Light source unit, eyeball tracking system and control method thereof

Abstract

The invention discloses a light source unit, an eyeball tracking system and a control method thereof, and the light source unit comprises at least one light source, a light beam splitter and a phase modulator. The light source is used for emitting illumination beams; the light beam splitter is located in a transmission light path of the illumination light beam and used for carrying out n beam splitting on the illumination light beam to form split light beams, and n is larger than or equal to 2; and the phase modulator is positioned in a light path for transmitting the split light beam, is used for modulating the angle of the split light beam to irradiate the eye area of the user, and is also used for modulating the phase of the split light beam to interfere and overlap in the eye area of the user so as to provide illumination for the eye area of the user. Therefore, in a limited number of light sources, the light supplementing brightness of the eye area is effectively improved, the utilization rate of the light sources is improved, the light source power of the supply system is further reduced, and due to precise dimming of the phase modulator and the increase of the illumination distance, the eye tracker with the gradually increased frame rate and the gradually increased eye box movement range can be better adapted.

Description

Technical Field

[0001] The present invention relates to the technical field of eye tracking, and particularly to a light source unit, an eyeball tracking system and a control method thereof. Background Art

[0002] Eye tracking, also known as gaze tracking, is to estimate the line of sight and / or fixation point of the eye by measuring the eye movement. With the progress of technology, eye tracking technology has been widely applied in various industries. In psychology, it can be used to study the visual attention distribution and visual processing process of people in different tasks, so as to study the psychological process of people; in neuroscience, it can be used to study the neural activities of people, and in the field of computer vision, it can be used to detect the focus points and regions of interest of the human eye on the computer interface, so as to optimize the interface design.

[0003] When an eye tracking product tracks the eye position, a light source is required for auxiliary light filling. At present, mainly an LED light source is used to fill light and illuminate the eye area or form Purkinje spots. However, the problem is that due to the large divergence angle of the light source, most of the light is irradiated on places irrelevant to the eye position, greatly increasing the power consumption of the product. Summary of the Invention

[0004] The present invention provides a light source unit, an eyeball tracking system and a control method thereof, which realizes that a light source unit with lower power can meet the light filling requirements of a device with gradually increasing frame rate and gradually increasing movement range of the eye box, and improves the utilization rate of the light source.

[0005] To achieve the above object, the first aspect embodiment of the present invention proposes a light source unit, including at least one light source, a light beam splitter and a phase modulator;

[0006] The light source is used for emitting an illumination light beam;

[0007] The light beam splitter is located in the optical path of the illumination light beam transmission, and is used for splitting the illumination light beam into n split light beams, where n≥2;

[0008] The phase modulator is located in the optical path of the split light beam transmission, and is used for modulating the angle of the split light beam to irradiate to the user's eye area, and is also used for modulating the phase of the split light beam to interfere and superpose in the user's eye area to provide illumination for the user's eye area.

[0009] Optionally, the split light beam after interference and superposition is reflected by the user's eye area to form Purkinje spots.

[0010] Optionally, the light beam splitter is a fused biconical taper optical splitter or a planar waveguide optical splitter.

[0011] Optionally, the phase modulator is a liquid crystal module or a piezoelectric ceramic.

[0012] Optionally, when there are multiple light sources, they are distributed in a ring shape.

[0013] To achieve the above object, an embodiment of the second aspect of the present invention provides an eye tracking system, including: at least one light source unit, an image collector, and a processor according to any embodiment of the present invention;

[0014] The image collector is used to collect an image of the user's eye area;

[0015] The processor is electrically connected to the image collector, and the processor is used to determine the position of the user's eye area based on the eye area image.

[0016] Optionally, the split beam light after interference superposition is reflected by the user's eye area to form a reflected beam. The image collector is located in the optical path of the transmitted reflected beam and is used to collect the image of the user's eye area. The user's eye area image includes Purkinje spots;

[0017] The processor is used to determine the fixation point based on the user's eye area image.

