Abstract: A sheet conveying apparatus includes a tray having a plurality of sheets, a feeder to successively convey sheets stacked on the tray, a controller, and a double-feed sensor to detect double feed when the feeder conveys a plurality of sheets in an overlapping manner. When a double-feed length, which corresponds to a length, in a conveyance direction of the sheet, of a region in which the double feed has been detected by the double-feed sensor, is larger than a predetermined distance, the controller determines that the double feed has occurred. When the double-feed length is smaller than the predetermined distance and a sheet size is smaller than a predetermined size, the controller determines that the double feed has occurred. When the double-feed length is smaller than the predetermined distance and the sheet size is larger than the predetermined size, the controller determines that the double feed has not occurred.

Abstract: A method and an arrangement for detecting and counting articles are disclosed, performing the steps of: providing a detecting station arranged along a passageway for the articles, the detecting station being adapted to establish at least a scanning radiation beam at a cross section of the passageway; passing articles past the detecting station, the detecting station detecting an article upon sensing at least a partial interruption of the scanning radiation beam; and obtaining a count of the detected articles through the passageway, wherein the detecting station include first and second detecting assembly arranged at a predetermined distance from each other along the direction of travel of the articles, which first and second detecting assembly establish a respective scanning radiation beam on a first, respectively second scanning plane at a corresponding cross section of the passageway, and wherein at least a first predetermined reference section of the articles is detected at each scanning plane; a travellin

Abstract: An integrated circuit counter includes a cascaded chain of bit counters, which are collectively configured to count a number of first edges of a counter input signal received at an input thereof and output the count as a counter output signal. The cascaded chain includes at least two bit counters, which are: (i) configured to support both counter and buffer modes of operation, and (ii) responsive to respective bypass control bit signals having values that specify whether a corresponding one of the at least two bit counters is disposed in the counter or buffer mode of operation.

Abstract: The display device according to the present invention comprises a substrate and at least one optical coupler having an optical receiver and an optical transmitter formed on the substrate, wherein the optical transmitter transmits an optical signal to the optical receiver.

Abstract: A seed sensor system determines the position of the seed relative to the seed tube as the seed passes the sensor. The position of the seed as well as the speed of the planter and the position of the seed tube above the planting furrow are used to calculate trajectory of the seed into the furrow from which the seed spacing is predicated. By sensing the seed in both X and Y directions in the seed tube, the sensor is better able to determine multiple seeds as well providing more precision to the seed population.

Abstract: A readout chip for single photon counting has a plurality of N individually working channels each assigned to a respective detector diode. Each channel has a counter designed as a binary counter having a length of M bits and a number of programmable bits. Further, the readout chip has a serial shift register or parallel data input register for entering values for the counter and the programmable bits, and a number of data output shift registers each having a number of K data outputs. Means are provided for selectively multiplexing each of the K data outputs onto a selectable bit of the data output shift register.

Abstract: A radiation device includes a detector connected to a multi-functional radiation identifying and processing application specific integrated circuit. The detector includes a plurality of individual imaging cells, each imaging cell generating a charge in response to incident radiation events and outputting the generated charge at an imaging cell output. The application specific integrated circuit includes a different circuit connected respectively to a corresponding one of the imaging cell outputs, each circuit receiving and processing the generated charge received from the corresponding one imaging cell output. Each circuit includes a preamplifier for generating a voltage or current amplitude in response to the received charge, a counter, and a mode logic configured for setting the counter to perform, selectively, at least two of a) photon counting, b) analog to digital conversion of the one of the voltage amplitude and the current amplitude, and c) timing measurement of incident radiation events.

Abstract: A battery powered transmitter circuit has a LED of a continuously cycling microcomputer transmit a beam of a predetermined number of infrared pulses at predetermined time periods to a sensor of a battery powered receiver circuit. Only a clock circuit of each circuit of the same frequency is continuously powered. The two clock circuits are synchronized each time that the sensor senses the predetermined number of infrared pulses. When an object breaks the beam, the sensor causes a count of the object by a microcomputer of the receiver circuit. The receiver microcomputer is inactivated when the sensor does not sense the predetermined number of infrared pulses during one or more cycles of operation of the receiver microcomputer. There is only one count incremented on a count display after the beam is interrupted until the sensor again senses the predetermined number of infrared pulses.

