Reducing flicker phenomenon of multiple light sources in images - Patents.com

Abstract

To provide a method for reducing a flicker effect of a plurality of light sources in an image captured with an imaging device, an imaging device, and a storage medium.SOLUTION: Provided is a method for reducing a flicker effect in multiple light sources (102-108) in an image (116) captured with an imaging device (112), wherein a lighting frequency associated with each of the multiple light sources (102-108) is detected and prioritized relative to a flicker effect in the image (116) to identify at least a first-prioritized lighting frequency and a second-prioritized lighting frequency. A first exposure-time factorization set is determined for the first-prioritized lighting frequency, and a second exposure-time factorization set is determined for the second-prioritized lighting frequency. An exposure time of the imaging device (112) is adjusted to an exposure time identified in the first exposure-time factorization set that matches, or aligns near-to-matching, an exposure time identified in the second exposure-time factorization set.SELECTED DRAWING: Figure 1

Description

[Background technology]

[0001] background Complementary metal oxide semiconductor (CMOS) sensors are commonly used in digital cameras and digital video cameras to generate images. Typically, a rolling shutter imaging process is used, in which a still or video frame is captured by exposing, sampling, and reading out the pixels sequentially, line by line, rather than all at once. Furthermore, each line of the image is sampled at a slightly different time, with a uniform exposure time.

[0002] Certain light sources powered by electrical alternating current (AC) exhibit a flicker phenomenon at certain AC frequencies, which, in combination with the rolling shutter of the CMOS sensor and exposure times that differ from the light flicker, causes the resulting image or video captured by the CMOS sensor to produce a noticeable banding or flickering effect in the recorded image, typically in the form of dark or shadowed zebra-like lines across the image, or dark moving lines across the video recording. Summary of the Invention [Means for solving the problem]

[0003] overview Described herein are exemplary imaging devices, systems, and methods for reducing light emission flickering from multiple artificial light sources with different light emission (e.g., blinking) frequencies in captured images. For example, in areas where artificial light is used, such as homes, shopping malls, offices, restaurants, etc., it is common for multiple light sources to be present with different light emission frequencies. For example, many traditional incandescent and fluorescent lamps are aligned with the power frequency (50 / 60 Hz sine wave, 100 / 120 Hz in the energy domain, 100 Hz in Europe, etc.), and most LED (Light Emitting Diode) light sources have higher frequencies. By detecting the light emission frequencies of these multiple light sources, the one that is more detrimental to image quality is identified, and multiple steps are taken to control the exposure time of the imaging device's CMOS sensor. This reduces or eliminates banding, flickering, or flicker artifacts (collectively referred to as "flickering") in captured images. Flickering typically appears as dark or shadowed zebra-like lines across an image, or dark moving lines across a video recording.

[0004] An exemplary method for reducing flickering of a plurality of light sources in an image captured by an imaging device includes first detecting a light emission frequency for each of the plurality of light sources. The light emission frequencies of the light sources are then prioritized with respect to the flickering of the image to identify at least a first prioritized light emission frequency and a second prioritized light emission frequency. A first exposure time factorization set for the first prioritized light emission frequency is determined, and similarly, a second exposure time factorization set for the second prioritized light emission frequency is determined. The exposure time of the imaging device is then adjusted such that the exposure times in the first exposure time factorization set match or nearly match (e.g., if there is no exact match) the exposure times in the second exposure time factorization set.

[0005] Exemplary systems and methods for addressing the flicker phenomenon from multiple light sources in an image captured by an imaging device will now be described with reference to the accompanying drawings, in which identical reference numbers refer to the same or similar components throughout. [Brief description of the drawings]

