WO2013125318A1 - Head mounted display, brightness adjustment method, and control program - Google Patents

Description

Head mounted display, brightness adjustment method, and control program

The present invention relates to a head mounted display, a brightness adjustment method, and a control program.

Conventionally, a head-mounted display that displays an image so as to be visually recognized in front of the user's eyes is known. Hereinafter, the head mounted display is described as HMD. The HMD includes, for example, a liquid crystal unit, an eyepiece optical system, a deflection member, and the like. The liquid crystal unit includes a backlight, for example. The eyepiece optical system is a lens group, for example. The deflection member is, for example, a half mirror. Hereinafter, the half mirror is referred to as HM. The HM makes image light emitted from the liquid crystal unit through the lens group enter the user's eyes. The user can view the external light in front through the HM at the same time. The luminance level of the backlight can be adjusted stepwise at predetermined luminance intervals, for example, with a luminance dial. For example, Patent Document 1 discloses an HMD that can change the brightness of an image in an image display unit in accordance with external illumination.

In the HMD, for example, the user may want to adjust the see-through degree in the HM each time depending on the content displayed on the HM, the usage scene, or the like. For example, in content where you want to see an image firmly, you may want to increase the brightness even in a dark place. In content that allows you to glance at an image, you may want to reduce the brightness even in a bright place. In such a case, the user can adjust the see-through degree in the HM by manually switching the luminance level and adjusting the luminance.

Japanese Patent Laid-Open No. 2004-233908

However, as in the technique described in Patent Document 1, simply changing the luminance of the image according to the change in the external illuminance changes the luminance level each time the external illuminance changes. For this reason, in the technique described in Patent Literature 1, the relationship between the luminance level that is intentionally adjusted by the user and the luminance of the backlight is shifted due to a change in the ambient illuminance. As a result, there is a problem that the see-through degree in the HM changes with a change in the ambient illuminance. Therefore, the user has to adjust the luminance level every time the external environment changes.

An object of the present disclosure has been made to solve the above-described problem, and a head-mounted display and a brightness adjustment method capable of adjusting the brightness of the backlight while maintaining the see-through degree in the display unit when the external illumination changes And providing a control program.

The head mounted display according to the first aspect of the present disclosure is irradiated with light valve elements capable of forming an image with pixels arranged in a matrix, a light source provided in the light valve elements, and the light valve elements. A deflection unit that reflects at least part of the image light to enter the user's eye and transmits at least part of the light from the external real image to enter the user's eye, and illuminance detection that detects the external illuminance According to the illuminance detected by the illuminance detection means for the plurality of luminance levels that can be received by the reception means Thus, the luminance corresponding to one of the luminance levels received by the receiving unit is changed from the plurality of luminance levels in which the luminance of the light source is set. Determining means for determining, and changing means for changing the luminance of the light source to the luminance determined by the determining means, wherein the determining means increases the illuminance detected by the illuminance detecting means toward the brighter side. As the illuminance interval between the luminance levels is wider and the illuminance is darker, the luminance interval between the plurality of luminance levels is narrower, and the ratio of the luminance of the light source to the external illuminance is constant at the same luminance level. The luminance of the light source is determined from the plurality of luminance levels.

In the head mounted display according to the first aspect, the brighter the illuminance in the outside world, the wider the luminance interval between the plurality of luminance levels of the light source. On the contrary, the darker the illuminance in the outside world, the narrower the brightness interval between the plurality of brightness levels of the light source. Furthermore, the ratio of the luminance of the light source to the external illuminance at the same luminance level is always constant. Therefore, even if the external illuminance changes, the ratio of the luminance to the external illuminance at the received luminance level can be maintained, so that the see-through degree in the deflecting unit can be maintained.

Further, in the first aspect, the determining unit multiplies the luminance set for each of the plurality of luminance levels at a predetermined illuminance by a coefficient corresponding to the illuminance detected by the illuminance detecting unit. The luminance corresponding to the plurality of luminance levels corresponding to the illuminance different from the predetermined illuminance may be determined from the set luminance levels. Thereby, even if the illuminance of the outside world changes, the ratio of the luminance to the illuminance of the outside world at the received luminance level can be kept constant, so that the see-through degree in the deflecting unit can be kept constant.

In the first aspect, the illuminance detection means may detect the illuminance of the external environment in the front direction when the illuminance detection means is worn on the user's head. Thereby, the illuminance of the outside world in the user's visual field can be detected well. In other words, the backlight luminance is determined using the illuminance of the outside world in the user's visual field. Therefore, the see-through degree can be kept constant with respect to the real image of the outside world that actually enters the user's eyes.

Further, in the first aspect, the determination unit is provided with a plurality of illuminance ranges for the illuminance detected by the illuminance detection unit, and the luminance corresponding to the plurality of luminance levels is set for each of the illuminance ranges. It is preferable that one of the luminance levels received by the receiving unit is determined from a plurality of luminance levels, and the threshold value of the illuminance range has hysteresis. Thereby, even if the illuminance detected by the illuminance detection means is near the threshold value, it is possible to prevent the luminance from changing repeatedly. Therefore, it is possible to maintain good visibility in the deflection unit.

Further, in the first aspect, the determination unit is provided with a plurality of illuminance ranges for the illuminance detected by the illuminance detection unit, and the luminance corresponding to the plurality of luminance levels is set for each of the illuminance ranges. A threshold passage determination unit that determines a luminance corresponding to the one luminance level received by the reception unit from a plurality of luminance levels, and determines whether or not the illuminance detected by the illuminance detection unit exceeds the threshold; When the threshold passage determining means determines that the illuminance exceeds the threshold, the state determining means determines whether or not the state where the illuminance exceeds the threshold continues for a predetermined time, and the state determining means When it is determined that the state exceeding the threshold has continued for the predetermined time, the luminance is changed to the luminance determined in the illuminance range on the side exceeding the threshold. May and a degree changing means. Thereby, even if the illuminance detected by the illuminance detection means is near the threshold value, it is possible to prevent the luminance from changing repeatedly. Therefore, it is possible to maintain good visibility in the deflection unit.

