BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of a star tracker telescope with a gradient filter.
FIG. 2 is a diagram of an annular absorption filter.
FIG. 3 is a diagram of a triangular annular absorption filter.
FIG. 4 is a diagram of annular lens eyeglasses.
FIG. 5 is a diagram of reduced glare optics.
FIG. 6 is a diagram of an edge-attenuating lens.
FIG. 7 is a diagram of a patterned attenuating lens.
FIG. 8 is a diagram of a reduced glare camera.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
An embodiment of the invention is described with reference to the figures using reference designations as shown in the figures. Referring to FIG. 1, a star tracker telescope includes an optical sensor 10, a bandpass filter 12, an optical lens 14, a tubular shade 15, and an annular filter 16 for focusing received images upon a focal plane 17. The tubular shade 15 may include baffles 18. A bright off-axis star image 20 and a dim on-axis star image 22 provide optical images. The images pass through the annular filter 16, the focal plane 17, and optical lens 14 for activating the optical sensor 10 that provides electronic images of the bright off-axis star image 20 and the dim on-axis star image 22 for star tracking. The bright off-axis image 20 could be an image of the sun or a distal bright star. The dim on-axis star image 22 could be a dim remote star that is to be tracked.
The bright star off-axis image 20 passes through the tubular shade 15 along an attenuated bright star optical path 30 to the focal plane 14, lens 12, and sensor 10. The dim star image 22 passes along a dim star optical path 32 to the focal plane 14, lens 12, and sensor 10. The bright star off-axis image 20 also passes through the tubular shade 15 along an absorbed bright star optical path 34 where a portion of the bright star off-axis image is absorbed by the baffles 18. The bright star off-axis image 20 also passes through and is reflected by the tubular shade 15 along a reflected bright star optical path 36, to the focal plane 14, lens 12, and sensor 10.
The annular filter 16 includes a clear circular center portion 40 passing the dim on-axis star image 22 along the dim star optical path 32. The clear circular center portion 40 is completely transmissive and does not attenuate the signal strength of dim on-axis star image 22. The annular filter 16 further includes an attenuating annular portion 42 that attenuates the signal strength of the bright star off-axis image 20 along the attenuated bright star optical path 30, absorbed bright star optical path 34, and the reflected bright star optical path 36. Hence, an attenuating annular portion 42 of the annular filter 16 serves to attenuate the signal strength, but does not completely block the signal of the bright star off-axis image 20. Concurrently, the clear circular center portion 40 of the annular filter 16 serves to passes the dim on-axis star image 22. In this manner, the optical sensor 10 receives the dim on-axis star image 22 with maximum signal strength while receiving the bright star off-axis image 20 with reduced signal strength.
Referring to FIGS. 1 and 2, and more particularly to FIG. 2, the annular filter 16 is an annular absorption filter having the center clear portion 40 and the attenuating annular portion 42. The clear portion 40 is centered in the filter 16 and is defined by a radius R. The attenuating annular portion 42 is an outer portion defined by the circumference of the clear portion 40. The outer circumference of the filter 16 is defined by a diameter D. In one form of the invention, the attenuating annular portion 42 is defined by an identical attenuation profile that is equal and identical along any radial line extending from the center of the filter 16 to the circumference of the filter 16. More preferably, the attenuation profile of the attenuating annular portion 42 could be a uniform profile providing uniform attenuation along any radial line where the attenuation is equal at all points along all radial lines through the portion 42. The attenuation profile could be a gradient profile providing linearly increasing or decreasing amounts of attenuation at points along all radial lines through the portion 42.
Referring to FIGS. 1 through 3, and more particularly to FIG. 3, another preferred form of the invention is a triangular annular filter that is also an attenuating annular filter having a nonidentical amount of attenuation along the radial lines. In this form, the annular filter 16 has triangular density portions 48 that extend from an inner R diameter 44 to an outer circumference having an outer D diameter 46. The triangular portions 48 are a plurality of like triangular portions being isosceles triangles or wedges having tips at the inner R diameter 44 and a base running substantially in coincident alignment with the circumference having an outer D diameter of the filter 16. The triangular portions 48 can provide uniform or gradient attenuation. One particular case of uniform attenuation of the triangular portions 48 is reflection providing complete attenuation. In operation, the triangular portions 48 collectively function to attenuate the bright off-axis star images even when the triangular portions 48 are reflective. Uncoated clear optics is disposed in the center while the triangular portions 48 are disposed on the periphery of the filter 16. The triangular portions 48 could be easily made by reflective manufacturing masks producing silver mirrored surfaces.
