U.S. patent application number 11/021966 was filed with the patent office on 2005-11-03 for common aperture time-division-multiplexed laser rangefinder.
This patent application is currently assigned to Raytheon Company, a corporation of the state of Delaware. Invention is credited to Staley, John R. III.
Application Number | 20050241207 11/021966 |
Document ID | / |
Family ID | 34964892 |
Filed Date | 2005-11-03 |
United States Patent
Application |
20050241207 |
Kind Code |
A1 |
Staley, John R. III |
November 3, 2005 |
Common aperture time-division-multiplexed laser rangefinder
Abstract
An optical rangefinder includes an optical portion for directing
optical radiation from a generator to and through an optical
aperture, and for directing reflected energy of the optical
radiation that is received back through the aperture to a detector,
the optical portion having an optical switch. In a first
operational mode the optical switch routes optical radiation from
the generator in a manner that facilitates the directing of the
optical radiation to and through the optical aperture, and in a
second operational mode the optical switch routes the reflected
energy in a manner that facilitates the directing of the reflected
energy to the detector. A control portion is responsive to the
detector, and controls the generator and the optical switch.
Inventors: |
Staley, John R. III;
(Dallas, TX) |
Correspondence
Address: |
Raytheon Company
Intellectual Property & Licensing, EO/E04/N119
2000 East El Segundo Boulevard
PO BOX 902
El Segundo
CA
90245-0902
US
|
Assignee: |
Raytheon Company, a corporation of
the state of Delaware
|
Family ID: |
34964892 |
Appl. No.: |
11/021966 |
Filed: |
December 23, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60552262 |
Mar 10, 2004 |
|
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Current U.S.
Class: |
42/105 |
Current CPC
Class: |
F41G 3/065 20130101;
F41G 1/48 20130101; G01S 7/4812 20130101 |
Class at
Publication: |
042/105 |
International
Class: |
F41C 027/06 |
Claims
What is claimed is:
1. An apparatus comprising an optical rangefinder that includes: an
optical aperture; a generator that can emit optical radiation; a
detector responsive to optical radiation; an optical portion for
directing optical radiation from said generator to and through said
aperture, and for directing reflected energy of the optical
radiation that is received back through said aperture to said
detector, said optical portion having an optical switch with first
and second operational modes, wherein in said first operational
mode said optical switch routes optical radiation from said
generator in a manner that facilitates said directing of the
optical radiation to and through said optical aperture, and in said
second operational mode said optical switch routes the reflected
energy in a manner that facilitates said directing of the reflected
energy to said detector; and a control portion that is responsive
to said detector and that controls said generator and said optical
switch.
2. An apparatus according to claim 1, wherein said generator emits
infrared radiation, and said detector is responsive to infrared
radiation.
3. An apparatus according to claim 2, wherein said generator
includes an infrared laser.
4. An apparatus according to claim 2, including a further aperture,
said optical portion directing visible radiation received through
said optical aperture along an optical path extending to and
through said further aperture.
5. An apparatus according to claim 4, wherein said optical portion
includes a beam splitter disposed along said optical path between
first and second portions thereof; and wherein said beam splitter
causes visible radiation arriving at said beam splitter from said
optical aperture along said first portion of said optical path to
thereafter travel away from said beam splitter toward said further
aperture along said second portion of said optical path, causes
infrared radiation arriving at said beam splitter along said first
portion of said optical path to thereafter travel away from said
beam splitter toward said optical switch along a further path, and
causes infrared radiation that arrives at said beam splitter along
said further path to thereafter travel away from said beam splitter
along said first portion of said optical path.
6. A method of operating an optical rangefinder having an optical
aperture, an optical radiation generator, an optical radiation
detector, and an optical switch, comprising: directing optical
radiation from said generator to and through said optical aperture,
including operating said optical switch in a first operational mode
in which said optical switch routes optical radiation from said
generator in a manner that facilitates said directing of the
optical radiation to and through said optical aperture; and
directing reflected energy of the optical radiation that is
received back through said optical aperture to said detector,
including operating said optical switch in a second operational
mode in which said optical switch routes the reflected energy in a
manner that facilitates said directing of the reflected energy to
said detector.
7. A method according to claim 6, including: causing said radiation
emitted by said generator to be infrared radiation; and causing
said detector to be responsive to infrared radiation.
8. A method according to claim 7, including directing visible
radiation received through said optical aperture along an optical
path extending to and through a further aperture.
9. A method according to claim 8, including: providing a beam
splitter along said optical path between first and second portions
thereof; causing visible radiation arriving at said beam splitter
from said optical aperture along said first portion of said optical
path to thereafter travel away from said beam splitter toward said
further aperture along said second portion of said optical path;
causing infrared radiation arriving at said beam splitter along
said first portion of said optical path to thereafter travel away
from said beam splitter toward said optical switch along a further
path; and causing infrared radiation that arrives at said beam
splitter along said further path to thereafter travel away from
said beam splitter along said first portion of said optical
path.
10. An apparatus comprising an optical rangefinder that includes:
means defining an optical aperture; generator means for emitting
optical radiation; detector means for detecting optical radiation;
optical means for directing optical radiation from said generator
means to and through said aperture, and for directing reflected
energy of the optical radiation that is received back through said
aperture to said detector means, said optical means including
optical switch means having a first operational mode for routing
optical radiation from said generator means in a manner that
facilitates said directing of the optical radiation to and through
said optical aperture, and having a said second operational mode
for routing the reflected energy in a manner that facilitates said
directing of the reflected energy to said detector means; and
control means for controlling said generator means and said optical
switch means, said control means being responsive to said detector
means.
11. An apparatus according to claim 10, wherein said generator
means emits infrared radiation, and said detector means is
responsive to infrared radiation.
12. An apparatus according to claim 11, including means defining a
further aperture, said optical means directing visible radiation
received through said optical aperture along an optical path
extending to and through said further aperture.
13. An apparatus according to claim 12, wherein said optical means
includes beam splitter means disposed along said optical path
between first and second portions thereof; and wherein said beam
splitter means causes visible radiation arriving at said beam
splitter means from said optical aperture along said first portion
of said optical path to thereafter travel away from said beam
splitter means toward said further aperture along said second
portion of said optical path, causes infrared radiation arriving at
said beam splitter means along said first portion of said optical
path to thereafter travel away from said beam splitter means toward
said optical switch means along a further path, and causes infrared
radiation that arrives at said beam splitter means along said
further path to thereafter travel away from said beam splitter
means along said first portion of said optical path.
