JP2013174708A - Head-mounted display, brightness adjusting method, and control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a head-mounted display, a brightness adjusting method, and a control program, capable of adjusting a brightness of a backlight while keeping a see-through degree at a display part when an external illuminance is changed.SOLUTION: A head-mounted display, while referring to a brightness decision table 321, decides, in accordance with an external illuminance detected by an illuminance sensor, a brightness of a backlight of a liquid crystal device corresponding to a brightness level adjusted by means of a brightness dial. In the brightness decision table 321, in a third range in which the external illuminance is bright, a brightness interval between brightness levels is wider than that in a first range in which the external illuminance is dark. Also, even in mutually different illuminance ranges, a rate of the brightness of the backlight relative to the external illuminance is constant at the same brightness level. Accordingly, even when the external illuminance changes, the brightness of the backlight can be adjusted while keeping a see-through degree at a half mirror which reflects image light.

Description

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

  2. Description of the Related Art Conventionally, a head mounted display (hereinafter referred to as “HMD”) that displays an image so as to be visually recognized as an image in front of a user's eye is known. 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 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, an HMD that can change the brightness of an image in an image display unit in accordance with the external illumination is disclosed (see, for example, Patent Document 1).

  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, and 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 an image according to a change in external illuminance changes the luminance level every 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 invention is to solve the above-described problems, 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 invention 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 display unit that reflects at least a part of the image light to enter the user's eyes and transmits at least a part of the light from the real image of the outside world so that the image is superimposed on the real image in the user's field of view. Illuminance detecting means for detecting the illuminance of the outside world, receiving means for accepting an input for designating a stepwise luminance level of the light source from the outside, and for each luminance level received by the receiving means, by the illuminance detecting means For each illuminance to be detected, a determining unit that determines the luminance of the light source, and the luminance of the light source are received by the receiving unit that is determined by the determining unit. Change means for changing to the luminance corresponding to the received luminance level, the determination means, the brighter the illuminance detected by the illuminance detection means, the wider the luminance interval between the luminance levels, The lower the illuminance is, the narrower the luminance interval between the luminance levels is, and the luminance ratio of the light source to the external illuminance is always constant at the same luminance level. The brightness of the light source is determined respectively.

  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 luminance levels of the light source. Conversely, the darker the illuminance in the outside world, the narrower the brightness interval between the 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 held, so that the see-through degree in the display unit can be held.

  In the first aspect, the determining unit multiplies each luminance level by a coefficient corresponding to the illuminance detected by the illuminance detecting unit to the luminance determined for each luminance level at a predetermined illuminance. The corresponding luminance should be determined respectively. 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 display unit can be kept constant.

  Moreover, the 1st aspect WHEREIN: The said illumination intensity detection means is good to detect the illumination intensity of the external field of the direction which a user can permeate | transmit and visually recognize the said display part. 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.

  In the first aspect, the determining unit provides a plurality of illuminance ranges for the illuminance detected by the illuminance detecting unit, determines the luminance corresponding to each luminance level for each illuminance range, and the illuminance range. The threshold value may have 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, the visibility in the display unit can be favorably maintained.

  Further, in the first aspect, the determination unit provides a plurality of illuminance ranges for the illuminance detected by the illuminance detection unit, determines a luminance corresponding to each luminance level for each of the illuminance ranges, and detects the illuminance. A threshold passage judging means for judging whether or not the illuminance detected by the means exceeds the threshold value, and the illuminance passed the threshold value when the threshold passage judging means judges that the illuminance exceeds the threshold value. A state determining means for determining whether or not the state has continued for a predetermined time; and when the state determining means determines that the state that has passed the threshold has continued for the predetermined time, the illuminance range on the side exceeding the threshold is It is good to provide the brightness | luminance change means which changes to the determined brightness | luminance. 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, the visibility in the display unit can be favorably maintained.

The brightness adjustment method according to the second aspect of the present invention 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 display unit for visually recognizing an image superimposed on a real image in a user's field of view, illuminance detection means for detecting illuminance in the external environment, and reception means for receiving a stepwise luminance level of the light source from the outside. A brightness adjustment method for a head-mounted display provided, wherein the illuminance is determined when the brightness of the light source is determined for each illuminance detected by the illuminance detection means for each brightness level received by the reception means. The brighter the illuminance detected by the detection means, the wider the luminance interval determined for each luminance level, and the darker the illuminance side, the narrower the interval. In addition, the determination step of determining the luminance of the light source for each luminance level so that the ratio of the luminance of the light source to the ambient illuminance is always constant at the same luminance level, and the luminance of the light source, A luminance changing step of changing to a luminance corresponding to the luminance level received by the receiving means determined in the determining step.

