Comparison System For Determining Shape And Intensity Of Illumination Of Luminous Objects

Abstract

A red hot steel strip travels below two elongated photocells disposed in parallel and in a direction perpendicular to the longitudinal axes of the latter. A comparator detects a difference between outputs from both photocells indicating the widths of the strip end portion and provides a signal upon that difference reaching a predetermined magnitude. The signals serves to cut the strip end portion off. One strip sensor is disposed adjacent each photocell to disable the signal during any erroneous system operation.

Description

BACKGROUND OF THE INVENTION

This invention relates to a comparison system for comparing a pair of luminous portions with each other in terms of the shape and/or intensity of illumination.

The invention is particularly in the field of steel rolling techniques. In steel rolling techniques it is generally the practice to perform a hot rolling operation in such a manner that the rough rolling process thereof is continuous to the finishing rolling process. If a leading end of a steel strip has changed in shape during the rough rolling process then such a change in shape of the strip can impose uneven loading on the succeeding finishing rolls leading to damages to the rolls, a failure of the particular rolling operation. In order to avoid these causes of damage it has been the practice that the operator visually monitor a steel strip being rolled and appropriately operate the associated cutting machine to cut off the deformed portion of the strip. It is very desirable to automatically sense any deformed portion of a steel strip being rolled and automatically operate the associated cutting machine to cut the deformed portion of the strip followed by the transfer of the sound strip portion to the succeeding finishing roll mill.

SUMMARY OF THE INVENTION

Accordingly it is a general object of the invention to compare a pair of luminous portions with each other in simple and reliable manner in terms of the shape or intensity of illumination.

It is another object of the invention to provide a new and improved comparison system for comparing a pair of luminous portions with each other in terms of shape or intensity of illumination of one of the portions relative to the other.

It is still another object of the invention to provide a new and improved comparison system for comparing a pair of luminous portions with each other in terms of the shape and also comparing a pair of luminous portions of the same shape with each other in terms of the temperature or intensity of illumination.

It is a special object of the invention to provide a new and improved comparison system for comparing a pair of different portions of a single luminous object such as a leading end portion and a middle portion and/or the latter and a tailing or trailing end portion of a length of a luminous strip, for example, a red hot steel strip being rolled with each other in terms of the shape or intensity of illumination.

It is an additional object of the invention to provide in the comparison systems of the type as described in the preceding paragraphs an improved protective device for sensing any malfunction of the comparison system to disable the latter.

It is still another object of the invention to provide a new and improved comparison system capable of comparing a pair of luminous portions having different intensities of illumination with each other in terms of the shape.

The invention accompanishes these objects by the provision of a comparison system for a luminous object comprising a first photoelectric element, a second photoelectric element, each of the photoelectric elements forming thereupon an image for that portion of the luminous object facing the same to provide an output proportional to at least one of the shape and intensity of illumination of the image and a comparison circuit operatively coupled to the first and second photoelectric elements to detect a difference between the outputs therefrom whereby those portions of the luminous object whose images are formed upon the first and second photoelectric elements are compared with each other in terms of at least one of the shape and intensity of illumination.

Advantageously, the first and second photoelectric elements may be connected to the respective amplifiers one of which is provided with means for varying the gain thereof.

In a preferred embodiment of the invention, the comparison system may comprise a first, a second and a third photoelectric elements successively disposed in a direction in which the luminous object travels, in the named order, each of the photoelectric elements forming thereupon an image for that portion of the luminous object facing the same to provide an output substantially proportional to a selected one of the shape and intensity of illumination of the image. A first object sensor is disposed adjacent the first photoelectric element; a second object sensor is disposed adjacent the third photoelectric element. End detector means operate to detect the lead end portion of the object when the first object sensor is in operation while the second object sensor is inoperative and to detect the trailing end portion of the object when the first object sensor is inoperative while the second object sensor is in operation. Comparison circuit means are provided and operative to compare the outputs from the first and second photoelectric elements with each other for the leading end portion of the object and to compare the outputs from the second and third photoelectric elements for the trailing or tailing end portion of the object.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a block diagram of a comparison system constructed in accordance with the principles of the invention;

FIG. 2 is a graph plotting a light receiving area against a shortcircuited output current for a photocell which may be used with the invention;

FIGS. 3a and b are respectively a schematic perspective and a schematic side elevational view illustrating the application of the invention to a steel rolling process;

FIG. 4 is a block diagram of an embodiment of the invention suitable for use in the arrangement of FIG. 3;

FIG. 5 is a circuit diagram illustrating in more detail the comparison system shown in FIG. 4;

FIG. 6 is a combined block and circuit diagram of a modification of the invention applied to a steel rolling process;

FIG. 7 is a view similar to FIG. 6 but illustrating a modification of the arrangement shown in FIG. 6;

FIG. 8 is a circuit diagram of a scanning device used in the arrangement illustrated in FIG. 6 or 7;

FIG. 9 is a view similar to FIG. 8 but illustrating a modification of the scanning device;

FIG. 10 is a schematic diagram of a circuit for driving the scanning device illustrated in FIG. 9; and

FIG. 11 is a truth table for the flip-flop illustrated in FIG. 10.

