Image sensing device and method of operating the same

Abstract

An image sensing device and an operation method thereof are disclosed, and the image sensing device may include: an image sensor including a plurality of pixels and adapted to generate an image based on incident light; and an image processor adapted to generate a high dynamic range (HDR) image based on the image and two or more tone mapping information divided according to brightness.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority to Korean Patent Application No. 10-2020-0040958, filed on Apr. 3, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] Various embodiments of the present disclosure relate to semiconductor design technologies, and more particularly, to an image sensing device and an operating method thereof. Background Art

[0004] An image sensing device captures an image by using the property of a semiconductor to react to light. Generally, there are two types of image sensing devices: a charge-coupled device (CCD) image sensing device and a complementary metal-oxide semiconductor (CMOS) image sensing device. Recently, since a CMOS image sensing device allows analog and digital control circuits to be directly implemented on a single integrated circuit (IC), the CMOS image sensing device has been widely used. Summary of the Invention

[0005] Various embodiments of the present disclosure are directed to an image sensing device and an operating method of the image sensing device, the image sensing device using a semi-global tone mapping method in which a global tone mapping method and a local tone mapping method are combined.

[0006] According to one embodiment, an image sensing device may include: a tone mapping module configured to generate two or more tone mapping information divided according to luminance based on a previously stored histogram; and a high dynamic range (HDR) image generation module configured to generate an HDR image based on the tone mapping information and an image.

[0007] The tone mapping module may include: a clustering block configured to generate two or more clustering histograms based on the histogram according to at least one threshold luminance value; and a tone mapping information generation block configured to generate the tone mapping information based on the clustering histograms.

[0008] According to one embodiment, an image sensing device may include: an image sensor including a plurality of pixels and configured to generate an image based on incident light; and an image processor configured to generate a high dynamic range (HDR) image based on the image and two or more tone mapping information divided according to luminance.

[0009] The image processor may include: a tone mapping module configured to generate the tone mapping information based on a previously stored histogram; and an HDR image generation module configured to generate an HDR image based on the tone mapping information and the image.

[0010] The tone mapping module may include: a clustering block, adapted to generate two or more clustering histograms based on a histogram according to at least one threshold luminance value; and a tone mapping information generation block, adapted to generate tone mapping information based on the clustering histograms.

[0011] According to one embodiment, an operation method of an image sensing device may include: generating a histogram based on a first image according to a global tone mapping scheme; generating two or more pieces of tone mapping information divided according to luminance based on the histogram according to a local tone mapping scheme; and generating a high dynamic range (HDR) image based on the tone mapping information and a second image.

[0012] The first image may correspond to a previous frame, and the second image may correspond to a current frame.

[0013] Each of the first image and the second image may correspond to a current frame.

[0014] Generating the tone mapping information may include: generating two or more clustering histograms based on the histogram according to at least one threshold luminance value; generating a modified histogram corresponding to the clustering histograms according to a stretching scheme; generating a smoothed histogram corresponding to the modified histogram according to a smoothing scheme; and generating tone mapping information including two or more tone mapping curves based on the smoothed histogram.

[0015] Generating the tone mapping information may include: generating two or more clustering histograms based on the histogram according to at least one threshold luminance value; and generating tone mapping information including two or more tone mapping curves based on the clustering histograms.

[0016] According to one embodiment, an operation method of an image sensing device may include: generating tone mapping information according to the luminance of pixels based on a histogram representing the frequency of pixels within an image, the tone mapping information being segmented into two or more groups with reference to one or more threshold luminance values; and generating a high dynamic range (HDR) image based on the groups and any one of the image and a subsequent image. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a block diagram illustrating an image sensing device according to an embodiment.

[0018] Figure 2 is a block diagram illustrating an image processor such as Figure 1 as shown.

[0019] Figure 3 is a block diagram illustrating a histogram generation module such as Figure 2 as shown.