Description
[0001] This application claims the priority under 35 U.S.C.
.sctn.119 of provisional application No. 60/552,262 filed Mar. 10,
2004.
TECHNICAL FIELD OF THE INVENTION
[0002] This invention relates in general to techniques for aiming
weapons and, more particularly, to a weapon sight that can be
mounted on a weapon in order to assist with accurate aiming of the
weapon.
BACKGROUND OF THE INVENTION
[0003] Over the years, various techniques and devices have been
developed to help a person accurately aim a weapon such as a rifle.
One common approach is to mount a sight or scope on the weapon. A
person then uses the sight or scope to view an intended target in
association with a reticle, often with a degree of magnification.
Although existing weapon sights have been generally adequate for
their intended purposes, they have not been satisfactory in all
respects.
[0004] For example, it is very common for a solder to carry both a
rifle and a grenade launcher. The grenade launcher is detachably
coupled to the rifle, thereby effectively giving the soldier an
integrated weapon that can selectively deliver either of two
different types of munition. Typically, however, one sight is
provided for the rifle, and a physically separate sight is provided
for the grenade launcher. Further, these sights are configured so
that, at any given point in time, each sight can be used with only
a single type of munition. Moreover, the sight for the grenade
launcher is often mounted near the outer end of the rifle barrel,
thereby adding weight at a location spaced from the center-of-mass
of the overall weapon, and thus necessitating greater effort by a
soldier to swing the weapon to bear and then hold it on a
target.
[0005] A further consideration is that, where a soldier has a
grenade launcher mounted on a rifle, the soldier may be able to
selectively use different bullets of the proper caliber in the
rifle, or selectively use different types of grenades with the
grenade launcher. Moreover, it may be a simple matter for the
soldier to detach one type of grenade launcher from the rifle and
quickly attach a different type of grenade launcher. Existing
weapon sights provide little or no capability for quick and
accurate adjustment in the field to accommodate changes in munition
type and/or weapon type.
[0006] To the extent some existing weapon sights include electronic
circuitry that can provide a user with electronically calculated
information to assist in aiming the weapon, this information is
often not visible within the same field of view in which the target
is visible, and is often presented digitally in the form of
alphanumeric characters that are sometimes difficult to understand
and use. A further consideration relates to the extent to which
calculations based on a particular target ranging event remains
available for use by a user.
[0007] Still another consideration is that some weapon sights
include a laser rangefinder. However, in order to achieve a high
transmission efficiency for both the outgoing pulse and the
reflected energy, these laser rangefinders typically have a first
aperture for the outgoing pulse, and a separate second aperture for
the reflected energy. Other existing laser rangefinders use a
single aperture, but in association with a beam splitter having a
transmissivity of approximately 50% for the laser wavelengths
involved, resulting in approximately a 50% loss for the energy of
the transmitted pulse, and another 50% loss for the reflected
energy. This is undesirable, because it reduces the maximum range
that can be measured by the rangefinder. Moreover, this is highly
inefficient, which makes it undesirable for a battery-operated
weapon sight, where any waste of energy reduces the amount of time
that the weapon sight can operate before the battery becomes
discharged.
SUMMARY OF THE INVENTION
[0008] One form of the invention relates to an optical rangefinder
having an optical aperture, an optical radiation generator, an
optical radiation detector, and an optical switch, and involves:
directing optical radiation from the generator to and through the
optical aperture, including operating the optical switch in a first
operational mode in which the optical switch routes optical
radiation from the generator in a manner that facilitates the
directing of the optical radiation to and through the optical
aperture; and directing reflected energy of the optical radiation
that is received back through the optical aperture to the detector,
including operating the optical switch in a second operational mode
in which the optical switch routes the reflected energy in a manner
that facilitates the directing of the reflected energy to the
detector.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] A better understanding of the present invention will be
realized form the detailed description that follows, taken in
conjunction with the accompanying drawings, in which:
[0010] FIG. 1 is a diagrammatic perspective rear view of an
apparatus in the form of a weapon sight that embodies aspects of
the present invention;
[0011] FIG. 2 is a diagrammatic perspective front view of the
weapon sight of FIG. 1;
[0012] FIG. 3 is a diagrammatic rear view of a support and a rear
reticle that are components of a direct view grenade sight in the
weapon sight of FIG. 1;
[0013] FIG. 4 is a diagrammatic fragmentary rear view, partly in
section, of a portion of the weapon sight, and shows a front
reticle of the direct view grenade sight;
[0014] FIG. 5 is a diagrammatic fragmentary rear view similar to
FIG. 4, except that the rear reticle is in an upright operational
position rather than a horizontal retracted position;
[0015] FIG. 6 is a diagrammatic view showing, in an enlarged scale,
an analog display that is part of the weapon sight of FIG. 1;
[0016] FIG. 7 is a diagrammatic view of the optics for a primary
optical sight in the weapon sight of FIG. 1;
[0017] FIG. 8 is a block diagram of the weapon sight, and
diagrammatically shows a number of components that are internal to
the weapon sight;
[0018] FIG. 9 is a diagrammatic view showing an example of an image
that the eye of a user would see when looking through the eyepiece
lens of the primary optical sight.
[0019] FIG. 10 is a diagrammatic view similar to FIG. 9, but
showing the image that would be seen when the weapon sight is set
for a higher level of magnification than shown in FIG. 9;
[0020] FIG. 11 is a diagrammatic view of a typical image that would
be displayed by an external display of the weapon sight of FIG.
1;
[0021] FIG. 12 is a diagrammatic side view of the weapon sight of
FIG. 1;
[0022] FIG. 13 is a diagrammatic view of the external display, and
depicts an example of an image that is presented by the external
display during a programming mode; and
[0023] FIG. 14 is a diagrammatic view of the external display, and
depicts a further example of an image presented by the external
display in the programming mode.
DETAILED DESCRIPTION
[0024] FIG. 1 is a diagrammatic perspective rear view of an
apparatus that is a weapon sight 10, and that embodies aspects of
the present invention. Although the disclosed weapon sight 10
happens to be a rifle sight, the present invention has aspects that
are not limited to rifle sights, but can be used in sights for
various different types of weapons. As discussed in more detail
later, the weapon sight 10 is capable of use with a rifle that can
fire at least two different types of munitions. One specific
example would be a military rifle having a grenade launcher
removably mounted on the barrel, such that a soldier can use the
rifle to fire either a munition with a low arc trajectory (such as
a bullet), or a munition with a high arc trajectory (such as a
grenade).
