Camera supporting color temperature detection

Abstract

A camera supporting color temperature detection disclosed by the present invention comprises a lens, a base, an infrared optical filter and a circuit board, the circuit board is provided with an image sensor, and the image sensor comprises a first optical filter array, a photodiode array, a sampling and processing circuit and a second optical filter array. The first optical filter arrays and the second optical filter arrays are installed above the photodiode array side by side, the second optical filter arrays are located at edge pixels of the first optical filter arrays, the photodiode array is connected with the sampling and processing circuit and outputs signals to the sampling and processing circuit, a separation area is arranged between every two sets of second optical filter arrays, and the separation area is located between every two sets of second optical filter arrays. An external detection light source enters the second optical filter array, other spectrums are filtered out, then the external detection light source enters the photodiode array and is converted into electric signals, the electric signals are sampled and processed by the sampling and processing circuit to obtain irradiation brightness of different spectrums of the external detection light source, and the color temperature of the external detection light source is obtained through calculation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of image processing, and in particular to a camera supporting color temperature detection. BACKGROUND

[0002] Traditional cameras usually use the gray world method and the white color block method and their improved algorithms to estimate the color temperature of the scene being photographed, but these algorithms based on assumptions have inherent defects in the face of actual complex light sources, and many times it is difficult to accurately evaluate the color temperature, resulting in obvious distortion of the color of the photographed image.

[0003] The human eye has the function of color constancy, that is, it can automatically identify various colors under different lighting conditions and is not affected by color temperature. However, CCD / CMOS image sensors do not have this function, and the scene in the photographed image will appear color cast under different color temperature lighting, with blue color cast under high color temperature lighting and red or yellow color cast under low color temperature lighting. This requires an automatic white balance (AWB) function to make the color of an image closer to the natural color observed by the human eye.

[0004] Automatic white balance (AWB) is a technology used in imaging devices such as cameras to automatically adjust the color of an image so that it can accurately present white under different color temperature light sources.

[0005] There are currently two main ways of AWB: the gray world method and the white color block method, as well as subsequent improved algorithms based on these two assumptions of the scene. The advantage of these two algorithms is low cost and low algorithm complexity, making them easy to implement. However, these two algorithms are based on assumptions, and for actual complex light sources, many times it is difficult to accurately evaluate the color temperature, resulting in obvious distortion of the color of the camera.

[0006] Currently, high-end mobile phones use dedicated color temperature sensors to measure the spectral distribution of the light source using a spectral sensor, calculate the color temperature of the light source based on the relationship between the spectral energy distribution and the color temperature, and then adjust the white balance parameters of the camera according to the color temperature value to accurately restore the color of the image. This method has high precision, but requires additional spectral measurement equipment, has high cost, and has high requirements for hardware. SUMMARY

[0007] In view of the above deficiencies in the current image processing technology field, the present application provides a camera supporting color temperature detection, which can significantly improve the accuracy of color temperature detection in complex light source environments, and can significantly reduce the use cost compared to the additional independent color temperature sensor, having good performance and cost advantage.

[0008] To achieve the above purpose, the embodiments of the present application adopt the following technical solutions:

[0009] A camera supporting color temperature detection for detecting color temperature of an external detection light source, comprising a lens, a base, an infrared filter and a circuit board, the lens and the infrared filter being installed in the base, the circuit board being located below the base, the circuit board further being provided with an image sensor, the image sensor comprising a first filter array, a photodiode array and a sampling and processing circuit, the image sensor further being provided with a plurality of groups of second filter arrays, the first filter array and the second filter array being installed side by side above the photodiode array, the second filter array being located at an edge pixel of the first filter array, the photodiode array being connected to and outputting a signal to the sampling and processing circuit, and a space being provided between each group of second filter arrays.

[0010] According to an aspect of the present application, the first filter array is arranged as a Bayer filter array, and the second filter array is arranged as a 380-730nm multi-row bandpass filter array, the external detection light source entering the second filter array and being filtered of other spectra, entering the photodiode array and being converted into an electrical signal, and the irradiance of different spectra of the external detection light source being obtained after sampling and processing by the sampling and processing circuit, and the color temperature of the external detection light source being calculated.

[0011] According to an aspect of the present application, each group of the second filter array is arranged with the same fixed number of rows and columns, the number of rows being at least 1 row, and the number of columns being at least 1 column, and each group of the second filter array being provided with the same fixed interval, the same fixed interval being at least 5 nanometers.

[0012] According to an aspect of the present application, the second filter array and the first filter array are provided with a space row, or are not provided with a space row.