[0020] Figure 4 is a block diagram illustrating such asFigure 2 Block diagram of the tone mapping module shown

[0021] Figure 5 is a diagram such as Figure 2 Block diagram of the HDR image generation module shown

[0022] Figure 6 is a diagram such as Figure 2 Diagram showing the operation of the histogram generation module shown

[0023] Figure 7 is a diagram such as Figure 3 Diagram showing the operation of the clustering block shown

[0024] Figure 8 is a diagram such as Figure 3 Diagram showing the operation of the histogram generation block shown

[0025] Figure 9 is a diagram such as Figure 3 Diagram showing the operation of the tone mapping curve generation block shown

[0026] Figure 10 is a diagram such as Figure 2 Diagram showing the operation of the HDR image generation module shown Detailed implementation mode

[0027] Various embodiments will be described below with reference to the accompanying drawings so that those skilled in the art can practice and easily implement the present invention

[0028] It will be understood that when an element is referred to as being "connected to" or "coupled to" another element, the element can be directly connected or coupled to the other element, or electrically connected or coupled to the other element with one or more elements inserted therebetween. Additionally, it will also be understood that when used in this specification, the terms "comprising", "comprising... of", "including", "including... of" specify the presence of the stated element and do not exclude the presence or addition of one or more other elements. Throughout the specification, a component identified in the singular does not necessarily mean that only one such component exists; there can be more than one such component unless otherwise stated or the context otherwise requires. Furthermore, throughout the specification, references to "one embodiment" etc. are not necessarily only one embodiment, and different references to any such phrase are not necessarily the same (multiple) embodiments

[0029] Figure 1 Block diagram of the image sensing device according to an embodiment shown

[0030] Refer to Figure 1 , the image sensing device may include an image sensor 100, a memory 200, and an image processor 300

[0031] The image sensor 100 may generate an image for each frame based on incident light. Although not illustrated, the image sensor 100 may include a pixel array and a signal converter. The pixel array may include a plurality of pixels that generate image values based on incident light. For example, the plurality of pixels may be arranged in a Bayer pattern. The signal converter may include a plurality of analog-to-digital (A / D) converters for converting the image values into digital values. The image may be represented by the digital values. Hereinafter, the image generated in the previous frame is referred to as the first image IMG1, and the image generated in the current frame is referred to as the second image IMG2.

[0032] The memory 200 may store a histogram HIST, first tone mapping information TM1, and second tone mapping information TM2 generated by the image processor 300. The histogram HIST, first tone mapping information TM1, and second tone mapping information TM2 will be described in detail below.

[0033] The image processor 300 may generate a high dynamic range (HDR) image HDR_IMG based on the first tone mapping information TM1 and the second tone mapping TM2, and the first image IMG1 and the second image IMG2. For example, the image processor 300 may generate the HDR image HDR_IMG through a semi-global tone mapping scheme in which a global tone mapping scheme and a local tone mapping scheme are combined.

[0034] Since the image sensor 100 and the memory 200 may be configured according to well-known techniques, only the image processor 300 will be described in detail below.

[0035] Figure 2 is illustrated Figure 1 is a block diagram of the illustrated image processor 300.

[0036] Refer to Figure 2 , the image processor 300 may include a histogram generation module 310, a tone mapping module 320, and an HDR image generation module 330. The histogram generation module 310 may generate a histogram HIST based on the first image IMG1. The histogram HIST may represent the frequency of pixels according to the luminance values. The frequency of pixels refers to the number of pixels having the corresponding luminance value. The histogram HIST may be stored in the memory 200.

[0037] The tone mapping module 320 can generate first tone mapping information TM1 and second tone mapping information TM2 divided according to brightness based on the histogram HIST. For example, the first tone mapping information TM1 can include a first tone mapping curve for improving the contrast of relatively dark regions of the first image IMG1, and the second tone mapping information TM2 can include a second tone mapping curve for improving the contrast of relatively bright regions of the first image IMG1. The first tone mapping information TM1 and the second tone mapping information TM2 can be stored in the memory 200.

