Methods and systems for applying adaptive color rendering on displays

Abstract

A method, computer program, carrier, system, and head-mounted device for applying adaptive color rendering by incorporating the brightness of light wavelengths related to a user's circadian rhythm are disclosed. The method includes receiving gaze tracking information that identifies the gaze vector of a user of the system, and determining corresponding positions of a first region and a second region of the display based on the identified gaze vector. A first color rendering mode is applied to the first region of the display, and a second color rendering mode is applied to the second region of the display. The difference between the first and second color rendering modes lies in the degree of selective adjustment of the brightness of light wavelengths related to the user's circadian rhythm.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of displays. In particular, the present disclosure relates to a method and system for applying adaptive color rendering in relation to luminance of light of wavelengths related to circadian rhythm. BACKGROUND

[0002] A person's circadian rhythm disorder is harmful in several ways. For example, there are indications that such a disorder can lead to a variety of diseases and symptoms, such as myocardial infarction, sepsis, cancer, arrhythmia, diabetes obesity metabolic syndrome, immune disorders, reproductive problems, sleep deprivation, learning deficits, depression, mood swings, body temperature management disorders, etc.

[0003] In order to control or influence the circadian rhythm, different solutions have been proposed in relation to adjusting the luminance of light of wavelengths related to circadian rhythm in displays. These solutions have different drawbacks and deficiencies. For example, adjusting the luminance of wavelengths related to circadian rhythm (mainly blue light) in a display will provide color rendering in the display that can be perceived as distorted and / or unnatural by a user.

[0004] In addition to the above-mentioned diseases and symptoms, there are indications that a lack of light of wavelengths related to circadian rhythm can lead to myopic eye (myopia).

[0005] It is desirable to solve the above-mentioned problems of the prior art. SUMMARY

[0006] It is an object of the present disclosure to mitigate, alleviate, or eliminate, alone or in any combination, one or more of the deficiencies in the prior art.

[0007] This object is achieved by the method, system, computer program and carrier according to the independent claims.

[0008] The dependent claims provide further advantageous features.

[0009] The present disclosure is based at least partly on the realization that, in order to avoid or mitigate that color rendering gives an unnatural color experience to a user, it would be beneficial to implement differentiated adjustment of color rendering in different areas of a display for light of wavelengths related to circadian rhythm.

[0010] According to a first aspect, there is provided a method in a system comprising a display for applying adaptive color rendering in connection with brightness of light of wavelengths related to the circadian rhythm of a user of the system. In the method, gaze tracking information identifying a gaze vector of the user of the system is received, and based on the identified gaze vector, respective positions of a first area of the display and a second area of the display are determined. A first color rendering mode is applied in the first area of the display, and a second color rendering mode is applied in the second area of the display. The first color rendering mode differs from the second color rendering mode in the degree of selective adjustment of brightness of light of wavelengths related to the circadian rhythm of the user.

[0011] By providing the possibility of using different color rendering modes in different areas of the display, different degrees of selective adjustment of brightness of light of wavelengths related to the circadian rhythm can be made in different areas.

[0012] By receiving gaze tracking information identifying a gaze vector of the user, the degree of selective adjustment of brightness of light of wavelengths related to the circadian rhythm in a particular area of the different areas can be based on the position of the particular area relative to where the gaze vector is located, i.e. where the user is looking on the display.

[0013] By “adjustment of brightness” is meant that the brightness is amplified or suppressed (increased or decreased) to be respectively higher or lower than the brightness of the color rendering as it would have been originally without the adjustment.

[0014] By “selective adjustment” is meant that the brightness of light of wavelengths related to the circadian rhythm can be made with no (or at least less) adjustment of light of other wavelengths, i.e. independently (or semi-independently) of the brightness of light of other wavelengths. Furthermore, “selective adjustment of brightness of light of wavelengths related to the circadian rhythm” does not imply that the brightness of light of all wavelengths related to the circadian rhythm needs to be adjusted. It is sufficient to adjust the brightness of light of at least a subset of wavelengths related to the circadian rhythm.

[0015] Furthermore, “light of wavelengths related to the circadian rhythm” does not imply that cases where the light is adjusted for other purposes than the sole (or even main) purpose of influencing the circadian rhythm are to be excluded. Light of wavelengths related to the circadian rhythm can also be related to other purposes. For example, light of wavelengths related to the circadian rhythm is also related to the secretion of dopamine and melatonin by ganglion cells in the human retina. Dopamine has a role in suppressing eye growth. A decrease in dopamine can cause the eye to lengthen, which in turn can cause myopia (near-sightedness). Thus, increasing light related to the circadian rhythm in a display can cause more dopamine to be secreted and thus reduce the risk of myopia.

[0016] The degree of selective adjustment can be based on the degree to which the user perceives the selective adjustment in different regions. This causes the degree of selective adjustment to be higher in one or more of the plurality of different regions in which the degree to which such selective adjustment will be perceived by the user is lower, and the degree of selective adjustment to be lower in one or more of the plurality of different regions in which the degree to which such selective adjustment will be perceived by the user is higher.

[0017] In some embodiments, the respective degree of selective adjustment of the first and second regions is based on the effect that light of the wavelength associated with the circadian rhythm will have on the circadian rhythm when projected onto the corresponding region of the retina of the eye of the user.

