Diffractive aspheric surface is a kind of optical element with special shape. Its curvature varies unevenly in different directions, which is different from the traditional spherical surface. On the diffractive aspheric surface, the light will diffract when passing through the surface of the aspheric surface. This diffraction will change the wave shape of the light, so as to achieve specific optical functions and improve the imaging quality and performance. Diffractive aspherical surface
Diffractive optical elements are based on the diffraction effect of light. They modulate the incident wavefront through the surface micro relief structure to obtain the desired wavefront. In order to realize more abundant optical functions and increase the freedom of optical design, the microstructure of diffractive elements is usually superimposed on the aspheric substrate.
In the optical design software CODE V, the rotationally symmetric diffractive surface is expressed as:
Where: n1 and n2 are the refractive index of the medium behind the diffractive plane and the refractive index of the medium behind the diffractive plane respectively; λ 0 is the equivalent design wavelength; C1, c2 and c3 are the second, fourth and sixth order phase coefficients of the diffractive surface respectively; HOR is diffraction times. It can be seen from the formula that the diffraction surface equation covers the aspheric substrate and the characteristics of diffraction microstructure, and its optical design meaning is shown in the following figure. Diffractive optical element is to fold the continuous refractive surface into a diffractive structure to realize the miniaturization and lightweight of the optical system under the condition of achieving the same optical performance.
Diffractive aspherical surfaces are widely used in various domains, including optical lenses, microscopes, photographic lenses, laser beam shaping, astronomical telescopes, etc. They play an important role in scientific research, medical diagnosis, industrial testing, communication transmission and other domains. Through accurate optical design and processing technology, diffractive aspheric lenses can achieve broader field of view, higher resolution and better aberration control.
Aspherical diffractive multifocal intraocular lens
In the optical domain, the measurement of diffractive aspherical lenses has always been a challenging task, with the following difficulties:
1. High requirements for measurement accuracy: non-contact measurement methods usually cannot directly obtain accurate measurement data like contact measurement, and any small error in the measurement process may affect the final optical effect;
2. Strict measurement environment requirements: due to the complex size and shape of diffractive aspheric parts, certain environmental conditions, such as noise, vibration, temperature, etc., need to be maintained during the measurement process;
3. Wide measuring range: the measuring range of diffractive aspheric surface needs to cover the whole surface, including various curvatures and dimensions, which requires that the measuring equipment has sufficient measuring range and accuracy;
4. Difficult data processing: the measured data needs to be processed and analyzed in a complex way to obtain accurate surface shape and size information, which requires corresponding data processing skills and experience.
In the past, the industrial measuring equipment that can detect the parameters of high-precision diffractive aspheric lenses in China basically relied on imports.
SJ5900 optical profiler
SJ5900 optical profilometer solution:
1. High precision contact measurement: ultra-high precision nano diffractive optical measurement system is adopted, and the instrument precision reaches a high level (instrument straightness ≤ 0.25 μ m/200mm, large range topography micro contour Pt ≤ 0.3 μ m). High precision diffractive aspheric surface measurement is achieved through contact lens scanning of the measuring needle;
2. Integrated closed type: the integrated closed type appearance reduces external noise, and the air flotation shock absorption system isolates environmental vibration;
3. Measurement range: X travel can reach 200mm, and the scanning height of the probe can reach 24mm, basically covering the effective aperture range of most aspherical surfaces;
4. Customized personalization scheme: it can provide personalized customization services, and design and adjust according to the specific needs of users to meet the requirements and applications of users.
5. Intelligent software system:
1) The powerful data processing system can process the measured data in real time and provide detailed data analysis and report, which is easy to operate. Used for correction of manufacturer's production equipment
2) Accurate analysis of step parameters (width and height) in diffraction zone
3) Intelligent display of comparison diagram of theoretical curve and measured curve (original contour curve, shape error curve)
4) Calculate the parameters with tolerance for each diffraction zone: angle, height, shape error, pt, etc
Measurement example
Diffraction surface measurement
Diffraction surface analysis
Scan original image
Comparison between measured curve and theoretical curve shape error results
Shape error results
Diffraction Shape Error Results
Diffraction surface measurement report: personalized measurement report can be customized, and data can be exported for production equipment correction.
Whether it is optical system manufacturing, laser equipment field or scientific research, SJ5900 optical profiler is a sharp tool to achieve high-quality production and improve production efficiency.
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