US3730615A

US3730615A - Image display from continuously moving image carrier

Info

Publication number: US3730615A
Application number: US00105515A
Authority: US
Inventors: J Woodier
Original assignee: Bell and Howell Co
Current assignee: Bell and Howell Co
Priority date: 1971-01-11
Filing date: 1971-01-11
Publication date: 1973-05-01
Anticipated expiration: 1990-05-01
Also published as: CA956158A

Abstract

An apparatus for displaying images of a succession of recordings from a continuously moving carrier operates with an optical compensator of a type being repeatedly advanced and being reset between successive advancements. Each image is displayed by the way of the compensator and the compensator is advanced during the display of each image to compensate for the continuous carrier movement and for sensed movements in the projected images. Resetting of the compensator is initiated by an electrical signal generating device which is coupled to the compensator drive for providing a reset signal upon attainment by the compensator of the predetermined state of advancement.

Description

United States Patent 11 1 Woodier 51 May 1, 1973 IMAGE DISPLAY FROM FOREIGN PATENTS OR APPLICATIONS CONTINUOUSLY MOVING IMAGE 894,292 12 1944 F ..352 I09 CARRIER [75 Inventor: James G. Woodier, Chicago, Ill. Primary Examiner-John M. I-Ioran Assistant Examiner-Monroe H. Hayes [73] Asslgnee. :lell & Howell Company, Chicago, Atmmey LuC P. Benoit [22] Filed: Jan. 11, 1971 [57] ABSTRACT [21] Appl- No.1 105,515 An apparatus for displaying images of a succession of recordings from a continuously moving carrier 52 US. Cl ..352/109 352/105 Operates with an Optical cmpensamr a type being 51 Int. Cl. .0631) 41/10 repeatedly advanced n being reset between Succes- 58] Field of Search ..352/105,109,110 Sive advancements' Each image is displayed by the way of the compensator and the compensator is ad- [56] References Cited vanced during the display of each image to compensate for the continuous carrier movement and for UNITED STATES PATENTS sensed movements in the projected images. Resetting 2 718 549 9/1955 Manke 352/109 X of the compensator is initiated by an electrical signal 3:067:284 12/1962 Baldwint: X generating device which is coupled to the compensa- 2,843,006 7/1958 Tyler ..352 109 tor drive for Providing a reset Signal p attainment 3,539,250 11/1970 Johnston ....352/109 X by the compensator of the predetermined state of ad- 3,544,207 12/1970 John ..352/ I O9 vancement, 2,506,198 5/1950 Charles ....352/IO9 3,459,471 8/1969 Johnston ..352/105 8 Claims, 7 Drawing Figures IMAGE DISPLAY FROM CONTINUOUSLY MOVING IMAGE CARRIER CROSS-REFERENCE TO RELATED APPLICATIONS Subject matter disclosed in the present patent application is disclosed and claimed in the copending patent applications Ser. No. 89,323, filed Nov. 13, 1970, by Ellen B. Lancor, administratrix of Joseph I-lv Lancor, Jr. and by Leonard A. Ferrari, and Ser. No. 105,571, filed Jan. 1 l, 1971, by Dexter P. Cooper, Jr. Both of these copending patent applications are assigned to the same assignee as the subject application.

BACKGROUND OF THE INVENTION 1. Field of the Invention The subject invention relates to optics and, more particularly, to the display of images from a continuously moving image carrier.

2. Description of the Prior Art Around the turn of the Century the pioneering brothers Lumiere proposed a motion picture apparatus with continuously moving film. As say, for instance, be seen from their US. Pat. No. 634,560, issued Oct. 10, 1899, that proposal was to operate a single motion compensator element. A cam, driven in synchronism with the film, advanced the compensator element gradually during the display of each image, and 'reset the compensator element instantaneously preparatory to the display of the next image. In this manner, the compensator element was to maintain each displayed image substantially stationary despite the continuous movement of the film.

Shortcomings of mechanical cams subsequently fostered a search for corresponding electronic means for initiating and controlling the advance and resetting of the compensator element. Employment of electronic means called for the provision of a sensing device which wouldinitiate resetting of the compensator element.

A typical proposal for meeting this need make use of the fact that the timing of the compensator element resettings can to a large extent be determined from the arrival of film sprocket holes or other fiducial markings at a specific location near the frame projection aperture. According to that proposal, the film margin bearing the sprocket holes or fiducial markings is illuminated through a monitoring aperture in the film gate.