[0038] The HDR image generation module 330 can generate an HDR image HDR_IMG based on the first tone mapping information TM1, the second tone mapping information TM2, and the second image IMG2.

[0039] Figure 3 is a diagram Figure 2 of the block diagram of the histogram generation module 310 shown.

[0040] Reference Figure 3 , the histogram generation module 310 can include a brightness value calculation block 311 and a histogram generation block 313.

[0041] The brightness value calculation block 311 can calculate the brightness value for each pixel of the first image IMG1. For example, the brightness value calculation block 311 can calculate the brightness value for each pixel among a plurality of pixels based on the digital value representing the first image IMG1 (refer to Figure 6 (A) and (B)).

[0042] The histogram generation block 313 can generate a histogram HIST based on the brightness value YV1 calculated by the brightness value calculation block 311 (refer to Figure 6 (C)).

[0043] Figure 4 is a diagram Figure 2 of the block diagram of the tone mapping module 320 shown.

[0044] Reference Figure 4 , the tone mapping module 320 can include a clustering block 321 and a tone mapping information generation block 323.

[0045] The clustering block 321 can generate a first clustering histogram HC1 and a second clustering histogram HC2 based on the histogram HIST according to a threshold brightness value T. For example, the clustering block 321 can count the frequency of pixels for each of a plurality of brightness values based on the histogram HIST, and generate the first clustering histogram HC1 and the second clustering histogram HC2 according to the counting result, such that the number of pixels in each of the first clustering histogram HC1 and the second clustering histogram HC2 is the same (refer toFigure 7 )。

[0046] The tone mapping information generation block 323 can generate first tone mapping information TM1 and second tone mapping information TM2 based on the first clustering histogram HC1 and the second clustering histogram HC2 (refer to Figure 8 ). The first tone mapping information TM1 can include a first tone mapping curve corresponding to the first clustering histogram HC1. The second tone mapping information TM2 can include a second tone mapping curve corresponding to the second clustering histogram HC2. Each of the first tone mapping curve and the second tone mapping curve can correspond to the cumulative number of pixels of a corresponding luminance value.

[0047] Figure 5 is an illustration Figure 2 of the block diagram of the HDR image generation module 330 shown.

[0048] Refer to Figure 5 , the HDR image generation module 330 can include a luminance value calculation block 331, a blur block 333, and an image processing block 335.

[0049] The luminance value calculation block 331 can calculate the luminance value for each pixel of the second image IMG2 (refer to Figure 10 (A) and (B) of Figure 3 ). The luminance value calculation block 331 can operate in the same manner as the luminance value calculation block 311 described above with reference to

[0050] The blur block 333 can generate a blur code value YB for each pixel based on the luminance value YV2 calculated by the luminance value calculation block 331 (refer to Figure 10 (C) of

[0051] The image processing block 335 can generate the HDR image HDR_IMG based on the blur code value YB generated by the blur block 333, and the first tone mapping information TM1 and the second tone mapping information TM2.

[0052] Hereinafter, refer to Figures 6 to 10 to describe the operation of the image sensing device having the above configuration according to an embodiment.

[0053] Figure 6 is a diagram illustrating the operation of the histogram generation module 310 included in the image sensing device.

[0054] Refer to Figure 6 , the first image IMG1 can be represented by a digital value generated according to the arrangement of a plurality of pixels (i.e., the Bayer pattern as shown in (A)).

[0055] The histogram generation module 310 can generate luminance values corresponding to a plurality of pixels based on digital values, as shown in Figure 6 (B) of

[0056] [Equation 1]

[0057] P22 = (P11 + P13 + 4 * P22 + P31 + P33) + 2 * (P12 + P32) + 2 * (P21 + P23) / 16

[0058] The histogram generation module 310 can generate a histogram HIST based on the calculated luminance values, as shown in Figure 6 (C) of

[0059] Figures 7 to 9 FIG. is a diagram illustrating the operation of the tone mapping module 320 included in the image sensing device.

