Cellular multipoint adaptive technology for two-photon mesoscope

Wide field of view (FOV) and high resolution are two desirable properties in many vision-based applications such as tele-conferencing, surveillance, and robot navigation. In some applications, such as 3D reconstruction and rendering, it is also desired that all viewing directions share a single viewpoint, the entire FOV be imaged simultaneously, in real-time, and the depth of field be large. In this paper, we review such a panoramic camera proposed by Nalwa in 1996 that uses reflections off planar mirrors to achieve the first four of the aforementioned capabilities He uses a single mirror pyramid (SMP) and a number of cameras that point to the individual pyramid faces. Together the cameras yield a visual field having a width of 360 degrees and a height same as that of the individual cameras. We propose a double mirror-pyramid (DALP) design that still achieves a 360-degree FOV horizontally but doubles the vertical FOV. It retains the other three capabilities namely high resolution, a single apparent viewpoint across the entire FOV, and real-time panoramic capture. We specify the visual field mapping from the scene to the sensor realized by, the proposed camera. Finally, an implementation of the proposed DMP design is described and examples of preliminary panoramic images obtained are included.

Currently, there are four major medical imaging technologies in the clinic: X-ray computer tomography (X-CT), ultrasound scan imaging (US), positron emission tomography (PET), and magnetic resonance imaging (MRI). They have developed rapidly, but they all have their own disadvantages. Compared with the above four imaging methods, the photoacoustic imaging (PAI) technology based on the photoacoustic effect has been extensively researched. PAI combines the high-contrast advantages of pure optical imaging and the high resolution of pure ultrasound imaging, which can achieve deeper imaging of biological tissues, and is currently widely used in biological imaging. The research in this paper is the expansion of the depth of field of the PAI system. The basic principle of PAI is to irradiate the target tissue with a short pulse laser, to excite ultrasound. The light absorption distribution reflecting the internal structure of the target tissue is reconstructed from the sampled sound waves. Since it needs to focus the laser strongly, this will result in a small imaging depth of field. Many biological tissues (such as brain, abdomen, etc.) have curved surfaces. Due to the limited depth of field of the optical imaging system, the blood vessels in the imaging field of view may not be on the same focal plane. It is arduous to get all accurately focused blood vessel images. It is not conducive to the observation of changes in the structure and composition of blood vessels, which brings great inconvenience to related researchers. In order to solve this problem, this paper proposes a large depth of field and high-resolution three-dimensional photoacoustic information fusion technology suitable for PAI systems. In this paper, the virtual blood vessel data sets are used to simulate the three-dimensional data sets of blood vessels at different focal positions collected by the PAI system. Based on the visualization software Amira, the two sets of three-dimensional data are reconstructed and fused. The results demonstrate that the fused virtual blood vessel imaging structure shows a complete high-resolution structure in the entire field of view. The validity and reliability of the method are verified.

A pupil modulator is a useful tool to improve the resolution of an optical imaging system beyond the classical diffraction limit. However, when this technology is used in a large-aperture telescopic imaging system, the field of view (FOV) with good superresolution (SR) imaging quality is significantly smaller than the designed FOV of the baseline optical system. In this paper, we investigate the influence of various aberrations on the SR properties of a telescopic system using a low sidelobe five-ring pure phase pupil modulator. On this basis, we propose an optimal design method for a wide FOV and a large-aperture telescopic baseline optical system with uniform image quality and a particular residue of symmetric aberration. The design results show that when the optimized 4 m aperture baseline optical system and the modulator are combined as the imaging system, the imaging system has a round and very similar point spread function in the FOV range of 0.28°; the SR gain ratio is 1.234-1.254; and the highest sidelobe intensity is less than 0.1; thus, the system maintains a high resolution ratio and a low sidelobe energy throughout the entire FOV. Finally, a reasonable tolerance model of the baseline optical system is established. The central symmetry tolerances are observed to be loose in this model, thereby reducing the cost and manufacturing difficulty of the system.

Multiple guide stars optimization in conjugate adaptive optics for deep tissue imaging

Studies investigating the spectral reflectance of coral reef benthos and substrates have focused on the measurement of pure endmembers, where the entire field of view (FOV) of a spectrometer is focused on a single benthos or substrate type. At the spatial scales of the current satellite sensors, the heterogeneity of coral reefs even at a sub-metre scale means that many individual image pixels will be made up of a mixture of benthos and substrate types. If pure endmember spectra are used as training data for image classification, there is a spatial discrepancy, because many pixels will have a mixed endmember spectral reflectance signature. This study investigated the spectral reflectance of coral reef benthos and substrates at a spatial scale directly linked to the pixel size of high spatial resolution imaging systems, by incorporating multiple benthos and substrate types into the spectrometer FOV in situ. A total of 334 spectral reflectance signatures were measured of 19 assemblages of the coral reef benthos and substrate types. The spectra were analysed for separability using first derivative values, and a discrimination decision tree was designed to identify the assemblages. Using the decision tree, it was possible to identify 15 assemblages with a mean overall classification accuracy of 62.6%.

