Determining specular reflection information

Abstract

A computer-implemented method 100 is described. The computer-implemented method includes receiving 102 first and second imaging data acquired by an imaging system 204 of a subject 202 illuminated by a first illumination 206a in a first spectral band and a second illumination 206b in a second spectral band with a different spectral content than the first spectral band. The second illumination incident on the subject is polarized. The received first imaging data is acquired in the first spectral band. The received second imaging data is acquired in the second spectral band. Depending on the polarization state of the reflected first and second illumination received by the imaging system after reflection from the subject's surface, the first and second illumination are entered into the imaging system via an imaging system polarizer 310 of the imaging system. Information about the specular reflection from the subject's surface is determined by comparing the first and second imaging data.

Description

[Technical Field]

[0001] The present invention relates to a method, a tangible machine-readable medium and an apparatus for use in imaging in certain conditions. [Background technology]

[0002] A topic of interest in the field of non-intrusive measurement and monitoring relates to skin sensing for personal care and health applications. Skin sensing systems have been developed that allow for the quantification of skin and monitoring of skin characteristics that provide users with information that is too small to detect, too subtle to notice, or too slow to follow. To achieve results that are acceptable to users, such skin sensing systems must provide sensitivity and specificity in performing skin sensing. Users establish trust in these skin sensing systems when the measurements taken by such systems are proven to be robust and reliable. Summary of the Invention [Problem to be solved by the invention]

[0003] Imaging-based skin sensing systems implement various imaging techniques to determine certain information about a user's skin. Such information includes parameters such as the radiance of the user's skin. Certain systems for determining radiance are expensive, complex, and / or bulky. [Means for solving the problem]

[0004] Aspects or embodiments described herein relate to determining certain information, such as the shininess of a subject's surface, and avoid one or more problems associated with the cost, complexity, and / or bulkiness of systems for determining such information.

[0005] In a first aspect, a method is described. The method is a computer-implemented method. The computer-implemented method includes receiving first and second imaging data acquired by an imaging system of a subject illuminated by first illumination in a first spectral band and second illumination in a second spectral band having a different spectral content than the first spectral band. The second illumination incident on the subject is polarized.

[0006] The received first imaging data is acquired within a first spectral band as a result of a first color filter of the imaging system allowing at least a portion of the first spectral band to enter the imaging system and preventing at least a portion of the second spectral band from entering the imaging system, such that a majority of the intensity information in the first imaging data acquired within the first spectral band is derived from the first illumination.

[0007] The received second imaging data is acquired within a second spectral band as a result of a second color filter of the imaging system allowing at least a portion of the second spectral band to enter the imaging system and preventing at least a portion of the first spectral band from entering the imaging system, such that a majority of the intensity information in the second imaging data acquired within the second spectral band is derived from the second illumination.

[0008] The first and second illuminations are incident on the imaging system via an imaging system polarizer of the imaging system, depending on the polarization states of the reflected first and second illuminations received by the imaging system after reflection from the subject's surface, such that specularly reflected and diffusely reflected first illumination is incident on the imaging system and diffusely reflected second illumination is incident on the imaging system.

[0009] The computer-implemented method further includes determining information about specular reflection from a surface of the subject by comparing the first imaging data and the second imaging data.

[0010] Some embodiments relating to the first aspect are described below.

[0011] In some embodiments, the time frame during which the first imaging data is acquired at least partially overlaps with the time frame during which the second imaging data is acquired.

[0012] In some embodiments, the first and second imaging data are acquired simultaneously.

[0013] In some embodiments, the imaging system polarizer is configured to admit reflected first and second illumination having electric field components parallel to a polarization axis of the imaging system polarizer to the imaging system, and the imaging system polarizer is further configured to attenuate reflected first and second illumination having electric field components perpendicular to the polarization axis.

[0014] In some embodiments, the information about the specular reflectance is indicative of a gloss level of the subject's skin, the gloss level being determined by calculating a difference between intensity information in the first imaging data and intensity information in the second imaging data.

[0015] In some embodiments, the first and second color filters are part of a color filter array configured to enable at least one imaging device of the imaging system to acquire first imaging data in a first spectral band and second imaging data in a second spectral band. The computer-implemented method further includes extracting the first imaging data separately from the second imaging data from the raw imaging data acquired by the at least one imaging device.

[0016] In a second aspect, a tangible machine-readable medium is described that comprises instructions that, when executed by a processing circuit, cause the processing circuit to perform the method of the first aspect or any related embodiment.

[0017] In a third aspect, an apparatus is described, the apparatus comprising a processing circuit, the processing circuit comprising a receiving module and a determining module.

[0018] The receiver module is configured to receive first and second imaging data acquired by the imaging system of a subject illuminated by first illumination in a first spectral band and second illumination in a second spectral band having a different spectral content than the first spectral band, wherein the second illumination incident on the subject is polarized.

[0019] The received first imaging data is acquired within a first spectral band as a result of a first color filter of the imaging system allowing at least a portion of the first spectral band to enter the imaging system and preventing at least a portion of the second spectral band from entering the imaging system, such that a majority of the intensity information in the first imaging data acquired within the first spectral band is derived from the first illumination.

[0020] The received second imaging data is acquired within a second spectral band as a result of a second color filter of the imaging system allowing at least a portion of the second spectral band to enter the imaging system and preventing at least a portion of the first spectral band from entering the imaging system, such that a majority of the intensity information in the second imaging data acquired within the second spectral band is derived from the second illumination.

[0021] The first and second illuminations are incident on the imaging system via an imaging system polarizer of the imaging system, depending on the polarization states of the reflected first and second illuminations received by the imaging system after reflection from the subject's surface, such that specularly reflected and diffusely reflected first illumination is incident on the imaging system and diffusely reflected second illumination is incident on the imaging system.

[0022] The determination module is configured to determine information regarding specular reflection from a surface of the subject by comparing the first imaging data and the second imaging data.

[0023] Several embodiments relating to the third aspect are described below.

[0024] In some embodiments, the determination module is configured to determine a measure of skin radiance of the subject based on a comparison between the first imaging data and the second imaging data.

[0025] In some embodiments, the apparatus further comprises an imaging system and / or an illumination system configured to provide the first and second illumination.

[0026] In some embodiments, the imaging system polarizer is configured to allow reflected first and second illumination having electric field components parallel to a polarization axis of the imaging system polarizer to enter the imaging system, and the imaging system polarizer is further configured to prevent reflected first and second illumination having electric field components perpendicular to the polarization axis from entering the imaging system.

[0027] In some embodiments, the illumination system includes an illumination system polarizer configured to polarize the second illumination directed at the subject, the polarization axis of the imaging system polarizer being orthogonal to the polarization axis of the illumination system polarizer.

[0028] In some embodiments, the illumination system is configured such that the first illumination directed at the subject is unpolarized, or the illumination system comprises an additional illumination system polarizer configured to polarize the first illumination directed at the subject such that the polarization state of the first illumination directed at the subject is orthogonal to the polarization state of the second illumination directed at the subject.

[0029] In some embodiments, the illumination system is configured to direct the first and second illuminations toward the subject such that both specular and diffuse reflected components of the first and second illuminations reflected from the surface of the subject are directed into the imaging system for internal entry according to the polarization states of the reflected first and second illuminations.

[0030] In some embodiments, the imaging system comprises at least one imaging device and an optical filter array, the optical filter array comprising a first color filter and a second color filter.

[0031] The optical filter array is configured to pass at least a portion of the first spectral band into the imaging system to a first set of pixels of the at least one imaging device such that a majority of intensity information in first imaging data acquired within the first spectral band is derived from the first illumination.

[0032] The optical filter array is further configured to pass at least a portion of the second spectral band into the imaging system to a second, different set of pixels of the at least one imaging device such that a majority of the intensity information in second imaging data acquired within the second spectral band is derived from the second illumination.