[0025] The sight 10 includes a rail mount 12 that can fixedly but
removably mount the sight 10 on the receiver or mounting rail of a
firearm. The sight 10 includes a housing 16. The position of the
housing 16 can be adjusted relative to the rail mount 12 in a
manner known in the art, in order to "zero" the sight 10 to the
weapon. In the disclosed embodiment, this type of adjustment is
made using thumbscrews, one of which is visible at 18.
[0026] The top of the housing 16 has a lengthwise groove 21. A
backup sight has two portions 22 and 23 that are fixedly mounted in
the groove 21, near opposite ends of the groove. The portion 22 is
a rear sight having a cylindrical peep hole, and the portion 23 is
a front sight in the form of a rounded tritium lit post.
[0027] Three manually operable rotary switches 26, 27 and 28 are
provided on one side of the housing 16. Four manually operable
momentary pushbutton switches 31-34 are provided on a rear surface
of the housing 16. The switch 31 is a circular TOGGLE switch, the
switch 32 is a triangular UP switch, the switch 33 is a triangular
DOWN switch, and the switch 34 is a circular SELECT switch. The
switches 26-28 and 31-34 are each configured so that they can be
easily operated by someone who is wearing arctic mittens. The use
of the switches 26-28 and 31-34 is discussed in more detail
later.
[0028] An optical lens 36 is mounted in an opening in the rear
surface of the housing 16, and is part of an eyepiece optics
section of a primary optical sight that extends through the housing
16, as discussed in more detail later. Adjacent the lens 36 is a
further sight in the form of a rearwardly facing external display
38. The display 38 is a known type of device, such as a liquid
crystal display (LCD), and can present graphics images or video
images generated by circuitry within the sight 10, in a manner
discussed in more detail later.
[0029] FIG. 2 is a diagrammatic perspective front view of the sight
10 of FIG. 1. A thumbscrew 51 is provided to manually tighten and
loosen the rail mount 12. A removable battery compartment cover 53
provides access to batteries that power the circuitry within the
sight 10.
[0030] An infrared (IR) illuminator 56 is provided in a front
surface of the housing 16, and serves as a form of IR flashlight
that can be used to illuminate a potential target with IR
radiation. A person who is using the sight 10 and who is wearing
night vision goggles will then have a better view of the potential
target.
[0031] An IR pointer 58 and a visible pointer 59 are each provided
in the front surface of the housing 16. The pointers 58 and 59 each
produce a thin beam of radiation that can be centered on a
potential target, in order to help accurately aim the weapon at the
target. The beam of the visible pointer 59 can be seen with the
naked eye by a person using the sight 10, but may possibly be
noticed by the potential target. In contrast, the IR pointer 58 has
an IR wavelength of about 950 nm. In order to see the beam of the
IR pointer 58, a person using the sight 10 should be wearing night
vision goggles. A potential target will not see the beam of the IR
pointer, unless the target also happens to be wearing night vision
goggles.
[0032] An optical lens 62 is mounted in an opening in the front
surface of the housing 16, and is part of the above-mentioned
optical sight that extends through the housing 16, and that will be
discussed in more detail later. A sunshade 63 projects outwardly
from the housing 16, above the lens 62.
[0033] A direct view grenade sight includes a front reticle 66 and
a rear reticle 68. The front reticle 66 includes a circular piece
of transparent material such as a hard carbon-coated polycarbonate,
and is mounted in a circular opening provided through a wall of the
housing 16. The front reticle 66 has thereon a reticle pattern that
is discussed later. The rear reticle 68 is a rectangular piece of
transparent material, such as a hard carbon-coated polycarbonate,
and has thereon a reticle pattern that is discussed later. The rear
reticle 68 is mounted on a cylindrical support 71, and the support
71 is pivotally supported on the housing 16. As indicated
diagrammatically by a broken-line arrow 72, the rear reticle 68 can
be pivoted between a vertical operational position shown in FIG. 2,
and a horizontal retracted position. The rear reticle 68 is not
directly visible in FIG. 1, because it is in its horizontal
retracted position in FIG. 1. The front and rear reticles 66 and 68
are each backlit in a known manner, to facilitate visibility.
[0034] FIG. 3 is a diagrammatic rear view of the support 71 and the
rear reticle 68, with the reticle 68 in its upright operational
position. FIG. 3 shows in more detail the reticle pattern 76. The
reticle pattern 76 provides elevation ranging out to 400 meters,
for elevations that exceed 42.degree.. The reticle pattern 76
curves upwardly and leftwardly, in order to provide
spindrift-corrected elevation ranging with better than 20 meters
resolution. As is known in the art, spindrift is the tendency of a
projectile to drift laterally as a result of aerodynamics that
relate to the fact it is spinning as it travels through the air.
Spindrift is more acute for larger projectiles such as grenades
that have long flight times, as opposed to smaller projectiles with
shorter flight times, such as bullets.
[0035] FIG. 4 is a diagrammatic fragmentary rear view, partly in
section, of a portion of the sight 10 that includes the front
reticle 66 of the direct view grenade sight. In FIG. 4, the support
71 for the rear reticle 68 is in its horizontal retracted position,
and is thus not visible in FIG. 4. The reticle pattern of the front
reticle 66 includes perpendicular crosshairs 86 and 87, and a
correction grid 88 that is centered on the crosshairs 86 and 87. A
shooter can use the correction grid 88 to manually effect azimuth
and/or elevational compensation for factors such as a crosswind, or
a target that is at a higher or lower elevation than the shooter.
To the right of the reticle 66 is an analog display 91. The display
91 is controlled by electronic circuitry that is within the housing
16, and that is explained in more detail later.
[0036] FIG. 5 is a diagrammatic fragmentary rear view similar to
FIG. 4, except that the rear reticle 86 is in its upright
operational position, rather than its horizontal retracted
position. A person using the direct view grenade sight views a
potential target by looking through the rear and front reticles 68
and 66. The person centers the intersection of the crosshairs 86
and 87 on the potential target, and also aligns the intersection of
these crosshairs with a point along the curve 76 that corresponds
to the range to the target. If there are factors that necessitate
an azimuth correction or elevation correction, the person selects a
different set of crosshairs within the grid 88, and aims the weapon
using the intersection of these alternative crosshairs, instead of
the intersection of the main crosshairs 86 and 87.
