CA1118623A - Automatic exposure system for pass through microfilm cameras - Google Patents
Automatic exposure system for pass through microfilm camerasInfo
- Publication number
- CA1118623A CA1118623A CA000313744A CA313744A CA1118623A CA 1118623 A CA1118623 A CA 1118623A CA 000313744 A CA000313744 A CA 000313744A CA 313744 A CA313744 A CA 313744A CA 1118623 A CA1118623 A CA 1118623A
- Authority
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- Canada
- Prior art keywords
- rotary shutter
- exposure system
- automatic exposure
- set forth
- shutter
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000010276 construction Methods 0.000 claims description 7
- 239000003990 capacitor Substances 0.000 description 5
- 230000001276 controlling effect Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- 230000010355 oscillation Effects 0.000 description 4
- 230000003321 amplification Effects 0.000 description 3
- 238000013016 damping Methods 0.000 description 3
- 238000003199 nucleic acid amplification method Methods 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 230000003014 reinforcing effect Effects 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 230000004069 differentiation Effects 0.000 description 1
- 239000011796 hollow space material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B27/00—Photographic printing apparatus
- G03B27/72—Controlling or varying light intensity, spectral composition, or exposure time in photographic printing apparatus
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- General Physics & Mathematics (AREA)
- Projection-Type Copiers In General (AREA)
- Exposure Control For Cameras (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An automatic exposure system for pass through micro-film cameras is disclosed. The original copies are scanned photo-electrically for generating a reflectance reference signal.
A rotary shutter is employed for attenuating the light beam illuminating the original copy to be filmed by tilting into the path of the beam. An angular detector is coupled with the rotary shutter for determining its momentary angular position and for generating a corresponding signal. A comparison means compares the signal from the shutter ? signal based on the reference signal for producing a correction signal to drive a motor connected to the axis of the rotary shutter.
An automatic exposure system for pass through micro-film cameras is disclosed. The original copies are scanned photo-electrically for generating a reflectance reference signal.
A rotary shutter is employed for attenuating the light beam illuminating the original copy to be filmed by tilting into the path of the beam. An angular detector is coupled with the rotary shutter for determining its momentary angular position and for generating a corresponding signal. A comparison means compares the signal from the shutter ? signal based on the reference signal for producing a correction signal to drive a motor connected to the axis of the rotary shutter.
Description
1~8623 BACKGROUND OF THE INVENTION
1. Field of the Invention . . .
The present invention relates to an automatic exposure for pass through microfilm apparatus scanning the brightness of each original to be filmed and employing the resulting signal for the nominal value for controlling the amount of light falling on the film.
1. Field of the Invention . . .
The present invention relates to an automatic exposure for pass through microfilm apparatus scanning the brightness of each original to be filmed and employing the resulting signal for the nominal value for controlling the amount of light falling on the film.
2. Description of the Prior Art An automatic exposure system for microfilm cameras of this type is disclosed in German Patent No. 1,214,524 issued on October 9, 1969 in the name of Agfa-Gevaert A.G. The original copy passing through is illuminated with a lamp of constant brightness and the light reflected by the original copy is determined by a conventional detector such as a photo-cell. Depending on the brightness of the original copy the output signal of the photocell varies and controls a silicon controlled rectifier or other power control for adjusting the brightness of the exposure lights of the scanning station inversely proportional to the output signal of the photocell.
The varied properties of the original copies are balanced by a change in the light intensity of the illuminating lamps.
The capabilities of such a pass through camera are limited by the relatively small control velocity of its control loop. The silicon controlled rectifier needs about 20 rnilli-seconds for adjustment and the inertia of the illuminating lamps is such as to take about 150 to 250 milleseconds for reaching the newly adjusted brightness. This results in a relatively small maximum passage speed for the original copies ~0 and in a relatively large minimum distance between two succeed-ing original copies. Such exposure control devices are therefore unsuitable for use in microfilm cameras of moder~ constxuctio~
,` ~
1~186Z3 capable of microfilming mare than 50,000 original copies per hour. At such high filming rates the maximum adjustment times are required to be 10 and up to maximum 20 milliseconds.
Another disadvantage of a pass through camera control-ling the brightness of the exposure lamps results from varying color temperatures of the exposure lamps with changing brightness, which is very disadvantageous for color filming of original copies.
