Abstract:
Disclosed is a pair of variable-powered binoculars capable of keeping a high resolution without causing much change in the quality of the image, securing a wide view, and making small the difference between the eye relief of a low magnifying arrangement and that of a high magnifying arrangement when they are switched.  
     The binoculars comprise a pair of objective lens systems; a pair of prism systems, each of the prism system inverting an image that advances through the corresponding objective lens systems, from an inverted image to an erecting image; a pair of concave adjusting lenses, each of the concave adjusting lenses placed between the focus formed by the corresponding objective lens system and the corresponding prism system, so that each of the concave adjusting lenses is movable along the optical axis formed by the corresponding objective lens system and the corresponding prism system; and a pair of ocular lens systems, each of the ocular lens systems placed on the optical axis, so that each ocular lens system is movable along the optical axis closer to or away from the corresponding concave adjusting lens, synchronizing with a movement of the corresponding concave adjusting lens.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to a pair of variable-powered binoculars. More particularly, it provides a pair of binoculars with a pair of ocular zoom lens systems, of which magnifying power is varied by synchronously moving concave adjusting lenses and the ocular zoom lens systems.  
         BACKGROUND ART  
         [0002]    One example of variable-powered binoculars that are able to vary their magnifying power continuously is a pair of binoculars with ocular zoom lens systems. The ocular lens system of this type of binoculars is provided with at least a first lens placed closer to the eye and a second lens placed near the concave adjusting lens. Sometimes, a third lens is further placed between the first and second lenses. With the binoculars having ocular zoom lens systems, the user can continuously vary their magnifying power by moving the second lens closer to or away from the first lens. This type of binoculars can vary the magnifying power largely through a small movement of the second lens along the optical axis, which leads to an advantageous miniaturization of the binoculars. Due to this advantage, almost all of the existing variable-powered binoculars employ the ocular zoom lens system.  
           [0003]    [0003]FIG. 1 is a schematic illustration of the optical system of the conventional variable-powered binoculars with an ocular zoom lens system. FIG. 1(A) shows the optical arrangement when the system has a low magnifying power of 7, while FIG.  1 (B) the arrangement when the system has a high magnifying power of 15. In FIGS.  1 (A) and  1 (B), reference numeral  1  depicts an objective lens, reference numeral  2  an ocular lens, reference numeral  3  a prism system, reference numeral  4  a concave adjusting lens, reference numeral  5  a field lens, reference numeral  6  an objective image forming plane, and reference numeral  7  an apparent image forming plane. In the optical system of FIG. 1, the objective lens  1 , the ocular lens  2  and the prism system  3  are fixed, while the concave adjusting lens  4  and the field lens  5  are movable along the optical axis of the optical system in FIG. 1. When the magnification is small as shown in FIG. 1(A), the concave adjusting lens  4  is located at position a, and the field lens  5  at position c. To change the magnification from a low one shown in FIG. 1(A) to a high one shown in FIG. 1(B), the concave adjusting lens  4  is moved to position b in FIG. 1(B) and the field lens  5  to position d in the same figure. These two lenses are moved by turning a zoom lever or a zoom ring (not shown in the figures) which the variable-powered binoculars have. When the zoom lever or zoom ring is turned, the concave adjusting lens  4  and the field lens  5 , which are interlocked, shift together along the optical axis of the optical system. When the user of the variable-powered binoculars would like to see a magnified image of an object, s/he needs to turn the zoom lever or zoom ring to a position where the lens system gives him/her the desired magnification.  
           [0004]    However, since the conventional variable-powered binoculars have a mechanism in which the magnification is changed by moving two lenses, the concave adjusting lens and the field lens, they have difficulties in providing a large visual field and keeping a high resolution. It is because the quality of an image tends to change, which is caused by change in stigmatism when the magnifying power was changed from a low one to a high one. Besides, because of the difference between the eye relief when the arrangement is set for a high magnification and that when the arrangement is for a low magnification, the user sometimes cannot see some objects very well. Moreover, since the concave adjusting lens and the field lens have to be interlocked in the conventional variable-powered binoculars, the mechanical structure to interlock them is complicated, and therefore the production or assembly of the binoculars is not always easy.  
