Multi-aperture optics for wafer-level cameras

Abstract

Wafer-level optics is considered to yield imaging lenses for cameras of the smallest possible form factor. The high accuracy of the applied microsystem technologies and the parallel fabrication of thousands of modules on the wafer level make it a hot topic for high-volume applications with respect to quality and costs. However, the adaption of existing materials and technologies from microoptics for the manufacturing of millimeter scale lens diameters led to yield problems due to material shrinkage and z-height accuracy. A multi-aperture approach to real-time vision systems is proposed that overcomes these issues because it relies on microlens arrays. The demonstrated prototype achieves VGA (Video Graphics Array, 640×480 pixels) resolution with a thickness of 1.4 mm, which is a thickness reduction of 50% compared to single-aperture equivalents. The partial images that are separately recorded in different channels are stitched together to form a final image of the whole field of view by means of image processing. Distortion is corrected within the processing chain. The microlens arrays are realized by state-of-the-art micro-optical fabrication techniques on wafer level that are suitable for a potential application in high volume, e.g., for consumer electronic products

Artificial compound eye: a survey of the state-of-the-art

“…The prototype of (Tanida et al 2000) planar artificial compound eyes is either apposition compound eye or superposition compound eye. To date, a lot of planar artificial compound eyes have been proposed (Tanida et al 2000;Duparré et al 2004b, a;Duparré and Wippermann 2006;Duparré and Völkel 2006;Duparré et al 2005dDuparré et al , a, 2004cDuparré et al , 2005bWippermann et al 2005;Brückner et al 2007Brückner et al , 2008Druart et al 2008;Brückner et al 2010a, b;Bräuer et al 2011;Brückner et al 2011;Meyer et al 2011;Stollberg et al 2009;Duparré et al 2008;Druart et al 2009;Di et al 2009;Leitel et al 2010;Ueno et al 2013;Brückner et al 2010c;Ogata et al 1994;Carr et al 2004;Hornsey et al 2004;Kinoshita et al 2005;Christensen et al 2006;Wippermann et al 2006;Yang et al 2009;Sieler et al 2010;Fallah and Karimzadeh 2010;Dunkel et al 2014;Belay et al 2014). In what follows, several typical planar artificial compound eyes are selected to discuss the design principle.…”

“…Later, inspired by the compound eye of a parasite of wasps called Xenos Peckii, Druart et al came up with the idea to read out the completely partial image within each imaging channel, and then an imaging pre-processing method is used to form a full high resolution image (Druart et al 2008). Brückner et al followed this idea and presented an artificial compound eye system called eCley (Electronic Cluster Eye) (Brückner et al 2010a, b;Bräuer et al 2011;Brückner et al 2011). eCley has an overall thickness only 1.4 mm, but it achieves a VGA resolution with 700 × 550 pixels.…”

Field curvature correction in multichannel miniature imaging systems suited for wafer-level production

“…The size of the different fields and the number of channels were selected from the quality of the areal image. In contrast to existing realizations, 11,17 the field curvature was corrected by the axial position of the channel optics. The result is the design of a multichannel system having only a few channels.…”

“…However, the angular resolution of these systems is limited and superresolution techniques, such as the thin observation module by bound optics method, 5 are required. [10][11][12] Multichannel systems offer many design possibilities, each obtained by weighting differently the numerous design constraints. In our work, 13 we aim at a system with two main properties: the optics has to be simple for easy fabrication using wafer-level mass production [14][15][16] and its size has to be adequate to potentially achieve good angular resolution without resorting to superresolution techniques.…”

“…1 Novel approaches include the use of the wavefront coding method to simplify the lens systems 2,3 and multichannel objectives. [4][5][6][7][8][9][10][11] For fabrication and integration advantages, the multichannel objectives are made very thin using small optical channels. However, the angular resolution of these systems is limited and superresolution techniques, such as the thin observation module by bound optics method, 5 are required.…”