Patent Application
20080186485
This invention relates to an optical sight having a reticle and, more particularly, to such an optical sight wherein the reticle pattern is defined by a quantum-dot light emitter.
Refractive or reflective optical sights are used in a wide variety of applications to obtain increased magnification of a scene. In one common application, an optical sight is affixed to the upper side of the barrel of a rifle-type weapon used by a soldier. The user sights through the optical sight to acquire a target and aim the weapon toward the target to increase the likelihood of hitting the target with a projectile fired from the weapon.
A reticle is typically provided in the optical path of the optical sight. The reticle normally has reference markings or other information that aids the user in aiming the optical sight and thence the weapon toward the intended target. The reference markings usually include a cross hair or similar marking to indicate the bore sight of the weapon. The reference markings may also include elevation, windage, and other reference markings that assist in aiming the weapon.
The reticle may be illuminated by an artificial light source within the optical sight. The reticle illumination ensures that the reticle will be visible in lighting conditions including normal daylight, low-light ambient conditions, and, particularly for infrared and other optical sights to be used at night, in near-darkness conditions. If ambient light is the sole reticle illumination, the illumination may be uneven and undependable.
The illumination of the reticle ideally satisfies a number of requirements. The illumination of the reticle must not interfere with the observation of the scene being viewed, yet the reticle must stand out against the scene. The reticle output desirably is adjustable and has low power consumption. The reticle illumination must be relatively uniform over the entire reticle so that the entire exit pupil is filled. Existing illumination approaches do not fully meet these requirements.
There is a need for an approach to ensure proper illumination of the reticle of an optical sight, so that the reticle always remains visible to the user peering through the optical sight. The present invention fulfills this need, and further provides related advantages.
The present approach provides an optical sight having an illuminated reticle. The reticle illumination is fully controllable over a wide range of reticle intensities. The reticle illumination utilizes a highly efficient illumination source whose output wavelength may be selected. The color of the reticle illumination may be selected according to the materials used in the construction of the reticle.
In accordance with the invention, an optical sight comprises an optical train defining an optical path and having at least one optical element. The optical train includes as an optical element a reticle including a reticle pattern defined by a quantum-dot light emitter that is excited by light of an excitation wavelength and emits light in a visible wavelength, and a light source producing an output light of the excitation wavelength positioned to direct the output light to be incident upon the quantum-dot light emitter. The light source is preferably a source of ultraviolet excitation light, and is most preferably an ultraviolet light emitting diode. The optical sight normally includes a housing that encloses the optical train.
The optical train typically has at least one optically powered lens in addition to the reticle. In a typical configuration, there is an objective and eyepiece. There is also optionally but preferably an image erector. The reticle is normally integrated with the image erector or is a freestanding element that lies between the image erector and the eyepiece.
A preferred form of the structure of the reticle includes a reticle substrate that is transparent to light of the excitation wavelength and also is transparent to visible light. A reticle relief pattern is formed into the reticle substrate, typically by etching or engraving. The quantum-dot light emitter material is received into the reticle relief pattern. The light source is desirably positioned at a periphery of the reticle substrate and oriented to direct the output light toward the reticle relief pattern and its quantum-dot light emitter material.
One of the features of the present approach is that there may be a second, independently illuminated reticle pattern. In this case, the reticle pattern overlies a first portion of the reticle. The reticle further includes a second reticle pattern overlying a second portion of the reticle and defined by a second quantum-dot light emitter that is excited by light of a second excitation wavelength and emits light in a second visible wavelength. A second light source produces a second output light of the second excitation wavelength positioned to direct the second output light to be incident upon the second quantum-dot light emitter. The second quantum-dot light emitter may be the same material as the quantum-dot light emitter, or a different material. The second light source may be the same as the light source, or different. The second excitation wavelength may be the same as the excitation wavelength, or different. The second visible wavelength may be the same as the visible wavelength, or different.
In a preferred embodiment, an optical sight comprises an optical train defining an optical path and having at least one optical element. The optical train comprises an optically powered objective, an optically powered eyepiece, and a reticle comprising a reticle pattern defined by a quantum-dot light emitter that is excited by ultraviolet light and emits visible light. The reticle is preferably a freestanding element lying between the objective and the eyepiece. An ultraviolet light source, such as an ultraviolet light emitting diode, is positioned to direct ultraviolet light to be incident upon the quantum-dot light emitter. A housing encloses the optical train. Other compatible features discussed herein may be used with this embodiment.
Most preferably, an optical sight comprises an optical train defining an optical path and having at least one optical element. The optical train comprises an optically powered objective, an image erector, an optically powered eyepiece, and a reticle. The reticle comprises a freestanding reticle substrate that is transparent to ultraviolet light and also is transparent to visible light. The reticle substrate is positioned on the optical path between the objective and the eyepiece. There is a reticle relief pattern formed into the reticle substrate, and a quantum-dot light emitter received into the reticle relief pattern. A cover sheet may be placed over the reticle substrate so as to encapsulate the reticle relief pattern between the reticle substrate and the cover sheet. The quantum-dot light emitter is excited by ultraviolet light and emits visible light. An ultraviolet light source is positioned to direct ultraviolet light to be incident upon the quantum-dot light emitter. A housing encloses the optical train. Other compatible features discussed herein may be used with this embodiment.