         SUMMARY OF THE INVENTION  
         [0005]    One objective of the present invention is to provide a pair of variable-powered binoculars capable of keeping a high resolution over a wide magnification range, from a low magnification to a high, without causing much change in the quality of the image.  
           [0006]    Another objective of the present invention is to provide a pair of variable-powered binoculars capable of securing a wide view, especially a wide apparent view when the binoculars have a low magnification.  
           [0007]    Still another objective of the present invention is to provide a pair of variable-powered binoculars capable of making small the difference between the eye relief of a low magnifying arrangement and that of a high magnifying arrangement when they are switched, while capable of keeping the eye relief long.  
           [0008]    A still further objective of the invention is to provide a pair of variable-powered binoculars which has a relatively simple mechanical structure and of which production or assembly is easy.  
           [0009]    Other objectives and features of the invention will be apparent from the following explanations.  
           [0010]    In order to achieve the foregoing objectives, the present invention provides a pair of variable-powered binoculars, which comprises:  
           [0011]    a pair of objective lens systems;  
           [0012]    a pair of prism systems, each of the prism system inverting an image that advances through each of the objective lens systems, from an inverted image to an erecting image;  
           [0013]    a pair of concave adjusting lenses, each of the concave adjusting lenses placed between the focus formed by the corresponding objective lens system and the corresponding prism system, so that each of the concave adjusting lenses is movable along the optical axis formed by the corresponding objective lens system and the corresponding prism system; and  
           [0014]    a pair of ocular lens systems, each of the ocular lens systems placed on the optical axis, so that each ocular lens system is movable along the optical axis closer to or away from the corresponding concave adjusting lens, synchronizing with a movement of the corresponding concave adjusting lens.  
           [0015]    Another aspect of the present invention is the pair of the variable-powered binoculars wherein each of said ocular lens systems is movable on the optical axis so that the focus of each ocular lens system can be adjusted to the focus of the corresponding objective lens system that has been changed by the movement of the corresponding concave adjusting lens.  
           [0016]    Still another aspect of the present invention is the pair of the variable-powered binoculars wherein each of the ocular lens systems comprises combined lenses.  
           [0017]    The pair of variable-powered binoculars having the features described in the foregoing, since the whole ocular lens systems thereof, each comprising the combined plural lenses, are moved together, which is different from the typical way employed for conventional binoculars, can keep unchanged the location where the apparent image is formed. The ocular lens system of the invention can reduce a change in stigmatism caused by moving at least one lens of the ocular lens system in the conventional variable-powered binoculars. Therefore the pair of binoculars can provide images of which qualities are almost unchanged and keep its resolution, without deterioration, from a low magnification to a high magnification at such a high level as that of single-powered binoculars.  
           [0018]    The apparent visual field means the angle of an apparent image made by the binoculars, the angle which the outgoing beams make at the point of the eye with respect to the apparent image. With the binoculars of the present invention, since the whole ocular lens system is moved together, the difference in stigmatism between a low magnification arrangement and a high magnification arrangement can be reduced. This technical feature assures a wide visual field. Conventional binoculars with an ocular zoom lens system that have been adjusted so that the apparent visual field is large at a high magnification typically provide an apparent visual field of less than 40° when the lenses of the ocular lens system are moved to a low magnification arrangement. As a result, when the magnifying power is low, the narrow apparent visual field provides a narrow visual field, which hinders the user from a comfortable observation. On the other hand, the binoculars of the present invention are capable of keeping substantially unchanged the apparent visual field when the arrangement is for a low magnification and when it is for a high magnification. Even when the ocular lens system is designed so that the apparent visual field at a high magnification is 50° or more, a wide apparent visual field of 50° or over at a low magnification is assured by moving the whole ocular lens system together to set the system to the low magnification arrangement.  
           [0019]    Further, with the conventional zoom lens binoculars, since one of the lenses that comprise the ocular lens system is moved, the focal length of the ocular lens system at a low magnification is different from that at a high magnification, which results in a large difference between the eye relief when the arrangement is set for a high magnification and that when the arrangement is set for a low magnification. Consequently, the user sometimes cannot see some objects very well with conventional binoculars. On the other hand, since the pair of variable-powered binoculars in accordance with the present invention is capable of making small the difference between the eye relief of the low magnifying arrangement and that of the high magnifying arrangement when they are switched, which makes it possible for the user to see the objects that could not be observed well with the conventional binoculars. Needless to say, it also assures a long eye relief. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 is a schematic illustration of the optical system of the conventional variable-powered binoculars with an ocular zoom lens system. FIG. 1(A) shows an optical arrangement when the system has a low magnification, while FIG. 1(B) an arrangement when the system has a high magnification.  
