Optics: measuring and testing – Fiducial instruments – Reticle lies outside viewing path
Patent
1980-11-19
1983-09-06
McGraw, Vincent P.
Optics: measuring and testing
Fiducial instruments
Reticle lies outside viewing path
G02B 2734, G02B 2736
Patent
active
044026056
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to optical sighting instruments and, in particular but not exclusively, to sighting instruments of the type described in Swedish Pat. No. 371,491 and U.S. Pat. No. 3,942,901, that is to say relatively simple, lightweight sighting instruments which are primarily intended for use together with light firearms, for example hunting rifles, and permit rapid and precise aiming of the firearm.
Optical sighting instruments of this type comprise a housing with a rear sight aperture and a lens device disposed in front of and spaced from the sight aperture, the lens device having a concave mirror surface which is provided to serve as a semi-transparent mirror and is turned to face towards the sight aperture, and a light source which is located in or adjacent the focal plane of the semi-transparent mirror surface of the lens device and is directed towards the concave face of the mirror surface such that the mirror surface produces, from the light from the light source, a virtual image which is perceived by the eye of the marksman as a sighting mark located far ahead of the lens device.
The object of the present invention is to facilitate adjustment of a sighting instrument of the above-disclosed type mounted on, for example, a rifle, without the need to alter the position of the entire instrument (a frame in the form of a housing with the lens system and light source) in relation to the barrel of the rifle.
It is known, in, for example, mirror optics with a lens mirror as projection element, to use a lens member for compensating refractive error in the occurrence of refractive forces.
A further object of the present invention is to utilize a portion of the refraction-compensating lens device as a means for making possible adjustment of the sighting instrument in relation to that object, for example a rifle barrel, on which the sighting instrument is mounted, without the need to alter the adjustment of the frame (housing) of the sighting instrument.
These objects have now been attained in that the sighting instrument according to the invention possesses the characteristic features disclosed in appended claim 1.
The invention will be described in greater detail below with reference to the accompanying drawing, in which
FIG. 1 illustrates, in schematic axial section, an optical sighting instrument according to the present invention, the sighting instrument comprising a lens system with a mirror and mutually movably disposed lenses in a housing which is intended to be mounted on a rifle barrel and comprises adjustment means and other requisite components such as light source and battery, and
FIG. 2 is schematic cross-section taken along the line III--III in FIG. 2.
In the lens system illustrated in FIG. 1, the concave, spherical mirror is disposed as an interface 1 between two connected lenses 2, 3, of which the one lens 2 is convavo-convex and the other lens 3 is concavo-planar, counting from the focal point F of the mirror 1. The convex face of the concavo-convex lens 2 and the concave face of the concavo-planar lens 3 abuts against each other with the mirror surface, consisting of a very thin layer, disposed as an interface between the two abutting lens surfaces. The lenses 2 and 3 are fixed in relation to each other by means of, for example, cement.
In the embodiment in FIG. 1, the plano-concave lens composed of the two lenses 2 and 3 forms a reducing lens which compensates for refractive error from the mirror. For redressing the image reduction so that the total lens system neither reduces nor magnifies, a plano-convex lens 4 is mounted in front of the lens unit 1, 2, 3, the magnifying power of the lens 4 counteracting the reduction caused by the combined lens 2, 3. Both of the lenses 2, 3 have been considerably polished for obviating spherical aberration and may consist of different materials for correcting chromatic aberrations. The lens 4 renders the system as a unit non-refractive and has a further important function.
A lens system with a lens mirror as projection element and two lens
REFERENCES:
patent: 3942901 (1976-03-01), Ekstrand
Aimpoint AB
McGraw Vincent P.
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