Abstract: An optical fluid level indicator comprising a light transmitting member having a longitudinal axis, an upper end, and a lower end adapted to extend into a fluid container, the lower end including a first surface having a shape, and a portion projecting downwardly from the first surface and forming a second surface spaced beneath the first surface and having a shape, and a float member having mounted thereon a light reflecting disc and being connected to the lower end of the light transmitting member for movement relative to the light transmitting member in the direction of the longitudinal axis and between a first position wherein the light reflecting disc is adjacent the second surface so that light transmitted to the second surface is reflected by the light reflecting disc, thereby causing appearance at the upper end of the light transmitting member of a light area having the shape of the second surface surrounded by a dark area having the shape of the first surface, and a second position wherein the light

Abstract: A probe is fixed to a vertically displaceable rack. Under the probe is a reference plate freely exposed to snowfall. The probe is periodically lowered toward the reference plate and stopped when it encounters either the plate or a layer of snow which has fallen on the plate. With the aid of a light barrier and a perforated disk, electrical signals dependent upon the distance travelled by the probe are generated and transmitted to an evaluating device. This device calculates, on the basis of the signals received, the difference between the aforementioned distance travelled and the distance from the reference plate to the probe in its uppermost position. This difference corresponds to the thickness of the deposit of snow on the plate. For subsequent measurements, a new reference value corresponding to the surface of the snow already lying on the plate can be used for the calculation. Hence there is no need for clearing the plate of snow after each alarm signal.

Abstract: Method and apparatus for monitoring liquid stock in a storage tank. A prism connected by optical fibers is located at a fixed position in a tank, the volume of liquid at the fixed position being determined. A computer receives data relating to the liquid dispensed, and the liquid received, and calculates an amount of liquid in the tank at the moment the liquid passes the fixed prism. The calculated data is compared to the exact volume data received from the prism.

Abstract: A liquid level sight gauge comprises at least one sight tube 10, 11, a scale 12 mounted adjacent such sight tube(s) and periscope means 13, 15, 16 including a reflective member 17 mounted on an optical carriage 16 movable along the sight tube and scale for viewing liquid levels within the sight tube over a predetermined metering range. Each sight tube, the scale, and the optical carriage are mounted within a substantially closed tubular casing. The sight tubes and scale are illuminated at least at the level of the optical carriage.

Abstract: An opto-electronic position sensing system comprising a series of radiation sources, a series of radiation detectors, a moveable member having a range of movement over which it controls irradiation of various ones of said detectors by various ones of said sources according to the position of said member, each detector being adapted to produce an analog signal which varies from a minimum to a maximum with movement of the said member over a corresponding parts of its range in such a manner that the output signal of at least two of said detectors varies with movement of said member whatever its position in the said range of movement, and first means which determine the position of the member by digital analysis of outputs from the detectors and second means which subsequently better determine the position of the member by analog analysis of output from those detectors identified by the first means as indicating the position of the member.

Abstract: Bubble detecting infusion apparatus for infusing a liquid from a source into a patient through the lumen of a light transmissive conduit member, which lumen has a flat wall surface portion contacted by the liquid in the lumen, the conduit member having an operative position within a yoke in which it is removable disposed, the yoke having a light source for directing a light beam through the conduit member wall toward the flat lumen wall surface portion thereof and having a light sensor positioned to receive light from the source reflected through the conduit member wall by the flat lumen wall surface portion, the angularity between the incident light beam and the normal to the flat lumen wall surface portion being such that when a gas bubble is in contact with the lumen flat wall surface portion, substantially all light from the source incident thereon is reflected by said surface portion toward the light sensor, and when a bubble-free liquid is in contact with the lumen flat wall surface portion, said surfac

Abstract: Motion sensing apparatus comprise a mercury globule supported on an opaque concave surface having a transparent window at its lowest part. A photocell is exposed to light passing through the window as it is varied by movement of the mercury. The photocell output is passed to one terminal of a comparator, the other terminal of which is energized through a variable resistor by means of which the sensitivity of the comparator to the photocell input may be varied. The comparator output controls pulse generating apparatus which produces output pulses of controllable length or, alternatively, an electronically latched continuous output either of which may control mechanism of any kind.

