|  | 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

|  | G01 |
MEASURING (counting Fulltext... Hierarchy... Expanded...G06M); TESTING

|  | G01 |
Note(s) This class covers, in addition to "true" measuring instruments, other indicating or recording devices of analogous construction, and also signalling or control devices insofar as they are concerned with measurement (as defined in Note 2 below) and are not specially adapted to the particular purpose of signalling or control. In this class, the following term is used with the meaning indicated: "measuring" is used to cover considerably more than its primary or basic meaning. In this primary sense, it means finding a numerical expression of the value of a variable in relation to a unit or datum or to another variable of the same nature, e.g. expressing a length in terms of another length as in measuring a length with a scale; the value may be obtained directly (as just suggested) or by measuring some other variable of which the value can be related to the value of the required variable, as in measuring a change in temperature by measuring a resultant change in the length of a column of mercury. However, since the same device or instrument may, instead of giving an immediate indication, be used to produce a record or to initiate a signal to produce an indication or control effect, or may be used in combination with other devices or instruments to give a conjoint result from measurement of two or more variables of the same or different kinds, it is necessary to interpret "measuring" as including also any operation that would make it possible to obtain such a numerical expression by the additional use of some way of converting a value into figures. Thus the expression in figures may be actually made by a digital presentation or by reading a scale, or an indication of it may be given without the use of figures, e.g. by some perceptible feature (variable) of the entity (e.g. object, substance, beam of light) of which the variable being measured is a property or condition or by an analogue of such a feature (e.g. the corresponding position of a member without any scale, a corresponding voltage generated in some way). In many cases there is no such value indication but only an indication of difference or equality in relation to a standard or datum (of which the value may or may not be known in figures); the standard or datum may be the value of another variable of the same nature but of a different entity (e.g. a standard measure) or of the same entity at a different time. In its simplest form, measurement may give merely an indication of presence or absence of a certain condition or quality, e.g. movement (in any direction or in a particular direction), or whether a variable exceeds a predetermined value. Attention is drawn to the Notes following the title of section G, especially as regards the definition of the term "variable". In many measuring arrangements, a first variable to be measured is transformed into a second, or further, variables. The second, or further, variables may be (a) a condition related to the first variable and produced in a member, or (b) a displacement of a member. Further transformation may be needed. [6] When classifying such an arrangement, (i) the transformation step, or each transformation step, that is of interest is classified, or (ii) if interest lies only in the system as a whole, the first variable is classified in the appropriate place. [6] This is particularly important where two or more conversions take place, for instance where a first variable, for example pressure, is transformed into a second variable, for example an optical property of a sensing body, and that second variable is expressed by means of a third variable, for example an electric effect. In such a case, the following classification places should be considered: the place for the transformation of the first variable, that for sensing the condition caused by that variable, subclass Fulltext... Hierarchy... Expanded...G01D for expression of the measurement, and finally the place for the overall system, if any. [6] The measurement of change in the value of a physical property is classified in the same subclass as the measurement of that physical property, e.g. measurement of expansion of length is classified in subclass Fulltext... Hierarchy... Expanded...G01B.

|  | G01J |
MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRA-RED, VISIBLE OR ULTRA-VIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources Fulltext... Hierarchy... Expanded...F21, Fulltext... Hierarchy... Expanded...H01J, Fulltext... Hierarchy... Expanded...H01K, Fulltext... Hierarchy... Expanded...H05B; investigating properties of materials by optical means Fulltext... Hierarchy... Expanded...G01N) [2]

|  | G01J |
Note(s) This subclass covers the detection of the presence or absence of infra-red, visible, or ultra-violet light, not otherwise provided for. Attention is drawn to the Notes following the title of class Fulltext... Hierarchy... Expanded...G01.

|  | G01J |
Subclass index
PHOTOMETRY; PYROMETRY | 1/00; 5/00
SPECTROMETRY; MEASURING: POLARISATION; VELOCITY; PHASE; PULSES | 3/00; 4/00; 7/00; 9/00; 11/00

|  | G01J 1/00 |
Photometry, e.g. photographic exposure meter (spectrophotometry Fulltext... Hierarchy... Expanded...G01J 3/00; specially adapted for radiation pyrometry Fulltext... Hierarchy... Expanded...G01J 5/00)

|  | G01J 1/02 |
· | Details

|  | G01J 1/04 |
· · | Optical or mechanical part

|  | G01J 1/06 |
· · · | Restricting the angle of incident light

|  | G01J 1/08 |
· · | Arrangements of light sources specially adapted for photometry

|  | G01J 1/10 |
· | by comparison with reference light or electric value

|  | G01J 1/12 |
· · | using wholly visual means (Fulltext... Hierarchy... Expanded...G01J 1/20 takes precedence)

|  | G01J 1/14 |
· · · | using comparison with a surface of graded brightness

|  | G01J 1/16 |
· · | using electric radiation detectors (Fulltext... Hierarchy... Expanded...G01J 1/20 takes precedence)

