For this design, an optical lens composition form of 7G2GM (7 Glass Lenses + 2 Glass-Molded Aspherical Lenses) is adopted.

Optical Design of Projection Lens (Initial Structure)

This article shares the initial structure of the optical design for a projection lens, with specific parameters as follows:


  • The front group is mainly responsible for aberration correction corresponding to the field of view (FOV) and undertakes the function of rapidly reducing the FOV angle. It primarily adopts a separated lens configuration.
  • The rear group focuses on aberration correction related to the aperture, mainly including spherical aberration and chromatic aberration. It mainly uses double cemented and separated lens configurations.

The optical design results of the initial structure are as follows:

The lens data are as follows:

                        Figure 1: Lens Data


Figure 2: Lens Data

Lens Structure

1、Architecture Composition

Common retrofocus architectures generally include a front group and a rear group. A simple structure consists of two negative lenses in the front group and one double cemented lens in the rear group (located near the diaphragm).

2、The optical system architecture used in this design adopts a "front group (5 lenses) + rear group (4 lenses)" structure, where:


             Figure 3: 2D Structural Diagram of the Lens

                         Figure 4: Spot Diagram

                              Figure 5: MTF Curve (FFT)

                        Figure 6: Field Curvature and Distortion Diagram

                                      

Figure 7: Lateral Chromatic Aberration Diagram

Optimization Ideas
  1. 1、Prioritize constraints on total length, boundaries, distortion, and chief ray angle.
  1. 2、Ensure no conflicts between constraints; if optimization stagnates, appropriately relax constraints.

  1. 3、Under the default merit function, optimize the RMS (Root Mean Square) to around 1 pixel first, then proceed with MTF optimization.

  1. 4、For MTF optimization, adopt a local optimization method; do not attempt to optimize too many parameters at once.