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focus x
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focus
1. The focal point. 2. To adjust the eyepiece or objective of a telescope so that the image is clearly seen by the observer. 3. To adjust the camera lens, plate, or film holder so that the image is...
focus control
1. A mechanism that permits the focusing of an optical system.2. A means of obtaining the sharpest image from a cathode-ray tube display by adjusting the size of the spot where it reaches the screen.
focus lamp
An incandescent or carbon arc lamp designed with a stable and compact arc or filament that permits it to be used as a light source to be focused by a lens system.
focused laser scattering
A single-particle scattering technique in which an incident laser beam is tightly focused by means of lenses to yield a focal spot in the scattering material with a diameter on the order of the...
focusing anode
One of the electrodes used to focus the electron beam of a cathode-ray tube. As the electrode's voltage is changed, its electrical field is changed, resulting in a change of the electron beam's spot...
focusing coil
A coil used to focus an electron beam by the generation of a magnetic field parallel to the beam.
focusing corner cube
A retroreflector that can focus a beam of light, with one planar reflective surface, one spherical and a third that is either planar or convex cylindrical.
focusing scale
A scale on an optical instrument that indicates the condition of focus. May indicate the distance to the object or diopter output, or from infinity focus.
actinic focus
Actinic focus refers to the point or plane within an optical system where ultraviolet (UV) light or other actinic radiation converges to form the sharpest possible image. Here are the key aspects: ...
autofocus system
A means of adjusting the sharpness of an image automatically, with a sensor for estimating distance or contrast and a drive mechanism to adjust the lens. Active systems generate a light source to...
conjugate autofocus system
A system that determines whether an image is in or out of focus by means of a source of illumination at the conjugate focal point, which reflects off the target; the return beam is mediated by masks...
conjugate focus
->
conjugate points
The two points on the principal axis of a mirror or lens so positioned that light emitted from either point will be focused at the other, i.e., object and image points.
Crayford focuser
A high-quality focuser that uses rollers rather than gears and offers smooth, precise motion while reducing or eliminating image shift and backlash.
deflection focusing
The progressive defocusing of a cathode-ray tube display image that occurs when the deflected electron beam impinges on the cathode-ray tube screen at a slant.
depth of focus
The range of image distances that corresponds to the range of object distances covered by the depth of field.
direct screen focusing
In a camera, the focusing of an image on the screen located at the camera's film plane. Once the image is in complete focus, the recording medium is inserted in place of the screen.
double-focusing mass spectrometer
A mass spectrometer utilizing both radial electrostatic and magnetic field analyzers to improve the focusing and increase resolution.
electromagnetic focusing
->
electromagnetic lens
An electron lens consisting of a homogeneous axial electric field and a magnetic field used in high-quality image tubes for high modulation transfer function and small geometrical distortion...
electrostatic focus
The use of an applied electrical field to focus a cathode-ray tube's electron beam.
electrostatically focused image tube
An image intensifier that uses electrostatics to amplify and focus the electronic image.
fixed focus
Describes devices that are not provided with a means of focusing.
fixed-focus mode
->
convergent beam sensing mode
A type of photoelectric proximity mode sensing incorporating a lens system to focus the light from the emitter in a small, concentrated spot at a specific point in front of the sensor. Also referred...
front-cell focusing
A method of focusing an optical system by moving the front component (the lens closest to the subject) to change the distances between components. Also known as front-element focusing.
gas focusing
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ionic focusing
Also known as gas focusing. The introduction of an inert gas into a cathode-ray tube for the concentration of the electron beam. The gas molecules are ionized by the electrons, producing a core of...
inner focusing
In a camera, the movement of one or more lenses behind the front lens, rather than of the front lens itself, to bring the subject into focus. Because internal focusing does not require the front lens...
ionic focusing
Also known as gas focusing. The introduction of an inert gas into a cathode-ray tube for the concentration of the electron beam. The gas molecules are ionized by the electrons, producing a core of...
