A disparity computation system comprising: an acquisition unit (100, 711) configured to obtain a stereo image comprising a reference image and a comparison image from a stereo camera unit, and distance data (Z 1) indicating distance to an object in real space that lies at a position of a reference-pixel area (p) in the reference image from another distance sensor; a calculation unit configured to calculate: a first cost, indicating a degree of dissimilarity between the reference-pixel area (p) and a plurality of pixel areas in the comparison image, based on a difference between a pixel value of the reference pixel area (p) and pixel values of the plurality of pixel areas; a second cost (C 1), indicating a degree of dissimilarity between the reference-pixel area (p) and a pixel area at the position derived from the obtained distance data (Z 1) in the comparison image, based on a difference between the pixel value of the reference pixel area (p) and a pixel value of the pixel area that is at the position derived from the distance data (Z 1); and a weighted cost (Ĉ), wherein the calculation unit calculates the weighted cost (Ĉ) by combining the first cost and the second cost (C 1), said combining being based on weighted adding up of costs, said weighted adding up prioritizing the first cost when calculating the weighted cost (Ĉ) for the other pixel areas in the comparison image and prioritizing the second cost when calculating the weighted cost (Ĉ) for the pixel area that is at the position derived from the distance data (Z 1); and a computation unit configured to compute a disparity using the weighted cost (Ĉ) in a cost based matching of the pixel areas in the reference image and the comparison image, wherein the calculation unit calculates the weighted cost (Ĉ) for possible disparity shifts d for the stereo image and for the possible disparity shift d 1 derived from the other distance sensor, such as to make more significant the difference in cost between pixel areas where d = d 1 and other pixel areas for which d≠d 1. an acquisition unit (100, 711) configured to obtain a stereo image comprising a reference image and a comparison image from a stereo camera unit, and distance data (Z 1) indicating distance to an object in real space that lies at a position of a reference-pixel area (p) in the reference image from another distance sensor; a calculation unit configured to calculate: a first cost, indicating a degree of dissimilarity between the reference-pixel area (p) and a plurality of pixel areas in the comparison image, based on a difference between a pixel value of the reference pixel area (p) and pixel values of the plurality of pixel areas; a second cost (C 1), indicating a degree of dissimilarity between the reference-pixel area (p) and a pixel area at the position derived from the obtained distance data (Z 1) in the comparison image, based on a difference between the pixel value of the reference pixel area (p) and a pixel value of the pixel area that is at the position derived from the distance data (Z 1); and a weighted cost (Ĉ), a first cost, indicating a degree of dissimilarity between the reference-pixel area (p) and a plurality of pixel areas in the comparison image, based on a difference between a pixel value of the reference pixel area (p) and pixel values of the plurality of pixel areas; a second cost (C 1), indicating a degree of dissimilarity between the reference-pixel area (p) and a pixel area at the position derived from the obtained distance data (Z 1) in the comparison image, based on a difference between the pixel value of the reference pixel area (p) and a pixel value of the pixel area that is at the position derived from the distance data (Z 1); and a weighted cost (Ĉ), wherein the calculation unit calculates the weighted cost (Ĉ) by combining the first cost and the second cost (C 1), said combining being based on weighted adding up of costs, said weighted adding up prioritizing the first cost when calculating the weighted cost (Ĉ) for the other pixel areas in the comparison image and prioritizing the second cost when calculating the weighted cost (Ĉ) for the pixel area that is at the position derived from the distance data (Z 1); and a computation unit configured to compute a disparity using the weighted cost (Ĉ) in a cost based matching of the pixel areas in the reference image and the comparison image, wherein the calculation unit calculates the weighted cost (Ĉ) for possible disparity shifts d for the stereo image and for the possible disparity shift d 1 derived from the other distance sensor, such as to make more significant the difference in cost between pixel areas where d = d 1 and other pixel areas for which d≠d 1.