Abstract Information projection using laser-based illumination systems in the automotive area is of keen interest to enhance communication between road users. Numerous work on laser-based front end projection employing refractive and reflective optics has been reported so far, while for rear end illumination efforts are more scarce and a different optical design concept due to limited volumetric size and field of view regulations is required. Here, we report on a new and versatile approach for a laser-based rear end lighting system for automotive application which enables projection of information or signals to support other road users. The design is based on thin diffractive optical elements projecting the desired patterns upon illumination. Also, for protection of the road users from the steering laser beam, a diffusive back projection screen is designed to project information while fulfilling both the field of view and safety requirements. The projection system is based on a periodic diffusive structure made of an array of biconic lenses with sizes in the millimeter range. The field of view (FOV) from the simulated lens arrays complies with the angular requirements set by the Economic Commission for Europe (ECE). As a proof of concept, the diffusive screen is fabricated using microfabrication technology and characterized. In future, the screen will be combined with thin diffractive optical elements to realize an entire integrated projection system. The function of this element is to diffuse the steering laser beam and display the desired pattern on its outer surface. Also, regulations set by the Economic Commission for Europe (ECE) for the field of view (FOV) must be considered [14]. In order to realize a diffuser with predefined FOV, different concepts based on grounded glass with irregular structures as well as engineered dif- fusers for beam shaping have been reported [15 –16]. Also, the use of microlens array-based diffusers in LED street- lamps to increase uniformity and decrease glare effects have been achieved [17]. Furthermore, tandem microlens arrays producing top hat illumination patterns for epifluorescence microscopy and quantitative widefield imaging have been discussed [18]. Finally, randomly distributed microlens arrays have been employed for diffusing light beams at large angles and uniformities [19]. In this paper, we report on the design and the realization of a rear end automotive lamp system based on diffractive optics. The design of the DOE microstructure is based on binary gratings computed using a simple optimization algorithm. The fabrication of dif- fractive optical structures in polymer is achieved in a two- step process. The latter then diffuses the intense diffracted laser beams at higher angles and ensures safety of other road users. Also, the diffuser projects the desired pattern in a required angular FOV set by the Economic Commission for Europe (ECE). As for the intensity of the light, it is dependent on the illumination source employed. The standard intensity distribution of, for example, rear end S3 stop lamps defined in the ECE regulations is depicted in Figure 2(A). The standard light distribution displayed in Figure2(A) shows intensity distribution from −10° to +10° and −5° to +10° in horizontal and vertical direction, respectively. The lens design goal is to spread the light into a rectangular shaped profile as depicted in Figure 5 and described by the regulations mentioned in Section 2. The diffracted beam from the diffractive optical element is projected onto the diffuser lens which spreads the light into a rectangular field of view, see Figure 5. For designing purposes, a diffuser surface with irregular structure pro file and size leads to less freedom in design and optimization. In addition, the optimization procedure takes longer. Structures with regular structure profiles such as microlens arrays (MLAs) allow for variation in the output intensity distribution by changing lens shape parameters and usually require less optimization time. We have used Zemax Optics Studio software to simulate the diffuser shape for the desired FOV and the intensity pro file. Multi- ple beam diverging lens pro files can be used such as biconcave or plano-concave lenses. For biconcave lens arrays the light beam can diffract at larger angles compared to the plano-concave lens design; however the computa- tion time is increased due to multiple interfaces. On the other hand, plano-concave lens arrays require less computation time and form the light beam into a square shape pro file. To achieve the rectangular intensity distri- bution, as shown in Figure 5, a biconic lens is selected where the conic constant and base radius of both the x and y axes can be varied and used as optimization parameters. Hence, A flat top beam is required and simulated to ensure that the diffuser distrib- utes the incoming laser light at a wavelength of 638μm into a desired rectangular shape and desired intensity pro file, see Figure 6, rather than expanding the Gaussian beam profile. The flat top beam is used to illuminate the diffusive screen to simulate the desired rectangular FOV, see Figure 7. For the simulation of the diffuser lens, an array of lenses having an area of 12 × 12 cm 2 is created. The material used for the lens also plays an important role with regards to transmission ef ficiency of the lenslet array. Figure 7: Flat top beam generation through the diffuser (right) achieved by a Gaussian beam used for illumination (left). M.S. Khan et al.: Diffractive optics based automotive lighting 53 diffuser surface. This loss is due to fabrication artifacts. The diffuser is designed with a flat top beam, and the required beam pro file is realized by an appropriate design of the DOEs. As by design, the diffuser material is N-Lak 34 glass having a refractive index of 1.72, a difference in the final intensity distribution is observed in comparison the simulated distribution, see Figure 10(B).