Throughout the several Figures like reference numerals designate the identical or corresponding components.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and FIG. 1 in particular, there is illustrated the generic form of the invention. The arrangement illustrated comprises a pair of photoelectric elements 1 and 2 such as photocell having focussed thereon images 3 and 4 of individual luminous objects to be compared and providing the respective output currents in accordance with the areas of the images, and one current detection circuit 5 or 6 connected to each of the photoelectric elements 1 or 2 to detect the output current provided by the latter. The outputs of both current detection circuits 5 and 6 are connected to a comparison circuit 7 where the currents detected by the circuits 5 and 6 are compared with each other to provide an output at an output terminal 8.

The photocell serving as the photoelectric element 1 or 2 has the light receiving area to output current characteristic such as shown in FIG. 2 wherein the axis of abscissas represents logarithmically a light receiving area in square millimeters and the axis of ordinates represents logarithmically a shortcircuited output current in microamperes with the parameter being an intensity of illumination in luxes on the photocell. From FIG. 2 it is seen that the shortcircuited output current from the photocell is directly proportional to both the light receiving area and the intensity of illumination. In other words, the photoelectric elements 1 and 2 each provide an output current in accordance with the area and intensity of illumination of an image of an object focussed thereon. Therefore, if the output currents from the photoelectric elements 1 and 2 are detected by the associated current detection circuits 5 and 6 and then compared with each other by the comparison circuit 7, the output terminal 8 has developed thereat an electric quantity indicating a difference in shape and also a difference in intensity of illumination between the objects to be compared.

While the invention has a variety of its applications it is particularly suitable for use with steel strip roll mills and will now be described in conjunction with such a roll mill.

FIGS. 3a and b show the manner in which the invention is applied to a steel rolling process. In FIG. 3 a red hot steel strip 9 is shown as including its leading end leaving the associated roll mill (not shown) and has just entered into a field of vision of a focussing lens 11. The strip 9 is assumed to be traveling at a predetermined speed in the direction of the arrow shown in FIG. 3a. Light emitted from the leading end of the strip is focussed by the focussing lens 11 as shown at line 10 to form an image 9' upon a comparison apparatus according to the invention designated by the reference numeral 12. The comparison apparatus 12 may preferably take a configuration as shown in FIG. 4.

From FIG. 4 it is seen that a sensor unit SU includes a plurality of elongated photoelectric elements 13, 14, 15, 16 and 17 disposed in spaced parallel relationship with their axes substantially perpendicular to the direction of the traveling strip's image 9' as shown at the arrow in FIG. 4. The photoelectric elements 13, 14 and 15 correspond to the photoelectric elements 1 and 2 as shown in FIG. 1 while the remaining photoelectric elements 16 and 17 are intended to be used for the purpose of sensing the presence of an object which will be described later. It is assumed that the photoelectric elements 13 through 17 are photocells such as previously described in conjunction with FIG. 2 although they may be of any other desired type.

As shown in FIG. 4, the sensor unit SU further includes three hot metal sensors 18, 19 and 20 disposed along the longitudinal axis of the traveling image 9'. That is, within the sensor unit SU the sensors 18 and 19 are located on both sides of the set of the parallel photoelectric elements 13 through 17 and spaced away therefrom while the sensor 20 is located upstream of the sensor 18 with respect to the travel of the strip's image 9' for a purpose which will be apparent hereinafter.

The photoelectric elements 13, 14 and 15 are connected to high gain amplifiers 21, 22 and 23 high in input impedance respectively and the remaining elements 16 and 17 are connected to similar amplifiers 24 and 25 respectively. All the amplifiers 21 through 25 are preferably identical in construction and of the feedback type. The amplifiers 21, 22 and 23 each form the current detection circuit 5 or 6 as shown in FIG. 1.

As the red hot steel strip travels in the direction of the arrow in FIG. 4, the image 9' therefor is first formed on the photoelectric element 15 and then on the photoelectric element 17. Before the photoelectric element 17 receives light from the strip, relay contacts 30 and 32 are arranged to be interconnected under the control of a gate circuit 26 having inputs connected directly to the amplifiers 24 and 25, and the sensors 18 and 19 and through relay contacts 31 and 32 to the amplifiers 21 and also through relay contacts 30 and 32 to the amplifier 23.

A further travel of the strip's image 9' in the upward direction as viewed in FIG. 4 causes the image to fall upon the photoelectric element 14. At that time the image formed on the element 15 or 17 will have its width equal to its steady-state magnitude and therefore does not correspond to the deformed leading end of the strip. Under these circumstances, the output currents from the photoelectric elements 14 and 15 are applied to a comparison circuit 27 through the amplifiers 22 and 23. The circuit 27 corresponds to the comparison circuit 7 as shown in FIG. 1. Since the photoelectric elements 14 and 15 are the photocells, the output currents therefrom are proportional to areas and intensities of illumination of the image portions upon the elements respectively as previously described. Assuming that the steel strip is maintained everywhere at a fixed temperature, the image portions can be considered to have a constant intensity of illumination. Also since the photoelectric elements 14 and 15 are elongated and disposed widthwise of the traveling strip, the outputs from those elements and therefore from the amplifiers 22 and 23 are proportional to the widths of the corresponding portions of the strip.

