Optics: measuring and testing – Lens or reflective image former testing
Reexamination Certificate
1999-05-18
2001-05-22
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
Lens or reflective image former testing
C356S127000
Reexamination Certificate
active
06236453
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an improvement in a lens meter capable of displaying distribution mapping of the spherical degree, cylindrical degree, axial angle, and prism degree of a progressive power lens which is a subject lens to be tested (e.g., an eyeglass lens).
2. Description of the Related Art
In recent years, lens meters have been developed. The lens meter is equipped with a light source for generation of a measuring light beam. A progressive power lens (varifocal lens) is set in the optical path of the measuring light beam, and the images of a great number of patterns based on the measuring light beam transmitted through a wide area on the progressive power lens are received, thereby measuring the wide area and performing the image display (mapping display) of the distribution of a spherical degree S (see FIG.
26
(
a
)), a cylindrical degree C (see FIG.
26
(
b
)), an axial angle A (see FIG.
26
(
c
)), and a prism degree Prs (see FIG.
26
(
d
)).
In this kind of lens meter, a subject lens is arranged in an optical path so that the central portion of the subject lens is aligned with the center of measurement of the optical path, and a measuring light beam is transmitted through the wide area of the subject lens, thereby measuring the lens characteristics at each measuring point on the wide area of this subject lens. The lens meter is equipped with imaging/displaying means. The imaging/displaying means displays the lens characteristic information about at least a spherical degree S, a cylindrical degree (astigmatism degree) C, an axial angle A, and a prism degree Prs, based on the lens characteristics at each measuring point on the wide area of this eyeglass lens, and also performs mapping display with the center O of measurement on a screen corresponding to the center of measurement of the optical path as a reference.
When the measurement of an eyeglass lens is performed, there are cases where the lens characteristic values of the spherical degree S, cylindrical degree C, axial angle A, and prism degree Prs of the eyeglass lens are desired to be determined by measuring only a few narrow areas on the eyeglass lens. However, if the lens characteristic values of the spherical degree S, cylindrical degree C, axial angle A, and prism degree Prs of only a desired narrow area on an eyeglass lens are attempted to be obtained with an exclusive lens meter for mapping display, there are the problems that it will take time to obtain each lens characteristic value of the desired narrow area alone and it will be difficult to quickly obtain each lens characteristic value of the desired narrow area alone, because there is a need to compute a great number of measured values obtained by measuring a wide area on the eyeglass lens.
For example, in the case where an eyeglass lens is a lens having substantially the same power all over the surface thereof, such as a general spherical lens or a lens for astigmatism, each lens characteristic value of the spherical lens can be determined by measuring a portion of the spherical lens for astigmatism. In such a case, although it is desirable to measure the lens characteristic values of the spherical degree S, cylindrical degree C, axial angle A, and prism degree Prs of the eyeglass lens by measuring only a desired narrow area of the eyeglass lens, there is the problem that an exclusive lens meter for mapping display will take time for measurement.
Also, where an eyeglass lens as a subject lens is a progressive power lens, there are cases where the measurement is desired to be performed by judging a far point portion (distance portion) M
1
and a near point portion (near portion) M
2
(see FIG.
26
(
b
)) from the entire data. In order to obtain accurate values of lens characteristics at the far point portion M
1
and the near point portion M
2
as the measuring points, the progressive power lens is demanded to be placed so that the rear surface of a point to be measured is perpendicular to the axis of a measuring light beam. Hence, in this kind of lens meter, in the state where the rear surface of a subject lens is attached closely to the lens receiver, the subject lens is moved with respect to the measuring light beam so that a desired measuring point on the subject lens is positioned at the center of measurement of the optical path, thereby perpendicularly projecting the measuring light beam onto the measuring point and performing the measurement.
In the aforementioned conventional lens meter capable of mapping display, the lens characteristics at each measuring point on the wide area of a subject lens are measured and image processing is performed based on the lens characteristics at each measuring point, thereby displaying image information on a screen. For this reason, the imaging process takes time, and the movement of a subject lens does not match with an image being displayed on a screen in real time. That is, after the subject lens has been moved, an image where the measuring point and the center of measurement are aligned with each other is displayed late on the screen. Hence, in correspondence with the movement of the subject lens, it is preferable to display in real time an image where the measuring point and the center of measurement are aligned with each other.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a lens meter which is capable of performing both the measurement of only a narrow area on an eyeglass lens and the measurement of the whole area.
Another object of the present invention is to provide a lens meter which is capable of displaying in real time an image where a measuring point and a center of measurement are caused to coincide with each other in correspondence with the movement of a subject lens.
In accordance with one aspect of the present invention, there is provided a lens meter comprising: a light source for generation of a measuring light beam; a normal mode in which lens characteristic values obtained by measuring a narrow area of an eyeglass lens are displayed; and a wide-area measuring mode in which a wide area of the eyeglass lens is measured and thereafter mapping display is performed.
Preferably, a pattern forming plate is provided in an optical path of the measuring light beam, and the pattern forming plate has a central pattern for measuring lens characteristics of the narrow area of the eyeglass lens and a plurality of peripheral patterns for measuring lens characteristics of the wide area of the eyeglass lens. The pattern forming plate can be switched between the normal mode which receives the image of the central pattern based on the measuring light beam transmitted through the narrow area of the eyeglass lens and also measures the narrow area alone and displays the measured values and the wide-area measuring mode which receives a great number of images of the peripheral patterns based on the measuring light beam transmitted through the wide area of the eyeglass lens and also measures the wide area and performs mapping display.
Preferably, the light source has a wavelength distribution characteristic and a plurality of wavelength characteristics. An image receiving path for receiving the image of a pattern based on the transmitted measuring light beam is divided into a first image receiving path which receives the image of the central pattern and a second image receiving path which receives the images of the peripheral patterns based on the transmitted measuring light beam. A beam splitter is provided at a position at which the image receiving path is divided into the first and second image receiving paths, and the beam splitter transmits a portion of the transmitted measuring light beam and reflects the remaining portion.
Furthermore, an optical magnifying system for magnifying the image of the central pattern is provided in the first image receiving path.
In a preferred form of the present invention, the light source is equipped with first and second light sources which generate measuring light beams different in wave
Fukuma Yasufumi
Ikezawa Yukio
Kato Takeyuki
Yanagi Eiichi
Finnegan, Henderson Farabow, Garrett and Dunner L.L.P.
Kabushiki Kaisha Topcon
Pham Hoa Q.
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