[0006] [Figure 1] 1 illustrates an example of an imaging device configured to reduce light emission flicker from multiple light sources in a captured image. [Diagram 2] 4 is a flow chart illustrating an exemplary method for reducing light emission flicker from multiple light sources in an image captured by an imaging device. [Diagram 3] 4 is a flowchart illustrating operations, data, inputs, and outputs of an exemplary method for reducing light emission flicker from multiple light sources in an image captured by an imaging device. [Figure 4] 1 is a flowchart illustrating the operations and calculations of an exemplary method for determining an exposure time factorization set for adjusting the exposure time of an image capture device to reduce the phenomenon of luminescence flicker from multiple light sources in a captured image. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Detailed Description FIG. 1 is a block diagram illustrating an example of an imaging device configured to reduce or eliminate light flickering from multiple light sources in captured images. Light sources 1-N at 102, 104, 106, and 108 may be present in a typical artificially lit environment, such as a home, business, or other structure, where a person may be interested in taking a picture (e.g., capturing an image) of a person, object, or scene 110. Each light source 102-108 may flicker at a different light emission frequency. A person taking an image may use any type of device incorporating a digital camera or digital video camera, as represented by imaging device 112. As some non-limiting examples, imaging device 112 may be a mobile phone 112-1, a tablet terminal 112-2, or a digital video camera or digital camera 112-3. Imaging device 112 may include hardware, software, and functionality for reducing flickering from multiple light sources 102-108 in captured images.

[0008] The imager 112 may include a standard CMOS chip 114 using rolling shutter technology to capture an image 116 of the scene 110 through a camera lens 118. The imager 112 may also include a dedicated hardware light frequency sensor 118, a processor 120, and a memory 122. The imager 112 may also include other hardware components, such as, for example, an Application Specific Integrated Circuit (ASIC). The memory 122 is a machine-readable medium (e.g., a computer / processor readable medium) configured to store data and / or programming instructions executable by one or more processors. For example, the memory 122 may be a random-access memory (RAM), a read-only memory (ROM), a flash memory, a cache memory, or a solid-state drive (SSD). The memory 122 includes data and / or programming instructions executable by the processor 120 to reduce or eliminate flickering from the multiple light sources 102-108 in the captured image 116. Reducing or eliminating the flicker phenomenon reduces potential dark or shadowed zebra-like lines across the image 116, or dark moving lines across a video recording of a scene.

[0009] The memory 122 includes a flicker elimination manager 124 configured to reduce or eliminate flicker artifacts from the multiple light sources 102-108 in the captured image 116. In this example, the flicker elimination manager 124 is described as an application defined by executable instructions (e.g., firmware or software) in the memory 122 for execution on the processor 120. However, the operations of the flicker elimination manager 124 may also be performed independently or by the processor 120 using an Application Specific Integrated Circuit (ASIC) and / or other hardware components. The data for the flicker elimination manager 124 may be implemented in whole or in part in combination with programming instructions that can be used to adjust the flicker elimination manager 124. Example data for the flicker elimination manager 124 may include exposure limits, frame rate limitations, and sensor hardware limitations for the imager 112, as set in the design specifications defined in the product documentation for the imager.

[0010] The flicker elimination manager 124 may include a frequency detection manager 126, a prioritization manager 128, a factorization manager 130, and an exposure manager 132. These manager modules are shown separately in the figures for illustrative purposes, but may be combined or further separated into additional modules according to design and functionality choices. The frequency detection manager 126 functions to detect the emission frequency of each of the multiple light sources 102-108 that may affect the quality of the image 116 captured by the CMOS 114. The frequency detection manager 126 may work in conjunction with a dedicated hardware light frequency sensor 118 to detect the light source frequency with high reliability.

[0011] The prioritization manager 128 prioritizes the emission frequencies of the light sources 102-108 with respect to the flicker phenomenon relative to the image quality of the image 116. From these prioritized emission frequencies, at least a first prioritized emission frequency and a second prioritized emission frequency are identified. A particular emission frequency of the light sources 102-108 is identified as a higher priority emission frequency if it produces a worse or more noticeable emission flicker phenomenon relative to the image quality of the resulting image 116 compared to the other emission frequencies. In other words, the emission frequency of the light source that is most likely to produce dark zebra-like stripes on the image 116 is higher prioritized as a primary emission frequency to address and reduce or eliminate those phenomena in the image. In this regard, the first prioritized emission frequency is identified as one that may produce a worse emission flicker phenomenon in the image 116 than the second prioritized emission frequency. Similarly, the second prioritized light emission frequency is identified as being more likely to cause a worse light emission flicker phenomenon in the image 116 than the third prioritized light emission frequency, and so on.