[0033] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

[0034] Exemplary embodiments of the present invention will now be described, by way of example only, with reference to the following drawings: [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 illustrates a method for determining specific information about a surface of a subject according to one embodiment. [Figure 2] FIG. 1 is a schematic diagram of a system for determining specific information about a surface of a subject, according to one embodiment. [Figure 3] FIG. 1 is a schematic diagram of a system for determining specific information about a surface of a subject, according to one embodiment. [Figure 4] 4A-4C illustrate exemplary optical parameters of certain components of the system of FIG. 3. [Figure 5] 1 is a schematic diagram of a representation of a method for determining specific information about a surface of a subject according to one embodiment. [Figure 6] FIG. 1 illustrates a method for determining specific information about a surface of a subject according to one embodiment. [Figure 7] FIG. 1 is a schematic diagram of a machine-readable medium for determining specific information about a surface of a subject, according to one embodiment. [Figure 8] 1 is a schematic diagram of an apparatus for determining specific information about a surface of a subject according to one embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0036] According to skin beauty assumptions, it is desirable for skin to appear to have a natural, luminous sheen without appearing oily. Skin appearance depends on how light interacts with the skin. The level of apparent sheen depends on the underlying surface and subsurface reflections that result from light incident on the skin at various angles.

[0037] Measuring skin radiance is of interest in efficacy testing of certain skin care solutions, for example, as skin radiance is related to skin beauty and influences personal self-confidence and / or achieving a particular appearance.

[0038] When applied to the skin, skin care products such as makeup and moisturizers affect the apparent radiance of the skin. Additionally, some devices, such as skin cleansing devices, shavers, exfoliators, hydration devices, skin stimulators (e.g., mechanical, electrical, optical), or any other device that alters the appearance of the skin (e.g., for cosmetic reasons), also affect the apparent radiance of the skin. Skin care products and / or devices are used as part of a personal care regimen.

[0039] Certain personal care regimens involve characterizing skin radiance (e.g., before and / or after the personal care regimen). Users interested in characterizing their skin (e.g., to determine skin radiance) use certain embodiments described herein to determine information useful for such characterization. This information can be useful in evaluating the personal care regimen.

[0040] 1 illustrates a method 100 (e.g., a computer-implemented method) for determining certain information about a subject's surface (e.g., a user's skin). Method 100 is implemented by a computer, such as a user device or a server or cloud-based service (communicatively coupled to the user device). An example of a user device is a smart device, such as a smartphone, tablet, smart mirror, or any other device capable of processing imaging data as described below.

[0041] The method 100 includes receiving first and second imaging data at block 102 .

[0042] As described in more detail below, the first and second imaging data are acquired by an imaging system (prior to being received according to block 102 of method 100). Imaging data refers to information, such as pixel intensity information, derived from at least one image acquired by the imaging system of a subject illuminated by a first illumination and a second illumination. The first illumination is in a first spectral band and the second illumination is in a second spectral band. The second spectral band includes a different spectral content than the first spectral band. The first spectral band may or may not overlap with the second spectral band. Further details of the first and second spectral bands are described in more detail below. The second illumination incident on the subject is polarized (e.g., linearly polarized).

[0043] The received first imaging data is acquired within a first spectral band as a result of a first color filter of the imaging system allowing at least a portion of the first spectral band to enter the imaging system and preventing at least a portion of the second spectral band from entering the imaging system, such that a majority of the intensity information in the first imaging data acquired within the first spectral band is derived from the first illumination.

[0044] The received second imaging data is acquired within a second spectral band as a result of a second color filter of the imaging system allowing at least a portion of the second spectral band to enter the imaging system and preventing at least a portion of the first spectral band from entering the imaging system, such that a majority of the intensity information in the second imaging data acquired within the second spectral band is derived from the second illumination.

[0045] Thus, the imaging system acquires both first imaging data and second imaging data, and the second imaging data is distinct from the first imaging data in that the reflectance information is evidently different between the first and second imaging data.

[0046] The first imaging data corresponds to imaging performed within a first spectral band. The second imaging data corresponds to imaging performed within a second spectral band. Depending on the spectral overlap between the channels used to acquire the first and second imaging data and the spectral overlap between the first and second spectral bands, the first imaging data may or may not include information derived from the second illumination, or vice versa.

[0047] Imaging system embodiments described herein provide ways to ensure that a majority of the intensity information in first imaging data acquired in a first spectral band (e.g., at least 50% of the sum of the pixel intensity values) is derived from a first illumination. Similarly, such embodiments provide ways to ensure that a majority of the intensity information in second imaging data acquired in a second spectral band (e.g., at least 50% of the sum of the pixel intensity values ​​from an image) is derived from a second illumination.

[0048] In other words, at least 50% (i.e., a majority) of the total intensity information registered in the first imaging data (e.g., the sum of pixel intensity values ​​in the first imaging data) results from the first illumination (e.g., "red" light) entering the imaging system and being detected by pixels of the imaging device of the imaging system. Correspondingly, less than 50% (i.e., a "minority") of the total intensity information registered in the first imaging data (e.g., the sum of pixel intensity values ​​in the first imaging data) results from the second illumination (e.g., "blue" light) entering the imaging system and being detected by pixels of the imaging device of the imaging system. Corresponding logic is applied to the second imaging data.

[0049] The first and second illuminations are incident on the imaging system through an imaging system polarizer of the imaging system according to the polarization states of the reflected first and second illuminations received by the imaging system after reflection from the subject's surface such that specularly and diffusely reflected first illumination is incident on the imaging system and diffusely reflected second illumination is incident on the imaging system.

[0050] As described in more detail below, the first and second illumination incident on (i.e., directed toward) a subject has a particular initial polarization state (e.g., polarized or unpolarized). Upon reflection from the surface (and / or subsurface) of the subject, this polarization state may or may not be preserved. For example, diffusely reflected illumination is unpolarized (or randomly polarized) regardless of the polarization state of the illumination incident on the surface (e.g., surface “roughness” at least partially randomizes the polarization state after reflection). However, if the illumination incident on the surface is initially polarized, specularly reflected illumination will at least partially maintain the polarization state of the illumination incident on the surface. Unpolarized illumination incident on a surface will remain unpolarized after specular reflection. However, in some cases, unpolarized illumination incident on a surface will become at least partially polarized after reflection depending on the angle of incidence.

[0051] The imaging system is configured such that specularly reflected and diffusely reflected illumination is admitted or excluded from the imaging system depending on its polarization state upon incidence on the imaging system (i.e., after reflection from the surface).

[0052] The method 100 further includes, at block 104, determining information about specular reflection from the surface of the subject by comparing the first imaging data and the second imaging data.

[0053] As described above, the first imaging data includes information about the first illumination that is both specularly and diffusely reflected. The second imaging data includes information about the second illumination that is diffusely reflected. Specular reflection indicates a level of apparent glossiness, while diffuse reflection obscures such specular reflection. By comparing the first imaging data and the second imaging data, it is possible to determine the information about the specular reflection, and therefore the glossiness, because the comparison separates the specular reflection information from the diffuse reflection information.

[0054] Thus, in some embodiments, the information regarding specular reflection is indicative of a gloss level of the subject's skin, which is determined by calculating a difference between the intensity information in the first imaging data and the intensity information in the second imaging data. In similar terms, the result of the comparison between the first imaging data and the second imaging data corresponds to a measure of the glossiness of the subject's skin.

[0055] Certain embodiments described herein facilitate visualization of skin radiance (e.g., for the entire face) in a relatively inexpensive manner. For example, a user device, such as a smartphone equipped with an imaging system including an imaging device, can acquire first and second imaging data. In some cases, additional equipment, such as a hardware module (e.g., including a polarizer and / or an illumination system) that can be coupled to or used in situ with the user device, is used to facilitate acquisition of the first and second imaging data (e.g., to introduce first and second illumination according to its polarization state and / or to provide first and second illumination as referenced in method 100). In other cases, a dedicated device comprises hardware and corresponding functionality to facilitate acquiring first and second imaging data, providing first and second illumination, and / or determining the information referenced in method 100. Furthermore, certain embodiments described herein facilitate providing precise and / or accurate measurement and tracking / monitoring of skin radiance over time. In some cases, certain embodiments described herein provide a straightforward / low-complexity way to accurately determine specular information. Certain embodiments described herein provide a highly accurate way of distinguishing between specular and diffuse information in imaging data, potentially without the need to acquire separate images at different times and / or without the need to use complex lighting or imaging system setups to acquire the images. The light beam containing both specular and diffuse information follows a common path / same angle in the imaging system, thereby reducing complexity and / or allowing for more accurate estimation of the specular contribution. In some cases, certain embodiments described herein provide a relatively low-complexity (and cost-effective) solution to the problem of measuring a subject's shine, for example, through the use of a polarizer in the imaging system, as described below.

