Optical system position controlling device

Claim 2

An optical system having a controlling device therefor and comprising: an image forming fixed optical system for forming an image of the object to be photographed; a light splitting means for splitting a light beam passed through said image forming fixed optical system from the object to be photographed into a first and second light beam; an image forming movable optical means disposed behind said light splitting means and having an optical axis in alignment with the optical axis of said first light beam, said image forming movable optical means being movable along its optical axis for varying its focusing position; a position controlling means for controlling the position of said image forming movable optical means, said position controlling means including a position detecting means for detecting the position of the image of the object formed by said image forming fixed optical system, said detecting means being movable in said second light beam to detect the position of the image of said object in accordance with the brightness of light gathered from the object, an image forming movable optical system shifting means for controlling the movement of said image forming movable optical means, said image forming movable optical system Shifting means being controlled by an output signal from said position detecting means, whereby said image forming movable optical means is moved along its optical axis, so that the object light beam passed therethrough and through said image forming fixed optical system forms the object image at a predetermined position.

Claim 3

An optical system according to claim 1, wherein said position detecting means has a light receiving surface inclined with respect to the optical axis of said second light beam and moves across said second light beam in a direction approximately perpendicular to the optical axis of the second light beam.

Claim 4

An optical system according to claim 2, wherein said light receiving surface of said position detecting means is provided with a photosensitive element.

Claim 5

An optical system according to claim 3, wherein said light receiving portion of said position detecting means is provided with a plurality of photosensitive elements.

Claim 6

An optical system according to claim 2, wherein said image forming movable optical system shifting means includes a pulse motor.

Claim 7

An optical system according to claim 1, wherein said position detecting means includes a signal generating means for detecting the brightness of light from the object and producing an output signal in correspondence with said brightness of object light, and a signal comparing means for comparing the output signal of said signal generating means with a reference signal, said signal comparing means being electrically connected to said image forming movable optical system shifting means to control said movable image forming optical system shifting means in correspondence with a difference between said reference signal and said output signal of said signal generating means.

Claim 8

An optical system according to claim 6, wherein said image forming movable optical system shifting means is electrically connected to said signal comparing means and is provided with a motor mechanically linked to said image forming movable optical means.

Claim 9

An optical system according to claim 7, wherein said motor is a pulse motor.

Claim 10

An optical system according to claim 1, whereidn said photomeasuring means is provided with an alarm means for alarm indication in case the object light quantity is below a predetermined value.

Claim 11

An optical system having a position controlling device therefor and comprising: a image forming fixed optical system for forming an image of the object to be photographed; a light splitting means for splitting the light beam passed through said image forming fixed optical system from the object to be photographed into a first and second light beam; a light regulating means provided between said image forming fixed optical system and said light splitting means and for controlling the light quantity provided to said light splitting means; a photomeasuring means for measuring the light quantity passed through said image forming fixed optical system and controlling said light regulating means in accordance with said light quantity, said photomeasuring means being selectively located in said second light beam; an image forming movable optical means disposed behind said light splitting means and having an optical axis in alignment with the optical axis of said first light beam, said image forming movable optical means being movable along the optical axis of said first light beam for varying the focusing position, and a position controlling means for controlling the position of said image forming movable optical system, said position controlling means including: a position detecting means for detecting the position of the image of the object formed by said image forming fixed optical system, said position detecting means being movable in said second light beam to detect the position of said image in accordance with the brightness, and an image forming movable optical system shifting means for controlling the movement of said image forming movable opTical means, said shifting means being controlled in accordance with an output signal of said position detecting means, whereby said image forming movable optical means is movable along its optical axis so that the light beam passed therethrough and through said image forming fixed optical system is focused at a predetermined position with constant light quantity.

Claim 12

An optical system having a position controlling device therefor and comprising: a image forming fixed optical system for forming an image of the object to be photographed; a light splitting means for splitting the light beam passed through said image forming fixed optical system from the object to be photographed into a first and second light beam; a light regulating means provided between said image forming fixed optical system and said light splitting means and for controlling the light quantity provided to said light splitting means; a photomeasuring means for measuring the light quantity passed through said image forming fixed optical system and controlling said light regulating means in accordance with said light quantity, said photomeasuring means being selectively located in said second light beam; an image forming movable optical means disposed behind said light splitting means and having an optical axis in alignment with the optical axis of said first light beam, said image forming movable optical means being movable along the optical axis of said first light beam for varying the focusing position, and a position controlling means for controlling the position of said image forming movable optical system, said position controlling means including: a position detecting means for detecting the position of the image of the object formed by said image forming fixed optical system, said position detecting means being movable in said second light beam to detect the position of said image in accordance with the brightness, and an image forming movable optical system shifting means for controlling the movement of said image forming movable opTical means, said shifting means being controlled in accordance with an output signal of said position detecting means, whereby said image forming movable optical means is movable along its optical axis so that the light beam passed therethrough and through said image forming fixed optical system is focused at a predetermined position with constant light quantity.

