u03c6 4 as shown in fig2 c and the light intensity gradually decreases around the area u03c6 4 and becomes completely zero in an area u03c6 41 the transverse axis u03b8 of fig2 c represents the angle of view by arranging such element lens systems at a predetermined interval the time integrated exposure distribution in the image plane is made uniform now the various elements of the bar lenses will be described in detail in fig2 a and b the curvature radius of the first surface of the first bar lens 1 i e the surface thereof which is adjacent to the object side is expressed as r 1 the curvature radius of the second surface of the first bar lens i e the surface thereof which is adjacent to the image side is expressed as r 2 a negative amount in the figures the center thickness of the lens i e the thickness of the lens between the first and the second surface thereof along the optical axis is expressed as d 1 39 and the main refractive index of the material of this lens i e the refractive index thereof for a typical design wavelength is expressed as n 1 39 also the effective diameter of this lens is represented as u03c6 1 the size of the object 4 39 is represented as u03c6 0 the size of the intermediate image 6 formed by this lens is represented as u03c6 2 the distance from the first surface of this lens to the object 4 39 is expressed as s 1 a negative amount in the figures and the distance from.