Abstract:
The range binoculars include first and second observing optical systems, a laser beam-emitter for emitting a laser beam, a measuring optical system for collimating the laser beam and sending the collimated laser beam to a target. A laser beam-receiving device receives the laser beam reflected by the target, while a distance-determining device determines the distance between the observation place and the target from the flight time of the laser beam taken from the laser beam-emitter to the laser beam-receiver. A measurement-displaying device displays the measurements obtained by the distance-determining device.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to range binoculars, more particularly, the invention relates to a pair of binoculars having an optical system that measures distance and an optical system for observation. 
   2. Background Art 
   Typically, conventional range binoculars emit an infrared ray as a distance-measuring laser beam, collimate and aim the emitted infrared ray at a target, then receive a reflected ray from the target, measure the flight time taken from the ray-emitting point to the reflected ray-receiving point, and determine the distance from the observation place, i.e., the ray-emitting point to the target. 
   Conventional range binoculars are provided with a beam splitter, which permits an infrared ray to be transmitted, but does not permit visible rays to be transmitted between the objective lens of the optical system for observation and the erecting prism. As such, the infrared ray beam goes to the beam splitter, is reflected, and returns to the objective lens. The beam is collimated by the objective lens and transmitted to the target. Furthermore, in the conventional range binoculars, visible rays entering the objective lens for observation go through the beam splitter and advance to the eyepieces at which an image is formed. 
   The beam splitter used in the conventional range binoculars is required to assure the reflection of the distance-measuring infrared ray thereon and, at the same time, the transmission of the observed visible rays through itself at a high transmittance. Thus, the beam splitter is required to have a high performance. 
   To produce such high performance beam splitters is technically difficult, thereby resulting in high production costs. Consequently, conventional range binoculars using such beam splitters are rather expensive. 
   Furthermore, such high performance beam splitters are not able to transmit all of the visible rays reaching the beam splitters. Thus, conventional range binoculars, due to the presence of the beam splitter, inevitably reduce the transmittance of the observed visible rays and the resolving power thereof. As a result, images are degraded using conventional range binoculars. 
   The focusing mechanism of binoculars is of an independent feeding type (IF Type) or a central feeding type (CF Type). It is well known in the industry that focusing is easier with the CF Type binoculars than with the IF Type binoculars. In CF Type binoculars, an internal focusing lens is inserted between the objective lens and the erecting prism. The user focuses by moving the focusing lens. Therefore, the CF Type binoculars must be provided with the internal focusing lens and a means for moving in a space between the objective lens and the erecting prism. 
   However, it is very difficult and almost impossible to find a space to place an internal focusing lens in such conventional range binoculars, because the beam splitter is already fixed between the objective lens and the erecting prism. Thus, conventional rangefinder binoculars can hardly use the CF Type focusing systems, which is disadvantageous. 
   SUMMARY OF THE INVENTION 
   An object of the invention is to overcome the above-described drawbacks of conventional range binoculars. It is also an object of the invention to provide a pair of range binoculars which can be produced at a lower cost, has a lower degree of image degradation, and uses CF Type focusing means. 
   In order to achieve the above-described objects, the invention provides a pair of range binoculars, which includes a first observing optical system separate from a second observing optical system. An emitting device emits a laser beam to measure a distance, while a rangefinder optical system, provided separately from the first and second observing optical systems, collimates the emitted laser beam and aims the laser beam at a target. A laser beam-receiver receives the laser beam reflected by the target so a distance-measuring device can determine a distance from the observation place to the target. A display indicates the distance obtained by the distance-measuring device. 
   The rangefinder optical system includes a reflecting mirror for reflecting the laser beam emitted by the emitting device to the distance-measuring device and a collimating lens for collimating the distance-measuring laser beam reflected from the mirror. The first observing optical system includes a first objective optical member, a first eyepiece optical member, and a first optical member for assembling an image of the visible rays from the first objective optical member and sending the image to the first eyepiece optical member. The second observing optical system includes a second objective member, a second eyepiece member, and a second optical member for assembling an image of the visible rays from the second objective optical member and sending the image to the second eyepiece optical member. 