  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 if the external illuminance changes. The see-through degree can be maintained.

  A control program according to a third aspect of the present invention reflects 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 a user's eye. A display unit that allows an image to be visually recognized by being superimposed on a real image in the user's field of view; an illuminance detection unit that detects the illuminance of the outside; and a reception unit that receives a stepwise luminance level of the light source from the outside. A control program for causing a head-mounted display to function, when determining the luminance of the light source for each illuminance detected by the illuminance detecting means for each of the luminance levels received by the receiving means. The higher the illuminance detected by the illuminance detection means, the wider the luminance interval determined for each luminance level, and the illuminance is The brightness of the light source is determined for each of the brightness levels so that the closer the distance is, the narrower the interval is, and the ratio of the brightness of the light source to the ambient illuminance is always constant at the same brightness level. A determining step; and a luminance changing step of changing the luminance of the light source to a luminance corresponding to the luminance level received by the receiving means determined in the determining step.

  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 display 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. It is the II sectional view taken on the line in FIG. It is a block diagram which shows the electric constitution of HMD1. It is a conceptual diagram of the brightness | luminance determination table. 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 invention will be described with reference to the drawings. A head mounted display 1 (hereinafter referred to as an HMD 1) shown in FIG. 1 displays an image so as to be visually recognized as an image in front of the user's eyes. 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.

  First, 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. However, the projection apparatus 100 may be attached to the glasses used by the 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.

  Next, 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. The housing | casing 2 is a square cylindrical resin member, and is L shape in planar view (refer FIG. 2). The housing 2 includes a projection unit 10 (see FIG. 3). 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 (hereinafter referred to as HM holder 5) is fixed to the opening 7 on the left side of the housing 2. 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 referred to as HM8).

  HM8 is made of resin. The HM 8 reflects at least a part (for example, half) of the light emitted from the projection unit 10 and enters the left eyeball (not shown) of the user. 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.

  Next, 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 (hereinafter referred to as an LCD 42) shown in FIG. 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 luminous flux of image light. That is, “collection” 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.

  Next, 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 is provided between the front end portion of the left frame portion 92 and the front end portion of the right frame portion 93. The center frame portion 94 includes a pair of nose pads 95 (only one is shown in FIG. 1) at the center in the longitudinal direction. The support portion 96 is provided on the upper left end side (upper right end in FIG. 1) of the central frame portion 94 as viewed from the user side. 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. A tooth portion (not shown) having a saw-toothed unevenness is engraved in the longitudinal direction on the front surface of the downward extending portion 98.

  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. The mounting portion 49 includes a U-shaped groove 49A (see FIG. 2) along the vertical direction. A leaf spring 49B is provided at the bottom of the U-shaped groove 49A. A downward extending portion 98 provided in the support portion 96 of the glasses 91 is inserted into the U-shaped groove 49A. The leaf spring 49B is locked to any peak 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.

  Next, 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. The control device 200 includes, for example, a power switch 62, a brightness dial 63, an operation unit 64 (see FIG. 4, not shown in FIG. 1), and the like. The power switch 62 turns on / 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 luminance 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.

  Next, 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, and the like are connected to the CPU 51. The power switch 62, the brightness dial 63, and the operation unit 64 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 apparatus 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 luminance level signal to the projection apparatus 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 with a stable voltage.

  Next, 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.

  The 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 the 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 luminance determination table 321 (see FIG. 5) to be described later. 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 decoded 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 luminance control unit 35 sets the luminance of the backlight 41 in, for example, 64 levels by constant current control based on the luminance setting signal output from the CPU 31. The 64 steps are predetermined luminance intervals and equal intervals. Constant current control is control performed by changing the current while keeping the voltage constant. 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.

Next, the γ (gamma) characteristics of the human eye will be described. The relationship between the brightness (input value) perceived by humans and the incident illuminance (output value) to the eyes is not a relationship represented by a linear function, but can be represented by, for example, the following equation (1). The incident illuminance is light energy incident on the eye per unit area.
・ (Brightness perceived by humans) = (incident illuminance) ^a (1)
At this time, it is a = 0.33-0.45, and it becomes a graph curve of the convex shape (expands) upwards. 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. Therefore, the following equation (2) is defined so that a human can perceive linearly to a change in luminance.
(Signal intensity) ^γ ≒ luminance = 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 linearly with respect to the luminance change of the light source.

  Next, the luminance 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 device 100 refers to the luminance determination table 321 (see FIG. 5), and 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. To decide. The luminance determination table 321 is stored in the ROM 32, for example.