[0060] Figure 7 FIG. is a diagram illustrating the operation of the clustering block 321 included in the tone mapping module 320.

[0061] Reference Figure 7 , the clustering block 321 can generate a first clustering histogram HC1 and a second clustering histogram HC2 based on the histogram HIST according to a threshold luminance value T. For example, the clustering block 321 can count the frequency of pixels with respect to the luminance value based on the histogram HIST, and extract the threshold luminance value T when the counting result indicates that the frequency of the pixels corresponds to half of the total number of pixels, as shown in Figure 6 (A) of Figure 6 . In addition, the clustering block 321 can generate a first clustering histogram HC1 indicating the frequency of pixels with relatively low luminance values based on the threshold luminance value T, as shown in (B) of

[0062] Figure 8 Figure 9 FIG. is a diagram illustrating the operation of the tone mapping information generation block 323 included in the tone mapping module 320, and Figure 8 FIG. is an additional diagram illustrating the operation of the tone mapping information generation block 323 shown in

[0063] The tone mapping information generation block 323 can generate first tone mapping information TM1 based on the first clustered histogram HC1. The tone mapping information generation block 323 can receive the first clustered histogram HC1, as shown in (A) of Figure 8 and generate a first smoothed histogram based on the first clustered histogram HC1, as shown in (B) of Figure 8 . The process of generating the first smoothed histogram will be described in detail below.

[0064] The tone mapping information generation block 323 can generate a first modified histogram corresponding to the first clustered histogram HC1 according to a stretching scheme. For example, the tone mapping information generation block 323 can generate the first modified histogram by adaptively adjusting the stretching degree of the first clustered histogram HC1 based on the peak of the frequency of the pixels included in the first clustered histogram HC1. The following equation 2 can be used to generate the first modified histogram.

[0065] [Equation 2]

[0066] HIST1_modification(code) = λ * HC1(code) + (1 - λ) * HIST_uniform(code)

[0067] In this article, "HIST1_modification(code)" can refer to the frequency corresponding to each luminance value in the first modified histogram. "λ" can refer to the stretching degree. As shown in Figure 9 , as the peak increases, "λ" increases. "HC1(code)" can refer to the frequency corresponding to each luminance value in the first clustered histogram HC1. "HIST_uniform(code)" can refer to a histogram with a uniform frequency. The following equation 3 can be used to generate "HIST_uniform(code)".

[0068] [Equation 3]

[0069] HIST_uniform(code) = m * n / max_code

[0070] In this article, "m * n" can refer to the total number of pixels. "max_code" can refer to the maximum luminance value within the range of the luminance values in the histogram HIST.

[0071] The tone mapping information generation block 323 can generate a first smoothed histogram corresponding to the first modified histogram according to a smoothing scheme. The following equation 4 can be used to generate the first smoothed histogram.

[0072] [Equation 4]

[0073] HIST1_smoothing(code) = convolution(HIST1_modification(code), line_filter(tap))

[0074] In this text, "HIST1_smoothing(code)" may refer to the frequency corresponding to each luminance value in the first smoothed histogram. "HIST1_modification(code)" may refer to the frequency corresponding to each luminance value in the first modified histogram. "line_filter(tap)" may determine the range of luminance values included in the first modified histogram according to the value set in "tap". "convolution(HIST1_modification(code), line_filter(tap))" may refer to the average value of the frequencies within the range of luminance values in the first modified histogram determined according to the value set in "tap".

[0075] The tone mapping information generation block 323 may generate first tone mapping information TM1 including a first tone mapping curve based on the first modified histogram and the first smoothed histogram, as Figure 8 shown in (C) of. The first tone mapping curve may correspond to the cumulative number of pixels according to the luminance value. The first tone mapping curve may be generated using the following Equation 5.

[0076] [Equation 5]

[0077]

[0078] In this text, "TM1_curve(code)" may refer to the frequency corresponding to each luminance value included in the first tone mapping curve. may refer to the cumulative number obtained by adding the frequencies corresponding to the luminance values in the first smoothed histogram.

