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Varifocal Lens
A varifocal lens is a camera lens with variable focal length in which focus changes as focal length (and magnification) changes, as compared to a '' parfocal'' ("true") zoom lens, which remains in focus as the lens zooms (focal length and magnification change). Many so-called "zoom" lenses, particularly in the case of fixed-lens cameras, are actually varifocal lenses, which give lens designers more flexibility in optical design trade-offs (focal length range, maximum aperture, size, weight, cost) than parfocal zoom. These are practical because of autofocus, and because the camera processor can automatically adjust the lens to keep it in focus while changing focal length ("zooming") making it suitable for still photography where a change in magnification of the subject, as demonstrated below is not a problem. The change in the subject size is a significant problem in video and true parfocal designs are needed for higher quality video work. Varifocal lenses can be used for image displ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Camera Lens
A camera lens (also known as photographic lens or photographic objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically. There is no major difference in principle between a lens used for a still camera, a video camera, a telescope, a microscope, or other apparatus, but the details of design and construction are different. A lens might be permanently fixed to a camera, or it might be interchangeable with lenses of different focal lengths, apertures, and other properties. While in principle a simple convex lens will suffice, in practice a compound lens made up of a number of optical lens elements is required to correct (as much as possible) the many optical aberrations that arise. Some aberrations will be present in any lens system. It is the job of the lens designer to balance these and produce a desi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focal Length
The focal length of an optical system is a measure of how strongly the system converges or diverges light; it is the inverse of the system's optical power. A positive focal length indicates that a system converges light, while a negative focal length indicates that the system diverges light. A system with a shorter focal length bends the rays more sharply, bringing them to a focus in a shorter distance or diverging them more quickly. For the special case of a thin lens in air, a positive focal length is the distance over which initially collimated (parallel) rays are brought to a focus, or alternatively a negative focal length indicates how far in front of the lens a point source must be located to form a collimated beam. For more general optical systems, the focal length has no intuitive meaning; it is simply the inverse of the system's optical power. In most photography and all telescopy, where the subject is essentially infinitely far away, longer focal length (lower opti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focus (optics)
In geometrical optics, a focus, also called an image point, is a point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the blur circle. This non-ideal focusing may be caused by aberrations of the imaging optics. In the absence of significant aberrations, the smallest possible blur circle is the Airy disc, which is caused by diffraction from the optical system's aperture. Aberrations tend to worsen as the aperture diameter increases, while the Airy circle is smallest for large apertures. An image, or image point or region, is in focus if light from object points is converged almost as much as possible in the image, and out of focus if light is not well converged. The border between these is sometimes defined using a "circle of confusion" criterion. A principal focus or focal point is a special focus: * For a lens, or a spherical or parabolic mirror, it is a point ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnification
Magnification is the process of enlarging the apparent size, not physical size, of something. This enlargement is quantified by a calculated number also called "magnification". When this number is less than one, it refers to a reduction in size, sometimes called ''minification'' or ''de-magnification''. Typically, magnification is related to scaling up visuals or images to be able to see more detail, increasing resolution, using microscope, printing techniques, or digital processing. In all cases, the magnification of the image does not change the perspective of the image. Examples of magnification Some optical instruments provide visual aid by magnifying small or distant subjects. * A magnifying glass, which uses a positive (convex) lens to make things look bigger by allowing the user to hold them closer to their eye. * A telescope, which uses its large objective lens or primary mirror to create an image of a distant object and then allows the user to examine the image clo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parfocal Lens
A parfocal lens is a lens that stays in focus when magnification/ focal length is changed. There is inevitably some amount of focus error, but too small to be considered significant. Microscopy Parfocal microscope objectives stay in focus when magnification is changed; i.e., if the microscope is switched from a lower power objective (e.g., 10×) to a higher power objective (e.g., 40×), the object stays in focus. Most modern bright-field microscopes are parfocal. Photography ''Zoom lenses'' (sometimes referred to as "true" zoom) are ideally ''parfocal'', in that focus is maintained as the lens is zoomed (i.e., focal length and magnification changed), which is convenient and has the advantage of allowing more accurate focusing at maximal focal length then zooming back to a shorter focal length to compose the image. Many zoom lenses, particularly in the case of fixed-lens cameras, are actually '' varifocal lenses'', which gives lens designers more flexibility in optical design t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zoom Lens
