Refractive characteristics measuring apparatus for measuring the refractive characteristics of a lens

A refractive characteristics measuring apparatus enables the measurement of the refractive characteristics of a progressive multifocal lens through the observation of a geometrical test pattern through the lens. The apparatus comprises selector switches for selecting a desired geometrical test pattern, modifying the geometrical test pattern and moving the geometrical test pattern, a pattern generator for generating data representing the selected geometrical test pattern, a display for displaying the selected geometrical test pattern, and supporting members for supporting the lens on the display. The geometrical test pattern displayed on the display is observed through the lens to determine the respective positions of the far viewing section and near viewing section of the progressive multifocal lens through the observation of the geometrical test pattern distorted according to the distribution of refractive power in the progressive multifocal lens.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a refractive characteristics measuring 
apparatus for measuring the refractive characteristics of a lens to 
determine the distribution of refractive power in the lens and, more 
particularly, to a refractive characteristics measuring apparatus for 
determining the respective positions of the far viewing section and near 
viewing section of a progressive multifocal lens through the measurement 
and observation of the distribution of refractive power in the progressive 
multifocal lens. 
2. Description of Related Art 
The refractive power of a progressive multifocal lens, which has become 
prevalent in recent years, varies continuously from a far viewing section 
through a progressively varying focus area to a near viewing section. The 
progressive multifocal lens is similar in appearance to a single-focus 
lens and it is impossible to discriminate between the far viewing section 
and near viewing section of the progressive multifocal lens from the 
appearance of the same. 
Therefore, the far viewing section and near viewing section of a 
progressive multifocal lens as manufactured, such as a progressive 
multifocal lens as shipped from the lens maker, are indicated by marks and 
dimensions of the respective positions of the far viewing section and the 
near viewing section, which differ between progressive multifocal lenses 
of different types. The respective positions of the far viewing section 
and the near viewing section are determined by measuring the progressive 
multifocal lens with reference to concealed marks indicating reference 
points and additive diopter or by placing the progressive multifocal lens 
on a layout chart showing the far viewing section and the near viewing 
section and printed on a sheet of paper. The respective refractive powers 
of the far viewing section and the near viewing section are measured 
individually by a lens meter. 
However, it is difficult and requires much time to determine the respective 
positions of the far viewing section and near viewing section of the 
progressive multifocal lens by measuring the progressive multifocal lens 
after the progressive multifocal lens has been shaped and framed. 
Furthermore, there have been no effective optical measures for detecting 
errors in the specified positions of the far viewing section and the near 
viewing section and it is possible that the respective positions of the 
far viewing section and near viewing section are determined erroneously by 
measurement. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a 
refractive characteristics measuring apparatus for measuring the 
refractive characteristics of a progressive multifocal lens, capable of 
readily determining the respective positions of the far viewing section 
and near viewing section of the progressive multifocal lens through the 
observation of the distribution of refractive power in the progressive 
multifocal lens. 
To achieve the objects and in accordance with the purpose of the invention, 
as embodied and broadly described herein, the refractive characteristics 
measuring apparatus for measuring the refractive characteristics of a lens 
of this invention comprises selector switches including a pattern selector 
switch to be operated for selecting a geometrical test pattern, to be used 
for the observation of the distribution of refractive power, from among a 
plurality of geometrical test patterns, a pattern generating means for 
generating data representing a geometrical test pattern selected by 
operating the pattern selector switch and storing the same in a memory, a 
display means for displaying the selected geometrical test pattern 
represented by the data generated by the pattern generating means and a 
support means for supporting the lens on the display means for the 
observation of the distribution of refractive power in the lens.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1 showing a refractive characteristics measuring 
apparatus in a preferred embodiment according to the present invention, a 
pair of glasses 1 holding a pair of lenses to be tested in rims is 
supported on a central support 2 resembling the nose, and a pair of frame 
supports 3 disposed, respectively, on the opposite sides of the central 
support 2. The central support 2 is laterally slidable on a console along 
a guide groove 5, and the frame supports 3 can be vertically moved for 
height adjustment along guide grooves 9. Although the height of the frame 
supports 3 need not be adjusted very accurately for normal refractive 
characteristics measurement, it is desirable to move the frame supports 3 
by a motor or the like when changing the size of a geometrical test 
pattern for the observation of the distribution of refractive power by 
changing the distance between the lenses and the surface of the screen of 
a display 6, such as a CRT, for displaying a geometrical test pattern. The 
display 6 may be any suitable display other than a CRT, such as an 
electroluminescence (EL) display, a liquid crystal display (LCD) or a 
plasma display capable of displaying images formed by computer graphics. 
