JPH03109028A - Eye sight detector having means for controlling quantity of irradiation light - Google Patents

Abstract

PURPOSE:To enable highly accurate detection of eye sight by controlling a quantity of irradiation light utilizing a signal based on an interval of a cornea reflection image to be detected to always set a quantity of irradiation light to an eye ball to an optimum value. CONSTITUTION:Cornea reflection images (e) and (f) based on a luminous flux reflected on the surface of cornea 1 among infrared rays lighting an eye ball is formed again at points e' and f' on an image sensor 9 through a light receiving lens 7. An eye sight computation circuit 401 records a signal corresponding to an interval between the two cornea reflection images e' and f' into a latch memory 402. A data of the latch memory 402 is converted in code with a decoder 403 and for example, when two terminals are selected, a transistor 407 is turned ON and a current determined by a resistor 411 flows through a resistor 413 to generate a voltage V0. Therefore, it is so arranged that a terminal 1 is selected when the interval of the cornea reflection images e' and f' is small while a terminal 7 is selected in sequence when it is large. With such an arrangement, as a light emitting element 416 as light source is driven by a constant current, when a resistance value of a resistor 417 is R, light is emitted with a power source of V0/R. Thus, the eye ball is always lighted with a minimum necessary quantity of light.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a line of sight detection device having an irradiation light amount control means. Reflection that is formed when the axis of the direction of the gaze point observed by the observer (photographer) on the focal plane (the so-called line of sight (visual axis)) is illuminated on the observer's eyeball surface with the light beam from the illumination means. The present invention relates to a line of sight detection device having an irradiation light amount control means that appropriately controls the amount of irradiation light onto the eyeball surface when detecting using an image.

(Prior Art) Various line-of-sight detection devices have been proposed that detect a so-called line of sight (visual axis) that detects which position on an observation surface an observer (subject) is observing.

For example, in Japanese Patent Application Laid-Open No. 61-172552, a parallel light beam from a light source is projected onto the anterior segment of the subject's eye, and the visual axis is (Point of attention) is being sought.

FIG. 6 is an explanatory diagram of the principle of the line of sight detection method.

In the figure, reference numeral 4 denotes a light source such as a light emitting diode that emits infrared light that is insensitive to the observer, and is arranged on the focal plane of the projection lens 6.

The infrared light emitted from the light source 4 is turned into parallel light by the projection lens 6 and reflected by the half mirror 5 to illuminate the cornea 1 of the eyeball 101. At this time, a corneal reflection image d based on a part of the infrared light reflected on the surface of the cornea 1 is transmitted through the half mirror 5 and focused by the light receiving lens 7, and is re-formed as a corneal reflection image d at a position d' on the image sensor 9. Image.

Further, the light beams from the ends a and b of the iris 3 are guided onto the image sensor 9 via the half mirror 5 and the light receiving lens 7, and images of the ends a and b are formed at the positions a and b'. . When the rotation angle θ of the optical axis A of the eyeball, which corresponds to the optical axis A of the light-receiving lens 7, is small, the iris 3 (1) The two coordinates of the ends a and b are Za,
When Zb, the coordinate Zc of the center position C of the iris 3 is expressed as Za+Zb Zaillus 2 .

In addition, the Z coordinate of the position d of the corneal reflection image is Zd, and the angle ll is
The distance between the center of curvature 0 of 5i1 and the center C of iris 3 is oC
Then, the rotation angle θ of the eyeball optical axis I is 0C-5inθ4Zc
-Zd...approximately satisfies the relational expression (1). Therefore, by detecting the position of each singular point (the corneal reflected image d and the ends a and b of the iris) projected onto the image sensor 9, the rotation angle θ of the eyeball optical axis i can be determined. At this time, equation (1) is β-QC-sinθ, Za"+Zb':zci'
・ ・ ・ ・ ・ (2) can be replaced. However, β is the occurrence position d of the corneal reflection image.
It is a magnification determined by the distance 1 between the light receiving lens 7 and the light receiving lens 7 and the distance all no between the light receiving lens 7 and the image sensor 9, and is usually a nearly constant value.

