Abstract:
Binoculars, one form of telescope, in accordance with the present invention have a lens frame drive responsive to manipulating a focusing ring. Lens frames are driven to advance or withdrawn by means of the lens frame drive. The lens frames are driven to thrust from their positions of collapse to other positions, at which they enable observation, by manipulating the focusing ring. At this time, lens barriers covering the front surfaces of the lens frames are pressed by means of projections, and thus driven from positions at which they block objectives to other positions at which they free the objectives. Withdrawal of the lens barriers and thrusting of the lens frames can be achieved merely by manipulating the focusing ring. Changing the lens barriers from their positions of protection to their positions of withdrawal can be achieved with the simple manipulation.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a telescope having a barrier member for protecting an optical system. 
     2. Description of the Related Art 
     In general, that are one form of telescopes, have objectives and eyepieces, which are located at the front and back ends of paired lens barrels, exposed externally. When the binoculars are unused (stowed), if they are left intact, dust or oil and fat adhere to the surfaces of the lenses. When the adhering dust is wiped away, the lenses may be damaged. In conventional binoculars, a lens cap serving as an optical system protecting member is provided for groups of objectives and eyepieces in each of the right and left lens barrels. 
     However, the lens cap is merely mounted on the circumference of each lens barrel. The lens cap therefore readily comes off due to an extraneous force or the like. Moreover, there is a fear that the lens cap may be lost. For preventing the loss, a proposal has been made of binoculars having one end of each lens cap thereof coupled to the body of each lens barrel using a string-like member. However, the binoculars having one end of each lens cap coupled to the body of each lens barrel using the string-like member are hard to handle because the dismounted lens caps swing. Moreover, the appearance of the binoculars having the dismounted lens caps swinging is unfavorable. 
     Binoculars having a barrier, which can slide, mounted on the front surface of each lens have been proposed in the past. Before the binoculars are used, a barrier handler is manipulated in order to move the barrier. The lenses are thus freed. Thereafter, the lenses are focused and observation is carried out. 
     However, in the conventional binoculars having the barrier mounted on the surface of each lens, before observation is started, the barriers must be manipulated in order to focus the lenses. The manipulation of the barriers and a manipulation to be performed for focusing are independant and annoy a user. Moreover, since both a mechanism for driving the barriers and a mechanism for focusing the lenses must be included, the structure of the binoculars may become complex. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide a telescope whose usable state and unused state can be changed by moving a barrier member to a position of withdrawal and a position of protection relative to an optical system. Herein, the barrier member can be readily changed from the position of protection to the position of withdrawal. 
     According to the present invention, a telescope has a barrel, an optical system moving mechanism, and a barrier member. The lens barrel bears an optical system. The optical system moving mechanism is used to move the optical system between a position of non-use and a position of use. The barrier member can move to a position of protection at which it protects the front surface of the optical system and a position of withdrawal at which it has withdrawn from the front surface of the optical system. The barrier member is moved to the position of protection or the position of withdrawal responsively to a manipulation performed on the optical system moving mechanism. The barrier member can thus readily be changed from one state to the other. 
     The other features of the present invention and advantages thereof will be fully apparent from the description below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing the appearance of binoculars in accordance with the first embodiment of the present invention; 
     FIG. 2 is an exploded oblique view showing a lens frame drive and barrier mechanism which are incorporated in the binoculars of the first embodiment; 
     FIG. 3 is a longitudinal sectional view of a left lens frame and its surroundings in the binoculars of the first embodiment that are stowed; 
     FIG. 4 is a longitudinal sectional view of the left lens frame and its surroundings in the binoculars of the first embodiment that are usable; 
     FIG. 5 shows a change of a lens barrier included in the binoculars of the first embodiment from a closed state to an open state and a change in the position in a direction of thrust of a lens in relation to an angle θ of rotation at which a focusing ring is positioned; 
     FIG. 6 is an exploded oblique view showing a lens frame drive and barrier mechanism which are incorporated in binoculars of the second embodiment; 
     FIG. 7 is a plan view showing the interior of the binoculars of the second embodiment that are stowed with lens frames moved to their positions of collapse; 
     FIG. 8 is a plan view showing the interior of the binoculars of the second embodiment that are usable with the lens frames moved to their in-focus positions for infinite focus viewing; 
     FIG. 9 is a plan view showing the interior of the binoculars the second embodiment that are usable with the lens frames moved to their in-focus positions for the closest focus viewing; 
     FIG. 10 is an exploded oblique view showing a lens frame drive and barrier mechanism which are incorporated in binoculars of the third embodiment of the present invention; 
     FIG. 11 is a plan view showing the interior of the binoculars of the third embodiment that are stowed; 
     FIG. 12 is a plan view showing the interior of the binoculars of the third embodiment that are usable with the lens frames moved to their in-focus positions for infinite focus viewing; 
     FIG. 13 is a longitudinal sectional view of a lens frame and its surroundings in the binoculars of the third embodiment that are stowed; and 
     FIG. 14 is a longitudinal sectional view of a lens frame and its surroundings in the binoculars of the third embodiments that are usable. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be described in conjunction with the drawings. 