         [0021]    [0021]FIG. 2 is a schematic illustration of the optical system of the variable-powered binoculars in accordance with the present invention. FIG. 2(A) shows an optical arrangement when the system has a low magnification, while FIG. 2(B) an arrangement when the system has a high magnification.  
         [0022]    [0022]FIG. 3 is a sectional view of a first example of the variable-powered binoculars in accordance with the present invention.  
         [0023]    [0023]FIG. 4 is an enlarged view of Part II, which is encircled with an ellipse in FIG. 3.  
         [0024]    [0024]FIG. 5 is a perspective exploded view of the magnification-varying mechanism of the first example.  
         [0025]    [0025]FIG. 6(A) is a side view of an outer cylinder of the ocular optical system, FIG. 6(B) a plan view of the outer cylinder, and FIG. 6(C) a side view showing a principal part of the outer cylinder.  
         [0026]    [0026]FIG. 7(A) is a side view of a cam inner cylinder, FIG. 7(B) a plan view of the cam inner cylinder, and FIG. 7(C) a side view showing a principal part thereof.  
         [0027]    [0027]FIG. 8(A) is a side view of an ocular inner cylinder holder, and FIG. 8(B) a plan view of the ocular inner cylinder holder.  
         [0028]    [0028]FIG. 9(A) is a side view of an ocular inner cylinder, and FIG. 9(B) a plan view of the ocular inner cylinder.  
         [0029]    [0029]FIG. 10(A) is a side view of a cam inner cylinder retainer, and FIG. 10(B) a plan view of the retainer.  
         [0030]    [0030]FIG. 11(A) is a side view of an outer support cylinder, and FIG. 11(B) a plan view of the outer support cylinder.  
         [0031]    [0031]FIG. 12(A) is a side view of a pop-up ring, and FIG. 12(B) a plan view of the pop-up ring.  
         [0032]    [0032]FIG. 13(A) is a side view of a rubber cup, and FIG.  13 (B) a plan view of the rubber cup.  
         [0033]    [0033]FIG. 14 is a sectional view of a second example of the variable-powered binoculars in accordance with the present invention.  
         [0034]    [0034]FIG. 15 is an enlarged view of Part XIV, which is encircled with an ellipse in FIG. 14.  
         [0035]    [0035]FIG. 16 is a perspective exploded view of the magnification-varying mechanism of the second example.  
         [0036]    [0036]FIG. 17(A) is a side view of an outer cylinder of the ocular optical system, and FIG. 17(B) a plan view of the outer cylinder.  
         [0037]    [0037]FIG. 18(A) is a side view of a cam inner cylinder, FIG. 18(B) a plan view of the cam inner cylinder, and FIG. 18(C) a side view showing a principal part of thereof.  
         [0038]    [0038]FIG. 19(A) is a side view of a cam inner cylinder retainer, and FIG. 19(B) a plan view of the retainer.  
         [0039]    [0039]FIG. 20(A) is a side view of an outer support cylinder, and FIG. 20(B) a plan view of the outer support cylinder.  
         [0040]    [0040]FIG. 21(A) is a side view of a twist ring, FIG. 21(B) a plan view of the twist ring, and FIG. 21(C) a side view showing a principal part thereof.  
         [0041]    [0041]FIG. 22(A) is a side view of a rubber cup, and FIG. 22(B) a plan view of the rubber cup. 