[0013] According to an aspect of the present application, each group of the second filter array is provided with a space column, or is not provided with a space column.

[0014] According to an aspect of the present application, the irradiance of different spectra of the external detection light source is arranged as B(λ, T), the color temperature represented by absolute temperature is arranged as T, Planck's constant is arranged as h, the vacuum light speed is arranged as c, and the Boltzmann constant is arranged as k, and the irradiance of different spectra of the external detection light source is obtained as follows:

[0015]

[0016] According to an aspect of the present application, the pixel array signal is sequentially subjected to analog processing, analog-digital conversion, image processing color temperature estimation, and then output to a MIPI interface or a DVP interface.

[0017] According to one aspect of the present application, the signal of the configuration register controlling the timing control output is sequentially subjected to analog processing, analog-digital conversion, image processing and color temperature estimation, and then output to the MIPI interface or the DVP interface, or directly subjected to image processing and color temperature estimation, and then output to the MIPI interface or the DVP interface.

[0018] According to one aspect of the present application, the irradiance of different spectra of the external detection light source is calculated by the least square method, so that the error square sum between the calculated irradiance and the actual measured value is minimized, and the color temperature of the external detection light source is obtained.

[0019] According to one aspect of the present application, the fitted color temperature is set as T fit , and the spectral irradiance at wavelength λ i is set as B mea (λ i ), λ i is 36 wavelengths from 380nm to 730nm, and the least square fitting formula is:

[0020] min∑ i [B(λ i ,T fit )-B mea (λ i )] 2 .

[0021] The advantages of the present application are as follows: a Bayer filter array, a photodiode array, a sampling and processing circuit, and a 380-730nm multi-row bandpass filter array are included, the Bayer filter array and the 380-730nm multi-row bandpass filter array are installed side by side above the photodiode array, the 380-730nm multi-row bandpass filter array is located at the edge pixels of the Bayer filter array, the photodiode array is connected and outputs signals to the sampling and processing circuit, a space is provided between each 380-730nm multi-row bandpass filter array, the external detection light source enters the 380-730nm multi-row bandpass filter array and is filtered out of other spectra, enters the photodiode array and is converted into an electrical signal, and then is sampled and processed by the sampling and processing circuit to obtain the irradiance of different spectra of the external detection light source, and the color temperature of the external detection light source is calculated; the color temperature detection accuracy under complex light source environment can be greatly improved, compared with additional independent color temperature sensors, the use cost can be greatly reduced, and good performance and cost advantages are achieved. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art based on the drawings without any creative effort should be within the protection scope of the present application.

[0023] Figure 1 A structural schematic diagram of a camera supporting color temperature detection according to the present application;

[0024] Figure 2 A circuit structural schematic diagram of a camera supporting color temperature detection according to the present application;

[0025] Figure 3 A structural diagram of a second embodiment of a camera supporting color temperature detection according to the present application;

[0026] Figure 4 A layout schematic diagram of a camera supporting color temperature detection according to the present application;

[0027] Figure 5 An appearance schematic diagram of a camera supporting color temperature detection according to the present application.

[0028] Legend of reference signs:

[0029] 1, second filter array; 2, first filter array; 3, photodiode array; 4, sampling and processing circuit; 5, lens; 6, base; 7, infrared filter; 8, circuit board. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort should be within the protection scope of the present application.

[0031] Embodiment one:

[0032] As Figures 1 to 5As shown, a camera supporting color temperature detection includes a lens 5, a base 6, an infrared filter 7, a circuit board 8 and an image sensor supporting color temperature measurement. The lens 5 is embedded on the upper part of the base 6, the infrared filter 7 is located at the bottom of the base, the circuit board 8 is connected below the base 6, and the image sensor supporting color temperature measurement is arranged on the circuit board 8. The image sensor includes a first filter array 2, a photodiode array 3, a sampling and processing circuit 4 and a second filter array 1. In this embodiment, the first filter array 2 is arranged as a Bayer filter array, and the second filter array 1 is arranged as a 380-730nm multi-row bandpass filter array. The Bayer filter array and the 380-730nm multi-row bandpass filter array are installed side by side above the photodiode array 3, and the 380-730nm multi-row bandpass filter array is located at the edge pixels of the Bayer filter array. The photodiode array 3 is connected to and outputs signals to the sampling and processing circuit 4.