In view of constructing the refractive characteristics measuring apparatus 
in a small size and reducing the distortion of a displayed image, a 
backlight LCD, an EL panel and a plasma display are preferred to the CRT. 
Different geometrical test patterns will be described later with reference 
to FIG. 2. 
A switching unit 7 is operated when displaying a geometrical test pattern 
on the display 6. The switching unit is provided with push buttons A, B, C 
and D for operating switches SWA, SWB, SWC and SWD, and a push button 8 
for operating a main switch. 
Referring to FIG. 2, the push button A is operated to select a geometrical 
test pattern among four kinds of geometrical test patterns, i.e., a 
pattern of a grid, a pattern of dots, a pattern of parallel straight lines 
and a pattern of concentric circles, to be displayed on the display 6 for 
the observation of the distribution of refractive power of the lenses 1. 
The four kinds of geometrical test patterns are selected sequentially as 
shown in FIG. 2(a) by repeatedly depressing the push button A. 
The push button B is operated to select an operating mode among three 
operating modes, i.e., a pattern modifying mode in which the size and the 
arrangement of components of the selected geometrical test pattern can be 
changed, a pattern moving mode in which the selected geometrical test 
pattern can be moved in a desired direction, and a speed selection mode in 
which the speed of movement of the selected geometrical test pattern can 
be changed. These operating modes are selected sequentially as shown in 
FIG. 2(b) by repeatedly depressing the push button B. 
The push buttons C and D are operated to change the size of the selected 
geometrical test pattern, to select a geometrical test pattern moving 
method or the like according to the operating mode selected by depressing 
the push button B as shown in FIG. 2(c). The selected geometrical test 
pattern can be moved by vertical translation, horizontal translation, 
diagonal translation or turning. 
The results of operation of the push buttons A, B, C and D are displayed in 
a lower area of the screen of the display 6. 
An electric system incorporated into the refractive characteristics 
measuring apparatus will be described hereinafter with reference to FIG. 
3. 
Selection signals representing selections selected by operating the 
respective push buttons A, B, C and D of the operating switches SWA, SWB, 
SWC and SWD are processed and the processed selection signals are given to 
a microcomputer 10. Then, the microcomputer 10 instructs a display 
controller 11 to send plotting information to the four frames a, b, c and 
d of a frame buffer memory, and to send address information through a 
latch 12 to the frame buffer memory 13, so that the geometrical test 
pattern and characters are stored in the frame buffer memory 13. The 
function information concerning the functions of the switches SWA, SWB, 
SWC and SWD is written in the frame a and the contents of the frame a are 
displayed in a lower area of the screen of the display 6. Information for 
carrying out animating functions for the translation or turning of the 
geometrical test pattern is written in the frames b and c. The selected 
geometrical test pattern is written in the frame b by the display 
controller 11 and the geometrical test pattern is displayed. Meanwhile, a 
geometrical test pattern formed by slightly shifting the frame b is 
written in the frame c, and then, the frame c is displayed after the 
completion of displaying the frame b. Thus, the frames b and c are 
displayed alternately and, consequently, the geometrical test pattern 
looks as if the same is moved continuously. 
The frame buffer memory 13 may be provided with a single frame if the 
ability of the display controller 11 permits. 
The information written in the frames is transferred from the frame buffer 
memory 13 to an image generating circuit 14 to generate an image. Image 
signals of a parallel data representation representing the generated image 
are converted into those of a serial data representation by a 
parallel-serial converter 15, the image signals are converted into analog 
video signals by a D/A converter 16, and then, the analog video signals 
are synchronized by a horizontal synchronizing signal and a vertical 
synchronizing signal to display a picture represented by the video signals 
on the display 6. A clock signal generated by an oscillator 17 is given to 
the display controller 11 and the parallel-serial converter 15 to 
synchronize the information processing operation of the display controller 
11 and the parallel-serial converter 15. 