     
    
     EXPLANATION OF REFERENCE NUMERALS  
       [0042]    [0042] 8 : objective lens,  9 : ocular lens system,  10 : prism system,  11 : concave adjusting lens (concave lens),  12 : objective image forming plane,  13 : apparent image forming plane,  20 : variable-powered binoculars,  27 : objective lens,  28 : ocular lens system,  29 : Porro prism,  30 : concave adjusting lens,  31 : magnification-varying mechanism  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0043]    [0043]FIG. 2 is a schematic illustration of the optical system of the variable-powered binoculars in accordance with the present invention. FIG. 2(A) shows the optical system when the magnifying power is 8, which is a low magnification. FIG. 2(B) shows the optical system when the magnifying power is 12, a high magnification. In FIGS.  2 (A) and  2 (B), reference numeral  8  depicts an objective lens, reference numeral  9  an ocular lens system, reference numeral  10  a prism system, reference numeral  11  a concave adjusting lens comprising a concave lens, reference numeral  12  an objective image forming plane, and reference numeral  13  an apparent image forming plane. In the optical system shown in FIG. 2, the objective lens  8  and the prism system  10  are fixed. On the other hand, the ocular lens system  9  and the concave adjusting lens  11  are placed so that they can be moved along the optical axis of the variable-powered binoculars. The concave adjusting lens  11  is placed between the prism system  10  and the objective image-forming plane  12  in the binoculars. When the lenses are arranged for a low magnification as shown in FIG. 2(A), the concave adjusting lens  11  is located at position e. When the arrangement is changed from the low magnification one shown in FIG. 2(A) to the high magnification one shown in FIG. 2(B), the concave adjusting lens  11  is moved to position f, which shifts the objective image forming plane, and then the ocular lens system  9  is moved from position g in FIG. 2(A) to position h in FIG. 2(B) in accordance with the shift of the objective image forming plane. In other words, since the concave adjusting lens is moved along the optical axis, the focal length of the objective lens  8  is elongated. Then, the ocular lens system  9  is moved along the optical axis so that the focus of the ocular lens system  9  meets the focus of the objective lens  8 , of which focal length has been elongated. The location where the apparent image is formed in relation to the position of the eye is the focal plane of the ocular lens system  9 , which means that the focal length of the ocular lens system  9  is not changed. Therefore the width of the apparent visual field is kept essentially constant when the magnifying power of the binoculars is changed.  
         [0044]    In summary, a change in the magnifying power effected by moving the concave adjusting lens  11  causes a change of the objective focal length and a shift of the objective image forming plane. Simultaneously, the whole ocular lens system  9  is moved in accordance with the shift of the objective image forming plane. In other word, the ocular lens system  9 , which was fixed conventionally, is moved. Thus, the magnifying power of the binoculars is changed by moving the concave adjusting lens  11  and the ocular lens system  9 .  
         [0045]    The concave adjusting lens  11  and the ocular lens system  9  are moved by turning a zoom lever or zoom ring (not shown). When the zoom lever or zoom ring is turned, the concave adjusting lens  11  and the ocular lens system  9  are moved, with being interlocked, along the optical axis of the optical system of the binoculars. If the user would like to look at an enlarged image of the object, s/he can achieve it only by turning the zoom lever or zoom ring to the point that the desired magnification is obtained.  
         [0046]    In the followings, I will explain examples of the present invention, referring to the attached figures.  
       EXAMPLES  
     Working Example 1  
       [0047]    FIGS.  3 - 13  show a first example of the present invention. As shown in FIG. 3, the pair of variable-powered binoculars is a pair of prism binoculars. The body thereof comprises the arm  23  of a scope  21  and the arm  24  of a scope  22  that are rotatably connected with a bridge  25 . Central trunk rollers  26  are engaged with the bridge  25  so that the central trunk rollers can turn on the bridge in both directions. Each of the scopes  21  and  22  is provided with an objective lens  27 , an ocular lens system  28  and Porro prisms  29 . Light beams coming through the objective lens  27  advance through the Porro prisms  29  to the ocular lens system  28 . The Porro prism  29  is an erecting prism. Between ocular lens systems  28  and their corresponding Porro prisms  29  are respectively placed concave adjusting lenses  30 . Each ocular lens system  28  and the corresponding concave adjusting lens  30  are supported by a magnification-varying mechanism  31 , with which each of the scopes  21  and  22  is provided, and interlocked with the mechanism. Thus the ocular lens system  28  and concave adjusting lens  30  are moved together along the optical axis  32 .  
