Illumination device and method for driving same

Abstract

This illumination device comprises: an optical element including a light source and at least one liquid crystal cell; and a control device that is electrically connected to the light source and the optical element. The control device includes: an optical element control unit that generates a first control signal for controlling the at least one liquid crystal cell, and that outputs, in accordance with a first clock signal, a first control signal to the optical element; a light source control unit that generates a second control signal for controlling the luminance of the light source, and that outputs, in accordance with a second clock signal, a second control signal to the light source; and a timer management unit that acquires the first clock signal and controls the output of the second clock signal. When the first control signal and the second control signal are generated, the timer management unit stops the output of the second clock signal, and at a set time, starts the output of the second clock signal which was synchronized with the first clock signal.

Description

Illumination device and driving method thereof

[0001] An embodiment of the present invention relates to a lighting device that controls light distribution using a liquid crystal cell, and a method for driving a lighting device that controls light distribution using a liquid crystal cell.

[0002] In recent years, lighting devices using liquid crystal cells have been developed, which utilize the refractive index distribution of the liquid crystal contained in the liquid crystal cell to diffuse or concentrate light emitted from a light source and control the light distribution (see, for example, Patent Document 1).

[0003] JP 2016-57541 A

[0004] In lighting devices using liquid crystal cells, the light distribution is adjusted by controlling the liquid crystal cells, and the brightness is adjusted by controlling the light source. However, the frequency of the clock signal for operating the liquid crystal cells is different from the frequency of the clock signal for operating the light source. Generally, the frequency of the clock signal for operating the light source is higher than the frequency of the clock signal for operating the liquid crystal cells. Furthermore, the frequency of the clock signal for operating the light source is higher than the response speed of the liquid crystal contained in the liquid crystal cells. Therefore, when the brightness and light distribution of a lighting device are changed simultaneously, a phenomenon occurs in which the brightness changes before the light distribution changes. In other words, a time lag occurs between the change in light distribution and the change in brightness.

[0005] An object of one embodiment of the present invention is to provide a lighting device in which the time lag between a change in light distribution and a change in brightness is suppressed. Another object of one embodiment of the present invention is to provide a driving method for a lighting device in which the time lag between a change in light distribution and a change in brightness is suppressed.

[0006] An illumination device according to one embodiment of the present invention includes a light source, an optical element including at least one liquid crystal cell that transmits light emitted from the light source in a diffusible manner, and a control device electrically connected to the light source and the optical element, wherein the control device includes an optical element control unit that generates a first control signal to control the at least one liquid crystal cell and outputs the first control signal to the optical element in accordance with a first clock signal, a light source control unit that generates a second control signal to control the brightness of the light source and outputs the second control signal to the light source in accordance with the second clock signal, and a timer management unit that acquires the first clock signal and controls the output of the second clock signal, wherein the timer management unit stops outputting the second clock signal when the first control signal and the second control signal are generated and starts outputting the second clock signal synchronized with the first clock signal at a set time.

[0007] An illumination device according to one embodiment of the present invention includes a light source, an optical element including at least one liquid crystal cell that transmits light emitted from the light source in a diffusible manner, and a control device electrically connected to the light source and the optical element, wherein the control device includes an optical element control unit that generates a first control signal to control the at least one liquid crystal cell and outputs the first control signal to the optical element in accordance with a first clock signal, a light source control unit that generates a second control signal to control the brightness of the light source and outputs the second control signal to the light source in accordance with the second clock signal, and a timer management unit that acquires the first clock signal and controls the output of the second clock signal, wherein when the first control signal and the second control signal are generated, the timer management unit stops outputting the second clock signal in accordance with the falling edge of the first clock signal, and the light source control unit outputs the second control signal to the light source when the output of the second clock signal stops.

