Reference and test waves are directed in a common path mode in a fiber tip diffraction interferometer. A first fiber can be used to generate the reference wave and a second fiber can be used to generate the test wave. Each fiber can include a single mode fiber tip that defines a wedge at an end without a coating on end surface or a tapered fiber tip. The fiber tip diffraction interferometer can include an aplanatic pupil imaging lens or system disposed to receive both the test wave and the reference wave and a sensor configured to receive both the test wave and the reference wave.

Reference and test waves are directed in a common path mode in a fiber tip diffraction interferometer. A first fiber can be used to generate the reference wave and a second fiber can be used to generate the test wave. Each fiber can include a single mode fiber tip that defines a wedge at an end without a coating on end surface or a tapered fiber tip. The fiber tip diffraction interferometer can include an aplanatic pupil imaging lens or system disposed to receive both the test wave and the reference wave and a sensor configured to receive both the test wave and the reference wave.

System and methods are provided for characterizing an internal surface of a lens using interferometry measurements. Sphere-fitting a distorted radius determines distorted pathlengths. Ray-tracing simulates refraction at all upstream surfaces to determine a cumulative path length. A residual pathlength is scaled by the group-index and rays are propagated based on the phase-index. After aspheric surface fitting, a corrected radius is determined. To estimate a glass type for the lens, a thickness between focal planes of the lens surfaces is determined using RCM measurements. Then, for both surfaces, the surface is positioned into focus, interferometer path length matching is performed, a reference arm is translated to stationary phase point positions for three wavelengths to determine three per-color optical thicknesses, and ray-tracing is performed. A glass type is identified by minimizing an error function based on optical parameters of the lens and parameters determined from known glass types from a database.

System and methods are provided for characterizing an internal surface of a lens using interferometry measurements. Sphere-fitting a distorted radius determines distorted pathlengths. Ray-tracing simulates refraction at all upstream surfaces to determine a cumulative path length. A residual pathlength is scaled by the group-index and rays are propagated based on the phase-index. After aspheric surface fitting, a corrected radius is determined. To estimate a glass type for the lens, a thickness between focal planes of the lens surfaces is determined using RCM measurements. Then, for both surfaces, the surface is positioned into focus, interferometer path length matching is performed, a reference arm is translated to stationary phase point positions for three wavelengths to determine three per-color optical thicknesses, and ray-tracing is performed. A glass type is identified by minimizing an error function based on optical parameters of the lens and parameters determined from known glass types from a database.

Methods, apparatus and systems for achieving efficient optical design are described. In one representative aspect, a method for optical design includes introducing a light source into the optical system. The light source emits illumination that is characterized as a point source, a collimated illumination, or a superposition of one or more point sources or one or more collimated illuminations. The light source is represented by a vector field comprising a plurality of vectors. The method also includes defining each optical surface of the optical system based on the vector field of the light source, tracing a plurality of rays that propagate from the light source, traverse through the optical system and reach a predetermined target or targets, and determining whether an illumination or an image characteristic at the predetermined target or targets meets preset design requirements.

Methods, apparatus and systems for achieving efficient optical design are described. In one representative aspect, a method for optical design includes introducing a light source into the optical system. The light source emits illumination that is characterized as a point source, a collimated illumination, or a superposition of one or more point sources or one or more collimated illuminations. The light source is represented by a vector field comprising a plurality of vectors. The method also includes defining each optical surface of the optical system based on the vector field of the light source, tracing a plurality of rays that propagate from the light source, traverse through the optical system and reach a predetermined target or targets, and determining whether an illumination or an image characteristic at the predetermined target or targets meets preset design requirements.

An on-machine measurement device that locates a tip position of a blade of a machining tool provided on a machining device includes: a measurement unit configured to measure, in a workpiece that has been machined by the machining tool, a height of a reference plane not machined by the machining tool and a height of a machined surface machined by the machining tool; and a locating unit configured to locate the tip position of the blade of the machining tool based on information on a machining depth specified at the time of machining of the workpiece, and the height of the reference plane and the height of the machined surface that are measured by the measurement unit.

A rocker arm grading system can comprise a grading tool. The grading tool can be used with a rocker arm to measure aspects of the rocker arm and determine a resulting valve lift. The grading tool can comprise a rocker arm jig comprising a pivot peg and a valve peg. A cam jig can comprise a cam arm. A cam pin can be mounted in the cam arm. A rocker arm can be removably mounted to the rocker arm jig. The rocker arm can comprise a radius on a bearing surface. A cam edge of the cam pin can press against the bearing surface. At least one measuring device comprising a wavelength emitting device paired with a wavelength detecting device can be configured to measure the radius of the bearing surface with respect to the pivot peg.

A rocker arm grading system can comprise a grading tool. The grading tool can be used with a rocker arm to measure aspects of the rocker arm and determine a resulting valve lift. The grading tool can comprise a rocker arm jig comprising a pivot peg and a valve peg. A cam jig can comprise a cam arm. A cam pin can be mounted in the cam arm. A rocker arm can be removably mounted to the rocker arm jig. The rocker arm can comprise a radius on a bearing surface. A cam edge of the cam pin can press against the bearing surface. At least one measuring device comprising a wavelength emitting device paired with a wavelength detecting device can be configured to measure the radius of the bearing surface with respect to the pivot peg.

A system for in-situ measurement of a curvature of a surface of a wafer comprises: a multiwavelength light source module, adapted to emit incident light comprising a plurality of wavelengths; an optical setup configured to combine the incident light into a single beam and to guide the single beam towards a surface of a wafer such that the single beam hits the surface at a single measuring spot on the surface; and a curvature determining unit, configured to determine a curvature of the surface of the wafer from reflected light corresponding to the single beam being reflected on the surface at the single measuring spot.