Abstract:
A binoculars rangefinder includes a central shaft, two eyepieces, two objective lenses, two prism modules, an optical transmitter, and an optical receiver. The eyepieces are disposed on two sides of the central shaft, allowing a first light beam reflected by an object to pass therethrough. The objective lenses are disposed on the two sides of the central shaft. The prism modules are disposed between the eyepieces and objective lenses. The optical transmitter is configured to emit a second light beam to the object. The optical receiver is configured to receive the second beam which is reflected by the object.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a rangefinder, and more particularly to a binoculars rangefinder. 
         [0003]    2. Description of the Related Art 
         [0004]    A conventional rangefinder allows a user to observe and aim at an object with only one eye, and the other eye must be closed. The user may feel uncomfortable after closing the other eye for a long period. 
         [0005]    To solve the problem described above, a binoculars rangefinder is developed such as the binoculars rangefinder disclosed in U.S. Pat. No. 8,149,507B2. A user can observe and aim at an object by both eyes through the binoculars. However, the binoculars rangefinder disclosed in U.S. Pat. No. 8,149,507B2 uses Abbe-König Prism and thus the optical path extending from the measured object to the reticle of the binoculars and the optical path extending from the reticle to the user&#39;s eyes are not coaxial (not in a line). 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    An object of the invention is to provide a binoculars rangefinder through which a user can observe and aim at a measured object by both eyes, and the measured object, a reticle of the binoculars rangefinder and the user&#39;s eyes are arranged in a line. 
         [0007]    The binoculars rangefinder in accordance with an exemplary embodiment of the invention includes a central shaft, two eyepieces, two objective lenses, two prism modules, an optical transmitter, and an optical receiver. The eyepieces are disposed on two sides of the central shaft, allowing a first light beam reflected by an object to pass therethrough. The objective lenses are disposed on the two sides of the central shaft. The prism modules are disposed between the eyepieces and objective lenses. The optical transmitter is configured to emit a second light beam to the object. The optical receiver is configured to receive the second beam which is reflected by the object. Each of the prism modules includes a first prism, a second prism, a third prism and an optical multi-layer film disposed between the first prism and the second prism. The optical multi-layer film allows the second light beam to pass therethrough and reflects the first light beam. When entering the first prism along a first axis, the first light beam is totally reflected by the first prism and reflected by the optical multi-layer film, leaves the first prism, enters the third prism, is totally reflected by the third prism, and leaves the third prism along the first axis. When entering the first prism along the first axis, the second light beam is totally reflected by the first prism, leaves the first prism, passes through the optical multi-layer film, enters the second prism, is totally reflected by the second prism, and leaves the second prism along a second axis. 
         [0008]    In another exemplary embodiment, the third prism is a roof prism. 
         [0009]    In yet another exemplary embodiment, the first prism includes a first surface, a second surface and a third surface. The second prism includes a fourth surface, a fifth surface facing the third surface and a sixth surface. The third prism includes a seventh surface facing the second surface, an eighth surface, a first roof surface and a second roof surface. The optical multi-layer film is disposed between the third surface and the fifth surface. 
         [0010]    In another exemplary embodiment, the third surface is attached to the fifth surface by adhesive. 
         [0011]    In yet another exemplary embodiment, the first light beam is visible light, and the second light beam is an infrared ray. 
         [0012]    In another exemplary embodiment, the optical transmitter includes a semiconductor laser, and the optical receiver includes an avalanche photodiode or a photodiode. 
         [0013]    In yet another exemplary embodiment, the binoculars rangefinder further includes two transmissive liquid crystal displays disposed between the eyepieces and the prism modules. 
         [0014]    In another exemplary embodiment, the binoculars rangefinder further includes two organic light emitting diodes disposed between the eyepieces and the prism modules. 
         [0015]    In yet another exemplary embodiment, the binoculars rangefinder further includes two flat glass plates disposed between the eyepieces and the prism modules. 
         [0016]    In another exemplary embodiment, the binoculars rangefinder further includes two focusing lenses disposed between the eyepieces and the prism modules. 
         [0017]    A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
           [0019]      FIG. 1A  depicts a cross section of an embodiment of a binoculars rangefinder of the invention; 
           [0020]      FIG. 1B  depicts a flat glass plate and a reticle of the binoculars rangefinder of  FIG. 1A ; 
           [0021]      FIG. 2A  is a schematic view of an optical path of visible light passing through prism modules of  FIG. 1A ; 
           [0022]      FIG. 2B  is a schematic view of an optical path of an infrared ray passing through prism modules of  FIG. 1A ; 
           [0023]      FIG. 3  depicts optical paths of the visible light and infrared ray in a receiving barrel of  FIG. 1A ; and 
           [0024]      FIG. 4  depicts an image observed through a transmissive liquid crystal display or an organic light emitting diode. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
         [0026]    Referring to  FIG. 1A , binoculars rangefinder  100  includes a transmitting barrel  10 , a receiving barrel  30  and a central shaft  50 . The transmitting barrel  10  and the receiving barrel  30  are connected to the central shaft  50 . The transmitting barrel  10  houses an eyepiece  11 , a flat glass plate  12 , a prism module  13 , a focusing lens  14 , a semiconductor laser  15  and an objective lens  16 . The receiving barrel  30  houses an eyepiece  31 , a flat glass plate  32 , a prism module  33 , a focusing lens  34 , an avalanche photodiode (APD)  35  and an objective lens  36 . The eyepiece  11  and the eyepiece  31  are disposed on two opposite sides of the central shaft  50  and symmetrical with respect to the central shaft  50 . Similarly, the flat glass plate  11  and the flat glass plate  31 , the prism module  13  and the prism module  33 , the focusing lens  14  and the focusing lens  34  are disposed on two opposite sides of the central shaft  50  and symmetrical with respect to the central shaft  50  respectively. 
