Abstract

A new optical concept for compact digital image acquisition devices with large field of view is developed and proofed experimentally. Archetypes for the imaging system are compound eyes of small insects and the Gabor-Superlens. A paraxial 3×3 matrix formalism is used to describe the telescope arrangement of three microlens arrays with different pitch to find first order parameters of the imaging system. A 2mm thin imaging system with 21×3 channels, 70°×10° field of view and 4.5mm×0.5mm image size is optimized and analyzed using sequential and non-sequential raytracing and fabricated by microoptics technology. Anamorphic lenses, where the parameters are a function of the considered optical channel, are used to achieve a homogeneous optical performance over the whole field of view. Captured images are presented and compared to simulation results.

© 2005 Optical Society of America

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References

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Appl. Opt. (8)

EOS Topical Meeting (2)

M. Eisner, N. Lindlein, and J. Schwider, �??Making diffraction limited refractive microlenses of spherical and elliptical form,�?? in Microlens Arrays, EOS Topical Meeting Digest Series, M. C. Hutley, ed., 13, (Nat. Phys. Lab., Teddington, 1997) pp. 39�??41.

M. Eisner, S. Haselbeck, H. Schreiber, and J. Schwider, �??Reactive ion etching of microlens arrays into fused silicia,�?? in Microlens Arrays, EOS Topical Meeting Digest Series, M. C. Hutley, ed., 2, (Nat. Phys. Lab., Teddington, 1993) pp. 17�??19.

EOS Topical Meetings (1)

N. Lindlein, S. Haselbeck, and J. Schwider, �??Simplified Theory for Ellipsoidal Melted Microlenses,�?? in Microlens Arrays, EOS Topical Meetings Digest Series, M. C. Hutley, ed., 5, (Nat. Phys. Lab., Teddington, 1995) pp. 7�??10.

J. Opt. A: Pure Appl. Opt. (2)

C. Hembd-Sölner, R. F. Stevens, and M. C. Hutley, �??Imaging properties of the Gabor superlens,�?? J. Opt. A: Pure Appl. Opt. 1, 94�??102 (1999).
[CrossRef]

N. Lindlein, �??Simulation of micro-optical systems including microlens arrays,�?? J. Opt. A: Pure Appl. Opt. 4, 1�??9 (2002).
[CrossRef]

Microelectron. Eng. (1)

R. Völkel, M. Eisner, and K. J. Weible, �??Miniaturized imaging systems,�?? Microelectron. Eng. 67�??68, 461�??472 (2003).
[CrossRef]

Opt. Eng. (1)

R. Völkel, H. P. Herzig, P. Nussbaum, and R. Dändliker, �??Microlens array imaging system for photolithography,�?? Opt. Eng. 35, 3323�??3330 (1996).
[CrossRef]

Proc. EOS/SPIE (1)

R. Völkel, C. Ossmann, T. Scharf, H. P. Herzig, and R. Dändliker, �??Optical microsystems for imaging,�?? in Electronic Image Capture and Publishing, Proc. EOS/SPIE 3410�??03, (1998).

Proc. SPIE (1)

J. Duparré, P. Schreiber, P. Dannberg, T. Scharf, P. Pelli, R. Völkel, H.-P. Herzig, and A. Bräuer, �??Artifical compound eyes�??different concepts and their application to ultra flat image acquisition sensors,�?? in MOEMS and Miniaturized Systems IV, A. El�??Fatatry, ed., Proc. SPIE 5346, 89�??100 (2004).

Progress in Optics (1)

W. Shaomin and L. Ronchi, �??Principles and design of optical arrays,�?? in Progress in Optics, E. Wolf, ed., 25 (North-Holland, Amsterdam, 1988), pp. 279�??347.
[CrossRef]

Pure Appl. Opt. (1)

P. Nussbaum, R. Völkel, H. P. Herzig, M. Eisner, and S. Haselbeck, �??Design, fabrication and testing of microlens arrays for sensors and Microsystems,�?? Pure Appl. Opt. 6, 617�??636 (1997).
[CrossRef]

Other (7)

C. Hofmann, Die Optische Abbildung, 1st ed. (Akademische Verlagsgesellschaft Geest & Portig, Leipzig, 1980).

A. E. Siegmann, Lasers (University Science, Mill Valley, Calif., 1986).

N. Hodgson and H.Weber, Optische Resonatoren (Springer, 1992).
[CrossRef]

R. Völkel and S. Wallstab, �??Flachbauendes Bilderfassungssystem,�?? Offenlegungsschrift DE 199 17 890 A1 (1999).

D. Gabor, �??Improvements in or relating to optical systems composed of lenticules,�?? Patent UK 541 753 (1940).

M. F. Land and D.-E. Nilsson, Animal Eyes, Oxford Animal Biology Series (University, Oxford, 2002).

J. S. Sanders, ed., Selected Papers on Natural and Artificial Compound Eye Sensors, SPIE Milestone Series, 122nd ed. (SPIE Optical Engineering, Bellingham, 1996).

