Vehicle tracking control for continuously detecting the distance and direction to a preceding vehicle irrespective of background dark/light distribution

An automobile radar apparatus comprising:

• light source means installed at a predetermined position on a rear side of a preceding vehicle, for projecting light backwards;
• a pair of spaced-apart light-receiving optical systems separately positioned on a front side of a self-vehicle (tracking vehicle), each of said optical systems having a respective light-receiving light path for receiving and focusing the light emitted from said light source means into an image;
• at least one photoelectric transducer provided at a focal plane of each light-receiving light path, for converting said focused image into electrical output signals;
• image formation position calculating means for calculating image formation positions in a horizontal direction at the focal plane with respect to the two light-receiving paths based upon outputs of the photoelectric transducer(s);
• rotating means for rotating said light-receiving optical systems in the horizontal direction, and,
• angle detecting means for detecting a turning angle of said light-receiving optical system driven by the rotating means,
• wherein said light-receiving optical systems are rotated in response to an output from said image formation position calculating means to realign the light-receiving paths of said light-receiving optical systems with said light source, a direction of the preceding vehicle is calculated based on an output from said angle detecting means, and a distance up to the preceding vehicle is calculated based on the output from said image formation position calculating means.