[0012] The factorization manager 130 may calculate a first exposure time factorization set for a first prioritized emission frequency, a second exposure time factorization set for a second prioritized emission frequency, a third exposure time factorization set for a third prioritized emission frequency, and so on. The exposure time factorization set is first calculated by matching the exposure time of the CMOS 116 to the emission frequency (e.g., fx) of the corresponding light source. Then, the set of exposure times for the emission frequency fx is defined as a multiple of the function 1 / fx. This set of exposure times defines a factorization set of exposure times for the emission frequency and is generated within the exposure limit of the imaging device. The exposure time factorization set specifies the multiple of the exposure time to be considered for the corresponding light source to reduce or eliminate the flicker phenomenon in the captured image 116.

[0013] The exposure manager 132 adjusts the exposure time of the imager such that a first exposure time in the first exposure time factorization set matches or nearly matches a second exposure time in the second exposure time factorization set. If a second exposure time in the second exposure time factorization set matches a first exposure time in the first exposure time factorization set, the matching second exposure time is selected. If there is no perfectly matching exposure time between the two sets, the exposure time of the imager is adjusted to an exposure time in the first exposure time factorization set that nearly matches an exposure time in the second exposure time factorization set. This can reduce and eliminate the luminescence flicker phenomenon of at least two luminescence frequencies with the highest priority in the image 116. The entire process adjusted by the flicker elimination manager 124 is carried out for the multiple light sources 102-108. This may be repeated for each light source 102-108 and their respective frequencies to ensure reduced flickering in the resulting image 116.

[0014] FIG. 2 is a flow diagram showing an example of a method 200 for reducing or eliminating the phenomenon of light emission flicker from multiple light sources in an image captured by an imaging device. At 202, a light emission frequency that may affect the captured image is detected for each of the multiple light sources. One example of a method for detecting the light emission frequency is to calculate the light emission frequency by counting the occurrence of a luminance change pattern in a known exposure time using captured image frames. This method is effective for simple scenes. However, the change in brightness of the light may be presented as a pulse wave or a sine wave, so the change in brightness is not always easy to identify. Furthermore, due to the exposure time and the scanning speed of the rolling shutter, the resolution of the light emission frequency may be limited as well as the frequency range. Furthermore, the content of the frame may mislead the change in brightness if the change in brightness is not uniform, making it difficult to detect even if a zebra-like pattern is present in a particular area. Therefore, additional methods may be used to detect the light emission frequency, either alone or in combination with counting the occurrence of a brightness change pattern in a known exposure time.

[0015] Another exemplary method of detecting the emission frequency is to use a dedicated hardware light frequency sensor other than the standard image sensor of the imager, which may expose the light source at a very high frequency (e.g., due to the Nyquist-Shannon sampling theorem). In this regard, if the data acquisition of the image is performed over a reasonable period of time, the sensor can detect a very wide range of emission frequencies with high resolution. Furthermore, fast Fourier processing may also be utilized to calculate the emission frequency and intensity, or additional calculations may be applied, for example, by using a time filter.

[0016] At 204, the emission frequencies of each of the multiple light sources are prioritized with respect to flickering to the image to identify at least a first prioritized emission frequency and a second prioritized emission frequency. Emission frequencies that increase flickering to the image (e.g., dark zebra-like lines on the image) are assigned a higher priority than other emission frequencies. Prioritization is necessary because each light source may transmit a respective emission frequency, and in order to reduce flickering as much as possible from all frequencies, the exposure time must be long enough to cover the greatest common denominator. However, if this exposure time is too long, it may result in an overexposed image. For this reason, the emission frequencies are prioritized to identify those that have the most impact on image quality. The higher prioritized frequencies are addressed first to improve image quality over other emission frequency effects.

[0017] An exemplary metric and method for prioritizing emission frequencies introduced by a particular light source that may affect image quality is shown in function statement (A) below.

[0018] (A) h=c 1 ×M(f)+c 2 ×P(f)+c 3 ×R(f) where h is the resulting relative priority value and c i are the weights of each metric function described herein, and f is the detected frequency. These three metric terms represent the impact on image quality.

[0019] The first metric term of the function statement (A) is defined by the following statement (A1). (A1) M(f) This refers to a measure of the strength (e.g., magnitude) of the lighting frequency signal. The stronger the signal, the greater its impact on image quality.