[0033] On the basis of the conventional Bayer array CMOS sensor, the original Bayer array is replaced by a 380-730nm multi-row bandpass filter array at the edge pixels of the CMOS sensor in this embodiment. According to the cost and detection accuracy requirements, the interval of the 380-730nm multi-row bandpass filter array is set to T nanometers, where T≥5. The smaller the interval, the more accurate the calculation of color temperature, but the higher the cost; on the contrary, the cost is low, and the accuracy is also low. In this embodiment, the interval T is set to 10nm, and 36 bandpass filters of 380, 390, 400, 410…700, 710, 720, 730nm need to be set.

[0034] As shown in Figure 4 Each spectrum is set to M rows and N columns, where M≥1 and N≥1. In order to reduce the crosstalk between adjacent different spectra, a space is arranged between each 380-730nm multi-row bandpass filter array. m empty rows are arranged between the 380-730nm multi-row bandpass filter array and the Bayer array, where m≥0; n empty columns are arranged between adjacent 380-730nm multi-row bandpass filter arrays, where n≥0.

[0035] According to the Planck's law formula, the radiation brightness of different spectra can be obtained:

[0036]

[0037] Where B(λ,T) is the spectral radiation brightness, T is the color temperature represented by absolute temperature, h is the Planck constant, c is the speed of light in vacuum, and k is the Boltzmann constant.

[0038] The external detection light source enters the 380-730nm multi-row bandpass filter array through the lens, filters out other spectra, enters the photodiode array 3 and is converted into an electrical signal, and then the sampling and processing circuit 4 processes the electrical signal to obtain the irradiance brightness B of the external detection light source of different spectra.mea (λ i By using optimization algorithms such as the least squares method to minimize the sum of squared errors between the theoretically calculated spectral radiance and the actual measured value, the color temperature of the external detection light source can be obtained.

[0039] The relevant formulas are as follows:

[0040] min∑ i [B(λ i ,T fit )-B mea (λ i ) 2

[0041] Among them, T fit It is the color temperature obtained through fitting, B mea (λ i ) is the wavelength λ i The spectral irradiance measured at λ i It has 36 wavelengths ranging from 380 to 730 nm.

[0042] In this embodiment, the CMOS sensor output resolution is selected as 1920*1080, and the effective pixel count is set to 1920*1088. A multi-row bandpass filter array ranging from 380-730nm is set in the first two rows. Each wavelength filter is configured with 52 columns * 2 rows, with a wavelength interval of 10nm, for a total of 36 wavelengths. The total number of bandpass filter array columns is 52 * 36 = 1872. To prevent crosstalk between different spectra, an empty column is set between filters of different spectra, for a total of 36 - 1 = 35 empty columns. Six empty columns are set in front of the bandpass filter array, and seven empty columns are set behind it, for a total of 1920 columns. Since each wavelength filter is configured with 52 columns * 2 rows, the total photosensitive area for each wavelength spectrum is very large, which can significantly improve the measurement sensitivity.

[0043] The advantages of the embodiment of the present application include a Bayer filter array, a photodiode array, a sampling and processing circuit, and a 380-730nm multi-row bandpass filter array, the Bayer filter array and the 380-730nm multi-row bandpass filter array are installed side by side above the photodiode array, the 380-730nm multi-row bandpass filter array is located at the edge pixels of the Bayer filter array, the photodiode array is connected and outputs signals to the sampling and processing circuit, a space is arranged between each 380-730nm multi-row bandpass filter array, after an external detection light source enters the 380-730nm multi-row bandpass filter array and is filtered to remove other spectra, the external detection light source enters the photodiode array and is converted into an electrical signal, and after sampling and processing by the sampling and processing circuit, the irradiation brightness of different spectra of the external detection light source is obtained, and the color temperature of the external detection light source is calculated; the color temperature detection accuracy under a complex light source environment can be greatly improved, compared with additional independent color temperature sensors, the use cost can be greatly reduced, and good performance and cost advantages are obtained.

[0044] Embodiment two

[0045] As shown in Figures 1 to 4 A CMOS sensor supporting color temperature detection includes a first filter array 2, a photodiode array 3, a sampling and processing circuit 4, and a second filter array 1. In this embodiment, the first filter array 2 is set as a Bayer filter array, and the second filter array 1 is set as a 380-730nm multi-row bandpass filter array. The Bayer filter array and the 380-730nm multi-row bandpass filter array are installed side by side above the photodiode array 3, the 380-730nm multi-row bandpass filter array is located at the edge pixels of the Bayer filter array, and the photodiode array 3 is connected and outputs signals to the sampling and processing circuit 4.

