Night vision

About: Night vision is a research topic. Over the lifetime, 6004 publications have been published within this topic receiving 67372 citations.

Bat Eyes Have Ultraviolet-Sensitive Cone Photoreceptors

Abstract: Mammalian retinae have rod photoreceptors for night vision and cone photoreceptors for daylight and colour vision. For colour discrimination, most mammals possess two cone populations with two visual pigments (opsins) that have absorption maxima at short wavelengths (blue or ultraviolet light) and long wavelengths (green or red light). Microchiropteran bats, which use echolocation to navigate and forage in complete darkness, have long been considered to have pure rod retinae. Here we use opsin immunohistochemistry to show that two phyllostomid microbats, Glossophaga soricina and Carollia perspicillata, possess a significant population of cones and express two cone opsins, a shortwave-sensitive (S) opsin and a longwave-sensitive (L) opsin. A substantial population of cones expresses S opsin exclusively, whereas the other cones mostly coexpress L and S opsin. S opsin gene analysis suggests ultraviolet (UV, wavelengths <400 nm) sensitivity, and corneal electroretinogram recordings reveal an elevated sensitivity to UV light which is mediated by an S cone visual pigment. Therefore bats have retained the ancestral UV tuning of the S cone pigment. We conclude that bats have the prerequisite for daylight vision, dichromatic colour vision, and UV vision. For bats, the UV-sensitive cones may be advantageous for visual orientation at twilight, predator avoidance, and detection of UV-reflecting flowers for those that feed on nectar.

Perceptual ability with real-world nighttime scenes: image-intensified, infrared, and fused-color imagery.

Abstract: This study investigated human perceptual performance allowed by relatively impoverished information conveyed in nighttime natural scenes. Researchers used images of nighttime outdoor scenes rendered in image-intensified low-light visible (i-squared) sensors, thermal infrared (ir) sensors, and an i-squared/ir fusion technique with information added. They found that nighttime imagery provides adequate low-level image information for effective perceptual organization on a classification task, but that performance for exemplars within a given object category is dependent on the image type. Overall performance was best with the false-color fused images. This is consistent with the suggestion in the literature that color plays a predominate role in perceptual grouping and segmenting of objects in a scene and supports the suggestion that the addition of color in complex achromatic scenes aids the perceptual organization required for visual search. The study addresses the issue of assessment of perceptual performance with alternative night-vision sensors and fusion methods and begins to characterize perceptual organization abilities permitted by the information in relatively impoverished images of complex scenes. Applications of this research include improving night vision, medical, and other devices that use alternative sensors or degraded imagery.

A Day and Night Vision MOS Imager With Robust Photonic-Crystal-Based RGB-and-IR

Abstract: This paper demonstrates a day and night vision MOS imager with red, green, blue (RGB) and extra near-infrared filters placed over individual pixels. The on-chip RGB and IR filters are fabricated from an inorganic photonic crystal color filter (PCCF) technology, thereby realizing a robust and reliable camera module for indoor and outdoor use without mounting a mechanical IR-cut filter. These PCCFs allow the IR band as well as the RGB bands to pass through to the RGB photodiodes from which RGB signals, each involving some amount of IR component, are derived. During the daytime, however, chromatically almost pure RGB colors are reproduced by subtracting a weighed IR signal of an extra IR pixel from the raw RGB signals of the surrounding IR pixels. As a result, the IR components in the resultant RGB signals are minimized from 25%, 21%, and 50% to 9%, 4%, and 21%, respectively. During the night, on the other hand, an IR image having a resolution match with a conventional IR imager can be captured by using the IR components of the raw RGB signals with the IR signal.

Phonon-enhanced photothermoelectric effect in SrTiO 3 ultra-broadband photodetector.

Abstract: The self-powered and ultra-broadband photodetectors based on photothermoelectric (PTE) effect are promising for diverse applications such as sensing, environmental monitoring, night vision and astronomy. The sensitivity of PTE photodetectors is determined by the Seebeck coefficient and the rising temperature under illumination. Previous PTE photodetectors mostly rely on traditional thermoelectric materials with Seebeck coefficients in the range of 100 μV K-1, and array structures with multiple units are usually employed to enhance the photodetection performance. Herein, we demonstrate a reduced SrTiO3 (r-STO) based PTE photodetector with sensitivity up to 1.2 V W-1 and broadband spectral response from 325 nm to 10.67 μm. The high performance of r-STO PTE photodetector is attributed to its intrinsic high Seebeck coefficient and phonon-enhanced photoresponse in the long wavelength infrared region. Our results open up a new avenue towards searching for novel PTE materials beyond traditional thermoelectric materials for low-cost and high-performance photodetector at room temperature.