CN112257675A - A non-contact fingerprint collection device for rotating photography - Google Patents

The invention discloses a non-contact fingerprint acquisition device for rotary shooting, which comprises: the device comprises a finger placing mechanism, a rotating mechanism and a linear array camera arranged on the rotating mechanism; the finger placing mechanism is used for fixedly placing fingers; the rotating mechanism drives the linear array camera to rotate around the circumferential direction of the finger on the finger placing mechanism, and triggers the linear array camera to scan and shoot the finger fingerprint surface in the rotating process. The 2D fingerprint image of finger fingerprint face can directly be obtained to rotatory mode of shooing, obtains higher image quality, obtains the fingerprint image of bigger area, and the true validity of the fingerprint of assurance more is close to the requirement of GA standard.

Non-contact fingerprint acquisition device of rotatory shooting

Technical Field

The invention belongs to the field of fingerprint acquisition, and relates to a non-contact fingerprint acquisition device for rotary shooting.

Background

Most conventional fingerprint image capture systems for police systems, security, customs and entry and exit rely on physical contact between a finger and a fingerprint capture device. When a high quality, complete, large area fingerprint is required, the finger needs to be rolled from side to side on the fingerprint acquisition device to increase the total contact area. When such devices are used by unskilled and non-compliant acquirers, the additional force for acquisition often results in large deformations and distortions of the fingerprint, and the acquirers may move the finger intentionally or unintentionally during the acquisition process causing the acquired images of the fingerprint to be blurred, thereby failing in acquisition. These problems greatly increase the difficulty and time of acquiring large-area and high-quality fingerprints, resulting in poor user experience. The contact type fingerprint acquisition instrument not only has low acquisition speed, but also causes the worry of people on the aspect of sanitation.

In some non-contact fingerprint acquisition methods, for example, after multiple area-array cameras or 3D depth cameras (such as binocular cameras or three-dimensional stereo cameras) are combined with structured light for shooting, images need to be processed and adjusted by a large amount of post-software (such as a method of performing 3D modeling and then expanding the images into 2D images or image splicing), splicing traces can appear in generated images, and the images have large differences in matching with real objects. The quality of fingerprint images acquired by the non-contact fingerprint instruments is not good enough, the area of the acquired fingerprints is limited, and the reliability problem exists. In addition, the criminal investigation fingerprint collection specified in the GA standard adopts a rolling type fingerprint collection method, and the fingerprint image obtained by adopting complicated algorithm modeling, converting and splicing in the existing non-contact fingerprint collection and the fingerprint image obtained by rolling type fingerprint collection have larger difference, so that the authenticity and the effectiveness of the fingerprint are influenced, and the fingerprint quality required by the GA standard can not be achieved.

Disclosure of Invention

The invention aims to: the utility model provides a through linear array camera around rotatory non-contact fingerprint collection device who shoots the fingerprint of fingerprint face, can all-round scanning shoot the fingerprint through rotating around the fingerprint face, directly obtain finger fingerprint face 2D fingerprint image, obtain higher image quality, obtain the fingerprint image of bigger area.

The technical scheme of the invention is as follows: a non-contact fingerprint acquisition device for rotational photography, the non-contact fingerprint acquisition device comprising: the system comprises a finger placing mechanism, a rotating mechanism and a linear array camera arranged on the rotating mechanism;

the finger placing mechanism is used for fixedly placing fingers;

the rotating mechanism drives the linear array camera to rotate around the circumferential direction of the fingers on the finger placing mechanism, and triggers the linear array camera to scan and shoot the finger fingerprint surface in the rotating process.

The further technical scheme is as follows: the non-contact fingerprint acquisition device further comprises: an illuminating light beam with a preset angle;

the lighting light column and the linear array camera are integrally arranged on the rotating mechanism; the rotating mechanism drives the illumination light column and the linear array camera to rotate synchronously; the illumination light column is always aligned to the shooting area of the linear array camera in the rotating process.

The further technical scheme is as follows: the rotating mechanism comprises an installation platform, a stepping motor, a synchronous wheel, a synchronous belt and a coding pulse trigger;

the output shaft of the stepping motor is provided with the synchronous wheel and the coding pulse trigger, and the synchronous belt is connected with the mounting platform and the synchronous wheel; the coding pulse trigger sends a pulse trigger signal according to the rotation of the stepping motor and is used for triggering the linear array camera to carry out scanning shooting; the step motor drives the synchronizing wheel to rotate, the synchronizing wheel drives the synchronous belt to drive, the synchronous belt drives the mounting platform to rotate, and the mounting platform is used for mounting the linear array camera and the lighting light beam.