[0018] Optionally, when there are multiple light source units, the multiple light source units are distributed in a ring shape.

[0019] Optionally, the image collector is one of an infrared camera, a black and white camera, a color camera, an image scanner, or a spot analyzer.

[0020] To achieve the above object, an embodiment of the third aspect of the present invention provides a control method for an eye tracking system, implemented based on the eye tracking system according to any embodiment of the present invention. The control method includes the following steps:

[0021] Control the phase modulator to be in an unmodulated state, and control the image collector to collect the i-th frame image, where i is a positive integer;

[0022] Obtain the i-th frame image, and obtain the position of the user's eye area in the i-th frame based on the i-th frame image;

[0023] Based on the position of the user's eye area in the i-th frame and the modulation relationship, control the phase modulator to be in a corresponding modulation state, where the modulation state is that the split beam light in the user's eye area interferes and superposes, and the rest interferes and cancels each other out.

[0024] Optionally, the control method further includes:

[0025] Control the image collector to collect the (i + 1)-th frame image;

[0026] Obtain the (i + 1)-th frame image and determine the user's fixation point based on the (i + 1)-th frame image.

[0027] According to the light source unit, eye tracking system and their control methods provided by the embodiments of the present invention, the light source unit includes at least one light source, a light beam splitter and a phase modulator; the light source is used to emit an illumination beam; the light beam splitter is located in the optical path of the illumination beam transmission, and is used to split the illumination beam into n split beams, where n ≥ 2; the phase modulator is located in the optical path of the split beam transmission, and is used to modulate the angle of the split beam to irradiate the user's eye area, and is also used to modulate the phase of the split beam to interfere and superpose in the user's eye area to provide illumination for the user's eye area. Furthermore, the supplementary light brightness of the eye area is effectively improved, the utilization rate of the light source is improved, and thus the light source power of the supply system is reduced. Moreover, due to the precise light regulation of the phase modulator, the illumination distance is increased, which can better adapt to the eye tracker with gradually increasing frame rate and gradually increasing eye box movement range, and solves the problems of excessive device power, low light source utilization rate and inability to achieve long-distance illumination.

[0028] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 is a schematic structural diagram of a light source unit provided by an embodiment of the present invention;

[0031] Figure 2 is an arrangement structure diagram of light sources in a light source unit provided by an embodiment of the present invention;

[0032] Figure 3 is a schematic structural diagram of an eye tracking system provided by an embodiment of the present invention;

[0033] Figure 4 is an arrangement structure diagram of a light source unit provided by an embodiment of the present invention;

[0034] Figure 5 is another arrangement structure diagram of a light source unit provided by an embodiment of the present invention;

[0035] Figure 6It is another structural diagram of the light source unit arrangement provided according to an embodiment of the present invention;

[0036] Figure 7 It is still another structural diagram of the light source unit arrangement provided according to an embodiment of the present invention;

[0037] Figure 8 It is another structural diagram of the light source unit arrangement provided according to an embodiment of the present invention;

[0038] Figure 9 It is still another structural diagram of the light source unit arrangement provided according to an embodiment of the present invention;

[0039] Figure 10 It is a flowchart of the control method of the eye tracking system provided according to an embodiment of the present invention;

[0040] Figure 11 It is a flowchart of another control method of the eye tracking system provided according to an embodiment of the present invention. Detailed implementation manners

[0041] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0042] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0043] Figure 1 It is a schematic structural diagram of the light source unit proposed in the embodiment of the present invention. As Figure 1 shown, the light source unit 100 includes at least one light source 10, a beam splitter 11, and a phase modulator 12;

[0044] The light source 10 is used to emit illumination light beams;

[0045] The optical beam splitter 11 is located in the optical path of the illumination beam transmission, and is used to split the illumination beam into n split beams, where n≥2;

[0046] The phase modulator 12 is located in the optical path of the split beam transmission, and is used to modulate the angle of the split beam to irradiate the user's eye area 13, and is also used to modulate the phase of the split beam to interfere and superpose in the user's eye area 13 to provide illumination for the user's eye area 13.

