afocal system

(noun)

An optical system that produces no net convergence or divergence of the beam, i.e. has an infinite effective focal length. This type of system can be created with a pair of optical elements where the distance between the elements is equal to the sum of each element's focal length (d = f1+f2).

Related Terms

Examples of afocal system in the following topics:

  • Combinations of Lenses

    • If two thin lenses are separated in air by some distance d (where d is smaller than the focal length of the first lens), the focal length for the combined system is given by
    • This type of system is called an afocal system, since it produces no net convergence or divergence of the beam.
    • Although the system does not alter the divergence of a collimated beam, it does alter the width of the beam.
    • (b) Multiple-lens systems, such as this achromatic doublet, can partially correct chromatic aberrations, but they may require lenses of different materials and add to the expense of optical systems such as cameras.

  • Parasympathetic Responses

    • The parasympathetic nervous system regulates organ and gland functions during rest and is considered a slowly activated, dampening system.
    • The parasympathetic nervous system (PSNS, or occasionally PNS) is one of the two main divisions of the autonomic nervous system (ANS).
    • The autonomic nervous system (ANS, or visceral nervous system, or involuntary nervous system) is the part of the peripheral nervous system that acts as a control system, functioning largely below the level of consciousness and controlling visceral functions.
    • The sympathetic nervous system can be considered a quick response, mobilizing system; and the parasympathetic system is a more slowly activated, dampening system.
    • The parasympathetic nervous system, shown in blue, is a division of the autonomic nervous system.

  • Introduction to Systems of Equations

    • A system of equations consists of two or more equations with two or more variables, where any solution must satisfy all of the equations in the system at the same time.
    • To find the unique solution to a system of linear equations, we must find a numerical value for each variable in the system that will satisfy all of the system's equations at the same time.
    • A solution to the system above is given by
    • An inconsistent system has no solution.
    • A dependent system has infinitely many solutions.

  • Expert Systems

    • An expert system consists of both an inference engine and a knowledge base and has decision-making abilities.
    • An expert system has a unique structure, different from traditional computer programs.
    • Knowledge-based systems are systems based on the methods and techniques of artificial Intelligence.
    • Knowledge base systems (KBS) go beyond the decision support philosophy to incorporate expert system technology into the decision-making framework.
    • Break down expert systems to the inference engine, the knowledge base, and conversational

  • Comparing the Somatic and Autonomic Nervous Systems

    • The peripheral nervous system (PNS) is divided into the somatic nervous system and the autonomic nervous system.
    • The somatic nervous system controls all voluntary muscular systems within the body, and also mediates involuntary reflex arcs.
    • The somatic nervous system consists of three parts:
    • The autonomic nervous system (ANS) is the part of the peripheral nervous system that acts as a control system, functioning largely below the level of consciousness and controlling visceral functions.
    • The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.

  • The Systems Viewpoint

    • Systems thinking is an approach to problem solving that considers the overall system instead of focusing on specific parts of a system.
    • Systems thinking is the process of understanding how people and situations influence one another within a closed system.
    • In business, management also involves systems thinking.
    • Systems generally contain the following aspects:
    • Practitioners of systems thinking believe that the component parts of a system can best be understood, and best analyzed, in the context of their relationships with other parts of a system .

  • Comparison of Enthalpy to Internal Energy

    • A thermodynamic system can be any physical system with a well-defined volume in space.
    • The outer edge of the system is referred to as its boundary, which often separates the system from the surroundings.
    • Hence, -q means the system loses heat, while +q means a system gains heat.
    • Similarly, +w means work is done on the system, while -w means work is done by the system.
    • However, in open systems, the pressure of the system and the surroundings has stayed constant.

  • Introduction to the Nervous System

    • The basic unit of the nervous system is the neuron.
    • The nervous system can be divided into two major parts—the central nervous system (CNS) and the peripheral nervous system (PNS).
    • The peripheral nervous system includes a large system of nerves that are linked to the brain and spinal cord.
    • The PNS can be further subdivided into the autonomic nervous system and the somatic nervous system.
    • The nervous system of the human body, including the brain and spinal cord (central nervous system) and all the nerves of the body (peripheral nervous system).

  • Plant Tissues and Organ Systems

  • The Continental System