Abstract: A gaseous mixture containing a number of molecular gases is analyzed to establish the amount of each individual gas by directing a light beam along a measurement path 11 through the gas. Each of the spectral component is selected to coincide with a respective vibrational-rotational-excitation band of one of the gases. The attenuation produced in each of the spectral components in its passage along the measurement path 11 serves as an indication of the concentration of the associated gas. The spectral components are generated either from distinct light sources 12, 13, 14 or are alternatively produced by spectral division of light from a multiple line or broad band source. Different marking frequencies f1, f2 and f3 are used to modulate each of the spectral components so that the signal received from the single photoelectric receiver 18 can be subsequently demodulated by three demodulators 19, 20, 21 to recover information relating to the individual spectral components.

Abstract: Closing and opening movements are effected by a reversible motor M. The motor M receives its power from a supply U via a feed circuit which includes switch contacts r.sub.1, r.sub.2 controlled by a relay R. The arrangement is such that a closing movement takes place when the relay is energized and an opening movement when the relay is deenergized. To select these two movements there is provided a selector switch S in the feed circuit which has two operative positions and an intermediate neutral position. The excitation winding of the relay R is included in a monitoring circuit in parallel with a strip-like safety switch SL. The strip-like safety switch SL is positioned in the path of the closing movement and has two strip-like contact bands 1, 2 which are pressed together if an object should become trapped in the path of the closing movement. If this occurs the excitation winding of the relay is short circuited and it automatically reverses the motor to convert the closing movement into an opening movement.

Abstract: Light barrier apparatus generally features a light transmitter for projecting light across a region to be monitored to a light receiver. The light transmitter and receiver units can either be separate or can be combined in a single housing and used in conjunction with a retro-reflector for returning light from the sender to the receiver.In any of these arrangements the light transmitter and/or sender units incorporate photoelectric converter components 11, 12 and optical projection components 13, 14 together with electronic processing elements which enable interruption of the light barrier to be detected. The present arrangement features a housing 17 including at least one sealed chamber 15, 15', 15" containing solely the optical and photoelectric converter elements. These chambers are thus sealed against the ingress of contamination and moisture. The remaining elements of the electronic processing circuit are housed separately in a further chamber 16.

Abstract: An optical electronic distance sensor utilizes a V-light barrier in which a light transmitter 11 transmits a substantially parallel light beam 14 at a defined angle and a light receiver 12 receives a substantially parallel light beam 15 at a defined angle and delivers an electrical output signal dependent on the intensity of the received light beam. The distance of the intersection of the transmitted and received light beam paths, i.e. the apex of the V, from the light transmitter and receiver defines the sensing distance of the light barrier and is adjusted by adjusting the separation of the light transmitter and receiver. For this purpose the light transmitter and receiver are displaceably mounted on a mounting rail. The distance sensor is particularly useful in indoor carparks for determining the presence or absence of a vehicle in a parking space.

Abstract: A light transmitter directs light via a first polarizing filter, so that it is polarized in one plane, to a retro-reflecting device across a region to be monitored and the retro-reflector produces depolarization, or rotates the plane of polarization of the light, prior to directing it to a light receiver positioned adjacent the light transmitter. A second polarizing filter crossed relative to the first is positioned in front of the light receiver so that the light receiver will only recognize light whose plane of polarization has been appropriately rotated by the retro-reflector but not light reflected from a strongly reflecting object which interrupts the light barrier. Threshold circuitry evaluates whether a signal from a photoelectric convertor embodied in the receiver lies above or below a given threshold. Weakly reflecting objects are not recognized, because light reflected therefrom will be too weak to generate a signal above the required threshold. Various polarizing arrangements are described.

Abstract: An entrapment prevention device for ensuring that people or obstacles do not become trapped in the path of automatic doors, windows and the like features an elongate sensor which can be fitted along an edge of an opening or of a closure member adapted to close the opening.The sensor features a pair 11 of electrically conductive bands 13 and 14 which are held spaced apart and facing each other by insulating strips 17 with the pair of bands being wound in helical form round a core 12 to form an elongate structure. A series of transverse slots are provided in the surface of the radially outer band 14 so that the remaining web portions 15 can be easily deflected by light contact pressure to electrically contact the radially inner band 14. This electrical contact is sensed by a monitoring circuit 24 which energizes a relay 26 to stop or reverse the automatic drive. The pair of bands 11 is surrounded by an outer helically wound resilient cushion 18 and is enclosed in a continuous outer sleeve 19.