  The luminance determination table 321 sets the luminance of the backlight 41 corresponding to each of the luminance levels 1 to 8 in accordance with the brightness of the external illuminance detected by the illuminance sensor 39. For example, it is conceivable to set 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 set in the luminance determination table 321 becomes enormous. Therefore, in this 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. doing. Therefore, the amount of luminance data set in the luminance determination table 321 can be small. These ranges are 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. If the main usage environment of the HMD 1 is assumed to be a general office, for example, the second range may be set to an illuminance range (500 to 1000 lx) under a general office environment. A reference value is provided for each ambient 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 set to 500 lx. The reference value of the second range is 750 lx. The reference value of 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 for calculating each luminance set in each of the first to third ranges will be described. In the present embodiment, each brightness set in the other first and third ranges is calculated with reference to each brightness set in the second range. Specifically, the luminance corresponding to each luminance level in the first range is calculated by multiplying each luminance set 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 set in the second range by a second coefficient described later. The first coefficient is a ratio of the reference value (500 lx) of the first range to the reference value (750 lx) of the second range. Therefore, the first coefficient is 2/3. The second coefficient is a ratio of the reference value (1000 lx) of the third range to the reference value (750 lx) of the second range. Therefore, the second coefficient is 4/3. Specific luminances will be described below.

  First, the luminance set in the second range will be described. The luminance set for each luminance level in the second range is made to correspond to the curve of γ = 2.2, 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).

  Next, the luminance set in the first range will be described. As described above, each value obtained by multiplying each brightness previously set in the second range by 2/3 is set as a 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).

  Next, the luminance set in the third range will be described. As described above, each value obtained by multiplying each previously set brightness in the second range by 4/3 is set as the 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 corresponding to the first range, the second range, and the third range, respectively. The brightness curve is created based on the brightness determination table 321 and plots the brightness set for each brightness level for each external illumination range. The luminance curve corresponding to the second range corresponds to the curve of γ = 2.2. This luminance curve has a downwardly convex (swelling) shape. This is symmetric with the graph curve of the equation (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, when the luminance level is changed in order from 1 to 8, a human can perceive the luminance change linearly.

  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 set to 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.

  Here, 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 such first coefficient and second coefficient, in the first and third ranges, the backlight 41 according to the illuminance change from the second range. The luminance can be changed satisfactorily.

  Next, the relationship between the see-through degree in the HM 8 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 this embodiment, the brightness determination table 321 is used so that such a see-through degree can be kept constant even when the brightness of the backlight 41 is changed in accordance with a change in ambient illuminance. 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. Further, 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 external 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 a ratio of only numerical values for easy understanding. However, even when converted to the same unit system, the ratio at each luminance level is constant in each illuminance range. Therefore, even when the ambient illuminance changes, the luminance of the backlight 41 can be 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 luminance level is adjusted to 4 by the luminance dial 63 and the external illumination is 800 lx, the CPU 31 determines 250 (cd) corresponding to the luminance level 4 in the second range as the luminance of the backlight 41. . 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 determines 167 (cd) corresponding to the brightness level 4 in the first range as the brightness of the backlight 41. .

  Next, the hysteresis property of the threshold value in the ambient illuminance range will be described. In the luminance determination table 321, each threshold value in the first to third ranges is set to hysteresis. For example, if the threshold values of the first range and the second range are 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, which makes it very difficult to see. Therefore, in this embodiment, for example, the upper limit value of the first range is set to 600 lx, and the lower limit value of the second range is set to 500 lx, so that the threshold value is set to 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, the luminance does not change because the second range is not reached unless it exceeds 600 lx. . Therefore, the luminance of the backlight 41 does not switch over and over in the vicinity of the threshold values of the first range and the second range, so that the visibility in the HM 8 can be maintained well. The threshold value between the upper limit value of the second range and the lower limit value of the third range is similarly set to hysteresis. Therefore, even in the vicinity of the threshold values of 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 kept good.

  Next, luminance 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. The specified brightness level information 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 controller 35 (see 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, the external illuminance changes from the second range to the first range with reference to the luminance determination table 321. 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 controller 35 (see 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 external illuminance changes from, for example, the second range to the first range, the luminance of the backlight 41 corresponds to the first range while maintaining the luminance level 4 adjusted by the luminance dial 63. Switch to brightness. 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 can be switched while maintaining the see-through degree in the HM 8. 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 has not changed (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, the ambient illuminance is in the second range, and therefore the luminance corresponding to the luminance level 7 in the second range is 680 (cd) with reference to the luminance determination table 321. 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 controller 35 (see 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 shown in FIG. 3 is an example of the “liquid crystal unit” of the present invention. The HM 8 is an example of the “display unit” in the present invention. The illuminance sensor 39 shown in FIG. 1 is an example of the “illuminance detection means” in the present invention. The luminance dial 63 is an example of the “accepting means” in the present invention. The CPU 31 that executes the processes of S13 and S15 to S18 in FIG. 7 is an example of the “determination unit” in the present invention. The CPU 31 that executes the process of S14 is an example of the “changing unit” in the present invention.

