OBJECTIVE AND SCANNER USING SAID OBJECTIVE

摘要

PURPOSE: To constitute a small and light weight scanner by recessing both first and second refracting faces as seen from the side of an object and making its focal distance rather much than thickness along an optical axis, so as to make the second refracting face a non-spherical surface. CONSTITUTION: Both the first and second refracting faces 22 and 23 are recessed as seen from the side of the object, and the second refracting face 23 is made an aspherical surface. The face 22 is provided with a divergent effect to a divergent beam 31, and as the result of this an incident beam furthermore diverges within a lens main body part to pass through the whole refracting face 23. The second face 23 is provided with an intense grading effect and grades the beam as the scanning spot 32 of a diffraction limit. Consequently, the focal distance regulated as a distance between a focal point F on an object side and a principle point H is much shorter than the thickness in the direction of the light axis of the objective lens. Thereby the device is made to be an extremely compact and rugged structure.