[0047] Among them, the above-mentioned light source unit 100 can be adapted to an eye tracking system. The light source 10 in the light source unit 100 can be one or more. When there are multiple light sources 10, they can be annularly distributed in front of the optical beam splitter. It can be understood that if there is only one light source 10, after the beam splitting of the optical beam splitter 11 and the modulation of the phase modulator 12, a relatively satisfactory illumination area and illumination brightness can be obtained, then the light source 10 can be set to only one. If the illumination area and illumination brightness are insufficient, the number of light sources 10 can be increased to increase the illumination brightness and illumination area. The increased light sources 10 can be annularly arranged around the central light source 10 (exemplarily, as Figure 2 shown).

[0048] Through the setting of the optical beam splitter 11, the illumination beam emitted by the light source 10 is split, and the illumination area is larger than that of the light source 10 itself. Then, through the phase modulator 12, the beam splitting of the optical beam splitter 11 is phase-modulated, so that part of the beams interfere and superpose, and part of the beams interfere and cancel each other. In order to be able to illuminate the user's eye area 13 and be able to illuminate the eyeball part of the user's eye area 13 more brightly, after the phase modulation of the phase modulator 12, the interference and superposition of the eyeball part for the eye area 13 can be achieved to enhance the brightness. In one embodiment, in order to obtain a stronger contrast, the part of the user's eye area 13 other than the eyeball part can be interfered and canceled to reduce the brightness.

[0049] Furthermore, within the same illumination distance and when other structures and parameters are the same, compared with directly illuminating the user's eye area 13 by a single light source, the light source unit proposed in the embodiment of the present invention can focus more of the illumination beam emitted by the light source 10 on the eyeball part in the user's eye area 13, improving the light utilization rate of the light source 10. That is to say, through the use of the optical beam splitter 11 and the phase modulator 12 in the embodiment of the present invention, the brightness effect of the illumination beam of a single light source 10 on the eyeball part in the user's eye area 13 may be equivalent to the brightness effect of directly illuminating the eyeball part in the user's eye area 13 by multiple light sources 10.

[0050] Among them, during the process of modulating the light beam by the above-mentioned phase modulator 13, it can be modulated according to a preset modulation relationship. For example, based on optical path simulation software or experimental testing methods, the voltage or current of the phase modulator 13 can be adjusted, and the modulation phase of the light beam can be detected to fit the modulation relationship. In actual use, the corresponding current or voltage of the phase adjuster 13 can be given according to the required modulation phase, so as to realize the phase modulation of the light beam by the phase modulator 13.

[0051] Thus, the light source unit 100 expands the light beam irradiation area through the optical beam splitter 11, and then concentrates the light source 10 on the user's eye area 13 through the phase modulator 12, realizing the beam expansion of a single light source 10 and the redistribution of brightness after beam expansion. Furthermore, in a limited number of light source units, the supplementary light brightness of the eye area 13 is effectively improved, the utilization rate of the light source 10 is increased, and thus the power of the light source 10 in the supply system is reduced. Moreover, due to the precise dimming of the phase modulator 12, the illumination distance is increased, which can better adapt to products with gradually increasing frame rates and gradually increasing eye box movement ranges, solving the problems of too high device power, low utilization rate of the light source 10, and inability to achieve long-distance illumination.

[0052] Optionally, the user's eye area 13 reflects the split light beams after interference superposition to form Purkinje spots. Thus, the Purkinje spot catcher in the eye tracking system can be used to capture the Purkinje spots to track the fixation point of the user's eye area 13 according to the Purkinje spots.

[0053] Optionally, the optical beam splitter 11 is a fused biconical taper optical splitter or a planar waveguide optical splitter. Among them, the optical splitter can split light according to the splitting ratio, and generally there is a 1*n optical splitter. It can be selected according to the actual situation.

[0054] Optionally, the phase modulator 12 is a liquid crystal module or a piezoelectric ceramic.

