|  | G |
SECTION G — PHYSICS

|  | G |
Note(s) In this section, the following term is used with the meaning indicated: "variable" (as a noun) means a feature or property (e.g., a dimension, a physical condition such as temperature, a quality such as density or colour) which, in respect of a particular entity (e.g., an object, a quantity of a substance, a beam of light) and at a particular instant, is capable of being measured; the variable may change, so that its numerical expression may assume different values at different times, in different conditions or in individual cases, but may be constant in respect of a particular entity in certain conditions or for practical purposes (e.g., the length of a bar may be regarded as constant for many purposes). Attention is drawn to the definitions of terms or expressions used, appearing in the notes of several of the classes in this section, in particular those of "measuring" in class Fulltext... Hierarchy... Expanded...G01 and "control" and "regulation" in class Fulltext... Hierarchy... Expanded...G05. Classification in this section may present more difficulty than in other sections, because the distinction between different fields of use rests to a considerable extent on differences in the intention of the user rather than on any constructional differences or differences in the manner of use, and because the subjects dealt with are often in effect systems or combinations, which have features or parts in common, rather than "things", which are readily distinguishable as a whole. For example, information (e.g., a set of figures) may be displayed for the purpose of education or advertising (Fulltext... Hierarchy... Expanded...G09), for enabling the result of a measurement to be known (Fulltext... Hierarchy... Expanded...G01), for signalling the information to a distant point or for giving information which has been signalled from a distant point (Fulltext... Hierarchy... Expanded...G08). The words used to describe the purpose depend on features that may be irrelevant to the form of the apparatus concerned, for example, such features as the desired effect on the person who sees the display, or whether the display is controlled from a remote point. Again, a device which responds to some change in a condition, e.g., in the pressure of a fluid, may be used, without modification of the device itself, to give information about the pressure (Fulltext... Hierarchy... Expanded...G01L) or about some other condition linked to the pressure (another subclass of class Fulltext... Hierarchy... Expanded...G01, e.g., Fulltext... Hierarchy... Expanded...G01K for temperature), to make a record of the pressure or of its occurrence (Fulltext... Hierarchy... Expanded...G07C), to give an alarm (Fulltext... Hierarchy... Expanded...G08B), or to control another apparatus (Fulltext... Hierarchy... Expanded...G05). The classification scheme is intended to enable things of a similar nature (as indicated above) to be classified together. It is therefore particularly necessary for the real nature of any technical subject to be decided before it can be properly classified.

INSTRUMENTS

|  | G02 |
OPTICS (making optical elements or apparatus Fulltext... Hierarchy... Expanded...B24B, Fulltext... Hierarchy... Expanded...B29D 11/00, Fulltext... Hierarchy... Expanded...C03, or other appropriate subclasses or classes; materials per se, see the relevant places, e.g. Fulltext... Hierarchy... Expanded...C03B, Fulltext... Hierarchy... Expanded...C03C)

|  | G02 |
Note(s) In this class, the following expression is used with the meaning indicated: "optical" applies not only to visible light but also to ultra-violet or infra-red radiations. [4]

|  | G02B |
OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS (Fulltext... Hierarchy... Expanded...G02F takes precedence; measuring-instruments, see the relevant subclass of class Fulltext... Hierarchy... Expanded...G01, e.g. optical rangefinders Fulltext... Hierarchy... Expanded...G01C; testing of optical elements, systems, or apparatus Fulltext... Hierarchy... Expanded...G01M 11/00; spectacles Fulltext... Hierarchy... Expanded...G02C; apparatus or arrangements for taking photographs or for projecting or viewing them Fulltext... Hierarchy... Expanded...G03B; sound lenses Fulltext... Hierarchy... Expanded...G10K 11/30; electron and ion "optics" Fulltext... Hierarchy... Expanded...H01J; X-ray "optics" Fulltext... Hierarchy... Expanded...H01J, Fulltext... Hierarchy... Expanded...H05G 1/00; optical elements structurally combined with electric discharge tubes Fulltext... Hierarchy... Expanded...H01J 5/16, Fulltext... Hierarchy... Expanded...H01J 29/89, Fulltext... Hierarchy... Expanded...H01J 37/22; microwave "optics" Fulltext... Hierarchy... Expanded...H01Q; combination of optical elements with television receivers Fulltext... Hierarchy... Expanded...H04N 5/72; optical systems or arrangements in colour television systems Fulltext... Hierarchy... Expanded...H04N 9/00; heating arrangements specially adapted for transparent or reflecting areas Fulltext... Hierarchy... Expanded...H05B 3/84)

