Image artifact mitigation in scanners for entry control systems

A method for imaging includes illuminating a vehicle undercarriage with illumination in an atmospheric absorption band, imaging the vehicle undercarriage to form an image, wherein scanning includes filtering out illumination returned from the vehicle undercarriage that is outside the atmospheric absorption band. The method includes forming an image with the filtered illumination returned from the vehicle undercarriage.

BACKGROUND

The present disclosure relates to imaging, and more particularly to scanners for entry control systems, such as under car scanners for security check points.

2. Description of Related Art

Several technologies exist which can scan the underside of motor vehicles. Many of these technologies rely on the ability to link a vehicle with a vehicle identifier (e.g., license plate number, radio frequency identification (RFID) tag, etc.) so as to be able to perform an automated search of the underside. Other technologies produce only a single image requiring manual inspection of the vehicle image on a screen. One issue that arises is artifacts in the images, wherein areas within a given image have lower image quality. Such artifacts can interfere with software performing analysis on the images, e.g., giving rise to false positives on potential security issues, and can even hamper manual inspection of the vehicle images on screen.

The conventional techniques have been considered satisfactory for their intended purpose. However, there is an ever present need for improved systems and methods for imaging systems and methods. This disclosure provides a solution for this need.

SUMMARY

A scanner system includes a scanner framework having a front end, a back end and a top surface. A scanner camera is operatively connected to the scanner framework and has a lens and a sensor for recording images captured from a field of view of the camera. A first mirror arrangement is secured to the framework so as to provide a first reflecting surface angled upwardly toward the top surface and toward the framework front end for imaging a second portion of the field of view. A second mirror arrangement is secured to the framework so as to provide a second reflecting surface angled upwardly in a direction facing the framework top surface and the framework back end for imaging a first portion of the field of view. An illuminator is operatively connected to the camera to illuminate the first and second portions of the field of view. A band pass filter is operatively connected to the scanner camera to filter out illumination outside of an atmospheric absorption band, wherein the sensor is sensitive to illumination in the atmospheric absorption band.

The filter can be configured to pass illumination within plus or minus 60 nm of at least one atmospheric absorption band selected from the list consisting of 780 nm, 940 nm, 1120 nm, 1400 nm, and 1900 nm. The filter can be configured to pass illumination within plus or minus 50 nm of at least one atmospheric absorption band selected from the list consisting of 780 nm, 940 nm, 1120 nm, 1400 nm, and 1900 nm. The illuminator can be configured to illuminate a scene with illumination in the at least one atmospheric absorption band selected from the list consisting of 780 nm, 940 nm, 1120 nm, 1400 nm, and 1900 nm. The sensor can include at least one of Germanium sensitive to plus or minus 50 nm of 1120 nanometers, InGaAs sensitive to plus or minus 50 nm of 780 nm to 1900 nm, and/or HgCdTe (Mercury Cadmium Telurride or Mercadetelluride). The illuminator can be an LED or laser based illuminator that emits 940 nm illumination, wherein the filter is configured to pass illumination within plus or minus 50 nm of 940 nm, and wherein the sensor is a silicon based sensor sensitive to illumination within plus or minus 50 nm of 940 nm.

The scanner camera can be secured to the framework such that the lens faces the framework front end. The first mirror arrangement can include a mirror mounted at or near the framework front end. The second mirror arrangement can include a primary mirror mounted at or near the framework back end, and a secondary mirror mounted at or near a location between the framework front and back ends. The scanner camera can be secured to the framework such that a portion of the lens faces the first mirror arrangement and a portion of the lens faces the second mirror arrangement. The first mirror arrangement can includes a mirror mounted at or near the framework front end and the second mirror arrangement can include a primary mirror mounted at or near the framework back end and a secondary mirror mounted at or near a location between the framework front and back ends.