[0056] 2 illustrates a system 200 for determining certain information about a surface of a subject according to certain embodiments. System 200 at least partially implements certain methods described herein, such as method 100 above. In some embodiments, certain blocks of system 200 are omitted.

[0057] System 200 is being used by subject 202 and comprises an imaging system 204 and an illumination system 206. Imaging system 204 is used to acquire the imaging data referred to in method 100. Illumination system 206 is configured to provide first and second illumination 206a, 206b. Imaging system 204 and / or illumination system 206 are implemented by at least one device, such as a user device. Thus, in some embodiments, separate devices comprise imaging system 204 and illumination system 206, while in other embodiments, the same device comprises imaging system 204 and illumination system 206.

[0058] System 200 further includes computer 208 (e.g., including processing circuitry implemented by a device or a server or cloud-based service to perform certain methods described herein). Accordingly, computer 208 is communicatively coupled to imaging system 204 and / or lighting system 206 for transmitting and / or receiving data to and from these systems. This data is processed by the processing circuitry of computer 208 and / or stored in memory (e.g., of computer 208 or accessible to the processing circuitry of computer 208). In some embodiments, computer 208 controls the operation of imaging system 204 and / or lighting system 206. In some embodiments, computer 208 includes controls for controlling lighting parameters (e.g., operating parameters for lighting system 206) and / or sensing parameters (e.g., operating parameters for imaging system 204) and for storing and / or processing captured images or videos.

[0059] As shown in FIG. 2 , both a first illuminant 206 a (solid line) and a second illuminant 206 b (dashed line) are directed toward the surface of the subject 202 by the illumination system 206. The first and second illuminants 206 a, 206 b incident on the subject are then reflected (e.g., specularly and / or diffusely reflected), thereby directing at least a portion of the reflected illuminants 206 a, 206 b toward and into the imaging system 204. As shown in FIG. 2 , the angle between the incident and reflected light depends on the respective positions of the imaging system 204 and the illumination system 206 relative to the subject 202. While the operation of the system 200 is not strongly angle-dependent, different angles affect the degree to which the illuminants 206 a, 206 b are specularly or diffusely reflected. In one embodiment, the angle of incidence is as close to normal incidence as possible (e.g., less than 10 degrees), although it should be understood that other angle ranges may be used depending on the configuration of the imaging system 204 and the illumination system 206.

[0060] FIG. 3 shows different views (a) and (b) of a system 300 for determining certain information about a subject's surface according to certain embodiments. View (a) is a side view of the system 300 in a plane containing the optical axis. View (b) is a front view of certain components of the system 300 in a plane perpendicular to the optical axis. The components of the features of the system 300 are schematic and may be provided in any suitable arrangement other than that shown in FIG. 3. Reference numerals for features in the system 300 that have the same or similar function as corresponding features in the system 200 are incremented by 100. The system 300 includes certain corresponding features of the system 200 (i.e., an imaging system 304, an illumination system 306, and a computer 308). The system 300 at least partially implements certain methods described herein, such as the method 100.

[0061] Next, the imaging system 304 will be described.

[0062] The imaging system 304 includes a polarizing device (i.e., "imaging system polarizer" 310). The imaging system polarizer 310 is configured to allow reflected first and second illumination 306a, 306b (i.e., reflected from the surface of the subject 202) with an electric field component parallel to the polarization axis of the imaging system polarizer 310 to enter the imaging system and to attenuate reflected first and second illumination 306a, 306b with an electric field component perpendicular to the polarization axis. The first and second illumination 306a, 306b that are attenuated upon entering the imaging system 304 are attenuated by absorption or reflection by the imaging system polarizer 310. "Polarization axis" refers to the electric field vector direction selected for entry into the imaging system 304. For example, if the electric field vector of illumination 306a, 306b is parallel to the polarization axis, the polarizing device allows this illumination 306a, 306b to enter the imaging system 403.

[0063] 3, the polarization axis of the imaging system polarizer 310 is the same for both the first and second illuminations 306a, 306b. Thus, in some cases, a single or "common" imaging system polarizer 310 is used to control the incidence of both the reflected first and second illuminations 306a, 306b (according to their polarizations) into the imaging system 304. The use of a common imaging system polarizer 310 provides a simple / low-cost arrangement for controlling the incidence of the reflected first and second illuminations 306a, 306b.

[0064] In some cases, the imaging system polarizer 310 comprises a (linear) polarizing device, such as a polarizing filter, that allows (at least partial) transmission of the first and second illuminations 306a, 306b when the illuminations 306a, 306b contain a non-zero electric field (vector) component parallel to the polarization axis (also called the "transmission axis") of the polarizing filter. The polarizing filter attenuates transmission of the first and second illuminations 306a, 306b when the illuminations contain a non-zero electric field (vector) component perpendicular to the transmission axis of the polarizing filter.

[0065] In some cases, imaging system polarizer 310 comprises a polarizing device, such as a polarizing beam splitter (PBS, not shown), that can transmit or reflect illumination depending on the polarization state of the incident illumination. Such a polarizing device is configured to allow illumination of a particular polarization state to enter imaging system 304 depending on the polarization state (e.g., either polarized illumination reflected from the PBS or polarized illumination transmitted by the PBS, depending on the configuration of the PBS). In either case, the polarization axis of the PBS is oriented in a manner that selects which polarization state enters imaging system 304.

[0066] Thus, the portion of illumination 306a, 306b that has a zero electric field vector component perpendicular to the polarization axis of the imaging system polarizer 310 (and a non-zero component parallel to the polarization axis) is admitted to the imaging system 304 by the imaging system polarizer 310 with little or no attenuation.

[0067] However, the portion of the illumination 306a, 306b that has a zero electric field vector component parallel to the polarization axis of the imaging system polarizer 310 (and a non-zero component perpendicular to the polarization axis) is attenuated (potentially completely attenuated) by the imaging system polarizer 310. Thus, the level of attenuation depends on the ratio of the electric field vector component parallel to the polarization axis of the imaging system polarizer 310 to the electric field vector component perpendicular to the polarization axis.

[0068] Thus, the imaging system polarizer 310 admits and / or attenuates the first and second illumination 306a, 306b reflected from the surface of the subject 302 depending on the polarization state of the reflected illumination 306a, 306b directed into the imaging system 304.

[0069] An optical axis (“z”) is defined between the imaging system 304 and the subject 302. The optical axis is also referred to as the “imaging axis.” Relative to the optical axis z, the imaging system polarizer 310 has a “horizontal” polarization axis in the “x” direction, indicated by a point adjacent to the imaging system polarizer 310 (the corresponding “y” direction is shown vertically in FIG. 3 ). Thus, illumination 306 a, 306 b with a non-zero electric field component in the x-axis is introduced into the imaging system 304 by the imaging system polarizer 310, but may be attenuated depending on whether there is a non-zero electric field component perpendicular to the polarization axis of the imaging system polarizer 310. The coordinate system shown in FIG. 3 and elsewhere in this disclosure is provided to aid in explanation, and other coordinate systems may be used.

[0070] In this embodiment, the imaging system polarizer 310 is configured to admit the first and second illuminations 306a, 306b to the imaging system 304 according to the polarization states of the reflected first and second illuminations 306a, 306b received by the imaging system 304, such that, after reflection from the surface of the subject 302, specularly and diffusely reflected first illumination 306a is admitted to the imaging system 304 and diffusely reflected second illumination 306b is admitted to the imaging system 304. The illuminations 306a, 306b admitted by (i.e., after admission by) the imaging system polarizer 310 have zero electric field components perpendicular to the polarization axis of the imaging system polarizer 310 (assuming a perfectly efficient polarizer, which is unlikely in practice).

