U.S. patent application number 09/381294 was filed with the patent office on 2001-05-24 for lens specifying device.
Invention is credited to IKEZAWA, YUKIO, KATO, TAKEYUKI, YANAGI, EIICHI.
Application Number | 20010001572 09/381294 |
Document ID | / |
Family ID | 11735473 |
Filed Date | 2001-05-24 |
United States Patent
Application |
20010001572 |
Kind Code |
A1 |
IKEZAWA, YUKIO ; et
al. |
May 24, 2001 |
LENS SPECIFYING DEVICE
Abstract
A lens specifying apparatus comprising a light source (21) for
projecting a measuring light beam on a lens (30) under examination,
an area CCD (35) image receiving element for receiving the
measuring light beam transmitted by the lens (30) under
examination, a filter disc (64) disposed, as means for providing
spectral transmittances, at a midpoint of an optical path extending
from the light source (21) to the area CCD (35), and a processing
circuit (37) for calculating the refractive characteristics and
spectral transmittances of the lens (30) under examination on the
basis of an output of the area CCD (35) and displaying the
refractive characteristics and spectral transmittances on a monitor
(3).
Inventors: |
IKEZAWA, YUKIO; (TOKYO,
JP) ; KATO, TAKEYUKI; (TOKYO, JP) ; YANAGI,
EIICHI; (TOKYO, JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND
MAIER & NEUSTADT
1755 JEFFERSON DAVIS HIGHWAY
FOURTH FLOOR
ARLINGTON
VA
22202
|
Family ID: |
11735473 |
Appl. No.: |
09/381294 |
Filed: |
September 22, 1999 |
PCT Filed: |
January 22, 1999 |
PCT NO: |
PCT/JP99/00224 |
Current U.S.
Class: |
356/124 |
Current CPC
Class: |
G01M 11/0228 20130101;
G01M 11/0235 20130101 |
Class at
Publication: |
356/124 |
International
Class: |
G01B 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 22, 1998 |
JP |
10-09996 |
Claims
1. A lens specifying apparatus including lens measuring means
having a measurement optical system for measuring a refractive
characteristic of a lens under examination, the apparatus
comprising: spectral characteristic measuring means having a part
of an optical path in common with the measurement optical system of
the lens measuring means and measuring a spectral transmittance of
the lens under examination; and display means for displaying the
spectral transmittance of the lens under examination measured by
the spectral characteristic measuring means.
2. The lens specifying apparatus according to claim 1, wherein the
lens measuring means comprises; a light source for projecting a
measuring light beam on the lens under examination; an image
receiving element for receiving the measuring light beam
transmitted by the lens under examination; transmission wavelength
selecting means disposed, as a part of the spectral characteristic
measuring means, at a midpoint of the optical path extending from
the light source to the image receiving element to serve as means
for obtaining the spectral transmittance; and a processing circuit
for obtaining, from an output of the image receiving element, the
refractive characteristic of the lens under examination and the
spectral transmittance thereof.
3. The lens specifying apparatus according to claim 2, wherein the
transmission wavelength selecting means is composed of a rotating
plate provided with a plurality of filter portions for cutting off
light in different wavelength ranges, respectively, one of the
filter portions being inserted in the optical path with the
rotation of the rotating plate.
4. The lens specifying apparatus according to claim 2, wherein-the
transmission wavelength selecting means comprises a rotating plate
provided with an aperture and a filter portion, the filter portion
being provided with a plurality of filters for cutting off light in
different wavelength ranges, respectively, the aperture or filter
portion being selectively inserted in the optical path with the
rotation of the rotating plate.
5. The lens specifying apparatus according to claim 1, wherein the
display means displays, as a bar graph, the spectral transmittance
in each of the wavelength ranges.
6. The lens specifying apparatus according to any one of claims 1
to 4, wherein the display means displays in three dimensions the
spectral transmittance at each site of a lens configuration
representing the lens under examination over the corresponding site
of the lens configuration based on spectral data obtained by moving
the lens under examination in fore-to-aft and side-to-side
directions.
7. The lens specifying apparatus according to claim 1, wherein, if
the upper and lower parts of the lens under examination have
different spectral transmittances, the display means displays the
spectral transmittance of the upper part along with a mark or
character indicative of the upper part and the spectral
transmittance of the lower part along with a mark or character
indicative of the lower part.
8. The lens specifying apparatus according to claim 1, wherein the
spectral transmittance is measured automatically when the lens
under examination- is moved in fore-to-aft and side-to-side
directions and an optical axis of the lens under examination is
located adjacent an optical axis of the measurement optical
system.
9. The lens specifying apparatus according to claim 1, wherein, if
the lens under examination is a multifocal progressive lens, the
spectral transmittance measured in a distance viewing zone and the
spectral transmittance measured in a near viewing zone are
distinguishably displayed by the display means.
10. The lens specifying apparatus according to claim 1, wherein, if
the lens under examination is a multifocal progressive lens, the
lens under examination is moved over a lens receiver to shift an
optical axis of the measurement optical system from a distance
viewing zone of the lens under examination to a near viewing zone
thereof, an add power of a progressive zone of the lens under
examination is calculated and displayed on a display element when
the measurement optical axis enters the progressive zone, and the
spectral transmittance of the near viewing zone is measured when an
add power memory switch is pressed.
11. The lens specifying apparatus according to claim 1, wherein, if
the lens under examination is a multifocal progressive lens, the
lens under examination is moved to shift an optical axis of the
measurement optical system from a distance viewing zone of the lens
under examination to a near viewing zone thereof, an add power of a
progressive zone of the lens under examination is calculated and
displayed on a display element when the measurement optical axis
enters the progressive zone, and the spectral transmittance of the
near viewing zone is automatically measured when the add power
slightly lowers from a maximum value.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lens specifying apparatus
for measuring the spectral transmittances of a lens under
examination and displaying the measured spectral
transmittances.
BACKGROUND ART
[0002] There are various eyeglass lenses including ones of colored
type, anti-surface-reflection type, flaw-free-coating covered type,
and UV (ultraviolet ray) cut-off type which cuts off an ultraviolet
ray harmful to eyes.
[0003] If one of the lenses in the right and left lens frames of
eyeglasses is broken, it is desirable to fit a lens of the same
type as the unbroken lens in one of the lens frames.
[0004] However, it was difficult to know the characteristics of the
unbroken lens, i.e., the spectral transmittances thereof at a mere
sight of the unbroken lens.
[0005] It is therefore an object of the present invention to
provide a lens specifying apparatus capable of easily and promptly
measuring the spectral transmittances of a lens.
