WO2000022480A1

WO2000022480A1 - Film projector using independently controlled stepper motors

Info

Publication number: WO2000022480A1
Application number: PCT/US1999/023470
Authority: WO
Inventors: Richard Evan Niccum; David K. Stall
Original assignee: Cfs/Rentec, Inc. Dba Cinema Film Systems
Priority date: 1998-10-14
Filing date: 1999-10-07
Publication date: 2000-04-20
Also published as: AU1105500A

Abstract

In a film projector (200), two or more stepper motor-driven systems are synchronized using a microprocessor (500) which provides speed and synchronization information to the stepper motors (240, 280, 281, 290, 291, 292). The invention is particularly applicable to a professional motion picture film projector (200) in which a film (250) passes through a projector (200) and is driven by a plurality of independently controlled but synchronized stepper motors (240, 280, 281, 290, 292). By independently controlling the stepper motors (240, 280, 281, 290, 292), the invention is not only able to control the speed at which the film (250) is progressed, but it is also able to control the various loop (251, 252) sizes and shutter speeds necessary to adjust the projector (200) while it is in operation.

Description

FILM PROJECTOR USING INDEPENDENTLY CONTROLLED STEPPER

MOTORS

Field of the Invention The invention relates to a motion picture film projector having a plurality of stepper motors used to independently power each of the film drive elements wherein the speed of each stepper motor is electronically controlled by a microprocessor control module and can be driven at different speeds independently of the other stepper motors.

Background of the Invention Motion picture projectors are used to exhibit films of a variety of sizes and speeds. The most common film size is 35 mm wide and it is usually advanced at a standard 24 frames per second (fps). Each frame typically contains four frame perforations that run along either side of the film. These perforations are engaged by sprockets attached to the film drive elements that progress the film though the projector system. The standard motion picture film projector has changed little since 1920. The major components of a conventional motion picture projector are:

(1) a spool on which film is stored; (2) an unspooling drive; (3) a device for providing an intermittent motion to the picture gate at a minimum of 16 fps; (4) a picture gate and aperture; (5) a sound scanning and amplifying system; (6) a spooling drive; (7) a lamphouse and lamp to project the illumination onto a screen; and (8) an electric motor. Conventional professional theater projectors are powered by a single electric motor which drives all of the moving parts of the projector through any number of different combinations of gears, sprockets and belts. To prevent failure, the gears, sprockets and belts must be precisely engineered so that each film drive element is advanced at exactly the same speed. These interlocking power transmission systems must also be periodically adjusted in order for the relative speeds to remain perfectly synchronized.

Figure 1 shows a diagram of a conventional projector 100 which uses a single electric motor 160 to drive the entire mechanical operation of the projector 100 through a series of belts 125, 135, 145, 155, 185, 195. From the film feed apparatus (not shown), the film 150 is fed to an upper film drive sprocket 120. The film 150 is then slightly "looped" 151 to allow for the speed differential between the intermittent film pulldown sprocket 180 and the constant speed upper film drive sprocket 120. The loop 151 preferably consists of approximately four frames of film, each frame having four perforations. The film 150 is then fed between the viewing aperture 161 and the shutter assembly 110 for projection. The film 150 is then engaged by the intermittent film pulldown sprocket 180, which intermittently drives the film one frame at a time for illumination. The intermittent film pulldown sprocket 180 advances the film extremely quickly through a "Geneva" (not shown) or other mechanism capable of imparting rapid intermittent motion to the film 150. The film 150 is then briefly held in a stationary position as the shutter assembly 110 allows the film 150 to be projected upon a screen. At the end of the hold period, the film 150 is again advanced extremely quickly so that the next frame is pulled into position for projection.

The shutter assembly 110 consists of one or two circular shutters 111, 112 each having openings therein. In a single shutter model (not shown), the shutter is rotated so that the opening of the shutter passes before the film 150 while the film 150 is in the rest position, thereby allowing the light to pass through the film and shutter opening and onto the screen. The shutter assembly 110 is synchronized with the intermittent film pulldown sprocket 180 so that light from the lamp (not shown) is allowed to pass through the opening of the shutter only while the film 150 is in the hold position. When the film 150 is being advanced by the intermittent film pulldown sprocket 180, the opaque portion of the shutter prevents any light from passing through the film and onto the screen. The shutter and film advancement is performed so rapidly that it is impossible for the human eye to detect the fact that the screen is illuminated only intermittently.

Many projectors use the dual shutter system 110 to intermittently pass and block the light falling onto the film 150. Each circular shutter 111, 112 typically contains two openings (not shown) that comprise approximately 50% of the total shutter area. The shutters 111, 112 are rotated in opposite directions by a pair of actuators 120, 130 powered by the electric motor 160 and are timed so that the openings coincide with the film 150 while the film 150 is in the "hold" position. A two shutter system 110 is often used because the light is passed through the openings of both shutters and is blocked twice as fast as when using a single shutter. Rather than close the opening from only one side in a "swipe", the opening is closed from both the top and the bottom as the shutters 111, 112 rotate in opposite directions. This allows the light "open" time and

"close" time to be shortened and increases the overall amount of light present on the screen, thereby resulting in a brighter picture.

