Eye movement measurement device and eye movement measurement method

Abstract

To suppress effect of head motion when calibration is performed using a wearable measurement device.SOLUTION: An ocular movement measurement device includes: an imaging part fixed to a head of a subject to image an eyeball of the subject; a projection part fixed to the head of the subject and projecting a plurality of calibration targets in projection positions different from one another in a specific direction from a position fixed to the head of the subject; and a correction part for using a relation between an inter-target distance from a projection position of a first calibration target which is projected by the projection part to a projection position of a second calibration target and a measurement value of ocular movement which is performed by the subject in response to change to projection of the second calibration target from the first calibration target to determine a correction function for correcting the measurement value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an eye movement measurement device and an eye movement measurement method.

Background Art

[0002] As a means for exploring the internal state of a subject, there is a means for measuring microsaccades, which are one of the minute eye movements (for example, Patent Documents 1-2). For example, it has been reported that the occurrence frequency of microsaccades increases as visual attention moves, while the occurrence frequency of microsaccades decreases as visual attention is concentrated. Utilizing such properties, for example, by measuring the occurrence frequency of microsaccades, etc., it is possible to determine whether the subject is concentrating visual attention on the object at which the line of sight is directed and observing it, or whether the subject is merely looking at it blankly (in a state of not concentrating attention), and it is possible to explore the internal state of the subject.

[0003] As a method for measuring microsaccades, for example, there is a method of obtaining the frequency, size, speed, direction, etc. of eye movements by analyzing an image of the eye captured using a small high-speed camera or the like. When microsaccades are measured by such a method, in addition to geometric conditions such as the imaging distance and the lens angle of view, fluctuations in detection sensitivity due to the influence of noise components may occur. For example, the measured value is often about 10 to 20% smaller than the true value. Also, the degree of influence of noise may change depending on the imaging conditions and the characteristics of the subject (such as the contrast of the subject's eyes). Therefore, calibration is performed in advance to obtain a correction coefficient, and the measured value of microsaccades is corrected.

[0004] During calibration, a specific mark, such as a circle, is displayed as a calibration target (hereinafter simply referred to as "target") at a known location on a display or in real space. The subject observes the movement of their eyes by observing a target displayed at one location from a target displayed at another location. The amount of eye rotation (amount of pupil movement) is detected as a measurement value from the image, and correction conditions are determined so that the detected measurement value matches the distance between the targets. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 6948688 [Patent Document 2] Patent No. 6902075 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, when using a wearable measuring device worn on the head to image the eyeballs, only eye movements excluding head movements are detected. This presented a problem: proper calibration could not be performed unless the head was fixed in place.

[0007] This invention has been made in view of the above circumstances, and aims to provide an eye movement measurement device and an eye movement measurement method that can suppress the influence of head movement when performing calibration using a wearable type measuring device. [Means for solving the problem]

[0008] The eye movement measuring device of the present invention is fixed to the head of a subject and includes an imaging unit that images the subject's eyeballs, and a unit that is fixed to the head of the subject and positioned relative to the head of the subject. The projection surface not fixed to the head of the subjectThe system includes a projection unit that projects multiple calibration targets to different projection positions, and a correction unit that determines a correction function to correct the measured values ​​using the relationship between the inter-target distance, which is the distance from the projection position of the first calibration target projected by the projection unit to the projection position of the second calibration target, and the measured values ​​of eye movements performed by the subject in response to the change in projection from the first calibration target to the second calibration target.

[0009] The present invention relates to an eye movement measurement method performed by an eye movement measurement device, wherein the imaging unit is fixed to the head of a subject and images the subject's eyeballs, and the projection unit is fixed to the head of the subject and projects from a position fixed to the head of the subject. The projection surface not fixed to the head of the subject Multiple calibration targets are projected at different projection positions, and the correction unit determines a correction function to correct the measured values ​​using the relationship between the inter-target distance, which is the distance from the projection position of the first calibration target projected by the projection unit to the projection position of the second calibration target, and the measured values ​​of eye movements performed by the subject in response to the change in projection from the first calibration target to the second calibration target. [Effects of the Invention]

