Automatic focusing camera

In a camera having a lens mount displaceable through a distance M between a pair of terminal positions with the distance from one terminal position to a location at which a subject at range R is in focus being defined as the distance N, said distance N being a predetermined function of R, and having range-finding means for generating a range signal whose timed duration is directly proportional to R thereby establishing a relationship between R and time, the improvement comprising:

• pulse generator means responsive to the start of a range signal for generating a train of pulses whose repetition rate varies during said range signal as the time-derivative of at least an approximation of the function relating N to R;
• a first counter for accummulating pulses from said pulse generator means during said range signal whereby the total number of pulses transmitted to said first counter is kN where k is a constant;
• and
• drive means for displacing said lens mount in accordance with the contents of said first counter.

In a camera having a shutter mechanism, and having a lens mount with a predetermined lens/subject function that relates the axial position of the lens mount at which a subject is in focus to the distance to the subject, the improvement comprising:

• keyable range finding means having an acoustic transponder for ascertaining the distance to a subject and responsive to keying for generating a range pulse whose duration is directly related to the subject distance thereby establishing a relationship between subject distance and time;
• a pulse generator with a programmed time-variable pulse repetition frequency responsive to the start of the range pulse for generating a train of pulses whose repetition rate varies as the time-derivative of at least an approximation of the lens/subject function;
• counter means for accumulating the pulses produced by said pulse generator during said range pulse duration;
• and
• drive means for displacing said lens mount in accordance with the contents of said counter.

An automatic focusing camera having a shutter mechanism, said camera comprising:

• a displaceable lens having a predetermined lens/subject function that relates the position of said lens, at which a subject is in focus, to the subject distance;
• means responsive to keying for generating a range pulse whose duration is directly related to the distance of a given subject;
• pulse generator means including a pulse generator with a programmed time-variable pulse repetition frequency, and a counter for accumulating pulses of said pulse generator, the programmed repetition rate of said pulse generator varying with time in accordance with the time derivative of at least an approximation of said predetermined lens/subject function, whereby the contents of said counter, at the end of said range pulse, is representative of the axial position of said lens at which said given subject will be in focus;
• and
• drive means actuatable for displacing said lens in accordance with the contents of said counter.

An automatic focusing camera comprising:

• means for defining a focal plane;
• an objective lens;
• means for mounting said lens for movement to respective focal positions wherein subjects at various distances from said camera are in focus at said focal plane, said focal positions of said lens being related to said subject distances by a predetermined non-linear lens/subject function;
• means for providing a subject range parameter as a linear function of subject distance;
• means for converting said range parameter to a lens parameter related to a focal position in a series of successive linear steps approximately said non-linear lens/subject function, said converting means including a pulse generator for producing a train of pulses and means for storing said pulses, said pulse generator being programmed at a different pulse repetition rate for each of said successive steps, said lens parameter being the total number of stored pulses;
• and
• means actuatable for displacing said lens to a focal position in accordance with said lens parameter, said displacing means including means for displacing said lens a fixed amount for each stored pulse.

A process of focusing a photographic camera comprising the steps of:

• propagating at least one pulse of energy at the subject to be photographed;
• timing the difference between the start of said propagation and the return of an echo signal from said subject;
• forming and storing pulses during said timing step at successive scaled rates providing linear steps approximating the relation between lens position and subject distance such that the number of stored pulses is representative of the lens position at which said subject is in focus;
• and
• displacing said lens to a focal position corresponding to the number of pulses stored during said forming and storing step.

In a camera having a displaceable lens for focusing image carrying rays from a subject on the camera focal plane, the position of said lens at which a subject is in focus being a predetermined non-linear function of subject distance, and having range finding means for generating a range parameter representative of subject distance, the improvement comprising:

• a first pulse generator responsive to said range parameter for generating a train of pulses whose number is representative of subject distance;
• means for converting displacement of said lens to a linear focus parameter, said converting means including a second pulse generator coupled to said lens for producing upon displacement therof a train of pulses whose number is representative of the position of said lens at which a given subject distance is in focus, said second pulse generator having a variable pulse repetition rate preprogrammed to provide a pulse for each displacement of said focusing means required per unit change in subject focus;
• means for displacing said lens;
• and
• means for evaluating the total number of said pulses in said pulse train and said pulses produced by said second pulse generator and for terminating displacement of said lens when said pulse generator produces a pulse count indicating that said lens is positioned in accordance with said range parameter.

In a camera having a displaceable lens for focusing image carrying rays from a subject on the camera focal plane, the position of said lens at which a subject is in focus being a predetermined non-linear function of subject distance, and having actuatable range finding means for generating a linear range parameter of timed duration representative of subject distance, the improvement comprising:

• means responsive to said range parameter for generating a train of pulses whose number is representative of the position of said lens at which said subject will be in focus, said pulse generating means including a first counter for accumulating said pulses of said pulse train and a pulse generator with a time-variable pulse repetition rate preprogrammed to approximate said non-linear function such that the contents of said first counter, at the end of said range pulse, is representative of the position of said lens at which said subject will be in focus;
• means indicative of the just previous position of said lens assembly, said indicative means including a second counter whose content is representative of said previous position of said lens assembly;
• means for determining the difference in content between said first and second counters;
• and
• means for displacing said lens in accordance with said difference in content between said counters so as to position said lens in accordance with said range parameter.