[0071] In some embodiments, the specularly and diffusely reflected first illumination 306a is attenuated depending on the polarization state of the reflected first illumination 306a incident on the subject 302. For example, if the polarization state of the reflected first illumination 306a is random, approximately 50% of the total reflected first illumination 306a is incident (the remaining 50% is attenuated by absorption or reflection). However, if the reflected first illumination 306a is not randomly polarized, the level of attenuation will vary depending on the angle between the polarization state and the polarization axis of the first illumination 306a. As a result, the first imaging data includes information about both specularly and diffusely reflected first illumination 306a.

[0072] Furthermore, if the specularly reflected secondary illumination 306b has a zero electric field vector component parallel to the polarization axis of the imaging system polarizer 310, it is likely to be nearly completely attenuated. The polarized secondary illumination 306b (before reflection) has an electric field component perpendicular to the polarization axis of the imaging system polarizer 310. If the polarization state is maintained (and not substantially rotated) after reflection (i.e., not randomized by surface roughness), the reflected secondary illumination 306b will have a zero electric field component parallel to the polarization axis of the imaging system polarizer 310. In this case, the secondary illumination 306b will be significantly attenuated, resulting in little or no secondary illumination 306b being incident by the imaging system polarizer 310. Surface roughness or low gloss will result in some diffuse reflection of the secondary illumination 306b, which will at least partially randomize the polarization state of the (originally polarized) secondary illumination 306b. Thus, at least a portion of the diffusely reflected second illumination 306b includes a non-zero electric field component aligned with the polarization axis, allowing at least attenuated entry of said diffusely reflected second illumination 306b. Thus, the second imaging data includes information about the diffusely reflected second illumination 306b (but not about the specularly reflected second illumination 306b).

[0073] Thus, the imaging system polarizer 310 is used to admit and / or attenuate illumination 306a, 306b with a particular polarization state, i.e., the orientation of the polarization axis of the imaging system polarizer 310 is such that a particular portion of the reflected first and second illumination 306a, 306b is admitted or attenuated depending on the polarization state of the reflected first and second illumination 306a, 306b.

[0074] As highlighted above, the reflected first and second illumination 306a, 306b have multiple polarization states due to the polarization states of different portions of the reflected first and second illumination 306a, 306b being modified to different degrees after reflection from different surface types. For example, polarized second illumination 306b incident on a rough surface will be randomly polarized after reflection, while polarized second illumination 306b incident on a smooth, shiny surface will maintain its polarization state after reflection (i.e., illumination that was initially polarized will remain polarized after reflection).

[0075] In some embodiments, the initially unpolarized (or randomly polarized) first illumination 306a remains unpolarized after reflection from a rough surface. In some embodiments, the initially unpolarized (or randomly polarized) first illumination 306a becomes at least partially polarized after reflection from a smooth or shiny surface. In some embodiments, the first illumination 306a is polarized with an initial polarization state that is orthogonal to the polarization state of the second illumination 306b.

[0076] Thus, for unpolarized first illumination 306a and polarized second illumination 306b incident on a smooth and / or glossy subject 302, the first imaging data (corresponding to imaging using the first illumination 306a) contains information about both specularly and diffusely reflected first illumination 306a. Because the reflected second illumination 306b entering the imaging system is substantially attenuated by the imaging system polarizer 310 due to its zero or near-zero electric field component parallel to the polarization axis of the imaging system polarizer 310, the pixel intensity levels registered for the second imaging data (corresponding to imaging using the second illumination 306b) will be much lower (i.e., darker) than the pixel intensity levels registered for the first imaging data.

[0077] Thus, by calculating the difference between the first imaging data (which contains both specular and diffuse reflection information) and the second imaging data (which contains diffuse reflection information), information about the specular reflection information is determined. In the above case, the glossy surface results in a low level of diffuse reflection and a relatively high level of specular reflection.

[0078] In the case of unpolarized first illumination 306a and polarized second illumination 306b incident on the rough subject 302, the first imaging data (corresponding to imaging using the first illumination 306a) includes information about both specularly and diffusely reflected first illumination 306a. Because the reflected second illumination 306 entering the imaging system 304 is not substantially attenuated by the imaging system polarizer 310 (due to its non-zero electric field component parallel to the polarization axis of the imaging system polarizer 310 resulting from the reflected second illumination 306b, including diffuse reflection, which may be at least partially randomly polarized), the pixel intensity levels registered for the second imaging data (corresponding to imaging using the second illumination 306) will not be dark (unlike in the previous case).

[0079] Thus, information about specular reflection is determined by calculating the difference between the first imaging data (which contains both specular and diffuse reflection information) and the second imaging data (which contains diffuse reflection information). In the above case, the rough surface results in a high level of diffuse reflection and a relatively low level of specular reflection.

[0080] Thus, the ratio of (or difference between) pixel intensity values ​​in the first and second imaging data indicates the relative amount of specular and diffuse reflection from the surface. If the second imaging data is relatively "darker" than the first imaging data (with lower registered pixel intensity values), this indicates a shiny surface. However, if the second imaging data is "lighter" than the first imaging data (with relatively higher registered intensity values ​​than the "shiny" case), this indicates a rough surface.

[0081] In some cases, the ratio or difference between pixel intensity values ​​in the first and second imaging data provides a quantitative measure of specular reflectance.

[0082] In some embodiments, the imaging system 304 comprises (at least one) first color filter and (at least one) second color filter. The color filter array 312 is configured to enable at least one imaging device 314 of the imaging system 304 to acquire first imaging data in a first spectral band (through the first color filter) and second imaging data in a second spectral band (through the second color filter). The color filter array 312 may be provided as part of the imaging device 314 itself (e.g., a Bayer filter or another type of filter layer) or as a separate component.

[0083] In one embodiment, color filter array 312 is aligned with pixels (not shown) of imaging device 314 such that each filter "cell" or "channel" of array 312 is aligned with a corresponding pixel of imaging device 314. For example, a Bayer filter comprises red, green, and blue bandpass filter "cells" aligned with pixels of imaging device 314. Thus, some pixels of imaging device 314 register "red" light, some pixels register "green" light, and the remaining pixels register "blue" light. In one embodiment, the "red" pixels provide first imaging data and the "green" pixels provide second imaging data. In another embodiment, the "red" pixels provide first imaging data and the "blue" pixels provide second imaging data. Any other combination of colors associated with pixels may provide first and second imaging data.

[0084] Thus, in some embodiments, the imaging system 304 comprises at least one imaging device 314 and an optical filter array 312. The optical filter array 312 comprises a first color filter and a second color filter. The optical filter array 312 is configured to pass at least a portion of a first spectral band into the imaging system 304 through a first set of pixels of the at least one imaging device 314 such that a majority of the intensity information in first imaging data acquired within the first spectral band is derived from the first illumination 306 a. The optical filter array 312 is further configured to pass at least a portion of a second spectral band into the imaging system 304 through a second, different set of pixels of the at least one imaging device 314 such that a majority of the intensity information in second imaging data acquired within the second spectral band is derived from the second illumination 306 a.

[0085] The imaging device 314 and / or the computer 308 extract the first imaging data separately from the second imaging data from the raw imaging data acquired by the imaging device 314. For example, certain pixels of the imaging device 314 that correspond to a particular color (e.g., one of red, green, or blue) provide pixel intensity information as the "raw" data for the first imaging data. Certain other pixels of the imaging device 314 that correspond to another color (e.g., one of red, green, or blue) provide pixel intensity information as the "raw" data for the second imaging data.

[0086] In another embodiment, imaging system 304 comprises multiple (e.g., two or more) imaging devices (not shown). A first one of the imaging devices receives the first illumination but not the second illumination (e.g., via an appropriate optical arrangement including appropriate optical filters). A second one of the imaging devices receives the second illumination but not the first illumination. Thus, the first imaging device provides first imaging data and the second imaging device provides second imaging data.

[0087] According to the above-described arrangements, the first and second imaging data may be acquired over the same or overlapping time periods. In other words, in some embodiments, the time frame over which the first imaging data is acquired at least partially overlaps the time frame over which the second imaging data is acquired. This occurs when a particular pixel (or first imaging device) associated with the first imaging data performs imaging (e.g., acquires frames) over a first time period, and the second imaging data performs imaging over a second time period that at least partially overlaps with the first time period.

