Design Of Achromatic And Apochromatic Flattening Linear Objective Lens

As an important part in the laser scanning system, f-θ lens is widely used in single wavelength laser scanning, and also has a wide range of applications in double wavelength or multi-wavelength scanning system such as laser color printing, biological sample scanning and so on. In this paper, an achromatic f-θ lens and an apochromatic f-θ lens are designed and the image quality is analyzed.Transmission characteristics of gaussian beam are analyzed briefly. The design requirements that using the beam waist radius to constraint geometric dispersion spot RMS radius and lateral chromatic aberration, using Rayleigh distance in image space to constraint field curvature, astigmatism and spherical aberration, using the ratio of the beam waist diameter and image height of f-θ lens to constraint nonlinearity is put forward.According to the above requirements, six-chip achromatic f-θ lens and seven-chip apochromatic f-θ lens are designed. Achromatic f-θ lens is telecentric in image space, the longitudinal chromatic aberration between wavelength of532nm and wavelength of632.8nm is corrected. This lens can be used for dual wavelength laser biological scanning system. The f-θ lens also can be used for general scanning optical system after we just shorten the after-working distance. Apochromatic f-θ lens’ secondary spectrum of wavelength of532nm,632.8nm, and680nm is corrected. The optical structure and aberrations such as field curvature, astigmatism, nonlinearity, dispersion spot RMS radius and spherical aberration are analyzed. Finally, we give an instance in dispersion spot RMS radius and nonlinearity to discuss the influence on image quality of the off-focal image plane.