Abstract An optical system is disclosed which is adapted for use in a reticle type infrared seeker. The effect of central obscurations caused by the structural support of a primary catadioptric focusing arrangement is reduced by the use of a light pipe and a field lens disposed between the image plane of such focusing arrangement and a photodetector. The disclosed catadioptric arrangement focuses the infrared energy from a target into a small spot in an image plane, the position of the spot being related to the angular deviation of the target from the optical axis of the system. Because of central obscuration caused by the support structure the focused energy is in the form of a hollow annular cone, the apex thereof forming the spot. A reticle is provided in the image plane to modulate the intensity of the energy in accordance with the position of the spot in the image plane. Such modulated energy is then directed to a photodetector through a field lens and a light pipe. The field lens, light pipe and photodetector are suitably arranged so that ring-shaped radiation entering the light pipe is dispersed in the plane of the face of the photodetector. The disclosed system is particularly suitable for use where the catadioptric arrangement, the reticle, the field lens and the light pipe are gimballed with respect to the photodetector.
An optical arrangement, comprising: a. a photodetector; b. means for focusing the apex of a cone of energy having a hollow central portion at a small spot in an image plane, such small spot being the apex of a cone of exiting energy having a hollow central portion; and c. means disposed between the image plane and the photodetector for dispersing the exiting energy over the central portion thereof at the photodetector.
Claim 2
Dependent Claim
72 words
An optical arrangement, comprising: a. a photodetector; b. means for focusing the apex of a cone of energy having a hollow central portion at a small spot in an image plane, such small spot being the apex of a cone of exiting energy having a hollow central portion; and c. means disposed between the image plane and the photodetector for dispersing the exiting energy over the central portion thereof at the photodetector.
Claim 3
Dependent Claim
15 words
The optical arrangement recited in claim 1 wherein the dispersing means includes a light pipe.
Claim 4
Dependent Claim
79 words
The optical arrangement recited in claim 2 wherein: a. the entering energy focused at the small spot passes through the image plane in the shape of a hollow cone of exiting energy defined by inner and outer rays; and b. the dispersing means includes a field lens means disposed between the image plane and the light pipe for directing the inner rays of the cone of energy at a position coincident with the exit end of the light pipe.
Claim 5
Dependent Claim
45 words
The optical arrangement recited in claim 2 wherein a reticle means is disposed between the image plane and the light pipe for modulating the intensity of the energy in the image plane in accordance with the position of the small spot in such image plane.
Claim 6
Dependent Claim
23 words
The optical arrangement recited in claim 2 including means adapted to rotate the focusing means and the dispersing means relative to the photodetector.