Abstract: A battery powered transmitter circuit has a LED of a continuously cycling microcomputer transmit a beam of a predetermined number of infrared pulses at predetermined time periods to a sensor of a battery powered receiver circuit. Only a clock circuit of each circuit of the same frequency is continuously powered. The two clock circuits are synchronized each time that the sensor senses the predetermined number of infrared pulses. When an object breaks the beam, the sensor causes a count of the object by a microcomputer of the receiver circuit. The receiver microcomputer is inactivated when the sensor does not sense the predetermined number of infrared pulses during one or more cycles of operation of the receiver microcomputer. There is only one count incremented on a count display after the beam is interrupted until the sensor again senses the predetermined number of infrared pulses.

Abstract: A lite-counting apparatus counts lites in a longitudinal array. During a traversal by the apparatus of a peripheral portion of the array, a beam of radiation is passed from at least one source to at least one detector. Based upon changes in the relative path taken by the beam, the articles may be counted.

Abstract: A proportional counting circuit generates count values for use in variably adjusting gain and exposure time of an image sensor array. The count values are adjusted in proportion to the current count value. This technique allows for fast and accurate adjustment of gain and exposure time without sacrificing the visual performance defined by the contrast difference. At least one break-in signal disables counting in some lower bits when a particular higher bit is asserted and allows the count values to be adjusted by a different increment when the count value reaches a predetermined value by asserting the particular higher bit. Break-out signals are used in less significant bits to disable counting in all lower bits than the bit being disabled by the break-in signal from the more significant bit.

Abstract: A gray code is produced from a minimum of gate logic by making available and monitoring master outputs of master-slave latch pairs, where the latch pairs are arranged to form a cascading chain of toggle flip-flop stages. The least significant bit through one less than the most significant bit in the gray code is supplied by the master latch outputs and the most significant gray code bit is supplied by the slave latch output of the last toggle stage in the chain.

Abstract: A current register unit. A first transistor of a first type, second to sixth transistors of a second type, and first and second capacitors are provided, and an image current signal is stored in the current register unit when a control signal is at a first logic level, and the image current signal is output by the current register unit when the control signal is at a second logic level. An image display device that utilizes the current register unit is also disclosed.

Abstract: Any complicates pulse waveform required depending on the type of CCD, can be generated with a simple circuit configuration. Specifically, any complicated pulse is obtainable by inputting an unlimited number of toggle timings, with no limitation imposed on the number of toggle timings inputted. This is achieved only by inputting different toggle timings sequentially from the exterior, because the toggle timing of toggle circuits (14 to 16) is regulated by shift registers (12a, 12b) of a loop structure and comparators (11a, 11b) connected to the rearmost stage of their respective shift registers (12a, 12b).

Abstract: An improved method for counting irregular or unsymmetrical shaped articles that allows greater precision and provides enhanced features over current counting devices and methods. The method improves upon current devices and methods by providing a more precise volume for each article by using actual cross sectional areas of articles. The improved method also allows the user to count broken or incomplete articles as “partial” volumes. These partial volumes may be added to one another to give a precise total batch volume. The actual cross sectional areas may also be used to allow the user to display three dimensional adaptations of each article counted. Because this information is stored, the articles may be displayed at any time after the articles are scanned. The improved method also allows a user to determine the distance between articles, by using the counting device, and, using this information, adjust the feed rate of the device to an optimum feed rate.

Abstract: A device for counting the number of corrugated articles in a stack of corrugated articles includes a light source for illuminating a multi-article containing surface of the stack of corrugated articles. An electro-optical image capturing camera captures a first visual image frame of a first segment of the multi-article containing surface, and a signal converting means converts the first visual image frame into a first electronic frame signal representative of the first visual image frame. A central processing unit, a frame grabber circuit and software process the first electronic frame signal into a first series of article signals representative of the series of individual articles of the first segment of the multi-article containing surface. The processor also counts the number of individual articles in the first series of article signals.

Abstract: A device and method for quantitative determination of an analyte in a biological sample utilizes a non-transparent support medium for retaining a chromatogenic reaction product with the medium being exposed to a source of light for transmitting therethrough a scattered, uniform response light signal which is collected at a photosensitive device whereby the amount of the analyte is correlated to the intensity of the response light signal. The response light signal may be converted to a time-duration signal proportional to light intensity to facilitate the quantitative determination.

