reflector 8 to the sample aperture 5 at the end of the illumination light path. The light reflected by the fingerprint object located at the sample aperture 5 after being illuminated is then reflected by the first reflector 8 and the beam splitter 4 to form an imaging light path. The formed imaging light path is reflected by a second reflector 9 and a third reflector 10 to the camera aperture 2 at the end of the imaging light path. The light path from the light source 11 to the first reflector 8 and the light path from the first reflector 8 to the third reflector 10 are both located in the horizontal direction.

[0039] The housing 1 is also equipped with a condenser lens 6 and an imaging objective lens 7. The condenser lens 6 is located in the illumination optical path between the light source 11 and the beam splitter 4, and the imaging objective lens 7 is located in the imaging optical path between the beam splitter 4 and the camera aperture 2.

[0040] The optical distance between the condenser lens 6 and the light source 11 is the same as the focal length of the condenser lens 6; the imaging objective lens 7 is set on the imaging optical path between the beam splitter 4 and the second mirror 9, and the optical axis of the imaging objective lens 7 and the optical axis of the condenser lens 6 are both parallel to the bottom plane of the housing 1, and the two optical axes intersect perpendicularly; the beam splitter 4 is set on the angle bisector of the right angle formed by the intersection of the two optical axes, and the beam splitter 4 is perpendicular to the bottom plane of the housing 1.

[0041] The inspection hole 5 is located at the bottom of the box 1, the first reflector 8 is located directly above the inspection hole 5, and the beam splitter 4 is located on the horizontal side of the first reflector 8; the optical axis of the condenser 6 intersects perpendicularly with the central axis of the inspection hole 5; the first reflector 8 is located at the intersection of the two axes and is perpendicular to the angle bisector of the right angle formed by the intersection of the two axes.

[0042] The second mirror 9 is disposed on the imaging optical path between the imaging objective lens 7 and the third mirror 10, and the second mirror 9 is disposed parallel to the beam splitter 4; the camera aperture 2 is disposed on the top of the housing 1 directly above the third mirror 10, and the central axis of the camera aperture 2 intersects perpendicularly with the optical axis of the imaging objective lens 7 after being reflected by the second mirror 9 at the intersection point 40; the third mirror 10 is disposed on the intersection point 40, and the third mirror 10 is disposed parallel to the first mirror 8.

[0043] The light source assembly 3 adopts a single light source structure and also includes a housing and a light transmission adjustment component. The light source 11 is assembled inside the housing, and the light transmission adjustment component is located at the light-emitting end of the light source 11 and is coaxially arranged with the light source 11. The housing includes an upper housing 13 and a lower housing 12 connected to each other to form an inverted T-shaped structure. The light source 11 includes a light-diffusing plate 14, LED beads 15, and a metal substrate 16. The metal substrate 16 is installed in the upper housing 13, and a fixing shell 19 is installed inside the lower housing 12. The light-diffusing plate 14 is mounted on the fixing shell 19 and is positioned opposite to the LED beads 15 arranged on the metal substrate 16 through a through hole 39 on the fixing shell 19. The metal substrate 16 is connected to... The wire 20 is led out from the upper shell 13 and connected to an external power source; the light transmission adjustment component adopts an adjustable aperture 17, which is existing technology and will not be described in detail in this patent. The adjustable aperture 17 is provided with a handle 18 for adjusting the size of the aperture. The adjustable aperture 17 is installed at the bottom of the lower shell 12. An aperture gear 21 is rotatably connected to the outside of the upper shell 13. A fork 22 is mounted on the aperture gear 21, and the bottom of the fork 22 is connected to the handle 18 led out from the adjustable aperture 17, that is, the fork head of the fork 22 is inserted into the handle 18; an aperture motor 30 is provided on the outside of the shell. The aperture motor 30 is connected to a gear 31, and the gear 31 meshes with the aperture gear 21.