[0079] As another example, the tone mapping information generation block 323 may omit the process of generating the first smoothed histogram. That is, the tone mapping information generation block 323 may use the following Equation 6 to generate first tone mapping information TM1 including a first tone mapping curve.

[0080] [Equation 6]

[0081]

[0082] In this text, may refer to the cumulative number obtained by adding the frequencies corresponding to the luminance values included in the first clustering histogram HC1.

[0083] The tone mapping information generation block 323 may generate second tone mapping information TM2 including a second tone mapping curve based on the second clustering histogram HC2 in the same manner as described above.

[0084] Figure 10 FIG. is a diagram illustrating operations of the HDR image generation module 330 included in the image sensing device.

[0085] Reference Figure 10 , the HDR image generation module 330 may generate luminance values YV2 corresponding to a plurality of pixels based on digital values representing the second image IMG2 (as shown in (A) of Figure 10 ), as shown in (B) of Figure 10 . Since the process of generating the luminance values YV2 is the same as the operation of the histogram generation module 310 described above, a detailed description thereof is omitted herein.

[0086] The HDR image generation module 330 may generate a blur code value for each pixel based on the luminance values YV2, as shown in (C) of Figure 10 . For example, the HDR image generation module 330 may calculate an average value of luminance values of 5×5 pixels based on a target pixel and generate the average value as the blur code value.

[0087] The HDR image generation module 330 may generate an HDR image HDR_IMG based on the blur code value YB and the first tone mapping information TM1 and the second tone mapping information TM2, as shown in (D) of Figure 10 . For example, the HDR image generation module 330 may generate the HDR image HDR_IMG by calculating a gain for each pixel and reflecting each gain in each luminance value YV2 included in the second image IMG2. The gain may be calculated using the following Equation 7.

[0088] [Equation 7]

[0089] g(i, j) = (1 - w(i, j)) * TM1(Y_blur(i, j)) + w(i, j) * TM2(Y_blur(i, j)

[0090] In this text, "g(i,j)" may refer to the gain of a pixel arranged at the intersection of the i-th row and the j-th column. "w(i,j)" may refer to the weight of a pixel arranged at the intersection of the i-th row and the j-th column. "TM1(Y_blur(i,j))" may refer to the frequency of the first tone mapping curve corresponding to the blur code value of a pixel arranged at the intersection of the i-th row and the j-th column. "TM2(Y_blur(i,j))" may refer to the frequency of the second tone mapping curve corresponding to the blur code value of a pixel arranged at the intersection of the i-th row and the j-th column.

[0091] The weight can be calculated using the following Equation 8.

[0092] [Equation 8]

[0093] w(i, j) = (Y_blur(i, j) - min(Y_pre_frame)) / (max(Y_pre_frame) - min(Y_pre_frame))

[0094] "w(i, j)" may refer to the weight of the pixel arranged at the intersection of the i-th row and the j-th column. "Y_blur(i, j)" may refer to the blurred code value of the pixel arranged at the intersection of the i-th row and the j-th column. "min(Y_pre_frame)" may refer to the minimum value of the luminance value YV1 in the first image IMG1. "max(Y_pre_frame)" may refer to the maximum value of the luminance value YV1 in the first image IMG1.

[0095] In summary, the operation method of the image sensing device is as follows. The operation method of the image sensing device may include: generating a histogram HIST based on the first image IMG1 through a global tone mapping scheme (refer to Figure 6 ); generating first tone mapping information TM1 and second tone mapping information TM2 divided according to luminance based on the histogram HIST through a local tone mapping scheme (refer to Figures 7 to 9 ); and generating an HDR image HDR_IMG based on the first tone mapping information TM1, the second tone mapping information TM2, and the second image IMG2 (refer to Figure 10 ).