[0008] A method for driving a lighting device according to one embodiment of the present invention is a method for driving a lighting device including a light source and an optical element including at least one liquid crystal cell that transmits light emitted from the light source in a diffusible manner, the method including: generating a first control signal that controls the at least one liquid crystal cell and a second control signal that controls the brightness of the light source; stopping output of a second clock signal that controls the timing of operation of the light source; acquiring a first clock signal that controls the timing of operation of the optical element; starting output of a second clock signal synchronized with the first clock signal at a set time after output of the second clock signal has stopped; and outputting the second control signal to the light source in accordance with the second clock signal.

[0009] 1 is a schematic perspective view showing the configuration of an illumination device according to one embodiment of the present invention; FIG. 2 is a schematic top view showing the configuration of an optical element of an illumination device according to one embodiment of the present invention; FIG. 3 is a schematic cross-sectional view showing the configuration of an optical element of an illumination device according to one embodiment of the present invention; FIG. 4 is a schematic cross-sectional view showing the configuration of an optical element of an illumination device according to one embodiment of the present invention; FIG. 5 is a schematic cross-sectional view illustrating the optical characteristics of a liquid crystal cell included in the optical element of an illumination device according to one embodiment of the present invention; FIG. 6 is a block diagram showing the configuration of a control device of an illumination device according to one embodiment of the present invention; FIG. 7 is a flowchart illustrating a method for driving an illumination device according to one embodiment of the present invention; FIG. 8 is a timing chart illustrating a method for driving an illumination device according to one embodiment of the present invention; FIG. 9 is a timing chart illustrating a method for driving an illumination device according to one embodiment of the present invention;

[0010] Hereinafter, each embodiment of the present invention will be described with reference to the drawings, etc. However, the present invention can be embodied in various forms without departing from the gist of the technical idea thereof, and should not be construed as being limited to the description of the embodiments exemplified below.

[0011] In order to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples, and the illustrated shapes themselves do not limit the interpretation of the present invention. Furthermore, in the drawings, components having the same functions as those explained in relation to previous drawings in the specification may be given the same reference numerals even if they are different drawings, and overlapping explanations may be omitted.

[0012] When a single film is processed to form multiple structures, each of the multiple structures may have a different function or role. Furthermore, the substrates on which the multiple structures are formed may be different. However, these multiple structures originate from a film formed as the same layer in the same process and are made of the same material. Therefore, these multiple structures are defined as existing in the same layer.

[0013] When expressing the manner in which a structure is placed on top of another structure, the term "above" is used, unless otherwise specified, to include both a case in which another structure is placed directly above, in contact with, a structure, and a case in which another structure is placed above, via yet another structure.

[0014] First Embodiment A lighting device 1 according to one embodiment of the present invention will be described with reference to FIGS.

[0015] 1 is a schematic perspective view showing the configuration of an illumination device 1 according to an embodiment of the present invention. As shown in FIG. 1, the illumination device 1 includes an optical element 10, a light source 20, and a control device 30.

[0016] The optical element 10 and the light source 20 are arranged along the z-axis direction. The optical element 10 includes four liquid crystal cells 100 (a first liquid crystal cell 100-1, a second liquid crystal cell 100-2, a third liquid crystal cell 100-3, and a fourth liquid crystal cell 100-4). The first liquid crystal cell 100-1, the second liquid crystal cell 100-2, the third liquid crystal cell 100-3, and the fourth liquid crystal cell are stacked in this order in the z-axis direction, starting from the side closest to the light source 20. An optically elastic resin layer 160 is provided between two adjacent liquid crystal cells 100. The two adjacent liquid crystal cells 100 are bonded and fixed by the optically elastic resin layer 160. For example, an adhesive containing a light-transmitting acrylic resin can be used as the optically elastic resin layer 160. The configuration of the liquid crystal cells 100 will be described in detail below.

[0017] The number of liquid crystal cells 100 included in the optical element 10 is not limited to four. The optical element 10 only needs to include at least one liquid crystal cell 100.

[0018] The light source 20 emits light toward the optical element 10. For example, the light source 20 may be, but is not limited to, a light emitting diode (LED). The light source 20 may be any element or device that can emit light. The light source 20 may also include multiple LEDs.