A photocell located at the film gate then senses the arrival of sprocket holes or fiducial markings at the monitoring aperture.

While that prior-art proposal generally presents a workable solution, it does have its drawbacks. One of these resides in the fact that space at the film gate is frequently limited, particularly if a small film format is used. Moreover, to avoid interference of the photocell sensing equipment with the image display, and with the image display compensator control, it is necessary that the reset sensor operate in response to a sprocket hole or fiducial marking that belongs to an image other than the image being displayed. This implies the danger that a compensator resetting operation is initiated prior or subsequent to the actual termination of the display of the particular image.

Another prior-art proposal triggers resetting operations by sensing the rotational position of a sprocket which is geared to the motion picture film. Disadvantages of that proposal include the fact that the employed sprocket imposes mechanical wear and tear on the film, and the fact that the state of advancement of the film is not necessarily indicative of the termination of the display of a particular image, since film shrinkage and elongation are practically unavoidable.

A further prior-art proposal initiates resetting operations by having a shutter element temporarily obscure a photocell that senses sprocket hole images which are projected by way of the compensator element to provide for a control of that element during image display operations. The latter proposal presents a workable solution but is limited in its application to situations in which the shutter operation is accurately correlated to the film advance, independently of the compensator element operation, and in which the compensator element control system is capable of operating with the same photocell for compensator control and compensator resetting purposes.

SUMMARY or THE INVENTION The subject invention is concerned with apparatus for displaying images of a succession of recordings from a carrier. From one aspect thereof, the subject invention resides in the improvement comprising the combination of means for substantially continuously advancing the carrier, means for displaying each of the images, including optical compensator means, means for sensing relative movements of each displayed image, means coupled to the compensator means and connected to the image movement sensing means for advancing the compensator means during the display of each image to compensate for the continuous carrier movement, these means for advancing the compensator means including electromechanical compensator drive means coupled to the optical compensator means, and means responsive to the image movement sensing means for energizing the electromechanical compensator drive means to advance the optical compensator means and reduce the sensed image movement, means for providing an electrical signal upon attainment by the compensator means of a predetermined'state of advancement, means for actuating the mentioned signal-providing means, these actuating means comprising means for mechanically coupling the signal-providing means to the electromechanical compensator drive means and means for resetting the compensator means in response to the electricsignal.

From another aspect thereof, the subject invention resides in the improvement comprising the combination of means for substantially continuously advancing the carrier, means for displaying each of the images, including a compensator mirror, means for sensing relative movements of each displayed image, means coupled to the compensator mirror and connected to the image movement sensing means for angularly advancing the compensator mirror during the display of each image to compensate for the continuous carrier movement, the means for advancing said compensator mirror including electromechanical compensator drive means coupled to said compensator mirror and means responsive to said image movement sensing means for energizing said electromechanical compensator drive means to advance said compensator mirror and reduce said sensed image movements signal upon attainment by the compensator mirror of a predetermined state of angular advancement, means for actuating the mentioned signal-providing means, these actuating means comprising means for mechanically coupling the signalproviding means to the compensator mirror, in response to the electric signal.

BRIEF DESCRIPTION OF THE DRAWINGS The subject invention will become more rapidly apparent from the following detailed description of preferred embodiments thereof, illustrated by way of example in the accompanying drawings, in which:

FIG. 1 is a diagrammatic illustration of a non-intermittent or continuous motion picture projector embodying a preferred embodiment of the subject invention;

FIG. 2 is a view along lines II II of FIG. 1;

FIG. 3 is a circuit diagram of a resetting pulse generator and an image motion sensor of the projector of FIG. 1;

FIG. 4 is a circuit diagram of a servo amplifier and mirror drive of the projector of FIG. 1;

FIG. 5 is a top view of a photocell combination that may be employed in the image motion sensor of FIGS. 1 and 3;

FIG. 6 is a side view, partially in section, of a compensator mirror and mirror drive, and of a reset signal generator in accordance with a preferred embodiment of the subject invention, for use in the continuous motion picture projector according to FIGS. 1 to 4; and

FIG. 7 is a partial illustration ofa view along lines VII VII of FIG. 6.

DESCRIPTION OF PREFERRED EMBODIMENTS The subject invention is of broad utility in continuous film motion display systems with resettable motion compensator means, and is not limited in its applicability to any specific system. However, to present the best mode presently contemplated of carrying out this in-.

vention, the preferred embodiments are herein disclosed and illustrated with reference to the above mentioned copending patent application by Joseph H. Lancor, Jr., and Leonard A. Ferrari, which is herewith incorporated by reference herein.

