Image enhancement based on contrast limited adaptive histogram equalization for 3D images of stereoscopic endoscopy

Abstract

Image enhancement is an important function of stereoscopic endoscopy. 3D images of stereoscopic endoscopy usually suffer from various kinds of degradation because of undesired noise, inhomogeneous brightness and poor contrast. In addition, it often contains color mismatch and different luminance between two stereo views. It will lead to many problems applying traditional image enhancement methods for 3D images of stereoscopic endoscopy. In order to solve those problems, we proposed a novel image enhancement algorithm which consists of three steps: adjusting image by contrast limited adaptive histogram equalization method, choosing the reference image and color matching. The experimental results show that the proposed algorithm produces high quality 3D images by improving image contrast, enhancing the details of the image obviously, removing the color cast and improving consistency of two stereo views. Therefore, the proposed method can obtain high quality 3D images under stressful conditions and be easily applied to stereoscopic endoscopy.Index Terms-3D images, stereoscopic endoscopy, image enhancement, contrast limited adaptive histogram equalization, color matching.

Efficient Enhancement of Stereo Endoscopic Images Based on Joint Wavelet Decomposition and Binocular Combination

“…It is worth pointing out that unlike the two-dimensional endoscopic images case, only few research works have been devoted for stereo endoscopic image enhancement [18], [19]. For instance, Hai et al [18] propose to apply contrast limited adaptive histogram equalization (CLAHE) to the left and right views of the SEI.…”

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“…The threshold will crop the peak value on the homogenous area, and the equalization is obtained from the cumulative value with the less gradient. The cumulative histogram will generate a contrast image and reduce the noise [15].…”

“…• Homogeneity is the measurement of image uniformity based on the greyness. The bigger value shows that the image is homogeneous, which can be calculated by equation (15).…”

Endoscopic image luminance enhancement based on the inverse square law for illuminance and retinex

“…In addition, the high‐dynamic range (HDR) method synthesises an endoscopic outcome with more than one same‐scene image with different exposures, leading to a reduced video frame rate. Histogram equalisation (HE)‐based methods 13,14 can stretch the dynamic range of image luminance to augment details. However, the HE‐based method enhances the contrast in an endoscopic image rather than adjusting the luminance, possibly generating overenhanced or underenhanced results 15 …”