|  | G01J 1/18 |
· · · | using comparison with a reference electric value

|  | G01J 1/20 |
· · | intensity of the measured or reference value being varied to equalise their effects at the detector, e.g. by varying incidence angle

|  | G01J 1/22 |
· · · | using a variable element in the light-path, e.g. filter, polarising means (Fulltext... Hierarchy... Expanded...G01J 1/34 takes precedence)

|  | G01J 1/24 |
· · · · | using electric radiation detectors

|  | G01J 1/26 |
· · · · · | adapted for automatic variation of the measured or reference value (regulation of light intensity Fulltext... Hierarchy... Expanded...G05D 25/00)

|  | G01J 1/28 |
· · · | using variation of intensity or distance of source (Fulltext... Hierarchy... Expanded...G01J 1/34 takes precedence)

|  | G01J 1/30 |
· · · · | using electric radiation detectors

|  | G01J 1/32 |
· · · · · | adapted for automatic variation of the measured or reference value (regulation of light intensity Fulltext... Hierarchy... Expanded...G05D 25/00)

|  | G01J 1/34 |
· · · | using separate light-paths used alternately or sequentially, e.g. flicker

|  | G01J 1/36 |
· · · · | using electric radiation detectors

|  | G01J 1/38 |
· | using wholly visual means (Fulltext... Hierarchy... Expanded...G01J 1/10 takes precedence)

|  | G01J 1/40 |
· · | using limit of visibility or extinction effect

|  | G01J 1/42 |
· | using electric radiation detectors (optical or mechanical part Fulltext... Hierarchy... Expanded...G01J 1/04; by comparison with a reference light or electric value Fulltext... Hierarchy... Expanded...G01J 1/10)

|  | G01J 1/44 |
· · | Electric circuits

|  | G01J 1/46 |
· · · | using a capacitor

|  | G01J 1/48 |
· | using chemical effects

|  | G01J 1/50 |
· · | using change in colour of an indicator, e.g. actinometer

|  | G01J 1/52 |
· · | using photographic effects

|  | G01J 1/54 |
· · | by observing photo-reactions between gases

|  | G01J 1/56 |
· | using radiation pressure or radiometer effect

|  | G01J 1/58 |
· | using luminescence generated by light

|  | G01J 1/60 |
· | by measuring the pupil of the eye

|  | G01J 3/00 |
Spectrometry; Spectrophotometry; Monochromators; Measuring colours [4]

|  | G01J 3/02 |
· | Details

|  | G01J 3/04 |
· · | Slit arrangements

|  | G01J 3/06 |
· · | Scanning arrangements

|  | G01J 3/08 |
· · | Beam-switching arrangements

|  | G01J 3/10 |
· · | Arrangements of light sources specially adapted for spectrometry or colorimetry

|  | G01J 3/12 |
· | Generating the spectrum; Monochromators

|  | G01J 3/14 |
· · | using refracting elements, e.g. prism (Fulltext... Hierarchy... Expanded...G01J 3/18, Fulltext... Hierarchy... Expanded...G01J 3/26 take precedence)

|  | G01J 3/16 |
· · · | with autocollimation

|  | G01J 3/18 |
· · | using diffraction elements, e.g. grating (gratings per se Fulltext... Hierarchy... Expanded...G02B)

|  | G01J 3/20 |
· · · | Rowland circle spectrometers

|  | G01J 3/22 |
· · · | Littrow mirror spectrometers

|  | G01J 3/24 |
· · · | using gratings profiled to favour a specific order

|  | G01J 3/26 |
· · | using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filter

|  | G01J 3/28 |
· | Investigating the spectrum (using colour filters Fulltext... Hierarchy... Expanded...G01J 3/51) [4]

|  | G01J 3/30 |
· · | Measuring the intensity of spectral lines directly on the spectrum itself (Fulltext... Hierarchy... Expanded...G01J 3/42, Fulltext... Hierarchy... Expanded...G01J 3/44 take precedence)

|  | G01J 3/32 |
· · · | Investigating bands of a spectrum in sequence by a single detector

|  | G01J 3/36 |
· · · | Investigating two or more bands of a spectrum by separate detectors

|  | G01J 3/40 |
· · | Measuring the intensity of spectral lines by determining density of a photograph of the spectrum; Spectrography (Fulltext... Hierarchy... Expanded...G01J 3/42, Fulltext... Hierarchy... Expanded...G01J 3/44 take precedence) [4]

|  | G01J 3/42 |
· · | Absorption spectrometry; Double-beam spectrometry; Flicker spectrometry; Reflection spectrometry (beam-switching arrangements Fulltext... Hierarchy... Expanded...G01J 3/08) [4]

|  | G01J 3/427 |
· · · | Dual wavelength spectrometry [4]

|  | G01J 3/433 |
· · · | Modulation spectrometry; Derivative spectrometry [4]

|  | G01J 3/44 |
· · | Raman spectrometry; Scattering spectrometry [4]