[0010] According to the present invention, the influence of head movement can be suppressed when performing calibration using a wearable measuring device. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram showing the configuration of the eye movement measuring device 1 according to an embodiment. [Figure 2A] This figure shows an example of an eye movement measurement device 1 according to an embodiment being worn by a subject. [Figure 2B] This figure shows an example of the eye movement measurement device 1 according to the embodiment projecting a target. [Figure 2C]It is a diagram showing an example in which the eye movement measurement device 1 according to the embodiment projects a target. [Figure 3] It is a block diagram showing the configuration of the computer 40 according to the embodiment. [Figure 4] It is a diagram showing an example of a projection surface on which a target according to the embodiment is projected. [Figure 5] It is a flowchart showing the flow of processing performed by the computer 40 according to the embodiment. [Figure 6] It is a diagram showing an example of a projection surface on which a target according to Modification 1 of the embodiment is projected. [Figure 7] It is a diagram showing an example of a projection surface on which a target according to Modification 2 of the embodiment is projected. [Figure 8] It is a diagram showing an example of a projection surface on which a target according to Modification 3 of the embodiment is projected. [Figure 9A] It is a diagram for explaining the effects of the embodiment. [Figure 9B] It is a diagram for explaining the effects of the embodiment.

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0013] (Configuration of the eye movement measurement device 1) FIG. 1 is a block diagram showing a configuration example of an eye movement measurement device 1 according to an embodiment. The eye movement measurement device 1 is a system for measuring eye movements. In the eye movement measurement device 1, calibration is performed before measuring eye movements. The calibration here is a process of determining a correction coefficient for correcting measurement values. For example, in calibration, a correction coefficient is determined such that the amount of pupil movement when observing a target displayed at one position from a target displayed at another position corresponds to the actual distance between the targets.

[0014] The eye movement measurement device 1 includes, for example, an imaging unit 10, a projection unit 20, and a computer 40. The imaging unit 10 images the eyeball G. The projection unit 20 projects a target 32 for calibration onto the projection surface 31. The computer 40 controls the imaging unit 10 and the projection unit 20.

[0015] The imaging unit 10 is, for example, a small high-speed camera. The imaging unit 10 includes, for example, a lighting unit 11, an imaging lens 12, an infrared filter 13, and an image sensor 14. The lighting unit 11 includes an LED (Light Emitting Diode) that irradiates infrared rays and illuminates the area of the eye including the subject's eyeball with infrared rays.

[0016] In the present embodiment, the LED provided in the lighting unit 11 is, for example, a device that emits invisible infrared light (infrared rays) with a wavelength of 770 nm. When visible light (instead of infrared light) is used for illumination, the subject may react to the light of the illumination, that is, the iris closes to change the size of the pupil and the position of the pupil changes to avoid the light because the amount of light entering the pupil decreases. Alternatively, since there is a possibility that the subject may be distracted by the light of the illumination, it becomes impossible to measure the eye movement that occurs in a natural state corresponding to the observed subject, which is used to estimate the psychological state of the subject in the observation of the object. For this reason, in the present embodiment, in order to measure the eye movement without being affected by the irradiation light, infrared light with an invisible wavelength is used for illuminating the eyeball.

[0017] The imaging lens 12 is a small imaging lens for imaging the eyeball from a short distance, and forms an image of the reflected light (reflected infrared light) from the eyeball, which is the subject, on the imaging surface of the image sensor 14 described later.

[0018] The infrared filter 13 is an optical filter that transmits infrared light with an invisible wavelength and blocks light with a visible light wavelength. In the present embodiment, for example, an optical filter with a cut-off wavelength of 700 nm is used.

[0019] The image sensor 14 is a device that converts the brightness and darkness of light illuminating the imaging surface into electrical signals and outputs them as image data. Examples include a CCD (Charge Coupled Device) sensor and a CMOS (Complementary Metal Oxide Semiconductor) sensor. For example, the image sensor 14 outputs frame images, which are images captured at a predetermined frame period, as a continuous moving image to the computer 40.

[0020] The projection unit 20 is, for example, an image projector. The projection unit 20 comprises, for example, a plurality of LEDs 21 (LEDs 21-1 to 21-3, ...) and a projection lens 22. The LEDs 21 emit light. The projection lens 22 causes the light emitted by the LEDs 21 to form an image on the projection surface 31, thereby creating a bright spot, which corresponds to the image of the target 32. Each of the plurality of LEDs 21 is configured to project the target 32 ​​to a different projection position from each other.