In operation, the annular filters 16 may take various forms, such as with identical or nonidentical radial attenuation profiles, but at a minimum has an annular outer portion 42 for attenuating the off-axis images and a clear center portion for passing on-axis images. As a further enhancement, and at a minimum, the center portion could also have some attenuation filter so long as it is distinct from and less attenuation of the outer annular portion passing an attenuated remainder of the off-axis image. This dual attenuation feature is well suited for star tracking telescopes, but could also be applied to other optical apparatus, such as personal eyeglasses, binoculars, telescopes, and cameras.
Referring to FIG. 4, a pair of annular lenses are disposed in eyeglasses including an eyeglasses frame 50 supporting a right eyeglass lens 51a and a left eyeglass lens 51b. Each of the lenses 51a and 51g include an annular attenuating portion 52 for attenuating off-axis images and a clear center portion 54. The lenses 51a and 51b need not be circular. The lenses 51a and 52b may be for example, substantially rectangular in perimeter shape but have two distinct portions, the center portion 54 that may be, for example, oval in shape, and an outer portion 54 that may have an inner oval edge and an outer rectangular edge. The center portion 54 and annular attenuating portion 52 would have respective differences in the respective amounts of attenuation. In the preferred form, the inner portion is transparent and the outer portion is opaque.
Referring to FIG. 5, a human eyeball 56 functions to receive both an off-axis image 57 and on-axis image 59 for human perception using a retina focal surface 58 in the eyeball 56. The off-axis image 57 may be a glaring image and the on-axis image 59 may be a target image. An exemplar eyeglass lens 60 includes a clear circular center portion 61 through which passes the on-axis image along an on-axis target optical path 63, and includes a lens attenuating annular portion 64 through which passes the off-axis image along an off-axis glaring optical path 62. The lens 60 may be a prescription lens for providing both corrective vision and off-axis attenuation.
Referring to FIG. 6, an edge-attenuating lens has opposing side-edge attenuating portions 65 and a clear center portion 66 for attenuating left and right off-axis images while not attenuating top and bottom off-axis images. The edge-attenuating lens can have various other possible preferred forms, such as attenuating up and bottom off-axis images. The edge-attenuating lens is characterized as having a nonidentical attenuation profile along all radial lines extending from the center of the lens 64.
Referring to FIG. 7, a patterned attenuating lens 67 is configured with attenuating squares 68 that may be partially transmissive or completely reflective. The patterned attenuating lens 67 is also characterized as having a nonidentical attenuation profile along all radial lines extending from the center of the lens 67. Various shapes and prescriptions can be used in many possible variants so long as an outer portion of the lens 67 attenuates in some measure more than a center portion of the lens having a distinctly differing lesser amount of attenuation, such as transparency or significantly reduced attenuation. For example, the lens could be part of prescription sunglasses having a much more darker and opaque outer portion for increased off-axis attenuation as compared to less on-axis attenuation for defining variants of annular filtering. The eyeglasses 50 could be used by automobile drivers suffering from poor night vision. Unwanted off-axis images tend to glare and degrade perception of the on-axis images. The eyeglasses 50 would not attenuate on-axis red tail lights of cars in a driver's immediate front, but would attenuate off-axis periphery light from headlights of on-coming traffic for improve driving safety, yet remain enough of the off-axis image for visual periphery perception and safety.
Referring to FIG. 8, annular filtering can be applied to many other optical apparatus, such as a glare reduction camera 69 including an image sensor 70 which may be for example, a CCD electronic sensor or photographic film. The glare reduction camera 69 would include a camera annular filter 72 and a camera lens 74. The annular filter 72 would preferably include a clear portion 61 for passing by transparency an on-axis image 59 along the on-axis optical path 63 for photographing the on-axis image 59. The annular filter 72 would further include an outer annular portion 64 for attenuating along the off-axis optical path 62 the off-axis image 57. In so doing, the photographic image would reduce light intensity of the off-axis image thereby reducing unwanted glare during photography while retaining a clear and bright photograph of the on-axis image. The application of the off-axis periphery attenuation can equally be applied generally to other optical apparatus including mechanical handheld binoculars and telescopes.
The present invention is directed to an optical apparatus including a front-end lens or filter that distinctly attenuates an off-axis image more than an on-axis image. In one form, an optical filter is mounted on the light shade with a clear transparent center portion in the center and with a gradient or uniform attenuating outer portions that would attenuate the stray light effects for improved star tracking of an on-axis image passing through the center portion. There are many advantages to reducing but not completely eliminating glint, glare, stray, or bright periphery light in various optical systems. Peripheral-attenuating optical systems are applicable to star trackers, as well as Earth sensors, horizon sensors, sun sensors, optical telescopes, and infrared telescopes. Peripheral-attenuating optical filters and lenses can in general be applied to any optical systems, including commercial cameras, eyeglasses, binoculars, hobby telescopes, and video systems. Those skilled in the art can make enhancements, improvements, and modifications to the invention, and these enhancements, improvements, and modifications may nonetheless fall within the spirit and scope of the following claims.
Patent Application
20080068711