     The structure of binoculars  1 , shown as a telescope in FIGS. 2-14, in accordance with the first embodiment of the present invention, will be described using FIG.  1  and FIG.  2 . 
     FIG. 1 is a perspective view showing the appearance of the binoculars  1  of the first embodiment of the present invention. FIG. 2 is an exploded oblique view of a lens frame drive and barrier mechanism incorporated in the binoculars  1 . 
     In the description to be made below, an optical axis O is the optical axis of an observation optical system included in the binoculars, and Z directions are directions parallel to the optical axis O. A direction Z 0  out of the Z directions is a direction towards an eyepiece, and a direction Z 1  is a direction towards an objective. Directions X are rightward and leftward directions orthogonal to the optical axis O. A direction of rotation D 0  is a clockwise direction relative to the eyepiece, and a direction of rotation D 1  is a counterclockwise direction relative to an observer (see FIG.  2 ). These reference numerals will also be applied to subsequent embodiments. 
     The binoculars  1  of the present embodiment have, as shown in FIG.  1  and FIG. 2, a body  2 , a lens barrel bearing frame  3 , a lens barrel bearing frame  4 , lens frames  31  and  33 , lens frames  32  and  34 , left and right barrier mechanisms  6  and  7 , a lens frame drive  20 , and a lens frame handling unit  16 . The lens barrel bearing frame  3  is supported to be able to slide leftward relative to the body  2 , and slid for accomodating a user&#39;s pupil distance. The lens barrel bearing frame  4  is fixed to the body  2 . The lens frames  31  and  33  holding a left objective and eyepiece  25  and  26  serving as an observation optical system are borne by the lens barrel bearing frame  3  so that the lens frames can advance or withdraw freely. The lens frames  32  and  34  holding a right objective and eyepiece  27  and  28  are borne by the lens barrel bearing frame  4 . The left and right barrier mechanisms  6  and  7  include left and right lens barriers  8  and  9  that are barrier members. The lens frame drive  20  drives the lens frames, which are optical system thrusting means, so that the lens frames will advance or withdraw. The lens frame handling unit  16  drives the lens frame drive  20  so as to focus the lenses and open or close the barriers. 
     The barrier mechanism  6  as shown in FIG. 2, consists of a slide base  10 , a spring  29 , a lens barrier  8 , and a torsion spring  12 . The slide base  10  that is a sliding member is supported by a guide groove  3   b  bored in a stowage chamber  3   a  of the lens barrel bearing frame  3  so that the slide base  10  can freely slide in the Z directions. The spring  29  serving as a second constraining means constrains the slide base  10  to move in the direction Z 0 . The lens barrier  8  is supported by a support shaft  11  at the distal end of the slide base  10  so that the lens barrier  8  can pivot freely. The torsion spring  12  serving as a first constraining means constrains the lens barrier  8  to pivot in a direction in which the objective is protected (shielded). 
     The lens barrier  8  is a member movable to a position of protection (position of blocking) P 8 A at which it protects the objective or a position of withdrawal (position of freeing) P 8 B at which it has withdrawn into the stowage chamber  3   a . The position of withdrawal P 8 B is a position at which the lens barrier  8  has withdrawn from the front surface of the objective, due to a sliding movement in the direction Z 0  made by the slide base  10 , after pivoting in a direction of freeing. A manipulation knob  10   a  is formed on the lower side of the slide base  10 . 