The use of the geometrical test pattern on the refractive characteristics 
measuring apparatus thus constructed will be described hereinafter. 
When the geometrical test pattern is observed through a progressive 
multifocal lens, the progressive section, the general disposition of the 
far viewing section and the near viewing section and the general 
distribution of refractive power can be recognized from the mode of 
distortion of the geometrical test pattern as shown in FIG. 4. However, 
the effect of the geometrical test pattern on showing the distortion 
caused by a lens is dependent on intervals between the component lines of 
the geometrical test pattern, and only a single geometrical test pattern 
is unable to serve properly for the measurement of refractive 
characteristics of all kinds of lenses of different refractive powers. 
Furthermore, the distribution of refractive power can be more readily 
recognized when the geometrical test pattern is moved because the 
geometrical test pattern passes under the entire area of the lens when the 
geometrical test pattern is moved. 
The characteristic method of using each pattern will be described 
hereinafter. 
Pattern of a Grid 
The pattern of a grid may be moved by vertical translation, horizontal 
translation, diagonal translation or turning. When the pattern of a grid 
is translated vertically, the vertical lines looks stationary and the 
horizontal distribution of refractive power can be recognized from the 
distortion of the horizontal lines, and vice verse when the pattern of a 
grid is translated horizontally. 
The distribution of refractive power can be more readily recognized when 
the pattern of a grid is translated diagonally or turned because both the 
vertical and horizontal lines are distorted simultaneously when the 
pattern of a grid is translated diagonally or turned. 
Pattern of Dots 
The pattern of dots are regarded as an arrangement of the intersection 
points of the pattern of a grid. When the pattern of dots are observed 
through a lens for astigmatic correction or a progressive multifocal lens 
for astigmatic correction, deformed dots of different sizes can be seen, 
which intensifies difference in brightness and irregular arrangement of 
the dots. 
Pattern of Parallel Lines 
Pattern of parallel lines are formed by omitting either the vertical lines 
or the horizontal lines of the pattern of a grid. Accordingly, the pattern 
of parallel lines is effective, when turned, on the determination of the 
direction of an axis of a lens for astigmatic correction or a progressive 
multifocal lens for astigmatic correction. It is desirable to indicate the 
angle of turning of the pattern of parallel lines at a corner of the 
screen of the display 6. 
A cross target consisting of a plurality of perpendicularly intersecting 
straight lines, which is used on manual lens meters, is a modification of 
the pattern of parallel lines. The direction of an axis can be exactly 
determined from the densities of the straight lines by turning a cross 
target consisting of a plurality of intersecting straight lines of the 
same line width. 
Pattern of Concentric Circles 
When a pattern of concentric circles is aligned with the optical center of 
a lens for astigmatic correction or the center of the far viewing section 
of a progressive multifocal lens, the distribution of refractive power of 
the lens can be known from the dislocation of the circles according to the 
distribution of refractive power. 
In operation, the push button 8 of the main switch is operated to connect 
the refractive characteristics measuring apparatus to a power source. In 
this initial state, the pattern of a grid is displayed on the display 6. A 
pair of glasses is set on the frame supports 3 in a horizontal position. 
The height of the pair of glasses is adjusted by moving the frame supports 
3 so as to facilitate the distribution of refractive power. The push 
button A is operated to select a desired geometrical test pattern, the 
push button B is operated to determine intervals between the lines of the 
geometrical test pattern, and the push buttons C and D are operated to 
select intervals that will cause large distortion and facilitate 
observation. When it is desired to move the geometrical test pattern, the 
pattern moving mode is selected by operating the push button B and a 
direction of movement is selected by operating the push button C. Then, 
the geometrical test pattern starts moving. The push button D is operated 
to stop the moving geometrical test pattern. A moving speed is selected by 
operating the push button B. The moving speed can be changed by operating 
the push buttons C and D. 
