Abstract:
Disclosed is a pair of range binoculars that, when the pupil distance is adjusted, is free from a deviation of the optical axes and undesirable influences on the electronic parts resulting from vibration caused by the adjustment, is capable to show the measured distance in such a way as the user can see it easily without making the system complicated, and secures the brightness of the visual field where the measured distance is displayed. The range binoculars are characterized in that a main case and an attached case contain a pair of left and right observation optical systems and the pupil distance is adjusted by turning only the attached case, and that the main case accommodates laser range-finding means, and measured distance displaying means comprising LCD means for displaying a distance measured by said laser range-finding means and a displaying optical system for projecting the distance displayed by said LCD means on the reticle so that the distance is shown at a rim of the visual field.

Description:
TECHNICAL FIELD 
   This invention relates to range binoculars, more particularly to range binoculars that are easy to adjust the pupil distance and capable of indicating the distance between the binoculars and the object being observed. 
   BACKGROUND ART 
   Conventional range binoculars have a pair of lens barrels, one of which includes a left observation optical system and the other of which includes a right observation optical system, and a middle bridge to which each of the barrels is connected, wherein either of the barrels can turn around the middle bridge. When the user adjusts the pupil distance, s/he turns the lens barrels around the middle bridge so as to adjust the distance between the eyepieces to his/her pupil distance. 
   This adjustment means turning the whole optical axes of the observation optical systems around the middle bridge, which is accompanied by a deviation of the optical axes and undesirable influences on the electronic parts resulting from vibration caused by the turning. 
   One of the methods of displaying a measured distance used in conventional range binoculars is directly placing an LCD showing the distance on the focal plane. Another method is brightly projecting the display of an LED onto the visual field with a relay lens using the beam splitter of an erecting prism. 
   However, in the former method, because the light transmissibility of an LCD is very low, the image made by the observation optical system that also displays the distance is dark compared with the image made by the other observation optical system. As a result, the image the binoculars finally make is very obscure. On the other hand, the latter method does not lower the brightness of the image made by the observation optical system that also displays the distance. Also, the distance can be displayed at the center of the visual field. Consequently, the latter method does not make the image obscure. However, it makes the system of relays complicated and requires special LEDs, which results in an increase in production cost. 
   The object of the present invention is to remove the deficiencies conventional range binoculars have. Specifically, the objective of this invention is to provide a pair of range binoculars that, when the pupil distance is adjusted, is free from a deviation of the optical axes and undesirable influences on the electronic parts resulting from vibration caused by the adjustment. The objective pair of binoculars is also capable to show the measured distance in such a way as the user can see it easily without making the system complicated, and secures the brightness of the visual field where the measured distance is displayed. 
   DISCLOSURE OF THE INVENTION 
   In order to achieve the aforementioned objective, the present invention provides a pair of range binoculars which comprises: a first observation optical system comprising a first optical member for forming an erecting image, a first objective optical system that determines together with said first optical member a first objective optical axis, and a first ocular optical system that determines together with said first optical member a first ocular optical axis; a second observation optical system comprising a second optical member for forming an erecting image, said second member being placed parallel with said first optical member, a second objective optical system that determines together with said second optical member a second objective optical axis, and a second ocular optical system that determines together with said second optical member a second ocular optical axis; a main case accommodating said first observation optical system and said second objective optical system; an attached case accommodating said second ocular optical system and said second optical member, said attached case being placed on said main case so that said attached case can be turned round said second objective optical axis; laser range-finding means accommodated in said main case; and measured result displaying means comprising LCD means for displaying a distance measured by said laser range-finding means, said LCD means being placed at a part off a light path formed by said first observation optical system, and a displaying optical system for projecting the distance displayed by said LCD means on the reticle so that the distance is shown at a rim of the visual field. 