[0020] Although M(f) may be used as a single metric, in practice, given a constant exposure time, the higher the energy cycle of the light source, the less noticeable the flicker or banding phenomena may be.

[0021] Therefore, the second metric term of the function statement (A) is introduced. The second metric term is the power cycle function of the emission frequency P(f), expressed in a normalized way in statement (A2) below.

[0022] (A2) P(f)=1 / f This means that the higher the frequency, the more power cycles can fit into the captured frame and are therefore less likely to affect image quality.

[0023] Another factor that can cause the flicker phenomenon to persist in video capture or preview is the rolling effect (dark stripes moving across the video recording). This is because if the flicker frequency, like the frame rate, is not matched with the exposure time, the preview or video capture will be even worse in terms of image quality as stripes will move across the frame. Furthermore, such movements may be considered as motion in image-based motion measurement, resulting in more exposure changes (e.g., more likely to shorten the exposure time to reduce motion blur), which can further affect image quality.

[0024] From this observation, the third metric term in function statement (A) reflects the rolling effect R(f), as expressed in statement (A3) below.

[0025] (A3) R(f) = min(f%FR,(f+FR)%FR) In this function, FR means the frame rate of the image. The modulation depth (%) checks whether the frequency matches the frame rate and how big the shift is. If the difference is small, a slow shift is seen, and if the difference is large, a fast shift is seen.

[0026] Finally, these three metric terms (A1), (A2), and (A3) are combined into an overall metric, represented by function statement (A), which is used to measure and prioritize the impact of each of the emission frequencies of multiple light sources on the image captured by the imaging device.

[0027] At 206, a first exposure time factorization set is determined for the first prioritized emission frequency, and a second exposure time factorization set is determined for the second prioritized emission frequency. The exposure time factorization set is calculated by first matching the exposure time of the image capture device to the emission frequency of the corresponding light source. Then, a set of exposure times for that emission frequency is defined to include multiples of the function "1 / emission frequency". The exposure time factorization set specifies, for that corresponding light source, the multiples of exposure time that should be considered to reduce the flicker phenomenon in the captured image.

[0028] At 208, the exposure time of the imager is now adjusted to an exposure time in the first exposure time factorization set that matches or nearly matches an exposure time in the second exposure time factorization set, thereby reducing or eliminating the light emission flicker phenomenon of the at least two most highly prioritized light emission frequencies in the resulting image. This process of prioritizing light emission frequencies at 204, determining an exposure time factorization set at 206, and adjusting the exposure time of the imager at 208 may be performed for additional light sources of the detected multiple light sources to reduce flicker for the multiple light sources and improve image quality.

[0029] FIG. 3 is a flow chart 300 showing high level operations, data, inputs, and outputs of an exemplary method for reducing flickering from multiple light sources in images captured by an imaging device. At 302, data identifying product specification information for an imaging device related to imaging capabilities, limitations, and capabilities is received as input data. For example, data defining frame rate limitations and sensor hardware limitations is received. This data is useful for operating within the limitations of the imaging device to reduce flickering in images captured by the imaging device. At 304, exposure limits for the imaging device are identified from the product specification input data. Exposure limits for the imaging device are typically set by design specifications for the imaging device's product description. These limits are preferably stored as imaging device parameter data, but may be obtained via other linking and networking functions. These limits are used to define boundaries for the exposure time of the imaging device, such that the exposure time factorization set (discussed and calculated elsewhere herein) is also limited by the imaging device's limits. At 306, the identified exposure limits are output for subsequent reference in determining an exposure time factorization set for reducing flickering in images.

[0030] Input data is obtained at 308 identifying detected emission frequencies of a plurality of light sources that may affect the quality of an image captured by the imaging device. The detected emission frequencies are prioritized with respect to flicker phenomena on an image captured by the imaging device at 310. At least a first prioritized emission frequency and a second prioritized emission frequency are identified and output at 312 for subsequent use to reduce flicker phenomena in the image.

