Research ArticleAPPLIED OPTICS

3D-printed eagle eye: Compound microlens system for foveated imaging

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Science Advances  15 Feb 2017:
Vol. 3, no. 2, e1602655
DOI: 10.1126/sciadv.1602655

Figures

  • Fig. 1 Working principle of the 3D-printed foveated imaging system.

    (A) System of four different compound lenses on the same CMOS image sensor, combining different FOVs in one single system. The lenses exhibit equivalent focal lengths for a 35-mm film from f = 31, 38, 60, and 123 mm. (B) Exemplary fusion of the pixelized object space content to create the foveated image. (C) SEM image of a 3D-printed doublet lens. The individual free-form surfaces with higher-order aspherical corrections are clearly visible. (D) Light microscope image of the 60° FOV compound lens.

  • Fig. 2 3D-printed four-lens systems on the chip.

    (A) CMOS image sensor with compound lenses directly printed onto the chip. The change in color on the sensor surface results from scratching off functional layers, such as the lenslet array and the color filters. (B) Detail of one lens group with four different FOVs for foveated imaging forming one camera. The combined footprint is less than 300 μm × 300 μm.

  • Fig. 3 Design and measurement of normalized MTF contrast in object space as a function of angular resolution.

    The data do not include the transfer function of the CMOS image sensor and are obtained by knife edge MTF measurements of the samples printed on a glass slide. The dashed vertical lines indicate the cutoff spatial frequency of the pixel response function above which the imaging resolution is strongly suppressed. The dashed horizontal line marks the 10% contrast limit, which was used as the criterion for resolvability in this work.

  • Fig. 4 Comparison of simulation and measurement for the foveated imaging systems.

    (A) Imaging through a single compound lens with a 70° FOV. (B) Foveated images for four different lenses with FOVs of 20°, 40°, 60°, and 70°. The measurement for (A) and (B) was carried out on a glass substrate. (C) Same as (A) but simulated and measured on the CMOS image sensor with a pixel size of 1.4 μm × 1.4 μm. (D) Foveated results from the CMOS image sensor. Comparison of the 70° FOV image with its foveated equivalents after 3D-printing on the chip. (E) Measured comparison of the test picture “Lena.” (F) Measured imaging performance for a Siemens star test target. (G) Simulated image for a single-lens reference with an image footprint comparable to the foveated system. (H and I) Geometry of reference lens and foveated system at the same scale.

  • Fig. 5 Development cycle of different lens systems.

    FOVs varying between 20° and 70°. The process chain can be separated into optical design, mechanical design, 3D printing, and measurement of the imaging performance using a USAF 1951 test target (top to bottom).

Tables

  • Table 1 Selected parameters of the designed lens systems.
    Lens 1Lens 2Lens 3Lens 4
    FOV (°)70604020
    Visible object diameter at a distance
    of 1 m (m)
    2.751.730.840.36
    Focal length (μm)64.678.3123.9252.2
    f Number0.70.81.22.6
    Hyperfocal distance (mm)6.47.28.17.3
    Fresnel number at λ = 550 nm705836.718
    35-mm Equivalent focal length (mm)313860123