   One of the preferred embodiments of the invention is a pair of range binoculars recited above, wherein 
   said displaying optical system comprises a relay lens and a reflecting mirror; 
   said laser range-finding means comprises a laser emitter for emitting a laser beam to an object, a laser beam receiver for receiving the laser beam reflected by the object, and range-finding means for measuring the distance between the pair of binoculars and said object based on the length of time from the emission of said laser beam to the receiving thereof, wherein said laser emitter comprises a laser diode emitting an infrared ray, and a plate beam splitter or prism beam splitter placed on the second objective optical axis, said splitter reflecting the infrared ray emitted by the laser diode, whereby the laser beam is sent to said object through the second objective optical system, and said splitter transmitting visible light coming through the second objective optical system; 
   said first optical member is a beam splitter that separates infrared ray from visible light and takes the separated infrared ray out of the light path of said first observation optical system; 
   said laser beam receiver receives an infrared ray that was emitted by the laser emitter to an object, reflected by said object, sent into the light path of said first observation optical system, and separated by said first optical member; and 
   said laser diode and said laser beam receiver are placed in the opposite side of the second observation optical system at a part off the light path formed by said first observation optical system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view illustrating the inside structure of a pair of range binoculars  1 , which is one embodiment of the invention. 
       FIG. 2  is a sectional illustration that shows the inside structure viewed from the right in  FIG. 1 . In  FIGS. 1 and 2 , housings such as main case  11  are cut away along the face parallel to the sheets. 
       FIG. 3  is a schematic sectional view illustrating the inside structure of range binoculars  1 , which is one embodiment of the invention. In this figure, housings such as main case  11  are cut away along a face perpendicular to the face explained in  FIG. 2  above. 
       FIG. 4  is a schematic illustration that shows the functions of measured distance displaying means  45 , reticle  40  and the first ocular optical system  32 . 
       FIG. 5  is a schematic illustration that shows only the optical systems of range binoculars  1  in  FIG. 1 . 
       FIG. 6  is a schematic illustration that shows only the optical systems of range binoculars  1  in  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An embodiment of the range binoculars in accordance with this invention will be explained with reference to the figures hereafter. 
   Range binoculars  1  comprise main body  10  and attached body  20 . As observation optical system, range binoculars  1  have the first observation optical system  30  comprising the first objective optical system  31 , the first ocular optical system  32  and the first optical member  33 , and the second observation optical system  50  comprising the second objective optical system  51 , the second ocular optical system  52  and the second optical member  53 . The first observation optical system and the second observation optical system are placed parallel with each other. 
   The first objective optical axis is determined by the first objective optical system  31  together with the first optical member  33 . The first ocular optical axis is determined by the first ocular optical system  32  together with the first optical member  33 . The second objective optical axis is determined by the second objective optical system  51  together with the second optical member  53 . The second ocular optical axis is determined by the second ocular optical system  52  together with the second optical member  53 . 
   Main body  10  comprises main case  11 , a housing, which accommodates the first observation optical system  30  and the second objective optical system  51  of the above-mentioned optical systems or members. 
   Main case  11  comprises objective part  12  accommodating the first objective optical system  31  and the second objective optical system  51 , and ocular part  13  accommodating the first ocular optical system  32  and the first optical member  33 , with the ocular part integrated with the objective part. Main case  11 , which is an integrated case of objective part  12  with ocular part  13 , has a general L-shape outline in the whole entity. Ocular part  13  has a first ocular cylinder  14  accommodating the first ocular optical system  32 . Objective part  12  has a hole  15  in face  16  where ocular part  13  is placed. The axis going through the center of hole  15  is in line with the optical axis of the second objective optical system. 
   On the other hand, attached body  20  comprises attached case  21  that accommodates the second ocular optical system  52  and the second optical member  53  of the second observation optical system  50 . 
