JPH068933B2 - Catadioptric lens - Google Patents

Description

The present invention relates to a catadioptric lens for a 35 mm single-lens reflex camera.

(Problems of the prior art) In order to make the total length of the mirror lens compact and to achieve high performance, the air gap between the focusing unit and the main mirror unit should be widened, or both the main and secondary mirrors should be mangin killer. It is preferable to reduce the power of the group. However, these methods also have a limit, and if they are equivalent to a refracting system, the tele ratio becomes large, so the Petzval sum shifts to the positive,
Off-axis correction becomes difficult. In order to prevent this, the refractive index of the convex lens system must be raised, and there has been a problem that the cost increases in a mirror lens having a large outer diameter.

(Means for Solving the Problems) The present invention has solved the above-mentioned problem of the shift of the Petzval sum to the positive by satisfying the following conditions.

That is, a convex lens L1 having an optical system whose convex surface faces the object side,
A concave meniscus lens L2 having a transparent surface at the center and a reflective surface at the center of the surface close to the image side with the convex surface facing the image side;
A convex lens L3 and a lens L1 cemented to the image side of the lens L1
, A biconcave lens L4 having a reflecting surface on the object side, and a convex lens L5 and a lens L cemented to the object side of the lens L2.
The concave lens L6 disposed on the image side of 2 is used as a main lens system up to L5, and L6 is a magnifying system.

1.2 ≤ m ≤ 2.0 0.1 ≤ d2 / f ≤ 0.15 However, m: imaging magnification of L6 d2: air gap between L1 and L2 f: focal length of the entire system (action) In each conditional expression, the condition is to make the lens system compact This is a condition for solving the positive shift of the Petzval sum in the main lens system by using the magnifying system with one concave lens. If the lower limit of the condition is exceeded, the tele ratio cannot be obtained and the Petzval sum increases positively. If the upper limit is exceeded, it becomes difficult to correct positive distortion. The condition is a condition for relaxing the power of the main lens system. If the lower limit of the condition is exceeded, the power of the main lens system itself becomes strong, and it is possible to make it compact, but it is difficult to achieve high performance and the cost of the glass material becomes high. If the upper limit is exceeded, the power of the main lens system can be relaxed, but the total lens length increases.

(Examples) Examples of the present invention will be shown below.

Example (Effects of the Invention) The catadioptric lens of the present invention is a compact, high-performance catadioptric lens that is provided with the above-described conditions to prevent power reduction advantageous for aberration correction and prevent positive shift of Petzval sum. I was able to achieve it.

[Brief description of drawings]

FIG. 1 is a lens configuration diagram showing an embodiment of the present invention, and FIG. 2 is each aberration diagram of the embodiment.

Claims (1)

[Claims] 1. A convex lens L1 having a convex surface facing in order from the object side.
And a concave meniscus lens L having a convex surface facing the image side, a central surface of the surface close to the image side being a transmitting surface, and the rest being a reflecting surface.
2, a positive lens L3 cemented to the image side of the lens L1, a biconcave lens L4 cemented to the object side of the lens L1 and having a reflecting surface on the object side, and a convex lens L5 cemented to the object side of the lens L2.
And a concave lens L6 disposed on the image side of the lens L2 and satisfying the following conditions. 1.2 ≦ m ≦ 2.0 0.1 ≦ d2 / f ≦ 0.15 However, m: imaging magnification of L6 d2: air gap between L1 and L2 f: focal length of the entire system