Claim 13

An optical system according to claim 10, wherein said position detecting means is provided with a light receiving surface inclined with respect to the optical axis of said second light beam and is movable across in said second light beam.

Claim 14

An optical system according to claim 11, wherein said light receiving surface of said position detecting means is provided with a light sensitive element.

Claim 15

An optical system according to claim 12, wherein said photomeasuring means has a biasing light emitting means for emitting a bias light to said light receiving surface of said position detecting means in a case where the light quantity from the object is below a predetermined value.

Claim 16

An optical system according to claim 11, wherein said position detecting means and said photomeasuring means cooperatively and successively move across said second light beam in a direction of movement approximately perpendicular to the optical axis of said second light beam.

Claim 17

An optical system according to claim 14, wherein said photomeasuring means is provided with a memory means for memorizing temporarily an object light quantity information.

Claim 18

An optical system having a position controlling device therefor and comprising: an image forming fixed optical system for forming an image of an object to be photographed; a light splitting means for splitting the light beam passed through the image forming fixed optical system from the object to be photographed into a first and a second beam; a trigger means for activating said optical system position controlling device, the trigger means selectively taking a first and a second position; a light regulating means for controlling the light quantity passing through said image forming fixed optical system, said light regulating means being arranged between said image forming fixed optical system and said light splitting means; a photomeasuring means for measuring the light quantity passed through said image forming fixed optical system and controlling said light regulating means in correspondence with said light quantity, said photomeasuring means being selectively arranged in said first light beam; a memory means for memorizing temporarily an object light quantity information measured by said photomeasuring means; an image forming movable optical means being arranged behind said light splitting means and having an optical axis in alignment with the optical axis of said second optical beam, said image forming movable optical means being movable along its optical axis so as to vary the focusing position; an image forming movable optical system shifting means for controlling the movement of said image forming movable optical means, said image forming movable optical system shifting means being mechanically linked with said image forming movable optical means; a controlling means for controlling said image forming movable optical system shifting means, said control means comprising a driving means driven selectively by said trigger means, said driving means effecting a driving action when said trigger means is in said first position and effecting no driving action when said trigger means is in said second position; a position detecting means for detecting the position of the object image formed by said fixed optical system, said detecting means being mechanically linked with said driving means to be movable in said first light beam by said driving means and being provided with a signal producing means for producing a signal corresponding to the brightness of said object image; a comparing means for comparing a Signal from said signal producing means with a reference signal, said comparing means generating a signal which releases the memorizing operation of said memory means, whereby said image forming movable optical means is moved along its optical axis so that the object rays passed through said image forming fixed optical system forms the object image at a constant light quantity in a predetermined position.

Claim 19

An optical system having a position controlling device therefor and comprising: an image forming fixed optical system for forming an image of an object to be photographed; a light splitting means for splitting the light beam passed through the image forming fixed optical system from the object to be photographed into a first and a second beam; a trigger means for activating said optical system position controlling device, the trigger means selectively taking a first and a second position; a light regulating means for controlling the light quantity passing through said image forming fixed optical system, said light regulating means being arranged between said image forming fixed optical system and said light splitting means; a photomeasuring means for measuring the light quantity passed through said image forming fixed optical system and controlling said light regulating means in correspondence with said light quantity, said photomeasuring means being selectively arranged in said first light beam; a memory means for memorizing temporarily an object light quantity information measured by said photomeasuring means; an image forming movable optical means being arranged behind said light splitting means and having an optical axis in alignment with the optical axis of said second optical beam, said image forming movable optical means being movable along its optical axis so as to vary the focusing position; an image forming movable optical system shifting means for controlling the movement of said image forming movable optical means, said image forming movable optical system shifting means being mechanically linked with said image forming movable optical means; a controlling means for controlling said image forming movable optical system shifting means, said control means comprising a driving means driven selectively by said trigger means, said driving means effecting a driving action when said trigger means is in said first position and effecting no driving action when said trigger means is in said second position; a position detecting means for detecting the position of the object image formed by said fixed optical system, said detecting means being mechanically linked with said driving means to be movable in said first light beam by said driving means and being provided with a signal producing means for producing a signal corresponding to the brightness of said object image; a comparing means for comparing a Signal from said signal producing means with a reference signal, said comparing means generating a signal which releases the memorizing operation of said memory means, whereby said image forming movable optical means is moved along its optical axis so that the object rays passed through said image forming fixed optical system forms the object image at a constant light quantity in a predetermined position.

