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Claims  |
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What is claimed is:
1. An optical measuring apparatus for examining an eye having:
(1) a measuring light projecting system for projecting a measuring light on
an eye;
(2) a measuring light receiving system including a light receiving sensor
which receives a light reflected by the eye;
(3) optical axes-aligning-focusing means including an optical
axes-aligning-focusing system for aligning the optical axes of said
apparatus and the eye with each other and focusing the light emitted by
said apparatus on the eye; and
(4) measuring means for projecting a measuring light on the eye and
measuring the eye based on a light reflected by the eye and received by
said measuring optical system;
said optical measuring apparatus being characterized in that:
(1) said light receiving sensor is so disposed that the optical axis of
said measuring light receiving system passes through the intersection of a
X-axis and a Y-axis provided on said light receiving sensor;
(2) said axes-aligning-focusing optical system has:
(a) a pair of optical axes-aligning light source means for projecting beams
on the eye, and
(b) said pair of optical axes-aligning light source means for projecting
fine beams on the cornea of the eye is disposed so that said light source
means are asymmetrical with respect to said optical axis of said light
receiving optical system in a direction of said X-axis and that the beam
reflected by the cornea of the eye is received by said light receiving
sensor only when an in-focus state is substantially obtained and an
axes-aligning error is extremely small; and
(3) said optical axes-aligning-focusing means includes:
(a) first comparing means for comparing the level of signals representing
images of two beams reflected by the cornea and received by said light
receiving sensor with a reference value,
(b) first discriminating means for discriminating whether or not said
images are received by said light receiving sensor on the X-axis thereof
when the level of said signals is discriminating to exceed the reference
value,
(c) calculating means for calculating the distance between the two images
of the beams reflected by the cornea received by said light receiving
sensor and the Y-axis of said light receiving sensor, and
(d) second comparing means for comparing two distances calculated by said
calculating means with each other and outputting a signal indicating the
start of the projection of the measuring light if the difference between
the two calculated distances is in the tolerance.
2. An optical measuring apparatus for examining an eye having:
(1) a measuring light projecting system for projecting a measuring light on
an eye;
(2) a measuring light receiving system including a light receiving sensor
which receives a light reflected by the eye;
(3) optical axes-aligning-focusing means including an optical
axes-aligning-focusing system for aligning the optical axes of said
apparatus and the eye with each other and focusing the light emitted by
said apparatus on the eye; and
(4) measuring means for projecting a measuring light on the eye and
measuring the eye based on a light reflected by the eye and received by
said measuring optical system;
said optical measuring apparatus being characterized in that:
(1) said light receiving sensor is so disposed that the optical axis of
said measuring light receiving system passes through the intersection of a
X-axis and a Y-axis provided on said light receiving sensor;
(2) said optical system has:
(a) a pair of optical axes-aligning light source means for projecting beams
on the eye, and
(b) said pair of optical axes aligning light source means for projecting
fine beams on the cornea of the eye is disposed so that said light source
means are symmetrical with respect to said optical axis of said light
receiving optical system in a direction of said X-axis and that the beam
reflected by the cornea of the eye is received by said light receiving
sensor only when an in-focus state is substantially obtained and an
axes-aligning error is extremely small; and
(3) said optical axes-aligning-focusing means includes:
(a) a comparator which compares the level of an image signal outputted from
said light receiving sensor with a reference value so as to output, as a
pulse signal, an image signal indicating the image of first and second
cornea-reflected beams corresponding to beams emitted by first and second
optical axes-aligning light source means,
(b) a synchronizing signal separator circuit for separating a synchronizing
signal outputted together with the image signal from said light receiving
sensor into a horizontal synchronizing signal and a vertical synchronizing
signal,
(c) a circuit for generating an X-axis reference signal indicating that the
image signal outputted from said light receiving sensor corresponds to an
image disposed on the X-axis of said light receiving sensor based on the
horizontal synchronizing signal and the vertical synchronizing signal
outputted from said synchronizing signal separator circuit,
(d) a first AND circuit which outputs a pulse signal in response to the
pulse signal outputted from said comparator and the X axis reference
signal,
(e) a first reflected image detecting circuit which outputs a pulse signal
when a first pulse signal is counted while counting the pulse signal
outputted from said first AND circuit,
(f) a circuit for generating a Y-axis reference signal indicating that the
image signal outputted from said light receiving sensor corresponds to an
image on the Y-axis of said light receiving sensor based on the horizontal
synchronizing signal outputted from said synchronizing signal separator
circuit,
(g) a second AND circuit which outputs a stop signal in response to the
pulse signal outputted from said first reflected image detecting circuit
and the Y-axis reference signal outputted from said circuit for generating
the Y-axis reference signal,
(h) a first circuit for detecting the distance between a reflected image
and the Y-axis which starts a counting in response to the pulse signal
outputted from said first AND circuit and steps the counting in response
to the stop signal outputted from said second AND circuit so as to output
a first distance signal indicating the distance between a first
cornea-reflected image and the Y-axis,
(i) a second reflected image detecting circuit which outputs a pulse signal
when a second pulse signal is counted while counting the pulse signal
outputted from said first AND circuit,
(j) a second counter for detecting the distance between a reflected image
and the Y-axis which starts a counting in response to the Y-axis reference
signal outputted from said Y-axis reference generating circuit and stops
the counting in response to the pulse signal outputted from said second
reflected image detecting circuit so as to output a second distance signal
indicating the distance between a second cornea-reflected image and the
Y-axis, and
(k) a comparing circuit which compares a first distance and a second
distance with each other based on the first and second distance signals
outputted from said first and second circuits for detecting the distance
between a reflected image and the Y-axis and outputs to said apparatus a
signal indicative of the start of the projection of a measuring light if
the difference between the values of the first distance and the second
distance is less than a tolerance.
