A new focus measure operator for enhancing image focus in 3D shape recovery

Abstract

Measuring the image focus is an important issue in Shape from Focus methods. Conventionally, the Sum of Modified Laplacian, Gray Level Variance (GLV), and Tenengrad techniques have been used frequently among various focus measure operators for estimating the focus levels in a sequence of images. However, they have various issues such as fixed window size and suboptimal focus quality. To solve these problems, a new focus measure operator based on the adaptive sum of weighted modified Laplacian is proposed. First, the adaptive window size selection algorithm based on the GLV is applied. Next, appropriate weights are assigned to the Modified Laplacian values in the image window based on the distance between the center pixel and neighboring pixels. Finally, the Weighted Modified Laplacian values in the image window are summed. Experimental results demonstrate the effectiveness of the proposed method.

3D Measurement Method for Saturated Highlight Characteristics on Surface of Fuel Nozzle

“…Shape from focus (SFF) is a passive, monocular technique used to recover the 3D (three dimensional) shape of an object from sequence images. In SFF, it is important to use the reliable focus measure (FM) operator to obtain the accuracy depth map [ 35 ]. The FM operator evaluates the focus value of every pixel block in the sequence images.…”

Multidirectional focus measure for accurate three‐dimensional shape recovery of microscopic objects

“…Gradient‐based operators compute the focus calculating the first derivative around a pixel based on the assumption that well‐focused image regions have sharper edges than blurred regions (Malik & Choi, 2007; Xie et al, 2007). Laplacian‐based operators measure the focus taking the second derivative around a pixel to respond more sensitively to gradient variations (Jang, Yun, Mutahira, & Muhammad, 2021; Nayar & Nakagawa, 1994). Discrete wavelet transform (DWT)‐based operators take the ratio of energies in high frequency and low frequency components in DWT of an image patch as focus value (Kautsky, Flusser, Zitova, & Šimberová, 2002; Xie et al, 2007).…”