DISCLOSURE OF THE INVENTION
[0006] To attain the object, the present invention provides as
defined in claim 1 an apparatus including lens measuring means
having a measurement optical system for measuring a refractive
characteristic of a lens under examination, the apparatus
comprising: spectral characteristic measuring means having apart of
an optical path in common with the measurement optical system of
the lens measuring means and measuring a spectral transmittance of
the lens under examination; and
[0007] display means for displaying the spectral transmittance of
the lens under examination measured by the spectral characteristic
measuring means.
OPERATION
[0008] With the above mentioned arrangement, the present invention
as defined in claim 1 enables the spectral transmittances of a lens
under examination to be measured easily and promptly by utilizing
the optical path of the measurement optical system of the lens.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is an explanatory view illustrating a lens meter as a
lens specifying apparatus according to the present invention;
[0010] FIG. 2 is a partially enlarged view illustrating the lens
meter shown in FIG. 1 when it is used;
[0011] FIG. 3 is an explanatory view showing the optical system of
the lens meter shown in FIG. 1;
[0012] FIG. 4 is an explanatory view illustrating the filter plate
of FIG. 3;
[0013] FIG. 5 is an explanatory view showing an example of display
of a refractive characteristic image and spectral transmittances on
a display device;
[0014] FIG. 6 is an explanatory view showing another example of
display of the spectral transmittances;
[0015] FIG. 7(a) is a partial explanatory view showing the optical
system having another filter disc,
[0016] FIG. 7(b) is an explanatory view illustrating the filter
disc of FIG. 7(a),
[0017] FIG. 7(c) is a partial explanatory view showing the optical
system having another filter disc, and
[0018] FIG. 7(b) is a view illustrating the filter plate of FIG.
7(a);
[0019] FIG. 8 is an enlarged explanatory view illustrating the
principal portion of FIG. 7;
[0020] FIG. 9 is an explanatory view illustrating a pattern
projected on an area CCD by the filter plate of FIGS. 7 and 8;
[0021] FIGS. 10 is an explanatory view showing a spectral
transmittance based on an output of the CCD of FIG. 9;
[0022] FIG. 11 is an explanatory view showing another example of
the lens meter as the lens specifying apparatus according to the
present invention;
[0023] FIG. 12(a) is an explanatory view illustrating a pattern for
measuring optical characteristics of FIG. 11 and FIG. 12(b) is an
explanatory view illustrating the filter plate for measuring the
spectral characteristics of FIG. 11;
[0024] FIG. 13 is an explanatory view showing the effect of the
optical system shown in FIG. 11;
[0025] FIG. 14 is an explanatory view showing the relationship
between the pattern for optical characteristics shown in FIG. 11
and the area CCD;
[0026] FIG. 15 is an explanatory view showing an example of display
of the spectral characteristics;
[0027] FIG. 16 is an explanatory view showing another example of
display of the spectral characteristics;
[0028] FIG. 17 is an explanatory view showing still another example
of display of the spectral characteristics;
[0029] FIG. 18(a) is an explanatory view showing the placement of
an optical system according to a third embodiment and FIG. 18(b) is
an explanatory view showing the case where a lens to be examined is
placed at a placement position;
[0030] FIG. 19 is a perspective view showing the outward appearance
of a lens meter according to a fourth embodiment;
[0031] FIG. 20 is an explanatory view showing the placement of the
optical system of the lens meter according to the fourth
embodiment;
[0032] FIG. 21 is an explanatory view showing scales each
representing the value of prism in the lens under examination over
concentric circles and a mark indicative of the position of the
axis of measuring light;
[0033] FIG. 22 is a block diagram showing the structure of a
control system for moving a target;
[0034] FIG. 23 is an explanatory view showing an example of display
on a monitor screen;
[0035] FIG. 24(A) is an explanatory view illustrating the
disposition of an optical system in another example of the fourth
embodiment, FIG. 24(B) is an explanatory view illustrating a
four-hole target plate, and FIG. 24(C) is an explanatory view
illustrating a filter plate;
[0036] FIG. 25(A) is an explanatory view showing the placement of
an optical system in still another example of the fourth embodiment
and FIG. 25((B) is an explanatory view illustrating a rotating
plate;
[0037] FIG. 26 is a perspective view showing the outward appearance
of a lens meter according to a fifth embodiment;
[0038] FIG. 27 is an explanatory view showing an aiming light beam
being projected on a lens under examination;
[0039] FIG. 28 is an explanatory view showing concentric scales
around the optical center of the lens under examination and a mark
showing the position of the axis of measuring light;
[0040] FIG. 29 is an explanatory view showing the mark being
coincident with the scale at the center portion; and
[0041] FIG. 30 is an explanatory view showing an example of display
on the monitor screen.
BEST MODES FOR IMPLEMENTING THE INVENTION
[0042] Referring now to the drawings, the embodiments of a lens
specifying apparatus in accordance with the present invention will
be described.
First Embodiment
[0043] In FIG. 1, 1 is a lens meter as the lens specifying
apparatus, 2 is a main body of the lens meter 1; 3 is a monitor
(display means) such as a CRT or a liquid crystal display provided
in the upper part of the main body 2; 3a is a display screen
(display element) of the monitor 3; 4 is an upper optical component
container provided on the front side of the main body 2; 5 is a
lower optical component container located under the upper optical
component container; 6 is a lens receiving table provided on the
upper end of the lower optical component container 5; 7 is a lens
rest located between the two containers 5, 6 and held on the front
side of the main body 2 to have its fore-and-aft position
adjustable; and 8 is a lever for operating the lens rest which is
held on the side of the main body 2 pivotably in the fore-and-aft
direction The fore-and-aft position of the lens rest 7 is
adjustable by pivoting the lever 8 in the fore-and-aft
direction.
[0044] A slider 9a is held movable in the side-to-side direction
along the upper edge of the lens rest 7. A nose pad support member
9 is held vertically pivotable by the slider 9a. The nose pad
support member 9 is upwardly biased with a spring not shown and has
its upward rotation at a horizontal position regulated. In the case
of measuring the refraction characteristic values of a lens SL (30)
of eyeglasses M under examination by using the nose pad support
member 9, the nose pad B of the eyeglasses M is pressed onto the
nose pad support member 9 from above and the nose pad support
member 9 is rotated downward, while moved laterally, such that the
lens SL (30) under examination is brought into contact with a lens
receiver 13 which will be described later, It is to be noted that
10 is a button (switch) for a menu for switching modes or the
like.
[0045] A stepped mounting hole 12 shown in FIG. 3 is formed in the
lens receiving table 6 such that the lens receiver 13 is provided
in the mounting hole 12. A circular unmachined lens (raw material
lens), a machined lens, or an eyeglass lens in an eyeglass frame is
set as the lens 30 to be examined in the lens receiver 13.
[0046] A measurement optical system shown in FIG. 3 is provided as
lens measuring means in the main body 2. The measurement optical
system has a light source portion 20 as an illumination optical
system and a light receiving optical system.