[0044] The housing 1 is equipped with a drive mechanism to make the light emitted by the light source 11 shine vertically or at a certain angle onto the fingerprint sample at the inspection hole 5. Specifically, the drive mechanism is a moving mechanism. The light source assembly 3 is connected to the moving mechanism, and the light source 11 moves on the focal plane of the condenser lens 6 through the drive of the moving mechanism. The moving mechanism includes an assembly moving frame 23 installed in the housing 1. The light source assembly 3 and the aperture motor 30 are both installed on the assembly moving frame 23. The screw 24 is threadedly connected to the assembly moving frame 23. The two ends of the screw 24 are rotatably connected to the inner wall of the housing 1. The inner wall of the housing 1 is equipped with a moving frame motor 28 and a worm gear 29 connected to the moving frame motor 28. The screw 24 and the worm gear 29 are both connected to the worm wheel 27. The slide rod 1 25 and the slide rod 26 pass through the assembly moving frame 23 and are connected to the inner wall of the housing 1.

[0045] The principle for achieving perpendicular or angled illumination of the light emitted by the light source 11 onto the fingerprint sample at the inspection hole 5 is as follows: the moving frame motor 28 drives the worm gear 29 to rotate, the worm gear 29 drives the worm wheel 27 and the screw 24 to rotate, and the screw 24 drives the moving frame 23 of the assembly to slide along the slide bar 1 25 and the slide bar 26, thereby allowing the light source 11 in the light source assembly 3 to move on the focal plane of the condenser lens 6. When the center of the light source 11 is located at the focal point on the axis of the condenser lens 6, the light emitted by the light source 11 is perpendicularly illuminated onto the fingerprint sample at the inspection hole 5. When the center of the light source 11 deviates from the focal point on the axis of the condenser lens 6, the light emitted by the light source 11 is angled onto the fingerprint sample at the inspection hole 5. The aperture motor 30 drives the gear 1 31 to rotate, the gear 1 31 drives the aperture gear 21 to rotate, and the aperture gear 21 drives the shift fork 22 and the handle 18 to rotate, thereby changing the aperture of the adjustable aperture 17.

[0046] The working process of this invention is as follows:

[0047] Bright-field fingerprint display: By moving the assembly moving frame 23, the center of the light source 11 in the light source assembly 3 is placed at the focal point on the axis of the condenser lens 6. Powering on the LED beads 15 causes them to emit light, which illuminates the light-diffusing plate 14. The light-emitting area of ​​the light-diffusing plate 14 is controlled by changing the aperture of the adjustable aperture 17. The light emitted by the light source 11 is converged by the condenser lens 6 and becomes approximately parallel light. After passing through the beam splitter 4 and being reflected by the first reflector 8, the light is almost perpendicularly projected onto the fingerprint sample at the sample hole 5. The smooth and flat surface of the fingerprint sample is equivalent to a mirror. The reflected light is still approximately parallel light. After the first reflection by the first mirror 8 and the second reflection by the beam splitter 4, it enters the imaging objective lens 7, then after the third reflection by the second mirror 9 and the fourth reflection by the third mirror 10, it reaches the camera aperture 2 and is finally imaged by the camera, appearing as a light-colored bright field background. Meanwhile, the fingerprint ridges on the surface of the fingerprint object and the background pattern beneath the surface, under the illumination of the light emitted by the light source 11, have scattered reflected light. After four reflections by the first mirror 8, the beam splitter 4, the second mirror 9, and the third mirror 10, the reflected light finally enters the camera at the camera aperture 2. The light flux in the imaging is relatively low, and the fingerprint ridges appear as dark ridges with lower brightness than the light-colored background, which also weakens the background pattern. Compared with the traditional beam splitter transmission imaging method and the reflection imaging portable fingerprint camera (patent number: ZL202021197355.1), the optical path length of the imaging light reaching the top of the device after four reflections by the first reflector 8, beam splitter 4, second reflector 9 and third reflector 10 is greatly extended. The reflected light of the fingerprint ridges and the background pattern under the object surface is diffused. As the optical path lengthens, the amount of light entering the camera at the aperture 2 decreases significantly. However, the reflected light from the smooth and flat surface of the fingerprint object is approximately parallel, so the amount of light entering the camera at the aperture 2 decreases only slightly as the optical path length increases. Therefore, extending the optical path of the imaging optical path can increase the contrast between the fingerprint ridges and the light-colored background, resulting in better weakening of the background pattern. Furthermore, by adjusting the aperture of the adjustable aperture 17, the illumination intensity of the fingerprint ridges and the underlying background pattern on the object surface can be further increased or decreased, and the brightness of the light source 11 can be adjusted until the fingerprint ridges are displayed to their optimal effect.

