Detail analysis of off-axis aspheric mirror: manufacturing method and process flow

Off-axis aspherical mirror is a non-spherical curved mirror whose center of mirror surface does not coincide with the center of mirror itself. Off-axis aspheric mirrors are widely used in optical systems because they can eliminate spherical aberrations and chromatic aberrations and improve image quality. Special processing techniques and tools are required in the manufacture of off-axis aspheric mirrors.

The main manufacturing methods of off-axis aspheric mirrors are as follows:

1. Grinding method: The process of off-axis asphaltic mirror grinding is completed by semi-automatic or fully automatic way. First, the entire surface needs to be thinned globally. Then, the mirror and the abrasive are placed on the same plane, and the grinding is carried out along the curved surface by means of grinding products or fixtures. This process requires constant measurement and adjustment until the desired accuracy is achieved. Then the surface quality of the surface is achieved by polishing and nanoscale grinding.

2. CMM machining method: CMM (Coordinate Measuring Machine) is a high-precision coordinate measuring machine. The shape of the desired 3D surface is calculated by increment of the coordinate system position after the contact between the zero point and the tool, and then the movement of the machine tool is controlled to process the off-axis aspheric mirror. The advantage of this machining method is that it realizes digital control and measurement, and improves machining accuracy and consistency. However, its disadvantage is that the processing speed is slow and the processing time is longer.

3. Free surface mirror cutting method: By taking the rotation axis of the tool as the degree of freedom, the polishing tool is moved to the required point, and the free surface mirror is cut. The advantage of this method is that the processing speed is fast and the cost is low, but there are some problems, such as the free cutting surface shape can not get the expected effect due to the free cutting of the free surface mirror.

The process of off-axis aspheric mirror manufacturing also includes some necessary process flow, which roughly includes the following steps:

1. Design: By means of mathematical simulation, optical analysis and simulation, the curve shape and many factors of the mirror are analyzed and simulated, and the preliminary design scheme is obtained. In addition, some parameters and requirements for processing and coating processes need to be determined.

2. Material selection: Because off-axis aspheric mirrors need to have characteristics such as high precision and small anisotropy, it is necessary to choose materials with higher quality.

3. Manufacturing and processing: Select one of the manufacturing methods mentioned above, and process and manufacture according to the design requirements.

4. Inspection and testing: test the surface shape, surface quality, refractive index, reflectivity and dispersion to check whether there are problems in the manufacturing process, and then proceed to the next step after determining.

5. Coating: According to the needs of the optical system, coating treatment, including the reflectivity and wavelength range of the entire mirror is adjusted.

The above is a brief introduction to the manufacturing method and process flow of off-axis aspheric mirror. The manufacture of off-axis aspheric mirrors is a difficult and complex process, which requires the cooperation of experts in many fields.