The scanner camera can be secured such that the camera lens is angled downwardly away from the framework top surface. The scanner camera can be secured to the framework such that the lens faces the framework back end. The framework can include a first glass member secured between the framework top surface and front end, and a second glass member secured between the framework top surface and back end. The first reflecting surface can be angled toward the first glass member and the second reflecting surface can be angled toward the second glass member. The camera can be provided with a single board computer (SBC) in two-way communication with a remote computer monitoring system.

A method for imaging includes illuminating a vehicle undercarriage with illumination in an atmospheric absorption band, imaging the vehicle undercarriage to form an image, wherein scanning includes filtering out illumination returned from the vehicle undercarriage that is outside the atmospheric absorption band. The method includes forming an image with the filtered illumination returned from the vehicle undercarriage.

Illuminating can include illuminating the undercarriage with illumination that includes at least one atmospheric absorption band selected from the list consisting of 780 nm, 940 nm, 1120 nm, 1400 nm, and 1900 nm. Filtering out illumination can include filtering out illumination that is not within plus or minus 50 nm of at least one band selected from the list consisting of 780 nm, 940 nm, 1120 nm, 1400 nm, and 1900 nm. The illuminator can be an LED or laser based illuminator that emits at least one of 780 nm and/or 940 nm illumination, and wherein the filter is configured to pass illumination within plus or minus 50 nm of at least one of 780 nm and/or 940 nm, and wherein the sensor is a silicon based sensor sensitive to illumination within plus or minus 50 nm of at least one of 780 nm and/or 940 nm.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an embodiment of a system in accordance with the disclosure is shown inFIG. 1and is designated generally by reference character54. Other embodiments of systems in accordance with the disclosure, or aspects thereof, are provided inFIGS. 2-6, as will be described. The systems and methods described herein can be used to improve image quality by removing imaging artifacts, e.g. artifacts imposed by the sun in the background of an undercarriage image.

As shown inFIGS. 1-2, the mobile platform100includes the following elements: a pair of platform runners50, two cross members52connecting between the platform runners, a scanner system54between the two cross members52, a proximity sensor55operatively connected to trigger under vehicle scanning by the scanner system54, and a front camera (not shown). The platform runners50and cross members52may not be required, as the scanner system54can be embedded in the ground underneath any vehicle which may pass over. In the mobile platform as shown inFIGS. 1-2, the scanner system54is positioned between the two platform runners50and is maintained so as to avoid vibration and other negative consequences. The platform runners50can have lead on and off ramps57for ramping a vehicle on an off of the platform runners50. On the leading edge of one of the runners (e.g., the right hand runner), a proximity sensor55can be provided. The sensor is activated by a pressure switch contained within a thick rubber strip, similar to those used at car washes, for example. Guide rails58can also be provided to keep the vehicle profile as consistent as possible. It will be appreciated that the runners will be maintained in substantially parallel condition to facilitate vehicles passing over them. The two cross members52assist in this process by linking the two runners50together by interlocking connections, in one embodiment. Additional details about the mobile platform are in U.S. Pat. No. 7,349,007 which is incorporated by reference herein in its entirety.

With reference now toFIG. 3, the scanner system54includes a housing or framework60having a front end62, a back end64, a top surface66, and openings68created between the top edge65of the front67and back69end walls and the respective side edges71,72of the top surface66. An ambient heat shield (AHS)70absorbs the direct heat from the sun and can be positioned above the top cover of the scanner, for example.

Two windows73,74can be securely positioned between the top surface66and the end walls67,69in order to cover the respective openings while maintaining visibility therethrough. The windows73,74are secured at respective angles A and B to the horizontal. The first window73is positioned to face forward (i.e., in the direction of travel of the overriding vehicle) and the second window74is positioned to face backward (i.e., against the direction of travel of the overriding vehicle) to assist in capturing two simultaneous views of the vehicle. The direction of travel of a given vehicle is indicated by arrow C inFIG. 3.