The non-intermittent or continuous motion picture projector 10 shown in FIGS. 1, 2, 3 and 4 has a film gate 12 which may be curved in accordance with wellknown principles rendering the angular rate of film advance equal for different points of the film gate.

A conventional variable speed drive 15 has a capstan 16 which may have a rubber lining 17 that engages the film with the aid ofa nip roller 18. The drive 15, which may comprise a variable-speed electric motor with reduction gear (not shown), is set at any practical speed to advance a motion picture film 13 through the film gate l2 in the direction of an arrow 19 at a substantially continuous or uniform rate (as distinguished from an intermittent film advance). Two guide rollers 20 and 21 assist the movement of the film into and out of the film gate.

In principle, a sprocket drive can be used for advancing the film 13. Where film sprocket holes are employed as control marks, it is, however, preferred that a capstan which does not wear out the sprocket hole areas be used as the powertransmitting device.

The film 13 bears a succession of optically reproducible recordings in the form of transparent images 23 located in image frames 24 and typically representing a filmed scene. The film further has sprocket holes 25 along a. margin 26 thereof. In accordance with known principles, the film gate has a projection aperture 28 whose length is at least equal to twice the height of each image frame 24 plus the height of an interframe space 29, so that the continuous motion compensator 30 is able to handle two full image frames in succession. The width of the projection aperture is sufficient for a projection of the sprocket hole that pertains to each projected image.

Working with projected sprocket holes through which light is transmitted presupposes that the film margin 26 is opaque or black. This typically is, indeed, the case if the film was produced with a reversal development process. If the sprocket hole margin 26 is transparent, a non-reflecting background may be provided behind the margin 26 and light may be projected onto the margin 26. This projected light is reflected by the film in the margin 26, but not by the sprocket holes. Accordingly, instead of sensing luminous sprocket hole images against a dark background, luminous background areas relative to dark sprocket hole images may be sensed in order to determine relative motion of the projected image (see U.S. Pat. No. 3,067,284, by .I.L.E. Baldwin, issued Dec. 4, 1962, and herewith incorporated by reference herein). Alternatively, a transparent margin of the film may be provided with opaque spots which accompany corresponding image frames 24, and which are sensed against luminous background areas.

The film 13 at the projection gate 28 is illuminated by a projector lamp 32 and condensor lens system 33.

The lamp 32, which may have a conventional reflector (not shown), is energized from an electric power source 34 upon closure of a switch 35. A projector lens system 38 projects the illuminated images and sprocket holes by way of the continuous motion compensator 30 onto a conventional back-lighted screen 39. The backlighted screen is shown by way of example, and a frontlighted screen may be used instead.

The compensator 30 has a first-surface mirror 40 which is repeatedly advanceable by motive power applied to a coil 41 through a range of angular motion so as to compensate for the continuous movement of the film 13. The objective of the compensator mirror 40 is to maintain each projected image substantially stationary. Since the projection aperture 28 in the film gate 12 is larger than an image, the screen 39 is provided with an opaque frame 43 which blocks from the view of the observer the projected sprocket holes and also part of images other than the one image that is being projected for viewing at the particular time.

A device 45 is located at the screen for sensing relative movements of each displayed image in a first direction corresponding to the direction 19 of movement of the film 13. The device 45 also senses relative movement of displayed images in a second direction opposite the first direction just mentioned. These movements in a second direction occur, for instance, if the compensator mirror 40 overshoots in its forward motion the advance of the film.

By way of example and as shown in FIG. 5, the motion sensing device may have two

conventional photocells

47 and 48 mounted adjacent to each other. The luminous sprocket hole is projected by way of the compensator mirror 40 onto the light-sensitive parts of the

photocells

47 and 48. Each of the

photocells

47 and 48 produces a cell current which varies as a function of the area of cell illumination.

As shown in the schematic of FIG. 3, the

cells

47 and 48 are connected in parallel and at opposite output signal polarities between two

terminals

50 and 51 of the sensing device 45. The two output signals of the

cells

47 and 48 buck each other, producing a zero net signal across the

terminals

50 and 51 when the photocells 47 v and 48 receive equal portions of a projected sprocket hole 53. In the case of projected luminous sprocket holes, the

cells

47 and 48 produce a zero net signal in response to equal illumination by portions of the projected sprocket hole. In the case of dark sprocket holes projected with a luminous background surrounding each dark hole, the

cells

47 and 48 produce a zero net signal in response to equal illumination by portions of the luminous background above and below the projected sprocket hole.

