In this paper, experimental results on single point diamond turning (SPDT) of fused silica glass, using the µ- LAM process is reported. It is shown that with a certain combination of tooling geometry, coolant, and laser beam power, surfaces with roughness values of 20 nm - 30 nm RMS can be achieved. Such surfaces are obtained with spindle speeds of 1000 RPM. All the experiments are done on planar samples. For tool machining track lengths greater than 3 km, a tool wear-land of 10 µm on the flank face of the tool was observed.
Mass production of Ge lenses is a very common operation in the infrared (IR) optics manufacturing industry. The process of choice for production of such optics is single point diamond turning (SPDT). Ge is a very suitable material for SPDT and this gives the ability to produce complex elements with excellent surface finishes (<5 nm RMS). In this paper the application of the Micro-LAM (referred to μ-LAM hereafter) process in SPDT of single crystal Ge is reported. The main idea is to investigate the maximum in-feed rates for a spindle speed of 5000 RPM as function of the tool nose radius and rake angle. Typical industry practice is to machine Ge with a spindle speed of 5000 RPM to 12000 RPM, and finishing in-feed rates between 0.5 μm/rev and 1 μm/rev. It is shown that an increase in the tool nose radius leads to an increase in the maximum in-feed achievable without the appearance of brittle fracture zones on the surface. It is also shown that using larger negative rake angles can also enable higher tool in-feeds without trade-off’s to the surface quality.
The application of microlaser assisted machining of precision optical components made of optical grade single-crystal Si is reviewed. An optical raytracing model is developed and used for predicting the laser interaction with the workpiece. Optical characterization of the system is shown to be in good agreement with that predicted by the model. Using the information from the simulation and experimental validation, the laser-assisted diamond turning of single-crystal Si samples is shown to have exhibited little to no brittle fracture on the surface and the potential of extending the diamond tooling life by 150%.
In this paper, the concept design of the addition of a 3D imaging system to commercially available see-through AR glasses is outlined. The 3D imaging is implemented through the projection of structured infrared light pattern of (λ=1550 nm) dots on a scene in front of the user. The light projector and detector of the light are adjacent to each other on the device frame. The structured light is produced using a diffractive optical element. To equip this 3D imaging system with a lateral sweeping system without the addition of a complex rotating scanner, two right angle prisms are used such that the chord face of each prism is parallel to the other. Given a certain gap between the prisms the angular trajectory of the structured light pattern can be manipulated, thus enabling high quality illumination of the scene at directions other than normal to the aperture of the illuminator. Computer algorithms can be used to calculate the position of each reflected dot given the field of view of the camera. The material of the prisms is a topic under investigation. While one of the prisms has a fixed position, the other is moved linearly away (in the z direction) from the other element using a linear actuator. This linear motion enables a variable gap between the two prisms and scanning the scene for a range of angles as a function of the prism's material properties and detector field of view.