The present approach provides a reticle with a controllable light intensity. The use of quantum-dot technology produces a brighter reticle pattern for the power input. The power consumption of the reticle illumination source is small, an important consideration because the power source is preferably a battery. The lower the power consumption, the smaller the battery or the longer the battery life. Additionally, the color of the reticle pattern may be selected according to the composition and size of the nanodots that form the quantum-dot light-emitter material.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.
The objective 22 inverts the image from the scene as it travels along the optical path 30. To re-invert the image so that it may be comfortably viewed by the user without changing the magnification of the image, an optional optically unpowered image erector (also called an image inverter), illustrated as an erector prism 60, is positioned on the optical path 30 as an additional optical component between the objective 22 and the eyepiece 26. The erector prism 60 includes mirror surfaces provided as three prism elements, and the optical path 30 is reflected from reflecting surfaces of the erector prism 60 as it passes through the erector prism 60 as illustrated in
The reticle 24 includes a reticle pattern 70 of markings that provide a spatial reference for the user looking through the optical sight 20.
A quantum-dot light emitter 86 is received into the reticle relief pattern 82, and specifically into the individual recesses 84. The quantum-dot (also sometimes termed “nano-dot”) light emitter is a nanophosphor material formed. of a mass of particles of phosphorescent material having particle sizes much smaller than the wavelength of visible light. These quantum-dot light emitters are excited by light of an excitation wavelength and emit light of an output wavelength. For the present application, the output wavelength is in the visible wavelength range, so that the light output is visible to the unaided human eye 32 peering through the optical sight 20. The excitation wavelength is preferably a non-visible wavelength so that the excitation light is not visible to the unaided human eye. Most preferably, the excitation wavelength is in the ultraviolet wavelength range, typically less than about 450 nanometers wavelength, and most preferably about 395-400 nanometers wavelength.
Operable quantum-dot light emitters 86 include materials such as cadmium sulfide, cadmium telluride, silicon, and germanium, processed with a surfactant to a very small nano-dot size much smaller than the wavelength of visible light, and encapsulated. Quantum-dot light emitters are described, for example, in U.S. Pat. Nos. 7,078,276; 6,918,946; and 6,251,303, whose disclosures are incorporated by reference. Quantum-dot light emitters are available commercially from companies such as American Dye Source, Inc., Baie d'Urfe, Quebec Canada.
The selection of quantum-dot light emitters has several important advantages for forming a reticle pattern 70. Because the nano-dots (i.e., quantum-dots) are small, a large fraction of the atoms in each nano-dot are near the surface of the nano-dot, and accordingly can participate in the light-emission process. The energy-conversion efficiency of the quantum-dot light emitter 86 is therefore very high, reducing the power required to form the illuminated reticle pattern 70. The emitted light wavelength is determined by both the chemical composition of the nano-dots and also their size. Accordingly, the apparent color of the reticle pattern 70 in the visible wavelength range may be controlled according to the selected chemical composition and size of the nano-dots.
The reticle 24 further includes a light source 88 producing an output light 90 of the excitation wavelength, an ultraviolet wavelength in the preferred application. The light source 88 is positioned to direct the output light 90 to be incident upon the quantum-dot light emitter 86 as its excitation light. The light source 88 is preferably an ultraviolet-wavelength (UV) light-emitting diode (LED). Such UV LEDs are available commercially from companies such as Kingbright Corporation, City of Industry, Calif. In the embodiment illustrated in
The reticle substrate 80 is preferably covered with a cover sheet 96 to protect the quantum-dot light emitter 86 within the individual recesses 84 of the reticle-relief pattern 82. The reticle substrate 80 and the cover sheet 96 are made of a material, such as a glass, that is transparent to the output light 90 of the excitation wavelength and transparent to the visible-wavelength light 94.
As shown in
In another reticle illustrated in
The second excitation wavelength associated with the second reticle pattern 100 may be the same as the excitation wavelength associated with the reticle pattern 70, or it may be different. The second visible wavelength associated with the second reticle pattern 100 may be the same as the visible wavelength associated with the reticle pattern 70, or it may be different. A second light source 104 produces a second output light of the second excitation wavelength positioned to direct the second output light to be incident upon the second quantum-dot light emitter 102. The second light source 104 may be of the same type as the light source 88, or it may be different. However, preferably the second light source 104 is different from the light source 88, so that the two reticle patterns 70 and 100 may be independently illuminated. For this latter and most general case, a second power supply 106 is provided. Where the reticle pattern 70 and the second reticle pattern 100 are independently illuminated, for example at different excitation wavelengths, it is preferred that a light barrier 108, such as an opaque layer, be placed in the reticle substrate 80 between the reticle pattern 70 and the second reticle pattern 100. The second reticle pattern 100 otherwise functions in the same manner as the previously described reticle pattern 70, and the prior description is incorporated.
In yet another form, the reticle may be in an existing optical surface of the optical sight 20 lying in the optical path 30. For example, the reticle relief pattern 82 may be formed into the final reflecting surface 62, or the reticle substrate 80, having the reticle relief pattern 82 herein, may be placed into facing contact with the final reflecting surface 62. These forms of the reticle 24 are otherwise constructed and operated as described above, which description is incorporated here. There is then no need for the freestanding reticle 24 such as illustrated in
Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.
