![]() If a diffractive element is placed behind the lens of the module, many spots that can form a complex light pattern are observed. Designing a DOEĪ laser module often has an adjustable lens system that creates a focused spot on a screen. Because only the light-pattern intensity distribution is relevant to the application, the phase of the light field is an important degree of freedom in the numerical computations for the DOE design. The underlying assumption that the light field is coherent and monochromatic is fulfilled in sufficiently good approximation as long as laser sources are modeled. In the easiest case-referred to as Fraunhofer approximation-the diffraction pattern can be computed simply by a Fourier transformation. Diffraction theory, which is the key to the theoretical treatment of this matter, can be used to calculate how a certain light wave of finite aperture size will be altered during propagation.ĭiffraction computations are based on the electromagnetic-field representation of the light field, not only on its intensity distribution. When a laser beam is transmitted through a diffractive optical element (DOE), it can be transformed into an almost arbitrary light pattern in the observation plane. The diffractive elements that produce these complex light patterns must be designed and fabricated in a sophisticated way. Examples include viewfinder patterns, arrangements of multiple lines or circles that can be used for three-dimensional (3-D) surface measurements, and patterns that represent rulers or scales. A detailed discussion of such aspects is done in the earliest stages of product development.Diffractive optical elements can be used to generate complex light patterns with precisely defined dimensions in a specified plane. regarding achievable resolution and cost-effectiveness. However, chosing an amplitude DOE may have application-dependent advantages, e.g. regarding the suppression of unwanted diffraction orders and achievable diffraction efficiency. The utilization of phase masks has certain general advantages, e.g. An example of the appearence of such a mask is shown in the figure below. For highervolume productions we also employ the lithographical production of binary and multi-level phase masks. These masks are made of cromium on quartz glass, a resolution of 500nm can be reached in the hologram plane. Eureca also offers prototyping and volume productions of thick phase holograms based on photopolymer.Īs a medium suitable for productions from prototypes to high volumes we offer high-resolution binary amplitude masks. High-resolution film based on silver halides are a powerful tool for prototyping and low-volume productions, as well. For prototyping we utilize holographic displays, which allow for fast evaluations and proof-of-concept studies. Ways of DOE Production from Proof of Concept to Final ProductĮureca offers a variety of ways of prototyping and manufacturing DOEs. The knowledge of Eurecas regarding the different manufacturing processes for DOEs also ensures that all steps from first evaluations to final production are interrelated at its best. Eurecas also utilizes different standard procedures for the generation of diffractive structures, among them FFT, IFTA and ASPW. Our detailed knowledge of physics and wide experience in using custom algorithms for wavefront propagation makes sure that precise and cost-effective ways of hologram-generation are selected. Once general specifications are found, the best way of generating the required target structures is chosen. At this point, Eurecas's strong competences in image simulation are particularly important. In this step of development, numerical reconstructions from exemplary diffractive structures can help determining which specifications are required. regarding size of reconstructed pattern structures, homogeneity of illumination, signal-to-noise ratio, necessary diffraction angles and diffraction efficiency. When the development of a customized DOE is considered, the first step usually is the determination of precise specifications, e.g. Project Steps from Specifications to Production
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