         [0048]    [0048]FIG. 4 is an enlarged view of the magnification-varying mechanism  31  in FIG. 3. FIG. 5 is a perspective exploded view of the magnification-varying mechanism  31 . FIGS.  6 - 13  respectively show the principal components of the magnification-varying mechanism. The magnification-varying mechanism  31  comprises an ocular outer cylinder  33  shown in FIG. 6, which is fixed onto each of the ocular portions of the respective scopes  21  and  22 ; a cam inner cylinder  34  shown in FIG. 7, which is rotatably engaged with each ocular outer cylinder  33 ; and the concave adjusting lens  30  that is placed in the cam inner cylinder  34  so that it can move reciprocally along the optical axis  32 . The concave adjusting lens  30  is fixed to a supporting cylinder  35 , which can slidably move on the inner surface of the cam inner cylinder  34  along the optical axis  32 . From the side face of the supporting cylinder  35  is projected a pin  36 , which is engaged with a longitudinal guide  39  of the outer cylinder  33  through an inner cam guide  37  cut out of the cam inner cylinder  34 . Reference numeral  38  depicts an outer cam guide made in the peripheral face of the ocular outer cylinder  33 . Also, longitudinal guides  40  are cut out of the peripheral face of the cam inner cylinder  34 . By inserting pins  41  into the longitudinal guides  40 , an inner cylinder holder  42  shown in FIG. 8 is slidably fitted into the cam inner cylinder  34 . The pins  41  are screwed and fixed in tapped holes  43  bored in the peripheral surface of the inner cylinder holder  42 .  
         [0049]    An ocular inner cylinder  44  shown in FIG. 9 is inserted into and fixed onto the inner cylinder holder  42 . To the ocular inner cylinder are fixed ocular lenses  28   a ,  28   b ,  28   c  and  28   d  that comprise the ocular lens system  28 . The inner cylinder holder  42  slidably moves along the longitudinal guides  40  formed in the cam inner cylinder  34  within the range of the length of the guides  40 . When the inner cylinder holder  42  slides on the inner surface of the cam inner cylinder  34 , the ocular inner cylinder  44  moves along the optical axis  32  together with the inner cylinder holder  42 . As shown in FIG. 10, a cam inner cylinder retainer  45  is screwed with the outer peripheral face of the ocular outer cylinder  33  and is engaged with the upper end of the cam inner cylinder  34  to prevent the cylinder  34  from slipping out. On the inner surface of the cam inner cylinder retainer  45  is formed a ring groove  45   a  provided with a seal ring  46 .  
         [0050]    An outer support cylinder  47  shown in FIG. 11 is engaged with the outer peripheral surface of the cam inner cylinder retainer  45 . In the peripheral face of the outer support cylinder  47  are bored tapped holes  48  with which screws  49  are engaged. The outer support cylinder  47  is fixed to the cam cylinder retainer  45  with the screws  49 . As shown in FIG. 12 a pop-up ring  50  is slidably engaged with the outer peripheral face of the outer support cylinder  47 . Longitudinal guides  51  are cut out of the peripheral face of the pop-up ring  50 . The screws  50  are turned into the tapped holes  48  of the outer support cylinder  47  through the respective longitudinal guides  51 . Reference numeral  52  depicts a ring groove formed on the outer peripheral surface of the pop-up ring  50 . The ring groove  52  is provided with a sealing ring  53 . Then, a rubber cup  54  is engaged with the outer peripheral surface of the pop-up ring  50  (FIG. 13). The rubber cup  54  together with the pop-up ring  50  can be extended from the binoculars  20 . The state where the rubber cup  54  is extended together with the pop-up ring  50  is shown in FIG. 4 with a broken line.  