[0021] Alternatively, the projection unit 20 may be configured to project targets 32 to different projection positions by changing the projected image.

[0022] In this embodiment, the imaging unit 10 is fixed to the subject's head. In other words, the imaging unit 10 is a wearable imaging device that is worn on the head.

[0023] In this case, the imaging unit 10 changes its imaging direction relative to the global coordinate system in conjunction with the movement of the subject's head. Therefore, even if the subject is observing the same direction, the direction of the pupil as seen from the imaging unit 10 will change depending on the orientation of the subject's head. For example, if a subject looks at a target displayed at one position and then at another, the amount of pupillary movement will be detected as a different value depending on whether the subject changes the orientation of their head to observe the target at the other position or does not change the orientation of their head. It is difficult to uniquely determine the relationship between the distance between targets and the amount of pupillary movement by simply measuring with a wearable imaging device. This has resulted in the problem that correct calibration cannot be performed.

[0024] One possible solution is to detect the amount of head movement of the subject and correct the amount of pupil movement based on that movement. However, this would require the addition of a device, such as a field-of-view camera, to detect head movement, which is not essential for normal eye movement. This would increase costs. Furthermore, there is a possibility that errors will occur and noise will be introduced when correcting pupil movement based on head movement.

[0025] Alternatively, as shown in Figure 9A, measures could be taken to fix the subject's head in place to prevent head movement. However, this would require a device to fix the head. Furthermore, forcing the subject into an unnatural posture would make it difficult to move the pupil smoothly, potentially leading to unstable measurements and increased errors.

[0026] Alternatively, as shown in Figure 9B, a measure can be taken to fix the target to the subject's head. For example, a rod-like device could be attached to the head mount, and the target could be attached to the end of the rod. In this way, the target could be positioned in a specific direction relative to the orientation of the subject's head while wearing the head mount. This would allow the target to be shown regardless of whether the subject moves their head or not, without restraining the subject, but it would be a large and cumbersome device, leaving problems such as the target becoming cumbersome to handle and the weight increasing.

[0027] Therefore, in this embodiment, the projection unit 20 is fixed to the subject's head. In other words, the projection unit 20 is a wearable projection device that is worn on the head.

[0028] In this case, the imaging unit 10 changes its projection direction in conjunction with the movement of the subject's head. When the subject changes the orientation of their head to view the target, the projection position of the target changes, resulting in the observation of a target with a changed projection position, causing the pupil to move according to the distance between the targets. When the subject tries to view the target without changing the orientation of their head, the pupil moves according to the distance between the targets. In other words, regardless of whether the subject moves their head or not, they observe the target by moving their pupil according to the distance between the targets. Even when performing measurements with a wearable imaging device, it becomes possible to uniquely identify the relationship between the distance between targets and the amount of pupil movement, enabling correct calibration. Moreover, by using a small projection device as the projection unit 20, handling becomes even easier, reducing the burden on both the experimenter and the subject.

[0029] Figure 2A shows an example of the eye movement measurement device 1 being attached to a subject. As shown in Figure 2A, the imaging unit 10 and the projection unit 20 are fixed to the subject's head H. This configures the projection unit 20 to emit light from a fixed position on the subject's head H.

[0030] Figures 2B and 2C show examples of projecting a target. Figure 2B shows an example where the subject's head is facing forward. Figure 2C shows an example where the subject's head is turned to the left relative to the front. As shown in Figure 2B, when the subject's head is facing forward, the target 32 ​​is projected onto the projection surface 31 facing forward. As shown in Figure 2C, when the subject's head is turned to the left, the projection unit 20 projects the target 32 ​​onto the projection surface 31 facing left relative to the front. In this way, in this embodiment, the position where the target 32 ​​is projected (projection position) can be changed according to the orientation of the subject's head. Therefore, it is possible to suppress the influence of head movement when performing calibration using a wearable measuring device.