By detecting the direction of the line of sight (point of gaze) of the observer's eye to be examined in this manner, it is possible to know which position on the focal plane the photographer is observing in, for example, an eye reflex camera.

For example, when an automatic focus detection device has distance measuring points not only at the center of the screen but also at multiple locations within the screen, and an observer selects one of the distance measuring points to perform automatic focus detection, This is effective in eliminating the need to manually select one of the points, treating the point observed by the observer as the distance measurement point, automatically selecting the distance measurement point, and performing automatic focus detection.

(Problem to be solved by the invention) Said JP-A-61
The line of sight detection device proposed in Publication No. 172552 generates a corneal reflection image or an iris image based on the light flux from the illumination means that is imaged on the image sensor surface according to the interval (distance) between the eyeball and the line of sight detection device. The light intensity changes greatly.

For example, as the distance between the eyeball and the line-of-sight detection device increases, the light intensity of these images decreases. In order to enable good line-of-sight detection even when this distance is large, it is necessary to illuminate the eyeball with a relatively large amount of light from the illumination means.

On the other hand, if the distance between the eyeball and the line-of-sight detection device becomes narrower, the light intensity set when the distance is large becomes too strong, and the amount of light irradiated to the eyeball becomes too high, resulting in problems from the viewpoint of eye safety. is also becoming a problem.

Generally, it is preferable that the eyeball be illuminated with a substantially constant amount of light that is the minimum amount that allows line of sight detection. However, since the distance between the eyeball and the line-of-sight detection device generally changes each time, it is very effective to illuminate with a constant amount of light that allows line-of-sight detection.

The present invention provides a line-of-sight detection device having an irradiation light amount control means that can always set the amount of light irradiated to the eyeball required for line-of-sight detection to an optimal value, and enables highly accurate line-of-sight detection. purpose.

(Means for Solving the Problems) A line of sight detection device having an irradiation light amount control means of the present invention illuminates the eyeball of a subject with a plurality of illumination means, When a detection means detects the image formation position of a plurality of corneal reflection images based on reflected light and an iris image of the eyeball on a predetermined plane, and the line of sight of the subject is determined using an output signal from the detection means. , the amount of light irradiated by the illumination means is controlled by the light amount control means using a signal based on the interval between the corneal reflection images detected by the detection means.

Further, in the present invention, the eyeball of the subject is illuminated with an illumination means, and the imaging position of a corneal reflection image and an iris image of the eyeball based on light reflected from the cornea of the eyeball of the illumination means on a predetermined plane is detected. The present invention is characterized in that the amount of light irradiated by the illumination means is controlled by the switch means when the line of sight of the subject is detected using the output signal from the detection means.

In addition, in the present invention, for example, the amount of light irradiated onto the eyeball by the illumination means is small before the corneal reflection image is detected by the detection means, and is irradiated with a predetermined amount of light after detection.

(Example) FIG. 1 is a schematic diagram of the main parts when detecting the line of sight of an eyeball in a first example of the present invention. FIG. 2 is an explanatory diagram showing the output state from the image sensor 9 of FIG. 1.

In the figure, 101 is the eyeball of the subject (observer), 1 is the cornea of the subject's eyeball, 2 is the sclera, and 3 is the iris. e' is the center of rotation of the eyeball 101, 0 is the center of curvature of the cornea 1, a and b are the ends of the iris 3, and e and f are the light sources 4a, which will be described later.
, 4b is the generation position of the corneal reflection image. 4a, 4
Each light source b is a light emitting diode or the like that emits infrared light that is insensitive to the subject. Furthermore, the light source 4a (4b) is located closer to the focal plane of the light emitting lens 6a (6b) than the focal plane of the light emitting lens 6a (6b).
b) located on the side; Projection lens 6a.

Reference numeral 6b illuminates a wide area of the cornea by using the light beams from the light sources 4a and 4b as a diverging light beam. Here, the light source 4a is on the optical axis of the light projection lens 6a, and the light source 4b is on the optical axis of the light projection lens 6b, and is arranged symmetrically in the Z direction with respect to the optical axis A. Note that the light sources 4a, 4b and the projection lenses 6a, 6b constitute elements of illumination means.