Therefore the attempt was made to control the exposure not with the brightness of the exposure lamps but by electro-mechanical means by influencing the image beam path with shutters entered into the path (German Pa~entApplication D.O.S. 24 46 240pu blished on April 8, 1976 in the name of Misho). The realization of the disclosure failed, since such electromechanical systems have not been able up to now to reach the very short setting times of less than 20 milliseconds. A usual microfilm camera of conventional construction needs shutters of between about 40 and 50 cm in particular when both front and back of A4 dimension are to be microfilmed at the same time and this explains the dif-ficulties arising. It appeared up to now technically unrealiz-able to safely set shutters of such large dimensions within the very short times required. In German Patent Application D.O.S. No. 25 52 589 published on May 26, 1977 in the name of Afga-Gevaert A.G. a device is disclosed for ~utomatic control of exposure in microfilm pass through cameras. By detecting a light beam passed by a rotary shutter and multiplying with the reflectance of an original copy ar~
__~~~~
./
resultill product value with a reference value of deviltion signal was obtained. The deviation signal then controlled the shutter opening. The indirect way of obtaining the shutter adjustment is a disadvantage of this construction.
SUMMARY OF THE INVENTION
1. Purposes of the Invention . ~
It is an object of the invention to provide an exposure system for a microfilm camera having a setting time of less than about 20 milliseconds.
It is another object of the invention to provide an exposure system for a microfilm camera which assures reliable operation by emploving simple technical means. It is another object of the invention to provide an exposure system for a microfilm camera with a light but mechanically stable rotary shutter.
It is another object~of the invention to provide an exposure system for a microfilm camera with a direct sensing of the rotary angle of the shutter.
These and other objects and advantages of the present invention will become evident from the description which follows.
2. Brief Description of the Invention An automatic exposure system is disclosed for continuous pass through microfilm cameras. The brightness of each original copy to be filmed is individually tested by a testing static~n.
The resulting reference signal corresponding to the brightness of the original copy is employed for controlling the light intensity falling on the film. A locally fixed shutter is used for limiting the image beam width between object and film. A
l ~11186Z3 .
rotary shutter can be tilted by a drive motor into the path of ~he image beam defined by the locally fixed shutter. An ahgular detector is coupled with the rotary shutter for determining the momentary angle of the rotary shutter and for generating a corresponding actual signal. A comparison means compares the actual signal with a nominal signal based on the reference signal for generating a corresponding correction signal. A control means is fed with the correction signal for driving the motor to adjust the angle of the shutter wing. Preferably the motor is a DC motor with low momentum of inertia and is coupled directly to the shaft of the rotary shutter. More preferred is a motor with bell type armature connected to and forming one axis with the shaft of the rotary shutter. The angular detector is advantageously formed by a potentiometer having the same axis as the rotary shutter and mounted on the same shaft.
Preferably the rotary shutter is of essentially 2-fold,
The varied properties of the original copies are balanced by a change in the light intensity of the illuminating lamps.
The capabilities of such a pass through camera are limited by the relatively small control velocity of its control loop. The silicon controlled rectifier needs about 20 rnilli-seconds for adjustment and the inertia of the illuminating lamps is such as to take about 150 to 250 milleseconds for reaching the newly adjusted brightness. This results in a relatively small maximum passage speed for the original copies ~0 and in a relatively large minimum distance between two succeed-ing original copies. Such exposure control devices are therefore unsuitable for use in microfilm cameras of moder~ constxuctio~
,` ~
1~186Z3 capable of microfilming mare than 50,000 original copies per hour. At such high filming rates the maximum adjustment times are required to be 10 and up to maximum 20 milliseconds.
Another disadvantage of a pass through camera control-ling the brightness of the exposure lamps results from varying color temperatures of the exposure lamps with changing brightness, which is very disadvantageous for color filming of original copies.