[0018] In further embodiments, the respective degree of selective adjustment of the first and second regions is based on the effect that light of the wavelength associated with the circadian rhythm will have on the secretion of dopamine and melatonin when projected onto the corresponding region of the retina of the eye of the user.

[0019] In some embodiments, the first region of the display is located within a boundary angle with the gaze vector, while the second region of the display is located outside the boundary angle with the gaze vector. Thus, the second color rendering mode involves a higher degree of selective adjustment of the luminance of the light of the wavelength associated with the circadian rhythm than the first color rendering mode.

[0020] Ganglion cells in the retina of the eye that are sensitive to light of the wavelength associated with the circadian rhythm and that affect the circadian rhythm typically have the highest density in the part of the retina that is outside the angle with the fovea of the retina. On the other hand, cone cells that record the color of the light typically have the highest density in the part of the retina that is within the angle, and a lower density in the part of the retina that is outside the angle. Thus, by choosing the boundary angle such that light from the second region of the display that is located outside the boundary angle will be projected onto a part of the retina of the eye of the user that includes a higher density of ganglion cells that are sensitive to light of the wavelength associated with the circadian rhythm and that affect the circadian rhythm, a greater effect on the circadian rhythm can be achieved. At the same time, since the cone cells that record the color of the light have a lower density in this part of the retina, the degree to which the user perceives the higher degree of selective adjustment of the second region of the display is lower than the degree to which the user perceives the higher degree of selective adjustment of the first region of the display, light from which will be projected onto a part of the retina of the eye of the user that includes a higher density of cone cells that record the color of the light.

[0021] Furthermore, the ganglion cells in the retina of the eye affect the secretion of dopamine and melatonin when exposed to light. Thus, by choosing the boundary angle such that light from a second region of the display located outside the boundary angle will be projected onto a part of the retina of the user's eye where the density of ganglion cells is higher, a greater impact on the secretion of dopamine and melatonin can be achieved.

[0022] In some embodiments, the first color rendering mode applied in the first region of the display located within the boundary angle with the gaze vector does not involve selective adjustment of the luminance of light of wavelengths related to the circadian rhythm.

[0023] Since the boundary angle is typically chosen such that light from a second region of the display located outside the boundary angle will be projected onto a part of the retina where the density of ganglion cells is higher and the density of cone cells recording the color of the light is lower, the first region of the display will be projected onto a part of the retina where the density of cone cells is higher. Thus, by applying the first color rendering mode in the first region, which does not involve selective adjustment of the luminance of light of wavelengths related to the circadian rhythm, the user will have the unadjusted color rendering in the corresponding first region of the display projected onto the fourth part of the retina that is most relevant for color registration.

[0024] In some embodiments, the first region is the entire region of the display within the boundary angle with the gaze vector.

[0025] In some embodiments, the second region is the entire region of the display outside the boundary angle with the gaze vector.

[0026] In other embodiments, the second region is a region of the display outside the boundary angle with the gaze vector and within an outer angle with the gaze vector, the outer angle being larger than the boundary angle.

[0027] The density of ganglion cells is highest near a peak angle with the fovea. Thus, the second region can be defined as a region of the display between the boundary angle and an outer angle larger than the boundary angle, which corresponds to a part of the retina near the peak angle.

[0028] In further embodiments, the second color rendering mode outside the boundary angle involves maximum selective adjustment of the luminance of light of wavelengths related to the circadian rhythm at a peak angle with the gaze vector larger than the boundary angle.

[0029] Since the density of ganglion cells is highest near a peak angle with the fovea, the second color rendering mode in the second region can be chosen to be the maximum adjustment at an angle corresponding to the peak angle.

[0030] The outer angle can be in the range of 10-90°, preferably 15-60°.

[0031] The peak angle can be in the range of 2-5°, more precisely about 3.5°.

[0032] The boundary angle can be in the range of 0.5-15°, preferably in the range of 1-10°, more preferably in the range of 2-6°.

[0033] In some embodiments, the method further comprises, if the first region and the second region are adjacent to each other, applying a smooth transition from the first color rendering mode to the second color rendering mode along a boundary between the first region and the second region.

[0034] By providing a smooth transition, e.g. by using a gradual transition from a first degree of adjustment of the first color rendering mode to a second degree of adjustment of the second color rendering mode in a region between the first region and the second region, the boundary between the first region and the second region is less apparent to a user.

[0035] In some embodiments, the selective adjustment of the luminance of the light of the wavelengths related to the circadian rhythm involves selectively increasing the luminance during the day and / or selectively decreasing the luminance during the night.

[0036] The adjustment of the luminance of the light of the wavelengths related to the circadian rhythm can differ depending on the application and the intention. For an application used only during the day, increasing the luminance can be sufficient. Also, when the intention is to avoid myopia due to insufficient dopamine secreted by the retinal ganglion cells, increasing the luminance during the day can be sufficient. For an application used only during the night, decreasing the luminance can be sufficient. For an application used both during the day and during the night, aiming at decreasing the luminance can be sufficient.

[0037] The selective adjustment of the luminance can be performed for some or all wavelengths in the range of 280-500 nanometers, preferably in the range of 440-490 nanometers.

