fov是什么

Quarter Waveplate The thickness of the quarter waveplate is such that the phase difference is 1/4 wavelength (true-zero order) or some multiple of 1/4 wavelength (multiple order). If the angle θ (between the electric field vector of the incident linearly polarized beam and the retarder principal plane) of the quarter waveplate is 45o, the emergent beam is circularly polarized. When a quarter waveplate is double passed, i.e. by mirror reflection, it acts as a half waveplate and rotates the plane of polarization to a certain angle. Quarter waveplates are used in creating circular polarization from linear or linear polarization from circular, ellipsometry, optical pumping, suppressing unwanted reflection and optical isolation.

There exist several methods for the measurement of lens focal length. Some of the methods for the measurement of lens focal length are listed as following:

Focal length

Half Waveplate The thickness of a half waveplate is such that the phase difference is 1/2-wavelength (true-zero order) or some multiple of 1/2-wavelength (multiple order). A linearly polarized beam incident on a half waveplate emerges as a linearly polarized beam but rotates such that its angle to the optical axis is twice that of the incident beam. Therefore, half waveplates can be used as continuously adjustable polarization rotators. Half waveplates are used in rotating the plane of polarization, electro-optic modulation and as a variable ratio beamsplitter when used in conjunction with a polarization cube.

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Calculatefocal lengthfromFOV

fov和焦距的关系

Focal length and angle-of-view have an inverse relationship. This means that a longer focal length results in a narrower angle-of-view while a shorter focal length leads to a wider angle-of-view.-For example, a 50mm camera lens has a standard field-of-view which is similar to human eye. A 24mm wide-angle lens captures more of the scene compared to what human eyes can capture. Conversely, a 200mm lens will have a narrow field-of-view and capture a smaller portion of the scene when compared with human eyes.

The characteristics of a camera lens have a critical impact on the performance of an embedded vision system. The quality and field-of-view of an image largely depend on the lens in an embedded vision application. Important factors to be considered during the selection of a camera lens for an embedded vision application include:

FOVcalculator

FOVtofocal lengthcalculator

The distance between a lens and the convergence point of light rays on a camera sensor/film is known as the focal length of that particular lens. Focal length is commonly measured in millimeters.

Image perspective depends on a number of factors including lens’ focal length. Generally speaking, shorter focal lengths result in images where objects appear further apart and smaller in size due to a wider viewing angle. Similarly, longer focal lengths result in images where objects appear closer together and larger in size due to a narrower viewing angle.

35mm equivalentfocal length

fov参数

The relative positioning of objects within an image when viewed from a certain angle is referred to as image perspective. Image perspective depends on the relative positions of objects in the image as well as the position of the observer.

Selection of an appropriate camera lens is of paramount importance in image processing, computer vision, and embedded vision systems. The resolution, sharpness, contrast, and FOV of an image largely depend on the camera lens. One of the most important properties of any camera lens is its focal length. In this article we explain the concept of focal length in detail and will help you in choosing the right lens for your camera system.

Focal length and subject size have a direct relationship. A lens with a shorter focal length will have a wider field-of-view which will lead to smaller subject sizes in the image frame. Similarly, a lens with a longer focal length will have a narrower field-of-view which will lead to larger subject sizes in the image frame. Due to this reason, subjects appear smaller in the images captured using wide-angle camera lens. Conversely, subjects appear larger in the images taken using narrow-angle camera lens.

Selection of appropriate focal length for a camera lens is crucial for the overall performance of an embedded vision system. Focal length affects multiple factors such as magnification, field-of-view, subject size, and image perspective. In this article, we have discussed lens focal length in detail and have provided useful information to the readers for the selection of appropriate focal length for an embedded vision application.

The magnification of an image largely depends on the focal length of the lens. Magnification is defined as the apparent size of an object in an image compared to the actual physical size of the object.Focal length and magnification have a direct relationship. Hence, a lens with a smaller focal length will result in smaller apparent size of objects in the image. Similarly, a lens with a greater focal length will result in larger apparent size of objects in the image. In conclusion, the lens’ focal length is directly proportional to the image magnification.

The angle-of-view refers to the amount of scene being captured by the camera lens and sensor. The angle-of-view can be measured vertically, horizontally, or diagonally. The angle-of-view of an image largely depends on the focal length of the image.

The extent to which a camera device can capture a scene is referred to as field-of-view of FOV. Focal length and FOV have an inverse relationship. This means that a lens with a shorter focal length will result in a wider FOV while a longer focal length will result in a narrower FOV.Lens with shorter focal length converge the light at a higher rate which leads to a wider viewing angle. Similarly, lens with longer focal length converge the light at a lower rate which causes narrow viewing angle. Due to this reason, wide-angle lens has a much greater FOV as compared to a telephoto lens.

Waveplates (retardation plates or phase shifters) are made from materials which exhibit birefringence. The velocities of the extraordinary and ordinary rays through the birefringent materials vary inversely with their refractive indices. The difference in velocities gives rise to a phase difference when the two beams recombine. In the case of an incident linearly polarized beam this is given by α=2*π*d(ne-no)/λ  (α - phase difference; d - thickness of waveplate; ne, no - refractive indices of extraordinary and ordinary rays respectively; λ-wavelength). At any specific wavelength the phase difference is governed by the thickness of the waveplate.