Claim 20

An optical system having a position controlling device therefor and comprising: a image forming fixed optical system for forming an image of the object to be photographed; a light splitting means for splitting the light beam passed through said image forming fixed optical system from the object to be photographed into a first and a second optical beam; a trigger member for activating the position controlling device of said optical system, the trigger member being arranged for displacement between a first and a second position; a light regulating means arranged between said image forming fixed optical system and said splitting means and for controlling the light quantity provided to said light light splitting means; a photomeasuring means being provided for selective movement into said first light beam from a starting position for measuring the object light quantity passed through said image forming fixed optical system and controlling said light regulating means in correspondence with said object light quantity; a memory means for memorizing temporarily an object light quantity information obtained by the photometry of said photomeasuring means; an image forming movable optical means arranged behind said light splitting means and having an optical axis which is in alignment with the optical axis of said second light beam, said image forming movable optical means being movable along its optical axis from a starting position to vary the focusing position; an image forming movable optical system shifting means for controlling the movement of said image forming movable optical means, said image forming movable optical means being mechanically linked with said image forming fixed optical means; a controlling means for controlling said image forming movable optical system shifting means, said controlling means including a driving means being selectively driven by said trigger member, in such a manner that said driving means effects a driving action when said trigger member is in said first position and effects no driving action when said trigger member is in said second position, a position detecting means for detecting the position of the object image formed by said image forming fixed optical system, said detecting means being mechanically linked with said driving means to thereby move from a starting position into said first light beam in a direction approximately perpendicular to the optical axis of said first light beam, and said position detecting means having a light receiving surface inclined with respect to the optical axis of the first light beam and having a signal generating means for generating a signal in correspondence with the brightness of the object image, and a comparing means for comparing the signal generated by said signal generating means with a reference signal, said comparing means generating a signal which releases the memorizing operation of the memory means and also a signal controlling said controlling means when the compared signals reach a predetermined magnitude relation; a biasing light emitting means for emitting a biasing light to said signal generating means when the object light quantity measured by said photomeasuring means is below a predetermined value; a reset means for resetting said photomeasuring means, said movable optical means and said position detecting meeans to their respective starting positions, said reset means being arranged for actuation in cooperation with said trigger member when said trigger member is moved from said second to said first posiTion.

Claim 21

An optical system having a position controlling device therefor and comprising: a image forming fixed optical system for forming an image of the object to be photographed; a light splitting means for splitting the light beam passed through said image forming fixed optical system from the object to be photographed into a first and a second optical beam; a trigger member for activating the position controlling device of said optical system, the trigger member being arranged for displacement between a first and a second position; a light regulating means arranged between said image forming fixed optical system and said splitting means and for controlling the light quantity provided to said light light splitting means; a photomeasuring means being provided for selective movement into said first light beam from a starting position for measuring the object light quantity passed through said image forming fixed optical system and controlling said light regulating means in correspondence with said object light quantity; a memory means for memorizing temporarily an object light quantity information obtained by the photometry of said photomeasuring means; an image forming movable optical means arranged behind said light splitting means and having an optical axis which is in alignment with the optical axis of said second light beam, said image forming movable optical means being movable along its optical axis from a starting position to vary the focusing position; an image forming movable optical system shifting means for controlling the movement of said image forming movable optical means, said image forming movable optical means being mechanically linked with said image forming fixed optical means; a controlling means for controlling said image forming movable optical system shifting means, said controlling means including a driving means being selectively driven by said trigger member, in such a manner that said driving means effects a driving action when said trigger member is in said first position and effects no driving action when said trigger member is in said second position, a position detecting means for detecting the position of the object image formed by said image forming fixed optical system, said detecting means being mechanically linked with said driving means to thereby move from a starting position into said first light beam in a direction approximately perpendicular to the optical axis of said first light beam, and said position detecting means having a light receiving surface inclined with respect to the optical axis of the first light beam and having a signal generating means for generating a signal in correspondence with the brightness of the object image, and a comparing means for comparing the signal generated by said signal generating means with a reference signal, said comparing means generating a signal which releases the memorizing operation of the memory means and also a signal controlling said controlling means when the compared signals reach a predetermined magnitude relation; a biasing light emitting means for emitting a biasing light to said signal generating means when the object light quantity measured by said photomeasuring means is below a predetermined value; a reset means for resetting said photomeasuring means, said movable optical means and said position detecting meeans to their respective starting positions, said reset means being arranged for actuation in cooperation with said trigger member when said trigger member is moved from said second to said first posiTion.

