JPH03149519A - Plane lens for automatic focusing - Google Patents

Abstract

PURPOSE:To obtain a small-sized, light weight voltage-controlled optical element by varying the gap between the plane lens and an electrode with use of an insulating film. CONSTITUTION:An insulating film 3 such as an oxide film is formed on the surface of the plane lens 2 and ground increasing in thickness from the center part to the outside of the plane lens 2 according to an exponential function, and electrodes 4a and 4b are provided on the surface of the insulating film 3 and the surface of a dielectric 1. When a voltage is applied to the electrodes to vary the refractive index of the plane lens 2, variation in the refractive index by the electrode 4a is large at the center part of the plane lens 2 and becomes smaller outwardly. Thus, the plane lens 2 is used as one lens to vary the focal length of the lens 2 itself with the voltage of a power source 5. Further, the plane lens 2 is combined to constitute a voltage-controlled focal length varying element and the size and weight are reducible because of the voltage control is used.

Description

[Detailed description of the invention]

■Industrial application field】 TECHNICAL FIELD The present invention relates to an automatic focusing structure of a flat plate lens.

[Summary of the invention]

The present invention provides an electrode and an insulating film on the surface of a flat lens,
This realizes electrically varying the focal length of a flat lens using the electro-optic effect.

[Prior Art J] Conventionally, variable focal length has been achieved by using a plurality of lenses, such as the flat plate lens shown in FIG. 1, and changing the distance between the lenses. [Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, since the distance between the lenses is changed mechanically, the reduction in size and weight is determined by the size of the lens, and because it is mechanically driven, it is easy to break down. It has the following problems. Therefore, the present invention aims to solve these problems.
The goal is to make it small and lightweight. The present invention provides a voltage-controlled optical element.

[Means to solve the problem]

The autofocus flat lens of the present invention has a flat lens having an electrode and an insulating film on the surface of the flat lens whose refractive index changes depending on an electric field, and the distance between the flat lens and the electrode is changed by an insulating film. Features and Effects The present invention has the above-described structure, and the action of the electrodes changes the refractive index distribution of the flat lens, thereby changing the focal length. 1 Example 1 FIG. 2 is a sectional view of a flat lens according to an example of the present invention. l is a dielectric, 2 is a flat lens, 3 is an insulating film, 4a, 4b
are electrodes and 5 power supplies. Here, a flat lens refers to a flat lens in which the refractive index from the center of the flat lens to the dielectric changes according to a square distribution in the cross section of the flat lens in Figure 1(b), and the focal length of the flat lens is It is determined by the difference between the refractive index at the center of the lens and the refractive index of the dielectric. As shown in Figure 2, an insulating film such as an oxide film is provided on the surface of the flat lens by chemical vapor deposition or sputter deposition, and the thickness of the insulating film is adjusted from the center of the flat lens by etching. Grinding increases exponentially towards the outside of the flat lens. Electrodes are provided on the surface of the insulating film and the surface of the dielectric by a method such as sputter deposition. When voltage is applied to the electrodes 4a and 4b by the power source 5, 4
An electric field is generated between electrodes a and 4b. The intensity of the generated electric field becomes denser as it approaches the electrode, and becomes sparser as it moves away from the electrode. The generated electric field changes the refractive index of the second flat lens. The change in refractive index caused by the electrode 4a is large at the center of the flat lens 2, and becomes smaller as it moves outward from the center of the flat lens. Therefore, the difference in refractive index between the second flat lens and the dielectric can be changed, and the focal length of the flat lens can be changed. The refractive index of the flat lens 2 can be controlled by the voltage of the power supply 5. Therefore, the focal length of the flat lens 2 can be changed by the voltage of the power supply 5. Furthermore, when the flat plate lens shown in Figure 2 is used as one lens, the focal length of the lens itself can be changed by the voltage of the power supply. Furthermore, by combining the flat plate lenses shown in Figure 2, the mechanically driven part can be changed. It is possible to configure a voltage-controlled variable focal length element without a voltage control, and it is possible to reduce the size and weight due to the voltage control.

【Effect of the invention】

As described above, the present invention has the effect that a voltage-controlled variable focal length element can be constructed by providing an electrode on the surface of a flat lens.

[Brief explanation of the drawing]

FIG. 1(a) is a plan view of a flat lens. FIG. 1(b) is a sectional view of a flat lens. FIG. 2 is a main sectional view showing an embodiment of the flat lens of the present invention. l...Dielectric 2...Flat lens 3...Dielectric 4a, 4b...Electrode 5...More than power supply 1-10 〜、、／へ１５ ＼ ＼ 1″″l Figure 2

Claims (1)

[Claims] 1. A flat plate lens for automatic focusing, which has an electrode and an insulating film on the surface of the flat lens whose refractive index changes depending on an electric field, wherein the distance between the flat lens and the electrode is changed by the insulating film.