3. An optical measuring apparatus for examining an eye having:
(1) a measuring light projecting system for projecting a measuring light on
an eye;
(2) a measuring light receiving system including a light receiving sensor
which receives a light reflected by the eye;
(3) optical axes=aligning-focusing means including an optical axes-aligning
focusing system f or aligning the optical axes of said apparatus and the
eye with each other and focusing the light emitted by said apparatus on
the eye; and
(4) measuring means for projecting a measuring light on the eye and
measuring the eye based on a light reflected by the eye and received by
said measuring optical system;
said optical measuring apparatus being characterized in that:
(1) said light receiving sensor is so disposed that the optical axis of
said measuring light receiving system passes through the intersection of
X-axis and Y-axis provided on said light receiving sensor;
(2) said optical axes-aligning-focusing system
(a) has a pair of optical axes-aligning light source means for projecting a
pair of beams close to each other and arranged in a direction of said
X-axis toward the eye, and
(b) said pair of optical axes-aligning light source means is disposed to be
symmetrical with respect to said optical axis in a direction of said
X-axis; and
(3) said optical axes-aligning-focusing means includes
(a) first discriminating means for discriminating whether or not
cornea-reflected images are formed on said light receiving sensor on the
X-axis thereof,
(b) second discriminating means for discriminating whether or not the
cornea-reflected images, formed on said light receiving sensor on the
X-axis thereof and detected by said first discriminating means, do not
overlap with each other and are separate from each other,
(c) calculating means for calculating the distance between the Y-axis of
said light receiving sensor and each of the two images disposed on both
outer sides among the cornea-reflected images received by said light
receiving sensor on the X-axis thereof, and `(d) comparing means for
comparing two distance calculated by said calculating means with each
other and outputting a signal indicating the start of the projection of
the measuring light if the difference between the two calculated distances
is less than the tolerance.
4. An optical measuring apparatus for examining an eye having:
(1) a measuring light projecting system for projecting a measuring light on
an eye;
(2) a measuring light receiving system including a light receiving sensor
which receives a light reflected by the eye;
(3) optical axes-aligning-focusing means including an optical
axes-aligning-focusing system for aligning the optical axes of said
apparatus and the eye with each other and focusing the light emitted by
said apparatus on the eye; and
(4) measuring means for projecting a measuring light on the eye and
measuring the eye based on a light reflected by the eye and received by
said measuring optical system;
said optical apparatus being characterized in that:
(1) said light receiving sensor is so disposed that the optical axis of
said measuring light receiving system passes through the intersection of
X-axis and Y-axis provided on said light receiving sensor;
(2) said optical axes-aligning-focusing system
(a) has a pair of optical axes-aligning light source means for projecting a
pair of beams close to each other and arranged in a direction of said
X-axis toward the eye, and
(b) said pair of optical axes-aligning light source means is disposed to be
symmetrical with respect to said optical axis in a direction of said
X-axis; and
(3) said optical axes-aligning-focusing means includes:
(a) a comparator which compares the level of an image signal outputted from
said light receiving sensor with a reference value so as to output, as a
pulse signal, an image signal indicating the image of first and second
cornea-reflected beams corresponding to first and second beams emitted by
first and second optical axes-aligning light source means and third and
fourth cornea-reflected lights corresponding to third and fourth beams
emitted by a second optical axes-aligning light source means,
(b) a synchronizing signal separator circuit for separating a synchronizing
signal outputted together with the image signal from said light receiving
sensor into a horizontal synchronizing signal and a vertical synchronizing
signal,
(c) a circuit for generating an X-axis reference signal indicating that the
image signal outputted from said light receiving sensor corresponds to an
image on the X-axis of said light receiving sensor based on the horizontal
synchronizing signal and the vertical synchronizing signal outputted from
said synchronizing signal separator circuit,
(d) a first AND circuit which outputs a pulse signal in response to the
pulse signal outputted from said comparator and the X-axis reference