The output from the amplifier 22 is now applied directly to the comparison circuit 27 and the output from the amplifier 23 is through the now interconnected relay contacts 30 and 32 to the same comparision circuit 27 where both outputs are compared with each other. If the circuit 27 determines if the output from the amplifier 22 is equal to that from the amplifier 23, the same is adapted to supply an operating signal to a time dealy circuit 49 and after a predetermined time delay the signal is applied to a cutting machine 50 disposed downstream of the field of the vision of the comparison apparatus 12 in the strip traveling direction as shown in FIG. 3b. Therefore the cutting machine is operated to cut fully the deformed leading end portion of the red heat strip 9 off.

By properly adjusting the gains of the amplifiers 22 and 23, for example, by setting the gain of the amplifier 23 to 90 percent of the gain of the amplifier 22, the comparison circuit 27 determines the equality of the outputs from the amplifiers 22 and 23 when the width of the image 9' formed on the photoelectric element 14 reaches 90 percent of the width of the image 9' formed on the element 15. Then the cutting machine 50 can be operated on that portion of the strip having its width approximately equal to 90 percent of the steady-state width to remove the deformed leading end portion of the strip from the remaining portion thereof.

The strip continues to travel in the upward direction as viewed in FIG. 4 until the trailing end portion thereof leaves the fields of vision of the photoelectric elements 15 and 17. At that time the photoelectric elements 16 and 17 and the associated amplifiers 24 and 25 cooperate with the gate circuit 26 to sense the presence of the trailing strip end portion in the field of vision of the sensor unit SU. Under these circumstances, the relay contact 32 is connected to the other relay contact 31 rather than to the contact 33 to permit the comparison circuit to compare the outputs from the photoelectric elements 13 and 14 with each other. At the same time another relay contact 35 disconnects from a relay contact 33 and is connected to a relay contact 34 as will be apparent hereinafter.

The process as above described in terms of the leading strip end portion is repeated to cut off the deformed trailing end or portion of the strip. Like the amplifier 23 the amplifier 21 may have its gain equal to 90 percent of the gain of the amplifier 22 in order to remove the deformed trailing end portion of the strip having its width approximately equal to 90 percent of the steady-state width.

The hot metal sensors 18, 19 and 20 are responsive to the presence of a red hot steel strip in the field of vision of the sensor unit SU to close the respective relay contacts (not shown) disposed therein to provide individual signals. These signals along with the outputs from the amplifiers 24 and 25 are utilized by the gate citcuit 26 to determine when the system can be operated on the particular steel strip. That is, the comparision circuit 27 is permitted to provide a signal for cutting the strip only when the sensor unit SU "views" the leading or trailing end portion whereby the cutting machine 50 is prevented from being erroneously operated when that portion of the strip intermediate between both ends is traveling below the sensor unit SU. To this end, the hot metal sensors 18, 19 and 20 are further connected to a malfunction detection circuit 28 along with the output from the gate circuit 26. The detection circuit 28 serves to detect any mulfunction of the system and is connected to a mulfunction prevention circuit 29. The latter circuit 29 has other inputs connected to the gate and comparison circuits 26 and 27 respectively and the amplifier 24, and an output connected to the output terminal 8 as shown in FIG. 1.

The arrangement of FIG. 4 may preferably have a circuit configuration as shown in FIG. 5 wherein like reference numerals designate the components identical or corresponding to those shown in FIG. 4. As shown in FIG. 5, the photoelectric elements or photocells 13 through 17 are connected to the high input impedance amplifiers 21 through 25 respectively. Because of the high gain thereof each of the amplifiers 21 through 25 has its input put at a potential imaginarily or virtually null by means of the associated feedback resistor R suffixed with the reference numeral for the same and its output having developed thereat an electrical signal corresponding to the shortcircuited output current from the associated photoelectric element multipled by the resistance of that feedback resistor. Each of the feedback resistors, for example, the resistor R.sub.13 is connected across a capacitor C such as shown by C.sub.13 for the purpose of preventing the instability of the associated amplifier resulting from a great length of coaxial cable connected to the output of that amplifier. In order to compensate for the differences in sensitivity among the photoelectric elements 13, 14 and 15, the outputs of the amplifiers 21, 22 and 23 are connected to potentiometers 50, 51 and 52 respectively. Therefore by properly adjusting those potentiometers, the presence of strip's images of the same width on the photoelectric elements 13, 14 and 15 permits voltages of the same magnitude to be developed on output leads 79, 80 and 81 to the potentiometers 50, 52 and 51 respectively. The output lead 80 is coupled to an inverter and amplifier 22' having a potentiometer 53 connected to the output and a feedback resistor R.sub.22 ' connected across a movable tap on the potentiometer R.sub.22 ' and the input. The potentiometer 53 serves to determine a ratio of the steady-state strip width to a width of a deformed leading or trailing end portion to be cut off. The output of the amplifier 22' is connected to the comparator 27 in the form of a feedback amplifier through a resistor 61 and the amplifiers 21 and 23 are selectively connected to the comparator 27 through the relay contacts 30, 31 and 32 and a resistor 62 identical in magnitude of resistance to the resistor 61. Amplifiers 24' and 25' are similarly connected to the amplifiers 24 and 25 through resistors 64 and 66 respectively and also selectively connected to the amplifiers 21 and 23 through the abovementioned relay contacts and resistors 63 and 65 for comparison purpose. Zener diodes 67, 68 and 69 are connected across the respective amplifiers 26, 24' and 25' in order to cause the outputs therefrom to range from the Zener voltage to a null voltage.

