US3562541A

US3562541A - Synchronizing light chopper comprising cylindrical disc with plurality of channels

Info

Publication number: US3562541A
Application number: US740899A
Authority: US
Inventors: Karl F Schroeder
Original assignee: NEOTEC CORP
Current assignee: NEOTEC Corp A CORP OF DE; Pacific Scientific Co; NEOTEC CORP
Priority date: 1968-06-28
Filing date: 1968-06-28
Publication date: 1971-02-09
Anticipated expiration: 1988-02-09

Abstract

A synchronizing light chopper which is rotatable and has a mechanical member in the form of a cylinder with a multiplicity of slots cut therethrough. One of the slots is wider than the others and permits a longer light pulse therein which is used to reset the flip-flop to its initial zero state. Thus, synchronization is ensured in spite of spurious, unwanted trigger pulses.

Description

United States Patent Inventor Karl F. Schroeder Berwyn Heights, Md. Appl. No. 740,899 Filed June 28, 1968 Patented Feb. 9, 1971 Assignee Neotec Corporation a corporation of Delaware SYNCHRONIZING LIGHT CHOPPER COMPRISING CYLINDRICAL DISC WITH PLURALITY OF CHANNELS 4 Claims, 4 Drawing Figs.

U.S. Cl 250/233, l78/7.6 Int. Cl G01d 5/36, H04n 3/02 Field of Search 250/233;

178/7.6 (US & X)

[56] References Cited UNITED STATES PATENTS 2,287,808 6/1942 Lehde 250/233X 2,397,202 3/1946 Potts 250/233X 2,458,334 l/l949 Brosius 250/233X 2,707,524 5/1955 Montgomery 250/233X 3,371,214 2/1968 Berryman 250/233 1,844,508 2/1932 Jenkins 2,139,869 12/1938 Traub 2,185,640 1/1940 Lubcke 2,543,463 2/1951 Malm 3,399,308 8/1968 Taylor Primary Examiner- Robert Segal Attorney-Lane, Aitken, Dunner & Ziems ABSTRACT: A synchronizing light chopper which is rotatable and has a mechanical member in the form of a cylinder with a multiplicity of slots cut therethrough. One of the slots is wider than the others and permits a longer light pulse therein which is used to reset the flip-flop to its initial zero state Thus, synchronization is ensured in spite of spurious, unwanted trigger pulses.

' ATENTEU FEB 9197! SHEET 1 [1F 2 INVENTOR. KARL F. SCHROE'DER BY Cw fig m ATTORNEY 'pmimimasm- I 3562,5541

sum 2 OF 2 w *mw L L L SLOT I SEQTZ s T 3 sL T 4 SLOT I }l REVOLUTION OF CHOPPER WHEEL- FALSE TRIGGER INVENTOR, KARL F. SCHROEDER ATTORNEY SYNCI'IRONIZING LIGHT CHOPPER COMPRISING CYLINDRICAL DISC WITH PLURALITY OF CHANNELS This invention relates to a rotating light chopper which may be used with a colorimeter. The present arrangement includes a system of synchronization by electronic circuitry which will insure correct synchronization each full cycle of rotation, even though unwanted noise pulses may appear in the system.

It is an object of the present invention to provide a servocontrolled positioned system in which the servo always maintains the correct sense, which is the proper positional direction, and seeks its proper null position. Power for the servo is derived from a synchronously demodulated error signal generated by the rotating mechanical member forming a relationship between the rotating member and the synchronizing light chopper that insures correct synchronization each full cycle of rotation.

Another object of the present invention is to provide a rotating synchronized light chopper having an upper section provided with a pulley and a drive belt. The lower part is substantially a cylinder with slots machined across its face. The lower cylinder part functions with a light source and a photocell to provide spaced, light pulses on the latter at predetermined intervals. This mechanical configuration coupled with a particular electronic circuitry provides the present overall system which insures correct synchronization every cycle or one rotation of the composite rotating membersynchronizing chopper.

A further object of the present invention is to provide a synchronizing light chopper which is compact in construction, relatively inexpensive to manufacture and reliably effective for the purposes intended.