Claim 22

An optical system according to claim 17, wherein said photomeasuring means is provided with an alarm means for alarm indication when the object light quantity is below a predetermined value.

Claim 23

An optical system according to claim 17, wherein said photomeasuring means and said position detecting means are integrally formed so as to be movable together.

Claim 24

An optical system having a position controlling device therefor and comprising: an image forming optical system for forming an image of the object to be photographed, said optical system being movable selectively along its optical axis; a light splitting means for splitting the light beam passed through said optical system from the object to be photographed into a first and a second light beam, said first light beam passing through a desired image forming plane on which said image forming optical system is allowed to form the object image; a position controlling means for controlling said selective movement of said image forming optical system, said position controlling means including a position detecting means for detecting the position of the object image formed by said image forming optical system, said position detecting means being selectively movable into said second beam split off by said splitting means to detect the image position in accordance with the brightness of an object image in said second light beam, an indicating means controlled in correspondence with an output signal of said position detecting means to determine the desired position of said image forming optical system, and a driving means for displacing said image forming optical system to said position determined by said indicating means, said driving means being selectively controlled in response to the output signal of the position detecting means, whereby said image forming optical means is moved along its optical axis so that the light rays passed through said optical system form the object image on said image forming plane.

Claim 25

An optical system having a position controlling device therefor and comprising: an image forming optical system for forming an image of the object to be photographed, said optical system being movable selectively along its optical axis; a light splitting means for splitting the light beam passed through said optical system from the object to be photographed into a first and a second light beam, said first light beam passing through a desired image forming plane on which said image forming optical system is allowed to form the object image; a position controlling means for controlling said selective movement of said image forming optical system, said position controlling means including a position detecting means for detecting the position of the object image formed by said image forming optical system, said position detecting means being selectively movable into said second beam split off by said splitting means to detect the image position in accordance with the brightness of an object image in said second light beam, an indicating means controlled in correspondence with an output signal of said position detecting means to determine the desired position of said image forming optical system, and a driving means for displacing said image forming optical system to said position determined by said indicating means, said driving means being selectively controlled in response to the output signal of the position detecting means, whereby said image forming optical means is moved along its optical axis so that the light rays passed through said optical system form the object image on said image forming plane.

Claim 26

An optical system according to claim 20, wherein said position detecting means has a light receiving surface inclined with respect to the axis of said second light beam and movable across said second light beam in approximately perpendicular direction to the optical axis of said second light beam.

Claim 27

An optical system according to claim 21, wherein said light receiving surface is provided with a plurality of the photosensitive elements.

Claim 28

An optical system according to claim 20, wherein said position detecting means includes a signal generating means which detects the brightness of the object and generates an output signal in correspondence with said object brightness, and a signal comparing means for comparing the signal from said signal generating means with a reference signal, said signal comparing means being electrically connected to said driving means to control said driving means in response to a difference between the signal from said signal generating means and the reference signal.

Claim 29

An optical system according to claim 23, wherein said driving means is electrically connected to said signal comparing means and has a motor mechanically linked with said driving means.

Claim 30

An optical system having a position controlling device therefor and comprising: an image forming optical system for forming an image of the object to be photographed, aid image forming optical system being movable selectively along its optical axis; a light splitting means for splitting the light beam passed through said optical system from the object to be photographed into a first and a second light beam; a light regulating means disposed between said image forming optical system and said light splitting means, said regulating means controlling the light quantity provided to said light splitting means; a photomeasuring means for measuring the object light quantity passed through said image forming optical system and controlling said light regulating means in correspondence with said object light quantity, said photomeasuring means being selectively movable in said second light beam, and a position controlling means for controlling the selectively moved position of said image forming optical system, said position controlling means including a position detecting means for detecting the position of the focused image formed by said image forming optical system, said position detecting means being selectively movable in said second light beam and detecting the focused position according to the brightness of the object image, an indicating means for the displaceable position of said image forming optical system, said indicating means being controlled in accordance with an output signal of said position detecting means to determine the proper position of said image forming optical system, and a driving means for displacing said image forming optical system to the position determined by said indicating means, said driving means being selectively controlled in accordance with the output signal of said position detecting means; whereby said image forming optical system is moved along its optical axis so that light rays passed through said image forming optical system form the image at constant light quantity at a predetermined position in said first light beam.