   The first and second optical members are beam splitters, which separate the distance-measuring laser beam and the visible rays entering the observing optical system from each other to remove the distance-measuring laser beam from the light path of the observing optical system before it is sent to the distance-measuring device. 
   A body case and an attachment case are provided with the body case having the first observing optical system and the second objective optical member contained therein. The attachment case, which has the second eyepiece optical member and the second optical member, is connected with the body case to allow the attachment case to rotate around the axis of the second objective optical member. The distance-measuring laser beam can generate an infrared ray. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a cross-sectional plan view of the range binoculars according to an embodiment of the invention; 
       FIG. 2  is a cross-sectional plan view of the left side of the range binoculars shown in  FIG. 1 ; 
       FIG. 3  is a schematic diagram illustrating the optical system of the range binoculars shown in  FIG. 1 ; and 
       FIG. 4  is a schematic diagram illustrating the relationship between the field of view and the LCD. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1 and 2  illustrate the structural configuration of the range binoculars according to a preferred embodiment of the invention.  FIG. 1  is a cross-sectional plan view of range binoculars  1 .  FIG. 2  is a cross-sectional plan view of the left side of a part of the range binoculars  1 . The range binoculars  1  include body case  11 , attachment case  21  and outer case  101 . 
   The body case  11  and a body  10  of the range binoculars  1  are contained in the outer case  101 . The body  10  includes a first optical system. The range binoculars  1  also include an attachment  20  contained in the attachment case  21 , wherein the attachment  20  includes a second optical system. 
   The range binoculars  1  include a pair of observing optical systems, that is, first and second observing optical systems. The first observing optical system  30  includes a first objective optical member  31 , first eyepiece optical member  32 , first internal focusing lens  63  and first optical member  33 . The second observing optical system  50  includes a second objective optical member  51 , second eyepiece optical member  52 , second internal focusing lens  64  and second optical member  53 . 
     FIG. 3  is a schematic diagram illustrating the first and second observing optical systems of the range binoculars  1  shown in FIG.  1 . 
   As shown in  FIG. 1 , the first objective optical member  31 , first internal focusing lens  63 , and first optical member  33  form an optical axis of a first objective optical system, and the first eyepiece optical member  32  and first optical member  33  form an optical axis of the first eyepiece optical system. The second objective optical member  51 , second focusing lens  64 , and second optical member  53  form an optical axis of the second objective optical system, and the second eyepiece optical member  52  and second optical member  53  form an optical axis of the second eyepiece optical system. 
   The body  10  of the binoculars  1  contains the first observing optical system  30  and the second objective optical member  51  of the second observing optical system  50 . The body case  11  surrounds the body  10  as an outer structural member. 
   The body case  11  includes the objective part  12 , which contains the first objective optical member  31  and the second objective optical member  51 , and the eyepiece part  13 , which contains the first eyepiece optical member  32  and the first optical member  33 . The eyepiece part  13  is integrally connected to the objective part  12 . The eyepiece part  13  includes a first eyepiece cylindrical frame  14 , which contains the first eyepiece optical member  32 . A face  16  provided on the eyepiece part  13  includes a hole  15 , wherein an axis of the hole  15  coincides with the optical axis of the second objective optical system. 
   The attachment  20  includes the second eyepiece optical member  52  and second optical member  53  of the second observing optical system  50 , which are contained by the attachment case  21  as an outer structural member. 
   The attachment case  21  includes a second eyepiece cylindrical frame  24 , which contains the second eyepiece optical member  52  at one end face thereof, and, at another end face  23 , a circular projection  22 , which can engage the hole  15  provided in the face  16  of the objective part  12 . The axis of the circular projection  22  coincides with the optical axis of the second objective optical member when the circular projection  22  engages the hole  15 . The circular projection  22  is provided with a connecting member  25 . The connecting member  25  contacts the inner wall of body case  11  when the circular projection  22  is inserted in the hole  15  and the face  16  of the body case  11  contacts the face  23  of the attachment case  21 . The connecting member  25  is a means for connecting the body case  11  and attachment  21  with each other, thereby allowing the attachment case  21  to rotate within the hole  15  of the body case  11 . 
   The body  10  further includes a laser diode  17 , which is a laser beam-emitting means, and a distance-measuring optical system  18 . 