Abstract: A method for counting conveyed workpieces, such as on a variable speed conveyor belt, includes sensing interruptions via an object sensor such as an optical sensor with a light beam, and with a computer, applying a mathematical comparison between duration of interruptions to the light beam path and gaps that separate these interruptions. The comparison determines which interruptions are caused by the passage of conveyed workpieces and which interruptions are caused by the passage of other objects such as components of the conveyor belt. The method described involves the selection of a preset factor used in a ratio comparison between the duration of interruptions to the light beam and the gaps that separate these interruptions such that the computer is able to accurately count objects such as sheets of paper pulled by gripper bars and distinguishing between sheets of paper and gripper bars such that gripper bars and clips are not incorrectly counted as sheets of paper.

Abstract: A compact counting and data storage system includes control circuitry coupled with a detector and input selector to enable monitoring of traffic within a selected area for a selected count interval. The system also includes a readily removable data storage unit.

Abstract: A method and apparatus for counting flat sheets of specularly reflective material juxtaposed in side by side relationship including a source of a parallel, collimated, beam of light adapted for movement to shine on a finite point across sides of a plurality of flat sheets at a shallow, acute angle of incidence relative to the sides of the flat sheets such that the beam of light is specularly reflected from the sides of the flat sheets except at one terminal edge of each side of the flat sheets where the beam of light is diffusely reflected, a sensor for sensing light diffusely reflected from the terminal edge of each of the flat sheets and generating an output signal in response to the intensity of the diffusely reflected light, and a microprocessor receiving the output signal from the sensor and generating a numerical count of the flat sheets over which the beam of light has been moved.

Abstract: A method and apparatus for counting irregularly-shaped articles. A pair of light sources are provided at a sensing plane through which articles to be counted are adapted to pass. Each of the light sources emits a light beam that is at an angle to the other light beam, such as an angle of about 90.degree.. Corresponding solar cells are positioned opposite the respective light sources to receive the light signals as the articles pass through the sensing plane. The light sources are alternately operated and the outputs from the respective light detectors are used to calculate an equivalent volume for the article for comparison with a predetermined article volume range to decide whether to count the article. The method and apparatus permit accurate counts of irregularly shaped articles and are substantially independent of the orientation of the article at the sensing plane.

Abstract: A method and apparatus for counting irregularly-shaped articles. A pair of light sources are provided at a sensing plane through which articles to be counted pass. Each of the light sources emits a light beam that is at an angle to the other light beam, such as an angle of about 90.degree.. Corresponding light sensors are positioned opposite the respective light sources to receive the light signals as the articles pass through the sensing plane. A time division multiplex circuit is provided to alternately operate the light sources, and the outputs from the respective light detectors are summed to provide a unitary signal that is provided to a counter to maintain a count of the number of articles passing through the sensing plane. The system provides combined output signals that are substantially independent of the orientation of the article at the sensing plane.

Abstract: A system for automatically recognizing persons or objects as they move past a selected location and for classifying the persons or objects in accordance with selected criteria. The system includes emitters for emitting beams toward a person or object moving past a selected location to generate reflected beams from the person or object. The included angle of the emitted and reflected beam is a function of the height of the person or object. A detector detects the reflected beams and generates signals representative of the included angle, and thus representative of a time-dependent height profile of the person or object from which the beams are reflected. The person or object is classified according to selected criteria.

Abstract: An apparatus for counting the number of passing persons by stature, wherein a projector for radiating light toward the head of a passing person, a light receiving lens for receiving light reflected from the person's head, and a light position detector are arranged as one set at an upper portion of a gateway or a passageway. The light receiving lens converges reflected light to different light-received positions of the light position detector according to the height of the reflective position. The light position detector outputs electric signals which differ according to the reflected light received at the light-received positions and a counting operation is performed discriminatively for every output of the signals.

Abstract: A counter for counting objects in a stack employs a beam moved by a scan carriage along an edge of the stack. A detector on the carriage determines the position of the portion of the beam reflected by the stack and determines, by optical triangulation techniques, the distance between the source of the beam and the edge of the stack. The resulting signal is used to recognize the presence of objects in the stack and to count them on the basis of this recognition.