The brightness adjustment method according to the second aspect of the present disclosure includes a light valve element, a light source provided in the light valve element, and at least a part of image light emitted from the light valve element to reflect the user's eyes. A deflection unit that transmits at least part of the light from the real image of the outside world and enters the user's eyes, an illuminance detection unit that detects the illuminance of the outside world, and a stepwise luminance level of the light source. A brightness adjustment method for a head-mounted display comprising: a receiving unit that receives from the light source according to the illuminance detected by the illuminance detecting unit with respect to the plurality of brightness levels that can be received by the receiving unit. The brightness corresponding to the brightness level corresponding to one of the brightness levels received by the receiving means is determined from the plurality of brightness levels set respectively. When the illuminance detected by the illuminance detection means is brighter, the brightness interval between the plurality of brightness levels is wider, and the darker the illuminance side is, the narrower the interval is and the same brightness level. A determination step of determining the luminance of the light source from the plurality of luminance levels at which a ratio of the luminance of the light source to the ambient illuminance is constant, and a luminance changing step of changing the luminance of the light source to the luminance determined in the determination step With.

In the luminance adjustment method according to the second aspect, since the head-mounted display performs the above steps, the ratio of the luminance with respect to the external illuminance at the received luminance level can be maintained even when the external illuminance changes. The see-through degree can be maintained.

A control program according to a third aspect of the present disclosure includes a light valve element, a light source provided in the light valve element, and at least a part of image light emitted from the light valve element to reflect on a user's eye. A deflection unit that transmits at least part of the light from the real image of the outside world and enters the user's eyes; an illuminance detection unit that detects the illuminance of the outside world; and a stepwise luminance level of the light source from the outside A control program for causing a head mounted display including an accepting unit to function, wherein the computer is configured to respond to illuminance detected by the illuminance detecting unit with respect to a plurality of the brightness levels that can be accepted by the accepting unit. , Corresponding to one of the brightness levels received by the receiving means from the plurality of brightness levels in which the brightness of the light source is respectively set When determining the brightness corresponding to the brightness level, the brighter the illuminance detected by the illuminance detecting means, the wider the brightness interval between the plurality of brightness levels, and the darker the illuminance side, the narrower the interval. And determining the luminance of the light source from the plurality of luminance levels at which the ratio of the luminance of the light source to the ambient illuminance is constant at the same luminance level, and determining the luminance of the light source in the determining step. And a luminance changing step for changing to a different luminance.

Since the control program according to the third aspect causes the computer of the head mounted display to execute each step described above, even when the external illuminance changes, the ratio of the luminance with respect to the external illuminance at the received luminance level can be retained. The see-through degree in the deflection part of the head mounted display can be maintained.

It is a perspective view of the spectacles 91 which attached HMD1. 2 is a plan view of the projection apparatus 100. FIG. FIG. 3 is a cross-sectional view taken along the line II in FIG. 2. It is a block diagram which shows the electric constitution of HMD1. 3 is a conceptual diagram of a luminance determination table 321. FIG. It is a graph which shows the brightness | luminance curve for every illumination intensity range in the brightness | luminance determination table. It is a flowchart of a brightness control process. It is a conceptual diagram of the brightness | luminance determination table 322 which is a modification. It is a graph which shows the luminance curve for every illuminance range in the luminance determination table 322. It is a flowchart of the brightness | luminance control processing which is a modification.

Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. The head mounted display 1 shown in FIG. 1 displays an image so as to be visually recognized as an image in front of the user's eyes. Hereinafter, the head mounted display 1 is described as HMD1. In the following description, the upward direction, the downward direction, the downward diagonal direction to the right, the upward diagonal direction to the left, the upward diagonal direction to the right, and the downward diagonal direction to the left are respectively the upward direction, downward direction, forward direction, and backward direction of HMD1. Right direction, left direction. The downward direction, upward direction, right direction, and left direction in FIG. 2 are the front direction, rear direction, right direction, and left direction of the projection apparatus 100, respectively. The upward direction, downward direction, right direction, and left direction in FIG. 3 are the upward direction, downward direction, right direction, and left direction of the projection apparatus 100, respectively.

The configuration of the HMD 1 will be described with reference to FIGS. As shown in FIG. 1, the HMD 1 includes a projection device 100 and a control device 200. The projection apparatus 100 is used by being mounted on spectacles 91 that are dedicated mounting tools. The projection apparatus 100 may be attached to glasses used by a user on a daily basis. The projection apparatus 100 irradiates the user's eyes with image light. The projection device 100 is detachably connected to the control device 200 via a harness 150. The control device 200 is used by being worn on a user's waist belt, for example. The control device 200 controls the projection device 100.

The configuration of the projection apparatus 100 will be described. As shown in FIGS. 1 and 2, the projection apparatus 100 includes a housing 2. As shown in FIG. 2, the housing | casing 2 is a square cylindrical resin member, and is L shape in planar view. As shown in FIG. 3, the housing 2 contains a projection unit 10. As shown in FIG. 3, the projection unit 10 generates image light and emits it in the left direction through the opening 7 on the left end side of the housing 2. A half mirror holder 5 is fixed to the opening 7 on the left side of the housing 2. Hereinafter, the half mirror holder 5 is referred to as an HM holder 5. The HM holder 5 is made of resin. As shown in FIGS. 1 to 3, the HM holder 5 holds a half mirror 8. Hereinafter, the half mirror 8 is referred to as HM8.

HM8 is made of resin. The HM 8 reflects at least a part of the emitted light such as half of the emitted light of the projection unit 10 and enters the left eyeball of the user (not shown). The user can visually recognize the image superimposed on the real image in his field of view. As shown in FIGS. 1 and 2, a slit 9 </ b> A is provided at the center in the left-right direction on the front surface of the housing 2. A part of the adjuster 16 is exposed in the slit 9A. The user can adjust the focus of an image that can be viewed with the HM 8 by rotating the adjuster 16 in the vertical direction with a finger. A circular small hole 40 is provided on the right side of the HM holder 5 on the front surface of the housing 2. An illuminance sensor 39 is exposed forward in the small hole portion 40. The illuminance sensor 39 can detect the external illuminance in front of the user's visual field, particularly the external illuminance in front of the HM8.