magnetically focused image tube
A vacuum tube in which a magnetic field is superimposed onto the tube's electrical field. When the two fields are aligned, electrons from the photocathode are accelerated through the tube in a spiral...
paraxial focus
Focus derived from paraxial data.
permanent magnetic focusing
The focusing of an electron beam by a magnetic field that permanently retains the majority of its magnetic properties.
point-focusing collector
A device used in solar systems to direct mirror-reflected sunlight to a heat absorber and heat-driven engine, which turns a generator to produce electricity.
principal focus
->
focal point
That point on the optical axis of a lens, to which an incident bundle of parallel light rays will converge.
principal point of focus
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focal point
That point on the optical axis of a lens, to which an incident bundle of parallel light rays will converge.
proximity-focused image tube
A planar photocathode and a planar phosphor screen mounted in a close-spaced parallel configuration in an evacuated enclosure so that the ensemble of photoelectrons emitted from each photocathode...
rear focusing
A type of internal focusing in which only the lens elements closest to the rear of the lens barrel are moved.
retrofocus lens
Also known as reversed telephoto lens. A lens consisting of an ordinary objective with a negative component near its front focal point. Thus, the back focus is large, relative to its focal length....
short-focus lens
->
wide-angle lens
A wide-angle lens is a type of camera lens that has a shorter focal length than a standard or normal lens, allowing it to capture a broader field of view. Wide-angle lenses are characterized by their...
soft-focus filter
A filter that creates spherical aberration resulting in an image with a soft outline.
soft-focus lens
A lens that exhibits spherical aberration when used at large aperture settings, and that forms an image with a slightly blurred outline.
variable-focus condenser
An Abbe condenser in which the upper lens element is fixed. The lower lens may focus the illumination between the elements so that it emerges from the fixed lens as a large-diameter parallel bundle....
variable-focus lens
A lens assembly containing several movable elements to permit changing of the effective focal length (EFL). Unlike a zoom lens, a variable-focus lens may require refocusing with each change of EFL....
inverted telephoto lens
->
retrofocus lens
Also known as reversed telephoto lens. A lens consisting of an ordinary objective with a negative component near its front focal point. Thus, the back focus is large, relative to its focal length....
reversed telephoto lens
->
retrofocus lens
Also known as reversed telephoto lens. A lens consisting of an ordinary objective with a negative component near its front focal point. Thus, the back focus is large, relative to its focal length....
SELFOC fiber
Derived from "self-focusing,'' Nippon Sheet Glass Co. (NSG) of Japan's trade name for graded-index fiber rods with parabolic index profile, suitable for use as cylindrical microlenses.
SELFOC lens
->
SELFOC fiber
Derived from "self-focusing,'' Nippon Sheet Glass Co. (NSG) of Japan's trade name for graded-index fiber rods with parabolic index profile, suitable for use as cylindrical microlenses.
varifocal
->
variable-focus lens
A lens assembly containing several movable elements to permit changing of the effective focal length (EFL). Unlike a zoom lens, a variable-focus lens may require refocusing with each change of EFL....
abaxial spherical aberration
Abaxial spherical aberration, also called oblique spherical aberration, refers to a specific type of optical aberration that occurs in lens systems. It is a form of spherical aberration that affects...
Abbe condenser
An Abbe condenser is a type of optical component used in microscopy to enhance the illumination of the specimen. Named after the German physicist Ernst Abbe, who developed it in the 19th century, the...
absolute magnification
The value of the distance of distinct vision, minimum focusing distance or near point, divided by the focal length of the lens. Magnification is produced when the optic is placed at its focal...
absorption lens
An absorption lens is a type of optical lens that not only focuses or diverges light but also significantly absorbs certain wavelengths of the incident light. This dual function makes it different...
accommodation
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ocular accommodation
Ocular accommodation is the process by which the eye changes its optical power to maintain a clear image (focus) on an object as its distance varies. This process is essential for seeing objects at...
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