Abstract: A light grid arrangement features a row of light emitting diodes 0 to 9 which are periodically switched on one after the other by a ring counter 11 and are arranged to direct their light through a monitoring region 23 towards an image forming optical means which is conveniently in the form of a concave mirror 24. The light beams are concentrated by the concave mirror 24 onto a photodetector 18 arranged behind a slot aperture 25 located at the focal point of the concave mirror. Missing pulses from the photodetector are detected by processing circuitry 26 to indicate obstruction of the light grid. The width of the slot aperture 25 restricts the width of each individual light beam so that only beams of light from the light emitting diodes that are generally parallel to the axis of the concave mirror are detected. In this way costly optical focussing elements are avoided as are the difficulties of aligning these optical elements with the other optical components of a system.

Abstract: Apparatus for determining faults in strip material is disclosed in this application which enables both color defects and distortions of the surface of the strip material to be recognized.It its general form the apparatus illuminates the material surface at a specific angle with white light and an optical system directs the light leaving the surface to a number of photodetection devices which detect the various angles at which light leaves the surface. The deviations of these angles from the direction of specular reflection, or unimpeded transmission, are characteristic of the nature of the distortion of the surface of the strip material. At least the photodetection device which receives the specularly reflected or normally transmitted light and preferably all the photodetection devices, includes two photodetectors, which detect light in different spectral ranges by means of associated beam splitting and filtering devices. In this way color defects such as stains or spots on the surface can also be recognized.

Abstract: Detection apparatus for finding holes in moving webs uses a row of individual mutually sideways displaced stepped mirror strips in combination with a scanning device which periodically scans a light beam from a laser over the individual mirrors of each strip, to generate a scanning light curtain directed at the surface of a web. A detection device comprising a row of individual Fresnel lenses and associated photoelectronic detectors is arranged parallel to the row of mirror strips to receive light transmitted through any hole present in the web. The individual Fresnel lenses focus any light received onto their associated photoelectric detectors the outputs from which signify the presence of the hole. Means are provided for introducing a degree of divergence into the beams deflected from the stepped mirrors and forming the light curtain whereby the light curtain scans a cross the web without gaps.

Abstract: Apparatus for determining faults on strip material includes a scanning device for linewise scanning of a strip of material with a light beam, a first cylindrical lens extending parallel to the direction of the scanned lines and arranged to image the scanned line on a first cylindrical mirror with its focal line at right angles to the direction of the scanned lines.Faults in the surface of the strip material such as dents, bumps and scratches give rise to characteristic deviations or deflection of the scanning light and the arrangement of the first cylindrical lens and first cylindrical mirror produce a convenient spatial distribution of the light in the image field of the first cylindrical mirror which can be detected by suitably disposed detectors to yield information about the nature and location of the fault. The apparatus includes various other optical components to produce a desired grouping of the deviated light beams to aid their identification and subsequent analysis.

Abstract: A banknote condition monitoring apparatus features a mirror wheel (22) located substantially at the focus of a concave mirror strip (25) with an intervening plane mirror (26) to fold the beam path. The mirror wheel (22) scans an incident light beam from a source (28) to form a transmitted light beam in the image space of the concave mirror (25) which is continuously displaced parallel to itself to and fro through the image space. The transmitted light beam is directed via a cylindrical lens (14) onto the surface of a drum (11) carrying the banknotes (12) to be monitored on its peripheral surface by way of air suction via the channels (32). Light remitted from the surface of the banknote is directed through the lower half of the cylindrical lens (14), impinges on a light conducting rod (15) and is detected at an and face of the light conducting rod by a light receiving device (33).

Abstract: Hole seeking apparatus for material webs is disclosed which features a light source for projecting a light beam onto a mirror wheel arrangement located optically in front of a concave mirror so as to produce a scanning beam in the image space of the concave mirror. The scanning beam is continuously displaced parallel to itself so as to periodically scan along a scanning path on the material web. The mirror wheel arrangement consists of two substantially identical mirror wheels which lie coaxially on one another and which are displaced by a half pitch.The dimensions of the light bead at its point of incidence on the mirror wheels and the optical geometry of the apparatus are selected to avoid light being scattered at an edge of either of the mirror wheels and passing to either side of the web. Scattered light is thus prevented from falling on a light receiving device arranged behind the web and intended to detect the presence of holes therein.

Abstract: An adjustment device for aligning a group of cyclically switched transmitters or receivers with a single receiver or transmitter of the kind in which a series of spatially spaced beams pass between the transmitters and the receiver, or alternatively between the transmitter and the receivers. In a preferred form the adjustment device is used to ensure alignment of a row of infra-red transmitters which direct beams of light to a photoelectric converter arranged at the focus of a concave mirror. The adjustment device features a coincidence circuit the outputs from which indicate that signals transmitted from the end transmitters of the row are received at the photoelectric converter. The outputs are used to energize respective adjustment indicating lamps. In a particularly preferred arrangement threshold circuitry is used to produce winking of the lamps when approximate adjustment has been achieved; continuous lighting of the lamps shows that accurate adjustment is present.