[0031] At 314, a current exposure time and gain associated with an image capture device for capturing an image is obtained. At 316, an exposure time factorization set is determined for the previously identified prioritized emission frequencies. At least a first exposure time factorization set is determined for the first prioritized emission frequency and a second exposure time factorization set is determined for the second prioritized emission frequency. The exposure time factorization sets are determined for the current exposure time and gain, the prioritized emission frequencies, and the previously determined exposure limit.

[0032] At 318, a current exposure time of the imager is matched to an exposure time in the first exposure time factorization set that matches or nearly matches an exposure time in the second exposure time factorization set, thereby adjusting the exposure time of the imager to capture an image with reduced flicker for at least the first prioritized and second prioritized emission frequencies of the plurality of light sources, as well as other calculated prioritized frequencies.

[0033] 4 is a flow chart illustrating the operations and calculations of an exemplary method 400 for determining an exposure time factorization set for an image capture device. These exposure time factorization sets are referenced to adjust the exposure time of the image capture device to reduce or eliminate flicker phenomena from multiple light sources in the captured image. In this example, exposure time factorization sets for two light emission frequencies (e.g., two light sources) are shown, but similar procedures may be repeated for a third or additional light source and respective light emission frequencies.

[0034] At 402, input parameters for determining an exposure time factorization set are identified. These input parameters include prioritized emission frequencies for each of the multiple light sources, and at least a first prioritized emission frequency and a second prioritized emission frequency. The emission frequencies are f 1 and f 2 and f 1 has higher priority. This is because 1 F 2 The current exposure time and gain of the image capturing device for capturing an image are respectively determined to be larger than the input data t in and g in It is expressed as:

[0035] In 404, the output parameters from which the exposure time and gain of the image capture device are calculated are denoted by t out and g out These represent the final values ​​of the matched (e.g., adjusted) exposure time and gain, respectively, after the emission frequencies have been prioritized, the exposure times have been factored, and the appropriately adjusted exposure time values ​​have been selected as follows:

[0036] At 406, constraints on the imaging device are identified. These constraints reflect information and data that should be considered to ensure that a suitable factorized set of exposure times is calculated to effectively reduce flicker phenomena in the image. As an example, assume the following definitions (B) and (C) for the exposure limits:

[0037] (B) Maximum and minimum exposure times: t max and t min (C) Maximum and minimum gain: g max and g min Also, assuming the same total exposure value is maintained to ensure adequate light for the image, this is expressed by the following function (D):

[0038] (D) t out ×g out =t in ×g in Furthermore, general constraints on exposure, e.g., frame rate and sensor hardware (HW) constraints, remain the same and are expressed by the following functions (E) and (F):

[0039] (E) t out ≦t max && t out ≧t min (F) g out ≦g max && g out ≧g min Now, in 408, the goal of this process is to reduce or eliminate as much as possible the flicker phenomenon in the captured image. In this sense, the first step is to divide the exposure time by the frequency f of the primary light source. 1 And the exposure time is 1 / f 1 Multiple of By changing it to f 1 For example, if the initial exposure time is 50 milliseconds (ms) and the gain is 2x, then the total exposure is expressed as the following function (G):

[0040] (G) 50ms x 2 = 100ms For example, the first light source frequency f 1 is 100 Hz, then the primary gap (e.g., flicker frequency for exposure) is 1000 ms÷100 Hz=10 ms / cycle (e.g., 10 milliseconds / cycle). Thus, a first exposure time factorization set for reducing or eliminating the flicker phenomenon in the captured image for the first prioritized emission frequency is defined as [10 ms, 20 ms, 30 ms, 40 ms, 100 ms].

[0041] Next, the second light source frequency f2 is corrected. For example, the second light source frequency f 2is 70 Hz, then the primary gap is 1000 ms÷70 Hz=14.2 ms / cycle. As a result, a second exposure time factorization set to reduce or eliminate the flicker phenomenon in the captured image for the second prioritized emission frequency is defined as [14.2 ms, 28.4 ms, 42.6 ms, 56.8 ms...99.4 ms].