The further technical scheme is as follows: the rotation stroke angle of the rotating mechanism is larger than the shooting stroke angle of the linear array camera;

the rotation stroke angle of the rotating mechanism and the shooting stroke angle of the linear array camera are symmetrical about an axis perpendicular to the finger positive fingerprint surface.

The further technical scheme is as follows: the rotation stroke angle of the rotating mechanism is 200 degrees +/-10 degrees, and the shooting stroke angle of the linear array camera is 170 degrees +/-10 degrees.

The further technical scheme is as follows: a preset angle is preset between the plane where the lens of the linear array camera is located and the axis direction of the finger, and one side of the linear array camera close to the fingertip inclines towards the fingertip.

The further technical scheme is as follows: the finger placing mechanism comprises a finger placing support and an arc-shaped soft rubber finger clamping device, the arc-shaped soft rubber finger clamping device is used for clamping fingers on the finger placing support, a movable template corresponding to the front end of the fingers is arranged on the finger placing support, and the movable template is automatically pulled out when the fingers are placed in place and start scanning is performed.

The further technical scheme is as follows: the non-contact fingerprint acquisition device further comprises: the finger positioning device comprises annular finger sleeves of different sizes, the annular finger sleeves are used for being sleeved on finger joints, the outer rings of the annular finger sleeves of different sizes are matched with the finger placement mechanism, the inner rings of the annular finger sleeves of different sizes are respectively matched with finger sizes of different thicknesses, and the positions, sleeved on fingers, of the annular finger sleeves correspond to the positions of the arc-shaped soft rubber finger clamping devices.

The further technical scheme is as follows: the non-contact fingerprint acquisition device further comprises: the sucking disc device corresponds the finger back position of finger, the sucking disc device passes through the fixed finger back of the finger of suction that the negative pressure produced.

The further technical scheme is as follows: the non-contact fingerprint acquisition device further comprises: a housing;

the finger placing mechanism and the rotating mechanism are installed on a supporting structure in the shell, a finger placing channel is arranged outside the shell, and the finger placing mechanism is automatically ejected out and automatically reset from the finger placing channel.

The invention has the advantages that:

1. the linear array camera rotates around the fingerprint surface to scan and shoot fingerprints in all directions, so that the problems of image splicing and humming caused by processing and adjusting of a large amount of post-software after shooting by adopting a plurality of area array cameras or 3D depth cameras and large difference of image matching with a real object are solved, a 2D fingerprint image of the fingerprint surface of the finger can be directly obtained, higher image quality is obtained, and a fingerprint image with a larger area is obtained; the method is closer to the rolling fingerprint acquisition method in the GA standard by keeping the finger still and rotating the linear array camera to shoot the fingerprint, so that the problem that the fingerprint image obtained by algorithm modeling is greatly different from the fingerprint image obtained by rolling fingerprint acquisition is solved, the authenticity and the effectiveness of the fingerprint are ensured, and the fingerprint quality required by the GA standard is achieved;

2. the preset angle is preset between the plane of the lens of the linear array camera and the axis direction of the finger, and the lens is inclined towards the fingertip, so that the grains of the fingertip of the finger can be considered in the rotary shooting process of the linear array camera, a fingerprint image with a larger area can be obtained, and the fingerprint image obtained by scanning is more complete;

3. by arranging the annular finger sleeves with different sizes, the outer ring of each annular finger sleeve is matched with the finger placement mechanism, and the inner ring of each annular finger sleeve is suitable for finger sizes with different thicknesses, so that the different finger sizes can be kept fixed on the finger placement mechanism, the fingers are prevented from moving in the acquisition process, and the image quality of fingerprint acquisition is ensured;

4. the finger back is fixed through the sucker device, so that the fixation of the finger can be further kept, and the image quality of fingerprint collection is ensured.

Drawings

The invention is further described with reference to the following figures and examples:

FIG. 1 is a schematic diagram of a non-contact fingerprint acquisition device for rotary photography according to the present application;

fig. 2 is a schematic view of a rotary mechanism provided in one embodiment of the present application;

fig. 3 is a schematic view of a rotary mechanism provided in another embodiment of the present application;

FIG. 4 is a schematic view of a non-contact fingerprint acquisition device with a housing provided herein;

FIG. 5 is a schematic illustration of fingerprint acquisition as provided herein;

FIG. 6 is a schematic diagram of a linear camera for fingerprint acquisition provided by the present application;

FIG. 7 is a schematic view of the illumination of a fingerprint acquisition provided by the present application;

FIG. 8 is a schematic view of a finger placement mechanism for fingerprint acquisition as provided herein;

fig. 9 is a schematic view of a finger placement mechanism with a ring shaped finger cuff as provided herein.