[0037] When a person is looking through the aligned front and rear
reticles 66 and 68, the analog display 91 is within a peripheral
portion of the person's field of view. The analog display 91
provides additional information that helps in aiming the weapon. In
this regard, FIG. 6 is a diagrammatic view that shows the analog
display 91 in a significantly enlarged scale. The analog display 91
includes a vertical column of five light emitting diodes (LEDs)
101-105. The LEDs 101-105 are controlled by electronic circuitry
within the weapon sight 10. In the disclosed embodiment, the LEDs
101-105 have different colors. In particular, the center LED 103 is
green, the two outer LEDs 101 and 105 are each red, and the two
remaining LEDs 102 and 104 are each yellow. Adjacent the center LED
103 is a hash mark 108, the purpose of which is to clearly
designate which LED is the center LED 103.
[0038] When either of the red outer LEDs 101 or 105 is lit, it
means that the weapon is currently aimed in a manner so that the
elevation is long or short by an amount that will cause a grenade
to miss the target by at least 50 meters. As the weapon is adjusted
and the elevation approaches more closely to the target, one of the
yellow LEDs 102 or 104 will also be turned on. When a red LED and
the adjacent yellow LED are both on, it means that the range is
between 20 to 50 meters short or long of the target. As the person
continues to adjust the orientation of the weapon, the red LED will
turn off, leaving only the yellow LED on. This means that the range
is currently between 10 and 20 meters short or long of the
target.
[0039] As manual adjustment of the weapon continues, the green
center LED 103 will eventually be turned on. When the green LED 103
and one of the yellow LEDs 102 or 104 is turned on, it means that
the current range is within 10 meters of the target. As adjustment
continues, the yellow LED will be turned off, so that only the
green center LED 103 remains on. This indicates that the current
elevation is such that the range is now within 5 meters of the
target.
[0040] At any point during this aiming process, if the side-to-side
cant or offset of the weapon is such that the grenade would land to
the left or right of the target by a distance greater than a
selected threshold distance, then each LED that is lit will blink.
In contrast, when there is no side-to-side cant or offset, each LED
will glow continuously when it is lit. The direct view grenade
sight with the reticles 66 and 68, and the analog display 91, are
each used to aim the weapon with respect to the secondary munition,
such as a grenade, and are not used to aim the weapon with respect
to the primary munition.
[0041] FIG. 7 is a diagrammatic view of the optics for the primary
optical sight of the weapon sight 10 of FIG. 1. In this regard,
FIG. 7 shows the lenses 36 and 62 that have already been mentioned
above. A potential target at a remote location is shown
diagrammatically at 114. A broken line 116 represents a path of
travel through the sight 10 of visible radiation that embodies an
optical image of the target 114. This radiation from the target 114
travels along the path 116 to an eye 118 of a user.
[0042] In more detail, after entering the sight 10, the radiation
passes through the previously-mentioned lens 62. In the disclosed
embodiment, the lens 62 is actually a lens doublet, and defines an
optical aperture for the sight 10. After passing thorough the lens
62, radiation passes successively through two lenses 121 and 122.
The lenses 121 and 122 are mounted on a support 123, and the
support 123 can be reciprocally pivoted though an angle of
90.degree.. If the support 123 is pivoted 90.degree.
counterclockwise from the position shown in FIG. 7, the lenses 121
and 122 will each move away from the path of travel 116 of the
radiation, to the respective positions shown in broken lines. The
pivotal position of the support 123 determines the optical
magnification of the sight 10. In particular, the optical
magnification is 1.times. when the lenses 121 and 122 are disposed
in the path of travel 116, whereas the magnification is 4.times.
when the lenses 121 and 122 are not in the path of travel 116.
[0043] The sight 10 also has a prism assembly that includes three
prisms 136-138. The prisms 136-138 each have one or two surfaces
that are at least partly covered by a reflective coating. For
clarity, these coatings are not separately shown in FIG. 7. The
coatings on the surfaces are each a type of coating that is well
known in the art, but these coatings are not all identical. Except
as otherwise discussed below, the coatings each reflect all of the
radiation of interest that is traveling through the sight 10. After
radiation has passed through the three prisms 136-138, it passes
successively through a lens assembly 148 and the lens 36, and then
travels to the eye 118 of the user.
[0044] Referring back to the surface 141 on the prism 136, the
coating on this surface is completely reflective to visible
radiation and to shorter wavelengths of IR radiation (such as a
wavelength of 950 nm), but is transmissive to longer wavelengths of
IR radiation (such as a wavelength of 1550 nm). This coating thus
serves as a form of beam splitter. In the disclosed embodiment,
this coating is a thin-film filter of a type well known in the art,
and has a plurality of layers of different types of material that
collectively give it the desired optical characteristic. The sight
10 has a section 156 that is shown diagrammatically in FIG. 7. The
section 156 includes an infrared laser rangefinder, and is
discussed in more detail later.
[0045] Turning now to the surface 142 on the prism 138, most of
this surface is covered by a reflective coating, but a portion of
the surface is not coated. The coated portion of the surface is
completely reflective to all radiation, including both visible and
infrared radiation. The sight 10 includes a section 157 that can
generate visible radiation, and this visible radiation passes
through the uncoated portion of the surface 142, and travels to the
eye 118 of the user. The section 157 is discussed in more detail
later. The primary optical sight of FIG. 7 is used to aim the
weapon for purposes of rangefinding and shooting the primary
munition, such as a bullet, but is not used to aim the weapon for
the purpose of shooting the secondary munition.
[0046] FIG. 8 is a block diagram of the weapon sight 10. Some of
the components shown in FIG. 8 have already been discussed above,
and are therefore not discussed again in association with FIG. 8.
In this regard, a block 166 in FIG. 8 collectively represents the
various user controls that can be manually operated by a user,
including the three rotary switches 26-28 (FIG. 1), and the three
pushbutton switches 31-34 (FIG. 1). With reference to the optical
arrangement shown in FIG. 7, it should be noted that, for clarity,
the prisms and some of the lenses have been omitted from FIG. 8.
FIG. 8 does show the eyepiece lens 36 at one end of the sight, and
the objective lens 62 at the other end of the sight.
[0047] As discussed above in association with FIG. 7, the surface
141 on the prism 136 has a coating that serves as a beam splitter,
and is associated with a section 156 of the sight that includes a
laser rangefinder. In FIG. 8, the coating that serves as a beam
splitter is shown diagrammatically at 171. As discussed above, this
coating is a thin-film filter of a known type, and differentiates
between two different groups of wavelengths. The wavelengths of one
group include visible radiation and shorter wavelengths of IR
radiation (such as a wavelength of 950 nm). The wavelengths in this
group can travel along the path 116 from the target 114 to the eye
118 of the user. The wavelengths of the other group include longer
wavelengths of IR radiation (such as 1550 nm). Wavelengths in this
group can travel from the section 156 of the sight to the beam
splitter 171 and then along the path 116 to the target 114.