The configuration of the projection unit 10 will be described. As shown in FIG. 3, the projection unit 10 includes a lens holder 15, an adjuster 16, and a liquid crystal holder 17. The lens holder 15 holds the eyepiece optical system 120. The liquid crystal holder 17 holds the liquid crystal device 12. The liquid crystal device 12 includes a backlight 41 and a liquid crystal display 42 shown in FIG. Hereinafter, the liquid crystal display 42 is referred to as an LCD 42. The backlight 41 is an example of a light source. The LCD 42 is an example of a light valve element that forms an image with pixels arranged in a matrix, for example. The liquid crystal device 12 emits image light. The eyepiece optical system 120 accommodates a plurality of lenses (not shown), collects image light emitted from the liquid crystal device 12, and guides it to the opening 7 of the housing 2. Condensing means an optical action that reduces the spread of the image light flux. That is, focusing is not limited to a configuration in which image light is converted into convergent light or parallel light by the eyepiece optical system 120.

The adjuster 16 has a ring shape. The adjuster 16 is attached to the liquid crystal holder 17 by being extrapolated. A spiral groove cam 17 </ b> A is provided on the outer peripheral surface of the liquid crystal holder 17. An engaging portion (not shown) is provided on the inner peripheral surface of the adjuster 16. The engaging portion engages with the groove cam 17A of the liquid crystal holder 17 and moves along the groove cam 17A. The adjuster 16 is positioned in the vertical and horizontal directions within the housing 2. Therefore, when the adjuster 16 is rotated, the liquid crystal holder 17 is moved in the left-right direction by the action of the groove cam 17A. As a result, the distance between the liquid crystal device 12 and the eyepiece optical system 120 changes, so that the focus adjustment of an image that can be visually recognized by the HM 8 can be performed.

The glasses 91 will be described. As shown in FIG. 1, the glasses 91 include a left frame portion 92, a right frame portion 93, a central frame portion 94, and a support portion 96. The left frame portion 92 is a portion that is hung on the user's left ear. The right frame portion 93 is a portion that is hung on the user's right ear. The center frame portion 94 connects the front end portion of the left frame portion 92 and the front end portion of the right frame portion 93. Although only one of them is shown in FIG. 1, the center frame portion 94 includes a pair of nose pads 95 at the longitudinal center portion. The support portion 96 is provided on the upper left end side of the central frame portion 94 as viewed from the user side, that is, on the upper right end in FIG. The support part 96 includes a downward extension part 98. The downward extending portion 98 extends in the up and down direction at the left front of the user's face. On the front surface of the downwardly extending portion 98, a plurality of tooth portions (not shown) having saw-shaped irregularities extending in the left-right direction are provided in the longitudinal direction.

As shown in FIGS. 1 and 2, a mounting portion 49 is provided in a portion of the housing 2 that faces the glasses 91. As shown in FIG. 2, the attachment portion 49 includes a U-shaped groove 49 </ b> A along the vertical direction on the inner side. A leaf spring 49B is provided at the bottom of the U-shaped groove 49A. A downwardly extending portion 98 provided in the support portion 96 of the glasses 91 shown in FIG. 1 is inserted into the U-shaped groove 49A. The leaf spring 49B is locked to any convex portion of the tooth portion provided in the downward extending portion 98. Therefore, the projection device 100 can be positioned within a predetermined range in the vertical direction of the user's head.

The configuration of the control device 200 will be described. As shown in FIG. 1, the control device 200 is a substantially rectangular parallelepiped system box, for example. As shown in FIG. 4, the control device 200 includes, for example, a power switch 62, a brightness dial 63, an operation unit 64, and the like. The power switch 62 turns on or off the power of the HMD 1. The brightness dial 63 can adjust the brightness of the backlight 41 in, for example, eight levels from level 1 to level 8. Note that the number of steps of the luminance level is not limited to this. The brightness of the backlight 41 increases as it goes from level 1 to level 8, for example. The brightness dial 63 may be a button type or may be in other forms. The operation unit 64 can perform various operations such as image selection and various mode switching in the projection apparatus 100, for example.

The electrical configuration of the control device 200 will be described with reference to FIG. The control device 200 includes, for example, a CPU 51, a ROM 52, a RAM 53, an HDMI (registered trademark) transmitter 54, a power supply IC 55, an output unit 56, and the like. The ROM 52, RAM 53, HDMI transmitter 54, output unit 56, power switch 62, luminance dial 63, operation unit 64, and the like are connected to the CPU 51. The CPU 51 performs overall control of the control device 200. The ROM 52 stores various programs. The RAM 53 temporarily stores various data. The HDMI transmitter 54 is connected to the output unit 56. For example, the HDMI transmitter 54 converts image data input from the CPU 51 into a digital serial signal, and transmits the digital serial signal to the projection device 100 via the output unit 56 and the harness 150.

The CPU 51 generates a luminance level signal in accordance with the scale adjustment of the luminance dial 63. The CPU 51 transmits the generated brightness level signal to the projection device 100 via the output unit 56 and the harness 150. The power supply IC 55 is connected to the output unit 56. The power supply IC 55 converts an unstable voltage supplied from the battery AC adapter 61 into a stable voltage. Electric power is supplied to the projection apparatus 100 through the output unit 56 and the harness 150 in addition to various electronic components of the control apparatus 200 at a stable voltage.

The electrical configuration of the projection apparatus 100 will be described with reference to FIG. The projection device 100 includes a controller 11 and a liquid crystal device 12. The controller 11 includes, for example, a CPU 31, a ROM 32, a RAM 33, an HDMI receiver 34, a luminance control unit 35, an input unit 37, a display control unit 36, a power supply IC 38, an illuminance sensor 39, and the like. The liquid crystal device 12 includes a backlight 41 and an LCD 42.