The scanner system54includes a camera75and first76and second77internal mirror arrangements, which can be angled such that internal mirrors82and84face out through the anti-reflective, anti-glare, water-repellant glass members of the windows73,74. The camera75can be a Basler A602f wide area scan camera manufactured by Basler Vision Technology of Ahrensburg, Germany, capable of recording digital video images at a rate of at least 200 frames per second. The camera is provided with a lens78mounted thereto. The scanner camera75is secured in a position that faces the direction C of oncoming travel of a vehicle. The camera75is secured such that the lens78faces at an angle downwardly away from the framework top surface66such that the camera75is appropriately positioned to capture images reflected off of the first76and second77mirror arrangements. It is contemplated that the camera75can be oriented such that its lens faces either the front end or the back end of the framework.

As further shown inFIG. 3, the first mirror arrangement indicated at76can be secured to the framework so as to provide a first reflecting surface angled upwardly toward the framework top surface66and toward the framework front end62. The positioning of the first mirror arrangement enables the camera to record images reflected by the first mirror82as they appear on the other side of window member73. The first mirror arrangement includes a first mirror secured at or near the scanner framework front end.

In a similar manner, the second mirror arrangement, indicated at77, can be secured to the framework so as to provide a second reflecting surface angled upwardly in a direction facing the framework top surface66and the framework back end64. The positioning of the second mirror arrangement77enables the camera75to record images reflected by the second mirror arrangement as they appear on the other side of window member74. The second mirror arrangement77can include a larger primary mirror84mounted at or near the framework back end64and a smaller secondary mirror86mounted at a location87in between the front62and back64ends of the scanner framework. The primary mirror84of the second mirror arrangement77is secured inside the back wall64of the framework and underneath the back window member74. The secondary mirror86of the second mirror arrangement77can be positioned roughly halfway between the scanner framework front62and end64walls, and can be secured in a substantially perpendicular relation to the framework bottom floor61. The mirror82can be secured at an angle D of between approximately 20 and 30 degrees from the horizontal, and mirror84is secured at an angle E of between approximately 25 and 35 degrees from the horizontal.

The scanner system54including the camera75and first and second mirror arrangements76,77allows the scanner system54to operate such that the camera75can detect multiple images from an overriding vehicle at the same time. The top half of the camera lens looks over the small mirror86on to the front mirror82. The bottom half of the camera lens looks onto the small mirror86that captures the view reflected by the back main mirror84. A first view is taken of the vehicle as it approaches wall69as shown by the dashed lines92. In this view, the camera is recording the image of the vehicle as reflected by the back mirror84at the back end of the scanner framework looking toward the back of the vehicle via the smaller mirror86. A second view is simultaneously recorded by the camera as it is reflected from the first mirror arrangement as indicated in dashed lines at90.

An illuminator95, which includes an upward facing laser or LED bank on either side end of the scanner system54, is operatively connected to the camera95to illuminate the first and second portions of the field of view. A band pass filter96is operatively connected to the scanner camera75to filter out illumination outside of an atmospheric absorption band, wherein the sensor97of the camera75is sensitive to illumination in the atmospheric absorption band. The filter96can be located outside of the lens78as shown, or it can be mounted between the lens78and the camera75inside the interface between the lens78and camera75.

The filter96can be configured to pass illumination within plus or minus 50 or 60 nm of at least one atmospheric absorption band such as 780 nm, 940 nm, 1120 nm, 1400 nm, and 1900 nm. The illuminator95can be configured to illuminate the scene in the field of view with illumination in the at least one atmospheric absorption band such as 780 nm, 940 nm, 1120 nm, 1400 nm, and 1900 nm. Those skilled in the art will readily appreciate that there can be advantages to systems that use even smaller bandwidth spectral filters. For example, a system54may be able to reject even more of the solar irradiance transmitted through the atmosphere by implementing a bandpass filter as low as plus or minus 5 nm. This approach would typically require laser illumination which has a smaller spectral bandwidth than 5 nm making for an efficient system that will collect most of the laser illumination through that small spectral band. Implementing an LED solution which has tradeoffs. LEDs have a larger spectral bandwidth typically above 30 nm, and therefore a filter of larger than 30 nm is needed to make sure the system54captures all of the LED illumination efficiently. If a spectral filter of plus or minus 5 nm bandpass is used with LEDs, most of the light from the LEDs would be rejected by the filter. In appropriate applications, it may be desirable to implement a laser based solution with a smaller spectral bandwidth filter since there are some atmosphere absorption bands that are thinner than the 50 or 60 nm.