[0031] Figure 3 is a block diagram showing the configuration of a computer 40 according to an embodiment. The computer 40 includes, for example, a communication unit 41, a storage unit 42, and a control unit 43. The communication unit 41 communicates with the imaging unit 10 and the projection unit 20. The storage unit 42 stores, for example, a correction coefficient 420. The correction coefficient 420 is information indicating a correction coefficient determined by calibration.

[0032] The storage unit 42 is a storage medium such as an HDD (Hard Disk Drive), flash memory, EEPROM (Electrically Erasable Programmable Read Only Memory), RAM (Random Access Read / Write Memory), ROM (Read Only Memory), or a combination thereof. The storage unit 42 stores programs for executing various processes of the computer 40, as well as temporary data used when performing these processes.

[0033] The control unit 43 includes, for example, an acquisition unit 430, a projection control unit 431, and a correction unit 432. Each of these functional units of the control unit 43, namely the acquisition unit 430, the projection control unit 431, and the correction unit 432, is realized by having the CPU (Central Processing Unit) provided as hardware in the computer 40 execute a program.

[0034] The acquisition unit 430 acquires various types of information. For example, the acquisition unit 430 acquires images captured by the imaging unit 10 via the communication unit 41. The acquisition unit 430 outputs the acquired images to the correction unit 432.

[0035] The projection control unit 431 controls the projection unit 20 and controls the projection position of the target 32 ​​to be projected onto the projection surface 31.

[0036] Here, using Figure 4, we will explain how the projection control unit 431 controls the projection position. Figure 4 is a diagram showing an example of a projection surface onto which a target according to the embodiment is projected. As shown in Figure 4, the projection control unit 431 controls the projection unit 20 so that, for example, targets 32 (targets 32-1 to 32-4) are projected onto each of the positions that are the vertices of a square with a constant side length (angular distance Dt).

[0037] For example, the projection unit 20 has four LEDs 21, each corresponding to a position that will be a vertex of the square. The projection unit 20 makes the light beam closer to parallel light by positioning the LEDs 21 on the surface of the projection lens 22 that is closer to the focal plane. The projection control unit 431 switches the four LEDs 21 on and off. This allows the target 32 ​​to be projected sequentially onto each of the positions that will be a vertex of the square.

[0038] Furthermore, if an aperture is positioned between the LED 21 and the projection lens 22 in the projection unit 20, the projection control unit 431 may adjust the amount of light that has been brought closer to parallel light by the projection lens 22 using the aperture. This allows the projection control unit 431 to control the size of the target 32 ​​to be projected onto the projection surface 31.

[0039] Returning to Figure 3, the correction unit 432 determines the correction coefficient. The correction unit 432 determines the correction coefficient using the relationship between the projection position of the target 32 ​​projected by the projection unit 20 and the measured value of the eye movement performed by the subject in accordance with the projected target 32. The correction unit 432 calculates the measured value of the eye movement by analyzing the image showing the eye movement projected by the imaging unit 10. Any method can be used to calculate the measured value of the eye movement, but for example, the imaging area in which the pupil is captured is identified based on the brightness value of each pixel in the frame image, and the amount of pupil movement calculated based on the amount of change in the identified imaging area according to the frame image is used as the measured value of the eye movement.

[0040] Here, we will explain how the correction unit 432 determines the correction coefficient using Figure 5. Figure 5 is a flowchart showing the processing flow performed by the computer 40 according to this embodiment.

[0041] Here, calibration is performed by projecting target 32 ​​in the order of target 32-4, 32-1, 32-2, and 32-3 onto the vertices of the square shown in Figure 4.

[0042] The projection control unit 431 of the computer 40 lights up LED-4, which is the LED 21 corresponding to target 32-4 (step ST10). As a result, target 32-4 is projected onto the projection surface 31. The subject observes target 32-4 projected onto the projection surface 31 (step ST11). The imaging unit 10 captures the subject's eyeballs as they observe target 32-4 and outputs the captured images to the computer 40.

[0043] The correction unit 432 of the computer 40 initializes the pupillary cumulative displacement amount S and sets the pupillary cumulative displacement amount S to 0 (zero) (step ST12). The correction unit 432 also initializes the variable N and sets the variable N to 1 (step ST13).