Abstract: A safety circuit for a potentially dangerous machine monitored by light and which works in an operating cycle. A safety circuit is described which utilizes a series of relays each of which is switched from an energized to a de-energized condition once during each working cycle of the machine so that each of the relay contact also opens and closes during the working cycle. In this way each relay contact is tested. The relays are so interconnected that if one contact should stick it will interrupt the sequence and will ensure the potentially dangerous machine e.g. a press is rendered inactive. Circuits are given for both hand fed and automatic machines which are monitored by a light barrier or curtain. For the hand fed machine the cycle is initiated by the operator reaching through the light barrier to insert an object into the machine. For an automatically fed machine the test cycle is initiated by a switch automatically activated once per cycle.

Abstract: A transmitting lens and a receiving lens are arranged alongside each other on one narrow side of a shallow housing so that a pencil beam of light transmitted by the transmitting lens and reflected by a separate reflector is received by the receiving lens and concentrated onto a photoelectric converter. Interruption of the pencil beam of light results in interruption of the output signal from the photoelectric converter and is detected and used to actuate an alarm signaller located within the housing. The alarm signaller, which is preferably a buzzer, is connected with the housing to form a single constructional unit. The optics and electronics are conveniently mounted on a circuit board which is conveniently located within the housing and secured by a resilient cushion.

Abstract: The optical apparatus basically comprises a cylindrical lens which gathers light reflected at various angles from a material surface and projects it onto a strip like curved mirror with its axis at right angles to the lens and which subsequently concentrates the light onto a number of photodetectors each of which is associated with a specified range of angles. The light is projected onto the material surface by a scanning device.The arrangement is such that the angle of reflection is determined irrespective of the point along the scanning line at which the scanned beam strikes the material surface.Various arrangements of different types of photodetector devices are described including a matrix of photodetectors, light conducting rods with photodetectors arranged at their end faces and photomultipliers.The apparatus is particularly suitable for monitoring the production of strip metal in strip mills to detect faults in the metal surface.

Abstract: Optical monitoring apparatus for detecting the angles at which light rays leave a material surface scanned by a light bead such as an incident laser beam includes a row of individual Fresnel lenses arranged edgewise directly adjacent each other to focus light leaving the surface onto respective arrays of photodetectors arranged in their focal planes.The outputs from the photodetectors are connected together by processing means to allow evaluation of their output signals. The row of Fresnel lenses may also be used for other optical monitoring purposes.

Abstract: The flanks of faults present in a surface produce abnormal reflection of a laser beam during linewise scanning of the surface by a laser beam. This apparatus deflects the angles of reflection from the surface, to indicate the presence of a flank, by a light conducting rod arranged parallel to the direction of linewise scanning for receiving reflected light on its surface and for conducting this light to its end face. The various light rays spread out transversely to the direction of scanning during their passage through the light conducting rod and are detected as they pass through a series of concentric annular apertures spaced from the end face of the light conducting rod. Each aperture is associated with a particular range of angles of incidence irrespective of the point on incidence along the surface of the rod and photoelectric detectors are used to sense the light passing through each aperture to provide the necessary indication of the presence or non-presence of a fault.

Abstract: A curve-following device having an optical sensing head which senses a guide zone containing the guide line to be followed and having at least a substantial transverse component, and which is movable along the guide zone at a substantially slower speed than the sensing rate and is connected to a control instrument which forms, from the signals delivered by the sensing head, control signals for the movement of the sensing head along the guide line. Marks associated with the guide line and detectable by the sensing head are detected for tripping further control commmands. At least one separate code zone which is sensed separately from the guide zone is provided at the side of the guide zone.

Abstract: Apparatus for inspecting a web of material for faults or aberrations which affect the remission and reflection of light incident on the material. A first cylindrical lens focuses light scanned over the length of the lens on the material and intercepts light which is remitted by the material. A first light conducting rod is positioned outside the angle of reflection of the light by the material and captures the remitted light. It is disposed on the side of the first cylindrical lens opposite the material so that the remitted light first passes through the first cyclindrical lens. A second cylindrical lens is positioned between the first rod and the first lens for concentrating the remitted light on an envelope region of the first rod. A second light conducting rod captures light reflected by the material and is positioned within the angle of reflection of the light within the angle of reflection of the light by the material.