When the hot metal sensor 18 (not shown in FIG. 5) senses a leading end of a red hot steel strip traveling toward the associated finishing roll mill (not shown), the same closes its contacts 18'. This closure of the contacts 18' causes a base electrode of a transistor 77 to be positively biased through a network 70 through 75 for rejecting noise and preventing the multiple operation as a result of the relay closed relay contacts bouncing. The transistor 77 is then saturated to put a null potential on a lead 82. Namely the lead 82 has a value of logic ZERO. Since the hot metal sensor 19 (not shown in FIG. 5) does not yet view the strip, the associated relay contacts 19' remain open. Therefore the associated lead 83 is maintained at a positive potential or at a value of logic ONE. Under these circumstance, NAND gates 90 and 91 coupled to the leads 82 and 83 respectively supply ZERO and ONE to their output leads 84 and 85 respectively. At that time leads 94 and 95 are at positive ONE and ZERO respectively. The leads 84 and 85 are connected to a setting and a resetting terminal of a flip-flop 92 adapted to be triggered to its set state with a ZERO applied thereto. Under these circumstances, the flip-flop 92 is put in its set state to provide ONE at the output 86. This causes a base of a transistor 93 to be positively biased to saturate the transistor. Therefore a relay winding 87 is energized to connect its contacts 32 and 35 to its contacts 30 and 33 respectively.

As the strip travels its image is formed on the photoelectric element 15 and then on the photoelectric element 17. Both elements 15 and 17 are connected to the associated amplifiers 25 and 23 with opposite polarity and the outputs from those amplifiers are applied to the amplifier or comparator 25' through resistors 66 and 65 respectively, the resistor 66 being smaller in resistance than the resistor 65. If the elements 15 and 17 have formed thereon the strip's images of a common width, the comparator 25 provides a positive signal at the output. Therefore a ZERO state is developed on a lead 88 while a ONE state is developed on a lead 89.

A further movement of the strip causes the photoelectric element 14 to begin to form "view" an image of the deformed leading end portion of the strip whereupon the amplifier 22 starts to provide a negative voltage at the output. The photoelectric element 15 has formed thereon an image of that portion of the strip having already reached the steady-state width. Thus the amplifier 23 has a positive voltage produced at the output. The outputs from the amplifiers 22' and 23 are applied through the respective resistors 61 and 62 to the comparator 27 for comparison.

Since the amplifier 22' is first less in magnitude of output than the amplifier 23, the comparator 27 provides a null output. When the deformed leading end portion of the strip further advances to approach the image's width on the photoelectric element 14 to the steady-state width, until the output from the amplifier 22' exceeds that from the amplifier 23. Thus the comparator 27 provides a positive output. A time point when the output from the comparator 27 changes in polarity depends upon a ratio of voltage division provided by the potentiometer 53. Assuming that this ratio is of .alpha. percent (which has been equal to 90 percent for the arrangement of FIG. 4), the output from the comparator 27 is rendered positive when the width of the strip's image on the photoelectric element 14 reaches .alpha. percent of the steady-state width. This causes the output 100 of a NAND gate to provide ZERO to change an output 101 of a flip-flop from its ONE to ZERO state thereby to turn off a transistor 102. At that time and thereafter a capacitor 105 charges through resistors 103 and 104. If the capacitor 105 is initiated to charge beyond the Zener voltage of a Zener diode 106 a transistor 107 is forwardly biased in the base-to-emitter direction to be saturated with the result that the collector potential thereof drops to a null magnitude. The associated flip-flop is triggered to again put its output 101 in ONE state. From this it will be appreciated that the other output of that flip-flop provides a pulse having a duration equal to a time interval for which the capacitor 105 charges to the Zener voltage of the Zener diode 106. Thus the transistors 102 and 107 and the associated components form a timer.

Since the NAND gate 99 has ONES positive potential applied through the leads 89 and 94 to the inputs as above described, a transistor 109 is saturated so long as the output 108 is maintained in its ONE state. This causes a relay winding connected to the collector of the transistor 109 to be maintained energized to interconnect its contacts 111 and 112. This closure of the contacts 111 and 112 permits an output terminal 115 connected to the contact 112 to be connected to another output terminal 116 through normally closed relay contacts 124 and 125. Both terminals 115 and 116 are connected across a control for the cutting machine such as 50. Thus the interconnection of the terminals 115 and 116 permits that control to be started until the deformed leading strip end portion is cut off.

If the leading end of the deformed portion of the strip is relatively pointed so that the image's width on the photoelectric element 14 does not reach the .alpha. percent of the steady-state width before the strip's image is formed on the photoelectric element 16 then the amplifier 24' is operated through a NAND gate 117 to put the lead 100 in its ZERO state to provide a cutting signal. That is, the output terminals 115 and 116 are interconnected in the manner as above described resulting in cutting off of the deformed leading strip end portion.

When the steel strip further advances and is sensed by the hot metal sensor 19, its relay contacts 19' are closed to saturate a transistor 76 in the similar manner as above described in terms of the hot metal sensor 18. This causes all the leads 94, 95 and 96 to be put in a ZERO state. This ensures that in spite of the output from the comparator 27, the output 108 of the flip-flop is prevented from providing ONE or a cutting signal for the strip. That is, the cutting signal is effectively prevented from being produced for the intermediate portion of the strip.

