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Axis : Patent Application Titled "Camera and Method of Producing Color Images" Published Online (USPTO 20180184054)

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07/12/2018 | 09:11 pm

By a News Reporter-Staff News Editor at Computer Weekly News -- According to news reporting originating from Washington, D.C., by VerticalNews journalists, a patent application by the inventors Lundberg, Stefan (Lund, SE); Hjelmstrom, Jonas (Lund, SE), filed on December 28, 2017, was made available online on July 5, 2018.

The assignee for this patent application is Axis AB.

Reporters obtained the following quote from the background information supplied by the inventors: "Image sensors used in digital cameras have a spectral response with a non-negligible component in the infrared (IR). This results in opportunities as well as challenges.

"An opportunity lies in that during night time, or in low-light conditions the IR-component may provide useful information about the imaged scene. Typically, low light conditions occur during dusk or dawn. Other low light condition scenes are badly lit rooms. Low-light condition may also be defined as conditions where the amount of visible light and IR-radiation are comparable, hence, low-light condition may also be referred to as a mixed light condition.

"During night time, or in low-light conditions use may be made of incoming radiation from the IR portion of the spectrum. The IR radiation will not contain any color information, and instead of performing a color separation, the only parameter is the intensity of the incoming radiation, which may be presented as a black and white intensity image (or with any desirable color scale).

"A challenge is found during day-time imaging, where the addition of an IR-component may distort the color balance in images captured using a digital camera. In some situations, some or all pixels of the image sensor may even be completely saturated by the infrared component.

"A way of maintaining the beneficial effects while suppressing the less beneficial effects is to add a movable IR-cut filter in the beam path in front of the image sensor. In this way, the IR-cut filter may be used during daylight conditions, enabling acquisition of color images. Pixels of the image sensor will then operate in a first manner, where the incident light is divided into colors and detected as a charge on individual photodetectors thus enabling color separation. The IR-cut filter will be removed during night time, or in low-light conditions allowing IR-radiation to reach the image sensor. Pixels of the image sensor will then operate in a second manner, where the only parameter measured by the pixels is the intensity of the incoming radiation. Hence, intensity based images may be captured, and presented in black and white.

"There may, however, be instances where it would be desirable to be able to capture color separated images even in low-light conditions."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventors' summary information for this patent application: "In view of the above, it is an object of the disclosure to provide means for capturing color separated images even in low-light conditions.

"According to a first aspect, a camera is provided. The camera comprises: an aperture; an image sensor comprising a plurality of pairs of pixels in which pair: a first pixel is configured such that it detects radiation which has entered the camera through the aperture and traveled from the aperture to the image sensor via a first radiation path, and a second pixel is configured such that it detects radiation which has entered the camera through the aperture and traveled from the aperture to the image sensor via a second radiation path, the second radiation path being different from the first radiation path; and a filter arranged in, or in the vicinity of, the aperture, wherein the filter comprises a first portion configured to block IR-radiation or visible light and a second portion configured to be transparent to wavelengths that are blocked by the first portion, wherein the filter is arranged such that radiation passing the first portion travels to the first pixels of the plurality of pairs of pixels, and such that radiation passing the second portion travels to the second pixels of the plurality of pairs of pixels.

"Hence, improved imaging is enabled. This is due to components of IR-radiation may be determined by comparing radiation detected by the first and second pixels in each pair of first and second pixels, and compensating for that IR portion. For example, a color image may be produced by determining the IR-portion of radiation detected by the image sensor. In this way, a true color representation may be obtained, even though the imaged scene contains IR-radiation which is captured by the image sensor.

"The term 'radiation' is to be construed as radiation comprising spectral components both in the infrared spectral range and in the visible light spectral range.

"The first portion of the filter may be configured to block IR-radiation. The first portion of the filter may be configured to block visible light.

"The second portion of the filter may be configured to be transparent to both IR-radiation and visible light.

"The first portion of the filter may be configured to block IR-radiation and the second portion of the filter may be configured to block visible light.

"The filter may be fixedly positioned in, or in the vicinity of, the aperture. A simple camera with very few movable parts may thus be provided. The filter does not have to be (often cannot be) exactly in the aperture plane, but as long as it is close enough, it does not matter which side of the aperture it is.

"The filter has to be close to the aperture. It does not have to be (often cannot be) exactly in the aperture plane, but as long as it is close enough, it does not matter which side of the aperture it is.