[0042] Next, f 1 The second light source frequency f 2 To find the best fit to 1 From n / f 1 Adjust until the second exposure time factorization If an exposure time in the first exposure time factorization set matches an exposure time in the first exposure time factorization set, the matching exposure time is selected. If there is no exact match between the two sets, the exposure time of the imager is adjusted to an exposure time in the first exposure time factorization set that approximately matches an exposure time in the second exposure time factorization set. 2 Search for a factorization set of f 1 Find a frequency gap that matches or nearly matches a frequency gap in the factorization set of f 2 The 28.4 and 99.4 in the second exposure time factorization set of 1 The first exposure time factorization set of 30 and 100 is almost the same. However, the first emission frequency f 1 The exposure time of 100 ms in the first exposure time factorization set of 2 In this way, the exposure time of the imager is selected to be 100 ms, which more effectively reduces or eliminates the luminance flicker phenomenon of both light sources in the resulting image.

[0043] In 410, the full function statement for determining these exposure time factorization sets and adjusting the output exposure of the image capture device to reduce the flicker phenomenon in the captured image is expressed as the following functions (H), (I), (J), and (K):

[0044]

number

[0045] The operations and methods described herein may be embodied in programming instructions executable by one or more processors in a computing device or system, alone or in combination with hardware blocks in a computing device or system, for example, with respect to methods 200, 300, and 400. Such programming instructions may be stored in a machine-readable medium (e.g., a computer / processor-readable medium) including a non-transitory random access memory (RAM), or cache memory, for execution on one or more processors of one or more computing devices. Instead of or in combination with a non-transitory machine-readable medium, the programming instructions may be stored in other machine-readable media, such as, for example, a read-only memory (ROM), a flash memory, a solid-state drive (SSD), a hard disk drive (HDD), a compact disc (CD), a jump drive, or a combination thereof.

[0046] The exemplary methods described in this disclosure may include multiple implementations, and different implementations of the methods may not employ all of the operations shown in the respective flow diagrams, or may employ additional operations not shown. Moreover, although the operations of the methods are presented in a particular order within the flow diagrams, the order of presentation is not intended to be limiting with respect to the order in which the operations may actually be performed, or with respect to whether any, some, or all of the operations may be performed. For example, one implementation of the method may be achieved by performing some initial operations without performing subsequent operations, while another implementation of the method may be achieved by performing more or all of the operations.

[0047] While the present disclosure has been described in terms of the exemplary embodiments outlined above, it is apparent that alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, the described and depicted embodiments of the present disclosure are intended to be illustrative rather than limiting, and the subject matter of the following claims will not necessarily be limited to the particular features or methods described in the present disclosure.

[0048] In the following sections, examples are provided. Example 1: A method for reducing a flicker phenomenon of a plurality of light sources (102-108) in an image (116) captured by an imaging device (112), comprising: detecting an emission frequency for each of at least two of the plurality of light sources (102-108); and prioritizing the emission frequencies of each of the at least two of the plurality of light sources (102-108) with respect to the flicker phenomenon in the image (116), wherein the prioritizing step includes prioritizing to identify at least a first prioritized emission frequency and a second prioritized emission frequency, determining a first exposure time factorization set for the first prioritized emission frequency and a second exposure time factorization set for the second prioritized emission frequency, and further comprising adjusting an exposure time of the imaging device (112) to a first exposure time in the first exposure time factorization set that matches at least one of the matching or nearly matching second exposure times in the second exposure time factorization set.

[0049] Example 2: The method described in Example 1, wherein the step of detecting the light emission frequency includes at least one of the following steps, or a combination thereof: counting the occurrence of a pattern of brightness changes at a known exposure time, using a dedicated light frequency sensor, utilizing fast Fourier processing, and using a time filter.

[0050] Example 3: A method as described in any one of the preceding examples, wherein the step of prioritizing the light emission frequencies includes a step of referring to a metric function of at least one of the intensity of the light emission frequencies, a power cycle function of the light emission frequencies, a rolling shutter effect of the imaging device, and a frame rate of imaging of the imaging device, or a combination thereof.

[0051] Example 4: A method as described in any one of the preceding examples, wherein a first prioritized emission frequency is identified as causing an increased flicker phenomenon in an image compared to a second prioritized emission frequency.