Then the strip continues to travel and the trailing end thereof leaves the region of the hot metal sensor 18 whereupon the inspection of the trailing strip end portion is initiated. At that time, the hot metal sensor 19 still "views" the strip so that the output lead 84 to the NAND gate 90 provides a ZERO while the leads 95 and 96 each provide a ONE output. Thus the flip-flop 92 produces a ZERO output. Then the transistor 93 is turned off to deenergize the relay winding 87. Therefore, its contact 32 is connected to its contact 31 while its contacts 35 and 34 are interconnected whereby the comparator 27 is now operated to compare a signal indicative of the width of the strip's image on the photoelectric element 14 with a signal indicative of the width of the strip's image on the photoelectric element 13.

The strip further advances until the image of the trailing strip end leaves the photoelectric element 17. This renders the output from the amplifier 25' null to bring the leads 88 and 97 into a ONE state. Further travel of the strip causes the deformed trailing end portion to be focussed upon the photoelectric element 14. The strip's image focussed upon the element 14 gradually decreases in width until the width reaches the .alpha. percent of the steady-state width. At that time, the output from the comparator 26 decreases from a positive to a null magnitude. Therefore, the lead 100 changes from a ONE to a ZERO state to operate the associated flip-flop to provide a ONE at the output 108. At that time, the lead 88 and 95 are held in a ONE state so that a NAND gate 98 provides a ZERO state or output to saturate a transistor 110 leading to the closure of relay contacts 113 and 114. A signal due to this closure of the contacts 113 and 114 is supplied to the control of the cutting machines (not shown in FIG. 5) through terminals 118 and 119 and normally closed relay contacts 126 and 127 resulting in the cutting off of the deformed trailing end portion.

A NAND gate 120 is provided for detecting any failure of the system operation or any mulfunction of the system on the basis of the condition that with a red hot steel strip being sensed by the sensors 18 and 19, the photoelectric elements 16 and 17 each should also sense that strip. If either one of the elements 16 and 17 does not sense a strip when the strip is present below the detector 12 photoelectric elements 16 and 17 and the hot metal sensors 18 and 19 (which is a failure in operation or a mulfunction) then the NAND gate 120 produces a ZERO output at its output lead 121 to bring the associated flip-flop into its set state thereby to saturate transistors 121 and 122 connected to that flip-flop. Therefore the associated relay contacts 124 and 126 disconnect from the cooperating relay contacts 125 and 127 respectively whereby a cutting signal such as above described is prevented from being applied through the terminals 115 and 116 or 117 and 118 to the control for the cutting machine (not shown).

Also any failure of the system operation or any mulfunction of the system is detected on the basis of the condition that with no strip present below the detector elements 16 and 17 and the sensors 18 and 19, or with the hot metal sensors 18 and 19 "viewing" no strip, the photoelectric elements 16 and 17 should also "view" no strip. With no strip present below the detector elements 16 and 17 and the sensors 18 and 19, one of the photoelectric elements 16 or 17 may sense a strip which is also a failure of the system operation or a mulfunction of the system. Under these circumstances, the NAND gate 120 also provides ZERO output. Then the process as above described in the preceding paragraph is repeated to prevent any cutting signal being applied to the control for the cutting machine.

The hot metal sensor 20 serves to determine if a length of red heat steel strip follows the strip now being sensed. In the presence of the succeeding strip the output 121 of the NAND gate 120 is locked in a ONE state ensuring the closures of the contacts 124 and 125' and of the contact 126 and 127. Therefore, the failure detecting is not effected.

It will readily be understood that one set of relay contacts similar to the set of relay contacts 123 and 124 may be provided in order to energize an alarm lamp or buzzer.

While the photoelectric elements 13, 14 and 15 are described as being elongated photocells it is to be understood that they may take another configuration such as shown in FIG. 6 wherein another embodiment of the invention is illustrated. In FIG. 6 a plurality of small photoelectric elements 130a, b, ....., n are disposed in spaced aligned relationship in a direction perpendicular to a strip traveling direction to form a first linear array of photoelectric elements generally designated by the reference numeral 130. A plurality of small photoelectric elements 131a, b, ....., n are similarly disposed to form a second linear array of photoelectric elements generally designated by the reference numeral 131. The first and second arrays 130 and 131 are disposed in substantially parallel relationship and equal in the number of the elements to each other while all the small photoelectric elements are of the same construction and the elements of each array are substantially aligned with the corresponding elements of the other array in the strip traveling direction. If desired, a third linear array of photoelectric elements may be disposed in parallel to and spaced away from the second photoelectric array 131 as in the arrangement of FIG. 4. As in the arrangement of FIG. 4, a pair of photoelectric elements 16 and 17 are shown in FIG. 6 as being disposed on the outsides of both arrays 130 and 131. Only for purpose of illustration it is assumed that the arrays are composed of photocells.

The photoelectric arrays 130 and 131 are connected at the outputs to individual scanners 134 and 135 respectively. Both scanners are of the same construction and only the scanner 134 will now be described in detail with reference to FIG. 8.

In FIG. 8, a plurality of N channel junction type field effect transistors 134a, b, ....., n are shown as being disposed in parallel circuit relationship. These transistors form the scanner 134 and each includes a source electrode connected to a different one of the photoelectric elements 13a, b, ....., n of the first array 130 having the other end connected to ground, a gate electrode connected to each of gate terminals 180a, b, ....., n, are a drain electrode connected to a common output terminal 175.