Therefore the attempt was made to control the exposure not with the brightness of the exposure lamps but by electro-mechanical means by influencing the image beam path with shutters entered into the path (German Pa~entApplication D.O.S. 24 46 240pu blished on April 8, 1976 in the name of Misho). The realization of the disclosure failed, since such electromechanical systems have not been able up to now to reach the very short setting times of less than 20 milliseconds. A usual microfilm camera of conventional construction needs shutters of between about 40 and 50 cm in particular when both front and back of A4 dimension are to be microfilmed at the same time and this explains the dif-ficulties arising. It appeared up to now technically unrealiz-able to safely set shutters of such large dimensions within the very short times required. In German Patent Application D.O.S. No. 25 52 589 published on May 26, 1977 in the name of Afga-Gevaert A.G. a device is disclosed for ~utomatic control of exposure in microfilm pass through cameras. By detecting a light beam passed by a rotary shutter and multiplying with the reflectance of an original copy ar~
__~~~~
./
resultill product value with a reference value of deviltion signal was obtained. The deviation signal then controlled the shutter opening. The indirect way of obtaining the shutter adjustment is a disadvantage of this construction.
SUMMARY OF THE INVENTION
1. Purposes of the Invention . ~
It is an object of the invention to provide an exposure system for a microfilm camera having a setting time of less than about 20 milliseconds.
It is another object of the invention to provide an exposure system for a microfilm camera which assures reliable operation by emploving simple technical means. It is another object of the invention to provide an exposure system for a microfilm camera with a light but mechanically stable rotary shutter.
It is another object~of the invention to provide an exposure system for a microfilm camera with a direct sensing of the rotary angle of the shutter.
These and other objects and advantages of the present invention will become evident from the description which follows.
2. Brief Description of the Invention An automatic exposure system is disclosed for continuous pass through microfilm cameras. The brightness of each original copy to be filmed is individually tested by a testing static~n.
The resulting reference signal corresponding to the brightness of the original copy is employed for controlling the light intensity falling on the film. A locally fixed shutter is used for limiting the image beam width between object and film. A
l ~11186Z3 .
rotary shutter can be tilted by a drive motor into the path of ~he image beam defined by the locally fixed shutter. An ahgular detector is coupled with the rotary shutter for determining the momentary angle of the rotary shutter and for generating a corresponding actual signal. A comparison means compares the actual signal with a nominal signal based on the reference signal for generating a corresponding correction signal. A control means is fed with the correction signal for driving the motor to adjust the angle of the shutter wing. Preferably the motor is a DC motor with low momentum of inertia and is coupled directly to the shaft of the rotary shutter. More preferred is a motor with bell type armature connected to and forming one axis with the shaft of the rotary shutter. The angular detector is advantageously formed by a potentiometer having the same axis as the rotary shutter and mounted on the same shaft.
Preferably the rotary shutter is of essentially 2-fold,
3-fold or 4-fold rotation symmetry and constructed of sandwich !type. More preferred are rotary shutters having two wings glued ¦together and reinforced by fins parallel to the axis of the ¦rotary shutter.
The exposure control is provided by blocking a more or ¦less large part of the image beams by tilting the rotary shutter more or less into the image beam for varying the effective exposure time of a point on the continuously moving film according to the position of the rotary shutter. Unexpectedly, by employing of a motor driven rotary shutter very short setting times of slightly more than 10 milliseconds have been achieved in particular if the driving motor is provided with a bell type ~ 8623 'I
armatur and if the armature is connected with the shaft of the rotary shutter and forms the same axis, if the rotary shutter is built as a sandwich for better stability, if the rotary shutter is symmetrical with respect to the rotation axis and comprises two equal glued together wings with reinforcing fins parallel to the rotation axis. This results in a very low momentum of inertia of the rotary shutter and of the shutter drive. The forming and special construction of the rotary shutter provides a high rigidity for avoiding undesirable oscillati ~ns of the shutter system. In addition the direct action of the drive system on the shutter shaft provides an optimal power transmission between drive system and rotary shutter.
The inventionaccordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the apparatus hereinafter described and of which the scope of application will be indicated in the appended claims.