Abstract: Level detection apparatus for determining the depth of a variable surface with respect to the apparatus is disclosed. The device includes a scanning source which causes an intense, collimated beam of light to move across the surface to be detected. First and second spaced detectors sensitive to light reflected from the surface are located at opposite sides of the scanning source and lie in the plane of the scanned beam so that the source directs light from the reflecting surface onto first one and then the other of the detectors. A circuit responsive to the receipt of the reflected beams by the first and second detectors produces first and second signals which will be spaced in time in accordance with the depth of the surface to be measured.

Abstract: A weighing and packaging system operates by combining weight data from a plurality of weighing machines, obtaining a combination of weighing machines giving a total combined weight value equal to a target value or closest to the target value within preset allowable limits, discharging articles from those weighing machines belonging to the combination obtained, and packaging the discharged articles. In performing combinatorial weighing, the articles discharged from the combinatorial weighing machine are temporarily retained in a cylinder, and light-emitting and light-receiving elements are arranged to detect the level of the retained articles, thereby making it possible to detect the volume of the articles charged into a package.

Abstract: A sensing system and method for detecting changes in the level of a liquid surface utilizing a source of essentially monochromatic illumination of narrow beam width for directing an incident beam toward a liquid surface at an oblique angle thereto, and thereby providing a reflected beam therefrom. A beam expander is interposed between the illumination source and the liquid source for increasing the narrow beam width of the incident beam to a beam width substantially greater than the wavelength of disturbances in the liquid surface. A converging lens is mounted transverse to and intercepts a portion of the reflected beam from the liquid surface for focusing that portion of the reflected beam to a centrum. A beam detector is positioned adjacent to the centrum for providing an indication of changes in the level of the liquid surface by detecting corresponding changes in a relative position of the centrum.

Abstract: An automatic fuel shutoff system for preventing fuel flow into a tank being filled when the level of fuel in the tank reaches a predetermined level. This system stops fuel flow when the passage of light from a light transmitter to a light receiver is blocked by the presence of fuel in a detector gap formed near the outlet of a fuel-dispensing nozzle.

Abstract: The specification discloses a method and apparatus for detecting the position of the float in a glass tube flow meter, and determining the distance of said float from a reference line on the glass tube flow meter which is being calibrated. The blockage of an infrared light beam being sent from a transmitter to dual photo receivers, coupled to an optical conditioner circuit, provides an indication of whether float is high, low or in-band in relationship to the desired position, while a float follower, which is movable along the length of the flow tube by a stepper motor which is connected to a pulse encoder, provides through an optical conditioner circuit, an indication of the float position with regard to the reference line on the glass tube. The circuitry also provides for the automatic tracking of the float as its position is changed by the operator.

Abstract: An apparatus for remotely monitoring the color distribution of two materials charged in a treating column by moving a color sensor along a viewing window of the column. The color sensor moving along the viewing window projects a light onto the materials in the treating column and receives the reflected light for conversion into a reception signal. A comparator compares the reception signal with a reference signal representing a standard color of the materials in the column to produce a digital color difference signal. The digital color difference signal is sampled and distributed to indicator lamps in accordance with position signals from the of positions sensing means which senses the passage of the color sensor by each of a plurality position. Thus, the indicator lamps provide a remote display of the color distribution of the materials along the viewing window.

Abstract: Apparatus for filling beverage tanks comprising a liquid manifold and a gas manifold for counter-pressurizing the liquid as it fills the tank. Supply conduits connect the tank with the manifolds. The gas supply conduit contains a coupling device for connection to a fill-height tube on the container. This coupling device includes an optical sensor embodying a prism which reflects light from a light source when the tank has liquid below a predetermined level and directs light onto a photo-conductor. When the liquid reaches a predetermined upper level in the tank and is forced into the coupling device through the fill-height tube, the prism changes its reflective characteristics, and light passes through the prism without reflection. The change in reflective conditions is brought about by the liquid covering adjacent sides of the prism. The photo-conductor correspondingly changes an electrical signal that is utilized to operate a solenoid valve for shutting off the liquid to the tank.