|  | G02B |
Note(s) In this subclass, the following terms or expressions are used with the meanings indicated: "simple lens or prism" means a single lens or prism; "compound lens or prism" means an optical member, the constituents of which either are close together without air-space or (except in group Fulltext... Hierarchy... Expanded...G02B 11/00) are "in broken contact", i.e. with the air-space between the constituents having no essential optical influence; "objective" means a lens or an optical system designed to produce a real image of a real object; "eyepiece" means a lens or an optical system designed to produce a virtual image for viewing by the eye or by another optical system; "front" or "rear" is determined by looking from the more distant conjugate.

|  | G02B |
Subclass index
OPTICAL ELEMENTS |
Characterised by their structure: lenses; light guides; other elements | 3/00; 6/00; 5/00
Characterised by the material | 1/00
OPTICAL SYSTEMS |
General structure: number and arrangements of optical components | 9/00, 11/00
Special structures: according to purpose; with variable magnification; with reflecting surfaces | 13/00; 15/00; 17/00
Other systems | 27/00
STRUCTURAL DETAILS OF ARRANGEMENTS COMPRISING LIGHT GUIDES AND OTHER OPTICAL ELEMENTS | 6/00
OPTICAL APPARATUS |
Condensers | 19/00
Microscopes | 21/00
Telescopes, periscopes, instruments for viewing the inside of hollow bodies, viewfinders, aiming or sighting devices | 23/00
Eyepieces, magnifying glasses | 25/00
Other apparatus | 27/00
CONTROL OF LIGHT | 26/00
MOUNTINGS, ADJUSTING MEANS, LIGHT-TIGHT CONNECTIONS | 7/00

|  | G02C |
SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES (trial frames for testing the eyes Fulltext... Hierarchy... Expanded...A61B 3/04; goggles or eyeshields not having the same features as spectacles Fulltext... Hierarchy... Expanded...A61F 9/00)

|  | G02C |
Note(s) This subclass covers also contact lenses for the eyes, monocles, pince-nez, or lorgnettes.

|  | G02C |
Subclass index
OPTICAL PARTS | 7/00
NON-OPTICAL PARTS |
Supporting arrangements; adjuncts | 3/00, 5/00; 11/00
ATTACHMENTS OF OPTICAL PARTS TO NON-OPTICAL PARTS |
Principal; auxiliary | 1/00; 9/00
ASSEMBLING, REPAIRING, CLEANING | 13/00

|  | G02F |
DEVICES OR ARRANGEMENTS, THE OPTICAL OPERATION OF WHICH IS MODIFIED BY CHANGING THE OPTICAL PROPERTIES OF THE MEDIUM OF THE DEVICES OR ARRANGEMENTS FOR THE CONTROL OF THE INTENSITY, COLOUR, PHASE, POLARISATION OR DIRECTION OF LIGHT, e.g. SWITCHING, GATING, MODULATING OR DEMODULATING; TECHNIQUES OR PROCEDURES FOR THE OPERATION THEREOF; FREQUENCY-CHANGING; NON-LINEAR OPTICS; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS (optical transfer means between sensing member and indicating or recording part in connection with measuring Fulltext... Hierarchy... Expanded...G01D 5/26; devices in which mathematical operations are carried out with optical elements Fulltext... Hierarchy... Expanded...G06E 3/00; electrical signal transmission systems using optical means to convert the input signal Fulltext... Hierarchy... Expanded...G08C 19/36; information-recording by electric or magnetic means and reproducing by sensing optical properties Fulltext... Hierarchy... Expanded...G11B 11/00; static stores using optical elements Fulltext... Hierarchy... Expanded...G11C 13/04; transmission systems employing electromagnetic waves other than radio waves, e.g. light, infra-red radiation, Fulltext... Hierarchy... Expanded...H04B 10/00; optical multiplex systems Fulltext... Hierarchy... Expanded...H04J 14/00; pictorial communication, e.g. television Fulltext... Hierarchy... Expanded...H04N) [2,4]