Supplementary Material (2)

» Media 1: AVI (157 KB)     
» Media 2: AVI (158 KB)     

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Figures (15)

Fig. 1.
Fig. 1.

Working principle of compound-eye-type imaging system with optical image reconstruction [16].

Fig. 2.
Fig. 2.

Front view of the multi-aperture imaging system with hexagonal arrangement of channels to form the cluster eye ((a) round lenses in lens array, (b) anamorphic lenses with elliptical lens bases in lens array). (c) Side view of multi-aperture imaging system. Field lens array is partitioned. This arrangement allows for wafer-scale lens manufacturing and wafer-level packaging of the imaging system.

Fig. 3.
Fig. 3.

Scheme of the paraxial optical model of the compound eye for visualization of the used variables.

Fig. 4.
Fig. 4.

Paraxial five-channel example system for demonstration of (a) the image transfer by the cluster eye principle and (b) behavior like a Gabor-Superlens. I: Focussing lens array, II: Field lens array, also position of field aperture array, III: Relay lens array, IV: Image plane. A and C show marginal fields of an individual channel, B represents the center field. D shows the focus for a field of 0°, and E for a field of 20°. In (a) and (b) exactly the same arrangement of lens arrays is presented. The only difference is the angular spectrum applied to the imaging system. For modelling the field apertures of the cluster eye in (a), each channel is assigned to a portion of the overall FOV, the adjacent channel’s FOVs are attached to. In (b) the performance as a Gabor-Superlens becomes visible because no constraints are set for the individual channel’s FOVs but each channel can transfer the full FOV. Exemplarily angles of incidence of 0° and 20° are presented.

Fig. 5.
Fig. 5.

Cluster eye in a rectangular arrangement of toric lenses in a matrix of 21×3 channels. Only channel-columns 0 to 10 are shown due to the y-symmetry of the system. (a) 3D-view of the system showing the increasing ellipticity of the lenses in the first array with increasing field angle. Substrates are hidden. (b) Side view of the system. Three lens arrays are placed on 550µm thick quartz substrates S1, S2, S3 (first array consists of toric lenses). Lenses and apertures are placed on the front side of S1, backside of S2 and front side of S3. For each channel the central field as well as the y-marginal fields are shown. The maximum marginal field of one channel equals the minimum marginal field of the adjacent channel. A perfect annexation of the individual sub-images to one overall image can be noticed because the same field angle transmitted by two adjacent channels delivers one image point. A, C and B indicate the positions of the marginal and the central field, respectively, of the central channel in the image plane.

Fig. 6.
Fig. 6.

Analysis of system presented in Fig. 5, only field angles from -1.8° to 35° are shown due to y-symmetry. (a) Horizontal and vertical sample objects with 1.2 LP/° are imaged by the cluster eye. The resolution of the patterns decreases with increasing y-field angle due to aberrations and image overlap. However, even for large field angles the line patterns can be resolved (b) Spot diagram of the presented system, for each channel a central and 4 marginal field bundles (+x,-x,+y,-y) are traced. Increasing spot size with y-field due to coma as well as very good overlap of marginal fields of adjacent channels can be observed.

Fig. 7.
Fig. 7.

Results of non-sequential raytracing analysis of the cluster eye, (a) signal to noise ratio of maximum intensity in image plane and overall power as a function of angle of incidence. (b) Image of 2°×2° extended source moving through the upper half of FOV of the cluster eye (0°–36°), linear scale. (c) Image of 2°×2° extended source moving through the upper half of FOV of the cluster eye (0°–36°), logarithmic scale. (d) Non-sequentially imaged horizontal bar target (only upper half of FOV shown, due to symmetry). (e) Non-sequentially imaged vertical bar target (only upper half of FOV shown, due to symmetry). [Media 1] [Media 2]

Fig. 8.
Fig. 8.

Scheme of experimentally realized cluster eye. The focussing lens array includes ellipsoidal lenses. The field lens and the relay lens array consist of circular lenses. Chromium apertures are attached to all lens arrays. Rectangular field apertures on the field lenses allow for a spatial annexation of the subimages to one overall image.