[0038] According to a second aspect, there is provided a computer program comprising instructions which, when executed by a processor, cause at least one processor to perform the method of the first aspect.

[0039] Embodiments of the computer program according to the second aspect can e.g. comprise features corresponding to features of any embodiments of the method according to the first aspect.

[0040] According to a third aspect, there is provided a carrier comprising the computer program according to the second aspect, wherein the carrier is one of an electronic signal, optical signal, radio signal and computer readable storage medium.

[0041] Embodiments of the carrier according to the third aspect can for example comprise features corresponding to features of any embodiment of the computer program according to the second aspect.

[0042] According to a fourth aspect, there is provided a system for applying adaptive color rendering in conjunction with brightness of light of wavelengths related to a circadian rhythm of a user of the system. The system comprises a display, a processor, and a memory. The memory contains instructions executable by the processor, wherein the system is operable for: receiving gaze tracking information identifying a gaze vector of a user of the system and determining respective positions of a first region of the display and a second region of the display; applying a first color rendering mode in the first region of the display and a second color rendering mode in the second region of the display. The first color rendering mode and the second color rendering mode differ in the degree of selective adjustment of brightness of light of wavelengths related to the circadian rhythm of the user based on the respective positions of the first region and the second region relative to the gaze vector.

[0043] In some embodiments, the respective degrees of selective adjustment of the first region and the second region are based on an impact that selective adjustment of light of wavelengths related to the circadian rhythm would have on the circadian rhythm when projected onto corresponding regions of the retina of the eye of the user.

[0044] In further embodiments, the respective degrees of selective adjustment of the first region and the second region are based on an impact that selective adjustment of light of wavelengths related to the circadian rhythm would have on the secretion of dopamine and melatonin when projected onto corresponding regions of the retina of the eye of the user.

[0045] In further embodiments, the first region of the display is located within a boundary angle with the gaze vector, while the second region of the display is located outside the boundary angle with the gaze vector. Thus, the second color rendering mode involves a higher degree of selective adjustment of brightness of light of wavelengths related to the circadian rhythm than the first color rendering mode.

[0046] Further embodiments of the system according to the fourth aspect can for example comprise features corresponding to features of any embodiment of the method according to the first aspect.

[0047] According to a fifth aspect, there is provided a head-mounted device comprising a system according to the fourth aspect.

[0048] Embodiments of the head-mounted device according to the fifth aspect can for example comprise features corresponding to features of any embodiment of the system according to the fourth aspect. BRIEF DESCRIPTION OF DRAWINGS

[0049] The foregoing will become clearer from the following more particular description of example embodiments which are illustrated in the following drawings where like reference numerals refer to like parts throughout the several views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments.

[0050] Figures la to lc is a plot showing the density of ganglion cells and cone cells versus the angle from the fovea of the eye.

[0051] Figure 2 is a plot showing the relative diurnal spectral sensitivity versus wavelength.

[0052] Figure 3a and Figure 3b is a schematic of a user’s eye and display relative to an embodiment of a system according to the present disclosure.

[0053] Figures 4a to 4c is a flowchart illustrating an embodiment of a method according to the present disclosure.

[0054] Figure 5 is a block diagram illustrating an embodiment of a system according to the present disclosure.

[0055] Figure 6a and Figure 6b are schematics of embodiments of a head-mounted device and a remote display system, respectively, according to the present disclosure.

[0056] All drawings are schematic, not necessarily to scale, and generally only show the parts that are necessary for the clarification of the respective examples, while other parts can be omitted or only be implied. DETAILED DESCRIPTION

[0057] Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. The apparatus and method disclosed herein can be implemented in any number of ways, and are not limited to the aspects described herein. Like reference numerals refer to like elements throughout.

[0058] The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0059] In the retina of the human eye, there are two different types of light-sensitive cells, namely rod cells and cone cells. Rod cells are more sensitive to light than cone cells and are thus involved in dim light (night vision) vision. Different cone cells are able to react differently to different wavelengths of light and are thus involved in color vision.

[0060] Figure la is a plot showing the density of ganglion cells versus the angle made with the fovea of the eye in the temporal, superior, nasal and medial directions on a logarithmic scale. As can be seen from the plot, the density of ganglion cells (number of cells per deg 2 increases with increasing angle from the fovea, reaches a maximum at an angle of about 3.5° from the fovea and then decreases again as the angle increases. The increase is similar in all directions. Figure lb is a plot showing the density of cone cells versus the angle made with the fovea of the eye on a logarithmic scale. On the other hand, the density of cone cells (number of cells per deg 2 is highest very close to the centre of the fovea and decreases rapidly at angles from the centre of the fovea that are quite small. For example, the density of cone cells at an angle of 5° from the fovea has decreased to about a tenth of the density compared to the peak at an angle of about 0.2° from the fovea.

[0061] Figure 2 is a plot showing the relative circadian spectral sensitivity versus wavelength. Normalized to 1 at the maximum circadian spectral sensitivity at slightly less than 480 nm, it can be seen from the plot that virtually all circadian efficacy (i.e. the ability to affect the circadian rhythm) is provided by light of wavelengths between 380 and 500 nm. About 79% of the circadian efficacy is provided by light of wavelengths between 440 and 490 nm.