     The barrier mechanism  7  has the same structure as the barrier mechanism  6 . The barrier mechanism  7  consists of a slide base  13 , a spring, a lens barrier  9 , and a torsion spring  15 . The slide base  13  is supported to be able to freely slide. The spring serving as a second constraining means that is not shown constrains the slide base  13  to move in the direction Z 0 . The lens barrier  9  is supported by a support shaft  14  so that it can rotate freely. The torsion spring  15  serving as a first constraining means constrains the lens barrier  9  to move in the direction of blocking. 
     The lens frame handling unit  16  consists of a focusing ring  17 , a cam unit, and a support shaft  18 . The focusing ring  17  can be manipulated externally. The cam unit is united with the focusing ring  17  and has a cam groove  17   a  that serves as an optical system thrusting means. The support shaft  18  is borne by the body  2  so that it can rotate freely, and supports the focusing ring  17  and cam unit. 
     The lens frame drive  20  has a drive base  21 , a slide plate  22 , and a support plate  23 . The drive base  21  has a slave pin  21   a  and a guide groove  21   c , and is borne by the body  2  so that it can slide freely in the Z directions over a distance defined by guide pins  2 b and  2 c. The slave pin  21   a  is engaged with-the cam groove  17   a  so that it can slide freely. The slide plate  22  is borne by a guide groove  21   b  in the-drive base  21  so that it can slide freely in the X directions. The slide plate  22  can freely slide in the Z directions in the lens barrel bearing frame  3  over a distance defined by a guide groove  22   a  while being interlocked with the drive base  21 . The support-plate  23  is fixed to the drive base  21  and bears the right lens frame  32  so that the right lens frame can slide freely. 
     A lens frame support  24  is fixed to the lens frame  31  holding the left objective. A projection  31   a  is projecting from the lower part of the lens frame  31 . The lens frame support  24  is always engaged with an engagement groove  22   b  bored in the distal part of the slide plate  22 . The lens frame support  24  moves together with the slide plate, whereby the lens frame  31  is driven to advance or withdraw in the Z directions. When the lens frame  31  is thrust in the direction Z 1 , the projection  31   a  presses the inner surface of the lens barrier  8  located at the position of blocking, and thus causes the lens barrier  8  to fall down in the direction of freeing. 
     The lens frame  32  holding the right objective has the same structure as the lens frame  31 . The lens frame  32  is driven to advance or withdraw by means of the support plate  23 . A projection of the lens frame  32 , which is not shown, causes the lens barrier  9  to fall down in the direction of freeing. 
     Actions made in the binoculars  1  of the first embodiment of the present invention, which have the foregoing structure, will be described in conjunction with FIG. 3 to FIG.  5 . 
     FIG. 3 is a longitudinal sectional view of the left lens frame and its surroundings in a lens-protected (shielded) state equivalent to the stowed state of the binoculars. FIG. 4 is a longitudinal sectional view of the left lens frame and its surroundings in a lens-freed (barrier withdrawn) state equivalent to the usable state of the binoculars. FIG. 5 graphically shows a change of the lens barrier from the closed state to the open state thereof and a change in the position in a direction of thrust of a lens in relation to the angle of rotation θ at which the focusing ring is positioned. The relationship shown in FIG.  5  is applicatable to the other embodiments described later. 
     As shown in FIG. 5, when the binoculars  1  are stowed, the focusing ring  17  is positioned at an angle of rotation θ 0 . The lens frames  31  and  32  are plunged into their positions of collapse by means of the cam groove  17   a  and lens frame drive  20 . At this time, the slide bases  10  have slid in the direction Z 1  because the knobs  10   a  were manipulated. As shown in FIG. 3, the lens barrier  8  is located at the position of blocking P 8 A, and the lens barrier  9  is located at the position of blocking P 9 A (see FIG.  1 ). 
     For making the binoculars  1  usable, the focusing ring  17  is rotated in the direction D 1  and positioned at an angle of rotation θ 1 . With the rotation, the drive base  21  and slide plate  22  are moved in the direction Z 1 . The lens frame  31  is thrust to the in-focus position for infinite focus viewing. Before the lens frame reaches the in-focus position for infinite focus viewing, that is, before the focusing ring  17  is positioned at the angle of rotation θ 1 , the projection  31   a  of the lens frame presses the lens barrier  8  in the direction Z 1  as shown in FIG.  4 . When the lens barrier is tilted by a predetermined angle to fall down, the constraining force produced by the spring  29  for constraining the slide base  10  to move in a certain direction operates on the slide base. The lens barrier  8  is then pulled into the stowage chamber  3   a  in the lower part of the left lens barrel bearing frame  3  along the guide groove  3   b  together with the slide base  10 . In this state, the lens barrier  8  has moved to the position of withdrawal P 8 B. Furthermore, the lens barrier  9  has also moved to the position of withdrawal. The binoculars  1  are thus put to an observation(discernment)-enabled state (see FIG.  5 ). 