Fig. 9.
Fig. 9.

Comparison of ideal and experimentally obtained radii of curvatures of ellipsoidal lenses of the focussing array.

Fig. 10.
Fig. 10.

Image of a white surface. (a), (b) and (c) show the same image produced by the cluster eye but with different axial positions of the relay optics (distance of 120µm with respect to each other).

Fig. 11.
Fig. 11.

Microscope image of field lens array with applied field apertures.

Fig. 12.
Fig. 12.

Images of a radial star test pattern at a distance of 41cm. (Here 5×3 channels are contributing.) (a) At a certain distance from the cluster eye the individual microimages have high contrast but are separated from each other. (b) Moving the image plane 120µm away all the microimages exhibit very good annexation with only minor areas of overlap or lack of annexation. One overall image is generated by transfer of the different image sections through different channels. However, the contrast of the microimages is reduced compared to (a).

Fig. 13.
Fig. 13.

Imaged bar targets. (a) Tilted bar target with a line pair size of 8.8mm and a height of 7cm at a distance of 55cm. Good image annexation can be observed, the edges of the bars are very sharp. (b) Image of a vertical test pattern at a distance of 41cm and size of 13.5cm demonstrating a resolution of the cluster eye of 71LP/mm being equal to 3.3LP/°. (c) The same resolution is achieved imaging a horizontal test pattern.

Fig. 14.
Fig. 14.

(a) Image of a text section of M. F. Land’s book “Animal Eyes”, Section 3: “What makes a good eye” [4] with size 10cm×3.7cm at a distance of 17cm. (b) Image of a picture of “Image processing Lena”. (c) Image of our institutes logo.

Fig. 15.
Fig. 15.

Ground diffusing glass introduced in the image plane of cluster eye. (a) Relay by microscope objective (8×3 channels observed, imaging a section of a radial star pattern). (b) C-mount objective (f=16mm, F/#=1.4, with extension rings) used for relay of image of a radial star pattern formed by the cluster eye. A horizontal FOV of 63° can be observed. 16×3 channels contribute.

Tables (2)

Tables Icon

Table 1. Parameters of example systems presented in raytracing simulations and fabricated by microoptics technology.

Tables Icon

Table 2. Theoretical parameters of lens array layers of cluster eye. Lens heights, full sizes of lens bases, radii of curvatures of lenses and sizes of apertures are given for center channel (0) and for marginal channel (10). Units are µm.

Equations (20)

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( h out α out 1 ) = ( M 11 M 12 Δx M 21 M 22 Δφ 0 0 1 ) · ( h in α in 1 ) .
( 1 0 0 1 f 1 σ f 0 0 1 ) = ( 1 0 σ 0 1 0 0 0 1 ) · ( 1 0 0 1 f 1 0 0 0 1 ) · ( 1 0 σ 0 1 0 0 0 1 )
M = ( M 11 M 12 M 13 M 21 M 22 M 23 0 0 1 ) = ( 1 F 0 0 1 0 0 0 1 ) · ( 1 0 N p 1 0 1 0 0 0 1 ) ·
· ( 1 0 0 1 f 2 1 N f 2 · ( p 1 p 2 ) 0 0 1 ) · ( 1 d f 1 0 0 1 0 0 0 1 ) ·
· ( 1 0 0 1 f f 1 N f f · ( p 1 p f ) 0 0 1 ) · ( 1 f 1 0 0 1 0 0 0 1 ) · ( 1 0 0 1 f 1 1 0 0 0 1 ) .
F = f 1 d f 1 + f 2 d f 2 .
F = d p 1 dp f f 1 p 1 + f 1 p f p 1 f f dp 1 dp f f 1 p 1 + f 1 p f f 2 p 1 + f 2 p f p 1 f f + p 2 f f f 2 .
F = p 1 p 1 p 2 f 2 .
p 1 = γ D α in max
p f = γ D ( 2 α in max f 1 + 2 α in max L + D ) α in max ( 2 α in max L + D )
p 2 = γ D ( 2 α in max F + D ) α in max ( 2 α in max L + D )
f 1 = D ( L F ) 2 α in max F + D
f f = 2 α in max f 1 ( L f 1 ) 2 α in max L + D
f 2 = 2 α in max F ( L F ) ( 2 α in max L + D )
d = L F
α in ind = γ D 2 α in max L + D
N = α in max ( 2 α in max L + D ) γ D
a = γ D 2 α in max ( 2 α in max L + D )
R = h L 2 + r 2 2 h L
R 0 r 2 = R x a x 2 = R y a y 2

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