Claim 31

An optical system having a position controlling device therefor and comprising: an image forming optical system for forming an image of the object to be photographed, aid image forming optical system being movable selectively along its optical axis; a light splitting means for splitting the light beam passed through said optical system from the object to be photographed into a first and a second light beam; a light regulating means disposed between said image forming optical system and said light splitting means, said regulating means controlling the light quantity provided to said light splitting means; a photomeasuring means for measuring the object light quantity passed through said image forming optical system and controlling said light regulating means in correspondence with said object light quantity, said photomeasuring means being selectively movable in said second light beam, and a position controlling means for controlling the selectively moved position of said image forming optical system, said position controlling means including a position detecting means for detecting the position of the focused image formed by said image forming optical system, said position detecting means being selectively movable in said second light beam and detecting the focused position according to the brightness of the object image, an indicating means for the displaceable position of said image forming optical system, said indicating means being controlled in accordance with an output signal of said position detecting means to determine the proper position of said image forming optical system, and a driving means for displacing said image forming optical system to the position determined by said indicating means, said driving means being selectively controlled in accordance with the output signal of said position detecting means; whereby said image forming optical system is moved along its optical axis so that light rays passed through said image forming optical system form the image at constant light quantity at a predetermined position in said first light beam.

Claim 32

An optical system according to claim 25, wherein said position detecting means has a light receiving surface inclined with respect to the optical axis of said first light beam and is movable across said first light beam in approximately perpendicular direction to the optical axis of said light beam.

Claim 33

An optical system according to claim 26, wherein said light receiving surface is provided with a photosensitive element.

Claim 34

An optical system according to claim 27, wherein said photomeasuring means has a biasing light emitting means for emitting biasing light to said light receiving surface when the object light quantity is below a predetermined value.

Claim 35

An optical system according to claim 25, wherein said photomeasuring means has a memory means for memorizing temporarily an object light quantity information.

Claim 36

An optical system according to claim 25, wherein said photomeasuring means has an alarm means for alarm-indicating when said object light quantity is below a predetermined value.

Claim 37

In combination a single lens reflex camera and an optical system having a position controlling device and comprising: a phototaking optical system for forming an image of the object to be photographed, said phototaking optical system being selectively movable along its optical axis; a trigger member for effecting the operation of said camera, said trigger member being displaceable selectively between a first and a second position; an optical means being selectiveldy arranged for positioning on and off the optical axis of said phototaking optical system, said optical means reflecting the light beam passed through said phototaking optical system into a first and a second light beam, said first light beam being formed when said optical means is off the optical axis of said phototaking optical system, and said second optical beam being formed when said optical means is on said optical axis; a light sensitive plane disposed on the optical axis of said first light beam; a light regulating means disposed between said phototaking optical system and said optical means, said regulating means controlling the light quantity provided to said optical means and to said light sensitive plane; a photomeasuring means for measuring the object light quantity passed through said phototaking optical system and controlling said regulating means in correspondence with the object light quantity, said photomeasuring means being selectively arranged in said second light beam; a memory means for memorizing temporarily an object light quantity information obtained by said photomeasuring means; a position controlling means for coNtrolling the selectively moved position of said phototaking optical system, said position controlling means including a position detecting means for detecting the position of the object image formed by said phototaking optical system, said position detecting means being provided with a signal generating means which selectively moves in said second light beam along the optical axis thereof, a first driving means for moving selectively said position detecting means in said second light beam, said first driving means being actuated in association with the displacing operation of said trigger member, an indicating means for indicating the moved position of said phototaking optical system, said indicating means being controlled in accordance with the output signal of said position detecting means to determine the position into which said phototaking optical system should be moved, and a second driving means for displacing said phototaking optical system to the position determined by said indicating means, said second driving means being selectively controlled in accordance with the output signal from said position detecting means; and a displacement detecting means for detecting whether or not said phototaking optical system is displaced to the determined position, said displacement detecting means being arranged to generate a signal for placing said optical means off the optical axis of said phototaking optical system and a signal for releasing the memory of said memory means; whereby said phototaking optical system is moved along its optical axis so that light rays passed through said phototaking optical system form the object image on said light sensitive plane at constant light quantity.