Similarly, these wavelengths can also travel from the target 114
along the path 116 to the beam splitter 171, and then to the
section 156.
[0048] As discussed earlier, the section 156 implements an IR laser
rangefinder. In more detail, the section 156 includes a laser diode
176 of a known type. The laser diode 176 can emit a short pulse of
highly-focused IR radiation at a wavelength of 1550 nm. The section
156 also includes an IR detector 177 that is responsive to
radiation at the wavelength of 1550 nm. The section 156 further
includes a fast optical switch 178. The optical switch 178 is a
device implemented with technology known in the art, such as that
disclosed in PCT Publication No. WO 01/40849, published by the
World Intellectual Property Organization of Geneva Switzerland on
Jun. 7, 2001. The switch 178 provides a form of time division
multiplexing between the laser diode 176 and the detector 177.
[0049] More specifically, when the optical switch 178 is set to a
first operational mode in which it selects the laser diode 176, the
laser diode 176 can emit an IR pulse that travels through the
switch 176 to the beam splitter 171, and then travels along the
path 116 to the target 114. After this pulse has been transmitted,
the optical switch 178 is shifted to a second operational mode, in
which it selects the detector 177. A portion of the energy of the
transmitted IR pulse will be reflected by the target 114, and will
travel back along the path 116 to the beam splitter 171, then to
the switch 178, and then to the detector 177, where the pulse of
reflected energy is detected. The time lapse between the emission
of the IR pulse by the laser diode 176 and the detection of the
reflected energy by the detector 177 is proportional to the
distance traveled by the IR radiation, and is thus proportional to
the distance between the sight 10 and the target 114. The use of
the optical switch 178 thus achieves a laser rangefinder that uses
only a single aperture, but that matches the performance of dual
aperture laser rangefinders. The laser diode and the detector gain
full advantage of the transmission capabilities of the common
optics, without introducing power sharing losses.
[0050] As discussed above in association with FIG. 7, the surface
142 on the prism 138 is partially covered with a reflective
coating, and is associated with a section 157 of the sight 10. In
FIG. 8, an interface is shown diagrammatically at 181, and
corresponds functionally to the coating that partially covers the
surface 142. As mentioned above, the portion of the surface that is
coated is completely reflective to visible radiation and IR
radiation. Consequently, all visible and IR radiation that is
traveling along the path 116 and that reaches the coated portion of
the surface will be reflected, and will continue traveling along
the path 116 to the eye 118 of a user.
[0051] As discussed earlier, the section 157 can generate a visible
image. This visible image is generated using an internal display
183. The display 183 is a known type of device, such as a liquid
crystal display (LCD). In the disclosed embodiment, the visible
image information generated by the display 183 includes
alphanumeric characters, as discussed later. This image information
travels from the internal display 183 to the interface 181, and
then along the path 116 to the eye 118 of a user. More
specifically, and as discussed above in association with FIG. 7,
this visible image information passes through the uncoated portion
of the surface 142, and then travels through the lens assembly 148
and the lens 36 to the eye 118 of a user.
[0052] As shown diagrammatically at 186 in FIG. 8, a reticle is
superimposed on the visible radiation that is traveling along the
path 116 to the eye 118 of a user. This is one of two reticles
provided by the sight 10, one of which is associated with the
1.times. magnification provided when the lenses 121 and 122 are
disposed in the path of radiation travel 116, and the other of
which is associated with the 4.times. magnification provided when
the lenses 121 and 122 are spaced from the path of travel 116. As
evident from FIG. 8, the reticle 186 used in association with
1.times. magnification is an aiming point in the form of a dot.
[0053] As shown diagrammatically in FIG. 8, the weapon sight 10
includes a sensor section 201 that has several sensors 203, 206 and
208. The sensor 203 is a light sensor of a known type, and can
detect the degree of ambient illumination that is present
externally of the weapon sight 10. The sensor 206 represents one or
more sensors that can determine the orientation of the weapon sight
10, and thus the orientation of a weapon attached to the weapon
sight 10. There are a variety of commercially-available electronic
sensors that can detect orientation, including tilt sensors, and
sensors that effectively serve as an electronic compass.
[0054] The sensor 208 is an acceleration sensor, and is capable of
detecting the distinct mechanical shock that occurs when a weapon
is fired. In the disclosed embodiment, the acceleration sensor 208
is implemented with a commercially-available component.
[0055] The weapon sight 10 includes an electronic control circuit
216, and the control circuit 216 includes a processor 217 of a
known type. The control circuit 216 also includes a memory 221. In
FIG. 8, the memory 221 is a diagrammatic representation of two or
more types of memory, including read only memory (ROM), volatile
random access memory (RAM), and non-volatile random access memory
(such as flash RAM). The memory 221 stores a program 222 that is
executed by the processor 217, and also stores data 223 that is
utilized by the program 222. The control circuit 216 is responsive
to the IR detector 177, the sensors 203, 206 and 208 in the sensor
section 201, and the user controls 166, including the rotary
switches 26-28 and the pushbutton switches 31-34 (FIG. 1). The
control circuit 216 is operatively coupled to and controls the
analog display 91, the internal display 183, the IR laser diode
176, the fast optical switch 178, the external display 38, the IR
illuminator 56, the IR pointer 58, and the visible pointer 59. The
sight 10 includes a replaceable battery 231, and this battery
provides the operating power for all of the electronic components
within the weapon sight 10.
[0056] FIG. 9 is a diagrammatic view representing an example of the
image that the eye 118 of a user would see when looking through the
eyepiece lens 36 of the primary optical sight. A horizontal line
301 extends across the lower portion of this image. The portion of
the image above the line 301 corresponds generally to the portion
of the surface 142 (FIG. 7) that has a reflective coating, and the
portion of the image below the line 301 corresponds generally to
the portion of the surface 142 that is not coated. Thus, the
portion of the image above the line 301 includes an image of the
target 114, and includes the reticle 186. FIG. 9 assumes that the
pivotal support 123 is in the position shown in FIG. 7, in which
the lenses 121 and 122 are disposed in the path of radiation travel
116, and thus provide 1.times. magnification. As discussed above,
the reticle 186 used with 1.times. magnification is simply a dot in
the center of the overall image.