A zoom lens is a mechanical assembly of lens elements for which the focal length (and thus angle of view) can be varied, as opposed to a fixed-focal-length (FFL) lens (see prime lens). A true zoom lens, also called a parfocal lens, is one that maintains focus when its focal length changes. Most consumer zoom lenses do not maintain perfect focus, but are still parfocal designs. Most camera phones that are advertised as having optical zoom actually use a few cameras of different but fixed focal length, combined with digital zoom to make a hybrid system. The convenience of variable focal length comes at the cost of complexity – and some compromises on image quality, weight, dimensions, aperture, autofocus performance, and cost. For example, all zoom lenses suffer from at least slight, if not considerable, loss of image resolution at their maximum aperture, especially at the extremes of their focal length range. This effect is evident in the corners of the image, when displa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autofocus
An autofocus (or AF) optical system uses a sensor, a control system and a motor to focus on an automatically or manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication. Autofocus methods are distinguished as active, passive or hybrid types. Autofocus systems rely on one or more sensors to determine correct focus. Some AF systems rely on a single sensor, while others use an array of sensors. Most modern SLR cameras use through-the-lens optical sensors, with a separate sensor array providing light metering, although the latter can be programmed to prioritize its metering to the same area as one or more of the AF sensors. Through-the-lens optical autofocusing is usually speedier and more precise than manual focus with an ordinary viewfinder, although more precise manual focus can be achieved with special accessories such as focusing magnifiers. Autofocus accuracy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oculus VR
Reality Labs is a business of Meta Platforms (formerly Facebook Inc.) that produces virtual reality (VR) and augmented reality (AR) hardware and software, including virtual reality headsets such as Quest, and online platforms such as Horizon Worlds. Reality Labs is the corporate successor to Oculus, a company that was founded in 2012 by Palmer Luckey, Brendan Iribe, Michael Antonov and Nate Mitchell to develop a VR headset for video gaming known as the Oculus Rift. Before the acquisition, Oculus raised over $2.4 million for the project via a crowdfunding campaign on Kickstarter—nearly ten times the original goal of $250,000. Oculus was acquired by Facebook in March 2014. The company partnered with Samsung Electronics to release the Gear VR accessory for Samsung Galaxy smartphones in 2015. In March 2016, Oculus released the first consumer version of the Rift headset. In 2017, the company released a standalone mobile headset known as Oculus Go, produced by Xiaomi. In 2019, i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Reality
Virtual reality (VR) is a simulated experience that employs pose tracking and 3D near-eye displays to give the user an immersive feel of a virtual world. Applications of virtual reality include entertainment (particularly video games), education (such as medical or military training) and business (such as virtual meetings). Other distinct types of VR-style technology include augmented reality and mixed reality, sometimes referred to as extended reality or XR, although definitions are currently changing due to the nascence of the industry. Currently, standard virtual reality systems use either virtual reality headsets or multi-projected environments to generate realistic images, sounds and other sensations that simulate a user's physical presence in a virtual environment. A person using virtual reality equipment is able to look around the artificial world, move around in it, and interact with virtual features or items. The effect is commonly created by VR headsets consisting ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Varifocal Example
A varifocal lens is a camera lens with variable focal length in which focus changes as focal length (and magnification) changes, as compared to a '' parfocal'' ("true") zoom lens, which remains in focus as the lens zooms (focal length and magnification change). Many so-called "zoom" lenses, particularly in the case of fixed-lens cameras, are actually varifocal lenses, which give lens designers more flexibility in optical design trade-offs (focal length range, maximum aperture, size, weight, cost) than parfocal zoom. These are practical because of autofocus, and because the camera processor can automatically adjust the lens to keep it in focus while changing focal length ("zooming") making it suitable for still photography where a change in magnification of the subject, as demonstrated below is not a problem. The change in the subject size is a significant problem in video and true parfocal designs are needed for higher quality video work. Varifocal lenses can be used for image displ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