Claim 38

In combination a single lens reflex camera and an optical system having a position controlling device and comprising: a phototaking optical system for forming an image of the object to be photographed, said phototaking optical system being selectively movable along its optical axis; a trigger member for effecting the operation of said camera, said trigger member being displaceable selectively between a first and a second position; an optical means being selectiveldy arranged for positioning on and off the optical axis of said phototaking optical system, said optical means reflecting the light beam passed through said phototaking optical system into a first and a second light beam, said first light beam being formed when said optical means is off the optical axis of said phototaking optical system, and said second optical beam being formed when said optical means is on said optical axis; a light sensitive plane disposed on the optical axis of said first light beam; a light regulating means disposed between said phototaking optical system and said optical means, said regulating means controlling the light quantity provided to said optical means and to said light sensitive plane; a photomeasuring means for measuring the object light quantity passed through said phototaking optical system and controlling said regulating means in correspondence with the object light quantity, said photomeasuring means being selectively arranged in said second light beam; a memory means for memorizing temporarily an object light quantity information obtained by said photomeasuring means; a position controlling means for coNtrolling the selectively moved position of said phototaking optical system, said position controlling means including a position detecting means for detecting the position of the object image formed by said phototaking optical system, said position detecting means being provided with a signal generating means which selectively moves in said second light beam along the optical axis thereof, a first driving means for moving selectively said position detecting means in said second light beam, said first driving means being actuated in association with the displacing operation of said trigger member, an indicating means for indicating the moved position of said phototaking optical system, said indicating means being controlled in accordance with the output signal of said position detecting means to determine the position into which said phototaking optical system should be moved, and a second driving means for displacing said phototaking optical system to the position determined by said indicating means, said second driving means being selectively controlled in accordance with the output signal from said position detecting means; and a displacement detecting means for detecting whether or not said phototaking optical system is displaced to the determined position, said displacement detecting means being arranged to generate a signal for placing said optical means off the optical axis of said phototaking optical system and a signal for releasing the memory of said memory means; whereby said phototaking optical system is moved along its optical axis so that light rays passed through said phototaking optical system form the object image on said light sensitive plane at constant light quantity.

Claim 39

An optical system having a position controlling device therefor and comprising: an image forming optical system for forming an image by light from an object to be photographed, said optical system being selectively movable along its optical axis; a position controlling means for controlling the selectively movable position of said image forming optical system, said position controlling means including a movable position detecting means for detecting the position of the object image formed by said image forming optical system, said position detecting means being movable across a light beam passed through said image forming optical system in an approximately perpendicular direction to the optical axis of said light beam, and having a light receiving surface inclined with respect to the optical axis of said light beam, said light receiving surface being arranged to generate a signal in correspondence with the brightness of said object image, and a driving means for displacing said image forming optical system in response to the output signal of said light receiving surface; whereby said image forming optical system is displaced along its optical axis to form the object image on a predetermined plane.

Claim 40

An optical system having a position controlling device therefor and comprising: an image forming optical system for forming an image by light from an object to be photographed, said optical system being selectively movable along its optical axis; a position controlling means for controlling the selectively movable position of said image forming optical system, said position controlling means including a movable position detecting means for detecting the position of the object image formed by said image forming optical system, said position detecting means being movable across a light beam passed through said image forming optical system in an approximately perpendicular direction to the optical axis of said light beam, and having a light receiving surface inclined with respect to the optical axis of said light beam, said light receiving surface being arranged to generate a signal in correspondence with the brightness of said object image, and a driving means for displacing said image forming optical system in response to the output signal of said light receiving surface; whereby said image forming optical system is displaced along its optical axis to form the object image on a predetermined plane.

Claim 41

An optical system according to claim 32, wherein said light receiving surface is provided with a plurality of photosensitive elements.

Claim 42

An optical system according to claim 32, wherein said position detecting means includes a signal comparing means for comparing a signal generated by said signal generating means with a reference signal, said signal comparing means being electrically coupled with said driving means to control said driving means in correspondence with a difference between said reference signal and said signal generated by said signal generating means.