Abstract:
A gun sight includes a rangefinder that operates in a continuous-measuring mode as soon as the rangefinder is activated. Because the rangefinder is continuously determining the distance to the target when in the continuous-measuring mode, the user does not have to take any time to press any buttons in order to obtain a distance measurement to a sighted target while aiming at that target.

Description:
BACKGROUND 
   The invention relates to gun sites having rangefinders, particularly for use with rifles. 
   It is known to provide gun sights, particularly telescopic gun sights, with a rangefinder that measures the distance from the gun sight to a target within the cross hairs of the gun sight. One example of such a telescopic gun sight is shown in U.S. Pat. No. 5,771,623. The user presses a button on the side of the telescopic sight in order to turn on the rangefinder. At this point in time, the rangefinder does not attempt to take any measurements. The user then sights the target by placing the target in the cross hairs of a reticle of the telescopic sight. The user then presses the button a second time to cause the rangefinder to emit a laser beam toward the target and thus determine the distance to the target. The user is informed of the distance, and then the user can appropriately aim at the target while taking into account any bullet drop that may occur due to the distance to the target. Some rangefinders also have a continuous-measuring mode in which, after the rangefinder has been turned on (for example, by pressing a button once), the user can then hold down the button so that the rangefinder continuously emits a laser beam and thus continuously measures the distance from the telescopic sight to the object positioned in the cross hairs of the reticle. 
   A problem with presently available sights having rangefinders is that the user must press a button to cause the rangefinder to take a measurement while the user is pointing the gun on which the rangefinder is mounted at the target so that the target is in the cross hairs of the sight. Pressing the button while aiming at a target can be awkward and can cause the gun to move, which obviously adversely affects the accuracy of the shot. Pressing the button after aiming also takes a certain amount of time, and thus causes a delay in taking a shot at the target, which can cause the user to miss an opportunity at a good shot. 
   SUMMARY 
   According to aspects of the invention, a gun sight includes a rangefinder that operates in a continuous-measuring mode as soon as the rangefinder is activated. Because the rangefinder is continuously determining the distance to the target when in the continuous-measuring mode, the user does not have to take any time to press any buttons in order to obtain a distance measurement to a sighted target while aiming at that target. 
   According to one embodiment, the gun sight includes the rangefinder and a reticle through which a target is viewed. The rangefinder includes a transmitter and a receiver. The transmitter emits energy toward the target, and the receiver receives energy reflected by the target. The rangefinder determines a distance to the target from the energy received by the receiver. In one preferred embodiment, the rangefinder is a laser rangefinder having a laser transmitter and a laser receiver that receives laser light reflected by the target. 
   According to one embodiment, the rangefinder includes a default mode setting switch that enables a user to selectively place the rangefinder in either the continuous-measuring mode or a user-specified measuring mode as a default mode in which the rangefinder automatically operates when the rangefinder is activated (turned on). 
   According to another embodiment, the rangefinder includes a mode-override switch that enables a user to place the rangefinder into a user-specified-measuring mode instead of the continuous-measuring mode. 
   The rangefinder indicates the measured distance to the target. For example, the rangefinder can include a display that displays the measured distance to the target for viewing by a user of the gun sight. The display can display the measured distance on the reticle of the gun sight. According to another embodiment, the rangefinder indicates the measured distance to the target by identifying a sighting area of the reticle that should be used to aim at the target. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in conjunction with the accompanying drawings of exemplary embodiments in which like reference numerals designate like elements, and in which: 
       FIG. 1  is a perspective view of a telescopic sight according to an embodiment of the invention; 
       FIG. 2  is a block diagram showing components of a telescopic sight incorporating a rangefinder according to an embodiment of the invention; 
       FIG. 3  shows a reticle incorporated into the telescopic gun sight and on which the distance to target is displayed; and 
       FIG. 4  illustrates a reticle incorporated into another embodiment of a telescopic gun sight in which the distance to the target is indicated to the user by highlighting a sighting area of the gun sight based upon the measured distances to the target. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
     FIG. 1  is a perspective view of a telescopic gun sight  10  to which aspects of the invention can be applied. The manner in which the telescopic gun sight functions, including the particular optical arrangement used, and the manner in which its rangefinder determines the distance to object, can vary and are not critical aspects of the invention. Thus, the particular optical and other structure of the telescopic gun sight including the rangefinder are not described herein in detail. One example of a telescopic gun sight and rangefinder to which aspects of the invention can be applied is described in the above-mentioned U.S. Pat. No. 5,771,623, the disclosure of which is incorporated herein by reference in its entirety. The telescopic gun sight of U.S. Pat. No. 5,771,623 measures the distance to a target sighted in the center cross hairs of the scope&#39;s reticle (that is, the optical system for the rangefinder and for the gun sight are integrated). The rangefinder determines the distance to the target based upon the time required for an emitted light beam to travel from the rangefinder to the target and then back to the rangefinder. The invention, however, can be applied to gun sight/rangefinder systems different from what is shown in U.S. Pat. No. 5,771,623. 