From the intermittent film pulldown sprocket 180, the film 150 is again looped 152 to allow for the speed differential between the intermittent film pulldown sprocket 180 and the constant speed lower film drive sprocket 190. The loop size at the lower film drive sprocket 190 is preferably also four frames. From the lower film drive sprocket 190, the film 150 is passed over the sound head 175 and the sound capstan 170 and is engaged by the sound sprocket 140. The film 150 is finally passed from the sound sprocket 140 to the film storage means (not shown). Each sprocket and drive mechanism on the conventional projector is driven by a single electric drive motor 160. All film drive mechanisms are attached to this electric drive motor 160 through a combination of belts 125, 135, 145, 155, 185, 195 or gears (not shown). The film drive sprockets 120, 180, 190, 140 and the shutter assembly 110 are driven from this single electric motor 160. Speed differences are achieved using different gear/belt ratios. The periodic movement of the intermittent film pulldown sprocket 160 is achieved using a mechanism well known in the art such as the "Geneva" mechanism or a "Maltese Cross" (not shown). However, the intermittent film pulldown sprocket 180 is also driven by the single electric motor 160. Because the prior film projection systems rely upon a single motor and an intricate combination of the belts 125, 135, 145, 155, 185, 195 and/or gears (not shown) to drive the various moving components, they are difficult to repair, maintain, and adjust. All adjustments or repairs must be performed by a skilled technician familiar with belt and gear assembly and replacement. In addition, each part must be carefully machined so that the gear/belt ratios for each component are identical. There is therefore a need for a motion picture film projector that is easy to operate, calibrate and repair.

Summary of the Invention The present invention contains a plurality of stepper motors that are individually electronically controlled by a microprocessor so that the use of timing gears and belts is often unnecessary to synchronize the various film drive components. Another aspect of the present invention is a projector that does not require mechanical gears or belts to operate the intermittent shutter modules in exact synchronization with both one another and with the other film drive components. The invention is also capable of electronically adjusting the timing of the shutter assembly during the projector's operation to improve the projection brightness and film clarity and to eliminate the need for costly and time consuming manual adjustment.

Another aspect of the present invention is a projector having independent stepper motors that are capable, upon proper programming of a microprocessor controller, of adjusting the relative speeds of the stepper motors in order to adjust the film loop size during operation of the projector. Because each of the stepper motors is independently controlled by a single microprocessor, the invention allows the operator to adjust the film loop size while the projector is running.

Another aspect of the present invention is to provide a projector operator with the ability to slow down each of the stepper motors in order to allow the film projector to test the film threading at less than full operating speed. Generally, a film projector must be threaded at normal operating speeds. However, because each stepper motor of the invention is independently controlled by a microprocessor, the microprocessor can be directed to operate the stepper motors at a lower speed while the film is threaded into the machine. This results in fewer misthreading errors and avoids film damage.

The present invention has the additional ability to adjust the frame speed. Because each of the stepper motors is independently controlled by a microprocessor, the microprocessor can be directed to increase or decrease the overall film progression speed, as desired by an operator without the need to change the entire gear belt transmission system of the projector. This facilitates the upgrading of the projector and allows the projector to be used in many ways not possible with single motor projectors, such as projecting films recorded in a variety of different speeds and formats.

Another aspect of the present invention is a projector film drive assembly having six discrete modules: 1) a film drive module; 2) an intermittent module; 3) a shutter module; 4) a microprocessor; 5) a power supply; and (6) a control module. Because the invention utilizes six individually controlled stepper motors, and one control module each of these modules can be easily replaced without the need for extensive dismantling of the gear/belt system thereby allowing repairs to be made quickly and easily.

Another aspect of the present invention is a motion picture film projector that provides feedback to the microprocessor control module. The speed of each of the stepper motors of the invention is fed back to the microprocessor through a sensor. The invention thereby enables each motor to provide feedback to the microprocessor in order to halt the projector to reduce projector and film damage in the event of a failure of one of the components. These feedback indicators also display the cause of a failure should one occur.

Brief Description of the Drawings

Figure 1 illustrates a prior art motion picture projector which utilizes a single motor that mechanically drives all of the film advancing elements.

Figure 2 illustrates a front view of a motion picture film projector according to a preferred embodiment of the invention. Figure 3 illustrates a side view of a motion picture film projector according to a preferred embodiment of the invention.

Figure 4 illustrates a control panel which enables a user to control the microprocessor according to a preferred embodiment of the invention.

Figure 5 illustrates a block diagram showing the microprocessor connections to the stepper motors and control panel according to a preferred embodiment of the invention.

Figures 6a-6d illustrate the operation of a dual shutter assembly in accordance with a preferred embodiment of the present invention.

Figures 7a and 7b illustrate the control module.

Figure 8 illustrates the connection of the control module to the projector housing. Detailed Description of the Preferred Embodiment

Figure 2 illustrates a side view of a motion picture film projector 200 showing a preferred embodiment of the invention which consists of six separate stepper motors 290, 240, 291, 292, 280, 281 used to advance the film 250 through the projector 200 and to drive a dual shutter blade assembly 210. The stepper motor 290 is attached to an upper film drive sprocket 220. The stepper motor 291 is attached to a lower film drive sprocket 222. The stepper motor 240 is attached to an intermittent film drive sprocket 221. The stepper motor 260 is attached to a first shutter 211. The stepper motor 280 is attached to a second shutter 212. The stepper motor 292 is attached to a sound drive sprocket 223. Each of these stepper motors is individually controlled by a single microprocessor (not shown) which in turn is controlled by a plurality of control buttons (not shown) accessible by a projector operator.