It may be helpful to note at this juncture that the sensor 45 need not necessarily be located at the screen 39. Rather, the sensor 45, may be positioned closer to the compensator mirror 40 (such as within the projector housing), with a lens (not shown) being provided for imaging the illuminated sprocket hole onto the sensing device 45 after projection thereof by way of the mirror 40.

The projector further includes an amplifier 55 for energizing the compensator coil 41 that moves the mirror 40. In the system shown in the drawings, no routine sawtooth motion is imposed on the compensator mirror 40. Rather, the mirror is only advanced in accordance with the then prevailing demands of the system aiming at a stabilization of displayedimages in a substantially stationary condition.

To illustrate this principle, a dotted line a in FIG. 1 approximately designates aray of light emanating from the center of an image ZS-initially appearing in the aperture 28 of the film gate 12 for projection by the objective 38 and via the compensator mirror 40 onto the screen 39. A dotted line b, on the other hand, approximately designates a ray of light emanating from the center of the same image, after that image has travelled along the film gate 12 to its extreme position in the aperture 28, just before the compensator mirror 40 is reset onto the next succeeding image. The stop plane of the lens 38 is preferably in front of the lens near the mirror 40.

The letter c in FIG. 1' designates a ray of light leading from the compensator mirror 40 to the center of the projected image on the screen 39. To maintain each projected image stationary during the movement of the image center lines from a to b, the mirror has to ad vance during such movement by an angle of magnitude substantially equal tojone-half of the magnitude of the angle between the lines a and b.

To provide for such a mirror advance, the mirror 40 is wide enough to receive and project images of the sprocket holes 25 which are illuminated by the projector lamp 32. Where the mirror 40 operates in substantially collimated light, as is preferably the case, reduction of the mirror size reduces the total light level, but

does not as such suppress passage of the sprocket hole image. As indicated above, each of these projected sprocket hole images impinges on the sensing device 45; one at a time. This device senses relative movements of the projected image. by developing a net error signal in response to movements of the projected sprocket hole images relative to the sensing device 45. This error signal is applied as an input signal to the servo amplifier 55.

The latter input signal causes the amplifier 55 to develop and apply to the compensator coil 41 motive power for angularly moving the compensator mirror in such a sense as to reduce movement of the projected sprocket hole in the named first direction. As is typically the case with practical servo systems of simple design, the mirror 40 will inevitably tend to overshoot in the direction of its advance.

As has been disclosed in the above mentioned Lancor and Ferrari patent application, and as will be more fully mentioned below, a direct-current level may be applied to the servo amplifier 55 in order to provide for a biasing of the mirror 40 in a direction opposite the direction of mirror advance during the display of each image. In this manner, the need for the traditional bias spring at the mirror 40 is obviated. If no mirror bias spring is used, the amplifier 55 does not have to provide a mirror drive current that increases in a saw-tooth fashion to overcome the force of a mirror bias spring as the display of the image progresses. Similarly, if a spring of low spring constant is used for mirror suspension, the servo amplifier 55 still does not have to provide a mirror drive current that rises to as high a magnitude as would be required if the spring had a sufficiently high spring constant to effect an automatic resetting of the mirror 40 between image displays or to act as the sole agency for precluding overshotting of the mirror 40 during image display.

In addition, the amplifier 55 is constructed to develop and apply to the mirror drive coil 41 a decelerating current when a large excursion of the error signal developed by the sensing device 45 indicates the danger of ringing of the servo system. These features are more fully disclosed in the above mentioned copending Lancor and Ferrari patent application. Also, it should be understood that systems which generate sawtooth currents for driving the compensar tor mirror 40 may, if desired, be employed, since the practice of the subject invention is not limited to the illustrated projector system or to systems without bias springs.

The preferred circuit diagrams of FIGS. 3 and 4 will now be considered.

According to FlGS. 3 and 4, the motion sensing device 45 may be connected to the amplifier input terminal 56 through

resistors

60 and 61 and a terminal 62. The resistor 60 is adjustable to render the loop gain variable. A capacitor 63 is connected in parallel to the

resistors

60 and 61. The combination of the

resistors

60 and 61 and capacitor 63 provides an electric damping network.