ROM 32, RAM 33, HDMI receiver 34, luminance control unit 35, display control unit 36, input unit 37, illuminance sensor 39, and the like are connected to CPU 31. A power supply IC 38, an HDMI receiver 34, and the like are connected to the input unit 37. An output line from the HDMI transmitter 54 is input to the HDMI receiver 34 without going through the CPU 31. The CPU 31 controls the projection apparatus 100 as a whole. In addition to various programs, the ROM 32 stores a brightness determination table 321 shown in FIG. The RAM 33 temporarily stores various data.

The HDMI receiver 34 receives the image data by restoring the serial signal transmitted from the control device 200. A display control unit 36 is connected to the HDMI receiver 34. The HDMI receiver 34 outputs the restored image data to the display control unit 36. The display control unit 36 drives and controls the LCD 42 based on the image data. The brightness control unit 35 sets the brightness of the backlight 41 in, for example, 64 levels based on the brightness setting signal output from the CPU 31. The 64 steps are equally spaced. By setting the voltage constant and making the current variable for each predetermined value, it is possible to set the brightness in 64 steps. The power supply IC 38 supplies power supplied from the power supply IC 55 of the control device 200 via the harness 150 to various electronic components of the projection device 100.

The gamma characteristic of the human eye will be described. The relationship between the brightness perceived by a human being as an input value and the incident illuminance with respect to the eye as an output value is not a relationship expressed by a linear function, but can be expressed by, for example, the following expression (1). Incident illuminance is light energy incident on the eye per unit area.
・ (Brightness perceived by human beings) = (incident illuminance) ^a (1)
At this time, a = 0.33 to 0.45.
Here, luminance is light energy irradiated from a unit area to a unit solid angle. Therefore, the incident illuminance can be regarded as corresponding to the luminance. As can be seen from the equation (1), the human eye perceives a change in luminance more sensitively as it becomes darker, and becomes duller in luminance change as it becomes brighter.

For example, when the luminance of the backlight 41 is set in 64 levels, the user perceives whether the luminance on the dark side is changed by one level or the luminance on the bright side is changed by one level as described above. The amount of change in brightness is different. However, when the luminance of the backlight 41 changes by one step, it is desirable for the user to always change the brightness by a certain amount. Therefore, in order to allow a human to perceive a change in brightness linearly with respect to a change in luminance, the following equation (2) is defined.
・ (Signal intensity) γ ≒ Brightness = Incident illuminance = (Brightness perceived by humans) ^{1 / a} (2)
In the present embodiment, the signal intensity corresponds to a numerical value from luminance levels 1 to 8, for example. Here, when a = 0.45, 1 / a = 1 / 0.45 = 2.2. Therefore, if γ = 2.2 is set, a human can perceive a change in brightness linearly with respect to a change in luminance of the light source.

The brightness determination table 321 will be described with reference to FIG. As described above, the luminance level of the backlight 41 can be adjusted in eight steps of levels 1 to 8 by the luminance dial 63. On the other hand, the luminance of the backlight 41 is set by the luminance control unit 35. The CPU 31 of the projection apparatus 100 refers to the luminance determination table 321 shown in FIG. 5 and determines the luminance of the backlight 41 corresponding to the luminance level adjusted by the luminance dial 63 according to the external illuminance detected by the illuminance sensor 39. decide. The luminance determination table 321 is stored in the ROM 32, for example.

The brightness determination table 321 stores the brightness of the backlight 41 corresponding to each of the brightness levels 1 to 8 according to the range of the ambient illuminance detected by the illuminance sensor 39. For example, it is conceivable that the luminance determination table 321 stores the luminance of the backlight 41 corresponding to each of the luminance levels 1 to 8 for every value of the external illuminance detected by the illuminance sensor 39. In that case, the amount of luminance data stored in the luminance determination table 321 becomes enormous. Therefore, in the present embodiment, the ambient illuminance assumed to be detected by the illuminance sensor 39 is divided into, for example, three ranges, and the luminance of the backlight 41 corresponding to each of the luminance levels 1 to 8 is set for each range. The determination table 321 is stored. Therefore, the amount of luminance data stored in the luminance determination table 321 can be small. The range of external illuminance assumed to be detected by the illuminance sensor 39 is referred to as an external illuminance range.

The ambient illuminance range is, for example, a first range, a second range, and a third range. The first range is, for example, 600 (lx) or less. The second range is, for example, 500 to 1000 (lx). The third range is, for example, 900 (lx) or more. The second range is an intermediate range between the three external illuminance ranges. When the main usage environment of the HMD 1 is, for example, a general office, the second range is preferably an illuminance range (500 to 1000 (lx)) under a general office environment. As shown in FIG. 5, reference values are stored in each external illuminance range. In the present embodiment, all external illuminances belonging to each range are regarded as reference values for the range. For example, the reference value of the first range is 500 (lx). The reference value for the second range is 750 (lx). The reference value for the third range is 1000 (lx). These reference values can be used when calculating the luminance for each illuminance range, as will be described later.

A method of calculating each luminance stored in the first to third ranges will be described. In the present embodiment, each luminance set in the other first and third ranges is calculated on the basis of each luminance stored in the second range. Specifically, the luminance corresponding to each luminance level in the first range is calculated by multiplying each luminance stored in the second range by a first coefficient described later. The brightness corresponding to each brightness level in the third range is calculated by multiplying each brightness stored in the second range by a second coefficient described later. The first coefficient is a ratio of the reference value of the first range to the reference value of the second range. Therefore, the first coefficient is 2/3. The second coefficient is a ratio of the reference value of the third range to the reference value of the second range. Therefore, the second coefficient is 4/3. Specific luminances will be described below.