Reference numeral 7 denotes a light-receiving lens which images the corneal reflection images e and f formed near the cornea 1 and the ends a and b of the iris 3 on the surface of the image sensor 9. In addition, the light receiving lens 7 and the image sensor 9
constitutes one element of the light receiving means.

Reference numeral 10 denotes a calculating means, which calculates and determines the line of sight of the subject using the output signal from the image sensor 9, as will be described later.

A indicates the optical axis of the light receiving lens 7, which coincides with the X axis in the figure.

A is the optical axis of the eyeball, which is tilted at an angle θ with respect to the X axis.

In this embodiment, the infrared light emitted from the light source 4a (4b) passes through the projection lens 6a (6b) and then widely illuminates the cornea 1 of the eyeball 101 while diverging. The infrared light transmitted through the cornea 1 illuminates the iris 3.

At this time, angle II of the infrared light illuminating the eyeball! Corneal reflection images e and f based on the light beam reflected on the surface of the image sensor 21 are re-imaged at points e and f' on the image sensor 9 via the light receiving lens 7. At this time, e' and f' in FIGS. 1 and 2 are corneal reflection images (virtual images) e generated by a pair of light sources 4a and 4b.
and a projected image of f. The midpoint of the projected images e' and f' is approximately the same as the projection position of the corneal reflected image onto the image sensor 9 (the position of point d' in FIG. 6) that occurs when the illumination means is placed on the optical axis A. We are doing so.

In addition, the infrared light diffusely reflected on the surface of the iris 3 is transmitted to the light receiving lens 7.
The light is guided onto the image sensor 9 via the iris to form an iris image. On the other hand, the infrared light that passes through the pupil of the eye illuminates the retina and is absorbed there, but since the illuminated area is a sparse area of photoreceptor cells away from the fovea, the subject cannot use the light source 4a.
, 4b cannot be visually recognized.

The vertical axis in Fig. 2 represents the output of the image sensor 9 in two directions.
This is what is shown. In the figure, the pupil and iris 3, because almost no infrared light passes through the pupil and is reflected back.
There is an output difference at the boundary of the iris, and as a result, the iris image a
, b' are detected.

Therefore, in this embodiment, the arithmetic unit 10 detects the coordinates (Za', Zb', Ze, Zf') of each singular point (ab', e'', f') of the eyeball on the image sensor 9, and ) Based on the formula β・0C−8inθ given Z8′+Zb′Ze '
+Zf ” ・ ・ ・ ・ (3) Calculate the eyeball and rotation angle θ.

The visual axis of the eyeball is determined from the rotation angle θ at this time, and the subject's line of sight is detected from this.

Dan.

However, β is the magnification (~□) of the receiving optical system and is J2° Ru.

In the line-of-sight detection device according to the present invention, the distance Rx l between the generation position of the corneal reflection image and the light receiving lens 7 is...
- Satisfies the relational expression (4). Therefore, even if the distance between the line of sight detection device and the eyeball changes, the interval lZe between the two corneal reflection images
The distance 5I11 can be calculated from -Zf'l.

However, Zo is the distance between the pair of light sources 4a (4b) in the Z direction, and λ2 is the distance between the light sources 4a (4b) and the light receiving lens 7 in the X direction.

FIG. 3 is a schematic diagram of a main part of an embodiment in which the line of sight detection device according to the present invention is applied to a single-lens reflex camera.

In this figure, the same elements as those shown in FIG. 1 are given the same reference numerals. Note that the arithmetic unit and focus plate are omitted.

In this embodiment, the image of the subject is raised by the photographing lens 14 and is formed on a focusing plate (not shown) via the flip-up mirror 13. Then, an eyepiece 1 having a dichroic mirror surface 11a as an erect normal image is passed through a pentagonal roof prism 12.
1, the subject image on the focus plate is observed.