signal,
(e) a first reflected image detecting circuit which outputs a pulse signal
when a second pulse signal is counted while counting the pulse signal
outputted from said first AND circuit,
(f) a circuit for generating a Y-axis reference signal indicating that the
image signal outputted from said light receiving sensor corresponds to an
image on the Y-axis of said light receiving sensor based on the horizontal
synchronizing signal outputted from said synchronizing signal separator
circuit,
(g) a second AND circuit which outputs a stop signal in response to the
pulse signal outputted from said first reflected image detecting circuit
and the Y-axis reference signal outputted from said circuit for generating
a Y-axis reference signal,
(h) a first circuit for detecting the distance between a reflected image
and Y-axis which starts a counting in response to the pulse signal
outputted from said first AND circuit and stops the counting in response
to the stop signal outputted from said second AND circuit so as to output
a first distance signal indicating the distance between a first
cornea-reflected image and Y-axis,
(i) a second reflected image detecting circuit which outputs a pulse signal
when a fourth pulse signal is counted while counting the pulse signal
outputted from said first AND circuit,
(j) a second counter for detecting the distance between a reflected image
and the Y-axis which starts a counting in response to the Y-axis reference
signal outputted from said Y-axis reference generating circuit and stops
the counting in response to the pulse signal outputted from said second
reflected image detecting circuit so as to output a second distance signal
indicating the distance between a second cornea-reflected image and the
Y-axis, and
(k) a comparing circuit which compares a first distance and a second
distance with each other based on the first and second distance signals
outputted from said first and second circuits for detecting the distance
between a reflected image and Y-axis and outputs to said apparatus a
signal indicative of the start of the projection of a measuring light if
the difference between the values of the first distance and the second
distance is less than a tolerance. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical measuring apparatus for
measuring an eye, and more particularly, to an optical measuring apparatus
for automatically measuring various optical characteristic such as the
refractive power of the eye, the curvature of the cornea or the like.
2. Description of the Related Art
An automatic refractometer (apparatus for automatically measuring the
refractive power of an eye) and an automatic keratometer (apparatus for
automatically measuring the curvature of a cornea) and the like are known
as optical apparatuses for examining an eye. According to these
apparatuses, a measuring optical system is constructed by having the eye
disposed at a predetermined position of the optical axis thereof. The
disposition of the eye requires the following two conditions: The optical
axis of the apparatus is aligned by the optical axis of the eye, i.e.,
optical axes-aligned condition is obtained and the focal point of the
optical system of a monitoring camera provided in the apparatus coincides
with the eye disposed on the measuring optical system of the apparatus,
i.e., an in-focus condition is obtained. The automatic refractometer
observes, through the optical system, an optical target (measuring light)
whose image is formed on the eyeground of the eye, namely, on the retina,
thus automatically measuring the refractive power of the eye. In order to
measure the refractive power of the eye, before the measuring lights are
projected, the positions of the measuring optical system of the apparatus
and the eye are adjusted to a measurable condition, namely, a condition in
which optical axes of the optical system and the eye align with each other
and the measuring lights projected by the light projecting optical system
are focused on the eye. According to known automatic refractometers,
before the examination of the eye is started, the apparatus is moved
lengthwise and widthwise so that the position of an axes-aligning mark
(reticle pattern) and the position of the image of a light reflected by
the cornea displayed on the monitor screen align with each other. Thus, an
optical axes alignment is accomplished. In addition, the distance between
the apparatus and the eye is adjusted. Thus, the focal point of the
optical system of the monitoring camera of the apparatus coincides with
the position of the eye disposed on the measuring optical system thereof.
As described above, in order to measure the refractive power of the eye,
it is necessary for an operator to confirm that optical axes-aligned and
in-focus condition have been obtained on the monitor screen and then, to
turn on a measuring start switch.