   Attached case  21  has a cylindrical shape, on one end face of which is mounted the second ocular cylinder  24  accommodating the second ocular optical system. The other end face  23  of the case is provided with an annular projection  22  that can be engaged with hole  15  formed in face  16  of objective part  12 . When annular projection  22  is engaged with hole  15 , the axis of annular projection  22  is in line with the optical axis of the second objective optical system  51 . Annular projection  22  is also provided with connecting member  25 . When annular projection  22  is engaged with hole  15  and face  16  of main body  11  is contacted with end face  23  of attached case  21 , connecting member  25  contacts with the inner wall of main case  11  and connects main case  11  with attached case  21  so that attached case  21  turns on face  16  with annular projection  22  sliding on the periphery of hole  15 . 
   Main body  10  includes laser emitter comprising laser diode  17  and plate beam splitter  18 . 
   Laser diode  17  is placed in the vicinity of that wall in objective part  12  of main case  11  which is by the side of the first observation optical system  30 . This laser diode emits an infrared ray perpendicularly to the optical axes of the first observation optical system  30  and the second observation optical system  50 . The wavelength of an infrared ray emitted by laser diode  17  may be chosen at the designer&#39;s discretion, as long as the distance between the binoculars and the observed object can be measured by the method that will be explained hereafter. An example of the wavelength is 905 nm. 
   Plate beam splitter  18  is placed on the axis of the second objective optical system  51  in objective part  12  of main case  11 . The splitter reflects an infrared ray emitted by laser diode  17  and sends the collimated ray through the second objective optical system  51  to the outside of range binoculars  1 . The splitter, on the other hand, transmits visible light coming into the optical path formed by the second objective optical system  51  from the outside of range binoculars  1  through the second objective optical system  51 , and guides the visible light to the second optical member  53 . A prism beam splitter that has the same or similar function as a plate beam splitter may be used in place of plate beam splitter  18 . 
   Each of the first objective optical system  31  and the second objective optical system  51  is comprised of a group of objective lenses made of a combination of plural lenses. The groups of objective lenses are fixed in the first objective cylinder  34  and the second objective cylinder  54  respectively. These objective optical systems may be the same as those used in conventional binoculars or range binoculars. 
   Each of the first ocular optical system  32  and the second ocular optical system  52  is comprised of a group of ocular lenses made of a combination of plural lenses. As explained hereinbefore, the first ocular optical system  32  is fixed in the first ocular cylinder  14  mounted on ocular part  13  of main case  11 , while the second ocular optical system  52  is fixed in the second ocular cylinder  24  mounted on attached case  21 . These ocular optical systems may be the same as those used in conventional binoculars or range binoculars. 
   As shown in  FIG. 5 , the second optical member  53  is a known Porro II erecting prism made by a combination of the second upper prism  55 , the second side prism  56  and the second lower prism  57 . The second optical member  53  is placed in such a position as a ray coming through the second objective optical system enters into the second upper prism  55 , the second side prism  56  and the second lower prism  57  in this order and then is sent to the second ocular optical system  52 . Due to this structure of the second optical member  53 , the second observation optical system  50  has the second ocular optical system  52  of which optical axis is not in line with the optical axis of the second objective optical system  51 . 
   As shown in  FIG. 5 , similar to the structure of the second optical member  53 , the first optical member  33  comprises a Porro II erecting prism made by a combination of the first upper prism  35 , the first side prism  36  and the first lower prism  37 , and further a rectangular prism  38 . Rectangular prism  38  is set to the Porro II erecting prism with the bottom face thereof contacted with the bottom face of the first lower prism  37 . This combination of the first lower prism  37  with rectangular prism  38  makes a beam splitter  39 . Consequently, the first optical member  33  has, in addition to the same function as the second optical member  53  has, the function of a beam splitter, which transmits an infrared ray and reflects visible light. Due to these functions of the first optical member  33 , of an infrared ray that is emitted by the laser diode to the outside of range binoculars  1 , reflected and returned by the object, and comes into the optical path of the first observation optical system  30  through the first object optical system  31 , and visible light that is reflected by the object and comes into the optical path of the first observation optical system  30  through the first object optical system  31 , only the visible light is reflected by beam splitter  39  and sent to the first ocular optical system  32 , while the infrared ray is transmitted by beam splitter  39  and guided to the outside of the first observation optical system  30 . 