A preferred amplifier 55 is illustrated in FIG. 4 and comprises an operational amplifier 64 and a complementary emitter follower output stage 65. Those skilled in the art of integrated circuits will recognize that the. operational amplifier 64 is available in monolithic form pensator drive coil 41 is connected to the amplifier output 69. The supply voltage stabilizer with Zener diodes 71 and 72 and filter capacitors 73 and 74 is also conventional.

A direct-current level for biasing the mirror 40 in a direction opposite to the direction of mirror advance during image display is provided by developing a direct current potential with the aid of a potentiometer 108. This potentiometer is connected between the volt and l 5 volt terminals of the current supply. The slidable contact of the potentiometer 108 is connected to a further input A of the servo amplifier 55 or operational amplifier 64. In this manner, an adjustable currentis provided in the drive coil'41 for biasing the compensator mirror 40 in a direction opposite to or against the direction of the mirror advance during image display, or for otherwise biasing the compensator mirror.

During image display, undesired movements are easily reduced by increasing the gain of the amplifier 55. This gain is preferably higher than 100 (one-hundred) and may be in the thousands.

Upon completion of the display of an image, the compensator mirror 40 is angularly reset preparatory to the display of the next image. As disclosed in the above mentioned copending Lancor and Ferrari patent application, timed electric pulse doublets are applied to the compensator coil 41 for resetting the mirror 40 between image displays. If the polarity of the mirror advance driving power is considered positive, then the resetting doublet 80 illustrated in FIG. 3 comprises a negative pulse 81 followed by a positive .pulse 82. The negative pulse 81 angularly drives the mirror 40 backwards at high speed, and the succeeding positive pulse 82 of the doublet prevents an overshooting of the mirror 40 in the reverse direction. This does away with the necessity of a regularly contacted mechanical stop or motion arresting device which has provided its demerits in prior art systems as a fertile source of wear and tear, noise, jitter and other trouble.

According to the subject invention, resetting of the compensator is effected in response to the provision of an electric signal by a signal generating device 85. The signal generating device 85 is coupled to the compensator drive 41 as indicated by the dotted line 86. As will become apparent in the further course of this disclosure, the device 85 provides an electric signal upon attainment by the compensator mirror 40 of a predetermined state of angular advancement. This state of angular advancement is illustrated in FIG. 1 by the dotted line 40 and corresponds to the position to which the mirror 40 has to be advanced in order to completely display images during normal operation of the motion picture projector.

A preferred form of signal generating device is shown in FIGS. 6 and 7, which also illustrate a preferred optical compensator 30 including the compensator mirror 40.

The compensator mirror 40 is mounted by means of a cement on a short tube 112 of non-magnetic material. The mirror drive coil 41 is wound on the tube 112. The tube 112 with drive coil 41 partially extends between pole pieces of a magnetic armature 113 which may be of a conventional permanent-magnet type, having a central core 114 of soft magnetic material and permanent-

magnet pole pieces

115 and 116. The central core 1 14 is mounted on a post 117 of non-magnetic material. Suitable fasteners (not shown) retain the

pole pieces

115 and 116, the central core 114 and the post 117 in position relative to the main body of the armature 113. Mechanical stops 150 and 151 may be provided to avoid contact of the coil 41 or tube 112 with the

pole pieces

115 and 116 and the core 114. In contrast to prior-art stops are so positioned as to be not regularly contacted by the driven compensator part.

Rather, these stops are placed beyond the regular range of the motion of the driven compensator part.

Two

bearings

118 and 119 are coupled to the mirror 40 and tube 112 by cement bonds 120 and mount the compensator mirror 40 for pivotal or angular movement about an axis 122. A mounting blade 123 is fixedly held at one end as shown at 124 and carries at the other end a pivot member 125 which frictionally engages the bearing member 126. Those skilled in the art will recognize that the electrically energized drive'coil 41 with tube 112 and magnetic armature 113 constitutes an electromechanical compensator drive for the compensator mirror 40 which is coupled to the compensator mirror by cement bonds 1 10.