However, according to the above-described method for examining the eye, it
is difficult for a patient to keep the same posture when optical
axes-aligned and in-focus conditions have been obtained. In practice, it
is very difficult for the operator to turn on the switch immediately after
the optical axes-aligned and in-focus conditions are obtained. That is,
the operator must be skilled in the timing of turning on the measuring
start switch.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical measuring
apparatus for examining an eye provided with a mechanism capable of
reliably obtaining axes-aligned and in-focus conditions in an appropriate
timing.
In accomplishing this and other objects, according to one preferred
embodiment of the present invention, there is provided an improved
apparatus for measuring an eye, for example the refractive power of an
eye, which comprises having a measuring light projecting system for
projecting a measuring light on an eye; a measuring light receiving system
including a light receiving sensor which receives a light reflected by the
eye; optical axes-aligning-focusing means including an
axes-aligning-focusing system for aligning the optical axes of the
apparatus and the eye with each other and focusing the light emitted by
the apparatus on the eye; measuring means for projecting a measuring light
on the eye and measuring the eye based on a light reflected by the eye and
received by the measuring optical system. The optical measuring apparatus
has the following feature. The light receiving sensor is so disposed that
the optical axis of the measuring light receiving system passes through
the intersection section of an X-axis and Y-axis provided on the light
receiving sensor. The axes-aligning-focusing optical system includes a
pair of optical axes-aligning light source means for projecting beams on
the eye. The pair of optical axes-aligning light source means for
projecting fine beams on the cornea of the eye is disposed so that the
light source means are symmetrical with respect to the optical axis B of
the light receiving optical system in an X-direction and that the beam
reflected by the cornea of the eye is received by the light receiving
sensor only when an axes-aligned and in-focus state is substantially
obtained. The optical axes-aligning-focusing means includes; first
comparing means for comparing a level of cornea-reflected image received
by the light receiving sensor with a reference value; discriminating means
for discriminating whether or not two cornea-reflected images are received
by the light receiving sensor of the X-axis thereof when the level of two
cornea-reflected images exceeds the reference value by the first comparing
means; calculating means for calculating the distance between the two
cornea-reflected images received by the light receiving sensor and the
Y-axis of the light receiving sensor; second comparing means for comparing
two distances calculated by the calculating means with each other and
outputting a signal indicating the start of the projection of the
measuring light if the difference between the two calculated distances is
less than the tolerance.
In the above-described construction, if the distance between the measuring
apparatus and the eye is inappropriate, that is, if the beams emitted by
the optical axes-aligning-focusing system is not focused on the eye, the
optical axes aligning beams reflected by the cornea is not received by the
light receiving sensor. Even if the beams are received by the light
receiving sensor, the level of the signals indicating the cornea-reflected
images is lower than the reference value. This condition is detected by
the first comparing means. Thus, an in-focus state can be obtained.
Further, when the axes-aligning error is relatively large, the
cornea-reflected images are not received by the light receiving sensor.
This state is also discriminated by the first comparing means. In the case
where the axes-aligning error is extremely small, the mis-alignments in
X-direction and Y-directions in the light receiving sensor are considered.
The mis-alignment in Y-direction is detected by the discriminating means
and the mis-alignment in Y-direction is detected by the calculating means
and the second comparing means. Thus, an optical axes-alignment is
accurately accomplished. When in-focus state and optical axes-aligned
states are obtained, the second comparing means outputs to the apparatus a
signal indicating that the projection of a measuring light should be
started.
Therefore, according to the above-described construction, when in-focus
state and optical axes-aligned states are obtained, the examination of the
eye is immediately started. Thus, an appropriate measuring timing can be
obtained.
According to another preferred embodiment in accordance with the present
invention, the axes-aligning-focusing system has a pair of optical
axes-aligning light source means for projecting a pair of beams close to
each other and arranged in X-direction on the eye. The pair of optical
axes-aligning light source means is disposed to be symmetrical with
respect to the optical axis in X-direction. The optical
axes-aligning-focusing means includes a first discriminating means for
discriminating whether or not cornea-reflected images are formed on the
light receiving sensor on the X-axis thereof; a second discriminating
means for discriminating whether or not cornea-reflected images, formed on
the light receiving sensor on the X-axis thereof and detected by the first
discriminating means, do not overlap with each other and are separated
from each other; and a calculating means for calculating the distances
between the Y-axis of the light receiving sensor and each of two images
disposed on both outer sides among four images received by the light
receiving sensor on the X-axis thereof; and comparing means for comparing
two distances calculated by the calculating means with each other and
outputting a signal indicating the start of the projection of the
measuring light if the difference between the two calculated distances is
within the tolerance.