[0044] The projection control unit 431 lights up LED-N, i.e., LED 21 corresponding to target 32-N (step ST14). Here, N is an integer from 1 to 3. As a result, target 32-N is projected onto the projection surface 31. The subject observes target 32-N projected onto the projection surface 31 (step ST15). The imaging unit 10 captures the subject's eyeballs as they observe target 32-N and outputs the captured image to the computer 40.

[0045] The correction unit 432 measures the pupillary displacement D# (step ST16). For example, by analyzing the image obtained in step ST11, the correction unit 432 identifies the imaging area (referred to as the first region) in which the pupil of the subject observing target 32-4 was captured. The correction unit 432 also identifies the imaging area (referred to as the second region) in which the pupil of the subject observing target 32-1 was captured by analyzing the image obtained in step ST15. The correction unit 432 calculates the change in pixel coordinates between the first and second regions and defines the pupillary displacement D# as a value corresponding to the calculated change.

[0046] The correction unit 432 adds the absolute value of the pupillary displacement amount D# calculated in step ST16 to the integrated pupillary displacement amount S (step ST17). The correction unit 432 also increments the variable N and adds 1 to the variable N (step ST18).

[0047] The computer 40 determines whether the variable N is greater than 4 (step ST19). If the computer 40 determines that the variable N is less than 4, it returns to step ST14 and continues the calibration.

[0048] On the other hand, if the variable N is greater than 4, the correction unit 432 calculates the correction coefficient α using the following formula (1) (step ST19) and terminates the process.

[0049] α = S / 4 / Dt …(1) However, α is a correction factor. S is the cumulative pupillary displacement. Dt is the angular distance.

[0050] In the above explanation, we have illustrated the case in which the correction unit 432 calculates the correction coefficient α. However, the correction unit 432 only needs to determine the correction conditions for correcting the measured value, and may be configured to determine a function such as a correction formula, for example.

[0051] Furthermore, although the above example illustrates the case where the target 32 ​​is projected onto the positions corresponding to the vertices of a square, the system is not limited to this. The projection control unit 431 may also project the target 32 ​​onto the positions corresponding to each vertex of a rectangle. In this case as well, the correction unit 432 can determine a correction coefficient according to the angular distance Dt from the projection position of one target 32 ​​to the projection position of another target 32.

[0052] As described above, the eye movement measuring device 1 of this embodiment comprises an imaging unit 10, a projection unit 20, and a correction unit 432. The imaging unit 10 is fixed to the subject's head and images the subject's eyeballs. The projection unit 20 is fixed to the subject's head and projects a plurality of targets 32 (calibration targets) in a specific direction from a fixed position relative to the subject's head. The correction unit 432 determines a correction coefficient α. The correction unit 432 determines the correction coefficient α using the distance between targets and the relationship between the measured values ​​of eye movements performed by the subject in response to a change in projection from one target 32 ​​to another target 32. The distance between targets is the distance from the projection position of one target 32 ​​(first calibration target) projected by the projection unit 20 to the projection position of another target 32 ​​(second calibration target).

[0053] As a result, the eye movement measuring device 1 of the embodiment can change the projection position of the target 32 ​​according to the orientation of the subject's head. Therefore, regardless of whether the subject moves their head or not, the target 32 ​​can be observed in such a way that the pupil moves according to the distance between the targets. Thus, it is possible to suppress the influence of head movement when performing calibration using a wearable measuring device.

[0054] Furthermore, in the eye movement measuring device 1 of this embodiment, the projection unit 20 is an image projector, and the projection position of the target 32 ​​is changed by changing the projected image. As a result, the eye movement measuring device 1 of this embodiment can project the target 32 ​​to any projection position.

[0055] Furthermore, in the eye movement measuring device 1 of this embodiment, the projection unit 20 is equipped with a plurality of LEDs 21 (a plurality of light sources corresponding to a plurality of calibration targets projected in different directions) whose projection positions are different from each other, and the projection position on which the target 32 ​​is projected is changed by switching the LEDs 21 to light up. As a result, in the eye movement measuring device 1 of this embodiment, the target 32 ​​can be projected to a predetermined projection position by the simple process of switching the LEDs 21 to light up.