[0088] In another embodiment, imaging system 304 is configured to acquire the first and second imaging data simultaneously, e.g., pixels configured to measure intensity levels for the first imaging data measure such intensity levels simultaneously with pixels configured to measure intensity levels for the second imaging data.

[0089] By acquiring the first and second imaging data over overlapping time periods and / or simultaneously, imaging data for determining information related to specular reflection can be acquired in a relatively straightforward and inexpensive manner. For example, a user device such as a smartphone can be configured to acquire the first and second imaging data in a straightforward manner by providing an imaging system polarizer 310 in conjunction with the user device's imaging device as described above. In some cases, the imaging system polarizer 310 is a component of the user device itself, or in other cases, it is a separate component.

[0090] Because a subject's surface (e.g., a user's face) moves voluntarily and / or involuntarily, acquiring first and second imaging data over overlapping time periods and / or simultaneously reduces errors in determining information related to specular reflection. For example, if first and second imaging data are acquired simultaneously, the same pixels are likely to register information from the same portion of the user's facial surface. Additionally, in some cases, gloss measurements are taken of multiple views of the face to cover multiple angles. Embodiments described herein facilitate acquiring a sequence of frames (e.g., a video or image sequence) using an imaging device capable of simultaneously spectrally separating the first and second imaging data.

[0091] The spectral gating of the first and second illumination, and the polarization dependence of the illumination 306a, 306b incident on the imaging system 304, allows the first imaging data to be distinguished from the second imaging data. Thus, the configuration of the imaging system 304 and illumination system 306 provides a way to easily distinguish between reflected illumination 306a, 306b containing specular information and reflected illumination 306a, 306b containing diffuse information, and thus determine the specular information.

[0092] Next, the lighting system 306 will be described.

[0093] The illumination system 306 includes a first illumination source 316 (e.g., at least one light emitting diode (LED) or other type of light source) configured to provide a first illumination 306a. In this embodiment, the first illumination 306a is unpolarized and directed toward the subject 302. The illumination system 306 includes a second illumination source 318 (e.g., at least one light emitting diode (LED) or other type of light source) configured to provide a second illumination 306b. The second illumination 306a is directed toward the subject 302 in a manner similar to the first illumination 306b. In this regard, the first illumination source 316 and the second illumination source 318 may be adjacent to each other or in any suitable arrangement for illuminating the subject 302.

[0094] The illumination system 306 includes an illumination system polarizer 320 configured to polarize the second illumination 306b directed toward the subject 302. The polarization axis of the imaging system polarizer 310 is orthogonal (e.g., relative to the optical axis) to the polarization axis of the illumination system polarizer 320. In similar terms, the polarization states incident on or transmitted by the imaging system polarizer 310 and the illumination system polarizer 320 are orthogonal to each other (or the two orthogonal polarization states represent diagonally opposite points on the Poincaré sphere). As shown in FIG. 3, the imaging system polarizer 310 has a polarization axis in the x-direction, and the illumination system polarizer 320 has a polarization axis in the y-direction.

[0095] In some embodiments, the illumination system 306 is configured to direct the first and second illuminations 306a, 306b toward the subject 302 such that both specular and diffuse reflection components of the first and second illuminations 306a, 306b reflected from the surface of the subject 302 are directed into the imaging system for internal entry according to the polarization states of the reflected first and second illuminations 306a, 306b.

[0096] As noted above, the angle of incidence varies depending on the configuration. In a possible configuration, the illumination system 306 includes first and second illumination sources 316, 318 positioned adjacent the imaging system 304 so that the angle of incidence is as close to normal incidence as possible. In a possible configuration, multiple first and second illumination sources 316, 318 are positioned around the imaging system 304 (e.g., in a ring or concentrically) so that the subject 302 is uniformly illuminated from multiple angles.

[0097] 3, the illumination system 306 is configured such that the first illumination 306a directed toward the subject 302 is unpolarized. However, in some embodiments, the illumination system 306 includes an additional illumination system polarizer (not shown) configured to polarize the first illumination 306a directed toward the subject 302 such that the polarization state of the first illumination 306a incident on the subject 302 is orthogonal to the polarization state of the second illumination 306b incident on the subject. In other words, the additional illumination system polarizer has its polarization axis oriented along the x-axis in FIG. 3.

[0098] Figure 4 shows example optical parameters of certain components of the system 300 of Figure 3 in graphical form of percent transmittance as a function of wavelength (for a solid line), overlaid with dotted lines corresponding to the spectral content of the first and second illumination sources 316, 318 referenced in Figure 3. The reference numbers of features referenced in Figure 3 are incremented by 100.

[0099] In Case #1, the first illumination 406a (dotted line) includes spectral content in a first spectral band centered around 650 nm (nanometers), i.e., toward the "red" portion of the spectrum. The full-width at half-maximum spectral width of the first spectral band is around 60 nm. The color filter array 312 in FIG. 3 includes different "cells" for admitting / passing the first spectral band. In FIG. 4, the spectral light entrance band for admitting the first illumination 406a is indicated by a solid line 412a. The spectral light entrance band is primarily in the "red" to "infrared" portion of the spectrum (e.g., between approximately 570 and 900 nm). The first spectral band of the first illumination 406a substantially overlaps with the spectral light entrance band 412a. Thus, the cells in the color filter array 312 of FIG. 3 corresponding to the spectral light entrance band 412a admit the first illumination 406a so that it is detected by the corresponding pixel (e.g., to reduce detection of illumination in other spectral bands).

[0100] The second illumination 406b (dotted line) includes spectral content in a second spectral band centered around 450 nm, i.e., toward the "blue" portion of the spectrum. The full-width at half-maximum spectral width of the second spectral band is around 50 nm. The spectral light entry band for entering the second illumination 406b is shown by the solid line 412b. The spectral light entry band is primarily in the "bluer" portion of the spectrum (e.g., between <400 and 550 nm). The second spectral band of the second illumination 406b substantially overlaps with the spectral light entry band 412b. Thus, the cells in the color filter array 312 of FIG. 3 corresponding to the spectral light entry band 412b enter the second illumination 406b such that it is detected by the corresponding pixel (e.g., to reduce detection of illumination in other spectral bands, such as the first illumination 406a).

[0101] In Case #2 of FIG. 4, the first illumination 406a and spectral light entry band 412a are the same as in Case #1. However, the second illumination 406b (dotted line) includes spectral content in a second spectral band centered around 530 nm, i.e., including the "green" portion of the spectrum. The full-width at half-maximum spectral width of the second spectral band is around 50 nm. The spectral light entry band for entering the second illumination 406b is shown by the solid line 412b. The spectral light entry band is primarily in the "green" portion of the spectrum (e.g., between approximately 450 and 610 nm). The second spectral band of the second illumination 406b substantially overlaps with the spectral light entry band 412b. Thus, the cells in the color filter array 312 of FIG. 3 corresponding to the spectral light entrance band 412b admit the second illumination 406b so that it is detected by the corresponding pixel (e.g., to reduce detection of illumination in other spectral bands, such as the first illumination 406a).

[0102] Case #2 highlights how there may be some spectral overlap between the spectral entry bands and / or the first and second illuminations 406a, 406b when sufficient spectral differentiation exists as described below.

[0103] This spectral discrimination is achieved when the wavelength band (e.g., interval) of each illumination source 316, 318 includes: 1) substantial spectral overlap with the spectral sensitivity of the associated channel (e.g., a red light source has an associated red detection channel) of the imaging system 304 (e.g., substantial overlap of the spectral content of illumination 406a, 406b with the corresponding spectral input band 412a, 412b); and 2) minimal spectral overlap with the spectral sensitivity of unassociated channels. In other words, the majority of the intensity information in the first imaging data acquired within the first spectral band is derived from the first illumination 406a. Similarly, the majority of the intensity information in the second imaging data acquired within the second spectral band is derived from the second illumination 406b. While there may be some “leakage” between channels, to some extent in Case #1 and even more so in Case #2, the majority of pixel intensity information is likely derived from the correct channel due to the spectral discrimination described above.