The preferred embodiment of the invention shown in Figure 2 operates as follows. The film 250 is unspooled from a film feed apparatus (not shown) and is first fed to an upper film drive sprocket 220. A minimum of 90° of engagement of the film 250 with the upper film drive sprocket 220 is desirable. The film 250 is held in place by one or more pads or roller sprockets 206, 226. The upper film drive sprocket 220 preferably rotates at a constant speed of 240 revolutions per minute (rpm) and is used to pull the film 250 from the film feed apparatus (not shown) into the projector housing 201. From the upper film drive sprocket 220, the film 250 is formed into an upper film loop 251 comprising approximately four frames and is then fed through a film gate 260 directly opposite the shutter assembly 210. In the film gate 260, the film 250 is illuminated by the light from the lamphouse 261, from a light source (not shown), and the image on the film is projected onto the screen. From the film gate 260, the film 250 is engaged by an intermittent film pulldown sprocket 221 which intermittently pulls the film 250 down one frame at a time so that it can be illuminated to project an image onto a screen. Preferably, the pull down time is approximately 25% of the overall frame transfer time. In one preferred embodiment of the invention, the frame pull down time is approximately 10 milliseconds. The frame is then held for approximately 30 milliseconds as the shutter blades 211, 212 open and allow the light from the lamphouse 261 to illuminate the frame onto a screen. Before the end of the 30-millisecond hold time, the shutter blades 211, 212 close the opening (not shown) and prevent the screen from being illuminated. Once the shutter assembly 210 has closed the opening, the next frame is pulled into position.

From the intermittent film drive sprocket 221, the film 250 is formed onto a lower film loop 252 comprising preferably four frames, and is fed to a lower film drive sprocket 222. The lower film drive sprocket 222 engages the film 250 and drives it at a uniform speed to the sound head 275 and the sound capstan 270. The sound head 275 reads the sound information from the film 250, and the sound information is processed by the projector's sound system (not shown). From the sound head 275, the film 250 is engaged by the sound sprocket 223 and is spooled onto the film storage means (not shown). Figure 3 discloses a front view of the invention. From the film feed apparatus (not shown), the film 250 is passed to the upper film drive sprocket 220. The upper film drive sprocket is powered by the stepper motor 290 that is controlled by the microprocessor (not shown). From the upper film drive sprocket, the film is looped and is driven past the shutter assembly 210 where the film 250 is illuminated through the aperture 260. Each shutter blade 211, 212 contains a pair of openings 213 that include approximately 50% of the surface area of the shutter blades 211, 212. The intermittent film drive sprocket 221 pulls each frame, one at a time, into position for illujr-ination. The intermittent film drive sprocket is independently powered by the stepper motor 293, which is controlled by the microprocessor (not shown). From the intermittent film drive sprocket 221 , the film 250 is again looped and passed to the lower film drive sprocket 222. The lower film drive sprocket is independently powered by the stepper motor 291, which is controlled by the microprocessor (not shown). From the lower film drive sprocket 222, the film 250 is passed along the sound head 275 to the sound sprocket 223. The sound sprocket 223 drives the film 250 out of the projector housing 201 onto the film storage means (not shown). The sound sprocket is independently powered by a stepper motor 292 that is controlled by the microprocessor (not shown).

Because each stepper motor is individually controlled, there is no requirement for complicated belt or gear systems to drive each of the moving parts. The relative timing of each of the motors is synchronized by a central microprocessor rather than through gear ratios or timing belt coupling. The speed of each motor can be finely tuned through the microprocessor by using a series of controls located on the microprocessor or on a control panel which is connected to the microprocessor.

Figure 4 represents a control panel used in a preferred embodiment of the invention. The control panel 400 is electrically connected by a wire bus to the control module (not shown). The control panel 400 includes a plurality of buttons 430, 440, 450, 460, 470, 480, 490, 493, 495.

The control panel 400 also includes a plurality of diagnostic lamps 401, 410, 420 that are located on a diagnostic light sub-assembly 402. Each button controls a separate function related to the relative and overall speeds of the stepper motors. The buttons 460, 470 labeled "Upper Loop" control the size of the upper film loop 251. When the button 460 labeled "Increase" is pressed, the microprocessor in the control module is directed to increase the speed of the stepper motor

290 attached to the upper film drive sprocket 220 relative to the speed of the stepper motor 293 attached to the intermittent film drive sprocket 221. The microprocessor thereby increases the size of the upper film loop 251 as more film accumulates between the two sprockets. When the user releases the button, the speeds of the two motors return to normal and the size of the upper film loop 251 remains steady. A reduction in the upper film loop 251 can be achieved using the corresponding button 470 labeled "Decrease." Upon depressing this button, the microprocessor is directed to slow the speed of the stepper motor 290 attached to the upper film drive sprocket 220 relative to the speed of the stepper motor 293 attached to the intermittent film pulldown sprocket 221. The size of the upper film loop 251 thereby decreases as the film 250 enters the intermittent film drive sprocket 221 from the accumulated upper film loop 251 faster than it enters from the upper film drive sprocket 220. The lower film loop 252 can be similarly increased or decreased using the buttons 450, 480 identified for the lower film loop labeled "Lower Loop." The aperture and turret of the projector can be alternated between a flat picture and a picture viewed in cinemascope by using the buttons 430, 440 labeled "Aperture/Turret."

