Image sensor including image signal processor and operating method of the image sensor
An image sensor including an image signal processor and an operating method of the image sensor are provided. An image sensor may include a pixel array configured to convert a received optical signal into electrical signals, a readout circuit configured to analog-digital convert the electrical signals to generate image data, and an image signal processor configured to perform one-dimensional filtering in each of a first direction and a second direction on the image data to remove noise of the image data, the second direction being different than the first direction.
1. An image sensor comprising:
a pixel array configured to convert a received optical signal into electrical signals;
a readout circuit configured to analog-digital convert the electrical signals to generate image data; and
an image signal processor configured to perform one-dimensional filtering in each of a first direction and a second direction on the image data to remove noise of the image data, the second direction being different than the first direction;
wherein the image signal processor is configured to
perform the one-dimensional filtering by applying a one-dimensional Gaussian filter to a plurality of pixels which have a same color and are arranged in the first direction or the second direction, wherein the image signal processor is configured to store a plurality of weights corresponding to each of a plurality of gains and adjust strength of the one-dimensional Gaussian filter by multiplying reference coefficients of the one-dimensional Gaussian filter by a weight corresponding to a set gain among the plurality of weights, a value of a first coefficient applied to a filtering target pixel among a plurality of coefficients included in the one-dimensional Gaussian filter being reduced as strength of the one-dimensional Gaussian filter increases;
calculate a converted pixel value of the filtering target pixel based on a number of bits representing the first coefficient; and
sense a peripheral illumination of the image sensor, wherein, as peripheral illumination decreases, a value of the gain increases, and strength of the one-dimensional Gaussian filter increases.
2. The image sensor of claim 1 , wherein the image signal processor is configured to perform the one-dimensional filtering by pixel group units including M 2 number of pixels arranged in an M×M matrix (where M is an even number of two or more) and to perform the one-dimensional filtering on each of the M 2 pixels on the basis of M 2 number of one-dimensional Gaussian filters respectively corresponding to the M 2 pixels.
3. The image sensor of claim 1 , wherein the plurality of coefficients have a Gaussian distribution, and a value of a first coefficient applied to the filtering target pixel among the plurality of coefficients is largest.
4. The image sensor of claim 1 , wherein the image signal processor comprises:
a bad pixel correction logic configured to correct a pixel value of a bad pixel included in the image data; and
a noise reduction logic configured to perform the one-dimensional filtering in the first direction and the second direction on the image data based on a plurality of one-dimensional filters to remove noise of the image data.
5. The image sensor of claim 4 , wherein the noise reduction logic comprises:
a first filtering module configured to perform one-dimensional filtering in the first direction on the image data on the basis of a first filter; and
a second filtering module configured to perform one-dimensional filtering in the second direction on image data on which the one-dimensional filtering in the first direction has been performed, on the basis of a second filter, and
the first direction is one of a horizontal direction and a vertical direction of the image data, and the second direction is the other of the horizontal direction and the vertical direction of the image data.
6. The image sensor of claim 4 , wherein the noise reduction logic is configured to receive directionality information, representing whether a pixel from the bad pixel correction logic corresponds to an edge region, and to determine whether to skip an operation of performing one-dimensional filtering in the first direction or one-dimensional filtering in the second direction on the pixel on the basis of the directionality information.
7. The image sensor of claim 4 , wherein the image signal processor further comprises a remosaic logic configured to convert a pattern of the image data into a Bayer pattern.
8. An image sensor comprising:
a pixel array configured to convert a received optical signal into electrical signals;
a readout circuit configured to analog-digital convert the electrical signals to generate image data; and
a noise reduction logic configured to
continuously perform one-dimensional filtering in a plurality of directions on the image data based on a one-dimensional Gaussian filter set, wherein the noise reduction logic is configured to perform the one-dimensional filtering on the image data by pixel group units including M 2 number of pixels arranged in an M×M matrix (where M is an even number of two or more) on a basis of M 2 number of one-dimensional Gaussian filters included in the one-dimensional Gaussian filter set, wherein the noise reduction logic is configured to store a plurality of weights corresponding to each of a plurality of gains and calculate coefficient values of a plurality of coefficients, respectively included in the M 2 one-dimensional Gaussian filters, by multiplying reference coefficient values by a weight based on a gain,
calculate a converted pixel value of a target pixel based on a number of bits representing the plurality of coefficients, and
sense a peripheral illumination of the image sensor, wherein, as peripheral illumination decreases, a value of the gain increases, and strength of the one-dimensional Gaussian filters increases.
9. The image sensor of claim 8 , wherein the noise reduction logic is configured to perform one-dimensional filtering in a first direction on the image and to perform one-dimensional filtering in a second direction, the first direction is one of a horizontal and a vertical direction of the image data, and the second direction is the other of the horizontal direction and the vertical direction of the image data.
10. The image sensor of claim 8 , wherein the noise reduction logic further comprises
a bad pixel correction logic configured to perform bad pixel correction on the image data.
11. An operating method of an image sensor including a signal processing processor, the operating method comprising:
generating image data on the basis of an optical signal received by a pixel array;
performing, by the signal processing processor, one-dimensional filtering in a first direction on the image data on the basis of a first Gaussian filter; and
performing, by the signal processing processor, one-dimensional filtering in a second direction on the image data on the basis of a second Gaussian filter, the second direction being different than the first direction;
setting, by the signal processing processor, a plurality of coefficients included in each of the first Gaussian filter and the second Gaussian filter by multiplying a plurality of coefficients by a weight corresponding to a set gain among a plurality of weights, wherein the plurality of weights are preset to correspond to a plurality of gains;
calculating a converted pixel value of a target pixel based on a number of bits representing the plurality of coefficients; and
sensing a peripheral illumination of the image sensor, wherein, as peripheral illumination decreases, a value of the gain increases, and strength of the first Gaussian filter and the second Gaussian filter increases.
12. The operating method of claim 11 , further comprising performing, by the signal processing processor, bad pixel correction on the image data.
13. The operating method of claim 12 , further comprising determining, by the signal processing processor, whether to skip one-dimensional filtering in the first direction and/or one-dimensional filtering in the second direction on the basis of directionality information about a pixel which is generated in the performing of the bad pixel correction.
14. The operating method of claim 11 , further comprising, before the one-dimensional filtering in the first direction is performed, performing remosaic processing for converting the image data into image data having a Bayer pattern.