[0062] Ganglion cells are most sensitive to light of wavelengths associated with the circadian rhythm and, when activated, affect the circadian rhythm. Furthermore, as can be seen from Figure la the plot, ganglion cells are typically denser in the part of the retina that is at an angle from the fovea of the retina. At the same time, cone cells that record the colour of light are typically less dense in this part of the retina. Therefore, if light of wavelengths associated with the circadian rhythm is projected onto the part of the retina of the eye of a user where ganglion cells are denser, a greater effect on the circadian rhythm can be achieved. At the same time, since cone cells that record the colour of light are less dense in this part of the retina, the user will not perceive, or at least to a lesser extent, that the light has any particular colour.

[0063] Furthermore, the ganglion cells in the retina of the eye influence the circadian rhythm by affecting the secretion of dopamine and melatonin when exposed to light. Thus, if light of a wavelength related to the circadian rhythm is projected onto a part of the retina of the eye of the user where the ganglion cells have a high density, a large effect on the secretion of dopamine and melatonin can be achieved. At the same time, since the cones cells that register the color of the light have a low density in this part of the retina, the user will not perceive or at least to a lesser extent perceive that the light has any specific color.

[0064] For the eye of the user, projecting light of a wavelength related to the circadian rhythm onto a part of the retina of the eye outside the angle to the fovea can be achieved by using eye tracking to identify the gaze vector of the user and then illuminating the eye in such a way that light is projected onto the part of the retina outside the angle to the fovea based on the gaze vector. For example, in a system comprising a display, the area of the display outside the corresponding angle to the gaze vector can be adjusted so that light of a wavelength related to the circadian rhythm is amplified or suppressed in this area of the display.

[0065] In common applications, the color of the light in a display is provided in order to create a desired color experience for the user. For example, in an image, a movie or a game animation displayed on a display, natural colors or colors that implement a specific mood can be required. Thus, if the color of the light is adjusted so that light of a wavelength related to the circadian rhythm is increased or decreased, the desired color experience will typically not be achieved.

[0066] By adjusting the area of the display outside the corresponding angle to the gaze vector so that light of a wavelength related to the circadian rhythm is emitted from this area of the display, light of the relevant wavelength above or below the nominal luminance can be provided. This is due to the fact that the cones cells that register the color of the light are very low on a part of the retina onto which the light adjusted with respect to the wavelength related to the circadian rhythm will be projected. Thus, the user will not perceive that the light has any specific adjusted color.

[0067] Figure 3a and Figure 3b is a schematic illustration of the eye of the user and the display in relation to an embodiment of the system according to the present disclosure. In particular, Figure 3a The eye of the user 300 is disclosed in cross-section together with the gaze vector 310. Light emitted towards the eye 300 within the boundary angle a will be projected onto a part of the retina within the corresponding angle to the fovea, and light emitted towards the eye 300 outside the boundary angle a and within the outer angle b will be projected onto a part of the retina between several corresponding angles to the fovea. Turning to Figure 3b , a schematic illustration of the display 320 is shown. Based on the gaze vector 310, the area of the display 320 outside the corresponding angle to the gaze vector 310 is adjusted so that light of a wavelength related to the circadian rhythm is amplified or suppressed in this area of the display 320. Figure 3aThe exhibited gaze vector 310, the border angle a and the outer angle b, if the gaze vector of the user is directed towards a point 330 on the display 320 (i.e. the user is looking towards the point 330) and the eye 300 of the user is at a given distance from the display, the border circle (or, if the gaze vector is not parallel to the normal of the display plane of the display, the border ellipse) A α The exhibited gaze vector 310, the border angle a and the outer angle b, if the gaze vector of the user is directed towards a point 330 on the display 320 (i.e. the user is looking towards the point 330) and the eye 300 of the user is at a given distance from the display, the border circle (or, if the gaze vector is not parallel to the normal of the display plane of the display, the border ellipse) A β The exhibited gaze vector 310, the border angle a and the outer angle b, if the gaze vector of the user is directed towards a point 330 on the display 320 (i.e. the user is looking towards the point 330) and the eye 300 of the user is at a given distance from the display, the border circle (or, if the gaze vector is not parallel to the normal of the display plane of the display, the border ellipse) A α The exhibited gaze vector 310, the border angle a and the outer angle b, if the gaze vector of the user is directed towards a point 330 on the display 320 (i.e. the user is looking towards the point 330) and the eye 300 of the user is at a given distance from the display, the border circle (or, if the gaze vector is not parallel to the normal of the display plane of the display, the border ellipse) A α The exhibited gaze vector 310, the border angle a and the outer angle b, if the gaze vector of the user is directed towards a point 330 on the display 320 (i.e. the user is looking towards the point 330) and the eye 300 of the user is at a given distance from the display, the border circle (or, if the gaze vector is not parallel to the normal of the display plane of the display, the border ellipse) A β The exhibited gaze vector 310, the border angle a and the outer angle b, if the gaze vector of the user is directed towards a point 330 on the display 320 (i.e. the user is looking towards the point 330) and the eye 300 of the user is at a given distance from the display, the border circle (or, if the gaze vector is not parallel to the normal of the display plane of the display, the border ellipse) A

[0068] In addition to the border angle a and the outer angle b, a peak angle can be identified, at which the light of the wavelength related to the circadian rhythm has the greatest impact on the circadian rhythm. This is the angle with respect to the gaze vector 310 at which the light is projected onto a portion of the retina that corresponds to the angle with the fovea at the location of the highest density of ganglion cells. Typically, the border angle a and the outer angle b will be defined such that the peak angle is between these two angles.