In the above-described construction, an optical axes alignment in a
Y-direction of the light receiving sensor is carried out by the first
discriminating means and a focusing adjustment is performed by the second
discriminating means. That is, the first discriminating means detects
whether or not a cornea-reflected image is formed on the X-direction of
the light receiving sensor. Thus, an optical axes alignment in a
Y-direction in the light receiving sensor is effected. The second
discriminating means detects whether or not four images reflected by the
cornea do not overlap with each other or are separated on the light
receiving sensor, thus discriminating whether or not the lights emitted by
the optical axes-aligning-focusing means is focused on the eye. The
calculating means and the comparing means detect whether or not the four
images, namely, a pair of cornea-reflected images received by the X-axis
on the left and right sides thereof are symmetrical with respect to the
Y-axis thereof. That is, the calculating means and the comparing means
detects an optical axes-aligned state. When the optical axes-aligned state
is obtained, the comparing circuit outputs to the apparatus a signal
indicating that the projection of a measuring light be started.
Similarly to the above-described construction, when the optical axes are
aligned and in-focus conditions are obtained, the examination of the eye
is started. Thus, an appropriate measurement timing can be always obtained
.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and features of the present invention will become
apparent from the following description taken in conjunction with the
preferred embodiments thereof with reference to the accompanying drawings,
in which:
FIG. 1 is an illustration of the optical system of an automatic
refractometer, used as an optical measuring apparatus for examining an
eye, in accordance with one embodiment of the present invention;
FIG. 2 shows a measuring light projecting optical system included in the
optical system shown in FIG. 1;
FIG. 3 shows a light receiving optical system included in the optical
system shown in FIG. 1;
FIG. 4 shows an optical axes-aligning-focusing optical system included in
the optical system shown in FIG. 1;
FIG. 5 (a), (b), and (c) show the relationship between the positions of the
eye and the optical axes-aligning light source of the automatic
refractometer shown in FIG. 1;
FIG. 6 is a block diagram of the automatic refractometer shown in FIG. 1;
FIG. 7 shows a condition in which optical axes-aligned and in-focus states
are obtained in which (a) shows an image displayed on a monitor screen;
(b) shows an image signal on X-axis; and (c) shows a binary image signal
on X-axis;
FIG. 8 shows a condition in which an in-focus state is obtained, but an
optical axes-aligned state is not obtained in which (a) designates an
image displayed on a monitor screen; (b) shows an image signal on an
X-axis; and (c) denotes a binary image signal on the X-axis;
FIG. 9 shows a condition in which an optical axes-aligned state is
obtained, but an in-focus state is not obtained, in which (a) designates
an image displayed on a monitor screen; (b) shows an image signal an image
signal on X-axis; and (c) denotes a binary image signal on the X-axis;
FIG. 10 shows, similarly to FIG. 1, the optical system of an automatic
refractometer, according to a second embodiment of the present invention;
FIG. 11 is an illustration showing the relationship between an optical
axes-aligning light source and an eye in an automatic refractometer shown
in FIG. 10; and
FIGS. 12 (a), 12 (b), 12(c), 13(a), 13(b), 13(c), l4(a), l4(b), and l4(c)
are illustrations showing the second embodiment and being similar,
respectively, to FIGS. 7(a), 7(b), 7(c), 8(a), 8(b), 8(c), 9(a), 9(b), and
9(c).
DETAILED DESCRIPTION OF THE INVENTION
Before the description of the present invention proceeds, it is to be noted
that like parts are designated by like reference numerals throughout the
accompanying drawings.
Referring now to FIGS. 1 through 9, a first embodiment of the present
invention is described hereinafter. FIG. 1 is an illustration showing the
entire optical system of an automatic refractometer of an optical
measuring apparatus for examining an eye (hereinafter referred to as
apparatus) in accordance with a first embodiment of the present invention.
FIG. 2 shows a measuring light projecting optical system shown in FIG. 1.
FIG. 3 shows a light receiving optical system shown in FIG. 1. FIG. 4
shows an optical axes-aligning-focusing optical system shown in FIG. 1.
