1. A lane recognition image processing apparatus installed on a vehicle for recognizing a lane based on a sensed image of at least one lane marking on the surface of a road, said apparatus comprising: an image sensing part for sensing a forward view of said vehicle; an image storage part for temporarily storing images obtained by said image sensing part; a window setting part for setting a search area for said at least one lane marking with respect to the images stored in said image storage part by means of a window; a candidate point extraction part for extracting candidate points for said at least one lane marking from said search area set by said window setting part; and a lane recognition part for deriving a lane marking mathematical model equation by approximating sets of candidate points extracted by said candidate point extraction part by a mathematical model equation. wherein said candidate point extraction part comprises: a kernel size setting part that sets a kernel size Δh in accordance with a forward distance from said vehicle; a one-dimensional image filtering part that outputs, as a filtering result, the smaller one of the values that are obtained by two equations {g(h)−g(h−Δh)} and {g(h)−g(h+Δh)} using the gray value g(h) of a pixel of interest and the gray values g(h−Δh), g(h+Δh) of pixels forwardly and rearwardly apart said kernel size Δh from said pixel of interest in a scanning direction, respectively; and a binarization part that binarizes said filtering result with a threshold.