[0048] Dark-field fingerprint development: The parameter settings are consistent with those for bright-field fingerprint development in this invention. First, a bright-field fingerprint image is developed. By moving the light source assembly 3, the center of the light source 11 is deviated from the focal point on the axis of the condenser lens 6. This causes the light emitted from the light source 11 to converge into approximately parallel light after passing through the condenser lens 6. This light is then transmitted through the beam splitter 4 and reflected by the first reflector 8 before being tilted at a certain angle to illuminate the fingerprint sample at the sample hole 5. The smooth, flat surface of the fingerprint sample acts like a mirror, and the reflected light remains approximately parallel. As the illumination tilt angle of the fingerprint sample increases, the reflected light passes through the first reflector 8, the beam splitter 4, the second reflector 9, and the third reflector 1... After four reflections, the light from the fingerprint object deviates further and further from the optical axis of the imaging path, resulting in less and less light flux reaching the camera at aperture 2. This causes the smooth and flat surface of the fingerprint object to be imaged as a dark background in a dark field. However, when the fingerprint ridges on the object are illuminated by oblique, nearly parallel light, the reflected light has scattering properties, resulting in a relatively large amount of light flux entering the camera at aperture 2. The fingerprint ridges appear as light-colored ridges with higher brightness than the dark background. By further moving the position of the light source assembly 3 to change the incident angle of the incident light on the fingerprint object, and adjusting the aperture of the adjustable aperture 17, the brightness of the light source 11 can be adjusted until the fingerprint ridges are displayed to their best effect.

[0049] Example 2

[0050] like Figures 8 to 16 As shown, Figures 8 to 16 As shown, a portable fingerprint camera with horizontal multi-stage reflection beam splitter imaging includes a housing 1. Inside the housing 1, there is a light source assembly 3 and a beam splitter 4. The light source assembly 3 includes a light source 11. The housing 1 has a camera aperture 2 and a sample aperture 5 for illuminating a fingerprint object (not shown in the figure). The light emitted by the light source 11 is transmitted through the beam splitter 4 to form an illumination light path. The illumination light path also includes a first reflector 8. The light transmitted through the beam splitter 4 is then reflected by the first reflector 8 to the sample aperture 5 at the end of the illumination light path. The light reflected by the fingerprint object located at the sample aperture 5 after being illuminated is then reflected by the first reflector 8 and the beam splitter 4 to form an imaging light path. The formed imaging light path is reflected by a second reflector 9 and a third reflector 10 to the camera aperture 2 at the end of the imaging light path. The light path from the light source 11 to the first reflector 8 and the light path from the first reflector 8 to the third reflector 10 are both located in the horizontal direction.

[0051] The housing 1 is also equipped with a condenser lens 6 and an imaging objective lens 7. The condenser lens 6 is located in the illumination optical path between the light source 11 and the beam splitter 4, and the imaging objective lens 7 is located in the imaging optical path between the beam splitter 4 and the camera aperture 2.

[0052] The optical distance between the condenser lens 6 and the light source 11 is the same as the focal length of the condenser lens 6; the imaging objective lens 7 is set on the imaging optical path between the beam splitter 4 and the second mirror 9, and the optical axis of the imaging objective lens 7 and the optical axis of the condenser lens 6 are both parallel to the bottom plane of the housing 1, and the two optical axes intersect perpendicularly; the beam splitter 4 is set on the angle bisector of the right angle formed by the intersection of the two optical axes, and the beam splitter 4 is perpendicular to the bottom plane of the housing 1.

[0053] The inspection hole 5 is located at the bottom of the box 1, the first reflector 8 is located directly above the inspection hole 5, and the beam splitter 4 is located on the horizontal side of the first reflector 8; the optical axis of the condenser 6 intersects perpendicularly with the central axis of the inspection hole 5; the first reflector 8 is located at the intersection of the two axes and is perpendicular to the angle bisector of the right angle formed by the intersection of the two axes.

[0054] The second mirror 9 is disposed on the imaging optical path between the imaging objective lens 7 and the third mirror 10, and the second mirror 9 is disposed parallel to the beam splitter 4; the camera aperture 2 is disposed on the top of the housing 1 directly above the third mirror 10, and the central axis of the camera aperture 2 intersects perpendicularly with the optical axis of the imaging objective lens 7 after being reflected by the second mirror 9 at the intersection point 40; the third mirror 10 is disposed on the intersection point 40, and the third mirror 10 is disposed parallel to the first mirror 8.