¦BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings in which is shown one of the various possible embodiments of the invention:
Fig. 1 is a view of a schematic diagram of the image beam path of a continuous microfilm camera;
Fig. 2 is a view showing the rotary shutter with drive motor and setting potentiometer;
Fig. 3 is a sectional view of the rotary shutter of ¦Fig. l;
i Fig. 4 is a view of a block diagram of the circuitry controlling the rotary shutter;
1~.186Z3 Fig. 5 is a view of a circuit of part of the block ; diagram of Fig. 4 in detail; and Fig. 6 is a view of a circuit of another part of the block diagram in Fig. 4 in detail.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The apparatus of the present invention comprises a locally fixed shutter for limiting the image beam path between original copies 1, 2, 3 and film 13, a rotary shutter 16 tiltable into the path of the beam defined by the locally fixed shutter; a drive motor 24 for tilting the rotary shutter, an angular detector for determining the momentary angular ( position and for generation of an actual signal, comparison ,~ circuitry 31 for comparing the actual signal with the nominal ~slgnal for generating of a corresponding correction signal, and means for controlling the drive motor with the correction signal as input.
, Referring now to Fig. 1 there are shown original copies 1, 2 and 3 to be microfilmed, which are carried by transport means (not shown) along a transport path in the direction of arrow A from an input station of a continuous microfilm pass through camera to an outgoing station. On the ~I transport path the original copies pass by a measurement station ), 4 for being illuminated with a lamp 5. A measuring device 6 comprising photoelectric elements measures the light reflected from the momentary original copy and allows determination of the brightness of the original copies. The original copies are illuminated for microfilming by lamps 14a and 14b. The scanning station 7 scans the reflected light in bands of the front and back sides of the momentary original copy and the front and back sides are imaged via surface mirrors 8, 9, 10, 11 and 12 onto the microfilm 13 running synchronously with the ~,~ .
---- ~
riginal ~opies into the direction of arrow ~. An imaging objective 15 focusses the image on the microfilm.
The rotation axis of a rotary shutter 16 is placed out-side of the image beam path 17, 18. Tilting the rotary shutter 16 out of its horizontal position results in a certain amount of image beam being blocked. The arrangement of the rotary shutter relative to the image heam path is shown in Fig. 3. The maximum width of the image beam path 17, 18 is determined by the slit width of the locally fixed shutter 19. When the shutter wings 161 and 162 are essentially in vertical position the image beam path is not influenced. When the rotary shutter 16 is tilted out of its vertical position more or less of the image beam path is blocked resulting in a change in the effective slit width as formed by locally fixed shutter 16 together with the rotary ;hutter. The length of the rotary shutter is 46 centimeters for imaging simultaneously the two beams 17, 18 having each a width corresponding to the width of A4 size. The rotary shutter has sadwich type construction and is additionally provided with reinfGrc~ing fins 161a, 161b, 161c, 162a, 162b and 162c running parallel to the rotation axis. This assures an extreme rigidity of the rotary shutter. The rigidity is indispensible for avoiding oscillations upon adjustment of its position. Such ¦oscillation would result in alternate bright and dark bands until the shutter comes completely to rest.
The shafts 21, 22 are attached to the cylindrical hollow space 163 ~ormed by the reinforcing fins 161b and 162b of the shutter wings 161 and 162. The shaft 21 is supported by the apparatus frame 23. The shaft 22 also forms the shaft for the driving motor 24. In order to keep the inertia of the shutter lllB623 and drive system as low as possible the motor is a direct current operated motor with bell type armature such as the direct current motor 3357/220 of Faulhaber Co., West-Germany. The bell type armature is connected to the shaft 22. The motor shaft 22 is coupled by bellows 25 to the precision potentiometer 26 for measuring the angular position of the motor and therewith the angle of the rotary shaft.
A functional diagram of the exposure automatic as disclosed is shown in Fig. 4. The light remission of the original copy to be microfilmed is measured with the photoelectric measuring device 6 and fed to an amplification and storage stage 30. The output of stage 30 is the nominal Un, which is fed into the input of a differential amplifier 31. The construction of such an amplification and storage stage 30 is for example disclosed in German paten application DT-OS 2 446 240 already mentioned hereinabove. The true momentary rotary shutter position is determined by potentiometer 26 operating as a voltage divider. The output voltage of the potentiometer is a measure for the angle position of the rotary shutter 16 and represents the actual voltage Ua. The Ua is entered into the other input of the differential amplifier 31. The output voltage QU provided by the differential amplifier 31 is proportional to the remaining adjustment of the tilting angle of the rotary shutter. A velocity signal va corresponding to the momentary angular velocity of the rotary shutter is required for bringing the motor 24 to the velocity vn specified by the nominal voltage Un. The values of this velocity va is formed by circuit 32 by differentiation of Ua. Since the inherent damping of DC motors is very low, the velocity signal va is also employed for damping of any control oscillations.