   Between the first optical member  33  and the first ocular optical system  32  of the first observation optical system  30  is placed reticle  40 . Reticle  40  is provided with a mill scale. 
   As shown in  FIG. 1 , main body  10  has laser beam receiver  41 , which is a photodetector that receives an infrared ray separated by the first optical member  33 , at a position near the inner wall on the side where laser diode  17  is placed. 
   Main body  10  further has range-finding means (not shown in the figures) for measuring the distance between the observer and the object based on the length of time from the emission of an infrared ray with laser emitter  17  to the receiving thereof with laser beam receiver  41 . For the range-finding means may be used known means. These means are taught by, for example, Japanese 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. 
   As shown in  FIGS. 4 and 6 , measured distance displaying means  45  is placed at a position above the optical axis of the first ocular optical system  32 , the position being off the optical path of the first observation optical system  30 .  FIG. 4  is a schematic illustration of that part shown in  FIGS. 1–3  which includes measured distance displaying means  45 , reticle  40  and the first ocular optical system  32 . Measured distance displaying means  45  comprises LCD means  42 , connected with the range-finding means, for displaying the distance between the observer and the object measured by said range-finding means, and relay lens  43  and reflecting mirror  44 , which comprise a displaying optical system for projecting the distance displayed by said LCD means on reticle  40 . In this application the abbreviation “LCD” means liquid crystal display. An image made by LCD means  42  is projected onto reticle  40  through relay lens  43  and by reflecting mirror  44 . Reflecting mirror  44  may be placed at a given position as long as it is within the visual field formed by the first ocular optical system. Preferably, the reflecting mirror should be placed at a rim of the visual field so that it does not obstruct the observed object. 
   Range binoculars  1 , which has the aforementioned structural features, functions as follows. 
   As shown in  FIG. 2 , the pupil distance is adjusted through the rotation of attached body  20 . As mentioned hereinbefore and shown in  FIG. 1 , the axis of annular projection  22  is in line with the optical axis of the second objective optical system  50 . Consequently, when the second optical member  53  and the second ocular optical system  52  are simultaneously turned through the rotation of attached body  20 , rays coming along the optical axis of the second objective optical system  51  enter the second optical member  53  always by the same point. This means that the rotation of attached body  20  does not change the image obtained in the second observation optical system  50 . Also, since the optical axis of the second objective optical system  51  is not in line with the optical axis of the second ocular optical system  52 , when attached body  20  is rotated, the optical axis of the second ocular optical system  52  included in attached body  20  turns, drawing a circular arc of which center is on the axis of the second objective optical system  51  and of which radius corresponds to the differential between the optical axis of the second objective optical system  51  and that of the second ocular optical system  52 . Since the optical axis of the second objective optical system exists in main case  11 , separate from attached body  20 , together with the optical axis of the first objective optical system  31  and that of the first ocular optical system  32 , when attached body  20  is rotated, the distance between the optical axis of the second objective optical system  51  and that of the first ocular optical system  32  is not changed. In summary, when attached body is rotated, the distance between the optical axis of the second ocular optical system  52  and that of the first ocular optical system  32  is changed, which means the distance between the second ocular cylinder  24 , accommodating the second ocular optical system  52 , and the first ocular cylinder  14 , accommodating the first ocular optical system  32 , is changed. 
   In  FIG. 6 , the second ocular cylinder  24  may take, for example, position a, b or c, by the rotation of attached body  20 . In this figure, the distance between the first ocular cylinder  14  and the second ocular cylinder  24 , which is the pupil distance, is smallest when the second ocular cylinder  24  takes position a, and largest when position c. In this way, the pupil distance can be adjusted without affecting the visual field. 