Abstract: A system for automatically counting people as they move past a selected location, and for measuring their heights. The system includes emitters for emitting beams toward persons moving past a selected location to generate reflected beams from the person, such that the included angle of the emitted and reflected beams is a function of the person's height. A detector detects the reflected beams and generates signals representative of the included angle, and thus representative of the height of the person. The signals representative of the height of the person are converted to data that may be used for evaluation purposes. The system is particularly adaptable for use in retail stores for determining the number of shopper units in the store during selected time periods and evaluating store performance based, in part, on the conversion of shopper units to actual customers.

Abstract: A can counting machine having an inclined housing into which a collection of beverage cans may be dumped. A rotor in the housing defines elongate openings spaced about its periphery for the singular reception and transport of cans upwardly to a discharge outlet in a backing plate rearward of the rotor. The rotor includes a rim projecting from the rotor for rotation therewith to facilitate lateral can movement into a disk opening. Ejector plates on the backing plate dislodge improperly, endwise inserted cans from the opening to prevent the simultaneous discharge of two cans past a can counting component. A motor circuit is responsive to motor loads resulting from a jammed can to automatically reverse motor and rotor direction. A receptacle support assembly receives a plastic bag and includes a frame member spring biased to maintain the bag in open configuration. A liquid barrier directs residual liquid from the cans to a receptacle. A display unit on the housing indicates a can total.

Abstract: The invention relates to an apparatus for counting objects, which includes a light emitting system intended to form an emission zone, a light receiving system forming a plurality of substantially aligned reception points, a passage between the emission zone and the reception points to allow the conveying of objects to be counted substantially perpendicularly to the alignment of reception points, and a counting system provided to determine the number of conveyed objects as a function of the variations of light received at the reception points, which variations are due to the interpositioning of objects between the emission zone and the reception points.

Abstract: The invention relates to apparatus for accurately counting the number of containerized items by movement of a unitary emitting and sensor of a beam of light over rows and columns of the planar surface platform supporting the containerized items.

Abstract: A first sensor at a first location along a conveyor provides a first signal indicating whether or not a container is present at the first location while a second sensor similarly provides a second signal indicating whether or not a container is present at a second nearby location. The first and second signals are input to a logic circuit which outputs a count pulse only if the the inputs are of a proper form in a proper sequence designed so that dither is ignored. The sensors are diffuse reflection type sensors operating at different frequencies. They are mounted so their sensing axes converge at about a 15 degree angle and the sensor lenses are about 3.5 inches from the point of conveyance. A mounting system allows the sensors to be moved up/down and in/out with respect to the conveyor and maintain a position perpendicular with both the container sidewall and the container flow direction.

Abstract: Apparatus and a method for counting primarily printed copy being advanced along a path in an overlapping manner is arranged to direct two beams of infra-red radiation on to a predetermined region in the path of advancement of the copy. The two beams are distinguishable and are directed from positions respectively upstream and downstream of said region. Two detectors are disposed above said region, to receive radiation from two distincts areas respectively, both within said region, but spaced in the direction of the path of advancement of the copy. Suitable processing of the detector outputs, to determine the gradients of the said areas, allows the generation of a count signal as the leading edge of an object passes through said region.

Abstract: Apparatus, intended primarily for use in an aerodynamic particle sizing system, for generating a pair of closely-spaced, substantially parallel light beams and for determining particle sizes by measuring the times of flight of particles between the two light beams. The apparatus for generating the light beams includes a laser source, an aperture slit for establishing the shape of the beams, a cylindrical lens for focusing the laser beam on the aperture slit, a diffraction grating for converting the beam from the aperture slit into diffracted beams in the zero order lobe and one first order lobe and a transfer lens for directing the diffracted beams as substantially parallel beams.

Abstract: An apparatus for automatically counting stacked sheet-like materials having sheet-to-sheet brightness gradients alternating between positive and negative while simultaneously eliminating problems encountered when the sheet edge reflectance characteristics have combined lambertian and specular reflective natures. Rectification of a pitch matched sensor array's data output combined with a selective disposition of the sensor and illumination optical components relative to the sheet edges to be counted based upon the maximum acceptance angle of the optical system yields the improved count data necessary to achieve accurate counting.