Wherein: 10. a finger placement mechanism; 11. a finger placing bracket; 12. the circular arc-shaped soft rubber finger clamping device; 13. a movable template; 14. an annular finger stall; 20. a rotation mechanism; 21. mounting a platform; 22. a synchronous motor; 23. a synchronous belt; 30. a line camera; 40. an illumination light column; 50. a housing; 51. a support structure; 52. and a sucker mounting bracket.

Detailed Description

The aperture of the line camera lens has an F-number of 4-12, where the F-number is the ratio of the focal length of the line camera lens to the diameter of the entrance pupil, a large F-number corresponds to a small aperture, increasing the depth of field, thus accommodating different finger thicknesses, while still allowing a sharp image of the fingerprint to be acquired, but if the F-number is too large, too little light enters the camera, resulting in insufficient illumination being provided, thus using an F-number in the range of 4-12 to balance the large depth of field with good illumination.

Optionally, the non-contact fingerprint acquisition device further includes: the sucking disc device corresponds the finger back position of finger, and the sucking disc device is through the suction that negative pressure produced fixed finger back of the body.

The application also provides a non-contact fingerprint acquisition method for rotary shooting, which is applied to the non-contact fingerprint acquisition device and can comprise the following steps:

the linear array camera and the lighting light column are driven by the rotating mechanism to start from a preset initial position, when the linear array camera and the lighting light column rotate around the finger placement mechanism by a first preset angle, the linear array camera is controlled to start scanning shooting, the rotation of the rotating mechanism and the shooting of the linear array camera are kept, when the linear array camera rotates around the finger placement mechanism by a second preset angle, the linear array camera is controlled to stop scanning shooting, and then the rotating mechanism is controlled to drive the linear array camera and the lighting light column to stop at a preset stop position;

transmitting the finger fingerprint surface image acquired by the linear array camera to an upper computer;

preprocessing the finger fingerprint surface image by an upper computer, wherein the preprocessing comprises noise filtering and sharpness and saturation enhancement; performing edge identification on the preprocessed fingerprint image, and extracting a main area of the fingerprint; and carrying out normalized gray value limitation on the regional fingerprint image, separating foreground color and background color, enhancing fingerprint lines along the ridge line direction, removing holes and burrs in the fingerprint, and thinning the lines and outputting the 2D fingerprint image.

The non-contact fingerprint acquisition device in this application shoots the output and is 2D fingerprint image, has pressed close to the authenticity that roll formula fingerprint was gathered, and further, can adopt the method of software to refine the 2D fingerprint image of gathering, improves the quality of fingerprint image.

In summary, the non-contact fingerprint acquisition device for rotational shooting provided by the application scans and shoots fingerprints in all directions by the linear array camera rotating around the fingerprint surface, so that the problems of image splicing and humming caused by a large amount of post software processing and adjustment after shooting by a plurality of area array cameras or 3D depth cameras and large difference between images and real objects are avoided, a 2D fingerprint image of the finger fingerprint surface can be directly obtained, higher image quality is obtained, and a fingerprint image with a larger area is obtained; the method is closer to the rolling fingerprint acquisition method in the GA standard by keeping the finger still and rotating the linear array camera to shoot the fingerprint, so that the problem that the fingerprint image obtained by algorithm modeling is greatly different from the fingerprint image obtained by rolling fingerprint acquisition is solved, the authenticity and the effectiveness of the fingerprint are ensured, and the fingerprint quality required by the GA standard is achieved;

in addition, a preset angle is preset between the plane of the lens of the linear array camera and the axis direction of the finger and the lens inclines towards the fingertip, so that the grains of the fingertip of the finger can be considered in the rotating shooting process of the linear array camera, a fingerprint image with a larger area can be obtained, and the scanned fingerprint image is more complete;

in addition, by arranging the annular finger sleeves with different sizes, the outer ring of each annular finger sleeve is matched with the finger placement mechanism, and the inner ring of each annular finger sleeve is suitable for finger sizes with different thicknesses, so that the different finger sizes can be kept fixed on the finger placement mechanism, the fingers are prevented from moving in the acquisition process, and the image quality of fingerprint acquisition is ensured;

in addition, the finger back is fixed through the sucker device, so that the fixation of the finger can be further kept, and the image quality of fingerprint collection is ensured.

The terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying a number of the indicated technical features. Thus, a defined feature of "first", "second", may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless otherwise specified.

The above-mentioned serial numbers of the embodiments of the present application are merely for description and do not represent the merits of the embodiments.

The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.