The optical axis (A) of the measuring light projecting optical system
extends from a light source 2 to a first half mirror 3 and is reflected by
a first half mirror 3 at an angle of 90.degree., then travels to an eye to
be examined (hereinafter referred to as eye E). An infrared ray emitting
diode is used as the light source 2. Various optical elements are disposed
along an optical axis a.sub.1 extending rectilinearly from the light
source 2 to the first half mirror 3. A measuring light emitted by the
light source 2 is reflected by the first half mirror 3, thus traveling
from the apparatus to the eye E along an optical axis a.sub.2. That is,
the measuring light can be projected into the eye E by disposing the
optical axis a.sub.E of the eye E on the optical axis a.sub.2. The
following optical elements are disposed along the optical axis a.sub.1
between the light source 2 and the first half mirror 3 in the following
order: a collimator lens 4, a quadrangular pyramid prism 5, a diaphragm 6,
a light projecting lens 7, a four-opening mirror 8, and an eyepiece 9. In
order to form four spot patterns of the measuring light, the quadrangular
pyramid prism 5 disperses an infrared ray which has been emitted by the
light source 2 and passed through the collimator lens 4 into four beams
concentrically spaced from each other at an an angular interval of
90.degree. in the periphery of the optical axis a.sub.1. The diaphragm 6
is disposed at the focal point of the light projecting relay lens 7.
Therefore, the four beams which have been dispersed by the quadrangular
pyramid prism 5 pass through the diaphragm 6, and thereafter, are incident
on the light projecting relay lens 7. Then, the four beams become parallel
with the optical axis a.sub.1, thus forming four spot patterns. In the
light receiving optical system 10 which is described later, the
four-opening mirror 8 reflects the measuring light reflected by the retina
of the eye E at an angle of 90.degree., the upper face of which forms
45.degree. with the optical axis a.sub.1. In the light projecting optical
system 1, four small openings are formed on the four-opening mirror 8 at
the portions corresponding to the light paths of the four spot patterns so
that the four-opening mirror 8 does not intercept the optical path of the
four spot patterns. Thus, the measuring lights which have passed through
the openings of the four opening mirror 8 are incident on the eyepiece 9
as four spot patterns. Then, the measuring lights are reflected at an
angle of 90.degree., thus entering into the eye E. The optical axes
b.sub.1 and b.sub.2 disposed from the eye E to the four-opening mirror 8
and forming part of optical axis (B) of the light receiving system 10
coincide with the optical axes a.sub.2 and a.sub.1 of the optical axis (A)
of the light projecting system 1, respectively.
In the light, receiving optical system, the measuring lights reflected by
the retina travel backward to the of the four-opening mirror 8 along the
optical axes b.sub.1 and b.sub.2 , thus being reflected by the
four-opening mirror 8 at an angle of 90.degree.. A micromirror 11 having a
face parallel with the faces of the four-opening mirror 8 is disposed on
the optical axis b.sub.3 of the reflected measuring lights. The
micromirror 11 reflects the reflected measuring lights downward at right
angles with the optical axis b.sub.3. There is provided below the
micromirror 11 an image forming lens 12 and a light receiving sensor 13
composed of a CCD (charge coupled device) serving as an image sensor
matrix along an optical axis b.sub.4. The optical axis b.sub.4 pass
through the center of the light receiving sensor 13. Therefore, supposing
that the cross section of the space through which a light passes is a
field, the center of the field is disposed on the optical axis (B) of the
light receiving optical system 10. In other words, the optical axis (B) or
b.sub.4 passes through the intersection, of the X- axis and Y-axis on the
light receiving sensor 13.
In the optical axes-aligning-focusing optical system 15, a pair of an
optical axes-aligning light sources 21, 21 comprising an infrared ray
emitting diode is horizontal and symmetrical with respect to the optical
axis a.sub.2. The direction of a straight line formed by connecting both
the optical axes-aligning light sources 21 and 21 coincides with the
direction in which the field is scanned on the light receiving sensor 13.
Normally, when the image in the field is monitored, a scanning line moves
downward sequentially while the field is scanned widthwise in the monitor
screen. In this embodiment, the image in the field is scanned widthwise,
i.e., the scanning direction is from left to right as viewed from an
operator. The diameter of lights emitted by the optical axes-aligning
light source 21 are greatly reduced into light beams by the collimator
lens 22 disposed forward of the optical axes-aligning light source 21.
When the eye E is appropriately disposed for an examination, the beams
reflected by the cornea travels back in parallel with the optical axis
a.sub.2. Thus, the beams are detected by the light receiving sensor 13.