Generally, an observer (subject) looking into the viewfinder field of a single-lens reflex camera captures the object light (image) that passes through the photographic lens 14, is reflected by the flip-up mirror 13, and is formed on the focusing plate, and then passes through the penta-roof prism 12 and the eyepiece. 11 to receive and observe light. At this time, the observer rotates his/her eyeball to direct his or her line of sight to the object to be watched within the viewfinder field of view.

A pair of illumination means (
A light source 4a (4b) and a projection lens 6a (6b) is arranged to illuminate the eyeballs of an observer (not shown).

At this time, the observer sees a light source 4a (
4b) cannot be visually recognized. The infrared light reflected by the cornea and iris of the eyeball enters the eyepiece 11 and is reflected by the dichroic mirror portion 11a of the eyepiece 11, forming respective images on the image sensor 9 via the light receiving lens 7. do. Here, the dichroic mirror portion 11a of the eyepiece 11 is formed, for example, by bonding two rectangular prisms coated with a dielectric multilayer film, and the dielectric multilayer film transmits visible light and reflects infrared light. is set to.

Each singular point is detected by each device based on the reflection of the eyeball formed on the image sensor 9, and the line of sight of the observer is detected by performing calculation according to equation (3) by a calculation device (not shown). There is.

FIG. 4 is a block diagram of essential parts of an electric circuit according to the first embodiment of the present invention. This figure shows a case where the amount of light emitted from the illumination means is controlled using a signal based on the interval between two corneal reflection images.

In the same figure, 401 is a line of sight calculation circuit corresponding to the calculation means 10 in FIG.
A signal corresponding to the interval ' is recorded in the temporary recording type latch memory 402. In the latch memory 402, the line of sight information is calculated by the line of sight calculation circuit 401, and the corneal reflection images e, f' are stored in the latch memory 402.
Basically, only when the interval between the corneal reflection images e and f' can be detected, that information is recorded.When the interval between the corneal reflection images e and f' cannot be detected, for example, another piece of information corresponding to one corner 0 is recorded manually. It is configured to do so.

A decoder 403 converts the information recorded in the latch memory 402 into codes and inverts any one of terminals 0, . . . , 7 to a high level side. transistor 404
408, resistors 409 to 413, and an operational amplifier 414 convert the information decoded by the decoder 403 into an analog voltage.

Here, KVc is a constant voltage power supply applied to the non-inverting input terminal of the operational amplifier 414. The output of the operational amplifier 414 is applied to the non-inverting input terminal of the operational amplifier 415, and the light emitting element (light source) 416 is connected to the operational amplifier 415 and resistors 417, 4.
18 and a transistor 419 to drive with a constant current. 42
0 is a current control circuit when no corneal reflection image is detected.

First, the power is turned on to the entire system, and the corneal reflection image is not detected until the examinee's eyeball is set in the line-of-sight detection device, that is, until the examinee looks onto a predetermined surface of the line-of-sight detection device, so the latch memory 402 0 information is written to n1 as described above. At this time, the decoder 403 selects the output terminal 0 and inverts it to the high level side, the transistor 405 turns on, and it becomes possible to generate an idling calculation current determined by the resistor 409 for forming a minute corneal reflection image.

The current at this time is finally controlled on/off via the transistor 404 which is controlled by the output of the current control circuit 420.

The first mode of the current control circuit 420 is a mode in which the output is always at a high level, and when a corneal reflection image cannot be detected, an idling calculation current for forming a corneal reflection image determined by the resistor 409 is always supplied. .

The second mode is convenient when the line of sight detection device is used in a camera or the like, and is a mode in which the output power is set to a high level for a certain period of time when the power switch is turned on.

A third mode may be a mode in which the output is periodically raised to a high level at regular intervals. These modes are selected depending on each system.

Next, the positions of the corneal reflection images e and f' are detected, and when the code data of the interval is entered into the latch memory 402, it is code-converted by the decoder 403. For example, when 2 terminals are selected, the transistor 407 is turned on, and the resistor 411 A current determined by flows through the resistor 413 and the corresponding voltage V. occurs. The interval between the corneal reflection images e and f' decreases as the distance (interval) between the eyeball and the line of sight detection device increases, and increases as the distance decreases.