  As described above, the HMD 1 of this embodiment includes the projection device 100 and the control device 200. The projection device 100 includes a controller 11 and a liquid crystal device 12. The liquid crystal device 12 includes a backlight 41. The luminance of the backlight 41 is set by the luminance control unit 35. The brightness level of the backlight 41 is adjusted by the brightness dial 63 provided in the control device 200. The brightness dial 63 can adjust the brightness level of the backlight 41 in, for example, eight levels. The CPU 31 of the controller 11 refers to the luminance determination table 321 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. The brightness determination table 321 is stored in the ROM 32.

  The brightness determination table 321 stores the brightness of the backlight 41 corresponding to the brightness levels 1 to 8 for each of the three ranges of the ambient illuminance. In this table, in the range where the external illuminance is brighter, the luminance interval between the luminance levels is wider than in the range where the external illuminance is dark. 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. And even if it is a mutually different illumination intensity range, the brightness | luminance corresponding to each brightness | luminance level is each set so that the ratio of the brightness | luminance of the backlight 41 with respect to external field illumination intensity may become fixed in the same brightness | luminance level. The ratio of the luminance of the backlight 41 to the ambient illuminance determines the see-through degree in the HM8.

  The CPU 31 refers to such a luminance determination table 321 and determines the luminance corresponding to the luminance level adjusted by the luminance dial 63 in the illuminance range to which the external illuminance detected by the illuminance sensor 39 belongs. Thereby, for example, even when the ambient illuminance changes, the luminance of the backlight 41 can be automatically adjusted while maintaining the see-through degree in the HM 8. Therefore, when the external illuminance changes, the brightness of the backlight 41 can be automatically adjusted according to the external illuminance without causing the user to feel uncomfortable.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, in the above embodiment, the brightness corresponding to each brightness level is set so that the brightness curve of the second range of the external illuminance set in the brightness determination table 321 corresponds to the curve of γ = 2.2. Based on the brightness data set in the second range, the brightness in the other first and third ranges is calculated and set. For example, the luminance may be set 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 luminance determination table 322 shown in FIG. 8 linearly changes the luminance of the backlight 41 with respect to the change in luminance level in the first to third ranges. For example, when the luminances set for the respective luminance levels 1 to 8 in the second range are plotted, a graph showing a linear change is obtained as shown in FIG. Each luminance set in the first range is calculated by multiplying each luminance set in the second range by the same coefficient multiple (for example, 2/3) as in the above embodiment. Each luminance set in the third range is calculated by multiplying each luminance set in the second range by the same coefficient multiple (for example, 4/3) as in the above embodiment. Therefore, similarly to the second range, when the luminances set to the respective luminance levels 1 to 8 in the first and third ranges are plotted, the graphs show linear changes as shown in FIG. .

  Also in the luminance determination table 322 of this modification, the luminance interval between luminance 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. And even if it is a mutually different illumination intensity range, the brightness | luminance corresponding to each brightness | luminance level is each set so that the ratio of the brightness | luminance of the backlight 41 with respect to external field illumination intensity may become fixed in the same brightness | luminance level. Thereby, for example, even when the ambient illuminance changes, the luminance of the backlight 41 can be automatically adjusted while maintaining the see-through degree in the HM 8. Therefore, when the external illuminance changes, the brightness of the backlight 41 can be 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 values of the first range and the second range are set to 500 lx, for example, and the second range and the third range are set. Even when the range threshold is set to, for example, 1000 lx and each is a single threshold value, it may be determined that the ambient illuminance has changed if the state exceeding the threshold value 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, the brightness control process as a modified example is obtained by deleting S <b> 16 of the process of FIG. 7 and adding processes S <b> 31 to S <b> 32 between S <b> 15 and S <b> 17. 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 (for example, 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 in FIG. 10 is an example of the “threshold passage judging means” in the present invention. The CPU 31 that executes S32 is an example of the “state determination means” in the present invention. S32: The CPU 31 that executes YES, S13, and S14 is an example of the “luminance changing means” in the present invention.