The luminance stored in the second range will be described. The luminance stored in each luminance level in the second range corresponds to the curve of γ = 2.2 in the above equation (2), for example. Therefore, for example, the luminance corresponding to the luminance level 1 is 125 (cd). The luminance corresponding to the luminance level 2 is 140 (cd). The luminance corresponding to the luminance level 3 is 170 (cd). The luminance corresponding to the luminance level 4 is 250 (cd). The luminance corresponding to the luminance level 5 is 360 (cd). The luminance corresponding to the luminance level 6 is 500 (cd). The luminance corresponding to the luminance level 7 is 680 (cd). The luminance corresponding to the luminance level 8 is 920 (cd).

The luminance stored in the first range will be described. As described above, each value obtained by multiplying each brightness previously stored in the second range by 2/3 is stored as the brightness corresponding to each brightness level in the first range. As a result, for example, the luminance corresponding to luminance level 1 is 83 (cd). The luminance corresponding to the luminance level 2 is 93 (cd). The luminance corresponding to the luminance level 3 is 113 (cd). The luminance corresponding to the luminance level 4 is 167 (cd). The luminance corresponding to the luminance level 5 is 240 (cd). The luminance corresponding to the luminance level 6 is 333 (cd). The luminance corresponding to the luminance level 7 is 453 (cd). The luminance corresponding to the luminance level 8 is 613 (cd).

The luminance stored in the third range will be described. As described above, each value obtained by multiplying each brightness stored in the second range by 4/3 is stored as a brightness corresponding to each brightness level in the third range. As a result, for example, the luminance corresponding to the luminance level 1 is 167 (cd). The luminance corresponding to the luminance level 2 is 187 (cd). The luminance corresponding to the luminance level 3 is 227 (cd). The luminance corresponding to the luminance level 4 is 333 (cd). The luminance corresponding to the luminance level 5 is 480 (cd). The luminance corresponding to the luminance level 6 is 667 (cd). The luminance corresponding to the luminance level 7 is 907 (cd). The luminance corresponding to the luminance level 8 is 1227 (cd).

FIG. 6 shows three luminance curves respectively corresponding to the first range, the second range, and the third range. The luminance curve is created based on the luminance determination table 321, and the luminance stored in each luminance level is plotted for each external illuminance range. The luminance curve corresponding to the second range corresponds to the curve of γ = 2.2, and has a symmetrical shape with the graph curve of the formula (1). That is, the lower the luminance level, the smaller the change in incident illuminance with respect to the change in luminance level. On the other hand, the higher the brightness level, the greater the change in incident illuminance with respect to the change in brightness level. Therefore, for example, a human can linearly perceive a change in brightness with respect to a change in brightness caused by sequentially changing the brightness level from 1 to 8, for example.

On the other hand, the luminance curve corresponding to the first range is shifted downward with respect to the luminance curve corresponding to the second range and has a gentle slope on the higher luminance level side. In addition, the luminance curve corresponding to the third range is shifted upward with respect to the luminance curve corresponding to the second range, and has a steep slope on the higher luminance level side. This is a result of multiplying each luminance stored in each luminance level in the second range by the first coefficient and the second coefficient, respectively. Therefore, the luminance curves corresponding to the first and third ranges also correspond to the curve of γ = 2.2.

The first coefficient is, for example, a rate of change from 750 (lx) belonging to the second range to 500 lx belonging to the first range. The second coefficient is, for example, a rate of change from 750 (lx) belonging to the second range to 1000 lx belonging to the third range. In the present embodiment, by multiplying each luminance of the second range by the first coefficient and the second coefficient, the backlight 41 according to the illuminance change from the second range in the first and third ranges. The brightness of the can be changed satisfactorily.

The relationship between the see-through degree in the HM8 and the luminance of the backlight 41 with respect to the ambient illuminance will be described. The ratio of the luminance of the backlight 41 to the ambient illuminance determines the see-through degree in the HM8. The see-through degree means, for example, the transparency of a real image with respect to an image in the HM 8 viewed from the user. In order to keep such see-through degree constant even when the luminance of the backlight 41 is changed in accordance with a change in external illumination, the luminance determination table 321 is used in the present embodiment. As shown in FIGS. 5 and 6, in the luminance determination table 321, for example, in the third range where the external illuminance is bright, the luminance interval between the luminance levels is wider than in the first range where the external illuminance is dark. On the contrary, in the first range, the luminance interval between the luminance levels is narrower than that in the third range. Even in the illuminance ranges different from each other, the ratio of the luminance of the backlight 41 to the external illuminance is substantially constant at the same luminance level.

For example, at the luminance level 1, the reference value of the external illuminance in the second range is 750 (lx), and the luminance of the backlight 41 is 125 (cd). When these are simply compared at a ratio of only numerical values, the ratio of the luminance of the backlight 41 to the ambient illuminance is 1/6. At the same luminance level 1, the reference value of the external illuminance in the third range is 1000 (lx), and the luminance of the backlight 41 is 125 (cd). When these are similarly compared at a ratio of only numerical values, the ratio of the luminance of the backlight 41 to the ambient illuminance is 1/6. Furthermore, at the same luminance level 1, the reference value of the external illuminance in the first range is 1000 (lx), and the luminance of the backlight 41 is 125 (cd). When these are similarly compared at a ratio of only numerical values, the ratio of the luminance of the backlight 41 to the ambient illuminance is 1/6.

That is, in the first range, the second range, and the third range, the ratio of the luminance of the backlight 41 to the ambient illuminance is the same. This is the same result at any luminance level. In the above calculation example, the external illuminance and the luminance are shown as ratios only for the sake of simplicity, but even when converted to the same unit system, the ratio at each luminance level is constant in each illuminance range. Accordingly, even when the ambient illuminance changes, the luminance of the backlight 41 is automatically adjusted while maintaining the see-through degree in the HM 8.

The CPU 31 refers to the brightness determination table 321 as described above, and determines the brightness of the backlight 41 according to the ambient illuminance. For example, when the brightness level is adjusted to 4 by the brightness dial 63 and the external illuminance is 800 (lx), the CPU 31 sets 250 (cd) corresponding to the brightness level 4 in the second range to the brightness of the backlight 41. Determine as. For example, when the brightness level is adjusted to 4 by the brightness dial 63 and the external illumination is 200 (lx), the CPU 31 sets 167 (cd) corresponding to the brightness level 4 in the first range to the brightness of the backlight 41. Determine as.