With the gate terminals 180a, b, ....., n maintained at a negative potential, a series of pulses a, b, ...., n denoted beside the terminals 180a, b, ....., n are squentially applied to the latter sequentially to read out the outputs from the photoelectric elements 130a, b, ....., n of the first array. The outputs are sequentially developed at the common output terminal 175. The outputs from the second array 131 are sequentially supplied to a common output terminal 177 in the same manner through channel junction type field effect transistors 135a, b, ....., n.

The scanner 134 may be realized in a configuration as shown in FIG. 9 wherein like reference numerals designate the components identical to those shown in FIG. 8. The photoelectric elements 130a, b, ....., i whose number is i provide outputs subsequently applied to a common amplifier 181a of negative feedback type through the respective field effect transistors 134a, b, ....., i. In this way each group of i photoelectric elements such as the elements No. (i + 1) through No. 2i are operatively coupled to one amplifier identical to the amplifier 181a. FIG. 9 illustrates only the first amplifier 181a and the jth amplifier 181j. The amplifiers 181 each include a field effect transistor 190a, ....., or j connected across its feedback resistor 192a, ....., or j to amplify the respective input signal only when the associated transistor 190 is in its OFF state. The outputs from the amplifiers 181a, ....., j are applied through the respective semiconductor diodes 193a, ....., 193j to a common feedback amplifier 193 where the outputs are added together. The resulting sum of the outputs is supplied to an output lead 195.

The arrangement as shown in FIG. 9 can scan the number of i .times. j of inputs by having the number of i of driving pulses and the number j of separate driving pulses applied thereto. To this end, one can preferably use a pulse generating circuitry as shown in FIG. 10. A circuit 197-198 for generating a rectangular waveform is coupled to a plurality, in this example, i of flip-flops 195a, b, ...., i. More specifically, the generating circuit is connected to clock terminals T of parallel flip-flops 195a, b, ...., i through a line driver or a NAND gate 199 and to resetting terminals R thereof. The ith flip-flop 195i is connected to a parallel combination of flip-flops 196a, b, ....., j whose number is j, through a line driver or a NAND gate 202. The flip-flops have the truth table as shown in FIG. 11.

In operation a terminal 201 leading to a NAND gate 200 is maintained at a positive potential to cause the NAND gate 200 to provide a null potential thereby to reset the flip-flops 195a through i and 196a through j. In the reset state, the Q terminals of the flip-flops are put at a positive potential while the Q terminals thereof have a null potential. Therefore output terminals operatively associated with the flip-flops are such that the output terminal 181a is at a null potential and the output terminals 181b through i are at a negative potential while the output terminal 191a is put at a negative potential and the output terminals 191b through 191j are maintained at a null potential. It is noted that the output terminal 181a is connected to the gate terminals 180a, 180.sub.i.sub.+1, 180.sub.2i.sub.+1, ... for the transistors 180a, 180.sub.i.sub.+1, 180.sub.2i.sub.+1, ... and the terminal 181i is connected to the gate terminals 180i, 180.sub.2i.sub.+1... therefor while the output terminal 190a is connected to the gate terminals 190a, 190.sub.i.sub.+1, 190.sub.2i.sub.+1... for transistors 192a, 190.sub.2i.sub.+1, 192.sub.2i.sub.+1... and the terminal 191j is connected to the gate terminals 190j, 190.sub.2j, 190.sub.3j,..... In the reset state of the flip-flops, therefore, the transistor 134a is in its ON state while the transistor 192a is in its OFF state. This results in the scanner 134 having hhe output from the photoelectric element 130a read out at the output terminal 175.

When the resetting terminal 201 has changed from its positive to its null potential, the NAND gate 200 provides a positive potential to initial the pulse generating circuit 197-198 to oscillate. The clock signal from that oscillating circuit is applied through the linear driver or NAND gate 199 to the flip-flops 195 at the clock terminals T. When the output voltage from the NAND gate 199 changes from its positive magnitude to zero, the Q terminal of the flip-flop 195a changes from its positive to a null potential while the Q terminal of the flip-flop 195b changes from its null to its positive potential. This causes the potentials at the terminals 181a and b to become negative and null respectively. At that time, the transistor 134b is in its ON state and the transistors 134a, c, ...., n are in their OFF state while the transistor 192a is in its OFF state and the transistors 192b, c, ...., n are in their ON state. This permits the output from the photoelectric element 130b to be read out at the output terminal 175 of the scanner 134. In this way the flip-flops responds to the application of succeeding clock signals thereto to be triggered until the output terminal 181i has a null potential and the terminals 181a through h have a negative potential permitting the photoelectric element 130i to be read out.

Then the next clock signal will arrive at the flip-flops. This causes the potentials at the terminal 181a and 181b through j to be null and negative respectively while at the same the flip-flops 196a and b are triggered. Therefore the terminal 191a changes to a null potential and the terminal 191b changes to a negative potential to turn off the transistor 192b (not shown). This permits the scanner 134 to read out the output from the photoelectric element 130j at its output terminal 175 thereafter after which the process as above described is repeated.

From the foregoing it will be appreciated that the driving circuits of FIG. 10 whose number is i + j can be used to scan (i + j) inputs.

Returning back to FIG. 6, it is assumed that an image 9' for a red hot steel strip travels in the upward direction as viewed in FIG. 6 until it is sensed by the photoelectric element 17. Under the assumed condition, an amplifier 151 connected to the element 17 provides a positive potential to change an output 152 of a NAND gate from a ZERO to a ONE.