Abstract: A liquid level detecting device, which has a low transmission loss and may be miniaturized, comprising a plurality of optical fibers each composed of a core made of a transparent material and a cladding layer covering the core therewith and made of another transparent material having a lower refractive index than that of the former transparent material forming the core, end portions of the optical fibers being placed in adjacent to each other in either parallel arrangement or that attained by making an acute angle with each other, and a detecting portion which is obtained by heating the adjacent end portions of these optical fibers to fuse one another and shaping into a spherical form due to the surface tension of the fused material.

Abstract: An optical gauge having a laser or other such light source, the beam from which is cyclically directed upon a photo-detector by a rotating plane mirror, the time at which or during which in each revolution of the plane mirror the beam impinges upon the photo-detector being commensurate with a linear parameter of a workpiece upon which the beam is also directed, either constantly, as in the first disclosed embodiment, or cyclically as the beam is moved across the workpiece and occluded thereby during a portion of each rotation of the mirror, as in the second disclosed embodiment. The point on the rotating mirror at which the beam is reflected lies at the focal point of a fixed, parabolic mirror.

Abstract: An arrangement for automatically controlling the dispensing of a beverage such as a frothy milk shake into an open mouth container such as a translucent paper or styrofoam cup. A dispensing station defines a designated position for the cup to be filled, and a dispensing nozzle is positioned above that designated position. A radiation source is positioned above the cup to direct radiation downwardly through the open mouth thereof such that it passes through the side walls of the cup. A radiation detector is positioned adjacent to an exterior wall of the cup at a vertical position thereon at which the cup holds a "full" dispensed quantity of beverage, such that it produces an output signal indicative of the radiation passing through the wall at the full position. The output signal is compared with a given threshold level, and when it falls therebelow, thereby indicating that the dispensed beverage is at the "full" height, the dispensing operation is terminated.

Abstract: Apparatus is disclosed for determining the position of a surface in which radiation from an optical radiant source is applied to the surface and, by means of a lens system, an image of the radiation is produced on a photoelectric receiver. A laser serves as the radiant source, and is aimed at an angle of inclination relative to an optical axis of the lens system at a point of a surface which, by virtue of its temperature, emits visible radiation in the same wavelength range as the Laser. The surface extends approximately perpendicularly of the optical axis and is subject to positional variations along the said optical axis. The beam is directed from the irradiated point to the photoelectric receiver through a narrow-band optical filter of which the pass band includes the laser wavelength.

Abstract: A water level gauge with fault detector comprises a column for containing a level of water with a plurality of light sources on one side of the column and a plurality of detector assemblies on an opposite side of the column. Filters are utilized to project red and green light through the column. Each detector assembly includes a red detector and a green detector with red and green filters respectively. Due to the difference in offset of light beams transversing the column at an oblique angle through water and through air, the green detector is activated by green light when the green and red light passes through the water in the column and the red detector is activated when the light passes through air in the column, that is, above the water level in the column. By a circuit connected to each detector assembly, it is possible to discover the level of water in the column.

Abstract: A generated signal is passed through an elongated signal conveying element positioned preferably perpendicular to the surface of a fluid the level of which is to be measured. The signal is directed from the signal conveying element to a detector element which senses the signal output from the signal conveying element. The signal output detected in an optical embodiment varies logarithmically with the depth of immersion of the signal conveying element into the fluid. A preferred embodiment employs an electromagnetic wave, e.g., light, signal which passes through a light pipe signal conveying element. By nearly matching the light pipe index of refraction with that of the fluid, a predetermined precentage of the wave is lost into the fluid each time the light is reflected further along the pipe.