  Further, the present invention 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 invention can also be applied to an HMD in which the HM is arranged in front of the right eye.

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

  Moreover, in the said embodiment, although the illumination intensity sensor 39 is exposed ahead from the small hole part 40 provided in the front surface of the housing | casing 2, if a user can detect the illumination intensity of the external field of the direction which can permeate | transmit and see through HM8, The position of the sensor 39 may be other than this. For example, you may make it provide in the upper part of the center frame part 94 of the spectacles 91. FIG. 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 can be accurately adjusted by detecting the illuminance of the external environment in that direction.

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

  In the above embodiment, in the luminance determination tables 321 and 322, the ambient illuminance is divided into three ranges to reduce 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 set. In this case, the luminance of the backlight 41 corresponding to each luminance level can be 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;
At least a part of the image light emitted from the light valve element is reflected and incident on the user's eye, and at least a part of the light from the real image in the external environment is transmitted to be superimposed on the real image in the user's field of view. A display unit for visually recognizing the image,
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;
Determining means for determining the luminance of the light source for each illuminance detected by the illuminance detecting means for each luminance level received by the receiving means;
Changing means for changing the brightness of the light source to a brightness corresponding to the brightness level received by the receiving means determined by the determining means;
The determination means is such that the brighter the illuminance detected by the illuminance detection means, the wider the luminance interval between the luminance levels, and the darker the illuminance side, the narrower the luminance interval between the luminance levels. A head mounted display that determines the brightness of the light source for each of the brightness levels so that the ratio of the brightness of the light source to the ambient illuminance is always constant at the same brightness level.   The determining unit determines the luminance corresponding to each luminance level by multiplying the luminance determined for each luminance level 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:   3. The head mounted display according to claim 1, wherein the illuminance detection unit detects the illuminance of the outside world in a direction that the user can visually recognize through the display unit. The determining unit provides a plurality of illuminance ranges for the illuminance detected by the illuminance detecting unit, and determines the luminance corresponding to each luminance level for each illuminance range,
4. The head mounted display according to claim 1, wherein the threshold value of the illuminance range has a hysteresis. The determining unit provides a plurality of illuminance ranges for the illuminance detected by the illuminance detecting unit, and determines the luminance corresponding to each luminance level for each illuminance range,
Threshold passage determining means for determining whether or not the illuminance detected by the illuminance detecting means exceeds the threshold;
State determining means for determining whether or not the state where the illuminance has passed the threshold has continued for a predetermined time when the illuminance is determined to have exceeded the threshold by the threshold passage determining means;
Brightness changing means for changing to the brightness determined in the illuminance range on the side exceeding the threshold when the state determining means determines that the state that has passed the threshold has continued for the predetermined time. The head-mounted display according to claim 1, wherein the head-mounted display is a head-mounted display. A light valve element, a light source provided in the light valve element, and at least part of the image light emitted from the light valve element is reflected and incident on the user's eye, so that it is superimposed on the real image in the user's field of view. A brightness adjustment method for a head mounted display, comprising: a display unit for visually recognizing an image; illuminance detection means for detecting illuminance in the outside; and reception means for receiving a stepwise luminance level of the light source from outside.
When determining the luminance of the light source for each illuminance detected by the illuminance detecting means for each luminance level received by the receiving means, the brighter the illuminance detected by the illuminance detecting means, The luminance interval determined for each luminance level is wide, the darker the illuminance side, the narrower the interval, and the ratio of the luminance of the light source to the external illuminance at the same luminance level is always constant. Determining the brightness of the light source for each brightness level;
A luminance adjustment method comprising: changing a luminance of the light source to a luminance corresponding to the luminance level received by the receiving unit determined in the determining step. A light valve element, a light source provided in the light valve element, and at least part of the image light emitted from the light valve element is reflected and incident on the user's eye, so that it is superimposed on the real image in the user's field of view. A control program for causing a head-mounted display to function, comprising: a display unit for visually recognizing an image; illuminance detection means for detecting illuminance in the external environment; and reception means for receiving a stepwise luminance level of the light source from outside. ,
On the computer,
When determining the luminance of the light source for each illuminance detected by the illuminance detecting means for each luminance level received by the receiving means, the brighter the illuminance detected by the illuminance detecting means, The luminance interval determined for each luminance level is wide, the darker the illuminance side, the narrower the interval, and the ratio of the luminance of the light source to the external illuminance at the same luminance level is always constant. Determining each of the brightness levels for each of the brightness levels; and
A control program for executing a brightness change step for changing the brightness of the light source to a brightness corresponding to the brightness level received by the receiving means determined in the determining step.

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