The above and other features, objects and advantages of the present invention will be fully understood from the following description considered in connection with the accompanying illustrative drawings in which FIG. 1 is a diagrammatic perspective view of the mechanical construction of the rotatably synchronizing light chopper constructed in accordance with the teachings of my invention.

FIG. 2 is a bottom plan view of the mechanical construction shown in FIG. 1, with the baffle removed.

FIG. 3 is the circuit arrangement for the synchronizing light chopper shown in accordance with the teachings of the present invention.

FIG. 4 is a diagrammatic showing of the wave forms of the circuit illustrated in FIG. 3.

The synchronizing light chopper in the form of a rotating mechanical member is particularly illustrated in FIGS. 1 and 2 of the drawings wherein is shown a common rotatable shaft having a rotatably synchronizing light chopper rigidly mounted thereon and referred to generally by the numeral 12 and having a lower synchronizing section 14 as well as an upper pulley section 16.

The upper pulley section 16 is provided with a sheave l8 and a drive belt 20 for rotating the lower synchronizing section 14 in the direction of the arrow.

The lower synchronizing section 14 is shown in detail in FIG. 2 and constitutes a cylinder or disc having a multiplicity of

slots

1, 2, 3 and 4 machined across the face thereof. It should be noted that more or less slots may be cut into the face of the cylinder within the spirit and scope of the present invention.

Mounted on one side of the lower synchronizing section 14 is a light source in the form of lamp 22. The light beam from lamp 222 projects through a focusing lens 24 and when the slots are aligned with the light beam and lens 24 the light beam passes through the aligned slot to strike another lens 26 which focuses the light beam to impinge upon photocell 28. It should be apparent that as lower section 14 rotates, each of the slots 1-4 are alternately aligned with the light beam projected from lamp 22. Moreover, it should be noted that slot 1 has a different configuration than

slots

2, 3 and 4 in that its entrance and exit areas are cut at an angle relative to slot 3 instead of having its sides being parallel to the aforesaid slot 3. Thus, the

effect of these angular cuts is to widen the passageway of slot 1 relative to the other slots' 2, 3 and-4 respectively. Accordingly, the time the light beam takes to pass through slot 1 will be of longer duration therein than the time it takes to pass through the

slots

2, 3 and 4 respectively The latter slots' allow equally timed amounts of light to strike the photocell 28, and as stated above, all of which are of shorter duration than the light passing through slot 1. The purpose of this difference in construction of slot1 will become more apparent hereinafter.

The synchronization of electronic circuitry as shown in FIG. 3 with the rotating synchronizing light chopper functions as a servo-controlled position system which will insure correct synchronization each full cycle of rotation in spite of spurious noise pulses. The particular novel characteristic of lower cylinder 14, having one slot'that is configured to allowlight to pass through for a longer period of time than the remaining slots, forms a unique signature" generated once each revolution of the lower cylinder section 14 which may be used to reset any electronic circuitry utilized to process error signals derived from the mechanically coupled rotating member forming the light chopper l2.

A baffle 30 is shown in FIG. 1 which prevents excessive stray light from affecting the proper operation of the system. It should be clear that when the synchronizing light chopper 12 rotates light is passed from the lamp 22 to a selected slot, then blocks light passage and there after permits light to pass through another selected slot.

The electronic circuit that insures correct synchronization every cycle or one rotation of the synchronizing light chopper 12 is shown in FIG. 3 in which 63A, 04A and 04B are positive NOR" logic functions, 63B is a negative AND" logic function, FFl is a .I-K flip-flop memory element and Q, isa PNP transitor.

In the circuit illustrated in FIG. 3 the photocell 28 intercepts light fromthe lamp source 22 which is sequentially interrupted and allowed to pass through the slots in the lower section 14 of the synchronizing light chopper 12. This action results in a rapid change of the resistance of photocell 28 from high to low values alternately wherein there is high resistance when light is blocked and low resistance when illuminated. Transistor Q together with the resistors R and R invert the signal and amplify its rise and fall time. This signal at 40 is fed to an input of both G3A and G4A. The action of G3A is to.invert the signal and provide negative-going excursions to alternately trigger the storage flip-flop FF 1 (see wave form W of FIG. 4). By this arrangement the state-of the flip-flop always may be related to one of the slots in the synchronizing light chopper provided the flip-flop receives no undesirable trigger inputs.