_ T~ - 8 -In order to achieve the shortest settiAg time for the rotary shutter with ~reselected maximum current the motor and thereby the rotary shutter are operated with essentially onstant accellaration and decellaration. With preselected ~U
___ the relationship vn = ~2a ~ U holds for the nominal velocity vn. "a" is a constant essentail proportional to the constant accellearation or decelleration,respectively . The above root function is formed in the root function generator 33~ The nominal velocity Vn is compared with the actual velocity v in unit 34 and the difference of both signals is fed to the drive motor 24 after amplification in unit 35.
Providing a new nominal voltage U accellerates the motor with maximum current until the velocity specified by the difference signal~ U, the root function generator and the control deviation is reached. Immediately thereafter follows braking with a nearly constant current as determined by the root function.
Details of the electric circuits are shown in Fig. 5 and Fig. 6.
The differential amplifier unit 31 comprises the operational amplifier IC1 and the resistors Rl to R4. The approximate formation of the root function vn - ~ occurs in the root function generator 33 via the resistive networks R6 to R14 and the diodes Dl to D4. The actual signal Ua corresponding to the momentary rotary shutter position is fed via line 37 to the differential unit 32 comprising the operational amplifier IC2, the capacitor Cl to C3 and the resistors R15 to R18. The unit 34 follows the differential unit 32 and the angle function generator 33 and forms the difference of vn and v . The unit 34 comprises _g_ an operational amplifier IC3, the resistors Rlg to R24 and the capacitor C4. The potentiometer Rlg and R22 are adjusted to provide optimal an initial transient for moving the rotary shutter into the nominal position. In order to avoid control oscillations at high frequencies the frequency dependence of the controller is compensated with capacitor C4.
The output signal of unit 34 is fed to amplifier unit 35.
This amplifier unit comprises a driving stage formed by the transistors Tl and T2 and a final stage formed by transistors T3 and T4. In order to avoid resonance in the control loop formed by 1~ T2, T3, T4, and the resistors R28 and R
the frequency dependence is compensated with t~le resistor R30 and the capacitor C6. The capacitor C5 prevents the transistors T3 and T4 from becoming simultaneously conducting when the amplifier is controlled with high frequencies. Based on this capacitative loading the operatïonal amplifier of unit 34 could start to oscillate. This is prevented by the damping resistor R27.¦
The connectors 38, 39 are connected to the driving motor 24 and the connectors 40, 41 are connected to a voltage source.
It thus will be seen that there is provided an automatic exposure system for pass through microfilm cameras which achieves the various objects of the invention and which is well adapted to practical use.
As various possible embodiments might be made of the above invention, and as various changes might be made in the embodiment above set forth, it is to be understood that all matter herein described or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.
The exposure control is provided by blocking a more or ¦less large part of the image beams by tilting the rotary shutter more or less into the image beam for varying the effective exposure time of a point on the continuously moving film according to the position of the rotary shutter. Unexpectedly, by employing of a motor driven rotary shutter very short setting times of slightly more than 10 milliseconds have been achieved in particular if the driving motor is provided with a bell type ~ 8623 'I
armatur and if the armature is connected with the shaft of the rotary shutter and forms the same axis, if the rotary shutter is built as a sandwich for better stability, if the rotary shutter is symmetrical with respect to the rotation axis and comprises two equal glued together wings with reinforcing fins parallel to the rotation axis. This results in a very low momentum of inertia of the rotary shutter and of the shutter drive. The forming and special construction of the rotary shutter provides a high rigidity for avoiding undesirable oscillati ~ns of the shutter system. In addition the direct action of the drive system on the shutter shaft provides an optimal power transmission between drive system and rotary shutter.
The inventionaccordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the apparatus hereinafter described and of which the scope of application will be indicated in the appended claims.
