Currently, maintaining image quality during conjugate change is most frequently achieved through careful lens design with the multiconfiguration optimizing method and physical shifts of the lenses within the system such that the system remains in focus. However, in applications with operational limitations, such as endoscopy where the space available cannot allow for moving parts, the lens system needs to be designed such that the system is in focus over a wide range of conjugates. A lens design method that is integrable into existing commercial lens design software is presented. This method derives and maintains an optimal condition for astigmatism and distortion to control and reduce the overall aberration variation during the conjugate change, and extends the depth of field of the system. A side-by-side lens design comparison between the method illustrated in this study and the conventional lens design method commonly employed by designers of zoom lenses is also presented and is demonstrated to produce better results in designing conjugate change optical systems.
There always exist some new challenges for lens designers to keep their old-line technology update. To minimize lens
volume is one of the most notified examples. In this paper we designed a single thick lens, constructed by using one
oblique (reflective) surface, apart from two conventional refractive surfaces, to bend the optical path of the optical
system to achieve this goal. Detail design procedure, including system layout and lens performance diagrams, will be
Following the first order layout, we applied aspherical form to the two refractive surfaces in order to correct the spherical
aberration up to an acceptable condition. Then, the reduced aberrations such as coma, astigmatism, field curvature and
distortion can easily be corrected with some calculations related to spherical aberration as shown in the publication of H.
H. Hopkins (1950). Plastic material is used in the design, because the aspherical surfaces can then be manufactured in a
more cost effective way. The final specification of the design is: EFL is 4.6 mm, the F number is 2.8, the over all
thickness of lens is 3.6 mm, its MTF is 0.3 at 227 lp/mm in center field and chief ray angle is less than 15 degrees. Lens
data as well as optical performance curves are also presented in the paper. In conclusion we have successfully finished a
mega-pixel resolution lens design and its overall thickness is compatible with the state of the art.