The signal generating device 85 is combined with the bearing 119 in the form of a rotary electric switch 128. The signal generating device 85 including the switch 128 is thus mechanically coupled by cement bonds 1 10 and 120 to the latter electromechanical compensator drive. In the illustrated preferred embodiment, one of the cement bonds 120 mechanically couples the signal generating device 85 including the switch 128 to the compensator mirror 40, and that cement bond 120, as well as a cement bond 110 mechanically couple the signal generating device including the switch 128 to the electromechanical compensator drive including the electric drive coil 40 and tube 112. The rotary switch 128 includes a core 130 of electrically conducting material. The core 130 has an integral radial projection 131 which forms an electrical switch contact. A sleeve 132 of electrically insulating material circumferentially covers the conducting core 130, except for the switch contact 131.

An electrical contact blade 134 has one of its ends 135 fixedly mounted as shown at 136. The other end 138 of the contact blade 135 is in engagement with the insulating sleeve 132 of the rotary switch 128.

The rotary switch 128 is coupled to and actuated by i the compensator advancing coil 41. In the illustrated embodiment, the rotary switch 128 is also coupled to the compensator mirror 40 by a cement bond 120. In this manner, the moving portion of the rotary switch 128, including the

elements

130, 131 and 132, follows the angular movement of the mirror 40. The angular position of the switch contact 131 relative to the contact tip of the blade 134 is such that the movable switch contact 131 engages that contact tip upon attainment of the angular position 40 by the compensator mirror 40. It may be said that the spring contact 131 is at the beginning of a compensating operation displaced from the contact tip of the blade 134 by an angle which corresponds to the angle by which the compensator mirror has to be displaced for a display of a projected image.

The conductive core 130 of the rotary switch 128 is grounded by way of an electrically conducting mirror mounting blade 142 and an electrically conducting pivot member 143 connected to the blade 142 and contacting the core 130, as shown in FIG. 7.

A schematic showing of the rotary switch 128 and the compensator mirror 40 is provided in FIG. 3 to illustrate the signal generating device 85 in conjunction with the reset doublet generator 84. The contact blade 135 remains in engagement with the insulating sleeve 131 of the rotary switch 128 until the compensator mirror 40 has reached its advanced position 40. In consequence, the input terminal 145 of the doublet generator 84 remains insulated from ground until the attainment of the advanced position 40' by the mirror 40.

Upon attainment of the advanced position 40 by the compensator mirror 40, the doublet generator input terminal 145 is grounded by way of the rotary switch contact 131 and contact blade 135 which then move into electrical contact with each other. An electric reset signal of the type shown at 90 in FIG. 3 is thereby provided by the device 85 and applied to the doublet generator 84.

The doublet current generator 84 has a differentiator circuit 91 which produces a spike 92 in response to the input signal 90. A second differentiation spike, that would arise upon separation of the rotary switch contact 131 from the blade 135, is shown in dotted outline, since it is suppressed by the diode in the differentiator 91.

In considering the operation of the circuits of FIG. 3, it is also possible to view the spike 92 as the reset initiation signal. In this case it may be said that the electric power supply (not shown), which is connected between the V terminal and ground in- FIG. 3, provides an electric current. That current charges the capacitor 140 of the differentiator 91 by way of the differentiator 141. The rotary switch 128 selectively conducts that current by way of the switch contact 131 and contact blade 135 when the mirror position 40 has been attained. This discharges the capacitor 140 and produces a reset initiation signal in the form of the spike 92.

The spike 92 drives a monostable or one-shot multivibrator 94 of a conventional type to produce a pulse 95. The pulse 95 is applied to a differentiating network 99 to produce the two oppositely poled spikes 100 shown at the terminal 62. Y

The terminal 62 being connected to the amplifier input 56, the spike signal 100 is applied to the amplifier 55. The amplitudes of the spikes 100 are such as to drive the amplifier 55 into saturation. This is an important feature since it dispenses with the need of a circuit for disconnecting the image movement sensor 45 during mirror resetting operations. In other words, the oppositely poled spikes 100 not only provide for the requesite pulse doublets, but also effect an automatic suspension of the control operation of the image movement sensor 45 during mirror resetting operations.

An arrow 102 adjacent the spike signal 100 symbolically leads to the pulse doublet as it appears at the output 69 of the amplifier 55, and as it is applied to the compensator coil 41 to initiate and timely terminate v the requisite mirror flyback preparatory to a display of the next image. It is thus seen that the device provides an electric signal upon attainment by the compensator mirror 40 of the predetermined state of advancement 40', and that the doublet generator 84 and amplifier 55 thereupon reset the compensator 30 preparatory to the display of the next image. A potentiometer 96 permits the width of the pulse to be adjusted. This, in turn, permits an adjustment of the net energy with which the compensator mirror 40 is reversed.