¦BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings in which is shown one of the various possible embodiments of the invention:
Fig. 1 is a view of a schematic diagram of the image beam path of a continuous microfilm camera;
Fig. 2 is a view showing the rotary shutter with drive motor and setting potentiometer;
Fig. 3 is a sectional view of the rotary shutter of ¦Fig. l;
i Fig. 4 is a view of a block diagram of the circuitry controlling the rotary shutter;
1~.186Z3 Fig. 5 is a view of a circuit of part of the block ; diagram of Fig. 4 in detail; and Fig. 6 is a view of a circuit of another part of the block diagram in Fig. 4 in detail.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The apparatus of the present invention comprises a locally fixed shutter for limiting the image beam path between original copies 1, 2, 3 and film 13, a rotary shutter 16 tiltable into the path of the beam defined by the locally fixed shutter; a drive motor 24 for tilting the rotary shutter, an angular detector for determining the momentary angular ( position and for generation of an actual signal, comparison ,~ circuitry 31 for comparing the actual signal with the nominal ~slgnal for generating of a corresponding correction signal, and means for controlling the drive motor with the correction signal as input.
, Referring now to Fig. 1 there are shown original copies 1, 2 and 3 to be microfilmed, which are carried by transport means (not shown) along a transport path in the direction of arrow A from an input station of a continuous microfilm pass through camera to an outgoing station. On the ~I transport path the original copies pass by a measurement station ), 4 for being illuminated with a lamp 5. A measuring device 6 comprising photoelectric elements measures the light reflected from the momentary original copy and allows determination of the brightness of the original copies. The original copies are illuminated for microfilming by lamps 14a and 14b. The scanning station 7 scans the reflected light in bands of the front and back sides of the momentary original copy and the front and back sides are imaged via surface mirrors 8, 9, 10, 11 and 12 onto the microfilm 13 running synchronously with the ~,~ .
---- ~
riginal ~opies into the direction of arrow ~. An imaging objective 15 focusses the image on the microfilm.
The rotation axis of a rotary shutter 16 is placed out-side of the image beam path 17, 18. Tilting the rotary shutter 16 out of its horizontal position results in a certain amount of image beam being blocked. The arrangement of the rotary shutter relative to the image heam path is shown in Fig. 3. The maximum width of the image beam path 17, 18 is determined by the slit width of the locally fixed shutter 19. When the shutter wings 161 and 162 are essentially in vertical position the image beam path is not influenced. When the rotary shutter 16 is tilted out of its vertical position more or less of the image beam path is blocked resulting in a change in the effective slit width as formed by locally fixed shutter 16 together with the rotary ;hutter. The length of the rotary shutter is 46 centimeters for imaging simultaneously the two beams 17, 18 having each a width corresponding to the width of A4 size. The rotary shutter has sadwich type construction and is additionally provided with reinfGrc~ing fins 161a, 161b, 161c, 162a, 162b and 162c running parallel to the rotation axis. This assures an extreme rigidity of the rotary shutter. The rigidity is indispensible for avoiding oscillations upon adjustment of its position. Such ¦oscillation would result in alternate bright and dark bands until the shutter comes completely to rest.
The shafts 21, 22 are attached to the cylindrical hollow space 163 ~ormed by the reinforcing fins 161b and 162b of the shutter wings 161 and 162. The shaft 21 is supported by the apparatus frame 23. The shaft 22 also forms the shaft for the driving motor 24. In order to keep the inertia of the shutter lllB623 and drive system as low as possible the motor is a direct current operated motor with bell type armature such as the direct current motor 3357/220 of Faulhaber Co., West-Germany. The bell type armature is connected to the shaft 22. The motor shaft 22 is coupled by bellows 25 to the precision potentiometer 26 for measuring the angular position of the motor and therewith the angle of the rotary shaft.
