Ocular optics system having at least four reflections occurring between curved surfaces

Examples 1 to 3 of the image display device constructed using the ocular optics system according to the present invention will now be explained with reference to the accompanying drawings.

Constitutional parameters of each example will now be given later. In what follows, surface numbers are given by back-tracing surfaces numbers as counted from an observer's pupil position 1 toward an image display element 6. As shown in FIG. 1, a coordinate system is composed of the origin defined by an observer's iris position 1, a Z axis defined by an observer's visual axis 2, whose direction from the origin toward an ocular optical system 7 is taken as being positive, a Y axis perpendicular to the observer's visual axis 2, whose direction from below to above with respect to an observer's eyeball is taken as being positive, and an X axis perpendicular to the observer's visual axis 2, whose direction from right to left with respect to the observer's eyeball is taken as being positive. In other words, a Y-Z plane is defined within a sheet plane of FIG. 1 while an X-Z plane is defined by a plane perpendicular to the sheet plane. An optical axis is here assumed to be turned back within the Y-Z plane on the sheet plane.

Of the constitutional parameters to be described later, Y, Z and .theta. represent amounts of decenteration of a vertex of a given surface from the reference surface (pupil position 1) in the Y and Z axis directions and an angle of inclination of a center axis of that given surface from the Z axis, respectively. Note that the plus sign attached to .theta. means the direction of counterclockwise rotation, and that the surface separation is of no significance.

For each surface, an irrotationally symmetric aspheric shape is given by

where, on the coordinates defining that surface, Ry and Rx are the paraxial radii of curvature of the aspheric surface within the Y-Z plane (sheet plane) and the X-Z plane, respectively, Kx and Ky are the conical coefficients of the aspheric surface within the X-Z plane and the Y-Z plane, respectively, AR and BR are the fourth- and sixth-order aspheric coefficients of the aspheric surface which is rotationally symmetric with respect to the Z axis, respectively, and AP and BP are the fourth- and sixth-order aspheric coefficients of the aspheric surface which is irrotationally symmetric with respect to the Z axis, respectively.

It is here to be noted that the refractive index of a medium between surfaces is given by a d-line refractive index, and that length is given in units of millimeters.

In the constitutional parameters to be described later, back-tracing is carried out from an object point position of a virtual image positioned 1-meter away from the pupil.

FIGS. 1, 2 and 3 are sectional views of Examples 1, 2 and 3 of a monocular image display device. In these drawings, reference numeral 1 stands for an observer's pupil position, 7 an ocular optical system, 2 an observer's visual axis, 3 a first surface of the ocular optical system 7, 4 a second surface of the ocular optical system 7, 5 a third surface of the ocular optical system, and 6 an image display element.

Referring to actual optical paths in these examples, a pencil of light emanating from the image display element 6 is first incident on the ocular optical system 7 upon being refracted at the first surface 3 thereof, then is internally reflected at the second surface 4, the first surface 3, the second surface 4, the first surface 3 and the third surface 5 in the described order, then incident on the first surface 3 where it is refracted, and finally projected into an observer's eyeball while the iris position of the observer's pupil or the center of rotation of the observer's eyeball is taken as the exit pupil 1.

Horizontal and vertical field angles, and pupil diameter are 18.75.degree. and 25.degree., and 8 mm for Example 1; 22.5.degree. and 30.degree., and 4 mm for Example 2; and 30.degree. and 22.5.degree., and 4 mm for Example 3.

Throughout the examples, the surfaces are all anamorphic aspheric surfaces, and the first transmitting surface, second reflecting surface, fourth reflecting surface and second transmitting surface comprise the common first surface 3 while the first reflecting surface and third reflecting surface comprise the common second surface 4.

It should be noted that the ocular optical system of this invention is usable as an image optical system capable of forming an image of an object point at a distant place.

Enumerated below are the values of the constitutional parameters in Examples 1, 2 and 3. It is to be noted, however, that .theta..sub.1 to .theta..sub.5 represent angles which, as shown in FIG. 2, the principal ray--defined by a light ray leaving the center of the image display element 6 and arriving at the center of the pupil 1--incident on the first to fifth reflecting surfaces makes with the principal ray emerging therefrom.