Upon completion of the mirror resetting, the servo system including the photosensor 45 and amplifier 55 commences to lock in on the sprocket hole image belonging to the next succeeding image 23. Because of its illustrated construction the amplifier 55 is capable of generating decelerating power which is applied to the drive coil 41 to overcome large overshoots of the mirror 40. In general, however, the subject'servo system can be made to operate so well that the above mentioned direct-current level (see potentiometer 108 in FIG. 4) is capable of precluding undue overshoots without the assistance of decelerating currents.

Sincethe compensator drive 41 is not slaved to any routine cam advance or sawtooth-function generator,

the rate of film advance is conveniently varied by varying the speed of the film drive 15. Variable-speed'film drives are well known in the motion picture projector art.

It should be noted that the mirror position 40' is not necessarily the most advanced angular position which the compensator mirror will attain during image display. In practical systems, factors such as electrical delays in the doublet generator 84. and servo amplifier 55, as well as inertia of the mirror 40 and the mirror drive 41, will tend to require the generation of the reset initiation signal 90 at an advanced mirror position 40' which somewhat lags the extreme mirror advance position which the compensator mirror is to attain for image display. Adjustments for optical performance are easily effected in the illustrated preferred embodiment by making the contact spring 134 adjustablerelative to the block 136 so that the instant of electrical contact between the

members

131 and 138 can be varied.

The illustrated rotary switch 128 has a further advantage when used in conjunction witha compensator that does not have a bias spring. As has been explained in the above mentioned Lancor and Ferrari patent application, it is advantageous to operate such a compensator system at a substantially constant tracking error which is proportional to the damping of the driven compensator part. The servo system then advances the compensator mirror 40 with a substantially constant torque in proportion to the damping. This leads to a minimum of jitter in the projected images.

The rotary switch 128 according to a preferred embodiment of the subject invention provides a controllable amount of friction between (a) the moving contact 131 and insulating sleeve 13a and (b) the relatively stationary end portion 138 of the contact spring 134, as well as between the conductive core 130 and the pivot member 143. Since the signal generating device 85 including the rotary switch 128 is coupled to and actuated by the compensator mirror 40, the friction occurring in that switch acts as damping on the movable part of the compensator 30.

Accordingly, the rotary switch 128, in addition to its signal generating function, also acts as a device for instituting the generation of a substantially constant torque for advancing the compensator mirror 40 during image display.

lclaim:

1. In apparatus for displaying images of a succession of recordings from a carrier, the improvement comprising the combination of:

means for substantially continuously advancing said carrier;

means for displaying each of said images, including optical compensator means;

means for sensing relative movements of each displayed image;

means coupled to said compensator means and connected to said image movement sensing means for advancing said compensator means during the dis play of each image to compensate for the continuous carrier movement, said means for advancing said compensator means including electromechanical compensator drive means coupled to said optical compensator means and means responsive to said image movement Sensing means for energizing said electromechanical compensator drive means to advance said optical compensator means and reduce said sensed image movements;

means for providing an electric signal upon attainment by said compensatormeans of a predetermined state of advancement; means for actuating said signal-providing means, said actuating means comprising means for mechanically coupling said signal-providing means to said electromechanical compensator drive means; and means for resetting said compensator means in response to said electric signal.

2. Apparatus as claimed in claim 1, wherein:

said means for actuating said signal-providing means include means for mechanically coupling said signal-providing means to said electromechanical compensator drive means and to said compensator means.

3. Apparatus as claimed in claim 1, wherein:

said signal-providing means include means for providing electric current, and means connected to said current-providing means for selectively conducting said electric current to provide said electric signal upon attainment by the compensator means of said predetermined state of advancement.

4. Apparatus as claimed in claim 1, wherein:

said signal-providing means include means for providing electric current, electric switch means connected to said current-providing means for deriving said electric signal from said currentproviding means upon attainment by the compensator means of said predetermined state of advancement; and

said mechanical coupling means include means for mechanically coupling said electric switch means to said electromechanical compensator drive means.