As will be explained in more detail below, the overall speed of the projector is monitored using the light 410 labeled "Speed 24 FPS." This light 410 is lit whenever the film is running at its normal speed of 24 fps. The film 250 can be jogged at half speed using the button 493 labeled "Film Jog." Depressing this button 493 directs the microprocessor to slow the speed of all stepper motors to half speed while the film loading is tested. The button 490 labeled "Douser

Open/Close" turns the projector illumination light on and off. The light 420 labeled "Fault" indicates to the projector operator that a mechanical or electrical failure in the projector has occurred requiring immediate attention. The light 401 labeled "Ready" indicates that the projector is available for operation. Figure 5 shows the connective relationship between the control panel 510, a microprocessor 500, and the six stepper motors 290, 291, 260, 280, 240, 292 and the diagnostic light sub-assembly 402 used in the preferred embodiment of the invention. The entire system of speeds and timings can be reset by reprogramming the microprocessor 500. This feature enables the projector to use film which has been exposed at different rates. Because all of the speeds of the invention are controlled by a microprocessor 500 the invention is easily changed from one speed to another.

A standard projector includes a single shutter blade which has 50% of its area open. Figure 6a-6d show a first shutter blade 211 and a second shutter blade 212 each having two opposed openings that leave open approximately 50% of the overall blade surface. For ease of illustration, the blades are shown spaced apart, however, it should be understood that the blades are spaced very close together in the projector system illustrated in Figures 2 and 3. The shutter blades 211, 212 are used to block projection of the film as the film is advanced to the next frame by the intermittent film pulldown sprocket. The purpose of the shutter blade 210 is to block light from the projector aperture during the intermittent film pulldown cycle. The use of double shutter blades is desirable over a single shutter blade, because the dual shutter blades 211, 212 rotate in opposite directions at approximately 1440 rpm thereby allowing the shutter blades 211, 212 to alternately permit and preclude the light propagating to the screen twice as fast as a single blade. Using this method, shutter efficiency improves to nearly 50% of the maximum illumination. Figure 6a illustrates the shutter blades 211, 212 in a position in where light falling onto the first shutter blade 211 is blocked by opaque portion of the blade. Figure 6b illustrates the shutter blades 211, 212 at a time shortly after that shown in Figure 6a. In Figure 6b, the shutter blades 211, 212 have partially rotated in opposite directions such that the first shutter blade 211 passes the light falling onto the shutter opening, but the second shutter blade 212, has rotated such that the opaque portion of the blade blocks the light. Figure 6c illustrates the shutter blades 211, 212 at a time shortly after that shown in Figure 6b. In Figure 6c the shutter blades 211, 212 have partially rotated such that the light incident on the shutter blades 211, 212 passes through openings in each of the shutter blades 211, 212 and onto a screen (not shown). Figure 6d illustrates the shutter blades 211, 212 at a time shortly after that shown in Figure 6c. In Figure 6d, the shutter blades have partially rotated such that the light incident on the first shutter blade 211 is blocked by the opaque portion of the blade. The shutter blades 211, 212 rotate at high speeds alternately blocking and unblocking the light as the film (not shown) is advanced and stopped on a frame by frame basis. The shutter timing is adjusted to exactly match the pulldown cycle of the intermittent mechanism. The foregoing paragraph provides an overview of the operation of the invention.

Specific advantages of the invention will now be described in the following more detailed description.

As shown in Figure 2, in order for the dual shutter system 210 to achieve its goal, both shutters 211, 212 must be timed perfectly not only relative to one another, but also with respect to the intermittent film pulldown sprocket 221. If the shutters 211 , 212 are open while the film is still in a pulldown operation, a "travel ghost" is apparent to the viewer. The "travel ghost" appears as a slight blurring of the bottom edges of an image. If the blades 211, 212 are not perfectly timed with respect to one another, the screen appears to flicker. In order to prevent these phenomena from disrupting film exhibition, conventional projectors are required to be periodically calibrated and adjusted.

The prior art calibration procedure to eliminate the "travel ghost" involves the services of a projector maintenance expert who must perform a service call on the projector. The calibration process involves the steps of: 1) stopping the projector and removing the film; 2) aligning and adjusting the shutter blades by loosening and tightening screws on the shutter shaft; 3) manually moving the shutter blades on the shaft until a "notch" or other mark on the shutter blade aligns with a pin or mark on the projector; 4) rethreading the film and testing the result. A test film is then used to project an image of "squares" on a screen. These squares are measured for a percentage of the square that is blurred. This percentage is measured against the overall size of the projected square to derive the "travel ghost" specifications for the projector. This procedure is repeated through trial and error until a satisfactory result is achieved. Maintenance manuals specify that a calibration using this adjustment procedure results in at best a ±5% deviation from optimal. If a "travel ghost" problem appears during actual film exhibition, a theater operator must usually either cancel the exhibition and call a maintenance operator, or allow the problem to persist until maintenance can be performed. In either case, with a conventional projector, a

"travel ghost" or flicker problem cannot be corrected during the operation of the film projector.

The invention allows these costly steps to be eliminated by using the microprocessor to control the individual stepper motors attached to each of the shutter blades and the intermittent film pulldown sprocket as shown in Figure 5. According to the invention, the microprocessor 500 is connected to the first shutter stepper motor 260 which drives the first shutter blade 211. The microprocessor 500 is also connected to the second shutter stepper motor 280 which drives a second shutter blade 212 in an opposite direction. The microprocessor 500 is also connected to a plurality of buttons located inside the projector housing 200. Using the buttons attached to the microprocessor 500 inside the projector housing, a projector operator is able to adjust the relative and overall speeds of the shutter stepper motors 260, 280 driving each shutter. Phasing

(alignment) of the shutter blades 211, 212 can be performed by a projector operator during projector operation by engaging the buttons located on the microprocessor and observing the screen until the "travel ghost" problem disappears.