[0096] Generating the first tone mapping information TM1 and the second tone mapping information TM2 may include: generating a first cluster histogram HC1 and a second cluster histogram HC2 based on the histogram HIST according to a threshold luminance value T; generating a first modified histogram and a second modified histogram corresponding to the first cluster histogram HC1 and the second cluster histogram HC2 respectively according to a stretching scheme; generating a first smoothed histogram and a second smoothed histogram corresponding to the first modified histogram and the second modified histogram respectively according to a smoothing scheme; and generating the first tone mapping information TM1 and the second tone mapping information TM2 including a first tone mapping curve and a second tone mapping curve based on the first smoothed histogram and the second smoothed histogram.

[0097] As another example, generating the first tone mapping information TM1 and the second tone mapping information TM2 may include: generating a first cluster histogram HC1 and a second cluster histogram HC2 based on the histogram HIST according to a threshold brightness value T; and generating the first tone mapping information TM1 including a first tone mapping curve and the second tone mapping information TM2 including a second tone mapping curve respectively based on the first cluster histogram HC1 and the second cluster histogram HC2.

[0098] In the present embodiment, an example is described in which the histogram HIST and the first tone mapping information TM1 and the second tone mapping information TM2 are generated using a first image IMG1 corresponding to a previous frame. This example may be applicable to video shooting. In contrast, in the case of taking a still photo, the histogram HIST and the first tone mapping information TM1 and the second tone mapping information TM2 may be generated using a second image IMG2 corresponding to the current frame.

[0099] According to an embodiment of the present disclosure, since a histogram corresponding to the entire image is generated according to a global tone mapping scheme, and a first tone mapping curve for improving a relatively dark region and a second tone mapping curve for improving a relatively bright region are generated according to a local tone mapping scheme, the disadvantages of the global tone mapping scheme and the local tone mapping scheme can be separately compensated by using the two schemes. Additionally, according to an embodiment of the present disclosure, since the first tone mapping curve and the second tone mapping curve are generated according to brightness, compared with a local tone mapping scheme in the prior art that only generates a tone mapping curve for each region, the local contrast can be further improved.

[0100] According to an embodiment of the present disclosure, a semi-global tone mapping scheme that uses a global tone mapping scheme and a local tone mapping scheme overcomes the limitations of contrast improvement (disadvantages of the global tone mapping scheme) and the limitations of hardware resource improvement (disadvantages of the local tone mapping scheme).

[0101] Although the present disclosure has been illustrated and described with respect to specific embodiments, the disclosed embodiments and any specific description are not intended to be limiting. Additionally, it should be noted that, as will be recognized by those skilled in the art according to the present disclosure, the present invention can be implemented in various ways by substitution, change, and modification. The present invention encompasses all such variations that fall within the scope of the claims.

Claims

1. An image sensing device, comprising: a tone mapping module adapted to generate two or more tone mapping information divided according to brightness by a local tone mapping scheme based on a histogram generated by a global tone mapping scheme for a first image stored previously; and a high dynamic range (HDR) image generation module adapted to generate an HDR image based on the tone mapping information and a second image, wherein the first image corresponds to a previous frame, the second image corresponds to a current frame adjacent to the previous frame, and wherein the two or more tone mapping information includes tone mapping curves for improving the contrast of relatively dark areas or relatively bright areas of the first image.

2. The image sensing device according to claim 1, wherein the tone mapping module comprises: a clustering block adapted to generate two or more clustering histograms according to at least one threshold brightness value based on the histogram; and a tone mapping information generation block adapted to generate the tone mapping information based on the clustering histograms.

3. The image sensing device according to claim 2, wherein the clustering block counts the frequency of pixels with respect to brightness values within the histogram, and wherein the clustering block generates the clustering histograms such that the number of pixels within each of the clustering histograms is the same.

4. The image sensing device according to claim 2, wherein the tone mapping information generation block generates the tone mapping information based on the clustering histograms, and wherein each of the tone mapping curves corresponds to the cumulative number of pixels with respect to brightness values.