[0047] The light source portion 20 as the illumination optical
system has; a light source 21 for generating a measuring luminous
flux; a pin-hole plate 22; a filter disc (rotating plate) 60 as
means for measuring spectral transmittances (transmission
wavelength selecting means); a bored mirror 25; and a collimate
lens 26 in this order. The light source portion 20 has: a light
source 23 for generating a luminous flux for determining a center
position (luminous flux for specifying a position); a pinhole plate
24; an aperture 25a in the bored mirror 25; and the collimate lens
26. Besides, 22a, 24a denote pinholes and 27 denotes a concave
mirror for light convergence. The filter disc 60 may also be
disposed anterior to the collimate lens 26.
[0048] The light receiving optical system has: the lens receiver
13; a screen 32; a mirror 33; and a television camera 36. The lens
receiver 13 consists of a pattern plate 28 that is set inthe
stepped mounting hole 12 of the lens receiving table 6 and a lens
receiving pin 29 provided at the center of the pattern plate 28 to
protrude therefrom.
[0049] The pattern plate 28 is formed with approximately 1000
(numerous) small holes (not shown) for use in measuring a
refractive distribution to produce mapping for refractive
characteristics. The television camera 36 has an image forming lens
34 and an area CCD (image pickup means) 35 as an image receiving
element (light receiving element).
[0050] As shown in FIG. 4, the filter disc 60 described above is
provided with a filter portion 61 which transmits ultraviolet light
UVB at wavelengths of 280 to 315 nm and cuts off light at the other
wavelengths, a filter portion 62 which transmits ultraviolet light
UVA at wavelengths of 315 to 380 nm and cuts off light at the other
wavelengths, a filter portion 63 for measuring the spectral
transmittance of visible light in the range of 380 to 800 nm, and a
transparent hole 60a. The filter portion 63 is further provided
with filter portions 63a to 63n capable of selecting stepwise
transmission wavelengths between 380 to 800 nm. Such a filter disc
60 is rotatively driven by a drive motor (driving means) 65 such as
a pulse motor. Any one of the filter portions 61, 62, and 63a to
63n and the transparent hole (aperture) 60a is inserted in an
optical path to be disposed in opposing relation to the pinhole 22.
Although it is any one of the filter portions 61, 62, and 63a to
63n and the transparent hole 60a that is thus disposed in opposing
relation to the pinhole 22a, FIG. 3 shows reference numerals 61,
62, and 63a to 63n when the filter portion is disposed in opposing
relation to the pinhole 22 for the convenience of description.
[0051] If the transparent hole 60a is inserted in the optical path
and disposed in opposing relation to the pinhole 22, the
measurement optical system functions as lens measuring means (lens
refractive characteristic measuring means) for measuring the
refractive characteristics of a lens under examination, In short,
the lens measuring means for measuring the refractive
characteristics is a measurement optical system in the absence of
the filter portions 61, 62, and 63a to 63n on the optical path.
[0052] When one of the filter portions 61, 62, and 63a to 63n is
inserted in the optical path and disposed in opposing relation to
the pinhole 22, the measurement optical system functions as
spectral characteristic measuring means (spectral transmittance
measuring means) for measuring the spectral transmittances
(spectral characteristics) of a lens under examination.
Specifically, the spectral characteristic measuring means for
measuring spectral transmittances has one of the filter portions
61, 62, and 63a to 63n inserted in the optical path such that one
of the filter portions 61, 62, and 63a to 63n forms a part of the
optical path of the measurement optical system, Consequently, the
measurement optical system of the lens measuring means for
measuring a refractive characteristic and the optical path have a
part in common.
[0053] Moreover, the optical source 21 described above is composed
of a halogen lamp which emits light at wavelengths between the UV
and IR regions inclusive. The light source 23 is composed of an
LED. In the normal measurement of the refractive characteristic,
the transparent hole 60a of the filter disc 60 is disposed in the
optical path and a measuring luminous flux at all wavelengths is
projected from the light source 21 onto the lens under
examination.
[0054] The aperture 25a is formed in the bored mirror 25. The
pinhole plates 22, 24 are located at the focal point of the
collimate lens 26 which serves to convert the luminous flux emitted
from the light sources 21, 23 to a parallel luminous flux. Here,
the luminous flux generated from the light source 21 is designated
at a reference numeral P2 and the luminous flux generated from the
light source 23 is designated at a reference numeral P1.
Effects of First Embodiment
[0055] A description will be given below to the effects of a lens
meter with such a structure.
[0056] (i) Measurement and Mapping of Refractive Characteristic
[0057] As described above, the measurement optical system functions
as the lens measuring means (lens refractive characteristic
measuring means) for measuring the refractive characteristic of a
lens under examination by inserting the transparent hole 60a in the
optical path and disposing the transparent hole 60a in opposing
relation to the pinhole 22 through rotative driving by the drive
motor (driving means) 65 such as a pulse motor.
[0058] In this state, the light source 21 is turned on so that the
luminous flux from the light source 21 is projected on the lens 30
under examination on the lens receiver 13 via the pinhole 22a of
the pinhole plate 22, the mirror 25, and the collimate lens 26. The
luminous flux transmitted by the lens 30 under examination is
projected on the screen 32 through the small holes of the pattern
plate 28. At this time, the luminous flux that has passed through
the numerous small holes of the pattern plate 28, which are not
shown, is projected on a screen 3 with a spacing varied in
accordance with the refractive force of the lens 30 under
examination.
[0059] The pattern of the small holes projected on the screen 32 is
formed into an image at the area CCD 35 of the CCD camera 36 via
the mirror 33 and the image forming lens 34. By a processing
circuit 37 a mapping process is carried out based on an output of
the area CCD 35, whereby the refractive characteristic, such as
spherical frequency distribution or cylindrical frequency
distribution, of the lens 30 under examination can be mapped. As
shown in FIG. 1 or 5, the mapping allows a distance viewing zone
91, a progressive zone 92, a near viewing zone 93, a distorted
region 94, and a boundary line 95 to be displayed in a lens
configuration 90 on the monitor 3 Since a well-known technique is
used in this structure for mapping, the detailed description
thereof will be omitted.
[0060] (ii) Measurement of Spectral Transmittances
[0061] To measure the spectral transmittances of the lens under
examination by using the foregoing structure, the filter disc 60 is
pivoted by controlling the operation of the drive motor 65 using
the processing circuit 37 such that the filter portions 61, 62, and
63a to 63n of the filter disc 60 are disposed successively in the
optical path. On the other hand, the light source 21 which is the
halogen lamp for emitting light including rays between the UV area
and IR area is turned on such that measuring light beams at
gradually increasing wavelengths of 280 to 315 nm, 315 to 380 nm,
and 380 to 800 nm of the measuring light beam emitted from the
light source 21 are sequentially selectively transmitted by the
respective filter portions 61, 62, and 63a to 63n of the filter
disc 60 and projected on the lens under examination.