In order to advance the shutters 211, 212 relative to the hold time of the film 250, the projector operator depresses a first predetermined button on the microprocessor 500. In order to retreat the shutters 211, 212 relative to the hold time of the film, the projector operator depresses a second predetermined button on the microprocessor 500. Engagement of these buttons instructs the microprocessor 500 to gradually increase or decrease the speed of the stepper motors driving each shutter. As the shutter opening 213 more closely aligns with the frame hold time, the projector operator can visually inspect the result on the screen. When the projector operator deems the screen clarity sufficiently free of "travel ghost" problems, the projector operator releases the predetermined button on the microprocessor 500. This returns the shutter stepper motors 260, 280 to their original speed which is then synchronized with each of the other stepper motors 290, 291, 260, 280, 240, 292. The above described adjustment process results in a substantially ideal alignment that cannot be readily achieved using the conventional manual adjustment process. This alignment procedure can be done either during a test sequence, or during film exhibition to correct any problem related to the timing of the shutter blades 211, 212. The present invention is able to adjust the relative and overall shutter speeds "on the fly" thereby eliminating the need for an expensive and time consuming maintenance call. The buttons located on the microprocessor 500 panel can be used to adjust the shutter timing by any individual familiar with film projection and need not be done by a maintenance specialist. The buttons for adjusting the shutter timing are not located on the control panel 400 in order to avoid accidental misalignment of the shutter blades by an inexperienced projector operator. Further, the adjustment procedure does not require the repeated manual loading and unloading of the film in order to accomplish the adjustment through trial and error, and can be accomplished during actual film exhibition if necessary. A user is able to use the buttons provided on the microprocessor 500 to modify the shutter timing until the "travel ghost" disappears. The invention is thereby able to avoid the cancellation of theater productions and lost revenue due to misalignment of the shutter assembly

210.

The present invention also allows a projector operator to adjust the film loop size as shown in Figure 2. When a conventional projector is threaded, the film loops 251, 252 must be included due to the intermittent nature of the film pulldown process. Two film loops are conventionally used, the upper film loop 251 between the intermittent film pulldown sprocket

221 and the upper film drive sprocket 220, and the lower film loop 252 between the intermittent film pulldown sprocket 221 and the lower film drive sprocket 222. Typically, the film loops 251, 252 are approximately four frames long and are used to provide slack in the film 250 because the intermittent film pulldown sprocket 221 operates quickly on a frame by frame basis, while the upper and lower film drive sprockets 220, 222 operate at a continuous speed. The film loops 251, 252 allow the intermittent film pulldown sprocket 221 to advance the film extremely quickly and then come to a complete stop without impacting the continuous feed from the upper/lower film drive sprockets 220, 222 or placing undue tension on the film 250. Problems sometimes arise in threading the film through the entire projector mechanism that cause the film loop 251, 252 to be either too large or too small. If the projector operator does not properly estimate the amount of film to create a properly sized loop, the film 250 must be completely detached from the projector and rethreaded. Film loops 251, 252 that are too small place a high degree of tension on the film 250 and could break the film 250 if the problem is severe. If the film loops 251, 252 are too large, the film 250 tends to "flap", both making unwanted noise and potentially causing the film 250 to be caught in another drive mechanism thereby also damaging the film 250. It is desirable therefore to be able to adjust the size of the film loops 251, 252 without having to stop the projector and rethread the film 250.

The invention avoids the above problem by using stepper motors to individually control the intermittent film pulldown sprocket 221 and the upper and lower film drive sprockets 220, 222. In the invention, the microprocessor 500 is used to individually control each stepper motor 290, 240, 291. The microprocessor 500 is also connected to the control panel 400 that includes the loop control buttons 450, 460, 470, 480. These buttons allow a user to control the relative speeds of the upper and lower film drive sprockets 220, 222 relative to the speed of the intermittent film pulldown sprocket 221. By manipulating the buttons 450, 460, 470, 480 on the control panel 400, a user is able to direct the microprocessor 500 to temporarily increase the speed of the upper film drive sprocket 220 relative to the intermittent film pulldown sprocket 221. Because the speed of the intermittent film pulldown sprocket 221 does not change, the size of the upper film loop 251 increases. The operator can also temporarily slow the speed of the upper film drive sprocket 220 relative to the speed of the intermittent film pulldown sprocket 221 in order to reduce the size of the upper film loop 251. A similar adjustment can be performed with respect to the lower film drive sprocket 222 and the lower film loop 252. Thus, by using the control panel 400 to adjust the relative speeds of the individually controlled stepper motors, a user is able to adjust the size of the upper and lower film loops 251, 252 while the projector is ninning without the need to stop and rethread the projector each time the loop size is found to be incorrect. This ultimately results in a faster film load time and results in fewer operator errors that can lead to costly film breakages.

An additional feature of the invention allows the user to run the entire projector at lower than conventional operating speeds. Generally, projectors have only a single operating speed. This requires an operator to load the film and subsequently test the threading at full speed. If a film is improperly threaded, damage may occur as the film is pulled out of proportion before the operator is able to recognize the problem and stop the projector to make the necessary corrections. The present invention, by using the control panel 400 to adjust the speeds of the stepper motors 290, 291, 260, 280, 240, 292, can adjust the speed of all such motors so that the film threading can be checked at a speed much lower than the conventional operating speed, thereby avoiding extensive damage to an improperly threaded film.