[0046] This embodiment is based on a conventional Bayer array CMOS sensor, and the original Bayer array is replaced with a 380-730nm multi-row bandpass filter array at the edge pixels of the CMOS sensor. According to the cost and detection accuracy requirements, the interval of the 380-730nm multi-row bandpass filter array is set to T nanometers, where T≥5. The smaller the interval, the more accurate the color temperature calculation, but the higher the cost; on the contrary, the cost is low, and the accuracy is also low. In this embodiment, the interval T is set to 10nm, and 36 bandpass filters of 380, 390, 400, 410…700, 710, 720, and 730nm need to be set.

[0047] As shown in Figure 4As shown, each spectrum is set as M rows and N columns, where M≥1 and N≥1. In order to reduce the crosstalk between adjacent different spectra, a space is arranged between each 380-730nm multi-row band-pass filter array. An m number of empty rows are arranged between the 380-730nm multi-row band-pass filter array and the Bayer array, where m≥0; and n number of empty columns are arranged between adjacent 380-730nm multi-row band-pass filter arrays, where n≥0.

[0048] According to the Planck's law formula, the radiation brightness of different spectra can be obtained:

[0049]

[0050] Wherein, B(λ, T) is the spectral radiation brightness, T is the color temperature represented by absolute temperature, h is the Planck constant, c is the speed of light in vacuum, and k is the Boltzmann constant.

[0051] The external detection light source passes through the lens into the 380-730nm multi-row band-pass filter array, and after filtering out other spectra, it enters the photodiode array 3 to be converted into an electrical signal. After being processed by the sampling and processing circuit 4, the irradiance brightness B mea (λ i ) of the external detection light source of different spectra is obtained. By using the least square method and other optimization algorithms, the sum of squares of errors between the theoretically calculated spectral radiation brightness and the actual measured value is minimized, and the color temperature of the external detection light source can be obtained.

[0052] The relevant formula is as follows:

[0053] min∑ i [B(λ i ,T fit )-B mea (λ i ) 2

[0054] Wherein, T fit is the fitted color temperature, B mea (λ i ) is the measured spectral irradiance at wavelength λ i , and λ i is 36 wavelengths from 380-730nm.

[0055] In this embodiment, the CMOS sensor output resolution is selected as 1920*1080, and the effective pixels are set as 1920*1088. Before starting, a 380-730nm multi-row bandpass filter array is arranged in the first two rows, each wavelength filter is arranged as 52 columns*2 rows, the wavelength interval is 10nm, there are a total of 36 wavelengths, the bandpass filter array is a total of 52*36=1872 columns, in order to prevent cross talk between different spectra, an empty column is arranged between different spectral filters, a total of 36-1=35 empty columns, 6 empty columns are arranged in front of the bandpass filter array, and 7 empty columns are arranged behind the bandpass filter array, a total of 1920 columns. Since each wavelength filter is arranged as 52 columns*2 rows, the total photosensitive area of each wavelength spectrum is large, which can greatly improve the measurement sensitivity.

[0056] The advantages of the embodiment of the present application include a Bayer filter array, a photodiode array, a sampling and processing circuit, and a 380-730nm multi-row bandpass filter array, the Bayer filter array and the 380-730nm multi-row bandpass filter array are installed side by side above the photodiode array, the 380-730nm multi-row bandpass filter array is located at the edge pixels of the Bayer filter array, the photodiode array is connected and outputs signals to the sampling and processing circuit, an empty area is arranged between each 380-730nm multi-row bandpass filter array, after an external detection light source enters the 380-730nm multi-row bandpass filter array and filters out other spectra, the external detection light source enters the photodiode array and is converted into an electrical signal, and then the external detection light source is obtained after sampling and processing by the sampling and processing circuit, the irradiation brightness of different spectra of the external detection light source is obtained, and the color temperature of the external detection light source is calculated; the color temperature detection accuracy under a complex light source environment can be greatly improved, compared with additional independent color temperature sensors, the use cost can be greatly reduced, and good performance and cost advantages are obtained.

[0057] Embodiment three

[0058] A color temperature detection method is realized based on the CMOS sensor supporting color temperature detection in embodiment two. The method comprises the following steps:

[0059] S1: install a Bayer filter array and a plurality of 380-730nm multi-row bandpass filter arrays above a photodiode array 3, connect the photodiode array 3 and output signals to a sampling and processing circuit 4, and arrange an empty area between each 380-730nm multi-row bandpass filter array;

[0060] S2: input an external detection light source into the 380-730nm multi-row bandpass filter array and filter out other spectra;

[0061] S3: input the external detection light source filtered out of other spectra into the photodiode array 3 and convert it into an electrical signal;

[0062] S4: the electrical signal is input to the sampling and processing circuit 4 for sampling and processing, and the irradiance of different spectra of the external detection light source is obtained;

[0063] S5: the irradiance of different spectra of the external detection light source is calculated by least square fitting, the error sum of squares between the calculated irradiance and the actual measured value is minimized, and the color temperature of the external detection light source is obtained.