[0062] By the projection, the light beams at gradually increasing
wavelengths of 280 to 315 nm, 315 to 380 nm, and 380 to 800 nm are
selectively transmitted by the lens under examination and projected
on the area CCD 35. Accordingly, the quantity of light transmitted
by the lens under examination when the filter portions 61, 62, and
63a to 63n are not used is measured on the basis of an output
signal from the area CCD 35 by using measuring light at all
wavelengths from the light source 21 to previously obtain an
all-wavelength transmitted light quantity for the lens under
examination, while the respective quantities of measuring light
beams at individual wavelengths which have reached the area CCD 35
are measured on the basis of an output signal from the area CCD 35
to obtain wavelength-by-wavelength transmitted light quantities for
the lens under examination. The rates of the
wavelength-by-wavelength transmitted light quantities to the
all-wavelength transmitted light quantity are calculated and the
resulted rates are displayed as a percentage at the UVB, UVA, and
visible portions of the screen 3a, as shown in FIG. 5. In the case
of visible light, the mean value of the transmittances of the lens
under examination at individual wavelengths is displayed. It is
also possible to show the spectral transmittances at individual
wavelengths as a bar graph, as shown in FIG. 6.
[0063] Since a large number of dot images projected on the area CCD
35 are increased or reduced in size depending on the refractive
index of the lens under examination, when the quantity of light is
measured to obtain the spectral transmittances, the absolute
quantity of light of the light dot images projected on the area CCD
35 is measured and compared with the quantity of light when it is
not transmitted by the lens under examination. In this case, since
the dot images are increased or reduced in size depending on the
power of the lens under examination, it is necessary to perform
integration or make a correction depending on the power.
[0064] By thus obtaining and displaying the spectral
transmittances, it is possible to know, whether or not the broken
lens is, e.g., a UV (ultraviolet ray) cut-off lens, i.e., a lens
with a UV-reflection coating having a spectral transmittance of a
certain percentage, the percentage of the spectral transmittance of
visible light attributable to the coating. By thus knowing the
light transmittance of the lens attributable to the coating on a
wavelength-by-wavelength basis, the adoption of a lens with a
coating having a spectral transmittance of the same percentage can
easily be determined in prescribing the other lens. As a result,
even when one of the right and left eyeglass lenses is broken and
the other lens is also to be replaced, the powers of the right and
left lenses can be best balanced through comprehensive
determination including not only the determination of the
configuration of the progressive zone of a progressive lens but
also the determination of the spectral transmittances as lens data.
Even when the upper and lower parts of an eyeglass lens have
different spectral transmittances, the upper and lower spectral
transmittances can be measured simultaneously for easy
determination.
[0065] Although the foregoing embodiment has measured the spectral
transmittances in the visible wavelength range by sequentially
selecting the filter portions 63a to 63n provided in the filter
disc 60, the present invention is not limited thereto. For example,
it is also possible to divide wavelengths of 280 to 800 nm between
the UV and visible regions inclusive into four wavelength ranges
and provide the filter disc 60 with a filter portion 64 for
transmitting light in the four wavelength ranges as transmission
wavelength selecting means, as shown in FIG. 7(b). In this case,
the filter portion 64 has four filter portions (filters) 64a, 64b,
64c, and 64d capable of transmitting light in the four wavelength
ranges and a light blocking region 64e for blocking light, as shown
in FIG. 8. Moreover, each filter portion 64 is provided with a lens
70 as shown in FIG. 7(a) so that the lens 70 renders the filter
portion 64 conjugate with a diffusion plate 32.
[0066] In obtaining the spectral transmittances by using the filter
portion 64, a set of light dot images 64a' to 64d' regulated by the
filter portions 64a to 64d are projected on the area CCD 35, as
shown in FIG. 9, From the set of light dot images 64a' to 64d', the
spectral transmittances can be obtained simultaneously, as
indicated by 64a" to 64d" in FIG. 10. It is to be noted that the
spectral transmittances 64a" to 64d" correspond to the set of light
dot images 64a' to 64d', respectively.
[0067] Although the filter disc 60 is provided with the filter
portion 64 such that the filter portion 64 is inserted in and
removed from the optical path by rotating the filter disc 60 by
means of the drive motor 65 in the embodiment of FIGS. 7(a) and
7(b), the present invention is not limited thereto. For example, it
is also possible to insert and remove a filter plate 71 provided
with the filter portion 64 in and from the optical path by means of
a solenoid 72, as shown in FIGS. 7(c) and 7(d).
[0068] According to this embodiment, since the spectral
transmittances of the lens 30 under examination are obtained by
measurement by commonly using the optical path of the measurement
optical system, the lens 30 under examination need not be placed
again on another member for the measurement of the spectral
transmittances. As a result, switching between the measurement of
the refractive characteristics of the lens 30 under examination and
the measurement of the spectral transmittances thereof can be
performed instantaneously, resulting in easier measurement.
Moreover, since the area CCD 35 is also used commonly, smaller size
and light weight are achievable.
[0069] In measuring the spectral transmittances, if dots are
printed by using a dot printer not shown, the sites at which the
spectral transmittances were measured can be recognized. It is also
possible to store prism values in the X and Y directions at the
sites at which the spectral transmittances were measured such that
the sites can be specified.
Second Embodiment
[0070] In FIG. 11, 40 is an LED, 41 is a diffusion plate, and 42 is
a pinhole. The LED 40, the diffusion plate 41, and the pinhole 42
constitute a light source portion for generating a measuring
luminous flux. The pinhole 42 functions as a diffusive secondary
point light source.
[0071] The luminous flux emitted from the pinhole 42 is converted
into a parallel luminous flux by a collimate lens 44 provided in a
projection light path 43. The projection light path 43 is provided
with a lens receiver 45 in which a lens 47 to be examined is set.
Although the lens receiver 45 has a diameter of about 8.phi. (mm)
when the lens 47 to be examined is an eyeglass lens, it is replaced
with a lens receiver 45 with a diameter of about 5.phi. (mm) when a
contact lens is set as the lens 47 to be examined.
[0072] As shown in FIG. 12(a), a pattern 48 for the measurement of
optical characteristics having four apertures 48a is provided
posterior to the lens receiver 45. The number of the apertures 48a
may be at least three or more, since the optical characteristic
values can be calculated provided that the number of the apertures
48a is at least three. If the number of apertures 48a is
excessively large, a long period of time is required for
calculation, so that the four apertures 48a are desirable. Here,
each of the apertures 48a has a circular configuration and the four
apertures 48a are located at respective positions which are shifted
by 90 degrees from the adjacent ones and at equal distances L from
a measurement optical axis O. The apertures 48a are preferably
provided at vertically symmetrical positions to allow the
measurement of the lens 47 under examination which is not
rotation-symmetric, such as a progressive lens.
