This paper investigates the impact of diamond crystal type on single point diamond turning of single crystal silicon oriented at the <111< direction. The sample has a diameter of 85 mm with a concave base radius of curvature of 291 mm. The tools are made of single crystal diamond formed naturally (hereby referred to as natural diamond) and under lab controlled highpressure high-temperature conditions (hereby referred to as synthetic diamond). The tools have similar geometries of 0.5 mm nose radius, -25° rake angle. The natural diamond is oriented such that the top face of the diamond stone is a {100} plane and the cutting occur in the <110> direction relative to the stone. The synthetic diamond stone is oriented in the {100} plane with the cutting happening in the <100> direction. It is seen that, on average, the synthetic tool can cut approximately 38.5% longer distances without inducing significant brittle fracture on the surface.
This paper reports on the possibility of single point diamond turning (SPDT) of an axisymmetric convex aspherical fused silica lens. Due to the relatively abrupt tool wear during SPDT of fused silica, generally the process is not considered to be commercially acceptable. Surfaces created with SPDT are very rough and of no optical functionality. That said the SPDT can be a very convenient method in production of fused silica asphere and freeform optics should the process be amenable to producing relatively smooth surfaces. In this article it is shown that a lens fabricated via conventional fine grinding processes can be SPDT'ed to roughness values below 100 nm RMS and surface form better than 800 nm PV.
This article summarizes laser assisted single point diamond turning (SPDT) of select brittle and hard materials, using the μ-LAM process. These materials all have significant industrial importance in the modern day. It is shown that the μ-LAM process can produce smooth surfaces, with roughness values range from 40 nm RMS down to subnanometer RMS.
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.
This work is a continuation of previously published work on the application of fiber-based tools in precision polishing of optical components. Previous publications mainly focused on understanding how fiber-based tools remove material and the potential of such tools in reducing existing midspatial frequency errors on planar samples. In this work, an exemplary tool consisting of nylon 6/6 fibers is used in a five-axis computerized numerically controlled machine tool to evaluate the tool’s ability to polish nonplanar BK7 components. The five-axis system has an inline slurry feed system which is found to produce higher material removal rates than the nonrecirculatory slurry bath configuration used in earlier polishing tests. Polishing results obtained on planar and spherical surfaces in the five-axis system show close agreement with that predicted via convolution. A finite element model of the fiber’s interaction with a concave surface shows that the calculated local pressure distribution reflects that observed experimentally, thus further supporting the predictable behavior of fiber-based tools.
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.
The design proposed in this abstract, for a monocular see through smart glass, i.e. Design Challenge #1, leverages a varifocal lens to accommodate human eyes with different focusing abilities. The eyepiece is made of three separate segments. The varying focus of the system is achieved by using two freeform Alvarez surfaces. The Alvarez lens proposed here has the advantage of achieving different focal lengths by laterally shearing the optics with respect to each other. As a proof of concept, it is shown that the Alvarez lenses provide the ability of a constant performance for different eye conditions.
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