The sensor97can include at least one of Germanium sensitive to plus or minus 50 nm of 1120 nanometers (Germanium can be sensitive to the wavelengths of 700 nm to about 1600 nm. It is not typically sensitive up to 1900 nm.), InGaAs sensitive to plus or minus 50 nm of 780 nm to 1900 nm, and/or HgCdTe (Mercury Cadmium Telurride or Mercadetelluride). It is contemplated that the illuminator95can be an LED or laser based illuminator that emits 940 nm illumination, wherein the filter96is configured to pass illumination within plus or minus 50 nm of 940 nm, and wherein the sensor97is a silicon based sensor sensitive to illumination within plus or minus 50 nm of 940 nm. Those skilled in the art having the benefit of this disclosure will readily appreciate that the bandwidths described in this paragraph can be tailored larger or smaller as suitable for a specific application, e.g. as explained in the previous paragraph, and to account for manufacturing tolerances in illuminators or the like.

With reference now toFIG. 4, the camera75can be provided with a single board computer (SBC)98in two-way communication with a remote computer monitoring system. This can be implemented as part of an entry control system, including an entry control platform and scanner device as described above (shown generally at10) and a computer/monitor element15. Computer and monitor15can access a database20, which can be locally stored on the computer15or accessible via a network. Computer15can also be connected to a wide area network25such as the Internet, for example, in order to access a different database30. This database30can be used to store and update reference images for vehicles of all types, and may be used to update local database20. Reference images can be “stock” images of vehicle undersides made available by vehicle manufacturers, dealers or service providers, for example. It is also contemplated that reference images can be images created using the systems disclosed herein. It will be appreciated that the effectiveness of the scanner system54can be increased when using reference images created using the systems as disclosed herein, due to the increased accuracy and comprehensive detail available.

A separate computer35is shown, which may be a remote computer not located near the physical entry control deployment elements10. Thus, communications from the scanner system54can be used while being operated either locally at computer15or remotely at computer35. It will be appreciated that computer and monitor15may be considered remote even when located at the implementation site, since they may be connected to elements10via Ethernet or fiber cabling12, for example, or via wireless communication.

A method for can include illuminating a vehicle undercarriage with illumination in an atmospheric absorption band, imaging the vehicle undercarriage to form an image, wherein scanning includes filtering out illumination returned from the vehicle undercarriage that is outside the atmospheric absorption band. The method includes forming an image with the filtered illumination returned from the vehicle undercarriage.

Illuminating can include illuminating the undercarriage with illumination that includes at least one atmospheric absorption band selected from the list consisting of 780 nm, 940 nm, 1120 nm, 1400 nm, and 1900 nm. Filtering out illumination can include filtering out illumination that is not within plus or minus 50 nm of at least one band selected from the list consisting of 780 nm, 940 nm, 1120 nm, 1400 nm, and 1900 nm (or other suitable bandwidths as described above).FIG. 6shows an under carriage image200formed without the benefits of systems and methods disclosed herein. The artifacts202are a result of the sun shining in to the scanner system during the scanning process.FIG. 5shows an undercarriage image300as obtained with systems and methods disclosed herein. The artifacts202are eliminated, even if the sun shines into the scanner system54during the scanning process.

The methods and systems of the present disclosure, as described above and shown in the drawings, provide for reduction or even elimination of certain artifacts in vehicle undercarriage imagery. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.