| 摘要 |
PURPOSE:To improve an SN ratio by providing a cylindrical lens in front of an array and by setting the aperture of an image-forming lens smaller than the width of a light responding element. CONSTITUTION:Positive cylindrical lens 5 is arranged in front of linear array 3 so that its generating line will be in parallel to the X axis. Aperture 6 is arranged near image-forming lens 2 and provided with a circular opening. So that the image of the part of aperture 6 perpendicular to the scanning direction of array 3 will be formed on the photodetection of linear array 3 being smaller than the width of array 3, cylindrical lens 5 is closely arranged with the power determined. In this case, althrough the quantity of light as much as only the width of array 3 is used for detection without the cylindrical lens 5, light of wide width reaches onto array 3 because of cylindrical lens 5, thereby improving the sensitivity by the ratio of the increment. |