[0055] The light source assembly 3 adopts a single light source structure and also includes a housing and a light transmission adjustment component. The light source 11 is assembled inside the housing, and the light transmission adjustment component is located at the light-emitting end of the light source 11 and is coaxially arranged with the light source 11. The housing includes an upper housing 13 and a lower housing 12 connected to each other to form an inverted T-shaped structure. The light source 11 includes a light-diffusing plate 14, LED beads 15, and a metal substrate 16. The metal substrate 16 is installed in the upper housing 13, and a fixing shell 19 is installed inside the lower housing 12. The light-diffusing plate 14 is mounted on the fixing shell 19 and is positioned opposite to the LED beads 15 arranged on the metal substrate 16 through a through hole 39 on the fixing shell 19. The metal substrate 16 is connected to... The wire 20 is led out from the upper shell 13 and connected to an external power source; the light transmission adjustment component adopts an adjustable aperture 17, which is existing technology and will not be described in detail in this patent. The adjustable aperture 17 is provided with a handle 18 for adjusting the size of the aperture. The adjustable aperture 17 is installed at the bottom of the lower shell 12. An aperture gear 21 is rotatably connected to the outside of the upper shell 13. A fork 22 is mounted on the aperture gear 21, and the bottom of the fork 22 is connected to the handle 18 led out from the adjustable aperture 17, that is, the fork head of the fork 22 is inserted into the handle 18; an aperture motor 30 is provided on the outside of the shell. The aperture motor 30 is connected to a gear 31, and the gear 31 meshes with the aperture gear 21.

[0056] The housing 1 is equipped with a driving mechanism to ensure that the light emitted by the light source 11 illuminates the fingerprint sample at the inspection hole 5 perpendicularly or at a certain angle. Specifically, the driving mechanism is a rotating mechanism. The housing 1 is also equipped with a light source reflector 32, which is located in the illumination path between the light source 11 and the condenser lens 6. The light source reflector 32 is connected to the rotating mechanism, and the angle of the light source reflector 32 is adjusted by rotating the rotating mechanism to ensure that the light emitted by the light source 11 illuminates the fingerprint sample at the inspection hole 5 perpendicularly or at a certain angle. The central axis of the light source 11 and the optical axis of the condenser lens 6 are both parallel to the bottom plane of the housing 1 and intersect perpendicularly at intersection point 41. The light source reflector 32 is located at intersection point 41 and is perpendicular to the bottom plane of the housing 1.

[0057] The rotating mechanism includes a fixed frame 33, which is fixed to the bottom inner wall of the housing 1. The light source assembly 3 and the aperture motor 30 are both mounted on the fixed frame 33. A rotating frame 34 is rotatably connected to the fixed frame 33 via a rotating shaft 38. The light source reflector 32 is mounted on the rotating frame 34. The rotating shaft 38 is perpendicular to the bottom plane of the housing 1. A reflector gear 35 is mounted on one end of the rotating shaft 38. A reflector motor 36 is mounted on the fixed frame 33. The reflector motor 36 is connected to a second gear 37. The second gear 37 meshes with the reflector gear 35.

[0058] The principle of achieving perpendicular or angled illumination of the light emitted by the light source 11 onto the fingerprint sample hole 5 is as follows: the reflector motor 36 drives the gear 2 37 to rotate, and the gear 2 37 drives the reflector gear 35 and the rotating frame 34 to rotate along the rotating shaft 38, thereby causing the light source reflector 32 to rotate. When the light source reflector 32 is perpendicular to the angle bisector of the right angle formed by the central axis of the light source 11 and the optical axis of the condenser lens 6, that is, when the light source reflector 32 deflects the light emitted by the light source 11 horizontally by 90°, the light emitted by the light source 11 is perpendicularly illuminated onto the sample hole. The fingerprint at point 5 is illuminated at a certain angle by the light source reflector 32 when it is not perpendicular to the angle bisector of the right angle formed by the central axis of the light source 11 and the optical axis of the condenser lens 6. That is, when the light source reflector 32 deflects the light emitted by the light source 11 horizontally by more than 90° or less than 90°, the light emitted by the light source 11 is tilted to illuminate the fingerprint at point 5. The aperture motor 30 drives the gear 31 to rotate, the gear 31 drives the aperture gear 21 to rotate, and the aperture gear 21 drives the shift fork 22 and the handle 18 to rotate, thereby changing the light transmission aperture of the adjustable aperture 17.

