JPS63294502A - Single lens - Google Patents

Abstract

PURPOSE:To forbid the movement of an image point even if a lens inclines by forming the whole or part of at least one face of the lens, whose faces is not required to be passed with rays, to a spherical shape so that the center of curvature of the spherical phase coincides with the nodal point of the lens. CONSTITUTION:The single lens 1 is formed to the spherical shape in the whole or part of at least one face of the lens, whose face is not required to be passed with rays, so that the center of the curvature of this spherical phase is made to coincide with the nodal point 10 of the lens. Even if, therefore, the lens inclines, the nodal point 10 does not move as the contact part of a lens barrel 2 and the lens 1 constitutes the spherical phase around the nodal point 10 of the lens 1. The incident rays on the lens 1 toward the nodal point 10 thereof do not change the direction thereof. The image point is, therefore, formed at the position based on the lens barrel 2 even if the lens 1 is mounted with an inclination to the lens barrel 2 when the lens 1 is inserted and fixed into the barrel 2. The adjustment for mounting is thus exceedingly facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention makes it easy to form an image at a predetermined position when a lens is fixed, and even if the lens moves due to various factors after the lens is fixed. , concerns a single lens whose image position can be made to vary little.

Conventional technology Optical disc and compact disc pickups include
Many optical parts are used. In particular, extremely high sensitivity is required for objective lenses and collimator lenses. On the other hand, minute optical elements are also used in optical communications. These lenses are required to have high precision and low cost, and in recent years, aspheric surfaces have been particularly popular. Therefore, what used to require a plurality of spherical lenses is now requiring only one aspherical lens.

FIG. 6 is a cross-sectional view of a conventional single lens. lens 24
is inserted into the lens barrel 2. Parallel light rays 8 are incident on the lens and are focused on an image point 9. In FIG. 6(a), since the optical axis 6 of the lens and the central axis 7 of the lens barrel coincide, the image point 9 is aligned on the central axis 7 of the lens barrel. On the other hand, if the lens is slightly tilted within the lens barrel 2, as shown in FIG. 6(b), the light rays incident on the 0 node where the lens node 10 is off the center axis 7 of the lens barrel will exit in the same direction. Therefore, the image point 25 when the lens is tilted is laterally shifted by d compared to when the lens is not tilted. (For example, Kazuo Miyake, "Geometric Optics" (June 1, 1981), Kyoritsu Publishing Co., Ltd., P39-P42) Problems to be Solved by the Invention However, with the above configuration, the tilt of the lens As a result, the nodal point of the lens moves, resulting in a problem in that the image point moves.

In view of the above-mentioned problems, the present invention focuses on the central axis of the lens barrel when a lens is inserted into the lens barrel, regardless of the inclination of the lens, and also prevents the lens from moving after installation due to vibration or aging. The objective is to provide a single lens whose imaging position does not change even when the image formation position changes.

Means for Solving the Problems In order to solve the above problems, the single lens of the present invention has at least one surface of the lens, in which all or part of the surface through which light rays do not need to pass, has a spherical shape, The center of curvature of the spherical surface is made to coincide with the node of the lens.

Effects The present invention has the above-described configuration, so that even if the lens is tilted, the contact portion between the lens barrel and the lens is a spherical surface centered on the nodal point of the lens, so the nodal point does not move. A ray of light incident toward a node of a lens does not change its direction. As a result, the image point can be prevented from moving even if the lens is tilted.

EXAMPLE Hereinafter, a single lens according to an example of the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional view of a single lens in a first embodiment of the invention. Figure 1 (
In a), the aspherical lens 1 is placed in the lens barrel 2. The aspherical lens 1 and the lens barrel 2 are in contact at a lens contact portion 3. Generally, a clearance is provided between the edge 4 of the aspherical lens 1 and the inner wall 5 of the lens barrel 2 to facilitate insertion of the lens. When the lens is in the desired position, the optical axis 6 of the aspherical lens 1 and the central axis 7 of the lens barrel coincide. When a light ray 8 parallel to the central axis 7 enters the aspherical lens 1 in this state, an image point 9 is formed on the optical axis 6 of the lens. On the other hand, as shown in FIG. 2(b), suppose that the aspherical lens 1 is tilted within the lens barrel 2, and the optical axis 6 of the lens and the central axis 7 of the lens barrel are not parallel. Lens contact part 3 of aspherical lens 1
The surface shape in is a part of a spherical surface of radius R centered on the node 10 of the lens. However, the lens surface 11 within the effective diameter is an aspherical surface necessary for lens design.

Even if the aspherical lens 1 is tilted, the nodal point 10 of the lens remains on the central axis 7 of the lens barrel. The ray passing through the central axis 7 of the lens barrel is at node 1
Pass through 0. Therefore, a ray 8 parallel to the central axis 7 is focused on the same image point 9 as if the aspherical lens 1 were not tilted at all. Even if the lens placed in the lens barrel is tilted due to some influence, such as temperature change or vibration, the image point of the lens will not move.