Abstract: An apparatus for counting hangers having a convex surface includes a housing having a central light source carried by the housing for projecting a light beam on the convex surface. A pair of spaced light detectors is positioned on the housing substantially on opposed sides of the central light source, the spaced light detectors detect light reflected from the convex surface. A detecting circuit is connected to the pair of spaced light detectors and detects the sequence of reflected light beams, and then determines whether the detected sequence is a sequence of reflected light beams characteristic of the relative displacement of the housing and the convex surface when the housing or the convex surface is displaced in substantially the direction of the space between the pair of opposed light detectors.

Abstract: According to the invention, each detecting element pair of a wafer detector is constituted by light-emitting and light-receiving elements of transmission-type and is arranged at a position corresponding to a fitting edge portion of one of a plurality of wafers. The number of detecting element pairs is equal to the number of wafers which can be stored in the wafer counter. Light emitted from a light-emitting element to a light-receiving element is kept substantially perpendicular to a surface of a wafer and is shielded when a wafer is engaged in a wafer counter. A change in the amount of light received by the light-receiving element is detected by a signal processor electrically connected to each of the detecting element pairs. The positions and number of a large number of wafers can be accurately and instantaneously detected with an extremely simple structure.

Abstract: The invention includes an apparatus for and method of moving textile articles such as pieces of laundry or the like comprising an enclosed passageway having two opposing open ends, and at least one bend between the two open ends; a vacuum source coupled with one of the two open ends and developing a subatmospheric pressure along the passageway and at the other open end of the passageway to draw textile articles into the other open end and through the passageway to the one open end; and a sensor located at the one bend and sensing textile articles drawn through the passageway. The sensor is coupled with an appropriate counter for accumulating a count of successive textile articles drawn through the passageway. A delay circuit is included between the sensor and the accumulator to inhibit successive detector outputs for a selectable but fixed time period, regardless of the size of the textile articles being passed and counted.

Abstract: The position of the moving mirror (20) in a Fourier-transform infrared spectrometer is monitored with a circuit which has an incremental counter formed of a plurality of cascaded up/down counters (82, 84, and 86) that count the pulses received by a laser detector (42) to yield a relative position count. A microprocessor (100) maintains an absolute position count by reading the counters (82, 84, and 86) and updating its absolute position count at regular intervals. A portion of the circuit is dedicated to discriminating the direction of the moving mirror (20) by gating circuitry connected to the digitized output of the laser detectors (42, 44).

Abstract: In an installation for determining the number of persons inside a monitored room or so-called pass-through, a sensor field is generated by IR-sensors. An evaluation unit uses as discriminating criterion the detection of moving bodies and generates for an entrance control unit a signal, allowing or barring the entrance of a person.

Abstract: A document sensor comprises a source of infrared light directed toward a document and a photocell for reacting to the light as it is reflected from the document. A clock drives the light source to send cyclically recurring light pulses toward the document. The clock source also enables a detector each time that the document light source is switched on. After a predetermined number of successive reflected light pulses have been picked up, a document present signal is given.

Abstract: A ballpoint pen of conventional size and shape has a movable ball point that is pressed upwardly in the direction of the housing of the pen when a mark is made. Means is provided for normally biasing the ballpoint outwardly of the housing. However, when the ballpoint is pressed against a writing surface, the refill cartridge having the ball at the lower end thereof is moved upwardly to close a normally open switch which connects a solar cell array in circuit with an electronic counter that counts each time the switch is closed. Controlled by the counter is a liquid crystal display that visually indicates the total number of counts. A gravity switch is contained in the housing and is actuated to reset or clear the counter in preparation for counting a succeeding group of marks when the pen is inverted.

Abstract: A garment hanger and counting system has cutouts in the hook portion so a counter can count each hanger even when they are side by side. The counter is not affected by garments supported on the hanger. The hanger has cutouts on an open end side of the hook portion and the neck side of sufficient depth so that a counter counts the hangers whichever way they are hung on a hanging bar. The system includes hangers and a hanger counter with a modulated light source converging beam optics to a focal point, a photodetector to produce a signal from each hanger, and an indicator to determine the number of hangers counted.

Abstract: The visually observable information is expressed in quantitive form according to an arrangement wherein there is firstly detected the distribution, size, shape and similar characteristics of objects appearing essentially in one level or plane of the sample and deviating visually from their environment. This detection is carried out by forming an image of the primary physical object on a light sensitive detector using known optic means, such as a microscope, in order to code the random information into a digital form, and thereupon the results of detection, that is the information thus brought into digital form, is transferred for further analysis to a computing and registering unit, such as a special purpose or process computer. Preferably, the detector unit comprises an array or matrix of light sensitive elements, such as photo-transistors.