[0059] The working process of this invention is as follows:

[0060] Bright-field fingerprint display: By rotating the light source reflector 32, the light source reflector 32 is perpendicular to the angle bisector of the right angle formed by the central axis of the light source 11 and the optical axis of the condenser lens 6. That is, the light source reflector 32 deflects the light emitted by the light source 11 horizontally by 90°. Powering on the LED beads 15 causes them to emit light, which illuminates the light-diffusing plate 14. The light-emitting area of ​​the light-diffusing plate 14 is controlled by changing the aperture of the adjustable aperture 17. The light emitted by the light source 11 is reflected by the light source reflector 32 and converged by the condenser lens 6 to become approximately parallel light. It is then transmitted through the beam splitter 4 and reflected by the first reflector 8. The fingerprint sample, illuminated almost perpendicularly to the sample aperture 5, has a smooth, flat surface that acts like a mirror. The reflected light remains nearly parallel, undergoing a first reflection by the first reflector 8 and a second reflection by the beam splitter 4 before entering the imaging objective lens 7. It then undergoes a third reflection by the second reflector 9 and a fourth reflection by the third reflector 10 before reaching the camera aperture 2. Finally, it is imaged by the camera, appearing as a bright field against a light-colored background. Meanwhile, the fingerprint ridges on the surface of the sample and the background pattern beneath the surface, illuminated by the light source 11, exhibit scattering properties. The reflected light passes through the first reflector 8, the beam splitter 4, and the second reflector 9... After four reflections by the third reflector 10, the light flux entering the camera at the aperture 2 is relatively small, resulting in fingerprint ridges appearing as dark ridges with lower brightness than a light background, and the background pattern is also weakened. Compared to the optical path length of the reflected light from the fingerprint object reaching the top of the device in traditional beam splitter transmission imaging and reflection imaging portable fingerprint imaging devices (patent number: ZL202021197355.1), the optical path length of the imaging light reaching the aperture 2 after four reflections by the first reflector 8, beam splitter 4, second reflector 9, and third reflector 10 is greatly extended, making the fingerprint ridges and the lower layer of the object surface more distinct. Since the reflected light from the background pattern is scattered light, the amount of light entering the camera at the aperture 2 decreases significantly as the optical path lengthens. However, since the reflected light from the smooth and flat surface of the fingerprint object is nearly parallel light, the amount of light entering the camera at the aperture 2 decreases only slightly as the optical path lengthens. Therefore, extending the optical path of the imaging optical path can increase the contrast between the fingerprint ridges and the light-colored background, resulting in better weakening of the background pattern. Furthermore, by adjusting the aperture of the adjustable stop 17, the illumination intensity of the fingerprint ridges and the underlying background pattern on the object surface can be further increased or decreased, and the brightness of the light source 11 can be adjusted until the fingerprint ridges are displayed to their optimal effect.

[0061] Dark-field fingerprint development: The parameter settings are consistent with those of the bright-field fingerprint development in this invention. First, a bright-field fingerprint image is displayed. By rotating the light source reflector 32, the light emitted by the light source 11 deviates from its original 90° angle. This means the light emitted by the light source 11, after being reflected by the light source reflector 32 and converged by the condenser lens 6, becomes approximately parallel light. This light is then transmitted through the beam splitter 4 and reflected by the first reflector 8 before being tilted at a certain angle to illuminate the fingerprint sample at the sample hole 5. The smooth, flat surface of the fingerprint sample acts like a mirror, and its reflected light remains approximately parallel. As the illumination tilt angle of the fingerprint sample increases, the reflected light passes through the first reflector 8, the beam splitter 4, the second reflector 9, and... After the third reflector 10 reflects light four times, it deviates further and further from the optical axis of the imaging light path. Eventually, the amount of light reaching the camera at the aperture 2 decreases, resulting in the smooth and flat surface of the fingerprint object being imaged as a dark background in a dark field. However, when the fingerprint ridges on the object are illuminated by oblique, nearly parallel light, the reflected light has scattering properties, resulting in a relatively large amount of light reaching the camera at the aperture 2. The fingerprint ridges appear as light-colored ridges with higher brightness than the dark background. By further rotating the light source reflector 32 to change the incident angle of the incident light on the fingerprint object and adjusting the aperture of the adjustable aperture 17, the brightness of the light source 11 can be adjusted until the fingerprint ridges are displayed to their best effect.