[0057] The portion of the image below the line 301 consists solely
of alphanumeric information produced by the internal display 183
(FIG. 8). This alphanumeric information includes a low battery
indicator LOWBAT 306, and this low battery indictor is displayed
when the battery 231 (FIG. 7) is nearing a discharged state. A
target range indicator 307 shows a current range to the target 114.
This is normally a range that has been determined automatically
using the laser rangefinder in the section 156 (FIG. 8), but can
alternatively be set manually, as discussed later. The information
at 308 is an indication of the current secondary munition on the
weapon, such as a selected grenade type. The information at 309 is
an indication of the current effective range of the secondary
munition, and is dependent on factors such as the current
orientation of the weapon and the sight 10. As a user changes the
orientation of the weapon and the sight 10, the electronic control
circuit 216 (FIG. 8) will repeatedly recalculate the effective
range of the secondary munition. Thus, the information displayed at
309 will change continuously while the weapon and the sight 10
being moved.
[0058] The information at 310 is an indication of the target
elevation, or in other words the angle formed with respect to a
horizontal reference by a straight line extending from the sight 10
to the target 114. The information displayed at 311 is an
identification of the current primary munition, such as a
particular type of bullet. The information displayed at 312 is the
current effective range of the primary munition. This range for the
primary munition is similar to the range information displayed at
309 for the secondary munition. It is continuously updated by the
control circuit 216 in response to changes in the orientation of
the weapon and the sight 10.
[0059] FIG. 10 is a diagrammatic view similar to FIG. 9, but
showing the image that would be seen by an eye 118 when the sight
10 is set for a magnification of 4.times. rather than 1.times.. As
discussed earlier, the magnification is changed from 1.times. to
4.times. by pivoting the support 123 90.degree. in a
counterclockwise direction from the position shown in FIG. 7. FIG.
10 is generally similar to FIG. 9, with two exceptions. First, the
target 114 is significantly larger within the image, because the
magnification is set at 4.times. rather than 1.times.. Second, the
reticle 186 has been replaced with a different reticle 186A. The
reticle 186A includes the dot or aiming point 186, and also several
stadia lines of a known type that facilitate ranging.
[0060] The reticles 186 and 186A are implemented in the following
manner. The reticles are each generated at the surface 142 of the
prism 138, because that surface lies at the focal plane of the
eyepiece lens 36 in the disclosed embodiment. In particular, the
coated portion of the surface 142 has the reticle pattern 186A
etched completely through the reflective coating, including the dot
186 and also the stadia lines. Under control of the control circuit
216, the internal display 183 is capable of causing just the dot
186 to be illuminated (as shown in FIG. 9), or of causing both the
dot and the stadia lines to be illuminated (as shown in FIG. 10).
Where only the dot 186 is being illuminated (as in FIG. 9) the
stadia lines may actually be faintly visible, but they have been
omitted FIG. 9 for clarity, because FIG. 9 represents a situation
where the dot 186 is illuminated and the stadia lines are not. In
the disclosed embodiment, the internal display 183 illuminates the
dot and/or the stadia lines using a distinctive color such as
red.
[0061] Instead of using the internal display 183 to illuminate the
reticle, it would alternatively be possible for the sight 10 to
have two light emitting diodes (LEDs) in the region of the surface
142, one of which was focused on the dot 186, and the other of
which was diffused to illuminate all the stadia lines. The control
circuit 216 could then selectively actuate one or both of the
LEDs.
[0062] FIG. 11 is a diagrammatic view of a typical image that would
be displayed by the external display 38 (FIG. 1) of the sight 10.
The external display 38 is used to aim the weapon for the purpose
of shooting the secondary munition, such as a grenade, but is not
used to aim the weapon for the purpose of shooting the primary
munition. All of the information presented by the display 38 is
generated electronically. This is in contrast to the images shown
in FIGS. 9 and 10, where a portion of the information is an actual
optical view of a remote scene, such as the target 114. In the
image of FIG. 11, there is a fixed reticle that includes a center
crosshair and nested concentric circles with range labels of "5",
"20" and "50" meters. The target is represented by a target symbol
in the form of a dot 336. In this regard, the dot 336 corresponds
to the target 114 shown in prior figures, but is given a separate
reference numeral in FIG. 11, because it is an
electronically-generated representation of the target 114, as
discussed below.
[0063] The periphery of the image in FIG. 11 includes some
alphanumeric information. This alphanumeric information includes a
low battery indicator 339 that is equivalent to the indicator 306
in FIG. 9, a target range indicator 341 that is equivalent to the
indicator 307, and a secondary munition type indicator 342 that is
equivalent to the indicator 308. In addition, the alphanumeric
information at 343 indicates the angle of elevation of the weapon
that is needed in order for the secondary munition to hit the
target 336.
[0064] As the weapon and the attached sight 10 are moved, the
electronically-generated target symbol 336 will move within the
image. Thus, in order to aim the weapon, the user will manually
move the weapon and the attached sight so that the target symbol
336 moves toward the crosshairs 331, as indicated diagrammatically
at 348. When the target symbol 336 is aligned with the crosshairs
331, the weapon is positioned so that the grenade or other
secondary munition should hit the target.
[0065] FIG. 12 is a diagrammatic side view of the weapon sight 10.
As shown in FIG. 12, the rotary switch 28 has two positions
"1.times." and "4.times.", and selects between the two levels of
magnification for the main optical sight. In this regard, the
switch 28 is physically coupled to the pivotal support 123 shown in
FIG. 7. Manual pivoting the switch 28 through 90.degree. between
its 1.times. and 4.times. positions effects a corresponding
90.degree. pivotal movement of the support 123, in order to move
the lenses 121 and 122 into or out of the path of travel 116 and
thus change the magnification. In addition, the rotary switch 28 is
electrically coupled to the electronic control circuit 216 (FIG.
8), so that the control circuit 216 knows the current setting of
the switch 28.
[0066] The rotary switch 27 is an illumination switch, and controls
the degree of illumination of several different components of the
sight 10. In particular, the illumination switch 27 controls the
brightness of the external display 38, the brightness of the LEDs
101-105 of the analog display 91, the brightness of the internal
display 183, and the brightness of the backlighting for the various
reticles 66, 68, 186 and 186A.