       Working Example 2  
       [0051]    FIGS.  14 - 27  show a second example of the variable-powered binoculars in accordance with the present invention. In these figures the same components as those shown in FIGS.  3 - 13  have the common reference numerals. FIG. 15 is an enlarged view of a magnification-varying mechanism  60  in FIG. 14. FIG. 16 is a perspective exploded view of the mechanism  60 . FIGS.  17 - 27  respectively show the principal components of the magnification-varying mechanism  60 . The mechanism  60  comprises an ocular outer cylinder  61  shown in FIG. 17, which is fixed onto each of the respective ocular portions of the scopes  21  and  22 ; a cam inner cylinder  62  shown in FIG. 18, which is rotatably engaged with each ocular outer cylinder  61 ; and a concave adjusting lens  30  that is placed in the cam inner cylinder  62  so that it can move reciprocally along the optical axis  32 . The concave adjusting lens  30  is fixed to a supporting cylinder  35 , which can slidably move on the inner surface of the cam inner cylinder  62  along the optical axis  32 . From the side face of the supporting cylinder  35  is projected a pin  36 , which is engaged with a longitudinal guide  64  of the ocular outer cylinder  61  through a first cam guide  63  made by cutting it out of the cam inner cylinder  62 . Reference numeral  65  depicts second cam guides made in the peripheral face of the ocular outer cylinder  61 . Also, third cam guides  66  are cut out of the peripheral face of the cam inner cylinder  62 . By inserting pins  41  into the third cam guides  66 , an inner cylinder holder  42  shown in FIG. 8 is slidably fitted into the cam inner cylinder  62 . The pins  41  are screwed and fixed in tapped holes  43  bored in the peripheral surface of the inner cylinder holder  42 .  
         [0052]    An ocular inner cylinder  44  shown in FIG. 9 is inserted into and fixed to the inner cylinder holder  42 . To the ocular inner cylinder are fixed ocular lenses  28   a ,  28   b ,  28   c  and  28   d  that comprise the ocular lens system  28 . The inner cylinder holder  42  can slidably move along the third cam guides  66  formed in the cam inner cylinder  62 . When the inner cylinder holder  42  slides on the inner surface of the cam inner cylinder  62 , the ocular inner cylinder  44  turns and moves along the optical axis  32  together with the inner cylinder holder  42 . As shown in FIG. 19, a cam inner cylinder retainer  67  is screwed with the outer peripheral face of the ocular outer cylinder  61  and is engaged with the upper end of the cam inner cylinder  62  to prevent the inner cylinder  62  from slipping out. On the inner surface of the cam inner cylinder retainer  67  is formed a ring groove  67   a  provided with a seal ring  46 .  
         [0053]    An outer support cylinder  68  shown in FIG. 20 is engaged with the outer peripheral surface of the cam inner cylinder retainer  67 . In the peripheral face of the outer support cylinder  68  are bored tapped holes  69  with which screws are engaged. The outer support cylinder  68  is fixed to the cam cylinder retainer  67  with the screws. Also in the peripheral face of the outer support cylinder  68  are formed pin insertion openings  70  into which pins  71  are inserted and fixed. These pins  71  are engaged with cam guides cut out of a twist ring  72  shown in FIG. 21, with which a rubber cup  74  is engaged. When the twist ring  72  is turned, the rubber cup  74  together with the twist ring  72  can be extended from the binoculars  20 . The state where the rubber cup  74  is extended together with the twist ring  72  is shown in FIG. 15 with a broken line. In FIG. 14, reference numeral  75  depicts a magnification-varying ring.  
       ADVANTAGES OF THE INVENTION  
       [0054]    As explained above, the variable-powered binoculars of the present invention are, irrespective of the magnifying powers, capable of keeping constant the location where the apparent image is formed in relation to the ocular lens system, which keeps, in turn, the quality of the image constant. Another advantage is that the binoculars are capable of keeping the resolution constant from a low magnification to a high magnification, to an extent comparable to single-powered binoculars.  
         [0055]    Also, the present invention provides the binoculars of which magnifying power is varied by moving the whole ocular system, and therefore the width of the apparent visual field is constant. Due to this feature, a wide visual field can be obtained. More specifically, because conventional zoom lens binoculars typically provide an apparent visual field of less than 40° at a low magnification, the visual field is so narrow that the user has troubles in observation. On the other hand, the binoculars in accordance with the present invention have an apparent visual field of which width is constant both at a low magnification and at a high magnification. Therefore the binoculars can assure an apparent visual field of 50° or more even when the arrangement for a low magnification is employed.  
         [0056]    Moreover, because conventional zoom lens binoculars have a large difference between the eye relief at a low magnification and that at a high magnification, the user may have difficulties in observing some targets. On the other hand, the invention is able to reduce the difference. Therefore a clear observation of targets that were poorly observed with conventional binoculars can be achieved. Also, the invention provides an assurance of a longer eye relief, which is a still more advantage.