Luminance parameter thresholds for user visual comfort under daylight conditions from subjective responses and physiological measurements in a gymnasium

Field-of-view (FOV) and resolution are two critical performance metrics of a near-to-eye display (NED) and are primarily limited by the refractive index (RI) of the waveguide combiner and the number of available pixel counts of the micro display. A high RI material (n = 2.0) is required to transfer an image exceeding a 60 degree full FOV using traditional techniques. We decouple FOV from resolution by wavelength-multiplexing multiple high-resolution FOVs followed by de-multiplexing those FOVs by volume holographic gratings. This approach increases the entire effective FOV beyond the RI-limited FOV while maintaining resolution. Using our new approach we experimentally demonstrate the transfer of images across a 60 degree full FOV through a waveguide with a RI-limited FOV of 30 degrees, which is a common limit for n = 1.5 material. Additional polarization multiplexing enables transferring a 90 degree FOV image over the n = 1.5 waveguide combiner.

The Earth 2.0 (ET) mission is a Chinese next-generation space mission aiming at detecting thousands of terrestrial-like planets, including habitable Earth-like planets orbiting solar type stars (i.e., Earth’s 2.0s), cold low-mass planets, and free-floating planets. The ET mission will use six 300 mm diameter wide field telescope arrays to continuously monitor 1.2 million FGKM dwarf stars in the original Kepler field and its adjacent regions for four consecutive years to search for new planets including Earth 2.0s using the transit technique. The six telescopes have the same configuration, point to the same sky area, and constitute the main scientific payload. Each telescope has an effective aperture of 300 mm with a very wide field of view (FOV) of 500 square degrees and a wavelength coverage of 450-900 nm. Each telescope is equipped with a focal plane mosaic camera. The mosaic camera is composed of 2×2, 9k×9k CMOS detectors with pixel size of 10μm. The optical design results in the diameter of the 90% encircled energy (EE90%) less than 40μm (or 4 pixels) over the entire FOV. About 20% vignetting at the edge of the FOV is introduced to provide good throughput for the entire FOV while keeping optics size and weight down to reduce manufacturing risk and scientific payload within the mass and volume limit. In this paper, we will present the optical design details, including influence analysis of various factors on image quality, e.g., glass material, detector flatness, manufacturing and assembly tolerances. In addition, we will describe temperature stability analysis of the telescope on image quality and photometry measurements.

Augmented reality (AR) displays are pivotal for delivering immersive experiences in the metaverse, thus driving significant research interest. Current AR systems, predominantly relying on diffraction principles, often suffer from low efficiency and face challenges in realizing monolithic full-color operation. Herein, we propose an AR system that integrates a broadband and highly efficient meta-grating in-coupler and an elliptical meta-grating out-coupler onto a single thin glass substrate. The meta-gratings, with unique nanostructures, enable coupling efficiency exceeding 60% for red (R), green (G), and blue (B) wavelengths across the entire field of view (FOV). Image-bearing light is first coupled into a single-layer optical waveguide via the meta-grating, then undergoes two-dimensional expansion through the elliptical meta-grating, and is ultimately coupled into the human eye to form a large AR FOV. Experimentally, we fabricated an optical waveguide prototype and validated the system’s high efficiency and color-enhanced imaging capabilities. This work advances the development of monolithic, trichromatic, highly efficient, and large FOV AR displays based on meta-grating technology.

Photoacoustic microscopy (PAM) systems often face challenges in simultaneously achieving high speed, high resolution, high sensitivity, and a large field of view (FOV). To address this challenge, we have developed dual-channel PAM (DC-PAM) that can expand the FOV without compromising the imaging speed, detection sensitivity, or spatial resolution. DC-PAM has two identical, independent channels of laser excitation and acoustic detection. It exploits two facets of a single hexagon scanner to concurrently steer the dual excitation laser beams and the resultant acoustic waves. DC-PAM achieves an ultra-wide FOV of 22.5 × 24 mm² with a total functional imaging time of ~15 s. Proof-of-concept experiments were conducted using DC-PAM on freely-swimming zebrafish, hypoxia-challenged mice, and sleeping glassfrogs, all of which benefit from the large FOV and high imaging speed to track the dynamic and physiological processes at the whole-organ or whole-body level. These applications demonstrate the potential of DC-PAM for a wide range of biological studies.