For this reason, the configuration is such that, for example, when the interval between the corneal reflection images e and f' is small, the terminal is selected, and when it is large, the terminal 7 is selected in sequence. In this case, terminal 1 is selected when the eyeball is far away, so in order to increase the amount of illumination light, resistor 41 is selected.
The calculation current is increased by decreasing the value of 0.

Conversely, since terminal 7 is selected when the eyeball is nearby, in order to reduce the amount of illumination light, the value of resistor 412 is increased to reduce the operational current, and the output V of operational amplifier 414 is
. The value of is reduced to reduce the amount of illumination light.

In this embodiment, the light emitting element 416 as a light source is driven with a constant current, and if the resistance value of the resistor 417 is R, it emits light using a power source of vo/R.

Note that the resistor 409 has a considerably larger resistance value than the resistor 412 in order to flow a calculation current for idling.

As described above, according to this embodiment, the eyeball can be illuminated with the amount of light corresponding to the interval between the corneal reflection images, that is, the distance between the eyeball and the line of sight detection device, so the eyeball is always illuminated with the minimum necessary amount of light. .

In this example, when the subject blinks, the corneal reflection image disappears, so the illumination light intensity returns to the weak light intensity of the idle link state. However, while the corneal reflection image can be continuously detected, Even if the corneal reflection image disappears for a relatively short period of time, the influence of blinking can be removed by configuring the system so that the amount of illumination light before the image disappears can be maintained.

FIG. 5 is a block diagram of essential parts of an electric circuit according to a second embodiment of the present invention. In this embodiment, for example, the distance between the eyeball and the line-of-sight detection device is significantly different when the subject (camera photographer) looks through the line-of-sight detection device when the subject (camera photographer) wears glasses and when he/she is naked. Easy glasses to adjust the amount of lighting,
It is controlled by switching with a switch means for switching to the naked eye.

In the figure, 501 is a line of sight arithmetic circuit corresponding to the arithmetic means 10 in FIG. is a data selector that selects input data based on the signal to the SP terminal. 507 is a decoder which performs code conversion on the information selected by the data selector 506 and inverts the signals of terminals 0, 1.2 to the high level side. transistors 508-511, resistors 512-515,
An operational amplifier 516 converts the information decoded by the decoder 507 into an analog voltage. The output of operational amplifier 516 is applied to the non-inverting input terminal of operational amplifier 517.
The light emitting element 518 includes an operational amplifier 517 and a resistor 519°52.
0 and a transistor 521 to drive the transistor 521 at a constant current. 522
is the current control circuit.

First, the power of the entire system is turned on, and the corneal reflection image is not detected until the examinee's eyeball is set in the line-of-sight detection device, that is, until the examinee looks over the predetermined surface of the line-of-sight detection device. Idle link data memory 505 is selected via SPi child 506 . At this time, the decoder 507 selects output terminal 0 and inverts it to the high level side,
The transistor 509 is turned on, and it becomes possible to generate an idle link calculation current determined by the resistor 512 for forming a minute corneal reflection image.

Next, when a corneal reflection image is detected, the data selector 506 selects the glasses data memory 503 selected by the switch means 502 for switching between glasses and the naked eye data memory 5.
Select one of 04.

When the subject wears glasses and sets the glasses switch to the position shown in the figure, the contents of the glasses data memory 503 are decoded by the decoder 507, the end t1 is inverted to the high level side, and the transistor 510 is turned on, and the resistor 513 is turned on. The output V of the operational amplifier 516 is determined based on the operation and current.

is calculated. If the subject wears glasses,
Since the distance (interval) between the eyeball and the line of sight detection device is large, it is necessary to increase the amount of illumination light, so the value of the resistor 513 is set small.

Next, when used by a person with the naked eye, switch means 5 for switching
02 to the opposite side as shown in the diagram, and the naked eye data memory 50
4 is selected and the contents of this memory are decoded by the decoder 507, the terminal 2 is inverted to the high level side, the transistor 511 is turned on, and the output V of the operational amplifier 516 is determined based on the operational current determined by the resistor 514. is calculated.

