Optics: measuring and testing – Lens or reflective image former testing
Reexamination Certificate
1999-10-08
2001-04-24
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
Lens or reflective image former testing
C356S127000, C351S169000
Reexamination Certificate
active
06222621
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to an evaluation method and an evaluation device for evaluating the optical properties of a spectacle lens, and in particular, to a spectacle lens evaluation method and evaluation device with which optical properties can be found taking into consideration the state in which the spectacle lens is worn and the direction of the line of vision of the eye.
2. Description of the Related Art
Spectacle lenses are produced and finished in accordance with the optimized specifications of designers, and lens meters are used to evaluate the properties of a finished spectacle lens. Determination with a lens meter involves projecting parallel light beams perpendicular to the lens surface and determining lens power, etc. Moreover, lens meters that determine the addition are also known. Determinations with these lens meters are usually determinations at a spot on the lens. In contrast to this, devices that determine optical properties over a wide region on the lens have recently been presented (for example, refer to Japanese National Publication No. Hei 10-507825 and Japanese Laid-Open Patent No. Hei 8-304228).
Incidentally, it is necessary to take into consideration the differences from conventional optical systems (cameras and telescopes) when evaluating the optical properties of a spectacle lens. That is, it is possible to project people to be photographed over a wide range all at once on the film surface with a conventional optical system, such as a camera, but when the eye looks over a wide range, the eyeball captures the object as it turns around its center of rotation (eyeball movement) and moves its line of vision. This is why not all objects reflected on the retina of the eye are perceived as clear objects and only the narrow region at the fovea with high resolution can be clearly seen.
On the other hand, it is not possible to determine the light rays or light beams in the direction of the field of vision that pass through the center of rotation of the eyeball other than on the optical axis of the spectacle lens, and the refractive index of the apex in the direction of the field of vision that passes through the periphery of the spectacle lens, etc., cannot be correctly determined with a lens meter.
SUMMARY OF THE INVENTION
The present invention is based on the above-mentioned background, its objective being to present an optical lens evaluation method and evaluation device with which it is possible to find optimum spectacle lens optical properties in accordance with the state in which the spectacle lens is worn by each wearer taking into consideration the state in which the spectacle lens is worn and the direction of the line of vision of the eye.
In order to accomplish the above-mentioned objective, the method of evaluating a spectacle lens of the present invention is characterized in that it comprises the steps of finding the optical properties of each position on a spectacle lens relating to the principal ray , or beam that comprises the principal ray, that passes through the center of rotation of the eyeball from the three-dimensional data of the spectacle lens, the parameters for the state in which the spectacle lens is worn comprising distance from the surface of said spectacle lens on the eye side to the center of rotation of the eyeball, and the material parameters of the spectacle lens comprising the index of refraction of said spectacle lens as a parameter, and evaluating the spectacle lens.
That is, in order to realize the optimum optical design for spectacle lens, it is necessary to evaluate optical properties at each position (the center as well as around the periphery of the lens) of spectacle lenses with respect to the principal ray or beam in the direction of the field of vision that passes through the center of rotation of the eyeball of various types of monofocal and bifocal lenses, particularly, progressive multifocal lenses.
Moreover, it is necessary to take into consideration the state in which the spectacle lens is worn, that is, the position relationship between the spectacle lens and the eyeball, particularly the position relationship of the spectacle lens with respect to the center of rotation of the eyeball. Moreover, not only the distance from the center of rotation, but also decentering, prism prescription, forward inclination of the spectacle lens, etc., which are other factors of the state in which the spectacle lens is worn, vary from individual to individual depending on the wearer's prescription, the spectacle frames being worn, etc. Consequently, in order to more correctly evaluate optical properties of spectacle lenses, it is necessary to construct an “optical model for when a spectacle lens is worn” that uses various factors of the state in which the spectacle lens is worn, such as the above-mentioned distance from the center of rotation.
On the other hand, the use of mechanical optical devices and equipment with which it is possible to change as needed the relative position relationship of the spectacle lens with respect to the center of rotation of the eyeball is considered so that it is possible to more accurately determine optical properties of the state in which the spectacle lens is worn. Nevertheless, by means of this type of mechanical optical device it becomes necessary to re-measure the same spectacle lens every time the values of each parameter for the state in which the spectacle lens is worn, such as the distance from the center of rotation, etc., are changed, or it is necessary to move the spectacle lens to many determination positions and then measure the lens when the distribution of the refractive index of the optical lens is being determined, etc. Thus, a considerable amount of time is needed.
The state in which the spectacle lens is worn, that is, the position relationship of the spectacle lens with the center of rotation of the eyeball (optical model for when the spectacle lens is worn), is determined from three-dimensional shape data of the spectacle lens and parameters for the state in which the spectacle lens is worn comprising the distance between the surface of the spectacle lens on the eye side and the center of rotation of the eyeball as parameter, and optical properties at each position on the spectacle lens relating to the principal ray, or the beam that comprises the principal ray, in the direction of the field of vision that passes through the center of rotation of the eyeball is found from this relationship. That is, one characteristic of the present invention is that the distance between the surface of the spectacle lens on the eye side and the center of rotation of the eyeball is treated as a parameter, not a fixed element. Thus, It is possible to more accurately confirm real optical properties when the spectacle is actually worn by the spectacle wearer. In other words, the present invention focuses on fact that the distance between the surface of the spectacle lenses on the eye side and the center of the rotation of the eyeball generally differs with the spectacle wearer and the fact that when this distance is different, real optical properties as seen through the eye are so different that they cannot be disregarded, even when the optical properties of the spectacle lens itself are the same. By using this distance as a parameter, it is possible to accurately find the real optical properties when a spectacle is actually worn by a spectacle wearer, even if the above-mentioned distance varies, by, for instance, using computer simulation, etc. Further, the present invention similarly uses factors other than the above-mentioned distance that vary depending on how the spectacle is worn as a parameter of the state in which the spectacle is worn. In addition, factors that can change with the shape of the face of the wearer and fashion, etc., serve as material parameters. The real optical properties of the entire lens when the spectacle is actually worn by the spectacle wearer can be more accurately found from these parameters and th
Hoyo Corporation
Oliff & Berridg,e PLC
Pham Hoa Q.
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