Explains the threshold hysteresis of the ambient illumination range. In the luminance determination table 321, each threshold value in the first to third ranges is set to hysteresis. For example, if the threshold value between the first range and the second range is set to a single value of 500 (lx), the luminance of the backlight 41 is switched many times when the ambient illuminance is around 500 (lx). It becomes difficult to see. Therefore, in the present embodiment, for example, the upper limit value of the first range is 600 (lx) and the lower limit value of the second range is 500 (lx), thereby setting the threshold value as hysteresis. Therefore, for example, even if the ambient illuminance decreases from the second range to the first range and then stagnates in the vicinity of 500 (lx), it does not become the second range unless it becomes 600 (lx) or more. The luminance of 41 is not switched. Therefore, the luminance of the backlight 41 does not switch over and over in the vicinity of the threshold value between the first range and the second range, so that the visibility in the HM 8 can be maintained well. Similarly, the threshold value between the upper limit value of the second range and the lower limit value of the third range is set to hysteresis. Therefore, even in the vicinity of the threshold value between the second range and the third range, the luminance of the backlight 41 does not switch over and over, so that the visibility in the HM 8 can be maintained well.

The brightness control processing by the CPU 31 will be described with reference to the flowchart of FIG. When the power switch 62 of the control device 200 is turned on, the CPU 31 calls the brightness control program stored in the ROM 32 and executes this process. First, the CPU 31 detects the ambient illuminance by the illuminance sensor 39 (S11). The detected ambient illuminance data is temporarily stored in the RAM 33. Next, the CPU 31 detects the state of the luminance dial 63 and specifies the luminance level (S12). For example, the CPU 31 transmits a request signal for requesting the control device 200 to transmit a luminance level signal. The CPU 51 of the control device 200 transmits a brightness level signal corresponding to the adjustment of the brightness dial 63 to the projection device 100. The luminance level signal includes information on luminance levels 1 to 8, for example. The CPU 31 can identify the current luminance level by receiving the luminance level signal. Information on the specified luminance level is temporarily stored in the RAM 33.

Next, the CPU 31 executes a luminance determination process (S13). The luminance determination process is a process of determining the luminance of the backlight 41 corresponding to the current luminance level based on the detected external illuminance based on the luminance determination table 321. For example, it is assumed that the detected external illuminance is 800 (lx) and the luminance dial 63 is adjusted to the luminance level 4. The ambient illuminance belongs to the second range. Referring to the luminance determination table 321 in FIG. 5, the luminance corresponding to the luminance level 4 in the second range is 250 (cd). Therefore, the luminance is determined to be 250 (cd). The CPU 31 outputs a luminance setting signal corresponding to the determined luminance to the luminance control unit 35 shown in FIG. 4 (S14). The luminance control unit 35 drives and controls the backlight 41 based on the luminance setting signal. The backlight 41 emits light at 250 (cd) which is the determined luminance.

And CPU31 detects external field illumination intensity again by the illumination intensity sensor 39 (S15). The CPU 31 compares the detected external illuminance with the external illuminance previously stored in the RAM 33, and determines whether or not the external illuminance has changed (S16). For example, the CPU 31 may refer to the luminance determination table 321 and determine that the external illuminance has changed when the range to which the external illuminance belongs is different. For example, when the luminance dial 63 is in the luminance level 4 and the external illuminance decreases from 800 (lx) to 200 (lx), referring to the luminance determination table 321, the external illuminance changes from the second range to the first range. is doing. In this case, the CPU 31 determines that the ambient illuminance has changed (S16: YES), returns to S13, and executes the luminance determination process again.

In the luminance determination process, since the ambient illuminance is in the first range, referring to the luminance determination table 321, the luminance corresponding to the luminance level 4 in the first range is 167 (cd). Accordingly, the luminance is determined to be 167 (cd). The CPU 31 outputs a luminance setting signal corresponding to the determined luminance to the luminance control unit 35 shown in FIG. 4 (S14). The luminance control unit 35 drives and controls the backlight 41 based on the luminance setting signal. Accordingly, the luminance of the backlight 41 is changed from 250 (cd) to 167 (cd).

Thus, when the ambient illuminance changes, for example, from the second range to the first range, the luminance of the backlight 41 corresponds to the first range while the luminance level 4 adjusted by the luminance dial 63 is maintained. The brightness is switched to As described above, the ratio of the luminance of the backlight 41 to the external illuminance in the HM 8 is kept substantially constant. Therefore, when the ambient illuminance changes, the luminance of the backlight 41 is switched while the see-through degree in the HM 8 is maintained. For example, the user adjusts the see-through degree in the HM 8 by adjusting the brightness dial 63 according to the work scene. In other words, there is a see-through degree suitable for the work surface. In the present embodiment, when the ambient illuminance changes, the luminance of the backlight 41 is adjusted in a state in which the see-through degree in the HM 8 is maintained, so that the image visibility in the HM 8 can be favorably maintained.

By the way, when the external illuminance does not change (S16: NO), the CPU 31 detects the state of the luminance dial 63 again and specifies the luminance level (S17). Information on the specified luminance level is temporarily stored in the RAM 33. The CPU 31 compares the specified luminance level with the luminance level previously stored in the RAM 33, and determines whether the luminance level has changed (S18). For example, when the brightness level is changed from 4 to 7 by the brightness dial 63 in an environment where the ambient illuminance is 800 (lx) (S18: YES), the process returns to S13 and the brightness determination process is executed again.

In the luminance determination process, since the ambient illuminance is in the second range, referring to the luminance determination table 321, the luminance corresponding to the luminance level 7 in the second range is 680 (cd). Accordingly, the luminance is determined to be 680 (cd). The CPU 31 outputs a luminance setting signal corresponding to the determined luminance to the luminance control unit 35 shown in FIG. 4 (S14). The luminance control unit 35 drives and controls the backlight 41 based on the luminance setting signal. Therefore, the luminance of the backlight 41 is changed from 250 (cd) so far to 680 (cd). As a result, the see-through degree in the HM 8 changes.

