JP2012042791A5 - - Google Patents

Description

The optical system of the present invention includes a cemented lens, the optical system including a holding member for holding the cemented lens, the image-side lens of the cemented lens has a larger outer diameter than the object-side lens, the image side lens The outer peripheral portion has a positioning portion for determining the position of the cemented lens in the optical axis direction, and the holding member holds the cemented lens by sandwiching the positioning portion from the object side and the image side. when the distance on the optical axis from the image plane to the lens surface on the most object side of the cemented lens L, and the focal length of the optical system is f,
0.2 <L / f <1.0
It satisfies the following conditional expression.

In addition to the stress generated at the periphery of the lens when the adhesive is cured in the cemented lens, the present inventor further increases the birefringence when stress from the holding mechanism (holding member) is applied to the portion. Was found to deteriorate.

Conventionally, in the holding method of the cemented lens in the lens holding frame, the both sides of the cemented lens are pressed down. Alternatively, the outer diameter of the lens on the image side having a small effective diameter is made smaller than the outer diameter of the lens on the object side, and is pressed only by the lens on the object side. In the case of the former, stress due to the curing of the adhesive and stress from the holding mechanism are applied twice on the positive lens side where the thickness is particularly thin at the periphery of the lens, and the birefringence of the material of the positive lens is greatly generated. I understood that. In the latter case, the stress from the holding mechanism is concentrated on the lens on the object side, so that a large birefringence is generated in the material of the lens on the object side together with the stress due to the curing of the adhesive. Furthermore, since the axial ray height h of the lens on the object side is large, the influence of birefringence appears more conspicuously with respect to the pupil peripheral luminous flux.

The cemented lens C1 is disposed at a position of L / f = 0.57 in the optical path, and the cemented lens C2 is disposed at a position of L / f = 0.32 in the optical path, both satisfy the conditional expression (1). ing. For this reason, in each of the cemented lenses C1 and C2, the image forming position of the light beam passing through the lens peripheral portion of the axial light beam is apt to vary. The cemented lens C1 is configured by cementing a positive lens (object side positive lens) 1 and a negative lens (image side negative lens) 2 in order from the object side to the image side as shown in the lens holding mechanism of FIG. Has been. The outer diameter of the image side negative lens 2 is larger than that of the object side positive lens 1. The cemented lens C1 is positioned outside the outer periphery of the object-side positive lens 1, and a lens barrel (lens holding frame) 4 having two planar portions 5 and 6 as positioning portions for positioning in the optical axis direction as holding members. The holding ring 3 is sandwiched from both the object side and the image side to hold the optical axis direction.

The holding of the cemented lens C1 in the radial direction by the lens barrel 4 is determined and held by abutting the outer peripheral plane portion 7 of the image side negative lens 2 against the inner peripheral surface of the lens barrel 4. As shown in FIG. 3B, the cemented lens C2 is configured by cementing a positive lens (object-side positive lens) 1 and a negative lens (image-side negative lens) 2 in order from the object side to the image side. The outer diameter of the image side negative lens 2 is larger than that of the object side positive lens 1. The cemented lens C <b> 2 abuts the object-side flat portion 5 of the negative lens 2 positioned in the optical axis direction outside the outer periphery of the object-side positive lens 1 against the abutting portion 4 a of the lens barrel 4. Then, a part of the caulking claw 8 of the lens barrel 4 is thermally deformed and applied to the flat surface portion 6 as a positioning portion on the image side of the negative lens 2 to hold in the optical axis direction. Here, the abutting portion 4a and the caulking claw 8 are holding members that hold the flat portions 5 and 6 by sandwiching them from both the object side and the image side.

Next, numerical examples 1 to 3 corresponding to the respective examples will be shown. In each numerical example, i indicates the order of the optical surfaces from the object side, ri is the radius of curvature of the i-th optical surface (i-th surface), di is the distance between the i-th surface and the i + 1-th surface, ndi and νdi indicate the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line, respectively. In addition to specifications such as focal length and F number, the angle of view is the half angle of view of the entire system, the image height is the maximum image height that determines the half angle of view, the total lens length is the distance from the first lens surface to the image surface , BF indicates the length from the final lens surface to the image plane.

Claims (12)

A cemented lens, the optical system including a holding member for holding the cemented lens, the image-side lens of the cemented lens has a larger outer diameter than the object-side lens, the outer peripheral portion of the image-side lens, the cemented lens The holding member holds the cemented lens by sandwiching the positioning unit from the object side and the image side, and the cemented lens from the image plane. most distance along the optical axis between the object side lens surface L, the focal length of the optical system is f, the
0.2 <L / f <1.0
An optical system that satisfies the following conditional expression: When the distance on the optical axis from the lens surface closest to the object side of the optical system to the image plane is Ltotal, 0.4 <Ltotal / f <1.2
The optical system according to claim 1, wherein the following conditional expression is satisfied. 3. The optical system according to claim 1, wherein two positioning portions of the image side lens are provided apart from each other in the optical axis direction, and the two positioning portions are formed of plane portions parallel to each other . 0.05 <dout / dcen <0.80 where the distance in the optical axis direction between the flat portions of the two positioning portions is dout and the center thickness of the cemented lens is dcen.
The optical system according to claim 3, wherein the following conditional expression is satisfied: The cemented lens includes a positive lens and a negative lens. Of the light incident / exit surfaces of the positive lens, the smaller diameter is dea, and the thickness in the optical axis direction at the outermost periphery of the diameter of the light incident / exit surface is dcov. 0.02 <dcov / dea <0.40
The optical system according to claim 1, wherein the following conditional expression is satisfied.   The optical system according to claim 1, wherein the cemented lens includes a positive lens and a negative lens in order from the object side to the image side.   The optical system includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power that moves on the optical axis during focusing, and a third lens group having a positive refractive power. The optical system according to claim 1, further comprising:   The optical system according to claim 7, wherein the cemented lens is included in the second lens group. In order from the object side to the image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having positive refractive power, a fourth lens unit having a negative refractive power, positive the fifth lens group refractive power, a sixth lens unit having a negative refractive power, is composed of a seventh lens unit having a positive refractive power, the seventh lens group and the fifth lens group and the second lens group, a move for zooming, the sixth lens group and the third lens group and the third lens group and the fourth lens group moves during zooming, the cemented lens is disposed in the second lens group the optical system according to any one of claims 1 to 6, characterized in that is.   The optical system according to claim 1, wherein the holding member includes a lens holding frame and a pressing ring. The optical system according to claim 1, wherein the holding member includes an abutting portion of the lens holding frame and a crimping claw of the lens holding frame. An optical apparatus comprising: the optical system according to any one of claims 1 to 11 ; and a solid-state imaging device that receives an image formed by the optical system.