[0055] Among them, the liquid crystal phase modulator 12 utilizes the optical properties of liquid crystal materials to change the refractive index of the liquid crystal through the action of an electric field, thereby adjusting the phase of the incident light. Specifically, liquid crystal molecules are molecules arranged in an orderly manner, and an external electric field can change their arrangement. When the liquid crystal molecules are in a disordered state, the light passing through the liquid crystal will not have a phase difference, so the light phase will not change; when the liquid crystal molecules are arranged in an orderly structure, the light passing through the liquid crystal will have a phase difference, thus realizing the phase modulation of the light beam.

[0056] Piezoelectric ceramics have the inverse piezoelectric effect, that is, they can generate micro-displacements corresponding to voltage signals under the application of voltage signals, and have the characteristics of high nanoscale resolution and microsecond-level response speed. They can be used in combination with optical fibers. The optical fiber is wound around the piezoelectric ceramic. When the piezoelectric ceramic undergoes periodic micro-deformation, the length of the optical fiber changes periodically, and the phase of the transmitted light also changes periodically, enabling fine-tuning of the optical phase modulation.

[0057] Figure 3 It is a schematic structural diagram of the eye tracking system proposed in an embodiment of the present invention. The eye tracking system includes: at least one light source unit 100, an image collector 14, and a processor 15 proposed in any embodiment of the present invention;

[0058] The image collector 14 is used to collect images of the user's eye area, and can be an infrared camera, a DVS camera, or a light signal receiver in a MEMS system, etc.;

[0059] The processor 15 is electrically connected to the image collector 14, and the processor 15 is used to determine the position of the user's eye area based on the eye area image.

[0060] Among them, the image collector 14 can be located in the optical path of the reflection and / or scattering of the illumination beam of the light source unit 100 by the user's eye area 13 to capture images of different positions of the user's eye area 13. Exemplarily, when capturing images of the user's eye area 13 based on the reflected and scattered light beams, relatively comprehensive images of the user's eye area 13 and images including the background can be captured. When capturing images of the user's eye area 13 based on the reflected light beam, images of parts with obvious reflection can be captured. When capturing images of the user's eye area 13 based on the scattered light beam, relatively dark parts in the user's eye area can be captured. Thus, the position of the image collector 14 can be set according to corresponding requirements, such as the position of the user's eye area to be captured.

[0061] In one embodiment, the image collector 14 can capture both reflected light and scattered light to obtain images of the user's eye area, and determine the position of the user's eye area through the processing of the processor 15.

[0062] Optionally, the split beam after interference superposition reflected by the user's eye area forms a reflected beam. The image collector 14 is located in the optical path of the transmitted reflected beam and is used to collect images of the user's eye area. The user's eye area image includes Purkinje spots;

[0063] The processor 15 is used to determine the fixation point based on the user's eye area image.

[0064] It can be understood that before the phase modulator 12 modulates the light beam, the light beam can illuminate the entire eye area of the user after being split, and the image collector 14 can capture the entire eye area of the user, and the processor 15 extracts and determines the position of the user's eye area. Then, the phase modulator 12 can modulate the light beam accordingly according to the position of the user's eye area, so that the eyeball part of the user's eye area can receive the split light beams after interference superposition. Thus, the image collector 14 can be located in the reflected light beam formed by reflecting the split light beams after interference superposition in the user's eye area, and can collect the Purkinje spot. Furthermore, the fixation point of the user can be determined.

[0065] Optionally, when there are multiple light source units 100, the multiple light source units 100 can be arranged in a ring distribution, a triangular distribution, a polygonal distribution, an arc distribution or a linear distribution.

[0066] It can be understood that Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 and Figure 9 are four structural diagrams of light source arrangements provided according to an embodiment of the present invention. As Figures 4 to 9 shown, according to requirements such as the supplementary light area and / or the supplementary light brightness, the eye tracking system can include multiple light source units 100, and the multiple light source units 100 can be arranged in a circular, rectangular, rhombic, polygonal, arc-shaped, triangular, etc.