[0069] Light towards the eye 300 from the display 320 at a given angle with the gaze vector 310 will typically be projected onto the retina at the same or a similar angle with the fovea. In the present disclosure, the border angle a, the outer angle b and the peak angle are defined with respect to the gaze vector 310 of the light towards the eye 300 from the display 320. As long as the angle of the gaze vector 310 of the light towards the eye 300 is different from the angle with the fovea at which the light is projected onto the retina, the border angle a, the outer angle b and the peak angle with respect to the gaze vector 310 should be adjusted in order to project the light onto the desired region of the retina.

[0070] From the graphs showing the distribution of the density of ganglion cells (peak distribution and cumulative distribution, respectively) Figure la and Figure lc and the graph showing the distribution of the density of cone cells Figure lb the following approximate conclusions can be drawn:

[0071] • If the light of the wavelength related to the circadian rhythm is suppressed or amplified at an angle of 10° and more (border angle a = 10°), approximately 50-80% of the ganglion cells are affected;

[0072] • If the light of wavelengths related to the circadian rhythm is suppressed or amplified at angles of 5° and above (border angle a = 5°), approximately 70-95% of the ganglion cells will be affected, but the user can perceive the suppression or amplification outside the border angle a;

[0073] • If the light of wavelengths related to the circadian rhythm is suppressed or amplified at angles of 2° and above (border angle a = 2°), more than 95% of the ganglion cells will be affected, but the user will most likely perceive the suppression or amplification outside the border angle a.

[0074] The choice of the border angle a is therefore a trade-off between affecting the largest possible proportion of ganglion cells by suppressing or amplifying the light of wavelengths related to the circadian rhythm and avoiding or reducing the user's perception of the adjustment.

[0075] Figures 4a to 4c is a flowchart illustrating an embodiment of a method according to the present disclosure. The method is performed in a system comprising a display and preferably also an eye tracking function. By performing these methods, the application combines color rendering with adjustments of the brightness of light of wavelengths related to the circadian rhythm of a user of the system. First, gaze tracking information identifying a gaze vector of a user of the system is received 410. The gaze tracking information is received from an eye tracking function internal to the system or from an entity external to the system. Based on the identified gaze vector, respective positions of a first region 340 of the display and a second region 350, 360 of the display are determined 420. A first color rendering mode is applied 430 in the first region 340 of the display, and a second color rendering mode is applied 440 in the second region 350, 360 of the display. The first color rendering mode differs from the second color rendering mode in the degree of selective adjustment of the brightness of light of wavelengths related to the circadian rhythm of the user.

[0076] The wavelengths to which the selective adjustment of the brightness is applied are in the range of 380-500 nm, preferably in the range of 440-490 nm.

[0077] When selectively adjusting the brightness of light of wavelengths related to the circadian rhythm, the brightness of light of other wavelengths is typically not adjusted. Furthermore, it is not necessary to adjust the brightness of light of all wavelengths related to the circadian rhythm. Adjusting the brightness of light of only a subset of the wavelengths related to the circadian rhythm can still provide useful results.

[0078] The brightness of light of wavelengths related to the circadian rhythm is adjusted selectively by being amplified or suppressed (increased or decreased) to be higher or lower, respectively, than the brightness of the color rendering as it would have been originally without the adjustment (i.e. relative to a nominal color rendering). This is done to a higher degree in the second region 350, 360 than in the first region 340.

[0079] In general, the respective degree of selective adjustment of the first and second regions 340, 350, 360 is based on the impact that selective adjustment of the light of the wavelengths related to the circadian rhythm will have on the circadian rhythm when the light is projected onto the corresponding region of the retina of the eye of the user. Thus, for example, adjustment by increasing or decreasing the luminance of the light of the wavelengths related to the circadian rhythm will be made mainly in a certain region of the display, the light from which will be projected onto the corresponding region of the retina of the eye of the user, for which region of the retina the greatest impact on the circadian rhythm will be produced by the illumination with light of the wavelengths related to the circadian rhythm or not.

[0080] In general, selective adjustment of the luminance of the light of the wavelengths related to the circadian rhythm involves selectively increasing or amplifying the luminance during the day and selectively decreasing or suppressing the luminance during the night. This is generally the case, for example, to enhance the daily circadian rhythm of a person who is in the same time zone.

[0081] Alternative times of selective adjustment are also envisaged to enhance the circadian rhythm. For example, if a person travels to a time zone different from the one in which he or she normally resides, the selective adjustment can be made on the basis of the time of day of the time zone in which the person normally resides, to maintain a normal circadian rhythm. For this case, the selective adjustment can involve selectively increasing or amplifying the luminance during the day in combination with the time zone in which the person normally resides and not in combination with the time zone in which the person is currently travelling.

