Depth from spectrally-varying blurring detected by a snapshot narrow band multispectral imaging sensor

• Main Authors: Wei Jiang, Dingrong Yi, Linghua Kong
• Format: Article
• Language: English
• Published: Wiley 2019-10-01
• Series: The Journal of Engineering
• Subjects: optical images; image restoration; cameras; focal planes; image colour analysis; infrared imaging; aberrations; optical filters; image resolution; image sensors; lenses; commercial colour camera; depth measurement accuracy; cross-talk; narrow-band spectral images; snapshot multispectral imaging sensor; visible longitudinal chromatic aberration; snapshot narrow-band msi sensor; spectrally-varying-focal-depth; different narrow bands; apparently different planes; spectrally-varying depth; snm-msi sensor; depth ambiguity; focal plane; blurred image; cross talks; different spectral channels; focused spectral band shifts; increasing depth; longitudinal chromatic aberration optical lens; snapshot narrow band multispectral imaging sensor; estimating depth; spectrally-varying-amount-of-defocus; single image
• Online Access: https://digital-library.theiet.org/content/journals/10.1049/joe.2018.9062

There exists few reports in the literature aimed at estimating depth from the spectrally-varying-amount-of-defocus contained in a single image generally captured by a commercial colour camera. However, the colour camera can adversely affect the depth measurement accuracy, due to the cross-talk between its wide and overlapping red/green/blue channels. In this study, the authors propose an improved method to estimate depth from non-overlapping and narrow-band spectral images captured by a snapshot narrow-band multispectral imaging (SNB-MSI) sensor. An optical lens with visible longitudinal chromatic aberration is placed in front of the SNB-MSI sensor to enlarge the spectrally-varying-focal-depth so that spectral images corresponding to different narrow bands are focused on apparently different planes. This setting not only differentiates depth ambiguity on both sides of the focal plane, that is caused by two different depths lead to the same blurred image, but also prevents cross talks between different spectral channels. Preliminary experimental data show that the central wavelength of best focused spectral band shifts with increasing depth of the target. This suggests that it is feasible to dynamically measure the depth of the scene using the combination of a longitudinal chromatic aberration optical lens with a SNB-MSI sensor.