5. The image sensing device according to claim 1, wherein the HDR image generation module comprises: a brightness value calculation block adapted to calculate a brightness value for each pixel of the second image; a blurring block adapted to generate a blurring code value for each pixel based on the brightness value calculated by the brightness value calculation block; and an image processing block adapted to generate the HDR image based on the blurring code value generated by the blurring block and the tone mapping information.

6. The image sensing device according to claim 1, further comprising a histogram generation module adapted to generate the histogram indicating the frequency of pixels according to brightness values based on the first image corresponding to the previous frame.

7. The image sensing device according to claim 6, wherein the histogram generation module comprises: a brightness value calculation block adapted to calculate the brightness value for each pixel of the first image; and a histogram generation block adapted to generate the histogram based on the brightness value calculated by the brightness value calculation block.

8. An image sensing device, comprising: an image sensor including a plurality of pixels and adapted to sequentially generate a first image and a second image based on incident light; and an image processor including: a tone mapping module adapted to generate two or more tone mapping information divided according to brightness by a local tone mapping scheme based on a histogram generated by a global tone mapping scheme for the first image; and A high dynamic range (HDR) image generation module, adapted to generate an HDR image based on the tone mapping information and the second image, wherein the first image corresponds to a previous frame, the second image corresponds to a current frame adjacent to the previous frame, and wherein the two or more tone mapping information includes tone mapping curves for improving the contrast of relatively dark or relatively bright regions of the first image.

9. The image sensing device according to claim 8, wherein the tone mapping module comprises: a clustering block, adapted to generate two or more clustered histograms based on the histogram according to at least one threshold luminance value; and a tone mapping information generation block, adapted to generate the tone mapping information based on the clustered histograms.

10. The image sensing device according to claim 9, wherein the clustering block counts the frequency of pixels according to luminance values within the histogram based on the histogram, and wherein the clustering block generates the clustered histograms such that the number of pixels within each of the clustered histograms is the same.

11. The image sensing device according to claim 9, wherein the tone mapping information generation block generates the tone mapping information based on the clustered histograms, and wherein each of the tone mapping curves corresponds to the cumulative number of pixels with respect to luminance values.

12. The image sensing device according to claim 8, wherein the HDR image generation module comprises: a luminance value calculation block, adapted to calculate a luminance value for each pixel of the second image; a blurring block, adapted to generate a blurring code value for each pixel based on the luminance value calculated by the luminance value calculation block; and an image processing block, adapted to generate the HDR image based on the blurring code value generated by the blurring block and the tone mapping information.

13. The image sensing device according to claim 8, further comprising a histogram generation module, the histogram generation module being adapted to generate the histogram indicating the frequency of pixels according to luminance values based on the first image corresponding to the previous frame.

14. The image sensing device according to claim 13, wherein the histogram generation module comprises: a luminance value calculation block, adapted to calculate the luminance value for each pixel of the first image; and a histogram generation block, adapted to generate the histogram based on the luminance value calculated by the luminance value calculation block.

15. An operating method of an image sensing device, comprising: generating a histogram based on a first image according to a global tone mapping scheme; generating two or more tone mapping information divided according to luminance based on the histogram according to a local tone mapping scheme; and generating a high dynamic range (HDR) image based on the tone mapping information and a second image, wherein the first image corresponds to a previous frame, the second image corresponds to a current frame adjacent to the previous frame, and wherein the two or more tone mapping information includes tone mapping curves for improving the contrast of relatively dark or relatively bright regions of the first image.

16. The operation method according to claim 15, wherein generating the tone mapping information comprises: generating two or more clustered histograms based on the histogram and according to at least one threshold luminance value; generating a modified histogram corresponding to the clustered histogram according to a stretching scheme; generating a smoothed histogram corresponding to the modified histogram according to a smoothing scheme; and generating the tone mapping information based on the smoothed histogram.

17. The operation method according to claim 15, wherein generating the tone mapping information comprises: generating two or more clustered histograms based on the histogram and according to at least one threshold luminance value; and generating the tone mapping information including two or more tone mapping curves based on the clustered histogram.

Images