We propose a microoptical approach to ultra-compact optics for real-time vision systems that are inspired by the compound eyes of insects. The demonstrated module achieves 720p resolution with a total track length of 2.0 mm which is about 1.5 times shorter than comparable conventional miniaturized optics. The partial images that are separately recorded in multiple optical channels are stitched together to form a final image of the whole FOV by means of image processing. The microlens arrays are realized by microoptical fabrication techniques on wafer-level which are suitable for a potential application in high volume e.g. for consumer electronic products
Miniaturized imaging systems combining an ultra-compact form factor in combination with the ability of refocusing and depth imaging have gained much interest in the field of mobile imaging. Therefore, artificial compound eye cameras are an extremely promising approach for the realization of compact monolithic camera modules on wafer level. Up to now, their imaging performance was limited to low resolution in the range of VGA format according to fabrication constrains given by the established microoptical fabrication methods, namely the reflow of photoresist. In order to overcome these classical limitations, the use of refractive freeform arrays (RFFA) instead of conventional microlens arrays is inevitable. To enable high volume and cost efficient mass production of artificial compound eye cameras for mass markets like the consumer electronics industry, their fabrication on wafer level is essential, but has not been published up to now. We present a wafer level based process chain enabling the fabrication of these elements for the first time.
In this contribution, a microoptical imaging system is demonstrated that is inspired by the insect compound eye. The array camera module achieves HD resolution with a z-height of 2.0 mm, which is about 50% compared to traditional cameras with comparable parameters. The FOV is segmented by multiple optical channels imaging in parallel. The partial images are stitched together to form a final image of the whole FOV by image processing software. The system is able to acquire depth maps along with the 2D video and it includes light field imaging features such as software refocusing. The microlens arrays are realized by microoptical technologies on wafer-level which are suitable for a potential fabrication in high volume
Artificial compound eye cameras are an attractive approach to generate imaging systems of maximum miniaturization. Their thickness can be reduced by a factor of two in comparison to miniaturized single aperture cameras with the same pixel size and resolution. The imaging performance of these systems can be improved significantly by the use of micro-optical refractive freeform arrays (RFFA). Due to the complexity of these non-symmetric surface profiles with sag heights larger than 50 µm in combination with extreme profile accuracies better than λ/14 (rms), there is no dedicated fabrication technology currently available. In the presented research, significant improvements in the fabrication of these elements with laser lithography were reached. Therefore, a laser lithographic process based on several coating steps in combination with a multiple exposure strategy was developed that is suitable for the fabrication of arbitrary freeform structures with sag heights up to 60 µm. In order to minimize surface deviations caused by unavoidable process nonlinearities, a compensation strategy based on an empirical process model is used. The achievable accuracy of the proposed method and its limitations were investigated by fabricating a spherical micro lens array for demonstration. The fabricated elements possess a shape deviation of less than 1.3 µm (rms) and can be used as master structures for a subsequent replication process in order to realize a cost efficient mass production of artificial compound eye optics on wafer level.
There is a huge demand on miniaturized cameras in the field of mobile consumer electronics. These cameras are currently based on miniaturized single aperture optics. In order to further decrease the thickness of miniaturized camera systems, a multichannel imaging principle needs to be used. These artificial compound eye cameras permit a further decrease in thickness by a factor of two in comparison to miniaturized single aperture optics with same resolution and pixel size. Their fabrication process is currently based on the reflow of photoresist. Due to physical limitations of this technique, only spherical and ellipsoidal surface profiles of the single lenslets are achievable. Consequently, the potential for correcting optical aberrations is restricted leading to limited image quality and resolution. This can be improved significantly by the use of refractive freeform arrays. Due to the non-symmetrical and aspherical surface shapes of the single lenslets, the fabrication by the reflow of photoresist is no longer possible. Therefore, we propose an approach for the fabrication of these structures based on the combination of an ultra-precision machining process together with a microimprinting approach.ophthalmic fs-surgery
We designed, fabricated, and characterized three-level transmission gratings in the resonance domain with reduced shadowing losses based on a three-wave interference mechanism. A new technological approach allows for fabrication of homogeneous and large area multilevel gratings without spurious artifacts. To our knowledge, the measured efficiency of 86% exhibits the largest value yet reported for a multilevel transmission grating in the resonance domain close to normal incidence.
The fabrication of microstructures with continuous surface profiles and very large sag heights by a laser lithographic process on a commercially available laser lithography system is presented. The fabricated structures possess sag heights up to 60 µm with a pitch of 400 µm. Fabrication imperfections due to nonlinearities in the photoresist response and the isotropy of the development process have been compensated in the exposure data to minimize profile deviations. Therefore, an empirical process model is proposed based on experimentally determined development rates. The achievable accuracy of the data pre shape and exposure method as well as their limitations are discussed
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.