[0067] In more detail, the switch 27 has three positions "N1", "N2"
and "N3" that implements three different levels of brightness
suitable for use by a user who is wearing night vision goggles. In
a similar manner, the switch 27 includes four positions "1", "2",
"3" and "4" that implement four different levels of brightness
suitable for unassisted viewing, or in other words viewing by a
user who is not wearing night vision goggles. The switch 27 has a
further position "A", where the control circuit 201 provides
automatic brightness control at levels suitable for unassisted
viewing, the level of illumination being a function of the ambient
illumination. In this regard, the light sensor 203 (FIG. 8)
determines the degree of ambient illumination around the weapon
sight 10, and the control circuit 216 uses this information to set
the level of brightness for the various displays and reticles. As
the degree of ambient illumination progressively increases, the
degree of illumination of the displays and reticles is also
progressively increased.
[0068] The rotary switch 27 includes a visible pointer position
"VP", in which the control circuit 216 turns on the visible pointer
59 (FIG. 8). The switch 27 also has an IR pointer position "IP", in
which the IR pointer 58 (FIG. 8) is turned on. Further, the switch
27 has an IR illumination position "IL", in which the IR
illuminator 56 (FIG. 8) is turned on. The switch 27 also has an
"OFF" position, in which the illumination of all displays and
reticles is off, and in which the IR illuminator 56 and the
pointers 58-59 are all off.
[0069] As evident from FIG. 12, the rotary switch 26 has three
positions, including an "OFF" position, a combat mode position "C",
and a programming mode position "P". When the switch is in the
programming mode position P, a user in the field can manually set
certain parameters, including identification of the types of
primary and secondary munitions that the weapon sight 10 is being
used with. In this regard, for example, it is possible for a
soldier to easily detach one type of grenade launcher from his
rifle and then attach a different type of grenade launcher, and the
weapon sight 10 needs to be notified of this change if it is to
assist the soldier in aiming the replacement grenade launcher.
[0070] FIG. 13 is a diagrammatic view of the external display 38,
and depicts an example of an image that is presented by the display
38 in the programming mode. In particular, when the rotary switch
26 is set to the programming mode position P, the external display
38 switches from presentation of the type of image shown in FIG. 11
to presentation of the type of image shown in FIG. 13. In FIG. 13,
there are two columns of information. The left column relates to
the secondary weapon and munition type, and the right column
relates to the primary weapon and munition type.
[0071] In each column, the top entry identifies a type of weapon,
such as a type of rifle or a type of grenade launcher. Thus, for
example, the entry 401 indicates that the secondary weapon is a
particular type of rifle-mounted grenade launcher EGLM, and the
entry 402 indicates that the primary weapon is a particular type of
rifle SCAR-L(S). The middle entry in each column is an
identification of a particular type of munition, such as a type of
grenade or a type of bullet. Thus, for example, the entry 403
indicates that the secondary munition is a particular type of
grenade SMK, and the entry 406 indicates that the primary munition
is a particular type of bullet M855.
[0072] The bottom entry in each column specifies the boresight
distance, where the boresight distance is the distance at which the
trajectory arc of the corresponding munition would hit a target
disposed at the same elevation as the weapon that fires the
munition. Thus, the entry 405 is the boresight distance for the
secondary munition identified at 403, and the entry 406 is the
boresight distance for the primary munition identified at 404.
[0073] Upon entry to the programming mode, one of the parameters
401-406 will be selected. This selected parameter will be blinking,
in order to indicate that it is the selected parameter. With
reference to FIG. 1, the SELECT pushbutton 31 can be repeatedly
manually pressed in order to cycle successively through all six
parameters 401-406. As each parameter is selected and becomes the
active parameter, it blinks. When a given parameter is active and
selected, the setting of that parameter can be changed by pressing
the up or down pushbuttons 32 and 33 (FIG. 1), in order to cycle
forward or backward through a predefined list of available options
for that parameter. When a given parameter is changed, other
parameters will also sometimes automatically change, without
blinking. For example, each time the primary munition type 404 is
changed, the associated boresight distance 406 will also typically
be changed, so that it conforms to the selected type of primary
munition.
[0074] When the boresight distance 405 for the secondary munition
is selected, some additional information is presented on the
display 38. More specifically, FIG. 14 is a diagrammatic view that
is similar to FIG. 13, and that depicts a further example of an
image presented by the display 38 in the programming mode. The
image shown in FIG. 14 is generally similar to the image shown in
FIG. 13, except that the image of FIG. 14 shows the additional
information at 411 and 412.
[0075] The values at 411 and 412 are offset values for the
secondary munition. When the entry 405 has been selected to be the
active parameter using the SELECT pushbutton 31, the offset values
411 and 412 are automatically displayed. The TOGGLE pushbutton 34
can then be pressed to successively cycle through the parameters
405, 411 and 412. Each of these parameters can be individually
altered while it is selected, by pressing the UP pushbutton 32 or
DOWN pushbutton 33. If the TOGGLE pushbutton 34 is pressed and held
for at least 2 seconds, then the parameters 405, 411 and 412 will
each be reset to a respective default value. When the mode switch
26 is eventually switched away from the programming mode position
P, the display 38 will stop displaying the image of FIGS. 13 and
14, and the parameters 401-406 and 411-412 will each be maintained
at the value it had when the switch 26 was moved away from the
programming mode position P.
[0076] When the rotary switch 26 of FIG. 12 is set to the combat
position C, the weapon sight 10 operates in the following manner.
With reference to FIGS. 9 and 10, the user can place the aiming dot
of the main sight reticle 186 or 186A on a target 114, and press
the SELECT pushbutton 31. With reference to FIG. 8, the control
circuit 216 will respond by operating the laser diode 176 and the
optical switch 178 so as to transmit an IR laser pulse to the
target 114, and will then reverse the switch 178, so that reflected
energy from this pulse will be routed to the detector 177. At the
same time that the target 114 is ranged in this manner, the control
circuit 216 records the current status of the orientation sensors
206, so that the control circuit has a record of the orientation of
the weapon and sight 10 at the point in time when the target was
ranged. The control circuit 216 then determines the time lapse
between the outgoing and incoming pulses of energy, and calculates
the range to the target 114.
[0077] The control circuit 216 then calculates a ballistic solution
for each of the primary and secondary munitions. In other words,
using techniques known in the art, the control circuit 216
calculates an orientation that the weapon would need to have in
order for the primary munition to hit the target 114, and will
calculates a different orientation that the weapon would need to
have in order for the secondary munition to hit the same target.