[0073] As shown in FIG. 11, a filter plate (transmission wavelength
selecting means) 80 for measuring spectral characteristics is
provided in a state capable of being inserted and removed between
the lens receiver 45 and the pattern 48 for the measurement of
optical characteristics by means of a solenoid 81. When the filter
plate 80 is disposed between the lens receiver 45 and the pattern
48, the filter plate 80 is in close proximity to the pattern
(pattern plate) 48 so that the filter plate 80 and the pattern 48
are in general conjugation with the pinhole 42. In addition, the
pattern plate 80 is provided with four filter portions 80a, 80b,
80c, and 80d which transmit light beams in four wavelength ranges
into which wavelengths of 280 to 800 nm between the UV and visible
regions inclusive are divided, as shown in FIG. 12(b). The filter
portion 80a transmits light in the wavelength range of 280 to 315
nm. The filter portion 80b transmits light in the wavelength range
of 315 to 380 nm. The filter portion 80c transmits light in the
wavelength range of 380 to 540 nm. The filter portion 80d transmits
light in the wavelength range of 540 to 800 nm.
[0074] A converging lens 49 is disposed in each of the apertures
48a. The size of the aperture 48a is preferably maximized to
ultimately approximate the values obtained by measuring the optical
characteristics by using an automatic lens meter to the values
obtained by measuring the optical characteristics by using a manual
lens meter. In the case where the lens 47 to be examined is a
contact lens, the size of the circumcircle of the four apertures
18a should be 5 mm or less since the aperture of the lens receiver
45 is about 5.phi. in size If the size of the aperture 48a is
excessively large, the respective centers of gravity of the light
dot images cannot be calculated in measuring the lens 47 under
examination with a positive strong power since the individual light
dot images are in intimate contact with each other. On the other
hand, measurement sensitivity is degraded if the distance 1 between
the measurement optical axis O and the center position O1 of the
aperture 48a is small. Conversely, if the distance 1 is excessively
large, the light dot images extend off the effective area of a
two-dimensional light receiving sensor, which will be described
later, in the case where the lens 47 under examination has a
negative strong power. Therefore, the distance 1 between the
measurement optical axis O and the center position O1 is preferably
on the order of 1 mm and the size of the aperture 48a is preferably
on the order of 1.phi..
[0075] As the pattern plate 48 for the measurement of optical
characteristics, there may be used, e.g., a glass plate in a gold
frame to which a microlens may be secured. Alternatively, there may
also be used a mold lens composed of four converging lenses 49
molded in a single resin or glass plate or a converging lens 49,
utilizing the phenomenon of diffraction, which is formed in a glass
plate by etching. Preferably, the portion other than the converging
lens 49 is shielded by using a substance such as chromium.
[0076] An area CCD 50 as the two-dimensional image receiving
element is provided posterior to the pattern 48 for the measurement
of optical characteristics. The distance Z from the area CCD 50 to
the lens receiver, i.e., the distance Z from the two-dimensional
image receiving element 50 to the back-side vertex position 47a of
the lens 47 under examination has been adjusted to be smaller than
the back focus distance Z1 obtainable when a lens 47 under
examination having the measurable strongest positive power is set
in the projection optical path 43. This is for preventing the light
dot images from overlapping each other or for preventing the
measuring luminous flux transmitted by the lens 47 under
examination from being inverted.
[0077] Specifically, if the area CCD 50 is provided at the position
indicated by the broken line in FIG. 13, a measuring luminous flux,
P1 that has passed through the region overlying the lens 47 under
examination is formed into an image in the region underlying the
area CCD 50 and the measuring luminous flux P2 that has passed
through the underlying region is formed into an image in the region
overlying the area CCD 50, so that the measuring luminous flux P
incurs inversion. Consequently, it becomes impossible to judge to
which light dot image on the area CCD 50 the measuring luminous
flux P corresponds in passing through the lens 17 under
examination.
[0078] If the lens 47 under examination which is measurable by
means of the automatic lens meter has a measured power of, e.g.,
.+-.25 diopters, the back focus distance Z1 is 40 mm, so that the
distance Z from the lens receiver 45 to the area CCD 50 is
preferably 20 to 30 mm. If the distance Z is set to 20 mm or less,
the measurement sensitivity is degraded. However, this is not the
case if a relay lens is provided between the lens receiver 45 and
the area CCD 40.
[0079] If a lens 47 with high measurement frequency, e.g., a lens
47 with a low power (-2.5 D) is set in the projection optical path
43, e.g., settings are preferably made such that the light dot
images on the area CCD 50 are minimized in size to render the
measurement less susceptible to flaws and contamination.
[0080] A measuring luminous flux n incident upon the lens 47 under
examination is polarized after passing through the lens 47 under
examination. The degree of polarization is determined by the height
h of incidence and the power of the lens 47 under examination at
the position of incidence. If the angle of polarization is assumed
to be .theta., S=tan .theta./10h is satisfied where the height h of
incidence is already known. As shown in FIG. 14, if the height from
the center line O' on the area CCD 20 is assumed to be hi,
.theta.=(h-hi/Z) is satisfied so that the power S of the lens 17
under examination is calculated if the center positions G1 to G4 of
gravity are obtainable.
[0081] When the lens 47 under examination has a positive power, the
spaces between the individual light dot images PM1 to PM4 is
reduced. If the lens 47 under examination has a negative power, the
spaces between the light dot images PM1 to PM4 are increased, If
the lens 47 under examination is a spherical lens, the respective
center positions G0 of the light dot images PM1 to PM4 are
generally equidistant from the center line O'. If the lens 47 under
examination is distorted, however, the distances from the
respective center positions G0 of the individual light dot images
PM1 to PM4 to the center line O' are different from each other.
[0082] In accordance with the present invention, since each of the
apertures 48a has been formed to have a maximum size, numerous fine
light beams pass through the individual apertures 48a on a
one-by-one basis under the influence of aberration of the lens 47
under examination. As a result, each of the center positions G1 to
G4 of gravity of the light dot images PM1 to PM4 in the individual
apertures 48a is shifted from the center position (center position
of gravity) G0 based on one fine light beam when they are formed on
the area CCD 20. Accordingly, the obtained power is approximate the
power obtainable with the manual lens meter.
[0083] Even if a small flaw or slight contamination is present in
the local region of the lens 47 under examination through which the
measuring luminous flux directed to the apertures 48a passes and
the measuring luminous flux directed to the apertures 48a is
thereby partially blocked, the degree of blocking is lower than in
the case with a fine light beam. As a result, the light dot images
PM1 to PM4 are shifted from the center positions G1 to G4 of
gravity only slightly, so that a measurement error resulting from
dust and contamination is small and measurement accuracy is
improved.