[0064] The advantages of the embodiment of the present application are as follows: the Bayer filter array and the plurality of 380-730nm multi-row bandpass filter arrays are installed above the photodiode array, the photodiode array is connected and the signal is output to the sampling and processing circuit, and the empty area is arranged between each 380-730nm multi-row bandpass filter array; the external detection light source is input to the 380-730nm multi-row bandpass filter array, and other spectra are filtered out; the external detection light source with other spectra filtered out is input to the photodiode array and converted into an electrical signal; the electrical signal is input to the sampling and processing circuit for sampling and processing, and the irradiance of different spectra of the external detection light source is obtained; the irradiance of different spectra of the external detection light source is calculated by least square fitting, the error sum of squares between the calculated irradiance and the actual measured value is minimized, and the color temperature of the external detection light source is obtained; the color temperature detection accuracy under a complex light source environment can be greatly improved, compared with additional independent color temperature sensors, the use cost can be greatly reduced, and good performance and cost advantages are achieved.

[0065] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A camera supporting color temperature detection for detecting the color temperature of an external detection light source, comprising a lens (5), a base (6), an infrared filter (7), and a circuit board (8), wherein the lens (5) and the infrared filter (7) are mounted in the base (6), the circuit board (8) is located below the base (6), and the circuit board (8) is further provided with an image sensor, the image sensor comprising a first filter array (2), a photodiode array (3), and a sampling and processing circuit (4), characterized in that, The image sensor is also provided with multiple sets of second filter arrays (1). The first filter array (2) and the second filter array (1) are mounted side by side above the photodiode array (3). The second filter array (1) is located at the edge pixel of the first filter array (2). The photodiode array (3) is connected to and outputs signals to the sampling and processing circuit (4). A gap area is provided between each set of second filter arrays (1).

2. The camera supporting color temperature detection according to claim 1, characterized in that, The first filter array (2) is set as a Bayer filter array, and the second filter array (1) is set as a 380-730nm multi-row bandpass filter array. After the external detection light source enters the second filter array (1) and filters out other spectra, it enters the photodiode array (3) and is converted into an electrical signal. After being sampled and processed by the sampling and processing circuit (4), the irradiance of different spectra of the external detection light source is obtained, and the color temperature of the external detection light source is calculated.

3. The camera supporting color temperature detection according to claim 1, characterized in that, Each group of the second filter array (1) is set to the same fixed number of rows and columns, with at least 1 row and at least 1 column. Each group of the second filter array (1) is provided with the same fixed interval, which is at least 5 nanometers.

4. The camera supporting color temperature detection according to claim 1, characterized in that, A blank line is provided between the second filter array (1) and the first filter array (2), or no blank line is provided.

5. The camera supporting color temperature detection according to claim 1, characterized in that, The second filter array (1) has empty columns between each group, or no empty columns are set.

6. The camera supporting color temperature detection according to claim 1, characterized in that, The irradiance of the external detection light source for different spectra is set as B(λ, T), the color temperature expressed in absolute temperature is set as T, the Planck constant is set as h, the speed of light in vacuum is set as c, and the Boltzmann constant is set as k. The irradiance of the external detection light source for different spectra is then obtained as follows:

7. The camera supporting color temperature detection according to claim 1, characterized in that, It also includes sequentially performing analog processing, analog-to-digital conversion, and image processing color temperature estimation on the pixel array signal before outputting it to the MIPI interface or DVP interface.

8. The camera supporting color temperature detection according to claim 7, characterized in that, It also includes sequentially performing analog processing, analog-to-digital conversion, and image processing color temperature estimation on the signals output by the configuration register control timing control before outputting them to the MIPI interface or DVP interface, or directly performing image processing color temperature estimation before outputting them to the MIPI interface or DVP interface.

9. The camera supporting color temperature detection according to any one of claims 1 to 7, characterized in that, The irradiance of different spectra of the external detection light source is obtained by using the least squares method to minimize the sum of squared errors between the calculated irradiance and the actual measured value, and the color temperature of the external detection light source is obtained.

10. The camera supporting color temperature detection according to claim 8, characterized in that, Set the fitted color temperature to T. fit , wavelength λ i The obtained spectral irradiance is set to B. mea (λ i ), λ i For 36 wavelengths ranging from 380 to 730 nm, the least squares fitting formula is obtained as follows: min∑ i [B(λ i ,T fit )-B mea (l i )] 2 。

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