| 摘要 |
PURPOSE:To achieve a higher measuring accuracy, by arranging an optical element near an image formation lens to defocus an image vertical to the direction in which a photo detector is arranged in a strip. CONSTITUTION:An image formation lens 3, a strip-like photo detector 2 having a double parallelogramic aperture, a differential amplifier 4 and the like are used to measure the relative speed such as moving speed of an automobile on a road. A cylindrical lens (optical element) 21 is provided near the image formation lens 3 to defocus as image vertical to the direction in which the photo detector 2 is arranged in a strip to remove the side lobe thereby achieving a higher measuring accuracy.
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