[0084] In measuring the spectral characteristics of the lens 47
under examination, the solenoid 81 is actuated to insert the filter
plate 80 for the measurement of spectral characteristics between
the lens receiver 45 and the pattern 48 so that light dot images
PM1 to PM4 as shown in FIG. 14 are formed on the area CCD 50.
Output signals from pixels at the respective locations of the light
dot images PM1 to PM4 are inputted to a calculation control circuit
(processing circuit) 90. The calculation control circuit 90
calculates the spectral transmittances of the lens 47 under
examination on the basis of the magnitudes of the output signals
from the pixels at the locations of the light dot images PM1 to PM4
and displays the result of calculation on the display screen 3a of
the display device 3, as shown in FIG. 10.
Other Features
[0085] It is also possible to measure spectral data when the lens
under examination is moved continuously in the fore-to-aft and
side-to-side directions and display the measured spectral data in a
two-dimensional map representation. Alternatively, it is also
possible to display in three dimensions a plurality of bars 96 with
heights each indicative of a light transmittance in overlapping
relation with the lens configuration 90, as shown in FIG. 15.
[0086] FIG. 16 shows the case where the spectral transmittances of
an eyeglass lens entirely covered with a coating for cutting off an
ultraviolet ray UVA at wavelengths of 280 to 315 nm and an
ultraviolet ray UVB at wavelengths of 315 to 380 nm and having an
upper half portion colored in gray or brown for cutting off visible
light are measured and displayed. In FIG, 16, the respective
transmittances of UVA and UVB and the transmittances of visible
light of the colored portion 97 are displayed laterally to the lens
configuration 90, while the colored portion 97 is indicated by the
broken lines. In the present embodiment, the transmittances can be
determined based on the values measured in the plurality of regions
and the regions in which the measured values are less than a
specified value can be displayed, For example, the respective
transmittances of UVA and UVB are less than 5% and the colored
portion 97 with a visible light transmittance of 70% is displayed.
Since a gray scale which progressively becomes thinner downwardly
is normally provided on the boundary between the upper-half colored
portion 97 and the lower-half uncolored portion, the degree of
variations in transmittance can also be displayed as a portion with
a color variation or with a gray-scale variation.
[0087] In the case of refilling a lens in eyeglasses in place of a
broken lens, the spectral transmittances of the unbroken lens are
measured and the spectral transmittances of a sample lens (or
unmachined lens) selected based on the measurement are measured so
that the respective spectral transmittances of the unbroken lens
and the sample lens (or unmachined lens) are displayed
simultaneously on the righthand and lefthand sides, as shown in
FIG. 17, whereby a comparison is made between the spectral
transmittances of the unbroken lens and the lens selected as a
refill on a wavelength-by-wavelength basis (i.e., a comparison is
made between color tones determined by the spectral transmittances
at the individual wavelengths) to determine whether the selected
lens is the same as or approximate to the unbroken lens. In this
case, if the spectral transmittances of the selected one are
superior, an emphasis can be placed on the superiority of the
selected lens.
[0088] In this case, first and second memories M1 and M2 indicated
by the broken lines in FIG. 3 are provided such that the spectral
transmittances of the unbroken lens are stored in the first memory
M1 and the spectral transmittances of the selected sample lens (or
unmachined lens) are stored in the second memory M2. The processing
circuit 37 is caused to compare the respective spectral
transmittances stored in the first and second memories M1 and M2
with each other to display the result of comparison on the display
screen 3a, as shown in FIG. 17. In addition, the unbroken "eyeglass
lens", "R" indicative of the righthand lens or "L" indicative of
the lefthand lens, and the "sample lens" or "unmachined lens" are
also displayed.
[0089] This enables a customer when he or she orders the dyeing of
a plastic lens to an eyeglass shop to check the difference between
the plastic lens actually dyed and the plastic lens as a sample
observed at the eyeglass shop.
[0090] In the case of providing a potentiometer which operates in
association with the nose pad support member 9, as shown in FIG. 1,
to detect from an output of the potentiometer whether the spectral
transmittances under measurement are those of the lefthand lens or
of the righthand lens, storing means for storing whether the
spectral transmittances under measurement are those of the lefthand
lens or of the righthand lens in conjunction with the measured
spectral transmittances (spectral characteristics) may be provided
appropriately. In this case, if one of eyeglass lenses is replaced
and the spectral transmittances of a refilled lens are not the same
as those of the remaining lens, the difference between the
respective spectral transmittances of the right and left eyeglass
lenses can be recognized.
[0091] In the case of examining a contact lens, especially a soft
contact lens, the lens with-high oxygen permeability is easily
contaminated and therefore must be sterilization-boiled, If such a
contact lens tarnishes considerably, it should be replaced.
However, it is difficult to visually estimate the degree of tarnish
of the contact lens. Since the degree of tarnish of the contact
lens can be determined precisely by measuring the spectral
transmittances (spectral characteristics) as described above, it
can easily be determined whether or not it is time to replace the
contact lens by measuring the spectral transmittances of the
contact lens. It is also possible to set, for each eyeglass shop, a
value (border line) based on which it is determined whether or not
the contact lens should be replaced when the spectral transmittance
reaches a certain level as the contact lens tarnishes
increasingly.
[0092] Moreover, since the filter for measuring the dispersive
transmittances is provided in a state capable of being inserted and
removed at a midpoint of the optical path of the optical system of
an existing lens meter such that the refractive characteristics of
the lens under examination are measurable when the filter is
removed from the optical path and that the dispersive
transmittances of the lens under examination are measurable by
inserting the filter in the optical path, as described above, it is
unnecessary to replace the lens under examination which has been
placed on the lens receiver 13 on another member for the
measurement of dispersive transmittances. As a result, the
measurements can be performed easily through instantaneous
switching between the measurement of the refractive characteristics
of the lens under examination and the measurement of the dispersive
transmittances thereof, In measuring the refractive characteristics
of the lens under examination at the different sites thereof and
displaying the measured refractive characteristics in a mapping
representation, it is also possible to display the dispersive
transmittances at the individual sites of the lens under
examination in precise overlapping relation with the mapping
representation.
Third Embodiment
[0093] In a third embodiment shown in FIG. 18, the spectral
transmittances can be measured by means of a normal lens meter, In
FIG. 18, 101A are four LEDs as a projection light source for
projecting a measuring luminous flux, which are disposed around the
optical axis, 101B is a projection lens, 101F is a measurement
target which is movable along the optical axis, 101C is a relay
lens, 101D is a light receiving lens, and 101E is an area sensor
composed of a CCD or the like.
[0094] The plane 101G on which the LEDs 101A are disposed and the
position 101H at which the lens 30 to be examined is disposed are
conjugate with each other relative to the projection lens 101B and
the relay lens 101C. On the other hand, the measurement target 101F
and the area sensor 101E are conjugate with each other relative to
the relay lens 101C and the light receiving lens 101D when the lens
30 to be examined is not disposed at the placement position 101H,
so that the measuring luminous flux passing through the hole
(pinhole) of the measurement target 101F is converged to a point on
the light receiving surface of the area sensor 101E.