Then, and taking into account the current orientation of the
weapon, appropriate information is presented on the various
electronic displays of the weapon sight 10. In particular, with
reference to FIG. 6, one or more of the LEDs 101-105 is lit in
either a continuous or blinking manner, as appropriate. In
addition, appropriate information is presented on the internal
display, for example at 307, 309, 310 and 312 in FIGS. 9 and 10.
Further, with reference to FIG. 11, the target symbol 336 is
displayed on the external display 38 at an appropriate location in
relation to the crosshairs 331.
[0078] This initial position of the target symbol 336 includes a
correction for spindrift, based on the measured range to the
target. The distance of the target symbol 336 from the crosshairs
331 is nonlinear. Thus, the position of the target symbol 336 will
typically not change much in response to movement of the weapon,
until the weapon's orientation is such that the secondary munition
would be delivered within 50 meters of the target. The target
symbol 336 never leaves the display. If the weapon is pointed too
far away from the target in any direction, the target symbol 336
simply comes to rest adjacent the top, the bottom or a side of the
display 38.
[0079] With reference to FIG. 8, and as discussed above, a manual
press of the SELECT pushbutton 31 causes the control circuit 216 to
use the laser rangefinder to determine the range to the target 114,
record the current state of the orientation sensors 206, and then
calculate an initial ballistic solution. Thereafter, the control
circuit 216 monitors the orientation sensors and repeatedly
recalculates the ballistic solution for each of the primary and
secondary munitions, using current information from the orientation
sensors, and using the previously-determined range to the target
114. Each time the ballistic solution is updated to reflect changes
from the orientation sensors 206, all of the displayed information
associated with the ballistic solution will also be updated. This
includes appropriate updates for the analog display 91, the
internal display 183, and the external display 38.
[0080] The control circuit 216 continues to repeatedly update the
ballistic solution, so long as there is ongoing user activity. For
example, operation of any of the switches 26-28 or 31-34 is
considered user activity, and firing of either the primary or
secondary weapon is considered user activity. In this regard, if
the user fires either the primary weapon or the secondary weapon,
the acceleration sensor 208 will detect the discharge, and notify
the control circuit 216. But if the control circuit 216 does not
detect any such user activity for a time interval of 40 seconds,
then the control circuit 216 will stop updating the ballistic
solution, will discard the target range and other information
associated with that ballistic solution, and will return to an idle
state in the combat mode.
[0081] It should be noted that the user can fire either or both of
the primary and secondary weapons one or more times, based on a
single laser ranging. In other words, the user is not required to
re-range the target after each discharge of either the primary or
secondary weapon. Moreover, the user can do only one ranging
operation in order to shoot either the primary munition or the
secondary munition, and does not need to do two separate ranging
operations that are respectively for the primary and secondary
munitions. Further, since the sight 10 is used for both the primary
and secondary munitions, the center of mass of the sight is near
the center of mass of the weapon, and thus a shooter can swing the
weapon to bear and hold it on a target with less effort. Due to the
use of certain common structure to support sights for both the
primary and secondary munitions, including the common housing,
optics and electronics, the weight and size of the sight 10 is les
than would be the case for two separate sights.
[0082] The sight 10 also includes sights that have analog
indicators within their field-of-view, such as the analog display
91 for the direct view grenade sight having the reticles 66 and 68.
This lets a shooter use his peripheral vision to determine when the
weapon is on target, while simultaneously keeping his fovea fixed
on the target itself. The use of analog indicators avoids the need
to match up a current digital value against a displayed or
remembered target digital value.
[0083] While a given ballistic solution is active and being
repeatedly updated, the pushbuttons UP and DOWN can be used to
manually adjust the range that is being used as a basis for
calculating the ballistic solution. In addition, the user can press
the TOGGLE pushbutton 34 in order to change the grenade type. Thus,
for example, if the user ranges a given target, shoots one type of
grenade, and then loads a different type of grenade on the grenade
launcher, the user does not need to re-range the target in order to
use the new grenade type. The user simply presses the TOGGLE
pushbutton 34 in order to cycle through the available types of
grenades to the new grenade type, and then the calculation of the
ballistic solution is immediately adjusted so as to accommodate the
new type of grenade. Changing the grenade type in this manner has
the effect of changing the pre-programmed grenade type parameter
shown as entry 403 in FIG. 13, without any need to enter the
programming mode.
[0084] When there is no active ballistic solution that is being
updated by the control circuit 216, or in other words when the
control circuit 216 is in an idle state while in the combat mode,
the user can optionally press the TOGGLE pushbutton 34 instead of
the SELECT pushbutton 31. As discussed above, pressing the SELECT
pushbutton 31 causes the control circuit 216 to use the laser
rangefinder to effect automatic ranging of a potential target. In
contrast, pressing the TOGGLE pushbutton 34 during the idle state
will cause the control circuit 216 to set the target range to a
default value of 200 meters, while recording the current status of
the orientation sensors 206 so that the control circuit knows the
orientation of the weapon and sight 10 at the time when the TOGGLE
pushbutton was pressed. The target is assumed to lie along the
line-of-aim of the sight 10 at the time that the TOGGLE pushbutton
34 is pressed. The UP and DOWN pushbuttons 32 and 33 can be used to
increase or decrease this default range, in a manner similar to
that discussed above. Selecting a default range by pressing the
TOGGLE pushbutton causes the control circuit 216 to exit its idle
state, and to begin repeatedly calculating a ballistic solution in
the same basic manner discussed earlier.
[0085] While a ballistic solution is active, or in other words
while the control circuit 216 is repeatedly updating the ballistic
solution, the SELECT pushbutton 31 can be pressed at any time, and
will cause the control circuit 216 to discard the current ballistic
solution, to immediately use the laser rangefinder to range the
target, and to then begin repeatedly calculating a ballistic
solution based on this new range. In contrast, pressing the SELECT
pushbutton 34 only sets the range to a default value if the control
circuit is in an idle state. If the SELECT pushbutton 34 is pressed
while a ballistic solution is active, it will cause the control
circuit to cycle through the available grenade types, as already
discussed above.
[0086] An advantage of the external display 38 is that, after a
target has been ranged, the user does not need to have a direct
view of the target in order to fire the secondary munition. For
example, a soldier standing behind a wall can stand up, range a
target using the main optical sight, duck down behind the wall, and
then accurately aim and fire the secondary munition using the
external display 38, while remaining out of view of the target.
[0087] Although one embodiment has been illustrated and described
in detail, it will be understood that various substitutions and
alterations are possible without departing from the spirit and
scope of the present invention, as defined by the following
claims.
* * * * *