Miniature optoelectronic compound eye camera

Abstract

Inspired by insect compound eyes (CEs) that feature unique optical schemes for imaging, there has recently been growing interest in developing optoelectronic CE cameras with comparable size and functions. However, considering the mismatch between the complex 3D configuration of CEs and the planar nature of available imaging sensors, it is currently challenging to reach this end. Here, we report a paradigm in miniature optoelectronic integrated CE camera by manufacturing polymer CEs with 19~160 logarithmic profile ommatidia via femtosecond laser two-photon polymerization. In contrast to μ-CEs with spherical ommatidia that suffer from defocusing problems, the as-obtained μ-CEs with logarithmic ommatidia permit direct integration with a commercial CMOS detector, because the depth-of-field and focus range of all the logarithmic ommatidia are significantly increased. The optoelectronic integrated μ-CE camera enables large field-of-view imaging (90°), spatial position identification and sensitive trajectory monitoring of moving targets. Moreover, the miniature μ-CE camera can be integrated with a microfluidic chip and serves as an on-chip camera for real-time microorganisms monitoring. The insect-scale optoelectronic μ-CE camera provides a practical route for integrating well-developed planar imaging sensors with complex micro-optics elements, holding great promise for cutting-edge applications in endoscopy and robot vision.

Fig. 1. Design and fabrication of the optoelectronic CE camera.

a Photograph of a dragonfly; the insets are the microscopic image of its CE and the schematic diagram of the organism underneath. b Schematic illustration of the defocusing issue in optoelectronic integration; there is a mismatch between the curved image surface and the planar image sensor. c, d Simulated light field of CEs with spherical ommatidia (c) and logarithmic ommatidia (d) via COMSOL Multiphysics simulation software; The incident light of the ommatidium was set as a plane wave. e The schematic diagram for the fabrication of CEs using FL-TPP; the inset is a photograph of an as-prepared μ-CE and the head of a mosquito. f The schematic diagram for the optoelectronic integration; the inset is the photograph of an optoelectronic integrated μ-CE camera.

Fig. 2. Comparisons between spherical and logarithmic CEs.

a, b Optical properties of a a single spherical lens (SL, radius: 25 μm, focal length: 355 μm) and b a logarithmic lens (LL, radius: 25 μm, focusing range: 100–800 μm). The top-left images are microscopic images; the top-right results are cross-sectional profiles; the bottom images are simulative (Sim) and experimental (Exp) focusing intensity distributions along the optical axis. c, d Morphologies of the as-prepared spherical (c) and logarithmic (d) μ-CEs; top images are overall and magnified SEM images, and the bottom results are relative cross-section profiles. e, f Focusing images (top) and normalized intensity distributions along the dotted line (bottom) of spherical (e) and logarithmic (f) μ-CEs. g, h Imaging results of spherical (g) and logarithmic (h) μ-CEs; the insets are magnified images of different ommatidia.

Fig. 3. Measurement of FOV and angular sensitivity function (ASF) of the logarithmic μ-CE.

a Schematic illustration (top) and the focused light field images (bottom) of the logarithmic μ-CE; the incident angles are 0°, 30°, and 45°, respectively. b Comparison of the intensity distributions along the X-axis and Y-axis at normal incidence; the insert is an image of a focal point. c, d Normalized intensity distribution along the X-axis (c) and Y-axis (d) under different incident angles (0°, 30°, and 45°); the wavelength of the continuous light is 633 nm. e The normalized intensity distribution under normal incidence extracted from the focusing image (inset) along the dotted line. f ASF of the logarithmic μ-CE (FWHM = 12.1°).

Fig. 4. The imaging capability of the optoelectronic μ-CE camera.

a Photographs of different targets (top) and the images collected by the μ-CE camera (bottom). b Schematic illustrations of the different spatial positions of a triangle model (top) and relative images captured by the μ-CE camera (bottom). c The true spatial position of the triangle relative to the μ-CE camera. d The calculated spatial position of the triangle according to the images; the side length of the triangular is known (20 mm). The radius of the imaging FOV is 80 mm. e Schematic diagram of the experimental setup for monitoring beetle motion using the μ-CE camera. f Time-lapse photography of a free-crawling beetle at different moments. The photograph is generated by combining five photographs together. The inset is the photograph of the beetle. g Images captured by the μ-CE camera at different times. h The definition statistics of five ommatidia (marked in circles) extracted from the images captured by the μ-CE camera at different times. The definition of ommatidia in different positions reaches the maximum at different moments. i The calculated spatial positions of the beetle at different moments and the as-generated movement trajectory.

Fig. 5. On-chip camera for living microorganisms.

a Schematic diagram of the basic principle for microscopic 3D reconstruction based on a μ-CE camera. b, c Images captured by the μ-CE camera (top) and the 3D reconstruction results of the target objects (a micro-square and a triangle) at two different spatial positions. Dashed and solid lines represent real and reconstructed spatial positions, respectively. d Photograph of the on-chip camera system (left), the μ-CE camera (top-middle), and the SEM image of the logarithmic CE (top-right). The insets are schematic illustrations of its working mechanism (bottom-middle) and the microscopic image of a Paramecium. e The reconstructed 3D trajectory of the Paramecia. f Images of the Paramecium captured by the μ-CE camera (top) and the reconstructed spatial positions (bottom) at different moments. The radius of the imaging FOV is 150 μm.