Linear exposure control system

• US 4,113,378 A
• Filed: 03/02/1977
• Issued: 09/12/1978
• Est. Priority Date: 03/02/1977
• Status: Expired due to Term

• Current Assignee: A.B. Dick Company (MAI Holdings, Inc.)
• Original Assignee: ITEQ Corporation
• Inventors: Wirtz, John Stanley
• Primary Examiner(s): Hix, L. T.
• Assistant Examiner(s): Brady, W. J.
• Application Number:
  US05/773,568
• Time in Patent Office: 559 Days
• Field of Search: 355/67-71, 355/35, 355/38, 355/55, 355/83
• US Class Current: 355/55
• CPC Class Codes: G03B 27/722 when the reproduction scale is changed

Abstract

A magnification signal of 64 - 100% is applied as an input parameter to a specially designed relaxation oscillator which produces a pulse train wherein the pulses thereof have a duration which vary in linear fashion with respect to the magnification input signal, the relaxation oscillator employing a constant current source in series relationship with an integrating capacitor which produces a saw tooth signal having a slope which is constant regardless of variations in the amplitude of the magnification input signal. The output pulses from the relaxation oscillator are counted to define an exposure control interval which changes linearly with respect to the input magnification signal.

Claims

1. In an exposure control system for varying the exposure of an object to be photographed in linear fashion as a function of changes in magnification of the image of said object focused upon a photo-sensitive medium, the improvement comprising:

a. movable lens means;

b. a lens actuator for mechanically changing the position of said lens means for producing changes in magnification;

c. magnification signal generating means for producing a magnification signal proportional to the position of said lens actuator;

d. integration signal generating means for producing an integrated signal upon being actuated having a linear slope regardless of variations of said magnification signal;

e. reference signal generating means;

f. comparator means for assuming a first state when the signal applied to one input terminal thereof is greater than the signal applied to the other input terminal thereof, and for assuming a second state when the signal applied to the one input terminal thereof is less than the signal applied to the other input terminal thereof, said comparator means connected to compare the amplitudes of the signal produced by said integration signal generating means and said magnification signal generating means during a first interval and comparing the signal produced by said integration signal generating means and said reference signal generating means during a second interval, output pulses being produced by said comparator for each change of said comparator from said first state to said second state;

g. switch means coupling said integration signal generating means and said magnification signal generating means to said comparator during a first interval and deactuating said integration signal generating means while coupling said reference signal generating means to said comparator during a second interval for referencing said integration signal generating means, thereby to cause said comparator to revert from said second state back to said first state and for thereafter causing said comparator to again compare the signal produced by said magnification signal generating means with the signal produced by said integrator; and

h. counter means for counting the pulses produced by said comparator and for producing an output signal when the count thereof reaches a predetermined value, said output signal being utilized to terminate said exposure of said object.

2. The combination as set forth in claim 1 wherein said integration signal generating means includes a capacitor and a constant current source coupled thereto for charging said capacitor.

3. The combination as set forth in claim 2 further including switch means for discharging said capacitor during said second interval.

4. In an exposure control system for varying the exposure of an object to be photographed in linear fashion as a function of changes in magnification of the image of said object focused upon a photo-sensitive medium, the improvement comprising:

a. movable lens means;

b. a lens actuator for mechanically changing the position of said lens means for producing changes in magnification;

c. magnification signal generating means for producing a magnification signal linearly proportional to the position of said lens actuator;

d. integration signal generating means for producing an integrated signal upon being actuated having a linear slope, and including an integrator together with a constant current source for charging said integrator during a first interval for maintaining the slope of said integration signal produced by said integration signal generator constant, regardless of variations of said magnification signal;

e. reference signal generating means;

f. comparator means for assuming a first state when the signal applied to one input terminal thereof is greater than the signal applied to the other input terminal thereof, and for assuming a second state when the signal applied to the one input terminal thereof is less than the signal applied to the other input terminal thereof, said comparator means connected to compare the amplitudes of the signal produced by said integration signal generating means and said magnification signal generating means during a first interval and comparing the signal produced by said integration signal generating means and said reference signal generating means during a second interval, output pulses being produced by said comparator for each change of said comparator from said first state to said second state;

g. switch means responsive to said first state of said comparator coupling said integration signal generating means and said magnification signal generating means to said comparator during said first interval and deactuating said integration signal generating means while coupling said reference signal generating means to said comparator during said second interval for referencing said integrator of said integration signal generating means, thereby to cause said comparator to revert from said second state back to said first state and for thereafter causing said comparator to again compare the signal produced by said magnification signal generating means with the signal produced by said integration signal generating means; and

h. counter means for counting the pulses produced by said comparator and for producing an output signal when the count thereof reaches a predetermined value, said output signal being utilized to terminate said exposure of said object.

5. The combination as set forth in claim 4 wherein said integration signal generating means includes a capacitor and a constant current source coupled in series therewith for charging said capacitor during said first interval.

6. The combination as set forth in claim 5 further including switch means for discharging said capacitor during said second interval.