[0052] Example 5: A method according to any one of the preceding examples, wherein the step of determining a first exposure time factorization set includes a step of identifying a first exposure time effective for reducing the flicker phenomenon of a first prioritized emission frequency in the image, and a step of identifying a first set of exposure times including a step of processing a multiple of a function calculated for the first exposure time, and the step of determining a second exposure time factorization set includes a step of identifying a second exposure time effective for reducing the flicker phenomenon of a second prioritized emission frequency in the image, and a step of identifying a second set of exposure times including a step of processing a multiple of a function calculated for the second exposure time.

[0053] Example 6: A method as described in any one of the preceding examples, further comprising a step of determining a first exposure time factorization set within the exposure limits of the imaging device, the exposure limits being determined by at least one of a step of maintaining the calculated total exposure value for the exposure time and gain value for the first prioritized light emission frequency the same, and a step of maintaining identified constraints among the exposure limits for the frame rate limitations and sensor hardware limitations of the imaging device.

[0054] Example 7: A method according to any one of the preceding examples, further comprising the steps of prioritizing the emission frequencies of at least two of the plurality of light sources to identify at least a third prioritized emission frequency, determining a third exposure time factorization set for the third prioritized emission frequency, and adjusting the exposure time of the imaging device to a first exposure time of the first exposure time factorization set that matches at least one of the matching or nearly matching second exposure times in the second exposure time factorization set and at least one of the matching or nearly matching third exposure times in the third exposure time factorization set.

[0055] Example 8: An imaging device configured to perform the method according to at least one of Examples 1 to 7.

[0056] Example 9: A machine-readable storage medium storing instructions that, when executed by at least one processor, cause the at least one processor to perform a method described in at least one of Examples 1 to 7.

Claims

1. 1. A method comprising: detecting an emission frequency for each of at least two of the plurality of light sources; prioritizing the emission frequencies of each of the at least two of the plurality of light sources to identify at least a first prioritized emission frequency and a second prioritized emission frequency; determining a first exposure time factorization set for the first prioritized emission frequencies and a second exposure time factorization set for the second prioritized emission frequencies based on an exposure limit of an imaging device; and instructing the imaging device to capture an image with an adjusted exposure time, the adjusted exposure time being an exposure time in the first exposure time factorization set that matches at least one of the matching or nearly matching exposure times in the second exposure time factorization set; the first exposure time factorization set includes a set of inverse multiples of the first prioritized emission frequency, and the second exposure time factorization set includes a set of inverse multiples of the second prioritized emission frequency.

2. The method of claim 1 , further comprising identifying an exposure limit of the image capture device prior to detecting the emission frequency for each of the at least two of the plurality of light sources.

3. The method of claim 1 or 2, wherein prioritizing the emission frequencies of each of the at least two of the plurality of light sources is based on a flicker phenomenon in an image captured by the imaging device.

4. 4. The method of claim 1, further comprising the step of determining a current exposure time of the imaging device for capturing an image prior to the step of determining the first exposure time factorization set for the first prioritized emission frequency and the second exposure time factorization set for the second prioritized emission frequency.

5. 5. The method of claim 1, wherein detecting the light emission frequency comprises at least one of, or a combination of, counting occurrences of a luminance change pattern at a known exposure time, using a dedicated light frequency sensor, utilizing Fast Fourier Processing, and using a temporal filter.

6. The method of any one of claims 1 to 5, further comprising the step of imaging with the adjusted exposure time, wherein said imaging step uses a rolling shutter technique.

7. 7. The method of claim 1, wherein the step of prioritizing the emission frequencies is based on a metric function of at least one of the following: intensity of the emission frequencies, a power cycle function of the emission frequencies, a rolling shutter effect of the imager, and an imaging frame rate of the imager, or a combination thereof.

8. The method of any one of claims 1 to 7, wherein identifying the exposure limit of the imaging device comprises reading the exposure limit from an internal memory of the imaging device.

9. 9. The method of claim 8, further comprising outputting the exposure limits of the imaging device for subsequent reference in determining the first and second exposure time factorization sets.

10. The method of any one of claims 1 to 9, wherein the first exposure time factorization set and the second exposure time factorization set are constrained by the exposure limit of the imaging device.

11. determining a current gain of the imaging device for capturing an image; 11. The method of claim 1, wherein the first exposure time factorization set and the second exposure time factorization set are determined based on the exposure limit of the imager, a current exposure time of the imager, and the current gain of the imager.

12. 1. An imaging device, comprising: At least one processor; and a computer-readable medium containing instructions that, when executed by the at least one processor, cause the at least one processor to: Detecting an emission frequency for each of at least two of the plurality of light sources; prioritizing the emission frequencies of each of the at least two of the plurality of light sources to identify at least a first prioritized emission frequency and a second prioritized emission frequency; determining a first exposure time factorization set for the first prioritized emission frequencies and a second exposure time factorization set for the second prioritized emission frequencies based on an exposure limit of the imaging device; adjusting a current exposure time of the image capture device to an adjusted exposure time, the adjusted exposure time being an exposure time in the first exposure time factorization set that matches at least one of the matching or nearly matching exposure times in the second exposure time factorization set; an imaging device, wherein the first exposure time factorization set includes a set of inverse multiples of the first prioritized light emission frequency, and the second exposure time factorization set includes a set of inverse multiples of the second prioritized light emission frequency.

13. The instructions further include causing the at least one processor to: The imaging device of claim 12 , further comprising: determining an exposure limit of the imaging device prior to detecting the emission frequencies for each of the at least two of the plurality of light sources.

14. 14. The imaging device of claim 12 or 13, wherein prioritizing the emission frequencies of each of the at least two of the plurality of light sources relates to a flicker phenomenon in an image captured by the imaging device.

15. The instructions further include causing the at least one processor to:

15. The imaging device of claim 12, further comprising: determining the current exposure time of the imaging device for capturing an image before determining the first exposure time factorization set for the first prioritized light emission frequency and the second exposure time factorization set for the second prioritized light emission frequency.

16. The imaging device of any one of claims 12 to 15, wherein the imaging device uses a rolling shutter technique to capture an image.

17. The imaging device of any one of claims 12 to 16, wherein the first exposure time factorization set and the second exposure time factorization set are constrained by the exposure limit of the imaging device.

18. The imaging device according to any one of claims 12 to 17, wherein the imaging device includes at least one of a digital camera and a digital video camera, or a combination thereof.

19. 1. A program storing instructions that, when executed by at least one processor, cause the at least one processor to: Detecting an emission frequency for each of at least two of the plurality of light sources; prioritizing the emission frequencies of each of the at least two of the plurality of light sources to identify at least a first prioritized emission frequency and a second prioritized emission frequency; determining a first exposure time factorization set for the first prioritized emission frequencies and a second exposure time factorization set for the second prioritized emission frequencies based on an exposure limit of an imaging device; adjusting a current exposure time of the image capture device to an adjusted exposure time, the adjusted exposure time being an exposure time in the first exposure time factorization set that matches at least one of the matching or nearly matching exposure times in the second exposure time factorization set; the first exposure time factorization set includes a set of inverse multiples of the first prioritized light emission frequency, and the second exposure time factorization set includes a set of inverse multiples of the second prioritized light emission frequency.

20. 20. The computer-readable medium of claim 19, wherein prioritizing the light emission frequencies of each of the at least two of the plurality of light sources relates to a flicker phenomenon in an image captured by the imaging device.

21. The program further includes instructions that, when executed by the at least one processor, cause the at least one processor to:

21. The program of claim 19 or 20, further comprising determining the current exposure time of the imaging device for capturing an image before determining the first exposure time factorization set for the first prioritized emission frequency and the second exposure time factorization set for the second prioritized emission frequency.

22. The program further includes instructions that, when executed by the at least one processor, cause the at least one processor to:

22. The program of claim 19, further comprising: outputting the exposure limits of the imaging device for subsequent reference in determining the first exposure time factorization set and the second exposure time factorization set.

23. The program of claim 19, wherein the first exposure time factorization set and the second exposure time factorization set are limited by the exposure limit of the imaging device.

24. The program further includes instructions that, when executed by the at least one processor, cause the at least one processor to: determining a current gain of the imaging device for capturing an image; The program of any one of claims 19 to 23, wherein the first exposure time factorization set and the second exposure time factorization set are determined based on the exposure limit of the imaging device, the current exposure time of the imaging device, and the current gain of the imaging device.

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