Abstract: A combine harvester vehicle having threshing, separating and cleaning stages for cut crop material and a tailings return elevator for conveying tailings to one of the stages for recycling, is provided with a tailings monitor including a photodiode for transmitting a radiant energy beam across the path of tailings being conveyed in the elevator, an electrical circuit including a photodetector for deriving digital signals indicative of whether the beam is impinging on the photodetector or is being interrupted by the tailings, and an RC circuit which charges a capacitor through a resistance when the digital signal is present indicating that the beam is interrupted and discharges it when the opposite digital signal is present to thereby develop an average voltage across the capacitor which is an analog of the percentage of time that the beam is interrupted by the tailings being conveyed in the elevator and can be visually displayed on a voltmeter to the combine operator as a measure of tailings volume.

Abstract: An oil-level detector is mounted on the outside face of a glass window in the wall of an oil tank. The detector has two fibre-optic cables which extend within a cavity between the detector and the window. The ends of the cables are mounted one above the other, one cable transmitting a beam of light at an angle .alpha. of 60.degree. to the window, through an oil in the cavity which has a refractive index substantially equal to that of the window glass. The angle .alpha. is greater than the critical angle of glass with air, and less than the critical angle of glass with the oil in the tank. When the window is covered by oil in the tank the light is refracted into the tank. When the oil level falls below the window, the light is reflected to the other cable which is connected to a control unit. The control unit gives a warning a predetermined time after the level has fallen.

Abstract: A liquid level sensing device, particularly useful for apparatus designed to humidify oxygen gas being administered to patients undergoing respiratory therapy is disclosed. The liquid level sensing device detects the liquid level in a canister having an optical probe therein. A bracket, rotatable on a frame of the device, carries a light source and a light sensing member for determining liquid level in the canister in conjunction with the probe. The hinged bracket engaging relation, and it also rotates out of probe-engaging relation and registry with the light probe. When the bracket is out of registry with the light probe, the canister may be removed and replaced. The bracket may be releasably retained out of probe-engaging relation by means of a snap fit structure.

Abstract: A liquid level indicator which includes a plurality of pairs of optical fibers and a common carrier supporting at least an end portion of each fiber. The carrier is formed with an elongated passage into which, in use, liquid flows to a height dependent on the liquid level to be monitored. The end portions of each pair of fibers are separated by the passage and have their axes generally coextensive, while the end portions of adjacent pairs of fibers are spaced apart along the passage. The end surfaces of end portions of each pair of fibers are inclined at an acute angle to the axis of the fibers such that transmission of light from one fiber to the other is substantially prevented if the liquid does not fill the region of the passage between the fibers, while light is transmitted between the fibers if the region of the passage is filled with the liquid.

Abstract: An optical coupling device wherein at least two light conductors are coupled through the intermediary of a transparent block in the shape of a half-ellipsoid on whose foci converge the end sections of the two light conductors. A light beam emerging from one conductor is reflected and transforms itself into a beam converging on the end of the second conductor. A slot permits the introduction of a liquid-crystal attenuating device connected to an alternating voltage source.

Abstract: Fiber optic waveguides exhibiting a blackout phenomenon can be used for temperature sensing. A temperature sensing waveguide can be used in such applications as maintaining a material within a selected temperature range, freeze protection viscosity control of liquids in pipelines, leak detection of cryogenic fluids, fire detection, application of heat-recoverable materials, battery charging, and fluid level detection. Novel waveguides exhibiting blackout at selected temperatures for use in these applications are described.

Abstract: An apparatus for monitoring and indicating the amount of material at a given level in a plurality of hoppers or bins includes a detector for sensing and indicating the build-up of the material on the side walls of the hoppers. A sensor positioned at each hopper senses the amount of material at the given level and generates a pulsed output signal which is accumulated over a predetermined time interval to represent the amount of the material at the given level in the hopper. The value of the accumulated output signal is compared with the values of first and second reference signals to generate "full" and "not full" indications respectively. Typically, the indications are a continuous "not full" light when the hopper is empty, a flashing "not full" light as the hopper is filled, a continuous "full" light when the hopper is full, and a flashing "full" light as the hopper is emptied.