     In this state, the focusing ring  17  is further rotated in the direction D 1  to an angle θ 2 . The lens frames  31  and  32  are thrust to their in-focus positions for the closest focus viewing. For adjusting the binoculars at accommodate user&#39;s pupil distance, the left lens frame bearing frame  3  is slid in an outward X direction. With the sliding manipulation, the slide plate  22  is moved together with the left lens frame bearing frame  3  and lens frame  31  in the X direction by means of the guide pin  3   c . Consequently, the pupil distance can be modified. 
     For returning the binoculars  1  from the usable state to the stowed state, first, the binoculars are adjusted to the narrowest distance. However, this manipulation is not required. The pupil distance may remain wide. Thereafter, the focusing ring  17  is rotated in the direction D 0  to the angle θ 0 . The lens frames  31  and  32  are thus plunged into the positions of collapse. The knobs  10   a  are manipulated in order to slide the slide bases  10  in the direction Z 1 . This causes, as shown in FIG. 3, the lens barriers  8  and  9  to pivot to the positions of blocking P 8 A and P 9 A (see FIG.  1 ). 
     According to the binoculars  1  of the first embodiment of the present invention, the manipulation of freeing to be performed for withdrawing the lens barriers can be interlocked with a manipulation to be performed for rotating the focusing ring for focusing the lenses. The binoculars can therefore be quickly brought to the observation-enabled state. Moreover, as mentioned above, driving the lens barriers for freeing the objectives may be interlocked with movements of the lens frames. This results in a simple barrier mechanism. 
     Next, the structure of binoculars  40  will be described as that of a telescope in accordance with the second embodiment of the present invention in conjunction with FIG.  6 . FIG. 6 is an exploded oblique view showing a lens frame drive and barrier mechanism incorporated in the binoculars. 
     In the binoculars  1  of the first embodiment, for returning the lens barrier  8  to the position of lens protection (position of blocking) P 8 A, the manipulation knob  10   a  of the slide base  10  must be manipulated. This may be annoying. In the binoculars  40  of the present embodiment, an action to be made for returning the lens barrier  8  to the position of lens protection (position of blocking) P 8 A is interlocked with an action to be made for plunging the lens frame  31  into the position of collapse (position of stowage). The binoculars  40  have the same components as the binoculars  1  of the first embodiment except a barrier interlocking mechanism. Only the different component will be described. The same reference numerals will be assigned to the same members. 
     A barrier mechanism  45  for a left objective included in the binoculars  40  has a slave pin  43  fixed to the slide base  10 . The knob  10   a  is excluded. Moreover, a support shaft  3   d  is fixed to the left lens barrel bearing frame  3 . A slide base drive lever  42  that is a rotating member for pressing the slave pin  43  and thus driving it is supported by the support shaft  3   d  so that the slide base drive lever can freely swivel. Restriction pins  44   a  and  44   b  for limiting the swiveling of the drive lever  42  to a required range are placed near the drive lever, as shown in FIG.  7 . 
     The lens frame support  24  can abut on the slide base drive lever  42 . When the lens frame support  24  moves in the direction Z 0  that is a direction in which the lens frame is stowed, the drive lever  42  is driven to swivel clockwise. This causes the slide base  10  to slide in the direction Z 1  via the slave pin  43 . With the movement of the slide base  10 , the lens barrier  8  is pushed to a position at which the lens barrier can pivot in a direction in which the objective is shielded. The constraining force produced by the torsion spring  12  causes the lens barrier to pivot to the position of protection P 8 A. 
     A barrier mechanism for the right objective is not shown but has the same components as the barrier mechanism  45  for the left objective. 