Abstract: A meter for remote inspection having a wheel assembly which enables a counting number indicating the amount of consumption of a measuring object, such as electric energy, or city water or the like to be remotely inspected in a remote inspection center equipped with computer systems. The wheel assembly comprises a plurality of wheels representing respective decimal columns, a series of pinion wheels for transmitting a driving torque, detecting means for detecting the binary-coded signal of a counting number including four photo-sensor portions, and fixed disk means for mounting the detecting means. A predetermined one of side surfaces of some wheels is composed of ten zones which are uniformly divided and selectively colored by two kinds of colors to provide the binary-coded signal of each order of decimals of the counting number.

Abstract: A method and apparatus for detecting a broken line up yarn, wherein a fine beam is adapted to travel widthwise across a row of line up yarns while it is radiated toward the yarns to cause flickerings which are photoelectrically converted to instantly count the current value for the number of yarns. The current value is compared with a standard threshold value, and if the current value is different from the threshold, an alarm signal is emitted indicating an abnormal condition. The present invention can be used as a broken yarn detecting technique for devices dealing with many line up yarns such as a warp knitting machine, a loom, a warping machine and so on.

Abstract: Continuously printed forms, e.g. checks, are cut from a sheet, sequenced and fed longitudinally and horizontally so that they are overlapped. Trays are moved vertically downwardly and are laterally open so that the overlapped checks are inserted and thereby stacked in the trays. Defective forms can be removed prior to shingling and slip sheets can be inserted to designate locations at which defective forms have been removed.

Abstract: An apparatus for counting substantially cylindrical articles comprises a rotatable elevator cylinder having a circumferential series of compartments for the articles on the inside surface of the cylindrical wall thereof. Means are provided for sensing the presence of an article in each compartment when passing a predetermined position in the rotational path of the compartments, and for sensing the arrival of each compartment to said position, as well as means for making one count in dependence on the sensing of an article in said position.

Abstract: A ballpoint pen of conventional size and shape has a movable ball point that is pressed upwardly in the direction of the housing of the pen when a mark is made. Means is provided for normally biasing the ballpoint outwardly of the housing. However, when the ballpoint is pressed against a writing surface, the refill cartridge having the ball at the lower end thereof is moved upwardly to close a normally open switch which connects a solar cell array in circuit with an electronic counter that counts each time the switch is closed. Controlled by the counter is a liquid crystal display that visually indicates the total number of counts. A second switch is actuated by gravity to reset or clear the counter in preparation for counting a succeeding group of marks.

Abstract: An adjuster can provide a potentiometric type of adjustment with a control generator, a driver and a transducer. The control generator can provide an adjusting signal to the driver. The driver is coupled to the control generator for providing a drive signal in response to the adjusting signal. The transducer has its input coupled to the driver and this input is electrically isolated from its output. This output of the transducer can conduct by a variable amount in response to the adjusting signal, to simulate potentiometric action.

Abstract: A taped parts counter which includes a photosensor system for counting the number of small parts encapsulated and carried by a storage tape. The small parts are contained in the storage tape at pre-determined and equal intervals. The intervals have a space relationship to drive holes in the edge of a storage tape. Movement of the storage tape past a sprocket drives a radiation interrupter wheel on which fins interrupt a radiation source in direct relationship to the parts moving past the sprocket. An electrical signal is generated by a photosensitive device as radiation from the radiation source strikes the photosensitive device. The electrical signals are counted by an electrical counting circuit.

Abstract: Sensors in the infeed and output stackers, under control of the microprocessor, monitor the sheets. The apparatus is started automatically by placing sheets in the infeed. A count of the sheets is developed and displayed as the sheets are fed. When the infeed is empty and the output contains sheets, the count is retained. If sheets are removed from the outfeed, the count is retained and is reset only after more sheets are placed in the input. The same rules obtain for batching. The sensors cooperate with singles, holes and doubles detectors and have their again adjusted depending upon sheet density. Automatic threshold adjustment circuits compensate for dust build-up and component aging. Upon sheet detection, the sensing circuit threshold level is instantaneously shifted to prevent an abrupt change in intensity from the sheet covering the sensor to provide an erroneous indication of the presence of a subsequent sheet or sheets.