[0056] Here, we will describe some modifications of the embodiment. Generally, it is known that the human field of view is approximately 200 degrees horizontally and 125 degrees vertically. The effective field of view, which is superior in information reception ability, is approximately 30 degrees horizontally and 20 degrees vertically. Furthermore, the stable field of fixation, where the point of fixation appears quickly and stably, is approximately 60 to 90 degrees horizontally and 45 to 70 degrees vertically. From these properties, it is thought that the human eye has the property that it is easier to move the pupil horizontally than vertically. It is also thought that it is more difficult to move the pupil within the field of view range compared to the range of the stable field of fixation. For this reason, the degree of discrepancy between the amount of pupil movement and the distance between targets may differ between the vertical and horizontal directions. In addition, it is thought that it is easier to move the pupil relatively small, but more difficult to move it large.

[0057] In the modified embodiment, taking these properties into consideration, the system is configured to calculate different correction coefficients when the projection position of the target 32 ​​is moved horizontally and when it is moved vertically. Furthermore, the system is configured to calculate correction coefficients that take into account when the pupil is moved a large amount and when it is moved a small amount.

[0058] (Modification of Embodiment 1) A modification 1 of the embodiment will be described using Figure 6. Figure 6 is a diagram showing an example of a projection surface 31 on which a target is projected according to modification 1 of the embodiment. This modification differs from the embodiment described above in that the projection control unit 431 projects the target 32 ​​along the horizontal direction. The correction unit 432 determines a correction coefficient α in the horizontal direction based on the relationship between the angular distance Dt between targets in the horizontal direction and the amount of pupil movement in the horizontal direction. The method for determining the correction coefficient α can be the same as in the embodiment.

[0059] (Modified embodiment 2) A second modification of the embodiment will be described using Figure 7. Figure 7 shows an example of a projection surface 31 on which a target is projected according to the second modification of the embodiment. This modification differs from the embodiment described above in that the projection control unit 431 projects the target 32 ​​along the vertical direction. The correction unit 432 determines a correction coefficient α in the vertical direction based on the relationship between the angular distance Dt between targets in the vertical direction and the amount of pupil movement in the vertical direction. The method for determining the correction coefficient α can be the same as in the embodiment.

[0060] In the modified example 2, the correction unit 432 may calculate the correction coefficient α by distinguishing between the case where the pupil is moved upward and the case where the pupil is moved downward.

[0061] Furthermore, generally speaking, the human pupil has the property of being more difficult to move in an oblique direction compared to the horizontal and vertical directions. For this reason, it is preferable that the projection control unit 431 does not project the target 32 ​​in a direction that is oblique to the horizontal and vertical directions.

[0062] (Modification of Embodiment 3) Here, a third modification of the embodiment will be described using Figure 8. Figure 8 is a diagram showing an example of a projection surface 31 on which a target is projected according to the third modification of the embodiment. In this modification, a weighting coefficient is set according to the distance between targets. The correction unit 432 multiplies the distance between targets by the weighting coefficient according to the distance between targets. For example, the correction unit 432 multiplies the angular distance Dt1, which is relatively large, by a relatively small weighting coefficient. On the other hand, the correction unit 432 multiplies the angular distance Dt2, which is relatively small, by a relatively large weighting coefficient. The correction unit 432 determines the correction coefficient α using the distance between targets multiplied by the weighting coefficient. The method for determining the correction coefficient α can be the same as in the embodiment.

[0063] As described above, in the eye movement measuring device 1 according to the modified embodiment 1, the projection unit 20 changes the projection position along the vertical direction. As a result, the eye movement measuring device 1 according to the modified embodiment 1 can calculate the correction coefficient α when the pupil is moved in the vertical direction. Furthermore, in the eye movement measuring device 1 according to the modified embodiment 2, the projection unit 20 changes the projection position along the horizontal direction. As a result, the eye movement measuring device 1 according to the modified embodiment 2 can calculate the correction coefficient α when the pupil is moved in the horizontal direction. Therefore, a correction coefficient α can be calculated that distinguishes between cases where the pupil is moved vertically and cases where it is moved horizontally.

[0064] Furthermore, in the modified eye movement measuring device 1 of the embodiment, the projection unit 20 does not change its projection position in directions oblique to the vertical and horizontal directions. As a result, the modified eye movement measuring device 1 of the embodiment can calculate a correction coefficient α that excludes cases where the pupil moves in an oblique direction.