A functional diagram of the exposure automatic as disclosed is shown in Fig. 4. The light remission of the original copy to be microfilmed is measured with the photoelectric measuring device 6 and fed to an amplification and storage stage 30. The output of stage 30 is the nominal Un, which is fed into the input of a differential amplifier 31. The construction of such an amplification and storage stage 30 is for example disclosed in German paten application DT-OS 2 446 240 already mentioned hereinabove. The true momentary rotary shutter position is determined by potentiometer 26 operating as a voltage divider. The output voltage of the potentiometer is a measure for the angle position of the rotary shutter 16 and represents the actual voltage Ua. The Ua is entered into the other input of the differential amplifier 31. The output voltage QU provided by the differential amplifier 31 is proportional to the remaining adjustment of the tilting angle of the rotary shutter. A velocity signal va corresponding to the momentary angular velocity of the rotary shutter is required for bringing the motor 24 to the velocity vn specified by the nominal voltage Un. The values of this velocity va is formed by circuit 32 by differentiation of Ua. Since the inherent damping of DC motors is very low, the velocity signal va is also employed for damping of any control oscillations.
_ T~ - 8 -In order to achieve the shortest settiAg time for the rotary shutter with ~reselected maximum current the motor and thereby the rotary shutter are operated with essentially onstant accellaration and decellaration. With preselected ~U
___ the relationship vn = ~2a ~ U holds for the nominal velocity vn. "a" is a constant essentail proportional to the constant accellearation or decelleration,respectively . The above root function is formed in the root function generator 33~ The nominal velocity Vn is compared with the actual velocity v in unit 34 and the difference of both signals is fed to the drive motor 24 after amplification in unit 35.
Providing a new nominal voltage U accellerates the motor with maximum current until the velocity specified by the difference signal~ U, the root function generator and the control deviation is reached. Immediately thereafter follows braking with a nearly constant current as determined by the root function.
Details of the electric circuits are shown in Fig. 5 and Fig. 6.
The differential amplifier unit 31 comprises the operational amplifier IC1 and the resistors Rl to R4. The approximate formation of the root function vn - ~ occurs in the root function generator 33 via the resistive networks R6 to R14 and the diodes Dl to D4. The actual signal Ua corresponding to the momentary rotary shutter position is fed via line 37 to the differential unit 32 comprising the operational amplifier IC2, the capacitor Cl to C3 and the resistors R15 to R18. The unit 34 follows the differential unit 32 and the angle function generator 33 and forms the difference of vn and v . The unit 34 comprises _g_ an operational amplifier IC3, the resistors Rlg to R24 and the capacitor C4. The potentiometer Rlg and R22 are adjusted to provide optimal an initial transient for moving the rotary shutter into the nominal position. In order to avoid control oscillations at high frequencies the frequency dependence of the controller is compensated with capacitor C4.
The output signal of unit 34 is fed to amplifier unit 35.
This amplifier unit comprises a driving stage formed by the transistors Tl and T2 and a final stage formed by transistors T3 and T4. In order to avoid resonance in the control loop formed by 1~ T2, T3, T4, and the resistors R28 and R
the frequency dependence is compensated with t~le resistor R30 and the capacitor C6. The capacitor C5 prevents the transistors T3 and T4 from becoming simultaneously conducting when the amplifier is controlled with high frequencies. Based on this capacitative loading the operatïonal amplifier of unit 34 could start to oscillate. This is prevented by the damping resistor R27.¦
The connectors 38, 39 are connected to the driving motor 24 and the connectors 40, 41 are connected to a voltage source.
It thus will be seen that there is provided an automatic exposure system for pass through microfilm cameras which achieves the various objects of the invention and which is well adapted to practical use.
As various possible embodiments might be made of the above invention, and as various changes might be made in the embodiment above set forth, it is to be understood that all matter herein described or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.
Claims (10)
1. An automatic exposure system for continuous pass through microfilm cameras wherein the brightness of each of the original copies to be microfilmed is scanned individually by a scanning station and wherein the reference signal corresponding to the object brightness is employed for controlling the light intensity falling on the film comprising:
a rotary shutter capable of being tilted into the path of image beam between illuminated original copy and microfilm;
a drive motor for tilting the rotary shutter;
an angular detector coupled to the rotary shutter for determining the momentary angular position of the rotary shutter and for generating a corresponding actual signal Ua;
comparison means for comparing the actual signal with a nominal signal, based on the reference signal, for generating a correction signal; and control means for controlling the drive motor in accordance with the correction signal.
a rotary shutter capable of being tilted into the path of image beam between illuminated original copy and microfilm;
a drive motor for tilting the rotary shutter;
an angular detector coupled to the rotary shutter for determining the momentary angular position of the rotary shutter and for generating a corresponding actual signal Ua;
comparison means for comparing the actual signal with a nominal signal, based on the reference signal, for generating a correction signal; and control means for controlling the drive motor in accordance with the correction signal.