[0104] Case #1 refers to a scenario considered as having ideal overlap (e.g., overlap measured as the ratio of the overlap area under the curve to the area of ​​the illumination source spectrum) between the first illumination source 406a and the corresponding detection channel defined by the spectral entrance band 412a. The same is true for the second illumination source 406b and the corresponding detection channel defined by the spectral entrance band 412a. The spectral overlap between the first and second illumination sources 406a, 406b and the non-associated detection channel (e.g., the second and first spectral entrance bands 412b, 412a, respectively) is then minimal. For example, <10% of the total spectral width overlaps. It may be observed that the spectral overlap between the spectra of the first and second illumination sources 406a, 406b and the non-associated detection channel is approximately equivalent to the error in the calculated specular reflectance. Case #2 has a greater degree of overlap compared to Case #1, but still sufficient spectral differentiation to facilitate spectral gating operations.

[0105] The selection of one or more wavelengths for each of the first and second illuminators 406a, 406b is generally not critical, other than being appropriate for the wavelength detection range of the associated detection channel. For example, rather than having the first illuminator 406a include the red portion of the spectrum and the second illuminator 406b include the blue or green portion of the spectrum, as in cases #1 and #2 above, another configuration may be selected. For example, the first illuminator 406a may include the blue or green portion of the spectrum, and the second illuminator 406b may include the green or red portion of the spectrum. Furthermore, a non-visible illumination source, e.g., ultraviolet or infrared, may be used for at least one of the illumination sources.

[0106] 3, and in some embodiments, the illumination system 306 comprises a first illumination unit (e.g., first illumination source 316) for providing light illumination (e.g., directed toward the face of the subject 302). The first illumination unit provides the first illumination 406a by emitting in a first spectral emission band. The first spectral emission band is selected to substantially overlap with a first spectral detection band of the imaging unit (e.g., imaging system 304).

[0107] The illumination system 306 includes a second illumination unit (e.g., second illumination source 318) for providing linearly polarized light (illumination) (e.g., directed toward the face of the subject 302). The second illumination unit provides the second illumination 406b by emitting in a second spectral emission band. The second spectral emission band is selected to substantially overlap with the second spectral detection band of the imaging unit.

[0108] A first linear polarizing filter (eg, illumination system polarizer 320) associated with the second illumination unit is oriented perpendicular to the polarization axis of the light entering the imaging unit.

[0109] The imaging unit includes a second linear polarizing filter (e.g., imaging system polarizer 310). The imaging unit is configured to admit at least two spectral detection bands. The imaging unit is configured to capture (e.g., image) the diffuse reflectance of the second illumination 406b reflected from a surface (e.g., a face) of the subject 302. The imaging unit is further configured to capture the total reflectance (e.g., diffuse reflectance and specular reflectance) of the first illumination 406a reflected from the surface of the same subject. The wavelengths and bandwidths of the illuminations 406a, 406b are determined in combination with the spectral detection bands associated with the imaging unit.

[0110] A control unit (e.g., computer 308) is provided to control the illumination and detection parameters and to store and / or process the captured raw Bayer images or videos (e.g., receive the first and second imaging data and determine information regarding specular reflectance). As described above, specular reflectance is extracted from two separate channels from the raw Bayer image data.

[0111] 5 is a schematic diagram of a representation of a method for determining specific information about a surface of a subject according to one embodiment. Reference is made to the features of FIG. 3, with the reference numbers of similar features incremented by 200. The representation shows imaging data (represented by images) acquired by the procedure described above.

[0112] According to FIG. 5, information regarding specular and diffuse reflection is shown in the parallel “P” image, which is derived from the incident first illumination 306a. Information regarding diffuse reflection is shown in the cross “C” image, which is derived from the incident second illumination 306b. The total intensity is shown in the “P+C” image. The difference between the “P” and “C” images is shown in the “PC” image. The “PC” image therefore corresponds to the specular reflection image. Each of the images is derived by “de-Bayerizing” or extracting an individual channel (i.e., red, blue, or green) incident by the corresponding pixel associated with the color filter array 512. FIG. 5 also shows a sequence of frames acquired at various angles of the specular reflection image. The process for acquiring each frame is relatively straightforward (e.g., in some cases, one frame is acquired per angle, and only that one frame is needed to extract the specular reflection information).

[0113] Some commercially available color cameras, such as those for mobile phones, have built-in Bayer filters (e.g., with green (two), red, and blue sub-filters). By utilizing a spectral gating procedure or polarization gating with orthogonal polarizers as described herein, cross- and parallel-polarized images of a face are acquired simultaneously without motion artifacts. Thus, cross- and parallel-polarized images can be acquired simultaneously, which reduces cost and / or complexity and allows for rapid frame acquisition and processing, e.g., for multiple frames at different angles.

[0114] Due to the scattering and reflectance properties of skin, the combination of a color camera and multiple illumination sources (at least one of which is polarized) results in less overlap in the Bayer spectra. This arrangement provides two images (e.g., corresponding to the first and second imaging data), one containing specular reflection and one containing no specular reflection at all (i.e., containing diffuse reflection instead).

[0115] The intensities recorded in the two images are distinguishable due to the different absorption, scattering, and polarization properties of the skin (as well as the different intensities of the first and second illumination 306a, 306b provided by the illumination system 306). The sensitivity of the gloss measurement is refined by selecting appropriate wavelengths of light with a Bayer filter (or other type of color filter array 512 or other optical arrangement) and prior knowledge of the specular reflectance of the skin.

[0116] Additionally, certain methods described herein are extended by analyzing histograms of pixel intensity information in a "PC" image to quantitatively measure, for example, oiliness reduction following a personal care regimen. For example, a PC image histogram with a peak toward higher pixel intensity values ​​indicates a large amount of specular reflection, while a more even distribution of pixel intensity values ​​(or a peak toward lower pixel intensity values) indicates minimal specular reflection.

[0117] 6 illustrates a method 600 (e.g., a computer-implemented method) for determining certain information about a subject's surface (e.g., a user's skin). Method 600 is implemented by a computer, such as a user device or a server or cloud-based service (e.g., communicatively coupled to a user device). An example of a user device includes a smart device, such as a smartphone, tablet, smart mirror, or any other device capable of processing imaging data as described below. Reference is made to FIG. 3 in the following description.

[0118] Method 600 includes blocks 102 and 104 of method 100. Method 600 further includes, in block 602, extracting the first imaging data separately from the second imaging data from raw imaging data acquired by the at least one imaging device 314. Block 602 is performed before block 102.

[0119] FIG. 7 illustrates a tangible, machine-readable medium 700 storing instructions 702 that, when executed by a processing circuit (e.g., at least one processor) 704, cause the processing circuit 704 to perform certain methods described herein, such as method 100, method 600, and / or related embodiments.

[0120] 8 illustrates an apparatus 800 that may be used to implement certain methods described herein, such as method 100, method 600, and / or related embodiments. Apparatus 800 includes modules whose functionality corresponds to certain features described in connection with system 200 of FIG. 2, such as computer 208. Apparatus 800 includes processing circuitry 802.

[0121] The processing circuit 802 comprises a receiving module 804 configured to receive first and second imaging data acquired by the imaging system 204 of the subject 202. The subject 202 is illuminated by first illumination 206a in a first spectral band and second illumination 206b in a second spectral band having a different spectral content than the first spectral band. The second illumination 206a incident on the subject is polarized.

[0122] The received first imaging data is acquired within a first spectral band as a result of a first color filter of the imaging system 204 allowing at least a portion of the first spectral band to enter the imaging system and preventing at least a portion of the second spectral band from entering the imaging system, such that a majority of the intensity information in the first imaging data acquired within the first spectral band is derived from the first illumination 206a.

[0123] The received second imaging data is acquired within a second spectral band as a result of a second color filter of the imaging system 204 allowing at least a portion of the second spectral band to enter the imaging system and preventing at least a portion of the first spectral band from entering the imaging system, such that a majority of the intensity information in the second imaging data acquired within the second spectral band is derived from the second illumination 206b.

[0124] The first and second illuminations are incident on the imaging system 204 via the imaging system polarizer 310 of the imaging system 204 according to the polarization states of the reflected first and second illuminations received by the imaging system after reflection from the subject's surface, such that specularly and diffusely reflected first illumination 206a is incident on the imaging system 204 and diffusely reflected second illumination 206b is incident on the imaging system 204.