[0065] Furthermore, in the eye movement measuring device 1 according to the third modified embodiment, the correction unit 432 determines the correction coefficient α using a value obtained by multiplying the measured value by a weighting coefficient corresponding to the distance between targets. As a result, the eye movement measuring device 1 according to the third modified embodiment can calculate a correction coefficient α corresponding to the distance between targets.

[0066] In the embodiments and variations thereof described above, the projection unit 20 may be configured to be detachable. The projection unit 20 is only necessary during calibration and is not needed when actually measuring eye movements. Therefore, the projection unit 20 is attached only during calibration and detached during actual measurement. This improves convenience during actual measurement. For example, the projection unit 20 can be attached to the head mount using a magnet. This makes it possible to easily attach and detach the projection unit 20.

[0067] Furthermore, from a safety standpoint, LED21 may be a regular visible light emitting LED instead of a laser diode. Also, to concentrate the luminous beam of target 32 ​​into a narrow angle, it is preferable to use an LED with a small half-angle of maximum power or a point light source LED. For example, the TLCR5800 from Vishay® can be used as an LED with a small half-angle of maximum power. For example, the MTPS9062MC-BK from Marktech can be used as a point light source LED.

[0068] The eye movement measurement device 1 and the computer 40 in the above-described embodiment may be implemented entirely or partially by a computer. In that case, the program for implementing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be loaded into the computer system and executed. The term "computer system" here includes hardware such as the OS and peripheral devices. The term "computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, and storage devices such as hard disks built into the computer system. Furthermore, the term "computer-readable recording medium" may also include those that dynamically hold programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or communication lines such as telephone lines, and those that hold programs for a certain period of time, such as volatile memory inside the computer system that acts as a server or client in such cases. The program may be for implementing a part of the functions described above, or it may be a program that can implement the functions described above in combination with a program already recorded in the computer system, or it may be implemented using a programmable logic device such as an FPGA.

[0069] Although embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention. [Explanation of Symbols]

[0070] 1… Eye movement measurement device 10…Imaging Department 20…Projection section 32…Target 40… Computers 431...Projection Control Unit 432...Correction section

Claims

1. An imaging unit fixed to the subject's head and imaging the subject's eyeballs, A projection unit fixed to the subject's head, which projects a plurality of calibration targets at different projection positions onto a projection surface not fixed to the subject's head, from a position fixed to the subject's head, A correction unit determines a correction function to correct the measured values ​​using the relationship between the inter-target distance, which is the distance from the projection position of the first calibration target projected by the projection unit to the projection position of the second calibration target, and the measured values ​​of eye movements performed by the subject in response to the change in projection from the first calibration target to the second calibration target. An eye movement measuring device characterized by being equipped with the following features.

2. The projection unit is an image projector, and by changing the projected image, it changes the projection position of the calibration target. The eye movement measuring device according to feature 1.

3. The projection unit includes multiple light sources corresponding to multiple calibration targets projected in different directions, and the projection position of the calibration targets is changed by switching and illuminating the light sources. The eye movement measuring device according to feature 1.

4. The projection unit changes the projection position of the calibration target along the vertical direction. The eye movement measuring device according to feature 1.

5. The projection unit changes the projection position of the calibration target along the horizontal direction. The eye movement measuring device according to feature 1.

6. The projection unit does not change the projection position of the calibration target in directions oblique to the vertical and horizontal directions. The eye movement measuring device according to feature 1.

7. The correction unit determines the correction function using a value obtained by multiplying the measured value by a weighting coefficient corresponding to the distance between targets. The eye movement measuring device according to feature 1.

8. An eye movement measurement method performed by an eye movement measurement device, The imaging unit is fixed to the subject's head and images the subject's eyeballs. The projection unit is fixed to the subject's head and projects multiple calibration targets at different projection positions onto a projection surface not fixed to the subject's head from a position fixed to the subject's head. The correction unit determines a correction function to correct the measured values ​​using the relationship between the inter-target distance, which is the distance from the projection position of the first calibration target projected by the projection unit to the projection position of the second calibration target, and the measured values ​​of eye movements performed by the subject in response to the change in projection from the first calibration target to the second calibration target. Method for measuring eye movements.

Images