[0095] Posterior to 101A, there are disposed a collimate lens 103
and a light source 104 composed of a halogen lamp or the like via a
mirror 102 in this order so that the light source 104 and the plane
101G are conjugate with each other relative to the collimate lens
103. 60 is a filter disc as shown in FIG. 4 which is disposed
between the projection lens 101B and the measurement target
101F.
[0096] To measure the lens characteristic of the lens 30 under
examination, the lens 30 to be examined is initially set at the
placement position 101H, as shown in FIG. 18(b). Then, the filter
disc 60 is rotated to insert the transparent hole 60a in the
optical path and the LEDs 101A are caused to emit light to project
the measuring luminous flux on the lens 30 under examination. The
lens 30 under examination disturbs the conjugate relationship
between the measurement target 101F and the light receiving lens
101D and the measuring luminous flux passing through the hole of
the measurement target 101F is no more converged to a point on the
light receiving surface of the area sensor 101E.
[0097] The measurement target 101F is moved along the optical axis
such that the measuring luminous flux passing through the hole of
the measurement target 101F is converged to a point on the light
receiving surface of the area sensor 101E, The amount .DELTA.t of
travel of the measurement target 101F is calculated when the
measuring luminous flux is converged to a point on the light
receiving surface of the area sensor 101E, i.e., when the conjugate
relationship is established between the measurement target 101F and
the light receiving lens 101D and the refractive characteristics of
the lens 30 under examination are calculated based on the amount
.DELTA.t of travel.
[0098] Next, the emission of light from the LEDs 101A is halted,
while the light source 104 is caused to emit light, and the
specified one of the filter portions 61, 62, and 63 is inserted in
the optical path by rotating the filter disc 60 The quantity of
light received by the area sensor 101E when the specified filter
portion 61, 62, and 63 is inserted in the optical path is measured
and the spectral transmittance is calculated from the measured
quantity of light. The spectral transmittances and the refractive
characteristics are calculated by a processing circuit 37 composed
of a CPU or the like, similarly to that shown in FIG. 3.
[0099] In calculating the spectral transmittances, the quantity of
received light is preliminarily calculated when the specified
filter portion 61, 62, and 63 is inserted in the optical path
before the lens 30 to be examined is disposed at the placement
position 101. In this case, it may also be constructed such that,
when a calibration switch (not shown) is pressed, the filter disc
60 is rotated to insert the specified filter portion 61, 62, and 63
in the optical path, the quantity of received light when the lens
30 to be examined is not set at the placement position 101H is
measured, and the spectral transmittance at this time automatically
becomes 100%.
[0100] In the third embodiment also, the lens 30 under examination
need not be placed again on another member since the spectral
transmittances can be measured at the position at which the
refractive characteristics were measured.
Fourth Embodiment
[0101] FIG. 19 shows a lens meter (lens specifying apparatus) 150
according to a fourth embodiment.
[0102] The lens meter 150 has an optical system as shown in FIG.
20. In FIG. 20, 102' is a half mirror, 152 is a light source for
measuring the amount of prism in a lens under examination, and 153
is a pinhole plate.
[0103] As shown in FIG. 21, the lens meter 150 displays concentric
scales K1 to K5 around the optical center of the lens under
examination and a crisscross mark M on the monitor screen 3a. Each
of the scales K1 to K5 represents the amount of prism and the prism
value decreases stepwise toward the center portion of the scales K1
to K5. The crisscross mark represents the position of a measurement
optical axis 101P.
[0104] As shown in FIG. 22, a target 101J shown in FIG. 20 moves
over a guide rail 171 provided along the optical axis, which is
moved by a motor 172. The motor 172 is controlled by a control
processing circuit 180 based on a light receive signal from the
area sensor 101E. The control processing circuit 180 calculates the
optical characteristics of the lens under examination based on the
amount of travel of the target 101J which has been detected by a
potential meter (not shown) provided along the guide rail 171 and
displays the result of calculation, the scales K1 to K5, and the
crisscross mark M on the monitor 3. The potential meter is composed
of, e.g., a sliding resistor and detects the amount of travel based
on the resistance value of the sliding resistor.
[0105] If the lens 130 to be examined, which is a monofocal lens,
is placed on the lens receiver 151 and the measuring luminous flux
is projected on the lens 130 to be examined by turning on the light
source 152, the measuring luminous flux transmitted by the lens 130
under examination is received by the area sensor 101, The amount of
prism at the portion of the lens 130 through which the measuring
luminous flux passes is calculated on the basis of the position on
the area sensor 101E at which light is received. Based on the
amount of prism, the crisscross mark M indicative of the measured
portion of the lens 130 under examination is displayed on the
scales K1 to K5 on the monitor screen 3a.
[0106] The examiner moves the lens 130 under examination over the
lens receiver 151 in the fore-to-aft and side-to-side directions
such that the crisscross mark M falls within the scale K1, while
monitoring the monitor screen 3a.
[0107] When the crisscross mark M falls within the scale K1, the
light source 152 is turned off and the LEDs 101A are caused to emit
light if the prism value falls within the limits of, e.g., .+-.0.5
(=K1) and such a state is maintained for 0.5 seconds or longer. The
target 101J is moved such that the measuring luminous flux from the
LEDs 101A converges to a point on the light receiving surface of
the area sensor 101E. When the measuring luminous flux from the
LEDs 101A converges to a point on the light receiving surface
thereof, the movement of the target 101J is halted, the amount of
travel of the target 101J detected by the potential meter is read,
and the refractive characteristics "S, C, and A" of the lens 130
under examination are calculated, so that the refractive
characteristics "S, C, and A" are displayed on the monitor 3.
[0108] When the refractive characteristics are calculated, the LEDs
101A are turned off, the light source 104 is caused to emit light,
and the filter disk 60 is rotated to insert the specified filter
portion 61, 62, and 63 in the optical path. The spectral
transmittances are calculated based on the quantity of light
received by the area sensor 101E and displayed on the monitor
screen 3a, as shown in FIG. 21.
[0109] In the case of measuring a lens to be examined having an
upper half portion colored in, e.g., gray or brown for cutting off
visible light, a half mode is set and the spectral transmittances
of the upper portion, e.g., is measured preferentially so that the
spectral transmittance of the upper portion and the spectral
transmittance of the lower portion are displayed on the monitor
display element 3a along with the characters of "UPPER SPECTRAL
TRANSMITTANCES" and "LOWER SPECTRAL TRANSMITTANCES," respectively.
Instead of the characters of "UPPER SPECTRAL TRANSMITTANCES" and
"LOWER SPECTRAL TRANSMITTANCES", marks indicative of the upper and
lower spectral transmittances may also be displayed.