"The filter may movable such that it may be positioned in and retracted from the first and second radiation paths. Thus, it will be possible to put the camera in different modes, such as a day mode wherein the filter with the first and second portions are used for calculating a proportion of IR-radiation in the scene based on an amount of radiation detected by each of the first and second pixels of the plurality of pairs of pixels and a night mode wherein the filter is removed, and the full spectral response of the image sensor is used for producing black and white images.

"The filter is useful when the scene comprises both visible light and IR-radiation. In these situations, it is possible to compensate for the IR-radiation and get good color fidelity. This is particularly useful in mixed light (low light, such as at dusk and dawn), where in implementation of today a switch to only registering the amount of radiation removing the IR cut filter is used. This is needed when the visible light level gets too low. In day light or good light, the IR-radiation is not needed, because there is plenty of visible light. However, the camera set up according to the present teachings makes it possible to compensate for the IR-radiation. In traditional monitoring cameras, this is when the IR cut filter is inserted.

"At night, or in other really low light, there is basically no visible light, and at least a lot more IR radiation than visual light, so it will be very hard to produce color images. Thus, the filter might be removed at night. This so that as much radiation as possible is reaching the image sensor (by not blocking any IR-radiation). This switch to night mode may be postponed to lower light levels using the present teachings.

"The portioning of the filter may be aligned with the first and second pixels such that: IR-radiation will not reach the first pixels in the pair of pixels, and IR-radiation will reach the second pixels in the pair of pixels.

"Each pixel of the image sensor may belong to a respective pair of pixels.

"The image sensor may be configured to, upon the camera being exposed to radiation comprising both visible light and IR-radiation, register a value indicative of an amount of radiation reaching each of the plurality of pairs of pixels. The camera may further comprise a processing unit configured to: determine, for each of the first pixels of the plurality of pairs of pixels, a value indicative of a first amount of radiation detected by the respective first pixel, determine, for each of the second pixels of the plurality of pairs of pixels, a value indicative of a second amount of radiation detected by the respective second pixel, calculate a proportion of IR-radiation in the scene based on the first and second amount of radiation determined for each of the first and second pixels of the plurality of pairs of pixels, and produce a color image of the scene by compensating for an IR-contribution in an image captured by the camera based on the calculated proportion of IR-radiation.

"According to a second aspect, a method of producing a color image of a scene captured by a camera exposed to radiation comprising both visible light and IR-radiation is provided. The method comprises: detecting a value indicative of an amount of radiation in each of a plurality of pairs of pixels, wherein each pair comprises a first pixel and a second pixel, determining, for each of the first pixels of the plurality of pairs of pixels, a value indicative of a first amount of radiation detected by the respective first pixel, determining for each of the second pixels of the plurality of pairs of pixels a value indicative of a second amount of radiation detected by the respective second pixel, calculating a proportion of IR-radiation in the scene based on the first and second amount of radiation determined for each of the first and second pixels of the plurality of pairs of pixels, and producing the color image of the scene by compensating for an IR-contribution in an image captured by the camera based on the calculated proportion of IR-radiation.

"The method may further comprise blocking IR-radiation or visible light from reaching the first pixels of the plurality of pairs of pixels, and allowing wavelengths that are blocked from reaching the first pixels of the plurality of pairs of pixels to reach the second pixels of the plurality of pairs of pixels.

"The above mentioned features of the camera, when applicable, apply to this second aspect as well. In order to avoid undue repetition, reference is made to the above.

"According to a third aspect, a non-transitory computer readable storage medium is provided. The non-transitory computer readable storage medium has computer readable program code stored thereon which when executed on a device having processing capability is configured to perform the method according to the second aspect.

"A further scope of applicability of the present teachings will become apparent from the detailed description given below. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments, are given by way of illustration only, since various changes and modifications within the scope of the disclosure will become apparent to those skilled in the art from this detailed description.

"Hence, it is to be understood that this disclosure is not limited to the particular component parts of the device described or steps of the methods described as such device and method may vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It must be noted that, as used in the specification and the appended claim, the articles 'a,' 'an,' 'the,' and 'said' are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise. Thus, for example, reference to 'a unit' or 'the unit' may include several devices, and the like. Furthermore, the words 'comprising', 'including', 'containing' and similar wordings does not exclude other elements or steps."

For more information, see this patent application: Lundberg, Stefan; Hjelmstrom, Jonas. Camera and Method of Producing Color Images. Filed December 28, 2017 and posted July 5, 2018. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.html&r=1&f=G&l=50&s1=%2220180184054%22.PGNR.&OS=DN/20180184054&RS=DN/20180184054

Keywords for this news article include: Axis AB, Business, Computers.

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