[0067] Among them, when the multiple light source units 100 are arranged in a ring distribution, the distance between the user's eye area and the image collector 14 can be increased. Exemplarily, multiple light source units 100 are arranged at the edge of a display. When the user gazes at the display, the multiple light source units 100 can be arranged in a ring to track the user's fixation point in real time. The multiple light source units 100 share a set of processor 15 and image collector 14.

[0068] Optionally, the image collector 14 is one of an infrared camera, a black and white camera, a color camera, a spot analyzer, and an image scanner.

[0069] Among them, the image collector 14 can be selected according to actual requirements. For example, it can be adapted according to the wavelength band of the light source. If the light source 10 is an infrared light source, the image collector 14 can be an infrared camera or an infrared scanner; if the light source 10 is red, green, or blue monochromatic light, then the image collector 14 can be a black and white camera; if the light source is white light, then the image collector 14 can be a color camera; if it is necessary to focus on analyzing the spot, then the image collector 14 can be a spot analyzer.

[0070] Figure 10It is a flowchart of a control method for an eye tracking system proposed by an embodiment of the present invention. This method is implemented based on the eye tracking system of any embodiment of the present invention. For example, Figure 10 as shown, the control method includes the following steps:

[0071] S101, control the phase modulator to be in an unmodulated state, and control the image collector to collect the i-th frame of image, where i is a positive integer;

[0072] S102, obtain the i-th frame of image, and obtain the position of the user's eye region in the i-th frame based on the i-th frame of image;

[0073] Exemplarily, i = 1. For example, Figure 1 as shown, the light source 10 emits a light beam, and the light beam is split into n light beams by the optical beam splitter 11. Moreover, the irradiation range of the n light beams is sufficient to cover the entire face. The light beam passes through the phase modulator 12 in the unmodulated state and reaches the face, and the light beam reflected by the face is collected by the image collector 14 as the first frame of image. According to the first frame of image collected by the image collector 14, using an image processing algorithm, obtain the position of the region where the user's eye region 13 is located at the first frame moment.

[0074] S103, based on the position of the user's eye region in the i-th frame and the modulation relationship, control the phase modulator to be in the corresponding modulation state, and the modulation state is the interference superposition of the split light beams in the user's eye region, and the interference of the rest part cancels out.

[0075] Among them, after S102, according to the position of the region where the user's eye region 13 is located at the first frame moment, the processor 15 controls the phase modulator 12 through current or voltage, starts the phase modulator 12, changes the phase and propagation direction of the light beam, so that the light beam interferes and superposes in the eye region 13, and fills light for the eye region 13.

[0076] It should be noted that the modulation relationship between the position where the user's eye region 13 is located and the phase modulator 12 can be calibrated in advance. Each region position corresponds to a specific voltage or current, and this data is stored in the processor 15. If it is necessary for the light beam to irradiate to a certain region position, the processor 15 controls the phase modulator 12 to apply the corresponding voltage or current. At this time, the internal structure of the phase modulator 12 changes, corresponding to changing the propagation direction and phase of the light beam, so that the light beam propagates to the required region position. This process can effectively change the propagation direction of the light source 10, improve the utilization rate of the light source 10, and further can reduce the number of light sources 10, reduce the power of the device, and the modulation process is simple, and the device can complete automatically, which is convenient for users to use.

[0077] Optionally, for example, Figure 11 as shown, the control method further includes:

[0078] S104. Control the image collector to collect the (i + 1)-th frame of image;

[0079] S105. Obtain the (i + 1)-th frame of image, and determine the user's fixation point based on the (i + 1)-th frame of image.

[0080] That is to say, after step S103, the reflected light beam of the eye area 13 is collected by the image collector 14 as the second frame of image. The processor 15 can determine the user's fixation point based on the second frame of image collected by the image collector 14 and the Purkinje spot.

[0081] Then, increment i by 1, and continue to execute S104 - S105 to obtain the user's fixation point next time, and finally track the user's eye movement trajectory to obtain the user's fixation line-of-sight curve.