[0125] The processing circuit 802 further comprises a determining module 806 configured to determine information regarding specular reflection from a surface of the subject 202 by comparing the first imaging data and the second imaging data.

[0126] In some embodiments, the apparatus 800 further comprises an imaging system 204. In some embodiments, the apparatus 800 further comprises an illumination system 206 configured to provide first and second illumination 206a, 206b.

[0127] In some embodiments, the determination module 806 is configured to determine a measure of the subject's skin radiance based on a comparison between the first imaging data and the second imaging data.

[0128] In some cases, any of the above-mentioned modules (e.g., receiving module 804 and / or decision module 806) includes at least one dedicated processor (e.g., an application specific integrated circuit (ASIC) and / or a field programmable gate array (FPGA), etc.) for performing the functionality of the module.

[0129] In some cases, the modules (e.g., receiving module 804 and / or determining module 806) comprise at least one processor for executing instructions that cause the at least one processor to perform the functions of the modules described above. In such examples, the instructions are stored on a machine-readable medium (not shown) accessible to the at least one processor. In some examples, the module itself comprises the machine-readable medium. In some examples, the machine-readable medium is separate from the module itself (e.g., at least one processor of the module is provided in communication with the machine-readable medium to access the instructions stored therein).

[0130] Although certain methods have been described as computer-implemented, in some cases such methods may refer to imaging methods in which an illumination system and / or an imaging system are used as part of the imaging method to enable acquisition of first and second imaging data (for use in performing the computer-implemented method). Similarly, in some cases, any apparatus for performing such a computer-implemented method further comprises an illumination system and / or an imaging system to enable acquisition of the first and second imaging data.

[0131] This disclosure includes subject matter defined by the following numbered paragraphs:

[0132] Paragraph 1. Receiving imaging data acquired by an imaging system of a subject illuminated by first illumination in a first spectral band and second illumination in a second spectral band having a different spectral content than the first spectral band, wherein the second illumination incident on the subject is polarized, and the imaging system: acquiring first imaging data in a first spectral band by allowing at least a portion of the first spectral band to enter the imaging system and preventing at least a portion of the second spectral band from entering the imaging system such that a majority of intensity information in the first imaging data acquired in the first spectral band is derived from the first illumination; acquiring second imaging data in a second spectral band by allowing at least a portion of the second spectral band to enter the imaging system and preventing at least a portion of the first spectral band from entering the imaging system such that a majority of intensity information in the second imaging data acquired in the second spectral band is derived from the second illumination; directing the first and second illuminations into the imaging system according to polarization states of the reflected first and second illuminations received by the imaging system after reflection from the surface of the subject, such that specularly and diffusely reflected first illumination is directed into the imaging system and diffusely reflected second illumination is directed into the imaging system; and determining information about specular reflection from a surface of the subject by comparing the first imaging data with the second imaging data; 10. A computer-implemented method comprising:

[0133] Paragraph 2. The computer-implemented method of Paragraph 1, wherein a time frame during which the first imaging data is acquired at least partially overlaps with a time frame during which the second imaging data is acquired.

[0134] Paragraph 3. The computer-implemented method of Paragraph 2, wherein the imaging system is configured to acquire the first and second imaging data simultaneously.

[0135] Paragraph 4. The computer-implemented method of any one of paragraphs 1 to 3, wherein the imaging system includes an imaging system polarizer configured to allow reflected first and second illumination having electric field components parallel to a polarization axis of the imaging system polarizer to enter the imaging system, and to attenuate reflected first and second illumination having electric field components perpendicular to the polarization axis.

[0136] Paragraph 5. The computer-implemented method of any one of paragraphs 1 to 4, wherein the information about the specular reflection indicates a gloss level of the subject's skin, and the gloss level is determined by calculating a difference between intensity information in the first imaging data and intensity information in the second imaging data.

[0137] Paragraph 6. The computer-implemented method of any one of paragraphs 1 to 5, wherein the imaging system comprises a color filter array configured to enable at least one imaging device of the imaging system to acquire first imaging data in a first spectral band and second imaging data in a second spectral band, and the computer-implemented method further comprises extracting the first imaging data separately from the second imaging data from raw imaging data acquired by the at least one imaging device.

[0138] Paragraph 7. A tangible, machine-readable medium comprising instructions that, when executed by a processing circuit, cause the processing circuit to perform the method of any one of paragraphs 1 through 6.

[0139] Paragraph 8. An apparatus having a processing circuit, the processing circuit: 1. A receiving module configured to receive imaging data acquired by an imaging system of a subject illuminated by first illumination in a first spectral band and second illumination in a second spectral band having a different spectral content than the first spectral band, wherein the second illumination incident on the subject is polarized, and the imaging system: acquiring first imaging data in a first spectral band by allowing at least a portion of the first spectral band to enter the imaging system and preventing at least a portion of the second spectral band from entering the imaging system such that a majority of intensity information in the first imaging data acquired in the first spectral band is derived from the first illumination; acquiring second imaging data in a second spectral band by allowing at least a portion of the second spectral band to enter the imaging system and preventing at least a portion of the first spectral band from entering the imaging system such that a majority of intensity information in the second imaging data acquired in the second spectral band is derived from the second illumination; and directing the first and second illuminations into the imaging system according to polarization states of the reflected first and second illuminations received by the imaging system after reflection from the surface of the subject, such that specularly and diffusely reflected first illumination is directed into the imaging system and diffusely reflected second illumination is directed into the imaging system. a receiving module configured to: and a determination module configured to determine information regarding specular reflection from a surface of the subject by comparing the first imaging data and the second imaging data.

[0140] Paragraph 9. The apparatus of Paragraph 8, wherein the result of the comparison between the first imaging data and the second imaging data corresponds to a measurement of the radiance of the subject's skin.

[0141] Paragraph 10. The apparatus of Paragraphs 8 or 9, wherein the apparatus further comprises an imaging system and / or an illumination system configured to provide first and second illumination.

[0142] Paragraph 11. The apparatus of Paragraph 10, wherein the imaging system includes an imaging system polarizer configured to allow reflected first and second illumination having electric field components parallel to a polarization axis of the imaging system polarizer to enter the imaging system, and to prevent reflected first and second illumination having electric field components perpendicular to the polarization axis from entering the imaging system.

[0143] Paragraph 12. The apparatus of Paragraph 11, wherein the illumination system includes an illumination system polarizer configured to polarize the second illumination directed at the subject, the polarization axis of the imaging system polarizer being orthogonal to the polarization axis of the illumination system polarizer.

[0144] Paragraph 13. The apparatus of any one of Paragraphs 10 to 12, wherein the illumination system is configured such that the first illumination directed at the subject is unpolarized, or wherein the illumination system comprises an additional illumination system polarizer configured to polarize the first illumination directed at the subject such that the polarization state of the first illumination directed at the subject is orthogonal to the polarization state of the second illumination directed at the subject.

[0145] Paragraph 14. The apparatus of any one of Paragraphs 10 to 13, wherein the illumination system is configured to direct the first and second illuminations toward the subject such that both specular and diffuse reflection components of the first and second illuminations reflected from the surface of the subject are directed into the imaging system for internal entry according to the polarization states of the reflected first and second illuminations.

[0146] Paragraph 15. An imaging system comprising at least one imaging device and an optical filter array, the optical filter array comprising: passing at least a portion of a first spectral band into the imaging system through a first set of pixels of at least one imaging device such that a majority of intensity information in first imaging data acquired within the first spectral band is derived from the first illumination; passing at least a portion of the second spectral band into the imaging system through a second, different set of pixels of the at least one imaging device such that a majority of the intensity information in second imaging data acquired within the second spectral band is derived from the second illumination; 15. The apparatus of any one of paragraphs 10 to 14, configured to:

[0147] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is by way of illustration or example only and is not to be considered restrictive. The invention is not limited to the disclosed embodiments.

[0148] One or more features described in one embodiment may be combined with or substituted for features described in another embodiment, for example, the methods 100, 600 of Figures 1 and 6 may be modified based on features described in connection with the systems 200, 300, machine-readable medium 700, and / or apparatus 800 of Figures 2 and 3, and vice versa.

[0149] Embodiments of the present disclosure may be provided as a method, a system, or a combination of machine-readable instructions and processing circuitry, such machine-readable instructions being contained on a non-transitory machine (e.g., computer) readable storage medium (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-readable program code thereon or thereon.