Then, the respective positions of the far viewing section and the near 
viewing section of the progressive multifocal lens through the observation 
of the distribution of refractive power of the lens and the positions of 
the far viewing section and the near viewing section are indicated with 
marks. When the lens is a lens for astigmatic correction, the direction of 
axis is indicated with a mark. If a cross target is used, the angle of the 
axis can be known. 
FIG. 5 shows an automatic lens meter incorporating the refractive 
characteristics measuring functions of the refractive characteristics 
measuring apparatus of FIG. 1. The description of the measurement of the 
refractive power of a lens by the automatic lens meter will be omitted 
because the same is not closely related with the present invention. The to 
"Automatic Lens Meter" proposed in Japanese Patent Laid-open (Kokai) No. 
Sho 60-17335 by the applicant of the present patent application, sets out 
typical details of the optical system and algorithm for the lens 
refractive power measuring apparatus 22 of FIG. 5. 
Referring to FIG. 5, the automatic lens meter has a lens table 20 and a 
display 21. A target mark for use in aligning the optical center of a lens 
with the optical axis of the measuring system and an alignment mark are 
displayed on display 21. Apparatus 22 includes measuring light beam 
projector 23 and apparatus 24, which is an optical detector and refractive 
power calculator. In the operation, apparatus 22 functions as follows. 
Measurement light is projected onto glasses 1 (FIG. 1) by measuring light 
beam projector 23; and the measurement light passed through the glasses 1 
is detected by optical detector and refractive power calculator 24. 
Refractive power is then calculated on the basis of a signal corresponding 
to the detected measurement light. 
In each respective case where, for example, the glasses 1 have (1) only 
spherical refractive power, (2) only cylindrical refractive power, or (3) 
both spherical refractive power and cylindrical refractive power, each 
applicable one of the respective powers and certain other optical 
properties is calculated by a designated operating formula on the basis of 
each position of an optical image indicated by the signal. selected 
geometrical test pattern for the observation of the distribution of 
refractive power according to the present invention is also displayed on 
the display 21. 
When an observation mode for observing of refractive power is selected by 
operating switches in a state after the measurement of the far point of 
the lens by apparatus 22, which can be easily achieved even if the lens is 
held by a rim, the size of the geometrical test pattern and intervals of 
the lines of the geometrical test pattern can be automatically selected. 
The size of the geometrical test pattern and intervals of the lines of the 
geometrical test pattern are selected with reference to the refractive 
power of the far point because additive diopter varies in a relatively 
narrow range. A geometrical test patten optimal for observing the 
distribution of refractive power is selected according to a program on the 
basis of the measured refractive power from a table showing refractive 
powers, and sizes and intervals of lines of geometrical test patterns. 
Since the geometrical test pattern is enlarged by a convex lens, a 
geometrical test pattern consisting of lines arranged at intervals smaller 
than the standard intervals is preferable for testing a convex lens. A 
geometrical test pattern consisting of lines arranged at smaller interval 
is used for a convex lens having a larger diopter and vice versa in 
measuring the refractive characteristics of a concave lens. 
The observation mode for observing the distribution of refractive power may 
be selected automatically subsequent to the operation of a switch for 
storing the diopter of the far point when a progressive multifocal lens 
measuring mode is selected. 
Since a suitable geometrical test pattern among a plurality of geometrical 
test patterns including a pattern of a grid, a pattern of dots, a pattern 
of parallel lines and a pattern of concentric circles is selected by 
operating the pattern selector switch, the geometrical test pattern is 
moved by translation or turning and the distribution of refractive power 
is observed from the geometrical test pattern displayed on the display, 
the position of the near viewing section of a progressive multifocal lens 
and the distribution of refractive power in the progressive multifocal 
lens can be readily determined without requiring much time and the 
direction of axis of a lens for astigmatic correction and a progressive 
multifocal lens for astigmatic correction can be easily determined. Thus, 
the present invention enables the selection of new progressive multifocal 
lenses having, in addition to a suitable additive diopter, a distribution 
of refractive power similar to that of the old progressive multifocal 
lenses of a pair of glasses presently worn by the person and facilitating 
the adaptation of the person's eyes, when changing the progressive 
multifocal lenses of the pair of glasses presently worn by the person.