[0082] As indicated with respect to Figures la to lc The sensitivity to the wavelengths related to the circadian rhythm and the perception of the colors vary as a function of the angle made with the fovea. More specifically, a limit angle a can be identified, outside which the density of the ganglion cells on the retina that are sensitive to the wavelengths related to the secretion of dopamine and melatonin and / or to the circadian rhythm is relatively high, while the density of the cone cells that record the color of the light is relatively low.

[0083] The first region 340 of the display can be located within the limit angle a made with the gaze vector, and the second regions 350, 360 of the display can be located outside the limit angle a made with the gaze vector 422. Thus, the light emitted from the first region 340 of the display will be projected onto the part of the retina that is within the limit angle a (which corresponds to the region 340 of Figure 3b On this part of the retina, the density of the ganglion cells that are sensitive to the wavelengths related to the secretion of dopamine and melatonin and / or to the circadian rhythm is low, while the density of the cone cells that record the color of the light is the highest. Furthermore, the light emitted from the second regions 350, 360 of the display will be projected onto the part of the retina that is outside the limit angle a (which corresponds to the region 350, 360 of Figure 3bon the retina, the density of ganglion cells sensitive to wavelengths associated with the secretion of melatonin and / or dopamine is highest, while the density of cone cells, which record the color of the light, is very low. Furthermore, the second color rendering mode can then involve a higher degree of selective adjustment 442 of the luminance of the light of wavelengths associated with the circadian rhythm compared to the first color rendering mode. The boundary angle a is in the range of 0.5-15°, preferably in the range of 1-10°, more preferably in the range of 2-6°.

[0084] Although this method does not exclude a selective adjustment of the luminance of the light of wavelengths associated with the circadian rhythm in the first region 340, generally, the first color rendering mode does not involve such a selective adjustment 432. This is because such a selective adjustment would be perceived more by the user in the first region 340, since the light from this region would be projected onto a part of the retina where the density of cells that record the color of the light (cone cells) is highest.

[0085] The first region 340 can for example be the entire region 424 of the display within the boundary angle a with the gaze vector.

[0086] The second regions 350, 360 can for example be the entire region 426 of the display outside the boundary angle a with the gaze vector. In an alternative 428, the second region 350 is a region of the display outside the boundary angle a with the gaze vector and within an outer angle b with the gaze vector (this corresponds to Figure 3b the region 350), wherein the outer angle b is larger than the boundary angle a. The outer angle b is in the range of 10-90°, preferably in the range of 15-60°.

[0087] Furthermore, in 444, the selective adjustment of the luminance of the light of wavelengths associated with the circadian rhythm in the second color rendering mode can vary with the angle, such that the selective adjustment is at a maximum at a peak angle with the gaze vector that is larger than the boundary angle a. The peak angle is in the range of 2-5°, more precisely approximately 3.5°.

[0088] Additionally, if the first region 340 and the second regions 350, 360 are adjacent to each other, a smooth transition 450 from the first color rendering mode to the second color rendering mode can be applied along the border between the first region 340 and the second regions 350, 360. In one example, in a border region starting from within the border angle a and ending outside the border angle a, the degree of selective adjustment gradually increases from the degree of selective adjustment defined according to the first color rendering mode to the degree of selective adjustment defined according to the second color rendering mode. The smooth transition can be implemented in a number of ways. This is intended to make the transition from the first color rendering mode in the first region 340 of the display to the second color rendering mode in the second regions 350, 360 of the display smoother and less noticeable.

[0089] When the user looks to another point of the display, the gaze vector of the user changes. When new gaze tracking information is received 460 identifying the new gaze vector of the user of the system, the first color rendering mode is applied 470 in a third region of the display located within the border angle a from the new gaze vector and the second color rendering mode is applied 480 in a fourth region of the display located outside the border angle a from the new gaze vector.

[0090] In a first alternative, once the third and fourth regions have been identified, the first and second color rendering modes are applied in the third and fourth regions, respectively. Thus, the region of the display having the first color rendering mode will be the border region within the border angle a, with the gaze point of the user located in the middle of the border region, which will depend on the gaze point of the user. The region of the display outside the border angle will have the second color rendering mode.

[0091] In a second alternative, once the third region has been identified, the first color rendering mode is applied in the third region. Further, the first color rendering mode is maintained 472 during a predetermined time after the new gaze tracking information is received in the first region 340 of the display 320 while the first color rendering mode is applied in the third region of the display. During this predetermined time, the second color rendering mode is applied in the part of the fourth region that does not overlap with the first region 340 (and the third region). When the predetermined time after the new gaze tracking information is received has passed, the first color rendering mode is applied in the third region of the display and the second color rendering mode is applied in the fourth region of the display. Thus, the region of the display having the first color rendering mode will first be the border region within the border angle a, with the gaze point of the user located in the middle of the border region. When the user changes the gaze point, the border circle A α will follow the gaze movement of the user, which differs from the first alternative in that the border circle A αthe previous position of the foveal region will still have the first color rendering mode for a predetermined time.

[0092] When the area of the display where the first color rendering mode is applied changes such that the second color rendering mode is applied in that area, the second alternative can be used to reduce the risk that moving the fixation point will cause a perceptible impact at the periphery of the user’s field of view.

