The openness of following case has been allowed by our clients with exception of key parameters, which is only 90% of complete design process.  I.Application To measure the thread profile accurately. II. Requirements Applicable wavelength: 500 ~ 600 nm Magnification: 20 x Lens quantity: no more than 6 pieces Lens maximum diameter: less than 35 mm Lens facial form: all spherical Lens material: optical glass Projection distance: 1 m Biggest diameter:50 mm Distance between tested object and first lens: 50~ 70 mm F No: F / 2.8 Maximum distortion: less than 0.5% Resolution ( tested object) : more than 60lp/mm@0.3 III. Features It shall design object side telecentric system, namely the pupil is located in infinity. The characteristics of image beam is that the chief ray of incident beam is parallel with optical axial. Therefore, there will be no measuring error when there is positional deviation for the tested object( within deep scope). Since the projection distance is far bigger than back intercept, so when we use optical softwares to design, make projection screen as an object while determinand as image. Since it is a measuring system, distortion demanding level is comparatively hihger than normal objective lens. IV. Result