[0062] In summary, the photographic apparatus of the present invention utilizes the beam splitter 4 for reflection imaging. Through the cooperation of the light source assembly 3 and the condenser lens 6, approximately parallel light is obtained to illuminate the fingerprint object. The light reflected from the fingerprint object reaches the photographic aperture 2 after four reflections by the first reflector 8, the beam splitter 4, the second reflector 9, and the third reflector 10, thus extending the optical path of the imaging light path. This greatly enhances the contrast between the fingerprint ridges and the background of the object in the bright field fingerprint display mode, better reduces or even eliminates the interference of the background pattern, and obtains a higher quality bright field fingerprint image. Secondly, by moving the light source assembly 3 or rotating the light source reflector 32 to change the direction of the light path, the incident light can be made to illuminate the fingerprint object perpendicularly or obliquely, thus obtaining a bright field or dark field image of the fingerprint. In conclusion, by arranging the optical components such as the light source assembly 3, the beam splitter 4, the condenser lens 6, the imaging objective lens 7, the first reflector 8, the second reflector 9, and the third reflector 10 on the same horizontal plane, the overall height of the device can be further reduced, making the device more portable and easier to use.

[0063] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. For example, by moving the condenser lens 6 perpendicular to the optical axis, the light emitted by the light source 11 can be directed perpendicularly or at a certain angle to the fingerprint sample at the sample aperture 5; increasing the number of reflectors in the imaging optical path can further extend the imaging optical path. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0064] 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 portable fingerprint camera with horizontal multi-level reflection beam splitter imaging, comprising a housing, wherein a light source assembly and a beam splitter are disposed within the housing, the light source assembly including a light source, and the housing having a photographic aperture and a sample inspection aperture, wherein light emitted from the light source is transmitted through the beam splitter to form an illumination optical path, characterized in that: The illumination optical path also includes a first reflector. Light transmitted through the beam splitter is reflected by the first reflector to the sample aperture at the end of the illumination optical path. Light reflected from the fingerprint sample located at the sample aperture is reflected by the first reflector and the beam splitter to form an imaging optical path. The light is then reflected by a second and a third reflector to the camera aperture at the end of the imaging optical path. The optical paths from the light source to the first reflector and from the first reflector to the third reflector are both horizontal. The housing also includes a condenser lens and an imaging objective lens. The condenser lens is positioned on the illumination optical path between the light source and the beam splitter, and the imaging objective lens is positioned on the imaging optical path between the beam splitter and the camera aperture. The optical distance between the condenser lens and the light source is the same as the focal length of the condenser lens. The imaging objective lens is positioned on the imaging optical path between the beam splitter and the second reflector. The optical axes of the objective lens and the condenser lens are both parallel to the bottom plane of the housing, and the two optical axes intersect perpendicularly. The beam splitter is positioned on the angle bisector of the right angle formed by the intersection of the two optical axes, and the beam splitter is perpendicular to the bottom plane of the housing. The sample aperture is located at the bottom of the housing, the first reflector is positioned directly above the sample aperture, and the beam splitter is located horizontally to the side of the first reflector. The optical axis of the condenser lens intersects perpendicularly with the central axis of the sample aperture. The first reflector is positioned at the intersection of the two axes and is perpendicular to the angle bisector of the right angle formed by the intersection of the two axes. The second reflector is positioned on the imaging optical path between the imaging objective lens and the third reflector, and is parallel to the beam splitter. The camera aperture is located on the top of the housing directly above the third reflector, and the central axis of the camera aperture intersects perpendicularly with the optical axis of the imaging objective lens after reflection by the second reflector at intersection point one. The third reflector is disposed at the intersection point one, and the third reflector is disposed parallel to the first reflector.

