focal length

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an expression of the longest dimension of an object, or of the measurement between its two ends.
crown-heel length (CHL) the distance from the crown of the head to the heel in embryos, fetuses, and infants; the equivalent of standing height in older persons.
Measuring an infant's crown-heel length. From Lammon et al., 1996.
crown-rump length (CRL) the distance from the crown of the head to the breech in embryos, fetuses, and infants; the equivalent of sitting height in older subjects.
cycle length in cardiac pacing terminology, the time interval in milliseconds from one event to the next; it is the inverse of the intrinsic rate (beats per minute) or the paced rate (pulses per minute).
focal length the distance between a lens and an object from which all rays of light are brought to a focus.

focal length

In optics, the length from the lens to the point of focus of light rays passing through the lens.
See also: length

length, focal

The linear distance separating the principal focal point (or focus) of an optical system from a point of reference (e.g. vertex, principal point, nodal point). The first (anterior) focal length is the distance from the lens (or first principal point) to the first principal focus. The second (posterior) focal length is the distance from the lens (or second principal point) to the second principal focus. Symbol: f.In a spherical mirror the focal length f, i.e. the distance between the focal point and the pole of the mirror, is equal to half its radius of curvature r
= r/2Syn. focal distance. See principal focus; mirror; cardinal points; principal points; equivalent power; refractive power; sign convention.


1. limited to a small area or volume.
2. pertaining to or emanating from focus.

focal distance
see focal-film distance.
focal length
the distance between the lens and an object from which all rays of light are brought to a focus.
focal liver disease
widely disseminated micro-abscesses or abscesses, migration paths of helminth larvae.
focal macular melanosis
dark colored spots on the skin, not elevated above the skin surface but apt to be confused with melanosis.
focal myelitis-encephalitis
widely disseminated inflammatory lesions, usually the result of blood-borne infection, in brain and spinal cord.
focal symmetrical encephalomalacia
see focal symmetrical encephalomalacia.
focal symmetrical spinal poliomalacia
see focal symmetrical spinal poliomalacia.
focal ulcerative dermatitis
manifest by ulcers in the unfeathered anterior breast skin of 4 to 5 months old male turkeys. The incidence is influenced by litter type. Called also breast buttons.
focal zone
in ultrasound, the area of the transducer where the sound beam is most sharply focussed and where the area under examination will give the best image.
References in periodicals archive ?
6) point to Layer #26, #25 and Layer #27, Content-based Autofocus approach is able to bring out the focus of all planes at z-postion 22, #24 and #26 respectively #27.
The dispute with Autofocus was based on evidence the consultancy gave in court over "spot rates" - estimates of how much cars cost to replace.
poLight has developed three different actuated autofocus devices based on a patented technology using its optical MEMS and polymer.
Most tools add more data to the long list my security operations team needs to deal with each day, but AutoFocus allowed us to quickly separate the most critical, and potentially damaging, attacks for immediate response.
Nikon's SWM converts "traveling waves" into rotational energy to focus the optics, which achieves extremely quiet autofocus photography.
The company was planning to take legal action against Suffolk-based Autofocus over thousands of cases it said had cost it as much as pounds 22 million.
Varioptic develops and sells optical Autofocus Solutions based on liquid lenses.
M/A mode enables switching from autofocus to manual focus, even during
Focusing screen: Fixed Nikon Clear Matte Screen 11 with central focus brackets for autofocus operation
Varioptic has considerable background experience in the development of proprietary materials for liquid lens applications and significant progress has been made recently to design reliable liquid formulations for mobile phone camera modules," says Paul Morris, director, Dow Venture Capital "As Varioptic moves forward from AutoFocus applications to other applications (such as microzoom) the requirements are even more challenging.
Other cameras include the Zoom-Touch 105 VR QD, the world's first camera to utilize Vibration-Reduction technology; and the Lite-Touch Zoom, the smallest autofocus compact zoom camera manufactured to date.
With Canon's new Face Detection AF/AE technology (working in concert with Canon's 9-point Autofocus system), the camera can detect, lock on and track up to nine human faces in a scene simply by pressing the shutter button halfway.