Interests of refocused images calibrated in depth with a multi-view camera for control by vision

Riou, Cécile; Colicchio, Bruno; Lauffenburger, Jean-Philippe; Cudel, Christophe

doi:10.1117/12.2264237

Cited by 3 publications

(7 citation statements)

References 8 publications

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“…If we consider other fields of research, light fields have proven to be useful for accurate millimetric measurement for automated visual inspection. In [80] the use of refocused depth calibrated images allows performance of measurements on industrial objects and the authors also show that a pixel metric scale can be estimated at different depths, avoiding the use of other measurement devices. It would be interesting to see if these techniques could be successfully applied for PAD in presence of 3D face masks.…”

Section: Discussionmentioning

confidence: 99%

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Light Fields for Face Analysis

Galdi

Chiesa

Busch

et al. 2019

Sensors

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The term “plenoptic” comes from the Latin words plenus (“full”) + optic. The plenoptic function is the 7-dimensional function representing the intensity of the light observed from every position and direction in 3-dimensional space. Thanks to the plenoptic function it is thus possible to define the direction of every ray in the light-field vector function. Imaging systems are rapidly evolving with the emergence of light-field-capturing devices. Consequently, existing image-processing techniques need to be revisited to match the richer information provided. This article explores the use of light fields for face analysis. This field of research is very recent but already includes several works reporting promising results. Such works deal with the main steps of face analysis and include but are not limited to: face recognition; face presentation attack detection; facial soft-biometrics classification; and facial landmark detection. This article aims to review the state of the art on light fields for face analysis, identifying future challenges and possible applications.

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Section: Discussionmentioning

confidence: 99%

“…Some tasks may require the use of only a small number of views. Some preliminary results obtained in [80,81] lead to reduce the number of views. A custom prototype of light-field camera is obtained by putting a small array of microlenses (e.g., of size 2×2) in front of the imaging sensor.…”

Section: Discussionmentioning

confidence: 99%

Light Fields for Face Analysis

Galdi

Chiesa

Busch

et al. 2019

Sensors

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“…In this section, we demonstrate post-capture refocusing using the method proposed in. 22 In Fig. allows performing numerical refocusing.…”

Section: Methodsmentioning

confidence: 99%

“…In the future, we plan to improve the rendering quality by increasing the resolution. On the other hand, the quality of refocusing using the 4 mini-lens ring with the method by 22 is good. This is an advantage given the fact the 4 mini-lens ring is much cheaper and easy to use since it only requires 2 images at 2 known distances (see 22 for more details).…”

Section: Comparison With a Raytrix Cameramentioning

confidence: 99%

“…Such refocused images calibrated in depth can be used efficiently in industrial visual applications such as highlighting a working plane, detecting measure defects in images, as it is illustrated in. 22 Another advantage is that the distance between the ring and the main lens and the distance between the ring and the image sensor are adjustable, which makes the device adaptable to different sizes and locations of objects in the scene.…”

Section: Related Workmentioning

confidence: 99%

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Light-field image acquisition from a conventional camera: design of a four minilens ring device

et al. 2019

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Since few years, a new type of camera is emerging on the market: a digital camera capable of capturing both the intensity of the light emanating from a scene and the direction of the light rays. This new camera technology called light-field camera uses an array of lenses placed in front of a single image sensor, or simply, an array of cameras attached together. In this paper, a new optical device is proposed: a 4 mini-lens ring which is inserted between the lens and the image sensor of a digital camera. This device prototype is able to convert a regular digital camera into a light-field camera as it makes it possible to record 4 sub-aperture images of the scene. It is a compact and cost-effective solution to perform both post-capture refocusing and depth estimation. The mini-lens ring makes also the plenoptic camera versatile; it is possible to adjust the parameters of the ring so as to reduce or increase the size of the projected image. Together with the proof of concept of this new device, we propose a method to estimate the positions of each optical component depending on the observed scene (object size and distance) and the optics parameters. Real-world results are presented to validate our device prototype.

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Interest of polarimetric refocused images calibrated in depth for control by vision

Gendre

Bazeille

Bigué

et al. 2018

Unconventional Optical Imaging

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This work shows the interest of combining polarimetric and light-field imaging. Polarimetric imaging is known for its capabilities to highlight and reveal contrasts or surfaces that are not visible in standard intensity images. This imaging mode requires to capture multiple images with a set of different polarimetric filters. The images can either be captured by a temporal or spatial multiplexing, depending on the polarimeter model used. On the other hand, light-field imaging, which is categorized in the field of computational imaging, is also based on a combination of images that allows to extract 3D information about the scene. In this case, images are either acquired with a camera array, or with a multi-view camera such as a plenoptic camera. One of the major interests of a light-field camera is its capability to produce different kind of images, such as sub-aperture images used to compute depth images, full focus images or images refocused at a specific distance used to detect defects for instance. In this paper, we show that refocused images of a light-field camera can also be computed in the context of polarimetric imaging. The 3D information contained in the refocused images can be combined with the linear degree of polarization and can be obtained with an unique device in one acquisition. An example illustrates how these two coupled imaging modes are promising, especially for the industrial control and inspection by vision.

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Interests of refocused images calibrated in depth with a multi-view camera for control by vision

Cited by 3 publications

References 8 publications

Light Fields for Face Analysis

Light Fields for Face Analysis

Light-field image acquisition from a conventional camera: design of a four minilens ring device

Interest of polarimetric refocused images calibrated in depth for control by vision

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