[0093] In Figure 5 , an embodiment of a system 500 according to the present disclosure is disclosed. The system 500 is configured for applying adaptive color rendering in conjunction with the brightness of light of a wavelength related to the user’s circadian rhythm, e.g. an embodiment of the method according to the present disclosure can be performed as described in relation to Figure 4a , Figure 4b and Figure 4c . The system 500 comprises a processor 510 and a carrier 520 comprising computer executable instructions 530, e.g. in the form of a computer program, which when executed by the processor 510 cause the system 500 to perform the method of the present disclosure, e.g. perform an embodiment according to Figure 4a , Figure 4b and Figure 4c disclosed. The carrier 520 can e.g. be an electronic signal, an optical signal, a radio signal, a transitory computer readable storage medium and a non-transitory computer readable storage medium. The system 500 further comprises a display 540. The system further preferably comprises an internal eye tracking functionality 550. In an alternative, the eye tracking functionality can be located externally to the system, and then receive and communicate eye tracking information identifying the gaze vector of the user of the system from outside the system, e.g. from a separate eye tracking system.

[0094] The system 500 as presented in relation to Figure 5 may e.g. be implemented in a head mounted device as presented in relation to Figure 6a or a remote display system as presented in relation to Figure 6b .

[0095] Figure 6a A head mounted device 1010 according to one or more embodiments is shown. The head mounted device 1010 is a device that can optionally be adapted to be mounted (or arranged) on the head of a user 1000, as presented in relation to Figure 6aThe head-mounted device 1010 can for example comprise and / or be comprised in a head-mounted display HMD such as a virtual reality (VR) headset, an augmented reality (AR) headset or a mixed reality (MR) headset. The head-mounted device 1010 or HMD comprises a display device 1015. The display device 1015 can be transparent to real-world experiences and non-transparent to virtual-world experiences. The head-mounted device 1010 is configured for applying adaptive color rendering in connection with the brightness of light of wavelengths related to the user's circadian rhythm, for example, embodiments of the method according to the present disclosure can be performed as described in relation to Figure 4a , Figure 4b and Figure 4c The head-mounted device 1010 is configured to provide eye tracker functionality by gaze tracking signals (e.g. indicating gaze direction and / or eye convergence distance) using one or more gaze tracking sensors (not shown). The head-mounted device 1010 is further capable of applying a first color rendering mode in a first area 340 of the display device 1015 and a second color rendering mode in a second area 350, 360 of the display device 1015. According to embodiments described in relation to Figure 4a , Figure 4b and Figure 4c The difference between the first color rendering mode and the second color rendering mode lies in the degree of selective adjustment of the brightness of light of wavelengths related to the user's circadian rhythm of the head-mounted device 1015, according to embodiments described in relation to

[0096] The display device 1015 can for example be a 3D display such as a stereoscopic display. The 3D display can for example comprise glasses equipped with AR functionality. Further, the 3D display can be a volumetric 3D display that is autostereoscopic or automultiscopic, which can mean that they form 3D images visible to the naked eye without the need for stereoscopic glasses or a stereoscopic head-mounted display. Thus, the 3D display can be part of the head-mounted device 1010, as described in relation to Figure 6a

[0097] Figure 6b A remote display system 1020 comprising a display device 1015 is shown according to one or more embodiments. The remote display system 1020 generally comprises a remote display device 1015. The display device 1015 is remote in the sense that it is not located in the vicinity of the user 1000. The remote display system 1020 is configured for applying adaptive color rendering in connection with the brightness of light of wavelengths related to the user's circadian rhythm, for example, embodiments of the method according to the present disclosure can be performed as described in relation to Figure 4a , Figure 4b and Figure 4c ​As disclosed, the remote display system 1020 is configured to provide eye tracker functionality using one or more gaze tracking sensors 1025, by gaze tracking signals (e.g., indicative of gaze direction and / or eye convergence distance). In other words, the remote display system 1020 is configured to provide an indication of what object the user 1000 is looking at and / or an indication of the depth of field the user is looking at / into. The remote display system 1020 is further capable of applying a first color rendering mode in the first region 340 of the display device 1015 and a second color rendering mode in the second region 350, 360 of the display device 1015. According to the embodiments described Figures la to lc and Figure 2 According to the embodiments described, the first color rendering mode and the second color rendering mode differ in the degree of selective adjustment of the luminance of light of wavelengths related to the circadian rhythm of the user of the head-mounted display. The remote display 1015 can be a 3D display that does not require stereoscopic / stereoscopic display glasses or a 3D display that requires stereoscopic display glasses to present the 3D effect to the user. The remote display 1015 can also be a 2D display. The remote display system 1020 can comprise only one eye tracker for both eyes. In other words, the illuminator(s) and image device(s) are arranged to illuminate / read both eyes of the user.

[0098] The person skilled in the art realizes that the present invention is in no way limited to the embodiments described above. On the contrary, many modifications and changes are possible while remaining within the scope of the appended claims.