A novel angle measuring principle, the optical vernier measuring principle, is presented in this paper based on which a high-accuracy digital sun sensor technology is developed. The design, the performance and the test of the digital sun sensor are described. Test results show that the accuracy of the digital sun sensor is better than 0.02° (about 1 min of arc) in the entire FOV (field of view) of ±64°. Compared with other sun sensors, the major advantage of this sun sensor is that high accuracy and large FOV can be realized with a photoelectric detector with fewer pixels.

This paper presents the design and fabrication of a fiber-based snapshot imaging spectrometer working in both visible (490 nm-732 nm) and short-wave infrared (1090 nm - 1310 nm) ranges. To maximize the light collection efficiency, a custom relay system with 0.25 NA and 20 mm field of view (FOV) was designed and integrated. The bench setup showed that the custom relay system could fully resolve 10 µm fiber cores over the entire FOV among visible and short-wave infrared ranges. The numerical aperture (NA) match provided a 2.07X fold throughout improvement in the visible range and about 10X fold in the SWIR range compared to the previous generations, enabling imaging with a fast frame rate and under low illumination conditions. The presented imaging spectrometer generated spectral datacubes with 35000 spatial samplings and 23 spectral channels. Spectral urban imaging results obtained by the spectrometer in both visible and SWIR ranges are presented. Finally, we collected spectral images of apple bruising to show potential applications in the food quality industry.

Recent literature has seen a number of efforts in respiratory motion correction of PET imaging by considering motion as part of the system model. This type of method however relies on a motion map derived from images (4D PET or 4D CT) of the entire field of view (FOV). In this study we present a region of interest (ROI) based extension to this approach, whereby only the motion map of a user-defined ROI is required and the incorporation of motion into the system model is solely performed within the ROI. A physical phantom study and an NCAT phantom based computer simulation study were performed to test the feasibility of this method. The physical phantom study showed that the proposed ROI based approach had comparable performance within the ROI when comparing with the full image based approach using the same, accurate motion information. The NCAT phantom based study further testified that motion of image features of interest can be estimated more efficiently and potentially more accurately using the ROI based approach.

Recent advances in positron emission tomography (PET) have allowed to perform brain scans of freely moving animals by using rigid motion correction. One of the current challenges in these scans is that, due to the PET scanner spatially variant point spread function (SVPSF), motion corrected images have a motion dependent blurring since animals can move throughout the entire field of view (FOV). We developed a method to calculate the image-based resolution kernels of the motion dependent and spatially variant PSF (MD-SVPSF) to correct the loss of spatial resolution in motion corrected reconstructions. The resolution kernels are calculated for each voxel by sampling and averaging the SVPSF at all positions in the scanner FOV where the moving object was measured. In resolution phantom scans, the use of the MD-SVPSF resolution model improved the spatial resolution in motion corrected reconstructions and corrected the image deformation caused by the parallax effect consistently for all motion patterns, outperforming the use of a motion independent SVPSF or Gaussian kernels. Compared to motion correction in which the SVPSF is applied independently for every pose, our method performed similarly, but with more than two orders of magnitude faster computation time. Importantly, in scans of freely moving mice, brain regional quantification in motion-free and motion corrected images was better correlated when using the MD-SVPSF in comparison with motion independent SVPSF and a Gaussian kernel. The method developed here allows to obtain consistent spatial resolution and quantification in motion corrected images, independently of the motion pattern of the subject.

This paper presents the optical design and experimental demonstration of a compact, foveated, wide field-of-view (FOV) imaging system using two lenses and a liquid crystal spatial light modulator (SLM). The FOV of this simple doublet system is dramatically improved by the SLM, which can be programmed to correct all the geometrical aberrations at any particular field angle. The SLM creates a variation in the image quality across the entire FOV, with a diffraction-limited performance at the field angle of interest (similar to the foveated human vision). The region of interest can be changed dynamically, such that any area within the FOV of the system can be highly resolved within milliseconds. The wide FOV, compactness, and absence of moving parts make this system a good candidate for tracking and surveillance applications. We designed an f/7.7 system, with a 60° full FOV, and a 27 mm effective focal length. Only two lenses and a beam splitter cube were used along with a reflective SLM. The theoretical wavefront aberration coefficients were used to program the SLM, which was placed in the pupil plane of the system. A prototype was built and the system was experimentally demonstrated using monochromatic light and a CCD camera.