FIGS. 5(a), 5(b), and 5(c) show directions, of lights reflected by the
cornea, which differ from each other depending on the distance between the
eye E and the optical axes-aligning light source 21. FIG. 5(a) shows the
case in which the distance therebetween is too short. FIG. 5(a) shows the
case in which the distance therebetween is appropriate enough to be
examined. FIG. 5(c) shows the case in which the distance therebetween is
too long. As understood from these figures, each of the diameters of the
beams emitted by the respective optical axes-aligning light sources is
very small and each of the areas of spots of the beams is very small on
the cornea. Therefore, each of the diameters of beams reflected by the
cornea is small and as such, does not diffuse. Thus, If the optical
axes-aligning light source 21 is too far from or near to the eye E, the
distance between the optical axis a.sub.2 and the beams reflected by the
cornea becomes great as the beams travel forward from the eye E. On the
other hand, when the distance between the eye E and the optical
axes-aligning light source 21 is appropriate, the beams reflected by the
cornea travel substantially parallel with the optical axis a.sub.2, thus
reaching the light receiving sensor 13. In this embodiment, the focal
point of the optical system of a monitoring camera coincides with the
cornea when the distance between the optical axes-aligning light source 21
and the eye E is as shown in FIG. 5(b).
Meanwhile, when the error of focusing condition is extremely small, the
reflected lights from the cornea can be received by the light receiving
sensor 13.
The optical elements constituting the optical path of beams emitted by the
optical axes-aligning light source 21 and reflected by the cornea
(hereinafter referred to as optical axes-aligning beam) are described
hereinafter. An optical axes aligning beam partially pass through the
first half mirror 3 is reflected downward at an angle of 90.degree. by a
second half mirror 14, then passes through a monitor relay lens 16. A
first 45.degree. mirror 17 is disposed below the monitor relay lens 16.
The beam which has passed through the mirror 17 is incident on a reticle
plate 18 made of a transparent glass on which a reticle pattern is drawn.
The reticle plate 18 is conjugate with the eye E with respect to the
monitor relay lens 16. The beam which has passed through the reticle plate
18 is incident on a second 45.degree. mirror 19 which reflects the beam
downward at an angle of 90.degree.. The light receiving optical system 10
and the optical axes-aligning-focusing optical system 15 have in common
the optical axis b.sub.4 disposed below the second 45.degree. mirror 19
and including the image forming lens 12 and the light receiving sensor 13.
Accordingly, the optical axes aligning-focusing-optical system 15 has a
construction in which the monitoring reticle optical system is
incorporated in the optical system of the monitoring camera. The
micromirror 11 of the optical axes aligning-focusing-optical system 15 is
so small that the optical axes aligning beams travel in the periphery
thereof. Thus, the micromirror 11 causes no problem in measuring the
refractive power of the eye E. As shown in FIG. 1, a target 20 is disposed
on the extension of the optical axis a.sub.2 of the light projecting
optical system 1 so that a patient watches a far point in having the
refractive power of the patient's eye E examined.
FIG. 6 is a block diagram of the automatic refractometer. The measuring
beams (emitted by the light source 2) reflected by the retina and beams
(emitted by the optical axes-aligning light source 21) reflected by the
cornea are received by the light receiving sensor 13 to be scanned, thus
sequentially converting the beams into image signals (electric signals).
Together with synchronizing signals of the scanning, the image signals are
inputted to a comparator 31, a synchronizing signal separator circuit 32,
an image processing device 52, and a monitor 53.
The image signals inputted to the comparator 31 are outputted to an AND
circuit 33 in two different levels. That is, one level is higher and the
other level is lower than a reference value set in the comparator 31. The
reference value substantially corresponds to the luminance of the optical
axes-aligning light source 21. That is, the level of the signal
corresponding to the image of the measuring beam reflected by the retina
is lower than the reference value and the signal corresponding to the
image of the optical axes-aligning beam reflected by the cornea is lower
than the reference value. The synchronizing signal inputted to the
synchronizing signal separator circuit 32 is separated into a horizontal
synchronizing signal and a vertical synchronizing signal. The horizontal
synchronizing signal is inputted to an X-axis reference generating circuit
34 and a Y-axis reference generating circuit 35. The vertical
synchronizing signal is inputted to only the X-axis reference generating
circuit 34. In the X-axis reference generating circuit 34, based on the
horizontal synchronizing signal and the vertical synchronizing signal,
timing signals representing the X-axis which passes through the center of
the optical axis are generated and inputted to the AND circuit 33. The
Y-axis reference generating circuit 35 includes a clock pulse generating
circuit and a pulse counter. The Y-axis reference generating circuit 35
outputs a timing signal to the AND circuit 41 and a counter 38 for
detecting the distance of the right side-spot with respect to Y-axis when
the number of pulses counted from the point the horizontal synchronizing
signal coincides with Y-axis which passes through the center of the
optical axis. The AND circuit 33 outputs signals to a right side-spot
detecting circuit 36, a left side-spot detecting circuit 37, and a counter
39 for detecting the distance of the left side-spot with respect to Y-axis
only when the signal outputted from the comparator 31 is disposed on
X-axis, namely, the reference axis. The signal corresponding to the beam
emitted by the optical axes-aligning light source 21 disposed on the right
side is outputted from the right side-spot detecting circuit 36. The
signal corresponding to the beam emitted by the optical axes-aligning
light source 21 disposed on the left side is outputted from the left
side-spot detecting circuit 37. That is, the left side-spot detecting
circuit 37 comprising a one-pulse counter outputs a signal to the AND
circuit 41 when one pulse signal is inputted thereto from the AND circuit
33. The right side-spot detecting circuit 36 comprising a two-pulse
counter outputs a signal to the counter 38 when two pulse signals are
inputted thereto from the AND circuit 33.