If the luminance level has not changed (S18: NO), the CPU 31 determines whether the power is turned off (S19). Until the power is turned off (S19: NO), the CPU 31 returns to S15 and repeats the above processing. If the CPU 31 determines that the power has been turned off (S19: YES), the process is terminated.

In the above description, the liquid crystal device 12 illustrated in FIG. 3 is an example of the liquid crystal unit of the present disclosure. HM8 is an example of the deflecting unit of the present disclosure. The illuminance sensor 39 shown in FIG. 1 is an example of the illuminance detection means of the present disclosure. The luminance dial 63 is an example of the accepting unit of the present invention. The CPU 31 that executes the processes of S13 and S15 to S18 in FIG. 7 is an example of the determining unit of the present disclosure. CPU31 which performs the process of S14 is an example of the change means of this indication.

The present disclosure is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, the luminance corresponding to each luminance level is stored such that the luminance curve of the second range of the ambient illuminance stored in the luminance determination table 321 corresponds to the curve of γ = 2.2. Based on the luminance data stored in the second range, the luminances of the other first and third ranges are calculated and stored. For example, the luminance may be stored for each luminance level in the first to third ranges so that the luminance of the backlight 41 changes linearly with changes in the luminance level.

For example, the brightness determination table 322 shown in FIG. 8 linearly changes the brightness of the backlight 41 with respect to the change of the brightness level in the first to third ranges. For example, when the luminance stored in each of the luminance levels 1 to 8 in the second range is plotted, a graph showing a linear change is obtained as shown in FIG. Each luminance stored in the first range is calculated by multiplying each luminance stored in the second range by the same coefficient multiple as in the above embodiment, for example, 2/3. Each luminance stored in the third range is calculated by multiplying each luminance stored in the second range by the same coefficient multiple as in the above embodiment, for example, 4/3. Accordingly, similarly to the second range, when the luminances stored in the luminance levels 1 to 8 in the first and third ranges are plotted, respectively, a graph showing a linear change as shown in FIG. Become.

Also in the brightness determination table 322 of this modification, the brightness interval between brightness levels is wider in the range where the external illuminance is brighter than in the range where the external illuminance is darker. Conversely, in the range where the external illuminance is dark, the luminance interval between the luminance levels is narrower than in the range where the external illuminance is bright. Even in different illuminance ranges, the luminance corresponding to each luminance level is stored in each illuminance range so that the ratio of the luminance of the backlight 41 to the external illuminance is constant at the same luminance level. Thereby, for example, even when the ambient illuminance changes, the brightness of the backlight 41 is automatically adjusted while the see-through degree in the HM 8 is maintained. Therefore, when the external illuminance changes, the luminance of the backlight 41 is automatically adjusted according to the external illuminance without causing the user to feel uncomfortable.

In the above embodiment, the threshold value of each illuminance range is set to hysteresis in the luminance determination table 321 shown in FIG. 5. For example, the threshold value between the first range and the second range is 500 (lx), for example, Even when the threshold values for the third range are each a single threshold value such as 1000 (lx), for example, it may be determined that the ambient illuminance has changed if a state exceeding these threshold values continues for a predetermined time. Therefore, a modification of the brightness control process will be described with reference to the flowchart of FIG.

As shown in FIG. 10, in the brightness control process as a modification, S16 of the process of FIG. 7 is deleted, and the processes of S31 to S32 are added between S15 and S17. For example, the CPU 31 detects the ambient illuminance while driving the backlight 41 with the brightness determined in the brightness determination process of S13 (S15). The CPU 31 determines whether or not the detected external illuminance has changed from the previous external illuminance stored in the RAM 33 and has exceeded any threshold value in each illuminance range (S31). If the detected external illuminance does not exceed the threshold (S31: NO), the process proceeds to S17 assuming that the external illuminance has not changed.

On the other hand, for example, when the detected external illuminance exceeds the threshold (S31: YES), the CPU 31 continues to detect the external illuminance by the illuminance sensor 39, for example, and the state exceeding the threshold continues for a predetermined time such as several seconds. Whether or not (S32). For example, if the external illuminance returns before the threshold value exceeds the threshold before the predetermined time has elapsed (S32: NO), the process proceeds to S17 assuming that the external illuminance has not changed.

On the other hand, when the CPU 31 determines that the state exceeding the threshold value has continued for a predetermined time (S32: YES), it returns to S13 assuming that the external illuminance has changed, and executes the luminance determination process for the external illuminance after the change. . Thereby, even if the external illuminance detected by the illuminance sensor 39 is in the vicinity of the threshold value of the external illuminance range, the luminance of the backlight 41 does not switch over and over, so that the visibility in the HM 8 can be maintained well.

In the present modification, the CPU 31 that executes S31 of FIG. 10 is an example of the threshold passage determination unit of the present disclosure. The CPU 31 that executes S32 is an example of a state determination unit of the present disclosure. S32: CPU31 which performs YES, S13, and S14 is an example of the brightness | luminance change means of this indication.

The present disclosure can be variously modified in addition to the above modified examples. For example, in the above embodiment, the type of HMD 1 in which the HM 8 is arranged in front of the user's left eye has been described. However, the present disclosure can be applied to a type of HMD in which the HM is arranged in front of the right eye.

In the above embodiment, the HMD 1 has been described as being attached to the glasses 91. However, for example, the HMD 1 can be attached to a mounting member attached to a head such as a headband, a headphone, or a helmet.
So far

In the above embodiment, the illuminance sensor 39 is exposed to the front from the small hole portion 40 provided on the front surface of the housing 2, but if the illuminance of the outside world in a direction that the user can see through the HM 8 can be detected, the illuminance sensor The position 39 may be other than this. For example, the position of the illuminance sensor 39 may be provided above the central frame portion 94 of the glasses 91. Since the light from the real image transmitted through the HM 8 is in the direction of the HM 8 when viewed from the user, the see-through degree in the HM 8 is accurately adjusted by the illuminance sensor 39 detecting the illuminance of the external environment in that direction.