7. In an exposure control system for varying the exposure of an object to be photographed in linear fashion as a function of changes in magnification of the image of said object focused upon a photo-sensitive medium, the improvement comprising:

a. movable lens means;

b. a lens actuator for mechanically changing the position of said lens means for producing changes in magnification from about 64% to 100%;

c. magnification signal generating means for producing a magnification signal linearly proportional to the position of said lens actuator;

d. integration signal generating means for producing an integrated signal upon being actuated having a linear slope, and including an integrator together with a constant current source for charging said integrator during a first interval for maintaining the slope of said integration signal produced by said integration signal generator constant, regardless of variations of said magnification signal;

e. reference signal generating means;

f. comparator means for assuming a first state when the signal applied to one input terminal thereof is greater than the signal applied to the other input terminal thereof, and for assuming a second state when the signal applied to the one input terminal thereof is less than the signal applied to the other input terminal thereof, said comparator means connected to compare the amplitudes of the signal produced by said integration signal generating means and said magnification signal generating means during a first interval and for comparing the signal produced by said integration signal generating means and said reference signal generating means during a second interval, output pulses being produced by said comparator for each change of said comparator from said first state to said second state;

g. switch means responsive to said first state of said comparator for coupling said integration signal generating means and said magnification signal generating means to said comparator during said first interval and for deactuating said integration signal generating means while coupling said reference signal generating means to said comparator during a second interval for referencing said integrator of said integration signal generating means, thereby to cause said comparator to revert from said second state back to said first state and for thereafter causing said comparator to again compare the signal produced by said magnification signal generating means with the signal produced by said integrator; and

h. counter means for counting the pulses produced by said comparator and for producing an output signal when the count thereof reaches a predetermined value, said output signal being utilized to terminate said exposure of said object.

8. The combination as set forth in claim 7 wherein said integration signal generating means includes a capacitor and a constant current source coupled in series therewith for charging said capacitor.

9. The combination as set forth in claim 8 further including switch means for discharging said capacitor during said second interval.

10. In an exposure control system for varying the exposure of an object to be photographed in linear fashion as a function of changes in magnification of the image of said object focused upon a photo-sensitive medium, the improvement comprising:

a. movable lens means;

b. a lens actuator for mechanically changing the position of said lens means for producing changes in magnification from about 64% to 100%;

c. magnification signal generating means for producing a magnification signal linearly proportional to the position of said lens actuator;

d. integration signal generating means for producing an integrated signal upon being actuated having a linear slope, and including an integrator together with a constant current source for charging said integrator during a first interval for maintaining the slope of said integration signal produced by said integration signal generator constant, regardless of variations of said magnification signal;

e. reference signal generating means;

f. comparator for assuming a first state during a first interval and a second state during a second interval;

g. switch means responsive to the state of said comparator causing said comparator to compare the output signal produced by said integration signal generating means with the output signal produced by said magnification signal generating means during said first interval until the signals applied to said comparator by said integration signal generating means and said magnification signal generating means crossover with respect to each other for causing said comparator to revert to said second state, and for causing said comparator to compare the reference signal produced by said reference signal generating means with the changing signal produced by said integrator of said integration signal generating means due to deactuation of said integrator by said switch means during said second interval until the signals applied to said comparator again crossover with respect to each other, which in turn causes said comparator to revert from said second state back to said first state to repeat comparison of the signal produced by said integration signal generating means and said magnification signal generating means, thereby to cause said comparator to produce a series of pulses; and

h. counter means coupled to said comparator for counting said pulses produced by said comparator and for producing an output signal when the count thereof reaches a predetermined value, said output signal being utilized to terminate said exposure of said object.

11. In an exposure control system for varying the exposure of an object to be photographed in linear fashion as a function of changes in magnification of the image of said object focused upon a photo-sensitive medium, the improvement comprising:

a. movable lens means;

b. a lens actuator for mechanically changing the position of said lens means for producing changes in magnification from about 64% to 100%;

c. magnification signal generating means for producing a magnification signal linearly proportional to the position of said lens actuator;

d. integration signal generating means for producing an integrated signal upon being actuated having a linear slope, and including an integrator together with a constant current source for charging said integrator during a first interval for maintaining the slope of said integration signal produced by said integration signal generator constant, regardless of variations of said magnification signal;

e. reference signal generating means;

f. a comparator having a first and second input circuit and an output circuit, said comparator assuming a first state when the signal applied to said first input circuit is greater than the signal applied to said second input circuit and a second state when the signal applied to said first input circuit is less than the signal applied to said second input circuit, output pulses being produced by said comparator for each change of said comparator from said first state to said second state;

g. an integrator control switch for causing said integrator to integrate the current produced by said constant current source when said integrator control switch is opened and for deactuating said integrator when said integrator control switch is closed;

h. an interval control switch for coupling said magnification signal generating means to said second input circuit of said comparator when said interval control switch is closed;

i. a reference voltage switch for coupling said reference signal generating means to said second input circuit of said comparator when said reference voltage switch is closed; and

j. switching means coupled to the output circuit of said comparator for opening said integrator control switch and said reference control switch while closing said interval control switch during said first interval thereby to cause said comparator to compare the signal produced by said integration signal generating means with said magnification signal generating means during said first interval and to cause said integrator control switch and said reference voltage switch to be closed and said interval control switch to be opened during said second interval thereby to deactuate said integrator with respect to the reference signal produced by said reference signal generating means during said second interval; and

k. counter means coupled to said comparator for counting said pulses produced by said comparator and for producing an output signal when the count thereof reaches a predetermined value, said output signal being utilized to terminate said exposure of said object.

12. The combination as set forth in claim 11 wherein said integrator comprises a capacitor and said integrator control switch is coupled thereto to cause said capacitor to discharge upon being closed;

13. The combination as set forth in claim 12 wherein the output circuit of said comparator is coupled to the control terminals of said integrator control switch and said reference voltage switch and further including inverter means having an input circuit coupled to the output circuit of said comparator and an output circuit and means coupled between the output circuit of said inverter and the control terminal of said interval control switch for causing said interval control switch to be closed when said integrator control switch and said reference voltage switch are opened and vice versa.