Abstract: An automated pipette employing a device to ensure exact volume pickup and delivery. An optical device senses the presence of a liquid in the tip of the pipette. By intaking the volume past the optical device stream continuity is determined.

Abstract: An apparatus for monitoring the level of material in a plurality of hoppers or bins includes a radiation source and sensor associated with each hopper. Each sensor generates an output signal representing the incidence of radiation passing through the material in the respective hopper. The sensor output signals are supplied to individual sample/hold circuits where they are temporarily stored. A central control circuit cyclically reads the stored signals from the sample/hold circuits and then generates a reset signal to clear the sample/hold circuits. The central control circuit compares the sum of the sensor output signals for each sensor over a predetermined time interval with at least one reference signal representing a predetermined material amount to generate a status signal for each hopper. A plurality of indicator circuits are responsive to respective condition of the status signals for visually and/or audibly indicating to an operator the status of the material level in the associated hopper.

Abstract: Air bubbles in a transparent intravenous solution conduit are detected, regardless of whether the solution is opaque or clear, by directing a light source at the conduit and detecting light shining through the solution with a first light sensor while detecting light reflected from the interior wall of the conduit with a second light sensor. If liquid is present in the conduit, whether clear or opaque, one sensor will see a low light level while the other sees a high level. If air is present, both sensors see a high light level. By EXCLUSIVE-OR'ing the outputs of the two sensors, a logic signal is obtained which is high only when the presence of liquid in the conduit is being detected. Means using two sensor assemblies spaced axially along the conduit, and a counter associated with each, are also provided to allow passage of minor air bubbles, and to provide a backup signal representative of a predetermined volume of air passing either assembly independently of the other.

Abstract: A level measuring device suitable for measuring the level of any substance, advantageously but not necessarily dangerous substances whether due to heat, toxicity or others, with or without anti-oxidization superficial layers, including in mutual cooperation and coordination an intense light source illuminating a limited and restricted area on the surface of the medium whose level is to be measured, a receiver-perceptor processor so arranged that at least part of the optical control axis is at an angle in relation to the incidence optical axis of said light source, therebeing advantageously present one or more regulating means responsive to the ambient light and to possible infrared rays or the like, regulating means responsive to absorption and reflection features of the light by the material of the surface and the medium in which the rays propagate, alarm means and regulation means.

Abstract: The liquid level indicator contains a number of first light fibers, a number of second light fibers, optical lens means interposed between each output end of the first fibers and an associated input end of the second fibers, and light detectors associated with the output ends of the second fibers. The optical lens means has substantially the same index of refraction as the liquid. When the lens means is not immersed into the liquid, it focusses light from the first fiber to the second fiber. This focussing effect is eliminated when the lens is submerged into the liquid.

Abstract: An automatic isolator of blood plasma comprising a photosensor to detect the border between the blood plasma layer and that of the blood cells, which have been separated using a centrifugal machine and stored in a blood bag, and a solenoid to stop the transfer of the blood plasma from the blood bag through a tube, by pinching the tube when the border is detected by the photosensor.

Abstract: A low liquid level electro-optical probe is made self-checking by providing the same with means for intercepting a portion of the usual light beam and constantly reflecting such portion to the usual receiving electro-optical transducer to constantly generate a low level electrical signal even when the probe is wet. Means are provided for boosting the signal to activate an alarm, failure of which will be indicative of failure or malfunctioning of one or more elements of the system.

Abstract: The invention relates to a fiber optical measuring device for measuring physical parameters of a medium, preferably the level thereof, and it comprises an electronic unit and a transducer unit interconnected by an optical fiber, the transducer including at least one light guide connected to the optical fiber. The light guide is adapted to be lowered or introduced into the medium, the level, or other parameters, of which is to be measured, the light guide having a core with a higher refractive index than the surrounding sheath. The sheath has one or more regions along the light guide that are light transparent by being uncovered or only very thinly covered. When the guide is immersed into the medium, it influences the channel such that light in the thinly covered or uncovered regions of the guide is transmitted from the core, which light is representative of the level, or other parameter, of the medium.

