Exposure controller for on-vehicle camera

Abstract

An exposure controller for an on-vehicle camera mounted on a vehicle is capable of performing exposure control such that a predetermined subject such as a lane marker can be imaged with a constant contrast regardless of variation of peripheral brightness and directions of the variation. An exposure controller images information imaged by an imaging part based on a second exposure property having linearity, the second exposure property being obtained by converting a first exposure property having non-linearity, calculates a target density value with which pixels in a window set in the image are to be imaged based on brightness values corresponding to density values of the pixels in the window, sets a third exposure property for obtaining the calculated target density value, and performs imaging with the set third exposure property.

Description

technical field [0001] The present invention relates to an exposure control device for an on-vehicle camera that controls the exposure of the camera so that the on-vehicle camera mounted on the vehicle can capture a subject with a constant contrast regardless of changes in surrounding brightness. Background technique [0002] In recent years, a lane departure warning system has been proposed in which a camera is installed on a vehicle, and white or yellow lines (hereinafter referred to as lane markings) drawn on the edge of a driving lane are captured by the installed camera through image processing. Lane markings are detected in the image, and based on the position of such lane markings and the behavior of the vehicle, it is possible to judge the possibility of departing from the lane and issue an alarm. [0003] In the case of a system using such image processing, it is desired to be able to stably detect lane markings regardless of surrounding brightness. [0004] Theref...

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Problems solved by technology

[0007] However, in the case of the exposure control method described in Patent Document 1, since the non-linearity of the exposure characteristics of the imaging element used in the imaging unit is not considered, the contrast between the road surface area and the lane markings in the exposure-controlled image is is not constant

[0008] Here, when detecting lane markings from images subjected to exposure control, it is necessary to set an appropriate threshold for recognizing the road surface and lane markings for each captured image. However, when the contrast is not constant as described above, In order to properly recognize road surfaces and lane markings, the threshold must be changed for each image, and this process of setting the threshold becomes complicated, and there is a problem that calculation time increases

[0009] Furthermore, in the case of the exposure control method described in Patent Document 1, the exposure control method when the surrounding suddenly becomes bright is described, but there is no description of the exposure control method when the surrounding suddenly becomes dark. It is not clear whether the invention can be applied to sudden darkening of the surroundings, such as when entering a tunnel

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