The counters 38 and 39 serve as means for measuring the distance between
Y-axis and the right side-spot image of the beam reflected by the cornea
and the distance between Y-axis and the left side-spot image of the beam
reflected by the cornea. The counter 39 starts a counting in response to a
signal outputted from the AND circuit 33 and terminates the counting in
response to a signal outputted from the AND circuit 41. In response to
signals outputted from the left side-spot detecting circuit 37 and the
Y-axis reference generating circuit 35, the AND circuit 41 outputs to the
counter 39 a stop signal indicating that the counting be stopped. Thus,
the counter 39 terminates the counting. The counter 39 outputs to a
comparator 40 a counted value corresponding to the distance between Y-axis
and the left side-spot image reflected by the cornea. The counter 38
starts a counting in response to a signal outputted from the Y-axis
reference generating circuit 35 and terminates the counting in response to
a signal outputted from the detecting circuit 36. The counter 39 outputs
to the comparator 40 a counted value corresponding to the distance between
Y-axis and the right side-spot image reflected by the cornea. The
comparator 40 decides whether or not the absolute values counted by the
counters 38 and 39 are close to each other and within the tolerance,
namely, whether or not the positions of the left side-spot image and right
side-spot image of the beams reflected by the cornea are symmetrical with
respect to Y-axis. If the counted values are within the tolerance, a
signal indicating that a measuring can be started is outputted to a
microcomputer 51, so that the microcomputer 51 outputs to the light
projecting optical system 1 a signal which indicates that a measuring
light should be projected.
FIGS. 7, 8, and 9 show the following three conditions when an optical
axes-alignment and a focusing are carried out. FIGS. 7(a), 8(a), and 9(a)
show images of spots and the eye E displayed on the monitor 53. FIGS.
7(b), 8(b), and 9(b) show image signals detected by the light receiving
sensor 13 on the X-axis thereof. FIGS. 7(c), 8(c), and 9(c) show the
binary signals of the image signals. FIG. 7 shows the condition in which
the optical axes of the eye E and the axes-aligning-focusing optical
system 15 are aligned with each other and the beams emitted by the
axes-aligning-focusing optical system are focused on the eye E. FIG. 8
shows the condition in which the beams emitted by the
axes-aligning-focusing optical system are focused on the eye E, but
optical axes of the eye E and the axes-aligning-focusing optical system 15
are not aligned with each other. FIG. 9 shows the condition in which the
optical axes of the eye E and the axes-aligning-focusing optical system 15
are aligned with each other, but the beams emitted by the
axes-aligning-focusing optical system are not focused on the eye E.
As shown in FIG. 7, when the optical axes of the eye E and the
axes-aligning-focusing optical system 15 are aligned with each other and
the beams emitted by the axes-aligning-focusing optical system are focused
on the eye E, the images of the eye E and the spot images of the optical
axes-aligning beams are clearly displayed on the center of the monitor. In
particular, the spot images P.sub.1 and P.sub.2 formed by the optical
axes-aligning beams are clearly displayed on the monitor screen. That is,
as shown in FIG. 7(b), the signal outputted from the light receiving
sensor 13 and corresponding to the spot images P.sub.1 and P.sub.2 has
clear peaks PL.sub.1 and PL.sub.2 at the portions corresponding to the
spot images P.sub.1 and P.sub.2. As described previously, since the
reference value TL is set in the comparator 31 so as to convert the signal
outputted from the light receiving sensor 13 into a high level signal and
a low level signal, two pulse signals PS.sub.1 nd PS.sub.2 outputted from
the AND circuit 33 and corresponding to the spot images P.sub.1 and
P.sub.2 can be obtained on X-axis as shown in FIG. 7(c).
It is to be noted th | | |
