Patent Application
20140071328
Embodiments relate to an imaging system and, more particularly, to a system and method to match an illuminated light at an equal aspect ratio as an illumination device and a size of a field of view of an imaging device on a target,
Light is required to illuminate a subject or target so that an imaging device, which may comprise a camera to photograph or take an image of the subject or target. A portion of a target that the imaging device photographs is within a field of view of the imaging device where the field of view is determined by a lens of the imaging device and a size or shape of an image collection sensor in the imaging device.
A light illuminating the target often over-fills the target since light reaches beyond the boundary established by the lens and sensor of the imaging device. Such over-filling can result in errant light bouncing back from, or reflecting from the surface and interfering with an image being captured.
Certain applications of imaging devices would benefit from an approach where the light illumination is narrowly focused, such as to approximately a same, or equal, size as an aspect angle of the imaging device. One such application is when an imaging device is used to optically lift a latent print or contaminant.
A latent print may be an invisible fingerprint impression, footprint impression, or palm print impression left on a surface following surface contact caused by the perspiration on ridges of an individual's skin coming in contact with the surface and leaving perspiration, sebum, waxes, oils, etc. behind, making an invisible or a partially visible impression on the surface as a result. Perspiration is known to contain water, salt, amino acids, and oils, which allows impressions to be made. The natural oils of the body preserve the print, where the impression left is utterly distinct so that no two humans have the same latent print.
Conventional methods for extracting fingerprints usually involve adding chemicals or powders to the print. Such conventional methods can present an immediate dilemma in that they force the investigator to make a decision as to whether to dust for prints versus swabbing for deoxyribonucleic acid (“DNA”) evidence. Either approach results in destroying, or removing, the prints as they are originally found since the prints are no longer on their original surface.
Automatic non-contact latent fingerprint detection systems are also known that avoid the need to add chemicals or powders that can disturb the surface chemicals of the fingerprint. Such systems generally include a single light source, utilize only diffuse reflectance (reject specular reflection (glare)) and some may even use specular reflection, and are generally limited to fingerprinting the area of one's finger, or an area about that size.
When clarity of an image is important, entities would benefit from a system and method where errant light does not interfere with an image capture.
Embodiments relate to a system and method for providing a equal aspect ratio for an imaging device and an illumination device upon a target and an equal size of a field of view of the imaging device on the target and a size of the illumination on the target. The system comprises an imaging device configured to capture an image of a target at a first aspect ratio and with a first field of view on the target. The system also comprises a light source configured to illuminate the target with a light at a second aspect ratio and with a second field of view on the target. The system also comprises at least one optical baffle configured to shape the light at the target. The second aspect ratio equals the first aspect ratio and the second field of view equals the first field of view.
A method comprises shaping an illumination aspect ratio of a light emitted from a light source to equal an aspect ratio of an imaging device at a target with at least one optical baffle. The method also comprises shaping a size of a field of view of the light emitted at the target to equal a field of view of the imaging device on the target. The method also comprises capturing an image of the target with the imaging device.
Another method comprises illuminating a target with an illumination source, and directing a path of the illumination to the target with at least one optical baffle. The method also comprises shaping an illumination aspect ratio of the illumination to equal an aspect ratio of an imaging device at a target with at least one optical baffle. The method also comprises shaping a size of a field of view of the illumination to equal a field of view of the imaging device on the target. The method also comprises capturing an image of the target with the imaging device.
A more particular description briefly stated above will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments and are not therefore to be considered to be limiting of its scope, the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
Embodiments are described herein with reference to the attached figures, wherein like reference numerals are used throughout the figures to designate similar or equivalent elements. The figures are not drawn to scale and they are provided merely to illustrate aspects disclosed herein. Several disclosed aspects are described below with reference to non-limiting example applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the embodiments disclosed herein. One having ordinary skill in the relevant art, however, will readily recognize that the disclosed embodiments can be practiced without one or more of the specific details or with other methods. In other instances, well-known structures or operations are not shown in detail to avoid obscuring aspects disclosed herein. The embodiments are not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required. to implement a methodology in accordance with the embodiments.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope are approximations, the numerical values set forth in specific non-limiting examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein. For example, a range of “less than 10” can include any and all sub-ranges between (and including) the minimum value of zero and the maximum value of 10, that is, any and all sub-ranges having a minimum value of equal to or greater than zero and a maximum value of equal to or less than 10, e.g., 1 to 4.
Though embodiments are disclosed with respect to imaging a latent fingerprint, embodiments are also applicable to other latent markings or prints as well, such as, but not limited to, a footprint a palm print, etc. As used herein, “latent print” comprises a latent fingerprint and other imprints that may be recognizable to distinguish an entity from another. Latent fingerprints, which are impressions left by the friction ridges of a human finger, may be composed of almost any material, including, but not limited to, grease, oil, sweat, wax, etc. “Latent” as used with respect to fingerprints and/or other prints means a chance or accidental impression left on a surface, regardless of whether visible or invisible at time of deposition. Embodiments are also application to other surface contaminants as well. The term “contaminant” is not limited as it can also apply to a latent print as well. Other non-limiting examples of a contaminant may include blood or another body fluid, non-bodily fluids, oils, greases, dusts, dirt, water residue, other particulates, a fracture in a surface, a physical defect in the surface, etc. Furthermore, as used herein as used herein, having an equal shape and/or size, with respect to aspect ratio and field of view, includes a tolerance of approximately plus or minus ten percent (+1-10%).