   The gun sight (or scope)  10  includes an integral rangefinder  50 , a mode selection switch  60   a  or  60   b , to be described below, and one or more adjustment knobs  53  for use in adjusting the aiming point of the scope  10  after the scope has been mounted to a gun such as a rifle. For example, after mounting the scope  10  to a rifle, the one or more adjusting knobs  53  are adjusted so that the center cross hairs of the gun sight correspond to a target that will be struck by the projectile shot by the rifle at a known range (for example, 200 yards). 
     FIG. 2  is a block diagram showing main components of the rangefinder  50 . A central controller  52  controls the overall operation of the device, including the laser emitter  54 , the laser receiver  56  and the distance indicator  40 , to be described in more detail below. If the scope  10  includes a mode selection switch ( 60   a  or  60   b ), then the controller  52  operates in the mode selected by that switch. 
   As noted above, the rangefinder  50  determines the distance to a sighted target based on one-half of the measured time required for a light beam emitted by laser emitter  54  to travel from the rangefinder  50  to the target and then reflect back to the laser receiver  56 , and the speed of light in air, as is well known. The determined distance is then conveyed to the user by distance indicator  40 , which typically displays the distance (for example, in yards) on the reticle of the scope  10 . 
   Various structures can be employed as the controller  52 . For example, the controller could be an Application Specific Integrated Circuit (ASIC) or a programmed general-purpose processing unit. 
   As noted previously, existing rangefinders can operate in either a user-specified-measuring mode or in a continuous-measuring mode. The user-specified-measuring mode is a mode in which a measurement to the sighted target is made only when the user issues a command (for example, by pressing a button) to take the measurement. The determined distance then is displayed by the distance indicator  40 . The continuous-measuring mode is a mode in which the rangefinder continuously determines the distance to the sighted target, and then continuously displays the determined distance (which could vary continuously as the target moves or as the sighted area of the scope  10  is moved to different targets). As noted above, existing rangefinders only operate in the continuous-measuring mode when a control button is continuously pressed after cycling through the user-specified-measuring mode. 
   According to one aspect of the invention, the controller  52  controls the rangefinder  50  so that as soon as the rangefinder  50  is activated (turned on), the rangefinder operates in the continuous-measuring mode. Thus, the user will know the distance to target as soon as the target is placed in the sighting area of the scope  10 . The user can thus immediately know the distance to target, aim appropriately and fire, without any further manipulation or control of the rangefinder  50 . Therefore, the user can fire at the target more quickly than with existing scopes, and the user need not perform any manipulation of the scope and/or rangefinder that might adversely affect the shot by causing movement of the gun. The rangefinder operates in the continuous-measuring mode without the user continuously pressing any button or switch. In one embodiment, the mode selection switch  60   a  or  60   b  is merely an ON/OFF switch, and the controller  52  automatically places the rangefinder into the continuous-measuring mode when the ON/OFF switch is placed into the ON position. 