The present invention also includes a removable control module as shown in Figures 7a and 7b. The control module is comprised of two printed circuit boards (PCB) 10. A microprocessor and support circuitry (not shown) are mounted on the first PCB. The first PCB is electrically connected by solder to a second PCB backplane which contains two backplane male edge connectors 50, 60 disposed on opposite ends thereof. The backplane male edge connectors 50, 60 contain conductive pads 55 which are connected to the first PCB and ultimately to the microprocessor through wire traces in the PCB. The second PCB backplane also includes a DB25 connector that permits the microprocessor to communicate with an outside computer which is then capable of performing diagnostics, software upgrades, and other modifications.

The backplane male edge connectors 50, 60 are designed to be inserted into two female edge connectors 70, 80 mounted onto the chassis of the projector housing 100 as shown in Figure 7b. The female edge connectors 70, 80 also contain electrically conductive pads that correspond to the conductive pads of the made edge connectors 50, 60 and make electrical contact when properly joined. The female edge connectors 70, 80 are used to allow the microprocessor to communicate with the control panel and with the other stepper motor modules (not shown). The upper female edge connector 70 is mounted onto a pivot arm 90 by a single point 110 that permits the upper female edge connector to rotate freely about the single point. The pivot arm is connected to the projector housing at a different point 120 at the distal end of the pivot arm 90. The pivot arm engages and releases the upper female edge connector 70 with the upper edge connector 50 on the PCB backplane on the control module. Because the female edge connector 70 is free to rotate about a different point than the pivot arm, the female edge connector will engage the upper male edge connector on the control module normal to the longitudinal axis of the PCB. Because there is no lateral motion during the engagement and disengagement process, there will be less wear and tear on the electrical contacts of both the upper female edge connector 70 and the upper male edge connector 50.

Once the lower edge connector 60 has been inserted into the stationary lower female edge connector 80, the pivot arm 90 can be rotated to engage or disengage the upper female edge connector 70 with the upper male edge connector 50. When the upper edge connectors are firmly secured, the control module 100 is in full communication through the wire bus (not shown) with the control panel, stepper motor modules and the power module (not shown).

The modular nature of the control module provides several advantages. First the removable nature of the control module permits the easy installation and replacement of the control module in the event of a failure or a software upgrade to the microprocessor program.

Second, as shown in Figure 8, the female edge connectors space the control module slightly apart from the projector housing. This permits better ventilation and cooling of the microprocessor and the control module. Third, because the second PCB is of a standard dimension, the microprocessor and other components on the first PCB can be upgraded, modified or replaced without altering the connection method to the projector itself. Thus, regardless of the electronic hardware used to implement the control module, the connection method to the projector will not change. Fourth, because there are only two connections to be made to install the control module, installation and removal are greatly facilitated.

Finally, the male edge connectors 50, 60 are of different widths. Similarly the female edge connectors 70, 80 are also of different widths to correspond to the male edge connectors. Because the upper and lower edge connectors of different widths, it is impossible to incorrectly orient the control module during installation. The control module will not fit unless it is properly oriented. This will prevent users from causing errors and or damage to the projector and control module by misorienting the control module during installation.

By pressing the button 493 labeled "Film Jog" shown in Figure 4, the operator is able to direct the microprocessor 500 to slow each of the stepper motors 290, 291, 260, 280, 240, 292 to a fraction of the normal operating speed (e.g., 50% of normal operating speed). The stepper motors 290, 291, 260, 280, 240, 292 will continue at this slower speed until the "Film Jog" button 493 is released. When the "Film Jog" button 493 is returned to its normal position, all stepper motors 290, 291, 260, 280, 240, 292 are completely stopped until the operator depresses the "Start/Stop" button 495 on the control panel to restart the projector at full speed.

Similarly, as explained above, the microprocessor 500 can also be directed to change the speeds of the stepper motors to accommodate different film exposure speeds. The entire system of speeds and timings can be reset by reprogramming the microprocessor 500. This feature enables the projector to use film which has been exposed at different rates. Film is traditionally exposed at 24 frames per second (fps). However, there has been a demand for a 30 fps film speed. In order for conventional projectors to accommodate both a 24 and 30 fps film speeds, an extensive gear replacement must be performed each time the operator wishes to change the projector to a different speed. Gears of one fixed ratio must be replaced with gears of another ratio in order to effect the speed change. Because all of the speeds of the present invention are controlled by the microprocessor 500 mounted on the control module, by changing the programming of the microprocessor 500, the user is able to change from one speed to another. The user can also upgrade by swapping out the control module for an updated version. The microprocessor 500 can easily be reprogrammed, or the programmable read only memory (PROM) (not shown) replaced so that the microprocessor 500 is instructed to increase the speed of every stepper motor 290, 291, 260, 280, 240, 292 such that the film 250 is viewed at 30 fps instead of the standard 24 fps speed. Because the components are modular individually- controlled stepper motors or electronic modules no gear or belt replacement is necessary. Only a reprogram of the microprocessor 500 or a PROM replacement need be performed to effect the change. If some other speed is desired, e.g., 40 fps, all that is required is that the microprocessor 500 be reprogrammed or the PROM switched to the 40 fps speed, as can be done by one of skill in the art of microprocessor design and programming.

The invention also includes a system whereby diagnostic information is fed back to the microprocessor 500. Each stepper motor 290, 291, 260, 280, 240, 292 includes a sensor/encoder (not shown) which counts the number of revolutions per minute of the motor to which it is attached. The encoder electronically sends this information to the microprocessor which monitors the speed of the motor. As shown in Figure 5, the microprocessor 500 is connected to each of the stepper motors 290, 291, 260, 280, 240, 292 by two buses. The first buses 521, 531, 541, 551, 561, 571 are used to transmit control information from the microprocessor 500 to the respective stepper motor. The second buses 522, 532, 542, 552, 562, 572 are used to transmit speed information from each individual stepper motor back to the microprocessor 500. The microprocessor 500 analyzes this information and takes an appropriate action based upon a preset criteria.