The present invention overcomes undesirable trigger input pulses and determines which state the flip-flop initially assumes at the turn-on condition. This is achieved because only one slot, which is slot 1 in this case, has a predetermined configuration which is wider than the other slots thereby ensuring that the light pulse through slot 1 has a longer duration than the light pulses through

slots

2, 3 and 4 respectively. This is clearly seen in wave forms W and W of FIG. 4. In this regard, the wave form W is used to trigger a monostable multivibrator constituted of 64A, G48, condenser C, and resistor R The output signal from circuit D in FIG. 3 along with the output from circuit C is applied to the inputs of G3B. This gate of 033 has a configuration such that when logical Os" are present on both inputs the output goes positive, i.e., the negative AND gate. In the present system this will occur only when slot 1 is present. This is so because the pulse width of the aforesaid monostable multivibrator is chosen to be wider than the pulse widths of

slots

2', 3 and 4 but narrower than the pulse width of slot 1. Thus, an output pulse is generated at the end of slot 1. This pulse E is used to reset the flip-flop to its initial "zero state. It is apparent, therefore, that at least once each cycle of rotation synchronization is ensured in spite of spurious, unwanted trigger pulses such as indicated at F and G in FIG. 3.

While I have shown and described the preferred embodiment of my invention, it will be understood that the latter may be embodied other wise than as herein illustrated or described and that in the illustrated embodiment certain changes in the details of construction and in the arrangement of the parts may be made without departing from the underlying idea or principle of the invention within the scope of the appended claims.

lclaim:

1. A rotating synchronized light chopper comprising a rotatable cylindrical disc having a plurality of channels cut therethrough, one of said channels having a larger width dimension extending in the direction of rotation of said cylindrical disc than the other of said channels and being widened at its entrance and exit areas, said channels being longer in the direction of light travel therethrough than the width dimension of said channel of larger width, a light source on one side of said rotatably cylindrical disc, a photoelectric cell on the opposite side of said cylindrical disc, the light beam from said light source being adapted to alternately project through each of said channels and impinge on said photocell, and associated circuitry for utilizing the pulse projecting-through the channel of larger width to thereby start said circuitry from a predetermined reference and process error signals derived from said rotatable cylindrical disc whereby correct synchronization every single rotation of said light chopper is effected.

2. A rotating synchronized light chopper as set forth in claim 1 further comprising a baffle plate between said rotatable cylindrical disc and said photocell for preventing excess stray light from affecting the proper operation of said photocell. i

3. A rotating synchronizing light chopper as claimed in claim 1 further including an upper pulley section, and a drive belt means for rotating said upper pulley section, said upper pulley section and said rotatable cylindrical disc being secured together.

4. A rotating synchronizing light chopper as set forth in claim 1 further comprising a first lens between said light source and rotatable cylindrical disc and a second lens between said rotatable cylindrical disc and said photoelectrical cell in the path of said light beam for focusing the latter on the active area of said photoelectric cell.

Claims

1. A rotating synchronized light chopper comprising a rotatable cylindrical disc having a plurality of channels cut therethrough, one of said channels having a larger width dimension extending in the direction of rotation of said cylindrical disc than the other of said channels and being widened at its entrance and exit areas, said channels being longer in the direction of light travel therethrough than the width dimension of said channel of larger width, a light source on one side of said rotatably cylindrical disc, a photoelectric cell on the opposite side of said cylindrical disc, the light beam from said light source being adapted to alternately project through each of said channels and impinge on said photocell, and associated circuitry for utilizing the pulse projecting through the channel of larger width to thereby start said circuitry from a predetermined reference and process error signals derived from said rotatable cylindrical disc whereby correct synchronization every single rotation of said light chopper is effected.

2. A rotating synchronized light chopper as set forth in claim 1 further comprising a baffle plate between said rotatable cylindrical disc and said photocell for preventing excess stray light from affecting the proper operation of said photocell.