[0099] Additionally, variations to the disclosed embodiments can become apparent to those of ordinary skill in the art upon reading the foregoing description by virtue of the appended claims. In the claims, the term “comprising” does not exclude the presence of other elements or steps than those listed in the claim. The term “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The term “one” does not exclude the presence of more than one. The term “about” in relation to a geographical location means the location plus or minus 10 km. The term “including” should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. The mere fact that measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The steps of a method or the operations of an apparatus do not have to be performed in the exact order disclosed. The scope of the invention is not limited to the embodiments described herein but can be implemented in any suitable way. Any reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

1. A method of applying adaptive color rendering in conjunction with brightness of light of wavelengths related to a circadian rhythm of a user (1000) of a system (500; 1010; 1020) comprising a display (320; 540; 1015), the method comprising: receiving (410) gaze tracking information identifying a gaze vector (310) of the user of the system; determining (420) respective locations of a first region (340) of the display and a second region (350, 360) of the display based on the identified gaze vector; applying (430) a first color rendering mode in the first region of the display; and applying (440) a second color rendering mode in the second region of the display, wherein the first color rendering mode differs from the second color rendering mode in a degree of selective adjustment of brightness of light of wavelengths related to the circadian rhythm of the user, wherein the first region of the display is located (422) within a boundary angle (a) with the gaze vector and the second region of the display is located outside the boundary angle with the gaze vector, and wherein the second color rendering mode involves (442) a maximum degree of selective adjustment of brightness of light of wavelengths related to the circadian rhythm at a peak angle greater than the boundary angle with the gaze vector; and wherein the peak angle is in a range of 2-5°. The respective degrees of selective adjustment of the first and second regions are based on an impact of the selective adjustment of light of wavelengths related to the circadian rhythm on the circadian rhythm when the light is projected onto corresponding regions of a retina of an eye of the user.

2. The method of claim 1, wherein, The first color rendering mode does not involve (432) selective adjustment of brightness of light of wavelengths related to the circadian rhythm.

3. The method of claim 1, wherein, The first region is (424) an entire region of the display within a boundary angle with the gaze vector.

4. The method of claim 1, wherein, The second region (350, 360) is (426) an entire region of the display outside the boundary angle with the gaze vector.

5. The method of claim 1, wherein, The second region (350) is (428) a region of the display outside the boundary angle with the gaze vector and within an outer angle (b) with the gaze vector, the outer angle being greater than the boundary angle.

6. The method of claim 1, wherein, The outer angle is in a range of 10-60°.

7. The method of claim 6, wherein, The peak angle is 3.5°.

8. The method of claim 1, wherein, The boundary angle is in a range of 0.5-15°.

9. The method of claim 1, wherein, The boundary angle is in a range of 1-10°.

10. The method of claim 9, wherein, The boundary angle is in a range of 2-6°.

11. The method of claim 10, wherein, 12. The method of claim 1, further comprising: if the first region and the second region are adjacent to each other, applying (450) a smooth transition from the first color rendering mode to the second color rendering mode along a boundary between the first region and the second region. ​ 13. The method of claim 1, wherein, The selective adjustment of the luminance of light of wavelengths related to the circadian rhythm involves selectively increasing the luminance during the day and selectively decreasing the luminance during the night.

14. The method of claim 1, wherein, The wavelengths of light for which the selective adjustment of the luminance is performed are in the range of 380-500 nanometers.

15. The method of claim 14, wherein, The wavelengths of light for which the selective adjustment of the luminance is performed are in the range of 440-490 nanometers.

16. A non-transitory computer readable medium comprising instructions (530) that, when executed by at least one processor, cause the at least one processor to perform the method according to any one of claims 1 to 15.

17. A system (500; 1010; 1020) for applying adaptive color rendering in conjunction with brightness of light of a wavelength associated with a circadian rhythm of a user (1000) of the system, the system comprising a display (320; 540; 1015), a processor (510), and a memory, the memory containing instructions (530) executable by the processor, wherein, The system is operable for: receiving gaze tracking information identifying a gaze vector (310) of the user of the system; determining respective locations of a first region (340) of the display and a second region (350, 360) of the display based on the identified gaze vector; applying a first color rendering mode in the first region of the display; and applying a second color rendering mode in the second region of the display, wherein the first color rendering mode and the second color rendering mode differ in the degree of selective adjustment of the luminance of light of wavelengths related to the circadian rhythm of the user, wherein the first region of the display is located within a boundary angle with the gaze vector and the second region of the display is located outside the boundary angle with the gaze vector; wherein the second color rendering mode involves a maximum degree of selective adjustment of the luminance of light of wavelengths related to the circadian rhythm at a peak angle greater than the boundary angle with the gaze vector; and wherein the peak angle is in the range of 2-5°. The respective degrees of selective adjustment of the first and second regions are based on an impact of the selective adjustment of light of wavelengths related to the circadian rhythm on the circadian rhythm when the light is projected onto corresponding regions of the retina of the eye of the user.

18. The system of claim 17, wherein, The first region of the display is located within a boundary angle with the gaze vector and the second region of the display is located outside the boundary angle with the gaze vector, and wherein the second color rendering mode involves a higher degree of selective adjustment of the luminance of light of wavelengths related to the circadian rhythm compared to the first color rendering mode.

19. The system of claim 17, wherein, 20. A head-mounted device (1010) comprising the system according to any one of claims 17-19. ​

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