[0110] In the case of measuring the add power of a progressive
lens, there is displayed, e.g., "ADD: +3.0" instead of "S, C, A,
and P" displayed on the righthand side of the display element
3a.
OTHER EXAMPLES
[0111] FIG. 24(A) shows an example in which four spectral
transmittances can be measured simultaneously and a four-hole
target plate 181 formed with four holes and a filter plate 182 as
shown in FIG. 24(B) are provided in place of the filter plate 60 As
shown in FIG. 24(C), the filter plate 182 is provided with the
filter portions 64a to 64d shown in FIG. 8. 183 is a half
mirror.
[0112] FIG. 25(A) shows another example in which a rotating plate
187 is provided with a pinhole 188 and a filter plate portion 189
which is provided with the filter portions 64a to 64d, as shown in
FIG. 25(B) The rotating plate 187 moves along a shaft 190 by means
of a motor not shown and rotates with the rotation of the shaft
190. The shaft 190 is rotated by a motor 191.
[0113] In the other example, the target 101F and the filter disc 60
are combined with each other and, when the refractive
characteristics are measured, the pinhole 188 of the rotating plate
187 is inserted in the optical path so that the rotating plate 187
moves along the optical axis. When the spectral transmittances are
measured, the filter plate portion 189 of the rotating plate 187 is
inserted in the optical path.
Fifth Embodiment
[0114] FIG. 26 shows a lens meter 200 according to a fifth
embodiment. The lens meter 200 is provided with: a first mode
switch 201 for setting a refractive characteristic mode (first
mode) in which refractive characteristics are measured; a second
mode switch 202 for setting a spectral measurement mode (second
mode) in which spectral transmittances are measured; and a third
mode switch 203 for setting an optical spectral mode (third mode)
in which the refractive characteristics and spectral transmittances
are measured. The lens meter 200 comprises the same optical system,
the processing circuit 37, and the like as shown in FIG. 3.
[0115] In the first and second modes, the refractive
characteristics and spectral transmittances are measured similarly
to the first embodiment, so that the description thereof will be
omitted.
[0116] When the third mode is set, the lens 30 to be examined is
placed on the lens receiver 13, a light-source lighting switch (not
shown) is turned on, the light source 23 is lit, and the lens 30
under examination is illuminated with an aiming light beam 210 as
shown in FIG. 27, so that the position of the axis of measuring
light is recognizable under the radiation of the aiming light beam
210.
[0117] The lens 30 under examination is moved in the fore-to-aft
and side-to-side directions over the lens receiver 13 such that the
aiming light beam 210 is positioned in the distance viewing zone of
the lens 30 under examination. When the aiming light beam 210 is
positioned in the distance viewing zone of the lens 30 under
examination, as shown in FIG. 27, a measurement initiation switch
not shown is turned on. Then, the transparent hole 60a of the
filter disc 60 is inserted in the optical path and the light source
21 is lit so that the measuring luminous flux P2 (see FIG. 3) is
projected on the lens 30 under examination, while the scales K1 to
K5 are displayed on the monitor screen 3a, as shown in FIG. 21.
[0118] The measuring luminous flux P2 transmitted by the lens 30
under examination reaches the area CCD 35 via the pattern plate 28,
the screen 32, the mirror 33, and the image forming lens 34 and the
images of the small holes of the pattern plate 28 are formed on the
CCD 35. The amount of prism at the portion of the lens 30 through
which the aiming light beam passes is calculated on the basis of
the positions of the images of the small holes on the area CCD 35
and, based on the amount of prism, the crisscross mark M indicative
of the measured portion of the lens 30 under examination is
displayed on the scales K1 to K5 on the monitor screen 3a, as shown
in FIG. 28.
[0119] The examiner moves the lens 30 under examination over the
lens receiver 13 in the fore-to-aft and side-to-side directions
such that the crisscross mark M falls within the scale K1, while
monitoring the monitor screen 3a.
[0120] As shown in FIG. 29, when the crisscross mark M falls within
the scale K1, the optical characteristics "S, C, and A" of the lens
30 under examination at a distance viewing point thereon are
measured and displayed on the monitor screen 3a. When the
measurement of the optical characteristics is completed, the filter
disk 60 is rotated to insert the specified filter portion 61, 62,
or 63 in the optical path and the spectral transmittances at the
distance viewing point are measured so that the spectral
transmittances at the distance viewing point are displayed on the
monitor screen 3a along with the characters of "SPECTRAL
TRANSMITTANCES FOR DISTANCE VISION".
[0121] When the measurement of the spectral transmittances is
completed, the filter disk 60 is rotated to insert again the
transparent hole 60a in the optical path. The lens 30 under
examination is then moved such that the aiming light beam 210 moves
toward a near viewing zone. When the aiming light beam 210 enters a
progressive zone, the add power of the progressive zone is
calculated and the add power is displayed on the monitor screen
3a.
[0122] When the add power becomes maximum, an add power memory
switch (not shown) is pressed so that the add power at this time is
displayed on the monitor screen 3a as the maximum add power. When
the add power memory switch is pressed, the filter disc 60 is
rotated to insert the specified filter portion 61, 62, or 63 in the
optical path and the spectral transmittances at a near viewing
point is measured, so that the spectral transmittances at the near
viewing point are displayed on the monitor screen 3a along with the
characters of "SPECTRAL TRANSMITTANCES FOR NEAR VISION". Instead of
the characters of "SPECTRAL TRANSMITTANCES FOR DISTANCE VISION" and
"SPECTRAL TRANSMITTANCES FOR NEAR VISION", marks indicative thereof
may also be used.
[0123] Although the spectral transmittances are measured when the
add power memory switch is pressed in the fifth embodiment, the
spectral transmittances may also be measured automatically when the
add power lowers from the maximum value by a specified value.
[0124] The aiming light beam 210 can easily be caused to enter the
progressive zone of the lens 30 under examination by displaying an
optical axis mark Ma indicative of the position of the axis of
measurement light on a distribution image Ga displayed on the
display screen 3a of the monitor 3, providing a potentiometer at
the lens pad 7 and the slider 9a so that the amounts of travel of
the lens 30 under examination in the X and Y directions are
detected by means of the potentiometer, shifting the optical axis
mark Ma over the distribution image Ga based on the detected
amounts of travel, and moving the lens 30 under examination while
monitoring the shifting position of the optical axis mark Ma.
Advantages of the Invention
[0125] As described above, according to the present invention, the
spectral transmittances of lens can easily and promptly be measured
by using the optical path of the measurement optical system of the
lens under examination. As a result, even when one of the right and
left eyeglass lenses is broken and the other unbroken lens is to be
replaced, comprehensive determination allows the right and left
eyeglass lenses to be best balanced.
* * * * *