FIG. 2 shows an optical system in which diverging light is emitted from a light source 12 and is converted into parallel light by an aspherical lens 1.

Such an optical system is often used in optical disk pickups to convert semiconductor laser light into parallel light. FIG. 2(a) shows a case where the aspherical lens 1 is installed so that the optical axis 6 of the aspherical lens 1 and the central axis 7 of the lens barrel coincide. At this time, the thousand-line light 13 is emitted parallel to the central axis 7 of the lens barrel. On the other hand, FIG. 2(b) shows a case where the aspherical lens 1 is tilted with respect to the central axis 7 of the lens barrel. In this case as well, the shape of the aspherical lens l in the lens contact portion 3 where the aspherical lens 1 and the lens barrel 2 are in contact is a part of a spherical surface with a radius R centered on the node 10, so that the light source 12 The light rays diverged from the central axis 7 of the lens barrel 2. It is emitted as parallel light rays 13 parallel to . In this way, even if the lens is tilted into the lens barrel, the direction of the emitted parallel light is always constant, so there is no need to readjust the optical system thereafter.

FIG. 3 is a cross-sectional view of a single lens showing a second embodiment of the invention. The single-sided aspherical lens 14 has a spherical surface 15 on the light incident side, and the spherical surface 15 is a spherical surface having a radius R1 centered on the nodal point 10 of the lens. On the other hand, the surface on the side from which the light rays are emitted is an aspherical surface 16. This single-sided aspherical lens 14 is inserted into the lens barrel 2 and further fixed by a spacer 19. The lens surface near the contact point 18 between the spacer 19 and the aspherical surface 16 is a part through which light rays do not pass, and the nodal point 10
It is part of the spherical surface of Patent R2, which is characterized by There is a clearance of several μm to several tens of μm between the lens barrel 2 and the edge 4 of the lens in order to facilitate insertion of the lens.

Therefore, the lens can rotate within the lens barrel 2, but since the center of rotation coincides with the nodal point 10 of the lens, parallel light, vj
! The position of the image point 9 formed when the light beam 8 is incident does not change.

FIG. 4 is a cross-sectional view of a single lens showing a third embodiment of the present invention. The aspherical lens 1 is for focusing the light rays emitted from the light source 20 to the image point 9.

Such lenses are often used, for example, in the field of optical communications to focus laser light onto a fiber. The part outside the effective diameter of the aspherical surface 11 of the aspherical lens 1 is a spherical surface with a radius R centered on the node 10, and the lens barrel 2
Even if the aspherical lens l is tilted within the lens, the image point 9 does not move.

FIG. 5 is a cross-sectional view of a single lens showing a fourth embodiment of the present invention. In the first to third embodiments, the spherical surface centered at the nodal point near the contact point between the lens and the lens barrel was smoothly connected to the spherical or aspherical surface within the effective diameter through which the light ray passes. However, in the fourth embodiment, one side of the lens 21 consists of an effective surface 22 and a lens contact surface 23, with a step between them. The lens contact surface 23 is at the node I
It is a spherical surface with radius R centered at O.

In each embodiment, only one image point has been described, but the same applies to the case where a two-dimensional image is formed, and the image plane itself does not move due to the tilt of the lens.

Effects of the Invention As described above, in the present invention, at least one surface of the lens through which light rays do not need to pass is entirely or partially spherical, and the center of curvature of the spherical surface coincides with the node of the lens. By configuring the lens to adjustment becomes easy. Furthermore, even if the lens is properly fixed initially, the lens may move due to subsequent vibrations or temperature changes. Even in such a case, there is no movement of the image point, and an optical system with little aging can be achieved. Similarly, in an optical system that converts a light beam into parallel light, the angle of the emitted light can be made not to change depending on the inclination of the lens. Furthermore, by manufacturing such lenses by press molding, it is possible to manufacture lenses that use aspherical surfaces with high accuracy and are easy to adjust, inexpensively and in large quantities.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a single lens according to the first embodiment of the present invention, Fig. 2 is a sectional view of a lens when converting a diverging ray into parallel light, and Figs. FIG. 6 is a sectional view of a conventional single lens. 1... Aspherical lens, 2... Lens barrel, 9
...image point, 10...node. Name of agent: Patent attorney Toshio Nakao Haka1 person!・-Last-tsubo surface lens z-4 Menu kite 10--Ichikushiki (IL) (b) Fig. 2 Fig. 3 Fig. 4 Fig. 5 1θ Fig. 6 ((L) Cb)

Claims (2)

[Claims] (1) All or part of at least one surface of the lens through which light rays do not need to pass is spherical, and the center of curvature of the spherical surface is aligned with a node of the lens. One lens. (2) The single lens according to claim (1), wherein at least one surface is a spherical lens, and the center of curvature of the spherical surface is made to coincide with a node of the lens.