Abstract: This invention relates to a method of registering the tophography and height level of the charged mass in a blast furnace. A distance meter for measurement by means of direct reflection against the surface is placed in the vicinity of the top of the blast furnace, appropriately at an inspection window located there. The distance meter is equipped with an aiming device with which the measuring direction of the distance meter is aimable at selected parts of the surface of the charged mass. A computing unit such as a micro- or minicomputer calculates, on the basis of the siting of the distance meter, the set angles of the aiming device for measurement direction and the results of performed distance measurements, calculates the positions for the different measuring points and presents these in analog or digital form.

Abstract: A liquid presence detector having a light-transmissive chamber for the liquid to be detected. A light emitting diode is positioned outside of the chamber for transmitting light through the chamber and a photosensitive transistor is positioned for receiving the light that has been transmitted through the chamber. The light emitting diode is located at a distance from the chamber that is equal to the focal point of a lens that is created by the chamber and liquid when the liquid is present. The photosensitive transistor output voltage is compared with a reference voltage and an output signal is provided in response to a predetermined difference between the detector output voltage and the reference voltage.

Abstract: A U-shaped device wherein the presence or absence of a transparent liquid or solid between the legs of the U is sensed. The device utilizes a collimated light source mounted in one leg of the U with an associated limited field of view sensor in the other leg of the U-shaped device. The light source is placed so as to cause the transmitted light beam to strike the surface of the material to be sensed at an angle which is substantially off of a line perpendicular to the surface of the sensed material.The light sensor is placed so as to receive the light beam when there is no liquid or solid material present between the source and the sensor and to prevent the refractively bent light beam from striking the sensor when a transparent liquid or solid is placed between the light source and sensor.

Abstract: Apparatus for providing an electrical signal when developer material for a copy machine recedes to predetermined level in a container for the material. The apparatus is positioned within the container and includes a light generating means directing light to a light to electric transducer. A cleaning member carried by a rotating arm is included which with rotation of the arm displaces any developer material that is present between the light generating means and the transducer means.

Abstract: An apparatus for detecting the level of a liquid in a container by modulating the intensity of light propagating through a fiber-optic light guide, a section of which has the cladding removed or partially removed. The system consists of a light source which is coupled into the input end of a fiber, a section of fiber from which the cladding is removed, a liquid-containing vessel into which the unclad fiber section can become immersed, and a detector at the output end of the fiber.

Abstract: A process and apparatus for the control of a continuous process for casting metal. The apparatus includes a mold cavity (8) formed by upper and lower movable belts (2 and 3, respectively) and side dams (6 and 7) and including an inlet opening (9). Molten metal (11) is flowed to the inlet opening from a source (14) by conduit (12) connecting with an outlet (13). An opto-electronic device (17, 51) provides a signal which is a function of the level of the molten metal at a zone (FIG. 4) within the mold cavity and a circuit (40) responsive to the signal controls the position of a plug (15) relative to the outlet to control the flow of molten metal. The opto-electronic device includes a photosensitive element (23, 57) whose sensitivity lies essentially to radiation within the visible spectrum and only weakly responsive to infra-red radiation.

Abstract: A photoelectrical bobbin feeler, in particular weft bobbin feeler, comprises one light source and two light sensors, or vice versa, two light sources and one light sensor. At least one polaroid filter is arranged in front of the one light source, or one light sensor, respectively, for polarizing the light which is specularly as well as diffusely reflected from the bobbin, and provides for a safer detection of the "bobbin empty" condition.

Abstract: Leakage of a liquid may be detected in terms of the drop in intensity of light rays traveling through a light guide core or optical fiber made of glass or synthetic resins due to the adhesion of the leaked liquid to the light guide.