As further illustrated in
In addition to an inherent aspect ratio, the image sensor of the imaging device 17 may have an inherent number of pixels. For a fixed lens magnification, the resolution of the imaging device 17 may be based on the number of sensor pixels, divided by an adjustable size of the image sensor. Thus, if the size of the image sensor is increased, the resolution is decreased, and if the size of the image sensor is decreased, while keeping the number of pixels constant, the resolution is increased. A preferred image resolution for a latent print or a surface contamination is approximately one thousand (1000) pixels per inch in both a vertical and horizontal direction, Which are about one million pixels per square inch. Thus, a number of pixels on the image sensor divided by one million is equal to a number of square inches of target space that may be photographed at a time. As another non-limiting example, another approach to increase resolution is to increase a number of pixels while keeping a size of the image sensor constant.
During use of the system 10, a minimum required resolution of an image of the target 14 is first determined, along with a required size and aspect ratio of the image. For example, if the target 14 is a latent fingerprint, the minimum required resolution is 1 million pixels per square inch, the required size of the target image is 1 square inch and the required aspect ratio is 1:1. The camera 13 and lens 15, or the imaging device 17, are then selected, based on the inherent number of pixels in the camera 13, and magnification of the lens 15, and whether the resolution is at least equal to a minimum required resolution, when the image sensor size is adjusted to the size of the target. As a non-limiting example, a camera with 5 million pixels and lens with a magnification of one (1) could be used to image the latent fingerprint since the camera would have a resolution of 5 million pixels per square inch (greater than the minimum required resolution), when the image sensor size is adjusted to the required image size of 1 square inch. The light source 12 is then selected, along with the optical baffles 24,25,27,29, such that the illumination aspect ratio of the light 11 on the target 14 is equal to the image sensor aspect ratio of the imaging device 17. They are also selected so that the light pattern on the target 14 should also an equal size, +/−10%, as the imaging device's field of view on the target. Though the above non-limiting example discusses selecting a camera 13 and lens 15, the camera 13 or lens 15 may be capable of simply being adjusted as oppose to selecting a specific camera and lens.
The method may further comprise adjusting the aspect ratio of the imaging device at the target with a lens to equal an aspect ratio of an image sensor of the imaging device, at 840. The method may further comprise limiting a high diverging portion of the light emitted from reaching the target while permitting a low diverging portion of the light to be illuminated to propagate from the light source to the target with the at least one optical baffle, at 850. The method may further comprise adjusting an opening through the at least one optical baffle with a lens, at 860. The method may further comprise reducing multiple directions of the light emitted from the light source with a reflector, at 870. The method may further comprise filtering a light spectrum of the light emitted through the at least one optical baffle with at least one spectral filter, at 880.
FIG, 9 shows a flowchart illustrating an embodiment of a method. The method 900 illuminating a target with an illumination source, at 910. The method also comprises directing a path of the illumination to the target with at least one optical baffle, at 920. The method 900 further comprises shaping an illumination aspect ratio of the illumination to equal an aspect ratio of an imaging device at a target with at least one optical baffle, at 930. The method further comprises shaping a size of a field of view of the illumination to equal a field of view of the imaging device on the target, at 940. The method further comprises capturing an image of the target with the imaging device, at 950.
The method further comprises adjusting the aspect ratio at the target of the imaging device with a lens, at 960. The method also comprises limiting a high diverging portion of the illumination from reaching the target while permitting a low diverging portion of the illumination to reach the target with the at least one optical baffle, at 970. The method further comprising adjusting an opening through the at least one optical baffle with a lens, at 980. The method further comprising reducing multiple directions of the illumination with a reflector, at 990. The method further comprising filtering a light spectrum of the illumination through the at least one optical baffle with at least one spectral filter, at 995.
Though the steps illustrated in the flowchart of the methods and provided in a particular sequence, these sequences are not meant to be limiting as those skilled in the art will recognize that these steps may be performed in any particular order. Based on the disclosure above, the system and methods may be used to ensure that light is most efficiently utilized to where a smaller, such as, but not limited to, where smaller means less illumination is available, light source may be used.
While various disclosed embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Numerous changes to the subject matter disclosed herein can be made in accordance with the embodiments disclosed herein without departing from the spirit or scope of the embodiments. In addition, while a particular feature may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application.
Therefore, the breadth and scope of the subject matter provided herein should not be limited by any of the above explicitly described embodiments. Rather, the scope of the embodiments should be defined in accordance with the following claims and their equivalents.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and/or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” Moreover, unless specifically stated, any use of the terms first, second., etc., does not denote any order or importance, but rather the terms first, second, etc., are used to distinguish one element from another.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Thus, while embodiments have been described with reference to various embodiments, it will be understood by those skilled in the art that various changes, omissions and/or additions may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the embodiments. in addition, many modifications may be made to adapt a particular situation or material to the teachings of the embodiments without departing from the scope thereof. Therefore, it is intended that the embodiments not be limited to the particular embodiment disclosed as the best mode contemplated, but that all embodiments falling within the scope of the appended claims are considered.
This application claims the benefit of U.S. Provisional Application No. 61/697,895 filed Sep. 7, 2012, and incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61697895 | Sep 2012 | US |