In this case, since the distance m<interval between the eyeball and the line of sight detection device is small, the amount of illumination light needs to be small, and the resistor 514
The value of is set large, and the calculation current is made small to make vo, which is the output of the operational amplifier 516, small. The operation of current control circuit 522 is the same as that of current control circuit 420 in FIG. 4, and therefore will not be described here.

In addition, in these embodiments, when the eyeball is not set with the line of sight detection device, slight illumination is performed to detect the corneal reflection image,
Once the eyeball is set, the amount of illumination light can be controlled to a specified level because the corneal reflectance is about 2'.5%, which is significantly larger than other tissues of the eyeball such as the iris.

Furthermore, this embodiment is a simple method and is particularly effective for controlling the amount of illumination light in a line-of-sight detection device in which only one corneal reflection image is formed.

(Effects of the Invention) According to the present invention, the eyeball of the examinee is illuminated by the illumination means, and the line of sight of the examinee is determined by detecting the focal point of the corneal reflection image and iris image from the eyeball on a predetermined plane. When detecting the line of sight, by configuring each element as described above, the amount of light irradiated to the eyeball is controlled to the optimum light amount for detecting the line of sight, and the line of sight is equipped with a means for controlling the amount of irradiated light that can detect the line of sight in good conditions. A detection device can be achieved.

Furthermore, according to the present invention, by illuminating with weak light until the corneal reflection image of the eyeball can be detected, and then illuminating with a predetermined amount of light after the corneal reflection image can be detected, wasteful power consumption of the entire line of sight detection system can be avoided. It is possible to achieve a line-of-sight detection device having an irradiation light amount control means that is preferable from the viewpoint of safety measures, such as being able to eliminate unnecessary light and prevent unnecessary light from being emitted to the outside.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the main parts when detecting the line of sight of the eyeball in the first embodiment of the present invention, FIG. 2 is an explanatory diagram of the output state from the image sensor of FIG. 1, i 3 [Ii is the invention 4 and 5 are schematic diagrams of main parts when the line of sight detection device according to the above is applied to a single-lens reflex camera, respectively. FIG. 6 is a block diagram of a main part of an electric circuit according to a second embodiment, and is a schematic diagram of a conventional line of sight detection device. In the figure, 101 is an eyeball, 1 is a cornea, 2 is a strong 11i, 3 is an iris, 4a, 4b are light sources, 6a, 6b are projecting lenses, 7 is a light receiving lens, 9 is a sensor, 10 is a calculation means, 401,
501 is a line of sight calculation circuit, 403.507 is a decoder, 4
16,518 is a light emitting element, 402 is a latch memory, 4
20° 522 is a current control circuit, and 414 and 415 are operational amplifiers.

Claims (2)

[Claims] (1) A subject's eyeball is illuminated with a plurality of illumination means, and a plurality of corneal reflection images and an iris image of the eyeball are formed on a predetermined plane based on light reflected from the cornea of the eyeball by the plurality of illumination means. When the image position is detected by a detection means and the line of sight of the subject is determined using an output signal from the detection means, the amount of light is determined using a signal based on the interval of corneal reflection images detected by the detection means. A line of sight detection device having an irradiation light amount control means, characterized in that the irradiation light amount of the illumination means is controlled by a control means. (2) The eyeball of the subject is illuminated by an illumination means, and the detection means detects the imaging position of a corneal reflection image based on light reflected from the cornea of the eyeball of the illumination means and an iris image of the eyeball on a predetermined plane. A line of sight detection having an irradiation light amount control means, characterized in that when detecting the line of sight of the subject using an output signal from the detection means, the amount of irradiation light of the illumination means is controlled by a switch means. Device. (3) The amount of light irradiated to the eyeball by the illumination means is small before the detection of the corneal reflection image by the detection means, and after the detection, the eyeball is irradiated with a predetermined amount of light. A line of sight detection device having an irradiation light amount control means.