   The distance-measuring optical system  18  is provided such that an optical axis of the system  18  is parallel to optical axes of the first observing optical system  30  and the second observing optical system  50  at a position between the second observing optical system  50  and a side wall of distance-measuring optical system  18  adjacent to the second observing optical system  50  in the objective part  12  of the body case  11 . The distance-measuring optical system  18  includes a mirror  61  and collimating lens  62 . The mirror  61  reflects a distance-measuring laser beam emitted by the laser diode  17  and sends the reflected distance-measuring laser beam to the collimating lens  62 , which collimates the distance-measuring laser beam reflected from the mirror  61 . Preferably, the collimating lens  62  includes two lenses, however, it is within the scope of this invention to vary the number of lenses used, so long as the above-described function is not lost. Similarly, it is within the scope of the invention to use any suitable lens capable of collimation as the collimating lens  62 . 
   Thus, the range binoculars  1  have a distance-measuring system  18 , first observing optical system  30 , and second observing optical system  50 . 
   The laser diode  17  is fixed under the mirror  61  can aim an infrared ray, also known as the distance-measuring laser beam, at the mirror  61 . The wavelength of the infrared ray emitted by the laser diode  17  is, for example, 905 nm, and may be any suitable wavelength as long as distance measurement is possible using the measuring method mentioned below. 
   In the range binoculars according to this invention, it is not necessary to always send the distance-measuring laser beam from the laser diode, through the mirror, to the collimating lens. Rather, the distance-measuring laser beam may be sent directly from the laser diode to the collimating lens, that is, without any mirrors therebetween. 
   Moreover, it is within the scope of the invention to position the laser beam-emitting part and distance-measuring optical system anywhere within the range binoculars. 
   The first objective optical member  31  and the second objective optical member  51  each includes a lens group having a plurality of objective lenses. It is within the scope of the invention to have the first objective optical member  31  and the second objective optical member  51  be substantially similar to objective optical members used in conventional range binoculars. 
   The first eyepiece optical member  32  and the second eyepiece optical member  52  each includes a lens group having a plurality of eyepieces. As mentioned above, the first eyepiece optical member  32  is mounted on the first eyepiece cylindrical frame  14  inserted in the eyepiece part  13  of the body case  11 . The second eyepiece optical member  52  is mounted on the second eyepiece cylindrical frame  24  inserted in the attachment case  21 . Similarly, it is within the scope of the invention to have the first eyepiece optical member  32  and the second eyepiece optical member  52  be substantially similar to eyepiece optical members used in conventional range binoculars. 
   The first internal focusing lens  63  is fixed between the first objective optical member  31  and the first optical member  33  wherein the optical axis of the first internal focusing lens  63  is aligned with the optical axis of the first objective optical member  31 . The second internal focusing lens  64  is provided between the second objective optical member  51  and the second optical member  53  wherein the optical axis of the second internal focusing lens  64  is aligned with the optical axis of the second objective optical member  51 . The first internal focusing lens  63  and second focusing lens  64  are fixed to a frame  66  of focusing lens-moving means  65  provided between the first observing optical system  30  and the second observing optical system  50 . Operating the focusing lens-moving means  65  moves the frame  66 , which, in turn, allows the first internal focusing lens  63  and second focusing lens  64  to travel together in a direction of the first objective optical member  31  and the second objective optical member  51 , or in the direction of the first optical member  33  and the second optical member  53 . Thus, the focus of the first observing optical system  30  and the second observing optical system  50  is controlled. That is, the range binoculars  1  use a CF Type of focusing method. 
   As shown in  FIG. 3 , the second optical member  53 , which is commonly known as a Porro II erecting prism, includes an assembly of a second upper prism  55 , second side prism  56 , and second lower prism  57 . The assembly of prisms is positioned such that a ray coming through the second objective optical system enters the second objective optical member  51  and passes sequentially through second upper prism  55 , second side prism  56  and second lower prism  57 , and is then sent to the second eyepiece optical system. Due to the structural arrangement of the second optical member  53 , the second eyepiece optical member  52  of the second observing optical system  50  has an optical axis that is not aligned with the optical axis of the second objective optical member  51 . 
   Similarly, the first optical member  33 , which is commonly known as a Porro II erecting prism, has a structure that is identical to the structure of the second optical member  53 . In particular, the structure of the first optical member  33  includes a first upper prism  35 , first side prism  36 , and first lower prism  37 , but further includes a rectangular prism  38 , as shown in  FIG. 3. A  bottom face of the rectangular prism  38  contacts a bottom face of the first lower prism  37 . The assembly of the first lower prism  37  and the rectangular prism  38  form a beam splitter  39 . Therefore, the first optical member  33  has, in addition to the same function as the second optical member  53 , the function of a beam splitter, which transmits an infrared ray and reflects visible light. Due to the beam splitting function of the first optical member  33 , an infrared ray, which is emitted by the laser diode away from the range binoculars  1 , reflected by an object back to the binoculars  1  and into the optical path of the first observing optical system  30  through the first object optical member  31 , is transmitted by the beam splitter  39  and guided to the outside of the first observing optical system  30 . On the other hand, visible light, which is reflected by the object back into the optical path of the first observing optical system  30  through the first object optical member  31 , is reflected by the beam splitter  39  and sent to the first eyepiece optical member  32 . 
   As shown in  FIG. 3 , the focusing plate  67  is provided between the first optical member  33  and the first eyepiece optical member  32  of the first observing optical system  30 . 
   The body  10  further includes a laser beam-receiving means  41  disposed near an inner wall on the side where laser diode  17  is placed. The laser beam-receiving means  41  is a photodetector which receives, for example, an infrared ray separated by the first optical member  33 , as mentioned above. 
   Furthermore, the body  10  has a range-finding means (not shown), connected to the laser diode  17  and laser beam-receiving means  41  for determining a distance between the observer and the target. The distance is determined based on the flight time of the infrared ray from the emission of the infrared ray by the laser diode  17  to reception by the laser beam-receiving means  41 . A range-finding means, for example, the range-finding means disclosed in JP Translated PCT Application Publication No. 10-512954(1998), U.S. Pat. Nos. 5,574,552, 5,612,779, 5,623,335, 5,652,651 or 5,740,952. 
   An LCD  42  is mounted on the focusing plate  67  for displaying the measurement result. The LCD  42 , which is connected to the range-finding means, displays the distance between the observation place and the target or object. The LCD  42  is disposed such that a display window  69  of the LCD  42  appears at a lower part of a view  68  formed on the focusing plate  67 . 
   Operation of the above-described range binoculars  1  is provided below. 
   A pupil distance is adjusted by rotating the attachment  20 . As mentioned above, the axis of the circular projection  22  is aligned with the optical axis of the second objective optical member  51 . Consequently, when the second optical member  53  is turned by rotating the attachment  20 , rays traveling along the optical axis of the second objective optical member  51  always enter the second optical member  53  at the same point. This means that the rotation of the attachment  20  does not change the image obtained in the second observing optical system  50 . Also, since the optical axis of the second objective optical member  51  is not aligned with the axis of the second eyepiece optical member  52 , when the attachment  20  is rotated, the optical axis of the second eyepiece optical member  52  included in the attachment  20  turns, drawing a circular arc having a center on the axis of the second objective optical member  51  and having a radius corresponding to a difference between the optical axis of the second objective optical member  51  and the optical axis of the second eyepiece optical member  52 . Since the optical axis of the second objective optical member  51  is provided in the body case  11 , separate from the attachment  20 , together with the optical axis of the first objective optical member  31  and the optical axis of the first eyepiece optical member  32 , when the attachment  20  is rotated, the distance between the optical axis of the second objective optical member  51  and the optical axis of the first eyepiece optical member  32  is not changed. In summary, when the attachment  20  is rotated, the distance between the optical axis of the second eyepiece optical member  52  and the optical axis of the first eyepiece optical member  32  is changed, which means the distance between the second eyepiece cylindrical frame  24  accommodating the second eyepiece optical system  52 , and the first eyepiece cylindrical frame  14  accommodating the first eyepiece optical member  32 , is changed. Thus, the pupil distance in the range binoculars  1  can be adjusted without affecting the visual field. 
   The user observes an object with the range binoculars  1  of the invention in the same way as with conventional binoculars. When an object is observed with the range binoculars  1  of the invention, visible light reflected by the object enters the binoculars through the first and second objective optical members  31  and  51 . The visible light entering the first observing optical system  30  through the first objective optical member  31  proceeds along the optical path determined by the first objective optical member  31 , and enters the first optical member  33 , which functions as a beam splitter. Since the beam splitter  39  of the first optical member  33  reflects visible light, the visible light is reflected by the beam splitter  39  and sent to the first eyepiece optical member  32  along the optical path determined by the first eyepiece optical member  32 . Visible light entering the second observing optical system  50  through the second objective optical member  51  proceeds along the optical path determined by the second objective optical member  51  to the second optical member  53 , advances through the second optical member  53 , and reaches the second eyepiece optical member  52  via the optical path determined by the second eyepiece optical member  52 . In this way, the same image of the object is made by each of the left and right optical systems. 
   As mentioned above, the range binoculars  1  do not have a beam splitter provided between the second objective optical member  51  and the second optical member  53 , as is typical in conventional binoculars. Therefore, the visible light entering the second observing optical system  50  through the second objective optical member  51  reaches the second eyepiece optical member  52  without passing through the beam splitter. Thus, the range binoculars  1  do not reduce the transmission amount of visible light or the resolving power. Consequently, the second observing optical system  50  also produces clear images. 
   The measurement of the distance between the observer and an object using the range binoculars  1  is carried out in the following way. First, the object is brought into focus. Then, the mirror  61  is irradiated with an infrared ray produced by the laser diode  17 . The mirror  61  reflects the infrared ray, which is then sent to the collimating lens  62 . The infrared ray, collimated with the collimating lens  62 , advances to the object. The infrared ray is reflected by the object and sent to the range binoculars  1  through the first objective optical member  31 . The incoming infrared ray proceeds along the path determined by the first objective optical member and enters the first optical member  33 , which performs a beam splitting function. Since the infrared rays travel through the beam splitter  39  of the first optical member  33 , the infrared ray is transmitted by the beam splitter  39  and guided to the outside of the first observation optical system  30 . Then, the infrared ray is received and detected by the laser beam-receiving means  41 . The distance between the observing point and the object is calculated by the range-finding means based on the length of time from the emission of an infrared ray by the laser diode  17  to the detection of the reflected ray by the laser beam-receiving means  41 . 
   When the calculation is finished, a signal indicating the distance is sent to the LCD  42 , wherein the distance is shown on the display window  69  of the LCD  42 . The displayed distance appears at a lower part of view  68 , which is obtained from the first observing optical system  30 . As a result, the user sees the distance on the display. 
   Hereinbefore has been explained an embodiment of the invention. Needless to say, the invention is not limited to the discussed embodiment only but can be suitably modified without departing from the scope of the invention. 
   For example, for the method of displaying the result of the measurement, a bright LED display may be formed in the view field  68  by a relay lens together with the beam splitter of the erecting prism. Alternatively, as disclosed in JP Utility Model 3074643, an LCD, reticle, relay lens, and reflecting mirror may be arranged so an image displayed on the LCD is reflected onto the reticle through the relay lens and reflecting mirror. The use of the relay lens prevents the LCD itself from coming into the view field, which results in the display of the measurement with little influence on observations. 
   The range binoculars  1  in accordance with the invention separate the observing optical systems from the distance-measuring system. Therefore, it is not necessary to have an expensive beam splitter to send a distance-measuring laser beam. Further, the collimating lens used to collimate a distance-measuring laser beam in the range binoculars  1  of the invention need not have any observation function. Therefore, a cost-effective lens, such as a plastic lens, may be used. These features of the invention advantageously reduce the production cost of the range binoculars  1 . 
   The range binoculars  1  in accordance with the invention do not provide a beam splitter between the objective optical member and the erecting prism. Therefore, visible light needed for observation reaches the eyepiece optical member without passing through any beam splitters. As such, the transmission of visible light or the resolving power is not reduced. A clear image is also obtained through the second observing optical system. 
   Since the range binoculars  1  in accordance with the invention does not have a beam splitter between the objective lens and the erecting prism, it is possible to place the internal focusing lens and corresponding moving means between the objective lens and the erecting prism. Thus, the CF type focusing mechanism, which can easily control the focusing, is used in the range binoculars  1  of the invention.