   The user can observe an object with range binoculars  1  in the same way as with ordinary binoculars. When an object is observed with range binoculars  1 , visible light reflected by the object comes into the binoculars through the first objective optical system  31  and the second objective optical system  51 . The visible light coming into range binoculars  1  through the first objective optical system  31  proceeds along the optical path determined by the first objective optical system  31 , and enters the first optical member  33 , which has the function of a beam splitter. Since beam splitter  39  of the first optical member  33  reflects visible light as shown in  FIG. 5 , the visible light is reflected by beam splitter  39  and sent to the first ocular optical system  32  through the optical path determined by the first ocular optical system  32 . On the other hand, the visible light coming into range binoculars  1  through the second objective optical system  51  proceeds along the optical path determined by the second objective optical system  51  to plate beam splitter  18 . Since plate beam splitter  18  transmits visible light, the visible light travels through plate beam splitter  18 , advances through the second optical member  53  and reaches the second ocular optical system  52  via the optical path determined by the second ocular optical system  52 . In this way, the same image of the object can be made by each of the left and right optical systems. 
   The measurement of the distance between the observer and an object with range binoculars  1  is carried out in the following way. First, the object is brought into focus. Then, plate beam splitter  18  is irradiated with an infrared ray produced by laser diode  17 . Since plate beam splitter  18  reflects infrared rays as shown in  FIG. 5 , the infrared ray emitted by laser diode  17  is reflected by plate beam splitter  18  and sent to the object through the second objective optical system  51 . The infrared ray is reflected by the object and sent into range binoculars  1  through the first objective optical system  31 . The incoming infrared ray proceeds along the path determined by the first objective optical system and enters the first optical member  33 , which has a beam splitting function. Since infrared rays travel through beam splitter  39  of the first optical member  33 , the infrared ray is transmitted by beam splitter  39  and guided to the outside of the first observation optical system  30 . Then, the infrared ray is received and detected with laser beam receiver  41 . The distance between the observing point and the object is calculated based on the length of time from the emission by laser diode  17  to the detection with laser beam receiver  41 . 
   When the calculation is finished, a signal indicating the distance is sent to LCD means  42  included in measured distance displaying means  45 , whereby the distance is displayed by LCD means  42 . The image, which was produced by LCD means  42  and indicates the distance, is sent to reflecting mirror  44  through relay lens  43 , reflected by reflecting mirror  44  and guided to the first ocular optical system  32 . Reflecting mirror  44  is placed at a position near a rim of the visual field made by the first ocular optical system  32 , which results in a distance display without interfering with the observation of an object. Also, since the distance display method of range binoculars  1  does not mar at all the visual field other than the distance displaying part with reflecting mirror  44 , the image made by the first observation optical system, which also shows the distance, is not darkened. 
   Further, from the distance calculated in the above-mentioned method and the indication of the mill scale fixed to reticle  40  can be calculated the size of the object that is observed. 
   Hereinbefore has been explained one example of this invention. Needless to say, the invention is not limited to this example only but can be worked with suitable modification to the shape and structure unless it departs from the essential requirements of the invention. 
   Since the first observation optical system and the second observation optical system of the range binoculars in accordance with this invention are accommodated in one case, the positional relationship between these optical systems is not changed when the pupil distance is adjusted, which means pupil distance adjustment does not cause a deviation of the optical axes. 
   The pupil distance of the range binoculars in accordance with this invention is adjusted through the rotation of the attached body. Therefore accommodating such electronic parts as a laser diode or laser beam receiver in the main case can reduce harmful influences of that vibration on these electronic parts which is caused by the rotation for pupil distance adjustment. This feature makes possible a reliable measurement of the distance between the observer and the object being observed. Also, the electronic parts can be placed along one inner wall of the main case, which makes the adjustment of the parts easy. 
   Since ordinary LCDs and simple relays can be used for the distance display, the production cost of the range binoculars in accordance with the invention can be reduced. 
   The range binoculars of this invention can provide an image which is the same as or similar to that made by an ordinary binoculars other than the distance display part. In other words, the range binoculars do not have such defect as the image is not clearly seen because, for example, the image is darkened. 
   Further, by providing the reticle with a mill scale, the size of an object being observed can be calculated from the distance measured and the indication of the mill scale.