The strip's image 9' further travels to be sensed by the second and first photoelectric arrays 131 and 130, the scanners 134 and 135 are operated in the manner as above described to read out ONE outputs from only those photoelectric elements having formed thereon the image portions thereby to provide output waveforms such as designated by the reference numerals 164 and 165 respectively. Those waveforms 164 and 165 are supplied to respective counters 136 and 137 including a common input terminal 168. The terminal 168 has applied thereto a control signal 166 equal in frequency to the signal for driving the scanners in order that the counters 136 and 137 each count the number of pulses provided by the associated scanner 134 or 135 only during the positive portions of the output from that scanner. The counters 136 and 137 are connected to a subtracter 138 where a difference between the counts effected by both counters 136 and 137 is determined after the completion of each scanning operation of both scanner 134 and 135. The difference in count from the subtracter 138 is applied to a comparator 139 at one input where it is compared with a reference width difference supplied to the other input 140. With the deformed leading strip end portion traveling below the photoelectric arrays 130 and 131, the comparator 139 is adapted to provide an output in response to the output from the subtracter 138 below the reference width difference.

As shown in FIG. 6, the outputs from the scanners 134 and 135 are also applied to the respective flip-flops 141 and 143 at the setting terminals. The flip-flops 141 and 143 are responsive to the occurrence of the signals at the outputs of the associated scanners 134 and 135 to be set providing ONE outputs on output leads 142 and 144. The flip-flops 142 and 143 include a common resetting terminal 145 to which is applied a pulse due to a tailing edge of a pulse 167 developed after the completion of each scanning operation. Also applied to a terminal 146 is a pulse due to the leading edge of the pulse 167.

Therefore, at the instant a measured width difference for the particular strip's image has become below the reference with difference, a ZERO signal is developed on a lead 100 to produce a cutting signal through the NAND gate 99 and in the same manner as previously described in conjunction with FIG. 5. The components serving to produce the cutting signal are designated by the same reference numerals for the corresponding components shown in FIG. 5.

After the strip's image 9' has been focussed upon the photoelectric element 16, an amplifier 150 connected thereto provides a positive potential at the output to put leads 152 and 153 in ZERO state. Therefore NAND gates 99 and 98 provide ONE outputs ensuring that relay contacts 111 and 112 and relay contacts 113 and 114 are maintained in their open position even in the presence of a cutting signal on the lead 148. This prevents the control for the cutting machine from being operated. Therefore as in the arrangement of FIG. 5, the system is effectively prevented from being erroenously operated when the intermediate portion of the strip travels below the photoelectric elements 17, 131, 130 and 16.

After an image for the deformed trailing end portion has left the photoelectric element 17 the sensing of that portion is immediately initiated. Under these circumstances the amplifiers 150 and 151 respectively provide a positive and a null output to put the lead 152 and 153 in ZERO and ONE states respectively.

When the trailing end portion is imaged upon the photoelectric arrays 131 and 130, the counter 135 gradually decreases in count as compared with the counter 136 leading to an increase in output from the subtracter 138. For the tailing end the comparator 139 is adapted to provide a signal at the output in response to the output from the subtracter 138 in the excess of the reference width difference. The signal from the comparator 139 serves to produce a cutting signal through the NAND gate 98 and in the same manner as previously described in conjunction with FIG. 5.

Also the outputs from the scanners 134 and 135 may be processed by an arrangement as shown in FIG. 7 wherein like reference numerals designate the components identical or corresponding to those illustrated in FIG. 6. The output from each scanner 134 or 135 is applied to one input to AND gates 171 and 172 having another input connected to a clock terminal 176 applied with clock pulses 166 as above described in conjunction with FIG. 6. Both AND gates 171 and 172 are connected to an OR gate 173 subsequently connected to a counter 174.

As in the arrangement of FIG. 6, the waveform 164 due to the photoelectric array 130 is developed at the output terminal 175 of the scanner 134 and the waveform 165 due to the photoelectric array 131 is developed at the output terminal 177 of the scanner 135. Further the inversions of the waveforms 164 and 165 also appear at the other output terminals 176 and 178 of the scanners 134 and 135 respectively. Under these circumstances, the OR gate 173 permits the clock pulses 166 to be gated therethrough only when the waveform 164 has a positive potential or a ONE value while the waveform 165 has a null potential or a ZERO value and when the waveform 164 has a ZERO value potential while the waveform 165 has a ONE value. In other words, the OR gate 173 provides at the output the clock pulses whose number corresponds to a difference in width between both waveforms. The counter 174 counts the clock pulses passed through the OR gate 174. In other respect the arrangement is identical in both construction and operation to that shown in FIG. 6.

The embodiments disclosed herein can compare a pair of luminous portions in terms of the shape regardless of their temperatures and are very effective for use in steel rolling processes. For example, either of both deformed end portions of the steel strip with a minimum possible length can be cut off from the sound portion of the strip to increase in yield, in addition to preventing uneven loading on the associated finishing roll null and therefore damages to the rolls thereof as previously described.

While the invention has been described in terms of the shape of the steel strip it is to be understood that the same is equally applicable to the comparison of the intensity of illumination thereof.