2. The automatic exposure system as set forth in claim 1 further comprising a locally fixed shutter for limiting the image beam width between object and film and for defining the path of the image beam in the vicinity of the rotary shutter.
3. The automatic exposure system as set forth in claim 1, wherein the drive motor acts directly on the shaft of the rotary shutter.
4. The automatic exposure system as set forth in claim 1, wherein the drive motor is a DC motor of low rotary inertia.
5.The automatic exposure system as set forth in claim 4, wherein the motor has a bell type armature and the armature of the motor is connected to the shaft of the rotary shutter forming one single axis.
6. The automatic exposure system as set forth in claim 1, wherein the angular detector is a potentiometer having the same axis as the rotary shutter and being mounted on the same shaft.
7. The automatic exposure system as set forth in claim 1, wherein the construction of the rotary shutter is of sandwich type.
8. The automatic exposure system as set forth in claim 1, wherein the rotary shutter is essentially of 2-fold, 3-fold or 4-fold rotation symmetry.
9. The automatic exposure system as set forth in claim 8, wherein the rotary shutter comprises two equal wings glued together.
10. The automatic exposure system as set forth in claim 9, wherein the wings are reinforced by fins parallel to the axis of the rotary shutter.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2746990A DE2746990C2 (en) | 1977-10-19 | 1977-10-19 | Automatic exposure for microfilm recorders |
| DEP2746990.5-51 | 1977-10-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1118623A true CA1118623A (en) | 1982-02-23 |
Family
ID=6021793
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000313744A Expired CA1118623A (en) | 1977-10-19 | 1978-10-19 | Automatic exposure system for pass through microfilm cameras |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA1118623A (en) |
| DE (1) | DE2746990C2 (en) |
| FR (1) | FR2406837A1 (en) |
| GB (1) | GB2010507B (en) |
| IT (1) | IT1106213B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2938925C2 (en) * | 1979-09-26 | 1985-01-17 | Agfa-Gevaert Ag, 5090 Leverkusen | Device for exposure control in a microfilm continuous recorder |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE637355C (en) * | 1932-07-29 | 1936-10-27 | Kodak A G | Optical copier |
| DE1056920B (en) * | 1957-11-07 | 1959-05-06 | Soennecken Fa F | Device for automatic, electronically controlled exposure control for microfilm flow devices |
| DE1214524B (en) * | 1965-03-22 | 1966-04-14 | Mikrofilm G M B H | Method and device for practicing the same for automatic exposure control in microfilm cameras |
| DE2046887C3 (en) * | 1970-09-23 | 1979-02-22 | Agfa-Gevaert Ag, 5090 Leverkusen | Device for controlling the exposure of a recording or copying material in two colors |
| DE2446240A1 (en) * | 1974-09-27 | 1976-04-08 | Agfa Gevaert Ag | MICRO-RECORDING DEVICE |
| DE2552589A1 (en) * | 1975-11-24 | 1977-05-26 | Agfa Gevaert Ag | DEVICE FOR AUTOMATIC EXPOSURE CONTROL IN MICROFILM CURRENT CAMERAS |
-
1977
- 1977-10-19 DE DE2746990A patent/DE2746990C2/en not_active Expired
-
1978
- 1978-10-06 FR FR7828633A patent/FR2406837A1/en active Granted
- 1978-10-17 IT IT51536/78A patent/IT1106213B/en active
- 1978-10-19 CA CA000313744A patent/CA1118623A/en not_active Expired
- 1978-10-19 GB GB7841148A patent/GB2010507B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2746990B1 (en) | 1979-03-01 |
| IT7851536A0 (en) | 1978-10-17 |
| FR2406837B1 (en) | 1984-12-28 |
| FR2406837A1 (en) | 1979-05-18 |
| DE2746990C2 (en) | 1979-10-25 |
| IT1106213B (en) | 1985-11-11 |
| GB2010507A (en) | 1979-06-27 |
| GB2010507B (en) | 1982-05-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |