IR-cut filter switch control
AssigneeAxis AB
InventorsAxel Thuresson, Ola Synnergren
Life of this patent
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Abstract
A method of performing better controlled switching between day mode and night mode imaging in a camera, where those illuminants contributing to the ambient light in day mode are considered when determining the visible light during night mode. Characteristic values of those illuminants are mixed with several levels of IR light to simulate the presence of an IR illuminator, and these characteristic values are compared to corresponding values derived from the color components of the ambient light in night mode in order to determine the IR proportion, and from that the amount of visible light.
Claims14
A method, performed in a video camera, of controlling an infrared cut (IR-cut) filter of the video camera, to switch between day mode and night mode, wherein the camera comprises an image sensor having a color filter array configured to allow the sensor to sense different color components at different regions of the sensor, the method comprising:
- measuring, by the image sensor, an amount of ambient light received by the image sensor and color components of the ambient light received by the image sensor, wherein the color components are determined by calculating the sum or integrated amount of ambient light received by the image sensor within the specific wavelength intervals corresponding to the color components,
- when the video camera is in day mode,
- determining a set of illuminants present in the scene and contributing to the ambient light intensity, by comparing the color components of ambient light received by the image sensor to a first set of characteristic values in the form of color components contributions associated with different illuminants,
- when the amount of ambient light received by the image sensor is lower than a first threshold, switching to night mode, and
- when the camera is in night mode,
- obtaining a second set of characteristic values by mixing a wavelength spectrum of each illuminant in the determined set of illuminants with spectrums of several different levels of added IR light, such that the second set of characteristic values contains a plurality of characteristic values per illuminant, wherein the proportion of IR light per characteristic value in the second set comprises both IR light from the spectrum of the illuminant and from the spectrum of the added level of IR light,
- determining an IR light proportion of the ambient light received by the image sensor, by comparing the color components of ambient light received by the image sensor to the second set of characteristic values in the form of color component contributions associated with different IR light proportions,
- determining a visible light intensity based on the determined IR light proportion and the amount of ambient light received by the image sensor,
- when the visible light intensity is higher than a second threshold, switching to day mode.
A video camera comprising:
- an image sensor having a color filter array configured to allow the sensor to sense different color components at different regions of the sensor, wherein the image sensor is configured to measure an amount of ambient light received by the image sensor and color components of the ambient light received by the sensor, wherein the color components are determined by calculating the sum or integrated amount of ambient light received by the sensor within specific wavelength intervals corresponding to the color components, and
- an infrared cut (IR-cut) filter which is configured to be controlled by the camera to switch between day mode and night mode,
- wherein the camera is configured to,
- when the camera is in day mode,
- determine a set of illuminants present in the scene and contributing to the ambient light intensity, by comparing the color components of ambient light received by the image sensor to a first set of characteristic values in the form of color components contributions associated with different illuminants,
- when the amount of ambient light intensity is lower than a first threshold, switch to night mode,
- when the camera is in night mode,
- obtain a second set of characteristic values by mixing a wavelength spectrum of each illuminant in the determined set of illuminants with spectrums of several different levels of added IR light, such that the second set of characteristic values contains a plurality of characteristic values per illuminant, wherein the proportion of IR light per characteristic value in the second set comprises both IR light from the spectrum of the illuminant and the spectrum of the added level of IR light,
- determine an IR light proportion of the ambient light received by the image sensor, by comparing the color components of ambient light received by the image sensor to a second set of characteristic values in the form of color component contributions associated with different IR light proportions,
- determine a visible light intensity based on the determined IR light proportion and the amount of ambient light received by the image sensor,
- when the visible light intensity is higher than a second threshold, switch to day mode.
A non-transitory computer readable storage medium having stored thereon instructions for implementing a method, when executed on a device having processing capabilities, the method, performed in a video camera, of controlling an infrared cut (IR-cut) filter of the video camera, to switch between day mode and night mode, wherein the camera comprises an image sensor having a color filter array configured to allow the sensor to sense different color components at different regions of the sensor, the method comprising:
- measuring, by the image sensor, an amount of ambient light received by the image sensor and color components of the ambient light received by the image sensor, wherein the color components are determined by calculating the sum or integrated amount of ambient light received by the image sensor within specific wavelength intervals corresponding to the color components,
- when the camera is in day mode,
- determining a set of illuminants present in the scene and contributing to the ambient light intensity, by comparing the color components of ambient light received by the image sensor to a first set of characteristic values in the form of color components contributions associated with different illuminants,
- when the amount of ambient light received by the image sensor is lower than a first threshold, switching to night mode, and
- when the camera is in night mode,
- obtaining a second set of characteristic values by mixing a wavelength spectrum of each illuminant in the determined set of illuminants with spectrums of several different levels of added IR light, such that the second set of characteristic values contains a plurality of characteristic values per illuminant, wherein the proportion of IR light per characteristic value in the second set comprises both IR light from the spectrum of the illuminant and from the spectrum of the added level of IR light,
- determining an IR light proportion of the ambient light received by the image sensor, by comparing the color components of ambient light received by the image sensor to the second set of characteristic values in the form of color component contributions associated with different IR light proportions,
- determining a visible light intensity based on the determined IR light proportion and the amount of ambient light received by the image sensor,
- when the visible light intensity is higher than a second threshold, switching to day mode.
Dependencies are inferred from the claim text.