While the invention has been illustrated and described in conjunction with a few preferred embodiments thereof it is to be understood that various changes and modification may be made without departing from the spirit and scope of the invention. For example, the scanner may be formed of field effect transistors of the type other than the N channel type. Also the invention is equally applicable to non-luminous objects as far as they are reflective to light. In the latter case, an object under comparison may be irradiated by any suitable source of light and reflected rays of light therefrom are compared with each other in the manner as above described. Therefore the term "luminous" used herein and in the appended claims is intended also to include the emission of light due to reflection.

Claims

What we claim is:

1. A comparison system for gaging a luminous body in the form of a travelling strip comprising, a first, second and third elongated photoelectric elements disposed transverse to and sequentially along a path of travel of a travelling luminous strip to be gaged, said photoelectric elements being disposed parallel to each other and spaced from said path of travel and from each other along said path of travel, lens means disposed between said first, second and third photoelectric elements and the path of travel of said travelling strip to form in operation an image of the strip thereon, each of said photoelectric elements having a light-receiving area whose dimensions are sufficient to receive the width of that portion of the strip imaged thereon and producing an output signal proportional to the area of said portion, a first object sensor disposed adjacent said third photoelectric element to sense the presence of the travelling strip below the same and develop an output signal in response to said presence, a second object sensor disposed adjacent said first photoelectric element to sense the presence of the travelling strip below the same and develop an output signal in response to said presence, said first object sensor and said second object sensor being disposed sequentially along said path of travel but spaced therefrom, each of said first and second object sensors comprising a photoelectric element, end detector means responsive to both said first object sensor sensing the presence of the strip and to said second object sensor sensing the absence of the strip to determine the presence of a leading end portion of the strip and responsive to both said first object sensor sensing the absence of the strip and said second object sensor sensing the presence of the strip to determine the presence of a trailing end portion of the strip, and comparison circuit means responsive to the detection of the presence of the leading end portion of the strip senses by said end detector means comparing the output signals from said first and second photoelectric elements and responsive to the detection of the presence of the trailing end portion of the strip sensed by said end detector means and comparing the output signals from said second and third photoelectric elements thereby to develop a signal representative of a measure of a difference in area between those portions of the strip imaged on the two associated photoelectric elements.

2. A comparison system as claimed in claim 1, further comprising a third and fourth object sensors, said third, first, second, and fourth object sensors being disposed sequentially in the path of travel of the strip in the order named and each developing an output signal upon sensing of the presence of said travelling strip, a first inspection circuit receptive of the output signal of said object sensors for inspecting if said first and second object sensors sense the presence of the strip when the presence of the strip is sensed by said third and fourth object sensors and said first inspection circuit developing an output signal in dependence upon the output signals of said object sensors, a second inspection circuit for inspecting if said first and second object sensors do not sense the presence of the strip as sensed by said third and fourth object sensors, and a protective circuit responsive to signal outputs from either of said inspection circuits to disable said comparison circuit means in response to said signal outputs.

3. A comparison system for gaging a travelling luminous object, comprising a pair of first and second arrays of photoelectric elements disposed spaced from and transversely of a path of travel of a travelling object, said photoelectric elements in each of said first and second arrays being equal in number to, aligned, spaced from each other along the path of travel of the object, and aligned parallel with those in the other array; each of said photoelectric elements being capable of having an image of a respective portion of the object viewed thereby, a first scanning circuit for sequentially scanning said photoelectric elements in said first array to take out outputs from said first array photoelectric elements viewing said image portions, a second scanning circuit for sequentially scanning said photoelectric elements in said second array to take out outputs from said second array photoelectric elements viewing said image portions, each of said first and second scanning circuits including a plurality of field effect transistors and a ring counter for driving said field effect transistors, and a counter circuit connected to said first and second scanning circuits to count a difference between outputs from said first and second scanning circuits to provide a measure of the shape of the luminous travelling object.

4. A comparison system for gaging a luminous body comprising, an elongated first photoelectric element disposed transversely relative to and spaced from the path of travel of a luminous body to be gaged, an elongated second photoelectric element disposed spaced from said path of travel transversely to said path of travel, parallel to the first photoelectric element and spaced therefrom along said path of travel, lens means disposed relative to the first and said second photoelectric elements and relative to said path of travel to form in operation an image of a part of said travelling body on one of said photoelectric elements and a separate image of another part of said travelling body on the other of said photoelectric elements, each of said photoelectric elements having a light-receiving area of a dimension sufficient to receive light from the entire width of said travelling body for developing respective electrical output signals, each representative of a corresponding area of the part of said travelling body imaged thereon, enabling means comprising amplifying means receptive of said output signals enabling developing of a difference signal only when a selected difference value exists between said output signals, and a comparison circuit connected to receive the output signals of said enabling means to compare the output signals and develop said difference signal therebetween when said difference exists between the areas of said one part and said another part of said travelling body, whereby said difference signal is representative of the difference in area between the areas of said one part and said other part of said travelling body.

5. A comparison system for gaging a luminous body according to claim 4, in which said enabling means comprising said amplifying means comprises two amplifiers receiving the individual output signals of said photoelectric elements respectively, and means to set a difference in gain in said two amplifiers.

6. A comparison system for gaging a luminous body according to claim 5, in which the output signals of said photoelectric elements comprise voltage divider means dividing the voltage output signal of at least one of said photoelectric elements, and said comparison circuit comprising means comparing an output of said voltage divider means with the output signal of the other photoelectric element to develop said difference signal.