         [0027]    The eyepiece  11  and the eyepiece  31 , the flat glass plate  11  and the flat glass plate  31 , the prism module  13  and the prism module  33 , the focusing lens  14  and the focusing lens  34  constitute a telescope system of the binoculars rangefinder  100 . A user can observe a measured object (not shown) through the eyepieces  11  and  31 . The distance between the eyepieces  11  and  31  can be adjusted through rotation of the transmitting barrel  10  and the receiving barrel  30  with respect to the central shaft  50 . The flat glass plates  12  and  32  have reticles  121  and  321  (as shown in  FIG. 1B ) respectively for aiming at the measured object. The focusing lenses  14  and  34  are movable so that a distance between the focusing lens  14  and the objective lens  16  and a distance between the focusing lens  34  and the objective lens  36  are adjustable for focusing. 
         [0028]    The semiconductor laser  15 , the prism module  13 , the focusing lens  14  and the objective lens  16  constitute an emitting system of the binoculars rangefinder  100 . The avalanche photodiode  35 , the prism module  33 , the focusing lens  34  and the objective lens  36  constitute a receiving system of the binoculars rangefinder  100 . When the binoculars rangefinder  100  is used for distance measurement, a user observes a measured object (not shown) through the eyepieces  11  and  31  and aims at the measured object through the reticles  121  and  321  (as shown in  FIG. 1B ). The semiconductor laser  15  emits an infrared ray which passes through the prism module  13 , the focusing lens  14  and the objective lens  16  to reach the measured object. The measured object reflects the infrared ray, and the reflected infrared ray returns to binoculars rangefinder  100  and passes through the objective lens  36 , the focusing lens  34  and the prism module  33  and is finally received by the avalanche photodiode  35 . The distance of the measured object is thereby calculated. 
         [0029]    The structure of the prism module  33  and the optical paths of the visible light and infrared ray passing through the prism module  3  are described in sequence in the following. 
         [0030]    Referring to  FIGS. 2A and 2B , the prism module  33  includes a first prism  331 , a second prism  333 , a third prism  335  and an optical multi-layer film  337 . The first prism  331  includes a first surface  3311 , a second surface  3312  and a third surface  3313 . The second prism  333  includes a fourth surface  3331 , a fifth surface  3332  and a sixth surface  3333 . The third prism  335  includes a seventh surface  3351 , an eighth surface  3352 , a first roof surface  3353  and a second roof surface  3354 . The first roof surface  3353  and the second roof surface  3354  are connected at a roof edge  3355 . The seventh surface  3351  faces the second surface  3312 , and the fifth surface  3332  faces the third surface  3313 . The optical multi-layer film  337  is disposed between the third surface  3313  and the fifth surface  3332 . The optical multi-layer film  337  only allows an infrared ray to pass therethrough, while the visible light is reflected by the optical multi-layer film  337 . The third surface  3313  is attached to the fifth surface  3332  by adhesive. 
         [0031]    When visible light  38  enters the first prism  331 , the visible light passes through the first surface  3311  and is totally reflected by the second surface  3312 . The reflected visible light  38  travels to the third surface  3313  and the optical multi-layer film  337 . Since the optical multi-layer film  337  only allows the infrared ray to pass through and reflects the visible light, the visible light  38  is reflected by the optical multi-layer film  337  to the second surface  3312  and passes through the second surface  3312  to leave the first prism  331  and enter the third prism  335 . The visible light  38  passes through the seventh surface  335  land is totally reflected by the eighth surface  3352 , the roof edge  3355  and the seventh surface  3351 . The visible light  38  passes through the eighth surface  3352  to leave the third prism  335 . The visible light  38  enters the prism module  33  and leaves the prism module  33  in the same direction and along the optical axes arranged in a line. 
         [0032]    Referring to  FIG. 2B , when entering the first prism  331 , an infrared ray  39  passes through the first surface  3311  and is totally reflected by the second surface  3312 . The reflected infrared ray  39  travels to the third surface  3313  and the optical multi-layer film  337 . Since the optical multi-layer film  337  only allows the infrared ray to pass through, the infrared ray  39  passes through the third surface  3313  and the optical multi-layer film  337  to enter the second prism  333 . The infrared ray  39  entering the second prism  333  passes through the fifth surface  3332  and is totally reflected by the sixth surface  3333 . The infrared ray  39  passes through the fourth surface  3331  to leave the second prism  333 . The infrared ray  39  enters and leaves the prism module  33  in opposite directions and along the optical axes not arranged in a line. 