Abstract: The invention contemplates instrumentation to enable performance of a plurality of automatic photometric analyses upon liquid samples, as in different analyses of such body fluids as blood, urine, etc. Prior to photometric evaluation, the liquid samples are automatically subjected to controlled doses of one or more reagents, and dwell times, as appropriate to the analysis to be performed at any given time. The particular automatic performance of a given analysis is supplied from an insertably replaceable holder which contains the reagents, dosage devices, and program-control coding unique to the particular analysis. Upon inserted replacement of the holder with another selected holder which is suitably encoded and equipped with reagents, the same instrument will serve for the handling of liquid samples unique to a different biological analysis.

Abstract: A device for detecting the presence of contaminating water in a fuel tank as well as for measuring the density of the fuel in the tank which includes an elongated body of optical material arranged to be mounted in a fuel tank in a vertically extending position, one side face of the body forming an interface with the fluid in the tank, and a plurality of light sensors on the opposite face of the body arranged in spaced-apart relationship, together with light-emitting means at the bottom of the body which emit a divergent group of rays of successively increasing angles of incidence upwardly so that those rays exceeding the critical angle at the interface for a fuel of a specific index of refraction are reflected to illuminate those sensors corresponding to the rays exceeding the critical angle to thereby provide a detected output representing the density of the fluid, the light-emitting means providing a second group of rays striking the lower portion of the interface which are reflected when water is present t

Abstract: An inclinometer is proposed wherein the degree and the orientation of the inclination of an apparatus, such as a vehicle or crane, relative to an artificial horizon can be measured and monitored by means of light barriers. This inclinometer comprises an annular vessel having light-transmissive walls and a hollow ring cover which partially embraces the annular vessel. The inner walls and outer walls of the hollow ring cover are provided with light sources and light receivers which are arranged opposite one another in pairs so as to form light barriers which penetrate the annular vessel and can be interrupted by a liquid contained in such vessel.

Abstract: For measuring the speed of movement of one phase in another, and particularly the rate of sedimentation of corpuscles in blood plasma, a container is filled with a blood sample, a light beam is directed through the container and an image of a vertical plane in the container traversed by the beam is formed in a measuring plane, the light intensity at two vertically spaced regions of the measuring plane is measured, the container is moved until a certain light intensity relationship exists between the two regions, indicating that the image of the boundary of the one phase in the other phase is located between the regions, and after a selected time interval the container is raised until the same light intensity relationship is established between the two regions and the distance through which the container has been raised is indicated.

Abstract: Apparatus and method are disclosed for determining the level of a light-reflecting substance with regard to a reference point. The apparatus and method comprise directing a beam of light at the substance, receiving the diffuse reflected light on an arrangement of photoelectric sensor elements in a manner such that displacement of the reflected light from a predetermined position on the sensor element arrangement is sensed electronically, generating an electrical signal which is proportional to the displacement of the reflected beam from the predetermined position on the element arrangement, and using the electrical signal to determine the amount of deviation of the level of the substance from a predetermined reference point.

Abstract: A liquid level detector for detecting whether a boundary surface between a liquid and a medium rises beyond a prescribed level comprises a rectangular prismatic refractor body formed of a material which only allows the transmission of a light having particular wavelengths and absorbs light having other wavelengths. The refractor body have first and second inclined flat surfaces and a base. The base of the refractor body is provided with a light-emitting element for projecting a beam of light having the particular wavelength and a photoelectric conversion element for converting the light to an electric signal. Each of these element is equidistantly spaced from the center of the base, and the optical axis of each of these elements defines an angle of 45.degree. with each of the inclined surfaces of the refractor body.

Abstract: An indicating device is disclosed for showing the level of a fluid in a container. A transparent rod having a sensing end is immersed in the fluid when the container is filled above a predetermined level. The sensing end is shaped to cause a substantially total reflection of a beam of light projected in the rod from an opposite end of the rod when the sensing end is not in contact with the flowable substance. A light source and photoelectric detector are arranged at the opposite end of the rod and a circuit is connected to the photoelectric detector for detecting when a predetermined amount of reflection occurs and also for preventing response of the device to slopping of the fluid to and fro in the container.