[0150] The present disclosure will be described with reference to flowcharts and block diagrams of methods, devices, and systems according to embodiments of the present disclosure. Although the flowcharts described above show a specific order of execution, the order of execution may differ from that shown. Blocks described in connection with one flowchart may be combined with blocks in another flowchart. It will be understood that each block in the flowcharts and / or block diagrams, and combinations of blocks in the flowcharts and / or block diagrams, may be implemented by machine-readable instructions.

[0151] The machine-readable instructions are executed by a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or another programmable data processing device, for example, to implement the functions described in the descriptions and figures. Specifically, a processor or processing circuit, or modules thereof, executes the machine-readable instructions. Thus, the computer 208, the computer 308, and / or the functional modules of the apparatus 800 (e.g., the receiving module 804 and / or the decision module 806), as well as the functional modules of other devices described herein, are implemented by a processor that executes machine-readable instructions stored in a memory or operates according to instructions embedded in a logic circuit. The term "processor" should be broadly interpreted to include a CPU, a processing unit, an ASIC, a logic unit, a programmable gate array, or the like. The methods and functional modules may all be executed by a single processor or may be divided among several processors.

[0152] Such machine-readable instructions may also be stored in computer-readable storage capable of directing a computer or other programmable data processing device to operate in a particular mode.

[0153] Such machine-readable instructions may also be loaded into a computer or other programmable data processing device such that the computer or other programmable data processing device performs a sequence of operations to create a computer-implemented process, such that the instructions executing on the computer or other programmable device implement the functions specified by the blocks in the flowcharts and / or block diagrams.

[0154] Furthermore, the teachings herein may be implemented in the form of a computer program product, the computer program product being stored on a storage medium and comprising a plurality of instructions for causing a computing device to perform the methods according to the embodiments of the present disclosure.

[0155] Elements or steps described in connection with one embodiment may be combined with or substituted by elements or steps described in connection with another embodiment. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the term "comprising" does not exclude other elements or steps, and the singular does not exclude the plural. A single processor or other unit may fulfill several items recited in a claim. The mere fact that certain means are recited in mutually different dependent claims does not indicate that a combination of these means cannot be used to advantage. A computer program may be stored or distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, or may be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. receiving first and second imaging data acquired by an imaging system of a subject illuminated with first illumination in a first spectral band and second illumination in a second spectral band having a different spectral content than the first spectral band, wherein the second illumination incident on the subject is polarized; the received first imaging data is acquired within a first spectral band as a result of a first color filter of the imaging system allowing at least a portion of the first spectral band to enter the imaging system and preventing at least a portion of the second spectral band from entering the imaging system, such that a majority of intensity information in the first imaging data acquired within the first spectral band is derived from the first illumination; the received second imaging data is acquired within a second spectral band as a result of a second color filter of the imaging system allowing at least a portion of the second spectral band to enter the imaging system and preventing at least a portion of the first spectral band from entering the imaging system, such that a majority of intensity information in the second imaging data acquired within the second spectral band is derived from the second illumination; and coupling the first illumination and the second illumination to the imaging system through an imaging system polarizer of the imaging system in accordance with polarization states of the reflected first illumination and the second illumination received by the imaging system after reflection from the subject's skin surface, such that the specularly reflected and diffusely reflected first illumination is coupled to the imaging system and the diffusely reflected second illumination is coupled to the imaging system. determining information about specular reflection from the skin surface of the subject by comparing the first imaging data with the second imaging data; and The computer-implemented method, wherein the subject is a person.

2. The computer-implemented method of claim 1 , wherein a time frame during which the first imaging data is acquired at least partially overlaps a time frame during which the second imaging data is acquired.

3. The computer-implemented method of claim 2 , wherein the first imaging data and the second imaging data are acquired simultaneously.

4. 4. The computer-implemented method of claim 1, wherein the imaging system polarizer allows the reflected first illumination and the second illumination having electric field components parallel to a polarization axis of the imaging system polarizer to enter the imaging system and attenuates the reflected first illumination and the second illumination having electric field components perpendicular to the polarization axis.

5. 5. The computer-implemented method of claim 1, wherein the information regarding specular reflection indicates a gloss level of the subject's skin, and the gloss level is determined by calculating a difference between the intensity information in the first imaging data and the intensity information in the second imaging data.

6. 6. The computer-implemented method of claim 1, wherein the first color filter and the second color filter are part of a color filter array that enables at least one imaging device of the imaging system to acquire the first imaging data in the first spectral band and the second imaging data in the second spectral band, and the computer-implemented method further comprises extracting the first imaging data separately from the second imaging data from raw imaging data acquired by the at least one imaging device.

7. A tangible, machine-readable medium comprising instructions that, when executed by a processing circuit, cause the processing circuit to perform the computer-implemented method of any one of claims 1 to 6.

8. 1. An apparatus comprising a processing circuit, the processing circuit comprising: a receiving module that receives first and second imaging data acquired by an imaging system of a subject illuminated by first illumination in a first spectral band and second illumination in a second spectral band having a different spectral content than the first spectral band, wherein the second illumination incident on the subject is polarized; the received first imaging data is acquired within a first spectral band as a result of a first color filter of the imaging system allowing at least a portion of the first spectral band to enter the imaging system and preventing at least a portion of the second spectral band from entering the imaging system, such that a majority of intensity information in the first imaging data acquired within the first spectral band is derived from the first illumination; the received second imaging data is acquired within a second spectral band as a result of a second color filter of the imaging system allowing at least a portion of the second spectral band to enter the imaging system and preventing at least a portion of the first spectral band from entering the imaging system, such that a majority of intensity information in the second imaging data acquired within the second spectral band is derived from the second illumination; a receiving module, wherein the first illumination and the second illumination are incident on the imaging system through an imaging system polarizer of the imaging system according to polarization states of the reflected first illumination and the second illumination received by the imaging system after reflection from the subject's skin surface, such that the specularly reflected and diffusely reflected first illumination is incident on the imaging system and the diffusely reflected second illumination is incident on the imaging system; a determination module that determines information regarding specular reflection from the skin surface of the subject by comparing the first imaging data with the second imaging data; The subject is a person.

9. The apparatus of claim 8 , wherein the determination module determines a measure of skin radiance of the subject based on a comparison between the first imaging data and the second imaging data.

10. 10. The apparatus of claim 8 or 9, further comprising the imaging system and / or an illumination system providing the first illumination and the second illumination.

11. 11. The apparatus of claim 10, wherein the imaging system polarizer allows reflected first and second illumination with electric field components parallel to a polarization axis of the imaging system polarizer to enter the imaging system and prevents reflected first and second illumination with electric field components perpendicular to the polarization axis from entering the imaging system.

12. 12. The apparatus of claim 11, wherein the illumination system comprises an illumination system polarizer that polarizes the second illumination directed at the subject, a polarization axis of the imaging system polarizer being orthogonal to the polarization axis of the illumination system polarizer.

13. 13. The apparatus of claim 10, wherein the illumination system is such that the first illumination directed at the subject is unpolarized, or the illumination system comprises an additional illumination system polarizer that polarizes the first illumination directed at the subject such that the polarization state of the first illumination directed at the subject is orthogonal to the polarization state of the second illumination directed at the subject.

14. 14. The apparatus of claim 10, wherein the illumination system is configured to direct the first illumination and the second illumination toward the subject such that both specular and diffuse reflected components of the first illumination and the second illumination reflected from the skin surface of the subject are directed into the imaging system for internal injection according to the polarization states of the reflected first and second illumination.

15. the imaging system comprises at least one imaging device and an optical filter array, the optical filter array comprising the first color filter and the second color filter, the optical filter array comprising: passing at least a portion of the first spectral band into the imaging system through a first set of pixels of the at least one imaging device such that the majority of the intensity information in the first imaging data acquired within the first spectral band is derived from the first illumination; passing at least a portion of the second spectral band into the imaging system through a second, different set of pixels of the at least one imaging device such that the majority of the intensity information in the second imaging data acquired within the second spectral band is derived from the second illumination; 15. The apparatus according to claim 10, wherein the

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