     Actions to be made for opening or closing the barriers included in the binoculars  40  of the second embodiment having the foregoing components will be described in conjunction with FIG. 7 to FIG.  9 . FIG. 7 is a plan view showing the interior of the binoculars  40  that is stowed with the lens frames moved to their positions of collapse. FIG. 8 is a plan view showing the interior of the binoculars  40  that is usable with the lens frames moved to their in-focus positions for infinite focus viewing. FIG. 9 is a plan view showing the interior of the binoculars  40  that is usable with the lens frames moved to their in-focus positions for the closest focus viewing. The relationship among the angle of rotation at which the focusing ring is positioned, the position of thrust to which the objective is thrust, and the movement of the barrier is identical to that graphically shown in FIG.  5 . 
     As shown in FIG. 7, when the binoculars  40  are stowed, the focusing ring  17  is positioned at its position of stowage. The lens frames  31  and  32  are plunged into their positions of collapse. Moreover, the lens barrier  8  has pivoted in a direction of closing due to the constraining force produced by the torsion spring  12 , and is retained at the position of blocking P 8 A. At this time, the slide base drive lever  42  has been pressed by the lens frame support  24  and rotated clockwise. 
     For changing the binoculars  40  from the stowed state to the usable state, similarly to that in the first embodiment, the focusing ring  17  is rotated in the direction D 1  and positioned at the angle of rotation θ 1 . This causes the lens frame  31  to thrust to its in-focus position for infinite focus viewing as shown in FIG.  8 . Immediately before the lens frame reaches the in-focus position for infinite focus viewing the lens barrier  8  is pressed by the lens frame  31  and moved to the position of withdrawal P 8 B. The front surface of the objective  25  is thus freed. At this time, the slide base  10  moves together with the lens barrier  8  in the direction Z 0  to its position of withdrawal in the withdrawal chamber. The slide base drive lever  42  rotates counterclockwise. 
     In the above state, the focusing ring  17  is further rotated in the direction D 1  and positioned at the angle θ 2 . Consequently, as shown in FIG. 9, the lens frames  31  and  32  are thrust to their in-focus positions for the closest focus viewing in the manner as they are in the first embodiment. 
     For returning the binoculars  40  from the usable state to the stowed state, similarly to that in the first embodiment, the focusing ring  17  is rotated in the direction D 0  and positioned at the angle of rotation θ 0 . This causes the lens frames  31  and  32  to plunge into their positions of collapse. Along with the plunging action, as shown in FIG. 7, the lens frame support  24  withdrawing in the direction Z 0  drives the slide base drive lever  42  to swivel clockwise. With the swiveling, the drive pin  43  presses the slide base  10 . The slide base  10  then moves in the direction Z 1 . 
     Along with the movement of the slide base  10 , the lens barrier  8  moves outward from the stowage chamber  3   a  of the lens barrel bearing frame  3 . The lens barrier  8  then pivots due to the constraining force produced by the torsion spring  12  and lies at the position of blocking P 8 A. The slide base moves together with the lens barrel in the direction Z 1 . 
     In the binoculars  40  of the second embodiment, driving the lens barrier to withdraw it for freeing the objective and driving the lens barrier to the position of blocking can be initiated by manipulating the focusing ring, which is used for focusing the binoculars, to rotate it. Manipulating the binoculars to change their states from the observation-enabled state to the stowed state or vice versa can be achieved very easily. 
     Next, the structure of binoculars  50  will be described as that of a telescope in accordance with the third embodiment of the present invention in conjunction with FIG.  10 . FIG. 10 is an exploded oblique view of a lens frame drive and barrier mechanism incorporated in the binoculars. 
     In the binoculars  1  of the first embodiment, the slide base  10  is needed for plunging the lens barrier  8  into the position of withdrawal P 8 B, and the stowage chamber  3   a  is needed for stowing the lens barrier and slide base. This may cause the lens barrel bearing frame to become complex or large-sized. In the binoculars  50  of the present embodiment, neither the slide base  10  nor chamber  3   a  is needed. The binoculars  50  have the same components as the binoculars  1  of the first embodiment except the barrier mechanism. Only the different component will be described. The same reference numerals will be assigned to the same members. 
     A barrier mechanism  55  for the left objective of the binoculars  50  has a lens barrier  58  supported by a support shaft  11  fixed to the left lens barrel bearing frame  3  so that the lens barrier  58  can pivot freely. The lens barrier  58  has a claw  58   a  extending from an upper position on the lens-side surface thereof. The lens barrier  58  is constrained to move in a direction of freeing by means of a torsion spring  54  serving as a first constraining means. 