In the above embodiment, the illuminance sensor 39 has been described as an example of the illuminance detection unit of the present disclosure. However, for example, an imaging unit such as a camera may be mounted on the HMD, and the ambient illuminance may be detected from an image captured by the camera. . In this case, the camera may point the imaging direction in front of the user's visual field.

In the above embodiment, the luminance determination table 321 or 322 divides the ambient illuminance into three ranges and reduces the amount of luminance data. For example, for every value of the external illuminance detected by the illuminance sensor 39, In addition, the luminance of the backlight 41 corresponding to each of the luminance levels 1 to 8 may be stored. In this case, the luminance of the backlight 41 corresponding to each luminance level is determined according to the ambient illuminance detected by the illuminance sensor 39.

1 Head mounted display (HMD)
8 Half mirror (HM)
12 Liquid crystal device 31 CPU
32 ROM
41 Backlight 42 LCD
63 Luminance dials 321 and 322 Luminance determination table

Claims (7)

A light valve element capable of forming an image with pixels arranged in a matrix, and
A light source provided in the light valve element;
A deflecting unit that reflects at least a part of the image light emitted from the light valve element and enters the user's eye, and transmits at least a part of the light from the external real image to enter the user's eye;
Illuminance detection means for detecting the illuminance of the outside world,
Accepting means for accepting an input for designating a stepwise luminance level of the light source from the outside;
With respect to the plurality of luminance levels that can be received by the reception unit, the reception unit determines from the plurality of luminance levels in which the luminance of the light source is set according to the illuminance detected by the illuminance detection unit. Determining means for determining a luminance corresponding to the one luminance level received;
Changing means for changing the luminance of the light source to the luminance determined by the determining means,
The determination unit has a wider luminance interval between the plurality of luminance levels as the illuminance detected by the illuminance detection unit is brighter, and a luminance interval between the plurality of luminance levels as the illuminance is darker. A head mounted display characterized in that the brightness of the light source is determined from the plurality of brightness levels that are narrow and have a constant ratio of the brightness of the light source to the ambient illuminance at the same brightness level. The determining unit is different from the predetermined illuminance by multiplying the luminance set for each of the plurality of luminance levels at a predetermined illuminance by a coefficient corresponding to the illuminance detected by the illuminance detecting unit. The head mounted display according to claim 1, wherein the brightness corresponding to the plurality of brightness levels corresponding to illuminance is determined from the set brightness levels. 2. The head mounted display according to claim 1, wherein the illuminance detecting means detects the illuminance of the external environment in the front direction when the illuminance detecting means is mounted on a user's head. The determining means is provided with a plurality of illuminance ranges for the illuminance detected by the illuminance detecting means, and for each of the illuminance ranges, the brightness levels corresponding to the plurality of brightness levels are respectively set, Determining a luminance corresponding to one of the luminance levels received by the receiving means;
The head-mounted display according to claim 1, wherein the threshold value of the illuminance range has hysteresis. The determining means is provided with a plurality of illuminance ranges for the illuminance detected by the illuminance detecting means, and for each of the illuminance ranges, the brightness levels corresponding to the plurality of brightness levels are respectively set, Determining a luminance corresponding to one of the luminance levels received by the receiving means;
Threshold passage determination means for determining whether or not the illuminance detected by the illuminance detection means exceeds the threshold;
State determining means for determining whether or not the state in which the illuminance exceeds the threshold continues for a predetermined time when the illuminance is determined to have exceeded the threshold by the threshold passage determining means;
A luminance changing means for changing to the luminance determined in the illuminance range on the side exceeding the threshold when the state determining means determines that the state exceeding the threshold has continued for the predetermined time. The head-mounted display according to claim 1. A light valve element; a light source provided in the light valve element; and at least part of image light irradiated from the light valve element is reflected and incident on a user's eye, and at least light from a real image in the outside world is reflected. Luminance of a head-mounted display comprising a deflection unit that partially transmits and enters the user's eyes, illuminance detection means that detects the illuminance of the outside, and reception means that accepts a stepwise luminance level of the light source from the outside An adjustment method,
With respect to the plurality of luminance levels that can be received by the reception unit, the reception unit determines from the plurality of luminance levels in which the luminance of the light source is set according to the illuminance detected by the illuminance detection unit. When determining the luminance corresponding to the received one luminance level, the brighter the illuminance detected by the illuminance detecting means, the wider the luminance interval between the plurality of luminance levels and the darker the illuminance side. The determination step of determining the luminance of the light source from the plurality of luminance levels, wherein the interval is narrow and the ratio of the luminance of the light source to the external illumination is constant at the same luminance level;
A luminance adjustment method comprising: changing the luminance of the light source to the luminance determined in the determining step. A light valve element; a light source provided in the light valve element; and at least part of image light irradiated from the light valve element is reflected and incident on a user's eye, and at least light from a real image in the outside world is reflected. A head-mounted display having a deflection unit that transmits part of the light and enters the user's eyes, illuminance detection means that detects the illuminance of the outside, and reception means that accepts a stepwise luminance level of the light source from outside A control program for causing
On the computer,
With respect to the plurality of luminance levels that can be received by the reception unit, the reception unit determines from the plurality of luminance levels in which the luminance of the light source is set according to the illuminance detected by the illuminance detection unit. When determining the luminance corresponding to the received one luminance level, the brighter the illuminance detected by the illuminance detecting means, the wider the luminance interval between the plurality of luminance levels and the darker the illuminance side. The determination step of determining the brightness of the light source from the plurality of brightness levels in which the interval is narrow and the ratio of the brightness of the light source to the external illuminance is constant at the same brightness level;
A control program for executing a brightness change step for changing the brightness of the light source to the brightness determined in the determination step.

Images