Depending on the information obtained, the microprocessor 500 is able to take a variety of actions. The microprocessor 500 monitors the speed of each of the stepper motors 290, 291,

260, 280, 240, 292 to ensure that their speed remains constant and that each stepper motor remains synchronized with the other stepper motors throughout the operation of the projector. If a motor begins to fall slightly out of sync with the other motors, the microprocessor 500 attempts to resynchronize the motor. The microprocessor 500 first lights a diagnostic lamp 420 on the diagnostic light sub-assembly 402 on the control panel 400 as shown in Figure 4 labeled as "Fault" to indicate a minor discrepancy. The diagnostic "Fault" lamp 420 remains lit until the microprocessor 500 is able to correct the problem, either by speeding up or slowing down the errant motor. If the motor falls out of sync to a preset degree, the microprocessor 500 shuts down all of the stepper motors to prevent damage to the film and to the projector itself. The microprocessor 500 then identifies the faulty motor and displays a permanent fault signal on the diagnostic lamp 420 on the diagnostic light sub-assembly 402 located on the control panel 400.

Because prior theatrical projectors include only a single motor which drives all of the moving parts through a complex series of gears and belts, they are extremely difficult to repair. If a single component fails, a number of gears and belts must be removed in order to replace the faulty part(s). This can only be done by an experienced projector technician. Various screws, pins and belts must be removed to replace even a minor part due to the interrelated nature of each of the parts. This causes repair to these machines to be costly and time consuming. Once repaired, the technician must perform a complex and laborious recalibration of the entire projector to resynchronize the complex timing mechanisms for each part. Because the above described invention uses a plurality of independently driven and controlled stepper motors, it avoids the above problems. Because there are no gears or belts that operate to synchronize the various film driving elements, the invention is designed in a modular fashion. The invention includes six major modules: 1) a film drive module; 2) a intermittent pulldown module; 3) a shutter module; 4) a microprocessor module; 5) a power supply; and (6) a control module. Each of these modules can be removed and replaced independent of the other modules. Because the microprocessor 500 mounted on the control module performs the complex timing sequences necessary to ensure proper film advancement, it is not necessary to remove and recalibrate many different gears and belts. Each module is designed to be easily removed and replaced because with the exception of the control module, its only physical attachments are to the housing of the projector and a bus connection to the microprocessor, the only physical connections of the control module are the female edge connectors shown in Figure 7b. Thus, removal of the bolts attaching the other modules to the projector housing and disconnection or unplugging of the buses leading to the control module are all that is required in order to remove and replace a modular stepper motor element. This replacement can be easily performed by an operator without the need for a specialized technician. Once a new stepper motor module is installed, an operator need only depress the "Start/Stop" button 495 on the control panel 400 as shown in Figure 4. Upon selection of the "Start/Stop" operation, the microprocessor 500 on the control module is instructed to restart all of the motors and to resynchronize them before film is loaded. Once the resynchronization is complete, the projector is again ready for operation. Thus, using separate and independently controlled stepper motors to power each film drive mechanism not only eliminates the complex gear systems characterizing prior projectors, it also eliminates the need for specialized technicians to perform repairs.

It will be appreciated that certain variations in the projector system of the present invention and its method of controlling the stepper motors may suggest themselves to those skilled in the art. The foregoing detailed description is to be clearly understood as given by way of illustration, the spirit and scope of this invention being limited solely by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A motion picture film projector for projecting an image onto a screen that (1) eliminates the need for mechanical gears or belts to maintain synchronization of the continuous and intermittant drive elements of the projector and (2) eliminates the need for costly and time consuming manual adjustment, said projector comprising: a plurality of continuous film drive elements used to advance a film through a projector; an intermittent film drive element used to periodically advance said film through said projector one frame at a time; a shutter assembly for alternatively passing and blocking light passing through said film; and a processor element electrically connected to said continuous film drive elements, to said intermittent film drive element, and to said shutter assembly that independently controls each of said continuous film drive elements, said intermittent film drive element and said shutter assembly, said processor element (1) automatically adjusting the timing of the projector shutter assembly during the projector's operation to improve the projector brightness and film clarity and (2) selectively controlling said shutter assembly relative to the speed of said intermittant drive element to automatically correct image defects.

2. In a motion picture film projector for projecting an image onto a screen having continuous film drive elements, an intermittent film drive element, and a shutter assembly, the improvement comprising a microprocessor controller electrically connected to said continuous film drive elements, to said intermittent film drive element, and to said shutter assembly, said controller independently controlling each of said continuous film drive elements, said intermittent film drive element and said shutter assembly so that timing gears and belts are not required to operate the intermittant film drive element in precise synchronization with the continuous film drive element or the shutter assembly.

3. A motion picture film projector for projecting an image onto a screen comprising: a plurality of continuous film drive elements used to advance a film through a projector; an intermittent film drive element used to periodically advance said film through said projector one frame at a time; a shutter assembly for alternatively passing and blocking light passing through said film; and a processor element electrically connected to said continuous film drive elements, to said intermittent film drive element, and to said shutter assembly, said processor element independently controlling each of said continuous film drive elements, said intermittent film drive element and said shutter assembly.

4. A motion picture film projector for projecting an image onto a screen as in claim 3, wherein said film drive element, said intermittent film drive element and said shutter assembly each further comprise a stepper motor.