2. The portable fingerprint camera with horizontal multi-level reflection beam splitter reflection imaging according to claim 1, characterized in that: The light source assembly adopts a single light source structure and also includes a housing and a light transmission adjustment component. The light source is assembled in the housing, and the light transmission adjustment component is disposed at the light-emitting end of the light source and is coaxially disposed with the light source.

3. The portable fingerprint camera with horizontal multi-level reflection beam splitter reflection imaging according to claim 2, characterized in that: The housing includes an upper shell and a lower shell connected to each other to form an inverted T-shaped structure. The light source includes a light-diffusing plate, LED beads, and a metal substrate. The metal substrate is installed in the upper shell, and a fixed shell is installed inside the lower shell. The light-diffusing plate is installed on the fixed shell and is arranged opposite to the LED beads arranged on the metal substrate through a through hole on the fixed shell. The wires connected to the metal substrate are led out from the upper shell and connected to an external power source.

4. The portable fingerprint camera with horizontal multi-level reflection beam splitter reflection imaging according to claim 3, characterized in that: The light transmission adjustment component adopts an adjustable aperture, which is installed at the bottom of the lower shell. An aperture gear is rotatably connected to the outside of the upper shell. A shift fork is mounted on the aperture gear, and the bottom of the shift fork is connected to a handle extending from the adjustable aperture. An aperture motor is provided on the outside of the shell, and the aperture motor is connected to a gear, which meshes with the aperture gear.

5. The portable fingerprint camera with horizontal multi-level reflection beam splitter reflection imaging according to claim 4, characterized in that: The housing is equipped with a driving mechanism to ensure that the light emitted by the light source shines vertically or at a certain angle onto the fingerprint sample at the sample hole.

6. The portable fingerprint camera with horizontal multi-level reflection beam splitter reflection imaging according to claim 5, characterized in that: The driving mechanism is a moving mechanism. The light source assembly is connected to the moving mechanism. Driven by the moving mechanism, the light source moves on the focal plane of the condenser lens, so that the light emitted by the light source can be perpendicularly irradiated or obliquely irradiated at a certain angle onto the fingerprint object at the sample hole.

7. The portable fingerprint camera with horizontal multi-level reflection beam splitter reflection imaging according to claim 6, characterized in that: The moving mechanism includes an assembly moving frame mounted inside the housing. The light source assembly and aperture motor are both mounted on the assembly moving frame. A screw is threadedly connected to the assembly moving frame. Both ends of the screw are rotatably connected to the inner wall of the housing. The inner wall of the housing is equipped with a moving frame motor and a worm gear connected to the moving frame motor. The screw and worm gear are both connected to a worm wheel. Slide rod one and slide rod two both pass through the assembly moving frame and are connected to the inner wall of the housing.

8. The portable fingerprint camera with horizontal multi-level reflection beam splitter reflection imaging according to claim 5, characterized in that: The driving mechanism is a rotating mechanism, and a light source reflector is also provided inside the housing. The light source reflector is located in the illumination light path between the light source and the condenser lens. The light source reflector is connected to the rotating mechanism, and the angle of the light source reflector is adjusted by rotating it through the rotating mechanism, so that the light emitted by the light source can be vertically irradiated or tilted at a certain angle onto the fingerprint object at the inspection hole.

9. The portable fingerprint camera with horizontal multi-level reflection beam splitter reflection imaging according to claim 8, characterized in that: The central axis of the light source and the optical axis of the condenser are both parallel to the bottom plane of the housing and intersect perpendicularly at intersection point two; the light source reflector is set on intersection point two, and the light source reflector is perpendicular to the bottom plane of the housing.

10. The portable fingerprint camera with horizontal multi-level reflection beam splitter reflection imaging according to claim 9, characterized in that: The rotating mechanism includes a fixed frame, which is fixed to the bottom inner wall of the housing. The light source assembly and the aperture motor are both mounted on the fixed frame. A rotating frame is rotatably connected to the fixed frame via a rotating shaft. The light source reflector is mounted on the rotating frame. The rotating shaft is perpendicular to the bottom plane of the housing. A reflector gear is mounted on one end of the rotating shaft. A reflector motor is mounted on the fixed frame. The reflector motor is connected to a second gear, and the second gear meshes with the reflector gear.

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