[0082] Since the light source can increase the light intensity through coherent superposition by the phase modulator and determine the supplementary light angle, the processor 15 can calculate the human eye area, so only the human eye area is supplemented with light. The utilization rate of the light source can be greatly improved.

[0083] In summary, according to the light source unit, eye tracking system and its control method proposed in the embodiments of the present invention, the light source unit includes a light source, a light beam splitter and a phase modulator; the light source is used to emit an illumination light beam; the light beam splitter is located in the optical path of the illumination light beam transmission, and is used to split the illumination light beam into n split light beams, n ≥ 2; the phase modulator is located in the optical path of the split light beam transmission, and is used to modulate the angle of the split light beam to irradiate the user's eye area, and is also used to modulate the phase of the split light beam to interfere and superpose in the user's eye area to provide illumination for the user's eye area. It realizes that using a single light source unit can meet the supplementary light requirements of a device with gradually increasing frame rate and gradually increasing eye box movement range, and improves the utilization rate of the light source.

[0084] It should be understood that various forms of the processes shown above can be used, reordering, adding or deleting steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions of the present invention can be achieved, which is not limited herein.

[0085] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A light source unit, characterized in that, it includes at least one light source, an optical beam splitter and a phase modulator; the light source is used for emitting an illumination beam; the optical beam splitter is located in the optical path of the illumination beam transmission, and is used for splitting the illumination beam into n split beams, where n≥2; the phase modulator is located in the optical path of the split beam transmission, and is used for modulating the angle of the split beam to irradiate the user's eye area, and is also used for modulating the phase of the split beam to interfere and superpose in the user's eye area to provide illumination for the user's eye area.

2. The light source unit according to claim 1, characterized in that, the reflected split beam after interference and superposition in the user's eye area forms a Purkinje spot.

3. The light source unit according to claim 1, characterized in that, the optical beam splitter is a fused biconical taper optical splitter or a planar waveguide optical splitter.

4. The light source unit according to claim 1, characterized in that, the phase modulator is a liquid crystal module or a piezoelectric ceramic.

5. The light source unit according to claim 1, characterized in that, when there are multiple light sources, they are distributed in a ring shape.

6. An eye tracking system, characterized in that, it includes: at least one light source unit according to any one of claims 1-5, an image collector and a processor; the image collector is used for collecting an image of the user's eye area; the processor is electrically connected to the image collector, and the processor is used for determining the position of the user's eye area based on the eye area image.

7. The eye tracking system according to claim 6, characterized in that, the reflected split beam after interference and superposition in the user's eye area forms a reflected beam, the image collector is located in the optical path of the reflected beam transmission, and is used for collecting the image of the user's eye area, and the user's eye area image includes a Purkinje spot; the processor is used for determining the fixation point based on the user's eye area image.

8. The eye tracking system according to claim 6, characterized in that, when there are multiple light source units, the multiple light source units are distributed in a ring shape.

9. The eye tracking system according to claim 6, characterized in that, the image collector is one of an infrared camera, a black and white camera, a color camera, an image scanner or a spot analyzer.

10. A control method for an eye tracking system, characterized in that, it is implemented based on the eye tracking system according to any one of claims 6-9, and the control method includes the following steps: controlling the phase modulator to be in an unmodulated state, and controlling the image collector to collect the i-th frame of image, where i is a positive integer; acquiring the i-th frame of image, and acquiring the position of the i-th frame of user's eye area based on the i-th frame of image; controlling the phase modulator to be in a corresponding modulation state based on the position of the i-th frame of user's eye area and the modulation relationship, and the modulation state is that the split beams in the user's eye area interfere and superpose, and the rest interfere and cancel each other.

11. The control method for an eye tracking system according to claim 10, characterized in that, it further includes: controlling the image collector to collect the (i + 1)-th frame of image; Obtain the (i + 1)-th frame image and determine the user's fixation point based on the (i + 1)-th frame image.

Images