5. A motion picture film projector for projecting an image onto a screen as in claim 3, wherein said processing element is a microprocessor.

6. A motion picture film projector for projecting an image onto a screen as in claim 4, wherein said processing element controls the speed of each of said stepper motors.

7. A motion picture film projector for projecting an image onto a screen as in claim 3, wherein said shutter assembly comprises: a first shutter blade having approximately 50% of the surface of said shutter blade open; and a second shutter blade having approximately 50% of the surface of said shutter blade open.

8. A motion picture film projector for projecting an image onto a screen as in claim 7, wherein said first shutter blade is connected to a first stepper motor and said second shutter blade is connected to a second stepper motor, and wherein the speeds of said stepper motors are controlled by said processing element.

9. A motion picture film projector for projecting an image onto a screen as in claim 8, wherein said first stepper motor and said second stepper motor are timed so that the openings of said first and second shutter blades are coincident when a frame of film is stationary before a viewing aperture.

10. A motion picture film projector for projecting an image onto a screen as in claim 9, wherein said processing element selectively increases or decreases the speed of first said stepper motor relative to said second stepper motor in order to correct image defects.

11. A motion picture film projector for projecting an image onto a screen as in claim 10, wherein said processing element selectively increases or decreases a speed of first said stepper motor and said second stepper motor relative to a speed of said intermittent film drive element in order to correct image defects.

12. A motion picture film projector for projecting an image onto a screen as in claim 11 , wherein said processing element selectively alters the speed of either or both of said first stepper motor and said second stepper motor.

13. A motion picture film projector for projecting an image onto a screen as in claim 3, wherein said processing element selectively increases or decreases the speed of one of said film drive elements relative to said intermittent film drive element in order to increase the amount of film therebetween.

14. A motion picture film projector for projecting an image onto a screen as in Claim 3, further comprising a removable control module.

15. A motion picture film projector for projecting an image onto a screen as in

Claim 14, wherein said control module further comprises said processing element.

16. A motion picture film projector for projecting an image onto a screen as in claim 3, wherein each said stepper motor further comprises a sensor that records information including a speed of each said respective stepper motor and transmits said speed information to said processing element.

17. A motion picture film projector for projecting an image onto a screen as in claim 16, wherein said processing element compares said speed information from each said sensor and indicates whether all said speed information is substantially the same for each said stepper motor.

18. A motion picture film projector for projecting an image onto a screen as in claim 17, wherein said processing element halts all said stepper motors if said speed information indicates that a speed of any one of said stepper motors exceeds a speed of any other of said stepper motors by a predetermined amount.

19. A method for projecting a motion picture film onto a screen for viewing comprising the steps of: feeding the film through a first film drive element; feeding the film between a projector lamp and a shutter assembly which periodically permits light from the projector lamp that passes through the film to fall onto a screen; feeding the film through an intermittent film drive element; feeding the film through a second film drive element; electronically controlling said first and second film drive elements, said intermittent film drive element, and said shutter assembly using a processing element.

20. A method for projecting a motion picture film onto a screen for viewing as in claim 19, wherein each of said first and second film drive elements, said intermittent film drive element and said shutter assembly further comprises a stepper motor.

21. A method for projecting a motion picture film onto a screen for viewing as in claim 20, wherein said processing element controls a speed and a timing of each of said stepper motors.

22. A motion picture film projector for projecting an image onto a screen that does not include a conventional gear/belt drive system, said projector comprising: a film drive module; an intermittent film drive module; a shutter module; a controller module; and a power supply: wherein each of said film drive module, said intermittent film drive module, said shutter module, said controller module, and said power supply are connected to said motion picture film projector independently so that each of these modules can be easily replaced without the need of dismantling the conventional gear/belt system to thereby allow repairs to be made quickly and easily.

23. A motion picture film projector for projecting an image onto a screen that does not include a conventional gear/belt drive system, said projector comprising: a film drive module; an intermittent film drive module; a shutter module; a controller module; and a power supply; wherein each of said film drive module, said intermittent film drive module, said shutter module, said controller module, and said power supply are connected to said motion picture film projector independently so that each of these modules can be easily replaced without the need of dismantling of the conventional gear/belt system to thereby allow repairs to made quickly and easily.

24. A motion picture film projector for projecting an image onto a screen as in Claim 23, wherein said controller module comprises at least one backplane edge connector that is connected to an edge connector receptacle that electrically connects said controller module to said film drive module; said intermittent film drive module, said shutter module, and said power supply.

25. In a motion picture film projector for projecting an image onto a screen having continuous film drive elements, an intermittent film drive element, and a shutter assembly, the improvement comprising a microprocessor controller electrically connected to said continuous film drive elements, to said intermittent film drive element, and to said shutter assembly, said controller independently controlling each of said continuous film drive elements, said intermittent film drive element and said shutter assembly so that timing gears and belts are not required to operate the intermittant film drive element in precise synchronization with the continuous film drive element or the shutter assembly, said microprocessor controller comprising a controller module which can be easily installed and removed from said film projector in the event of failure or software upgrade to the microprocessor program.

26. In a motion picture film projector for projecting an image onto a screen having continuous film drive elements, an intermittent film drive element, and a shutter assembly, the improvement comprising a microprocessor controller electrically connected to at least one of said continuous film drive elements, said intermittent film drive element, or said shutter assembly, said microprocessor controller comprising a controller module which can be easily installed and removed from said film projector in the event of failure or software upgrade to the microprocessor program.