|  | G01J 3/443 |
· · | Emission spectrometry [4]

|  | G01J 3/447 |
· · | Polarisation spectrometry [4]

|  | G01J 3/45 |
· · | Interferometric spectrometry [4]

|  | G01J 3/453 |
· · · | by correlation of the amplitudes [4]

|  | G01J 3/457 |
· · | Correlation spectrometry, e.g. of the intensity (Fulltext... Hierarchy... Expanded...G01J 3/453 takes precedence) [4]

|  | G01J 3/46 |
· | Measurement of colour; Colour measuring devices, e.g. colorimeters (measuring colour temperature Fulltext... Hierarchy... Expanded...G01J 5/60) [4]

|  | G01J 3/50 |
· · | using electric radiation detectors [4]

|  | G01J 3/51 |
· · · | using colour filters [4]

|  | G01J 3/52 |
· · | using colour charts

|  | G01J 4/00 |
Measuring polarisation of light (investigating or analysing materials by measuring rotation of plane of polarised light Fulltext... Hierarchy... Expanded...G01N 21/21) [2]

|  | G01J 4/02 |
· | Polarimeters of separated-field type; Polarimeters of half-shadow type [2]

|  | G01J 4/04 |
· | Polarimeters using electric detection means (Fulltext... Hierarchy... Expanded...G01J 4/02 takes precedence) [2]

|  | G01J 5/00 |
Radiation pyrometry (photometry in general Fulltext... Hierarchy... Expanded...G01J 1/00; spectrometry in general Fulltext... Hierarchy... Expanded...G01J 3/00)

|  | G01J 5/02 |
· | Details

|  | G01J 5/04 |
· · | Casings

|  | G01J 5/06 |
· · | Arrangements for eliminating effects of disturbing radiation

|  | G01J 5/08 |
· · | Optical features

|  | G01J 5/10 |
· | using electric radiation detectors

|  | G01J 5/12 |
· · | using thermoelectric elements, e.g. thermocouples (thermoelectric elements per se Fulltext... Hierarchy... Expanded...H01L 35/00, Fulltext... Hierarchy... Expanded...H01L 37/00)

|  | G01J 5/14 |
· · · | Electrical features

|  | G01J 5/16 |
· · · · | Arrangements with respect to the cold junction; Compensating influence of ambient temperature or other variables

|  | G01J 5/18 |
· · · · | Special adaptation for indicating or recording (indicating or recording measured values in general Fulltext... Hierarchy... Expanded...G01D)

|  | G01J 5/20 |
· · | using resistors, thermistors, or semiconductors sensitive to radiation

|  | G01J 5/22 |
· · · | Electrical features

|  | G01J 5/24 |
· · · · | Use of a specially-adapted circuit, e.g. bridge circuit

|  | G01J 5/26 |
· · · · | Special adaptation for indicating or recording

|  | G01J 5/28 |
· · | using photo-emissive, photo-conductive, or photo-voltaic cells

|  | G01J 5/30 |
· · · | Electrical features

|  | G01J 5/32 |
· · · · | Special adaptation for indicating or recording

|  | G01J 5/34 |
· · | using capacitors

|  | G01J 5/36 |
· · | using ionisation of gases

|  | G01J 5/38 |
· | using extension or expansion of solids or fluids

|  | G01J 5/40 |
· · | using bimetallic elements

|  | G01J 5/42 |
· · | using Golay cells

|  | G01J 5/44 |
· · | using change of resonant frequency, e.g. of piezo-electric crystal

|  | G01J 5/46 |
· | using radiation pressure or radiometer effect

|  | G01J 5/48 |
· | using wholly visual means

|  | G01J 5/50 |
· | using techniques specified in the subgroups below

|  | G01J 5/52 |
· · | using comparison with reference sources, e.g. disappearing-filament pyrometer

|  | G01J 5/54 |
· · · | Optical features

|  | G01J 5/56 |
· · · | Electrical features

|  | G01J 5/58 |
· · | using absorption; using polarisation; using extinction effect

|  | G01J 5/60 |
· · | using determination of colour temperature

|  | G01J 5/62 |
· · | using means for chopping the light

|  | G01J 7/00 |
Measuring velocity of light

|  | G01J 9/00 |
Measuring optical phase difference (devices or arrangements for controlling the phase of light beams Fulltext... Hierarchy... Expanded...G02F 1/01); Determining degree of coherence; Measuring optical wavelength (spectrometry Fulltext... Hierarchy... Expanded...G02F 3/00) [3]

|  | G01J 9/02 |
· | by interferometric methods (using interferometers for measuring optically the linear dimensions of objects Fulltext... Hierarchy... Expanded...G01B 9/02) [3]

|  | G01J 9/04 |
· | by beating two waves of the same source but of different frequency and measuring the phase shift of the lower frequency obtained [3]

|  | G01J 11/00 |
Measuring the characteristics of individual optical pulses or of optical pulse trains [5]