F number depth of fieldcanon

iii.     Circle of confusion (CoC): this is often corresponding to the pixel size, in the spatial dimension, along the slit, at the slit level (also taking into account the magnification of the system). A camera with large pixels will have large DoF. It also means that spatial binning would increase the DoF. PS: in practice, the (CoC) is limited by the system’s optical resolution but not the detector’s pixel size. Using the pixel size as CoC gives a minimum approximation for the DoF.

In tests, the camera not only produced sharp 3D images but also increased contrast and reduced lens crosstalk. The authors hope to implement this technology in other related applications.

F number depth of fieldphotography

Depth of fieldphotography examples

Before performing any major operation, medical professionals like to get a clear picture of the problem. For dental work, that could mean a 3D image of the mouth captured by a handheld camera. Such an image has the potential to provide a fast, accurate visual representation of the relevant area, but existing technologies come with limitations such as bulky hardware or motion artifacts that limit practical use.

Depth offocus

ii.     The Aperture of the lens, as F-number: a system with a large F-number would have a larger DoF. However, less light would enter the system, which would then be at the expense of the integration time.

Source: “Deep focus light-field camera for handheld 3D intraoral scanning using crosstalk-free solid immersion microlens arrays,” by Jae-Myeong Kwon, Sang-In Bae, Taehan Kim, Jeong Kun Kim, and Ki-Hun Jeong, APL Bioengineering (2023). The article can be accessed at https://doi.org/10.1063/5.0155862 .

Every optical imaging system has a depth of field (DoF). It is defined as the distance between the nearest and the farthest objects in sharp focus. The DoF should be distinct from another optical property, called the Depth of Focus, which refers to the tolerance of placement of the image plane concerning the lens position (Figure 1).

i.     The Working Distance: DoF increases with the measurement distance. Notice that this is at the expense of the spatial sampling of the object.

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Shallowdepth of field

As a 501(c)(3) non-profit, AIP is a federation that advances the success of our Member Societies and an institute that engages in research and analysis to empower positive change in the physical sciences. The mission of AIP (American Institute of Physics) is to advance, promote, and serve the physical sciences for the benefit of humanity.

“The ability of light-field cameras to capture both spatial and directional information in a single exposure, as well as their ability to be easily miniaturized, suggested an innovative method for improving 3D intraoral scanners,” said author Ki-Hun Jeong.

Kwon et al. developed a deep focus light-field camera (DF-LFC) equipped with a solid immersion microlens array (siMLA) capable of producing accurate images with a large depth of field. Their camera, integrated into a 3D intraoral scanner, captured high-resolution images that could be reconstructed into a complete dental model.

Where u represents the working distance (WD), N is the f-number, c is the Circle of Confusion, and f is the focal length. Note that equation (1) does not take into account lens aberrations. In some cases, when the circle of confusion is negligibly small relative to the Aperture (term c² tends to 0), and the working distance is significantly larger than the focal length (𝑢 − 𝑓 ≈ 𝑢), equation (1) can be approximated by [1].

“Based on these achievements, our next steps will involve the optimization of light-field camera design and light-field image processing for advanced 3D imaging systems in clinical endoscopy or robotic surgery,” said Jeong.

Depth of fieldcalculator

F number depth of fieldcalculator

The major downside to LFCs is that the microlens arrays they depend on have shallow depths of field owing to their manufacturing process. In a handheld scanner, this can result in blurry images and motion artifacts. The team overcame this challenge by employing si-MLAs, which are covered with a low-index transparent elastomer.

F number depth of fieldnikon

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All the above shows that high spatial resolution with large DoF can only be achieved at the expense of a high F-number (lower throughput and longer integration time).

An imaging system’s DoF is crucial when measuring non-flat samples. It could be in a laboratory, an industrial system, and remote sensing applications. The DoF can be estimated as follows [1].

iv.     The focal length of the front objective: the DoF decreases while the focal length increases. In practice, a lens with a wider FOV has a larger DoF.