New! Sign up for our free email newsletter.
Science News
from research organizations

Innovations in depth from focus/defocus pave the way to more capable computer vision systems

A new depth from focus/defocus approach combines model-based and learning-based strategies to achieve notable improvements in performance and applicability

Date:
February 9, 2024
Source:
Nara Institute of Science and Technology
Summary:
In an image, estimating the distance between objects and the camera by using the blur in the images as clue, also known as depth from focus/defocus, is essential in computer vision. However, model-based methods fail when texture-less surfaces are present, and learning-based methods require the same camera settings during training and testing. Now, researchers have come up with an innovative strategy for depth estimation that combines the best of both the worlds to solve these limitations, extending the applicability of depth from focus/defocus.
Share:
FULL STORY

In several applications of computer vision, such as augmented reality and self-driving cars, estimating the distance between objects and the camera is an essential task. Depth from focus/defocus is one of the techniques that achieves such a process using the blur in the images as a clue. Depth from focus/defocus usually requires a stack of images of the same scene taken with different focus distances, a technique known as focal stack.

Over the past decade or so, scientists have proposed many different methods for depth from focus/defocus, most of which can be divided into two categories. The first category includes model-based methods, which use mathematical and optics models to estimate scene depth based on sharpness or blur. The main problem with such methods, however, is that they fail for texture-less surfaces which look virtually the same across the entire focal stack.

The second category includes learning-based methods, which can be trained to perform depth from focus/defocus efficiently, even for texture-less surfaces. However, these approaches fail if the camera settings used for an input focal stack are different from those used in the training dataset.

Overcoming these limitations now, a team of researchers from Japan has come up with an innovative method for depth from focus/defocus that simultaneously addresses the abovementioned issues. Their study, published in the International Journal of Computer Vision, was led by Yasuhiro Mukaigawa and Yuki Fujimura from Nara Institute of Science and Technology (NAIST), Japan.

The proposed technique, dubbed deep depth from focal stack (DDFS), combines model-based depth estimation with a learning framework to get the best of both the worlds. Inspired by a strategy used in stereo vision, DDFS involves establishing a 'cost volume' based on the input focal stack, the camera settings, and a lens defocus model. Simply put, the cost volume represents a set of depth hypotheses -- potential depth values for each pixel -- and an associated cost value calculated on the basis of consistency between images in the focal stack. "The cost volume imposes a constraint between the defocus images and scene depth, serving as an intermediate representation that enables depth estimation with different camera settings at training and test times," explains Mukaigawa.

The DDFS method also employs an encoder-decoder network, a commonly used machine learning architecture. This network estimates the scene depth progressively in a coarse-to-fine fashion, using 'cost aggregation' at each stage for learning localized structures in the images adaptively.

The researchers compared the performance of DDFS with that of other state-of-the-art depth from focus/defocus methods. Notably, the proposed approach outperformed most methods in various metrics for several image datasets. Additional experiments on focal stacks captured with the research team's camera further proved the potential of DDFS, making it useful even with only a few input images in the input stacks, unlike other techniques.

Overall, DDFS could serve as a promising approach for applications where depth estimation is required, including robotics, autonomous vehicles, 3D image reconstruction, virtual and augmented reality, and surveillance. "Our method with camera-setting invariance can help extend the applicability of learning-based depth estimation techniques," concludes Mukaigawa.

Here's hoping that this study paves the way to more capable computer vision systems.


Story Source:

Materials provided by Nara Institute of Science and Technology. Note: Content may be edited for style and length.


Journal Reference:

  1. Yuki Fujimura, Masaaki Iiyama, Takuya Funatomi, Yasuhiro Mukaigawa. Deep Depth from Focal Stack with Defocus Model for Camera-Setting Invariance. International Journal of Computer Vision, 2023; DOI: 10.1007/s11263-023-01964-x

Cite This Page:

Nara Institute of Science and Technology. "Innovations in depth from focus/defocus pave the way to more capable computer vision systems." ScienceDaily. ScienceDaily, 9 February 2024. <www.sciencedaily.com/releases/2024/02/240209134440.htm>.
Nara Institute of Science and Technology. (2024, February 9). Innovations in depth from focus/defocus pave the way to more capable computer vision systems. ScienceDaily. Retrieved April 21, 2024 from www.sciencedaily.com/releases/2024/02/240209134440.htm
Nara Institute of Science and Technology. "Innovations in depth from focus/defocus pave the way to more capable computer vision systems." ScienceDaily. www.sciencedaily.com/releases/2024/02/240209134440.htm (accessed April 21, 2024).

Explore More

from ScienceDaily

RELATED STORIES