1. Field of the Invention
The present invention relates to a method for making a member having microstructure elements arranged thereon by forming a pattern having two-dimensional periodically in air and optically recording the pattern. The optical recording process in the method includes not only the recording by visible light but also recording by lights other than visible light. Such member having microstructure elements arranged thereon is hereinafter referred to as microstructure member for the purpose of simplification of description. Examples of the microstructure member to which the present invention is pertinent are microrelief structure, micromesh structure and the like. These microstructure members are useful for many purposes in optical, chemical, printing and machinery industries. For example, they are used as a focusing plate in camera. Also, they can be used as a particle size selection filter for a polishing agent and a dotted mesh screen in printing. In this specification, the manufacturing method of such microstructure member and its use will be described particularly in connection with those microstructure members which are preferably used in the technical field of optics.
2. Description of the Prior Art
Examples of the microstructure member well-known in the optical art are fly's eye lenses and microprisms which are used in cameras as finder screen and focusing plate and in image projecting apparatus as projector screen. Other uses of the microstructure member can be found also in illumination apparatus and data processing apparatus.
Recently it has been found that the diffusion plate generally used in optical apparatus, in particular, in cameras has an important disadvantage of insufficient brightness and therefore in the art many attempts have been made to improve the diffusion plate. As an solution to the problem it has been proposed to use a fly's eye lens as finder screen in camera. However, in this case, it is required that the individual lens elements of one fly's eye lens should have each a very small diameter in the order of 10.mu. or less, for the reason described later herein. At present, there is no method available for making a fly's eye lens composed of such fine lens elements. Under the standard of the prior art, therefore, any fly's eye screen for use in camera has not yet been realized.