     A barrier locking lever  52  that is a rotational interlocked member has a lock claw  52   a  that can be engaged with the claw  58   a . The barrier locking lever  52  is attached to the support shaft  3   e  of the left lens barrel bearing frame  3 . A spring  53  that is a second constraining means for constraining the barrier locking lever  52  to move in a direction of engagement is coupled to the barrier locking lever  52 . Furthermore, a pin  31   b  capable of pressing the barrier locking lever  52  in a direction of unlocking is fixed to the left lens frame  31 . 
     The barrier mechanism for the right objective has the same components as the barrier mechanism  55  for the left objective, though it is not illustrated. 
     Actions to be made for opening or closing the barrier in the binoculars  50  of the third embodiment having the foregoing components will be described in conjunction with FIG. 10 to FIG.  14 . FIG. 11 is a plan view showing the interior of the binoculars  50  that are stowed. FIG. 13 are a longitudinal sectional view of a lens frame and its surroundings in the state shown in FIG.  11 . FIG. 12 is a plan view showing the interior of the binoculars  50  that are usable with the lens frames moved to their in-focus positions for infinite focus viewing. FIG. 14 is a longitudinal sectional view of a lens frame and its surroundings in the state shown in FIG.  12 . The relationship among the angle of rotation at which the focusing ring is positioned, the position of thrust to which the objective is thrust, and the movement made by the barrier shall be identical to the relationship graphically shown in FIG.  5 . 
     As shown in FIG.  10  and FIG. 11, when the binoculars  50  are stowed, the focusing ring  17  are positioned at the angle of rotation θ 0  to its position of stowage. The lens frame  31  has been plunged to its position of collapse. Moreover, the lens barrier  58  has the claw  58   a  thereof locked by the barrier locking lever  52 , and is retained at its position of blocking P 58 A. 
     For changing the binoculars  50  from the stowed state to the usable state, similarly to that in the first embodiment, the focusing ring  17  is rotated in the direction D 1  and positioned at the angle of rotation θ 1 . The lens frame  31  is thus thrust to its in-focus position for infinite focus viewing. Immediately before the lens frame reaches the in-focus position for infinite focus viewing, as shown in FIG. 12, the pin  31   b  presses the barrier locking lever  52  along with the movement of thrusting made by the lens frame  31 . The claw  58   a  of the lens barrier  58  is then unlocked. The lens barrier  58  pivots due to the constraining force produced by the torsion spring  54  from its position of blocking P 58 A (FIGS. 11 and 13) through a middle position P 58 C (FIG. 12) to, as shown in FIG. 14, its position of withdrawal P 58 B. Consequently, the front surface of the objective  25  is freed. 
     The focusing ring  17  is further rotated in the direction D 1  and positioned at the angle θ 2 . The lens frame  31  is then thrust to its in-focus position for the closest focus viewing in the same manner as that in the first embodiment. 
     For returning the binoculars  50  from the usable state to the stowed position, the focusing ring  17  is rotated in the direction D 0  and positioned at the angle of rotation θ 0  in the same manner as that in the first embodiment. The lens frame  31  is then plunged into its position of collapse. The pin  31   b  of the lens frame  31  moves in the direction Z 0 . This causes the barrier locking lever  52  to pivot counterclockwise up to a position at which it is engaged with the locked claw  58   a  of the lens barrier  58 . 
     The lens barrier  58  is manipulated so that it will pivot to its position of blocking P 58 A in FIG. 11 against the constraining force produced by the torsion spring  54 . The claw  58   a  of the lens barrier  58  is locked by the barrier locking lever  52 . The lens barrier  58  is retained at the position of blocking P 58 A, and the binoculars  50  are put in the stowed state. 
     In the foregoing binoculars of the third embodiment, driving the lens barrier to withdraw it for freeing the objective can be achieved by rotating the focusing ring, which is used to focus the binoculars. Moreover, the stowage chamber in which the lens barrier  58  is stowed is unnecessary. This leads to a simplified barrier mechanism. Consequently, a compact lens frame can be realized. 
     As mentioned in the telescopes of the embodiments of the present invention, the barrier member is moved from its position of protection (position of shielding) at which it protects an optical system to its position of withdrawal (position of freeing) responsively to an action made by the optical system thrusting means. This leads to a simplified manipulation changing the binoculars to a usable state permitting observation. Consequently, the binoculars can be handled easily.