Multiscale guided deblurring: Chromatic aberration correction in color and near-infrared imaging

Abstract

Chromatic aberration, caused by photographic lens imperfections, results in the image of only one spectral channel being sharp, while the other channels are blurred depending on their wavelengths difference with the sharp channel.We study chromatic aberration for a system that jointly records color and near-infrared (NIR) images on a single sensor. Chromatic aberration in such a system leads to a blurred NIR image when the color image is in-focus and sharp. We propose an algorithm that deblurs the NIR image using the gradients of the sharp color image, as both scene representations are generally similar. However, the details of these images often exhibit significant differences due to varying scene reflection and absorption in the corresponding bands. To account for this, we compute the correlation between color and NIR gradients, and use the gradients of the color image in reconstructing NIR only where the gradients are highly correlated. We propose a multiscale scheme that gradually deblurs NIR and accurately computes similarities between color and NIR gradients. Experimental results show that our algorithm recovers details of NIR without producing visible artifacts.

AAM: AN Assessment Metric of Axial Chromatic Aberration

“…The opposite is true if high frequency spectral fusion is desired, (e.g. depth-of-field extension or deblurring), where axial aberration can be leveraged [2,8,9]. We can visually verify in Fig.…”

“…Chromatic aberration has undesirable visual artifacts [4][5][6], and can be a challenge to multispectral applications where spatial matching between channels is important [7]. However, it can also be useful in deblurring for multispectral systems having acquisition channels with shifted focus depth [2,8,9] by transferring high frequencies from one channel to another. Chromatic aberrations are either axial (longitudinal) or lateral (transverse) chromatic aberrations ( Fig.…”

Correlation-based deblurring leveraging multispectral chromatic aberration in color and near-infrared joint acquisition

“…With a simple lens, every wavelength has its own focal distance, causing different magnitudes of blur for different spectral bands. Taken from [17] with authors' permission.…”

“…Out-of-focus NIR images can be deblurred through postprocessing [14][15][16]. In [17], Sadeghipoor et al suggest that the gradients of the luma channel Y (the pixel-wise average of color channels) and of the NIR image representing the same scene are generally similar. Their algorithm matches the gradient of the NIR image iteratively over multiple scales of resolution to the gradient of the Y image, thus deblurring the NIR image using the high-frequency content in Y .…”

“…Our algorithm corrects for the chromatic aberration in the NIR image and extends its depth-of-field. The proposed method improves upon the state-of-the-art technique presented in [17] by separately exploring all color channels and their spectral and spatial correlations to obtain better deblurring, and by increasing the depth-of-field of the deblurred NIR as well. Section 2 presents a study of correlation among different spectral channels.…”