Spectral imaging based on custom-made multi-strip filter arrays.

Spectral imaging technology based on on-chip spectroscopy can find applications in areas including aerospace, industrial and consumer electronics, and so on. Since each application normally requires a different set and number of spectral bands, the development of customized spectroscopy solutions with more compact size and lower cost becomes quite important. In this paper, we demonstrate a compact, highly customizable imaging spectrometer scheme based on custom-made multi-strip filter arrays, which maintains an average high transmission of ∼85%, narrow bandwidth of ∼30n m, and high optical density of ∼O D2 in the blocking regions across the visible to near-infrared waveband. Spectral imaging experiments are conducted, and the accurate reconstruction of sparse spectral image data is demonstrated as well to prove the validity of the proposed scheme. As a result, the work reported in this paper allows researchers to develop customized spectral imaging equipment in a relatively easy way and also has a great potential to be engineered further for scalable production with a quite low cost.

Optimal design of a gravitational wave telescope system for the suppression of stray light.

For gravitational wave detection, the telescope is required to have an ultra-low wavefront error and ultra-high signal-to-noise ratio, where the power of the stray light should be controlled on the order of less than 10-10. In this work, we propose an alternative stray light suppression method for the optical design of an off-axis telescope with four mirrors by carefully considering the optimal optical paths. The method includes three steps. First, in the period of the optical design, the stray light caused by the tertiary mirror and the quaternary mirror is suppressed by increasing the angle formed by the optical axes of the tertiary mirror and the quaternary mirror and reducing the radius of curvature of the quaternary mirror as much as possible to make sure the optical system provides a beam quality with a wavefront error less than λ/80. Next, the stray light could satisfy the requirement of the order of 10-10 when the level of roughness reaches 0.2 nm, and the pollution of mirrors is controlled at the level of CL100. Finally, traditional stray light suppression methods should also be applied to mechanics, including the use of the optical barrier, baffle tube, and black paint. It can be seen that the field stop can efficiently reduce stray light caused by the secondary mirror by more than 55% in the full field of view. The baffle tube mounted on the position of the exit pupil can reduce the overall stray light energy by 5%, and the difference between the ideal absorber (absorption coefficient is 100%) and the actual black paint (absorption coefficient is 90%) is 3.2%. These simulation results are confirmed by the Monte Carlo method for a stray light analysis. Based on the above results, one can conclude that the geometry structure of the optical design, the quality of mirrors, and the light barrier can greatly improve the stray light suppression ability of the optical system, which is vital when developing a gravitational wave telescope with ultra-low stray light energy.

Advanced Biomimetic Multispectral Curved Compound Eye Camera for Aerial Multispectral Imaging in a Large Field of View.

In this work, we demonstrated a new type of biomimetic multispectral curved compound eye camera (BM3C) inspired by insect compound eyes for aerial multispectral imaging in a large field of view. The proposed system exhibits a maximum field of view (FOV) of 120 degrees and seven-waveband multispectral images ranging from visible to near-infrared wavelengths. Pinhole imaging theory and the image registration method from feature detection are used to reconstruct the multispectral 3D data cube. An airborne imaging experiment is performed by assembling the BM3C on an unmanned aerial vehicle (UAV). As a result, radiation intensity curves of several objects are successfully obtained, and a land type classification is performed using the K-means method based on the aerial image as well. The developed BM3C is proven to have the capability for large FOV aerial multispectral imaging and shows great potential applications for distant detecting based on aerial imaging.

Long-working-distance 3D measurement with a bionic curved compound-eye camera.