         [0033]    The third prism  335  is a roof prism in this embodiment, such as a Pechan prism. 
         [0034]    When entering the prism module  33  through the first surface  3311 , the visible light  38  and the infrared ray  39  are split by the prism module  33  to travel in different directions. The visible light  38  leaves the prism module  33  through the eighth surface  3352  in the same direction as it enters the prism module  33 . However, the infrared ray  39  leaves the prism module  33  through the fourth surface  3331  in an opposite direction from the direction in which it enters the prism module  33 . In another embodiment, the infrared ray  39  enters the prism module  33  through the fourth surface  3331  and leaves the prism module  33  through the first surface  3311  in an opposite direction from the direction in which it enters the prism module  33 . The visible light  38  enters the prism module  33  through the first surface  3311  and leaves the prism module  33  through the eighth surface  3352  in the same direction as it enters the prism module  33 . 
         [0035]    In this embodiment, the prism module  13  and the prism module  33  have the same structure and are symmetrically disposed with respect to the central shaft  50 . Thus, the optical paths along which the visible light and infrared ray pass through the prism module  13  are similar to the optical paths along which the visible light and infrared ray pass through the prism module  33 . Therefore, descriptions for the prism module  33  are omitted. 
         [0036]    Referring to  FIG. 3 , the measured object reflects the visible light and infrared ray to the binoculars rangefinder  100 . When reflected by the measured object to the receiving barrel  30 , the visible light  38  and the infrared ray  39  passes through the objective lens  36  and the focusing lens  34  along a first axis  41  and enters the prism module  33  through the first surface  3311 . The infrared ray  39  is totally reflected by the second surface  3312  to pass through the third surface  3313 , the optical multi-layer film  337  and the fifth surface  3332 . The infrared ray  39  is totally reflected by the sixth surface  3333  and leaves the prism module  33  through the fourth surface  3331 . The infrared ray  39  travels along a second axis  42  and is received by the avalanche photodiode  35 . The visible light  38  is totally reflected by the second surface  3312  and afterwards reflected by the optical multi-layer film  337 . The visible light  38  leaves the prism module  33  through the second surface  3312  and enters the third prism  335  through the seventh surface  3351 . The incident visible light  38  is totally reflected by the eighth surface  3352 , the roof edge  3355  and the seventh surface  3351  and leaves the third prism  335  through the eighth surface  3352 . The visible light  38  travels along the first axis to pass through the flat glass plate  32  and the eyepiece  31 . A user can observes an image of the measured object through the eyepiece  31 . 
         [0037]    Since the optical paths of the visible light and infrared ray in the transmitting barrel  10  are similar to the optical paths in the receiving barrel  30  shown in  FIG. 1A , the optical paths in the transmitting barrel  10  are not depicted by a figure. Rather, the optical paths in the transmitting barrel  10  are described only in texts as follows. Referring to  FIG. 1A , the infrared ray emitted from the semiconductor laser  15  enters the prism module  13  through the fourth surface and leaves the prism module  13  through the first surface. The infrared ray passes through the focusing lens  14  and the objective lens  16  to reach the measured object. The measured object reflects the infrared ray back to the binoculars rangefinder  100  and the infrared ray enters the receiving barrel  30 . Also, the visible light is reflected by the measured object to enter the transmitting barrel  10 . The visible light passes through the objective lens  16  and the focusing lens  14  to enter the prism module  13  through the first surface. The visible light leaves the prism module  13  through the eighth surface and afterwards passes through the flat glass plate  12  and the eyepiece  11 , whereby a user can view an image of the measured object through the eyepiece  11 . 
         [0038]      FIG. 3  shows that the optical path extends through the flat glass plate  32  (or the reticle of  FIG. 1B ) and the eyepiece  31  to the user&#39;s eyes. That is, the measured object, the reticle and the user&#39;s eyes are arranged in a line. Therefore, the user is able to aim at the measured object with the reticle (see  FIG. 1B ) without the necessity of regulating the reticle. 
         [0039]    It is understood that the flat glass plates  12  and  32  can be replaced with transmissive liquid crystal displays or organic light emitting diodes. The cross section of the binoculars rangefinder using the transmissive liquid crystal display (or organic light emitting diode) and the corresponding optical paths of the visible light and infrared ray are not depicted by figures because they are similar to those shown in  FIGS. 1A and 3 . The difference therebetween is that the transmissive liquid crystal display or organic light emitting diode is able to show distance values  522  and  722  (as shown in  FIG. 4 ) in addition to reticles  521  and  721  (as shown in  FIG. 4 ). 
         [0040]    It is also understood that the positions of the semiconductor laser and the avalanche photodiode can be exchanged. 
         [0041]    It is also understood that the avalanche photodiode can be replaced with a photodiode. 
         [0042]    While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.