EXAMPLE 1

Sur- face Sur- sep- Refractive face Radius of ar- index Abbe's No. No. curvature ation (Displacement) (Tilt angle) 1 .infin. (pupil) 2 R.sub.y -427.518 1.51633 64.1 R.sub.x -29.212 Y 17.473 .theta. -5.351.degree. K.sub.y 0 Z 26.387 K.sub.x 0 AR 0 BR 0 AP 0 BP 0 3 R.sub.y -254.887 1.51633 64.1 R.sub.x -649.767 Y 130.176 .theta. 12.443.degree. K.sub.y 0 Z 52.819 K.sub.x 0 AR -0.876797 .times. 10.sup.-6 BR 0 AP -0.713380 BP 0 4 R.sub.y -427.518 1.51633 64.1 R.sub.x -29.212 Y 17.473 .theta. -5.351.degree. K.sub.y 0 Z 26.387 K.sub.x 0 AR 0 BR 0 AP 0 BP 0 5 R.sub.y -242.504 1.51633 64.1 R.sub.x -42.527 Y -31.772 .theta. -8.869.degree. K.sub.y 0 Z 36.510 K.sub.x 0 AR 0 BR 0 AP 0 BP 0 6 R.sub.y -427.518 1.51633 64.1 R.sub.x -29.212 Y 17.473 .theta. -5.351.degree. K.sub.y 0 Z 26.387 K.sub.x 0 AR 0 BR 0 AP 0 BP 0 7 R.sub.y -242.504 1.51633 64.1 R.sub.x -42.527 Y -31.772 .theta. -8.869.degree. K.sub.y 0 Z 36.510 K.sub.x 0 AR 0 BR 0 AP 0 BP 0 8 R.sub.y -427.518 Y 17.473 .theta. -5.351.degree. R.sub.x -29.212 Z 26.387 K.sub.y 0 K.sub.x 0 AR 0 BR 0 AP 0 BP 0 9 (display device) Y 55.708 .theta. -22.615.degree. Z 21.266 .theta..sub.1 = 45.degree. .theta..sub.2 = 76.degree. .theta..sub.3 = 94.degree. .theta..sub.4 = 128.degree. .theta..sub.5 = 65.degree.

EXAMPLE 2

Sur- face Refractive Sur- sep- index face Radius of ar- (Displace- Abbe's No. No. curvature ation ment) (Tilt angle) 1 .infin. (pupil) 2 R.sub.y -152.846 1.51633 64.1 R.sub.x -66.891 Y -13.768 .theta. -13.449.degree. K.sub.y 0 Z 27.500 K.sub.x 0 AR -0.178178 .times. 10.sup.-8 BR -0.594362 .times. 10.sup.-11 AP 0.105146 .times. 10 BP 0.664504 3 R.sub.y -119.363 1.51633 64.1 R.sub.x -82.534 Y 47.793 .theta. 6.177.degree. K.sub.y 0 Z 54.768 K.sub.x 0 AR -0.190871 .times. 10.sup.-6 BR 0.305496 .times. 10.sup.-11 AP 0.660695 .times. 10.sup.-1 BP 0.487236 4 R.sub.y -152.846 1.51633 64.1 R.sub.x -66.891 Y -13.768 .theta. -13.419.degree. K.sub.y 0 Z 27.500 K.sub.x 0 AR -0.178178 .times. 10.sup.-8 BR -0.594362 .times. 10.sup.-11 AP 0.105146 .times. 10 BP 0.664504 5 R.sub.y -118.626 1.51633 64.1 R.sub.x -82.339 Y -26.271 .theta. -14.237.degree. K.sub.y 0 Z 40.718 K.sub.x 0 AR -0.122336 .times. 10.sup.-7 BR -0.514035 .times. 10.sup.-12 AP -0.236341 .times. 10 BP 0.831265 6 R.sub.y -152.846 1.51633 64.1 R.sub.x -66.891 Y -13.768 .theta. -13.419.degree. K.sub.y 0 Z 27.500 K.sub.x 0 AR -0.178178 .times. 10.sup.-8 BR -0.594362 .times. 10.sup.-11 AP 0.105146 .times. 10 BP 0.664504 7 R.sub.y -118.626 1.51633 64.1 R.sub.x -82.339 Y -26.271 .theta. -14.237.degree. K.sub.y 0 Z 40.718 K.sub.x 0 AR -0.122336 .times. 10.sup.-7 BR -0.514035 .times. 10.sup.-12 AP -0.263241 .times. 10 BP 0.831265 8 R.sub.y -152.846 Y -13.768 .theta. -13.419.degree. R.sub.x -66.891 Z 27.500 K.sub.y 0 K.sub.x 0 AR -0.178178 .times. 10.sup.-8 BR -0.594362 .times. 10.sup.-11 AP 0.105146 .times. 10 BP 0.664504 9 (display device) Y 45.606 .theta. -1.625.degree. Z 22.237 .theta..sub.1 = 52.degree. .theta..sub.2 = 85.degree. .theta..sub.3 = 87.degree. .theta..sub.4 = 124.degree. .theta..sub.5 = 66.degree.