The bionic curved compound-eye camera is a bionic-inspired multi-aperture camera, which can be designed to have an overlap on the field of view (FOV) in between adjacent ommatidia so that 3D measurement is possible. In this work, we demonstrate the 3D measurement with a working distance of up to 3.2 m by a curved compound-eye camera. In that there are hundreds of ommatidia in the compound-eye camera, traditional calibration boards with a fixed-pitch pattern arrays are not applicable. A batch calibration method based on the CALTag calibration board for the compound-eye camera was designed. Next, the 3D measurement principle was described and a 3D measurement algorithm for the compound-eye camera was developed. Finally, the 3D measurement experiment on objects placed at different distances and directions from the compound-eye camera was performed. The experimental results show that the working range for 3D measurement can cover the whole FOV of 98° and the working distance can be as long as 3.2 m. Moreover, a complete depth map was reconstructed from a raw image captured by the compound-eye camera and demonstrated as well. The 3D measurement capability of the compound-eye camera at long working distance in a large FOV demonstrated in this work has great potential applications in areas such as unmanned aerial vehicle (UAV) obstacle avoidance and robot navigation.

Biomimetic multispectral curved compound eye camera for real-time multispectral imaging in an ultra-large field of view.

In this work, we demonstrate a prototype of a biomimetic multispectral curved compound eye camera (BMCCEC). In comparison with traditional multispectral imaging systems, the BMCCEC developed in this work has the distinct features of multi-spectral imaging on multiple targets in real time in an ultra-large field of view (FOV), which can be attributed to its biomimetic curved compound eye structure as well as the multispectral cluster network. Specifically, the BMCCEC has a total of 104 multispectral ommatidia and a FOV of 98°×98°, which is able to realize 7-band multispectral imaging with center wavelengths of 500 nm, 560 nm, 600 nm, 650 nm, 700 nm, 750 nm and 800 nm and a spectral resolution of 10 nm. A prototype of BMCCEC was then manufactured and multispectral imaging experiments were performed based on it. As a result, the red edge feature of the spectrum of green plants has been successfully obtained and retrieved with a good accuracy.

Depletion of Survivin suppresses docetaxel-induced apoptosis in HeLa cells by facilitating mitotic slippage.

The anticancer effects of taxanes are attributed to the induction of mitotic arrest through activation of the spindle assembly checkpoint. Cell death following extended mitotic arrest is mediated by the intrinsic apoptosis pathway. Accordingly, factors that influence the robustness of mitotic arrest or disrupt the apoptotic machinery confer drug resistance. Survivin is an inhibitor of apoptosis protein. Its overexpression is associated with chemoresistance, and its targeting leads to drug sensitization. However, Survivin also acts specifically in the spindle assembly checkpoint response to taxanes. Hence, the failure of Survivin-depleted cells to arrest in mitosis may lead to taxane resistance. Here we show that Survivin depletion protects HeLa cells against docetaxel-induced apoptosis by facilitating mitotic slippage. However, Survivin depletion does not promote clonogenic survival of tumor cells but increases the level of cellular senescence induced by docetaxel. Moreover, lentiviral overexpression of Survivin does not provide protection against docetaxel or cisplatin treatment, in contrast to the anti-apoptotic Bcl-xL or Bcl-2. Our findings suggest that targeting Survivin may influence the cell response to docetaxel by driving the cells through aberrant mitotic progression, rather than directly sensitizing cells to apoptosis.

Biomimetic curved compound-eye camera with a high resolution for the detection of distant moving objects.

In this Letter, we demonstrate the design and fabrication of a biomimetic curved compound-eye camera (BCCEC) with a high resolution for detecting distant moving objects purpose. In contrast to previously reported compound-eye cameras, our BCCEC has two distinct features. One is that the ommatidia of the compound eye are deployed on a curved surface which makes a large field of view (FOV) possible. The other is that each ommatidium has a relatively large optical entrance and long focal length so that a distant object can be imaged. To overcome the mismatch between the curved focal plane formed by the curved compound eye and the planar focal plane of the CMOS image sensor (CIS), an optical relay subsystem is introduced between the compound eye and the CIS. As a result, a BCCEC with 127 ommatidia in the compound eye is designed and fabricated to achieve a large FOV of up to 98∘×98∘. The experimental results show that objects with a size of 100 mm can be clearly resolved at a distance of 25 m. The capture of the motion trajectories of a moving object is also demonstrated, which makes it possible to detect and track the moving targets in a huge FOV for security surveillance purposes.