5. Apparatus as claimed in claim 1, wherein:

said signal-providing means include means for damping said compensator means advance; and

said mechanical coupling means include means for coupling said damping means to said compensator means. 6. In apparatus for displaying images of a succession of recordings from a carrier, the improvement comprising the combination of:

means for substantially continuously advancing said carrier; means for displaying each of said images, including a compensator mirror;

means for sensing relative movements of each displayed image;

means coupled to said compensator mirror and connected to said image movement sensing means for angularly advancing said compensator mirror during the display of each image to compensate for the continuous carrier movement, said means for advancing said compensator mirror including electromechanical compensator drive means coupled to said compensator mirror and means responsive to said image movement sensing means for energizing said electromechanical compensator drive means to advance said compensator mirror and reduce said sensed image movements;

means for providing an electric signal upon attainment by said compensator mirror of a predetermined state of angular advancement;

means for actuating said signal-providing means, said actuating means comprising means for mechanically coupling said signal-providing means to said compensator mirror; and

means for resetting said compensator mirrorin response to saidelectric signal.

7. Apparatus as claimed in claim 6, wherein:

said signal-providing means include means for providing electric current, and rotary switch means connected to said current-providing means for selectively conducting said electric current to provide said electric signal upon attainment by the compensator mirror of said predetermined state of angular advancement; and

said mechanical coupling means include means for mechanically coupling said rotary switch means to said compensator mirror.

8. Apparatus as claimed in claim 6, wherein:

said signal-providing means include means for damping said compensation mirror advance; and I said mechanical coupling means include means for coupling said damping means to said compensator mirror.

Claims

1. In apparatus for displaying images of a succession of recordings from a carrier, the improvement comprising the combination of: means for substantially continuously advancing said carrier; means for displaying each of said images, including optical compensator means; means for sensing relative movements of each displayed image; means coupled to said compensator means and connected to said image movement sensing means for advancing said compensator means during the display of each image to compensate for the continuous carrier movement, said means for advancing said compensator means including electromechanical compensator drive means coupled to said optical compensator means and means responsive to said image movement sensing means for energizing said electromechanical compensator drive means to advance said optical compensator means and reduce saiD sensed image movements; means for providing an electric signal upon attainment by said compensator means of a predetermined state of advancement; means for actuating said signal-providing means, said actuating means comprising means for mechanically coupling said signalproviding means to said electromechanical compensator drive means; and means for resetting said compensator means in response to said electric signal.

2. Apparatus as claimed in claim 1, wherein: said means for actuating said signal-providing means include means for mechanically coupling said signal-providing means to said electromechanical compensator drive means and to said compensator means.

3. Apparatus as claimed in claim 1, wherein: said signal-providing means include means for providing electric current, and means connected to said current-providing means for selectively conducting said electric current to provide said electric signal upon attainment by the compensator means of said predetermined state of advancement.

4. Apparatus as claimed in claim 1, wherein: said signal-providing means include means for providing electric current, electric switch means connected to said current-providing means for deriving said electric signal from said current-providing means upon attainment by the compensator means of said predetermined state of advancement; and said mechanical coupling means include means for mechanically coupling said electric switch means to said electromechanical compensator drive means.

5. Apparatus as claimed in claim 1, wherein: said signal-providing means include means for damping said compensator means advance; and said mechanical coupling means include means for coupling said damping means to said compensator means.

6. In apparatus for displaying images of a succession of recordings from a carrier, the improvement comprising the combination of: means for substantially continuously advancing said carrier; means for displaying each of said images, including a compensator mirror; means for sensing relative movements of each displayed image; means coupled to said compensator mirror and connected to said image movement sensing means for angularly advancing said compensator mirror during the display of each image to compensate for the continuous carrier movement, said means for advancing said compensator mirror including electromechanical compensator drive means coupled to said compensator mirror and means responsive to said image movement sensing means for energizing said electromechanical compensator drive means to advance said compensator mirror and reduce said sensed image movements; means for providing an electric signal upon attainment by said compensator mirror of a predetermined state of angular advancement; means for actuating said signal-providing means, said actuating means comprising means for mechanically coupling said signal-providing means to said compensator mirror; and means for resetting said compensator mirror in response to said electric signal.

7. Apparatus as claimed in claim 6, wherein: said signal-providing means include means for providing electric current, and rotary switch means connected to said current-providing means for selectively conducting said electric current to provide said electric signal upon attainment by the compensator mirror of said predetermined state of angular advancement; and said mechanical coupling means include means for mechanically coupling said rotary switch means to said compensator mirror.

8. Apparatus as claimed in claim 6, wherein: said signal-providing means include means for damping said compensation mirror advance; and said mechanical coupling means include means for coupling said damping means to said compensator mirror.