   It is envisioned that users still may wish to use the rangefinder in a user-specified-measuring mode in certain circumstances. Thus, according to some aspects of the invention, the rangefinder  50  includes a mode selection switch to alternately switch the mode of operation between the continuously-measuring mode and the user-specified-measuring mode. Such a switch could be provided in addition to an ON/OFF switch. 
   According to one embodiment, the mode selection switch is a default mode setting switch  60   a  that enables a user to selectively place the rangefinder  50  in either the continuous-measuring mode or in the user-specified-measuring mode as a default mode in which the rangefinder operates when the rangefinder is initially activated (turned on), for example, by a separate ON/OFF switch. Thus, when the rangefinder  50  is equipped with the default mode setting switch  60   a , the rangefinder could operate like existing rangefinders that are placed in the user-specified-measuring mode when activated, or the rangefinder could operate in the continuous-measuring mode as soon as the rangefinder is activated (turned on). 
   According to another embodiment, the rangefinder always operates in the continuous-measuring mode as soon as the rangefinder is activated, but after activation the user can actuate a mode-override switch  60   b  to place the rangefinder into the user-specified-measuring mode instead of the continuous-measuring mode. 
   In the embodiment illustrated in  FIG. 1 , the default mode setting switch  60   a  and the mode-override switch  60   b  are illustrated as two-position toggle-like switches. However, other types of switches, such as push-button switches, for example, also could be used. 
     FIG. 3  illustrates one type of reticle  20  and display  30  that can be incorporated into the scope  10 . The reticle  20  of  FIG. 3  includes cross-hairs formed from a centrally-located horizontal line and a centrally-located vertical line. The center point  22 , where these two lines intersect is the sighting area used by the rangefinder  50 . Thus, the rangefinder  50  determines the distance to the target that corresponds to the center sighting area  22 . The rangefinder  50  displays the determined distance to the target in a display area  30 . For example, the rangefinder can include an LED display that projects the distance (for example, a number indicating the yards to target) in the display area  30 , in a manner well known in the art. 
   The reticle  20  of  FIG. 3  is known as a bullet drop compensation (BDC) reticle that provides additional sighting areas  24   a ,  24   b  and  24   c  located below the center sighting area  22 . The additional sighting areas  24   a - 24   c  are used in a manner well known in the art to sight onto the target based upon the distance to the target. As known in the art, a projectile such as a bullet drops vertically as it travels through the air. Thus, the user must aim over the target as the target is located farther away from the gun. 
   Thus, as is well known in the art, once the user knows the distance to the target, the user uses one of the sighting areas  22 ,  24   a ,  24   b  or  24   c  to aim at the target depending on the distance. For example, sighting area  22  might be used if the target is located about 200 yards from the gun, whereas sighting areas  24   a ,  24   b  and  24   c  might be used if the target is located 300 yards, 400 yards or 500 yards, respectively, from the gun. Of course, the distances corresponding to the sighting areas depends on the gun and the projectile, and typically is determined by gun users based on experience. 
     FIG. 4  illustrates a different reticle  20 ′ that is similar to the  FIG. 3  reticle  20  except for the manner in which the distance-to-target is conveyed to the user. Instead of indicating the distance-to-target by displaying the yardage in a display, the  FIG. 4  embodiment highlights the appropriate sighting area based on the determined distance. In  FIG. 4 , sighting area  24   b  is highlighted by being displayed darker than the other sighting areas. The hairlines and sighting areas in the  FIG. 4  embodiment are displayed by projection onto the reticle, rather than being physical indicia such as etched lines and circles. Thus, the highlighting of the appropriate sighting area is accomplished by changing the image that is displayed. 
   Although the illustrated embodiments use a laser rangefinder, other types of rangefinders, such as rangefinders using radio waves, electromagnetic waves, sonic waves or ultrasonic waves, for example, also can be used with the invention. 
   While the invention has been described with reference to preferred embodiments thereof, it is to be understood that the invention is not limited to these embodiments or constructions. The invention is intended to cover various modifications and arrangements. While the various elements of the exemplary embodiments are shown in various combinations and configurations, other combinations and configurations, including more, less or only a single element, also are within the spirit and scope of the invention.