To measure the quality of optical surfaces, one of the most used methods is the deflectometry. To implement this technique, a screen is used to choose some incident rays on the surface under test. Subsequently, the intersection of the rays is measured, after having passed through the surface, in a detection plane perpendicular to the optical axis. With the coordinates of the points in the detection plane, the normal vectors are determined in each point of the surface under test. The process is simple if the incident rays are chosen in a configuration called null, that is, in the detection plane the measured points will be distributed in a uniform configuration, rectangular, circular, radial, etc. In this work we present the numerical simulations, considering an incident spherical wavefront in the null screen that is placed at an arbitrary position between the source and the flat surface of an aspheric lens that was used in the experimental arrangement. In the simulations it is expected to obtain a uniformly distributed arrangement of spots, which will be compared with the experimental results.
One of the most used methods to measure the quality of optical surfaces by light transmission is the de ectometry. To implement this technique, an arbitrary ray selector is used to choose some incident rays. Measuring the intersection of the rays refracted by the surface, in a posterior detection plane perpendicular to the optical axis, the normal at the surface under test, it is determined. Whith measurement points, the shape of the surface is determined by their integration. The process is simple if the incident rays are chosen in a called null configuration, since it is expected that all refracted rays will strike a predetermined ordered array in the detection plane. To numerical calculation we using an ideal surface on this test. In order to full measuare of the surface on simulation, we used vector form of exact ray tracing. To carry out the necessary numerical simulations for a null screen, we considering a point light source and the selector placed in arbitrary position between the point source lens of the test. Some numerical simulations are shown and are compared with experimental results.
We present the numerical simulation of a ray selector with a uniform distribution. This selector shall be used in a deflectometry arrangement and the detection plane of spots necessary in the deflectometry shall be placed at an arbitrary distance from the lens under test. To perform this task, the vector form of the exact ray tracing is used through a lens and from these positions determine the shape of the convex surface of the lens. This program is flexible and can be used on other types of optical surfaces, and different ray distribution, including null distribution. The first preliminary results are shown below.
In order to evaluate either qualitative or quantitatively the shape of fast plano-convex aspheric lenses, a method to design null screens type Hartmann is proposed. The null screens are formed with non-uniform spots, which allows to have uniform images at detection's plane. The screens are printed on a foil sheet and placed in front of the lens under test, they are illuminated with a collimated monochromatic beam propagating along the optical axis, in such a way that through the process of refraction will form a uniform spot patterns which are recorded at a predefined plane of detection. Finally, processing properly its image recorded we could be able to get a quantitative evaluation of the lens under test. The designs of these null screens are based on the equations of the caustic surface produced by refraction. A preliminary test for a fast plano-convex aspheric lens with F=# = 0:8 is presented in this work. This method could also be applied to alignment of optical systems.
We have obtained a formula to represent the wavefront produced by a plano-convex aspheric lens with symmetry of revolution considering a plane wavefront propagating parallel to the optical axis and impinging on the refracting surface, it is called a zero-distance phase front, being it the first wavefront to be out of the optical system. Using a concept of differential geometry called parallel curves it is possible to obtain an analytic formula to represent the wavefront propagated at arbitrary distances through the optical axis. In order to evaluate qualitatively a plano-convex aspheric lens, we have modified slightly an interferometer Tywman-Green as follow: In the reference beam we use a plane mirror and the beam of test we have used a spatial light modulator (SLM) to compensate the phase produced by the lens under test. It will be called a null phase interferometer. The main idea is to recombine both wavefronts in order to get a null interferogram, otherwise we will associate the patterns of the interferogram to deformations of the lens under test. The null phase screens are formed with concentric circumferences assuming different gray levels printed on SLM.
In order to evaluate either qualitative or quantitatively the shape of fast plano-convex aspheric lenses, a method to design null screens type sub-structured Ronchi is proposed. The null screens are formed with nonuniform curves which allows us to have both thin and thick monochrome strips between contiguous curves. The screens are printed on a light transmission modulator and placed in front of the lens under test, they are illuminated with a collimated monochromatic beam propagating along the optical axis, in such a way that through the process of refraction will form a uniform straight fringes pattern which are recorded at a predefined plane of detection, finally processing its image recorded we could be able to get a quantitative evaluation of the lens under test. The designs of these null screens are based on the equations of the caustic surface produced by refraction. The null screens can be printed in gray levels on a light transmission modulator depending on the applied voltage on it. A preliminary test for a fast plano-convex aspheric lens with F=# = 0:8 is presented in this work. This method also could be applied to alignment of optical systems.
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