[0019] Light emitted from the light source 20 to the first liquid crystal cell 100-1 of the optical element 10 passes through the four liquid crystal cells 100 included in the optical element 10 and exits from the fourth liquid crystal cell 100-4 of the optical element 10. The light passing through the optical element 10 changes its light distribution (including, for example, the light distribution angle or light distribution shape) by being diffused or concentrated. Therefore, the lighting device 1 can emit light having various light distributions controlled by the optical element 10. Furthermore, in the lighting device 1, the brightness of the light emitted from the lighting device 1 can be adjusted by controlling the luminance of the light source 20.

[0020] The optical element 10 and the light source 20 are electrically connected to a control device 30. Specifically, the control device 30 is electrically connected to each of the first to fourth liquid crystal cells 100-1 to 100-4 of the optical element 10. The control device 30 may be electrically connected via an FPC provided at the terminal portion of each of the first to fourth liquid crystal cells 100-1 to 100-4. The control device 30 controls the operation of each of the first to fourth liquid crystal cells 100-1 to 100-4 of the optical element 10. The control device 30 also controls the brightness of the light source 20. The configuration of the control device 30 will be described in detail later.

[0021] [2. Configuration of Liquid Crystal Cell 100] Figure 2 is a schematic top view showing the configuration of the optical element 10 of the lighting device 1 according to one embodiment of the present invention. The first liquid crystal cell 100-1 is located at the top of the optical element 10, and the first to fourth liquid crystal cells 100-1 to 100-4 have the same basic structure. Therefore, hereinafter, when the first to fourth liquid crystal cells 100-1 to 100-4 are not particularly distinguished from one another, the first to fourth liquid crystal cells 100-1 to 100-4 will be described as the liquid crystal cell 100. Note that Figure 2 is partially transparent so that part of the internal structure of the liquid crystal cell 100 can be seen.

[0022] The liquid crystal cell 100 includes a first substrate 111 and a second substrate 112. As will be described in detail later, a plurality of transparent electrodes 120 extending in the x-axis direction or the y-axis direction are provided on each of the first substrate 111 and the second substrate 112. Here, the angle between the x-axis direction and the y-axis direction is approximately 90 degrees. In addition, a terminal unit 121 including a plurality of terminals is provided on the second substrate 112. The terminal unit 121 is electrically connected to the control device 30, and a control signal for controlling the liquid crystal cell 100 generated by the control device 30 is input to the terminal unit 121. The transparent electrodes 120 are electrically connected to the terminals of the terminal unit 121, and a voltage included in the control signal is applied to the transparent electrodes 120 via the terminal unit 121.

[0023] Here, the detailed configuration of the optical element 10 will be described with reference to FIGS. 3A and 3B.

[0024] 3A and 3B are schematic cross-sectional views showing the configuration of the optical element 10 of the illumination device 1 according to one embodiment of the present invention. Specifically, Fig. 3A is a cross-sectional view of the optical element 10 taken along line A1-A2 in Fig. 2, and Fig. 3B is a cross-sectional view of the optical element 10 taken along line B1-B2 in Fig. 2.

[0025] As described above, the optical element 10 includes the first to fourth liquid crystal cells 100-1 to 100-4. Each of the first to fourth liquid crystal cells 100-1 to 100-4 includes a first substrate 111, a second substrate 112, a plurality of transparent electrodes 120 (a plurality of first transparent electrodes 120-1, a plurality of second transparent electrodes 120-2, a plurality of third transparent electrodes 120-3, and a plurality of fourth transparent electrodes 120-4), a first alignment film 131, a second alignment film 132, a sealant 140, and a liquid crystal layer 150. The plurality of first transparent electrodes 120-1 and the plurality of second transparent electrodes 120-2 are provided on the first substrate 111 and are covered with the first alignment film 131. Furthermore, the plurality of third transparent electrodes 120-3 and the plurality of fourth transparent electrodes 120-4 are provided on the second substrate 112 and are covered with a second alignment film 132. The first substrate 111 and the second substrate 112 are arranged such that the first transparent electrodes 120-1 and the second transparent electrodes 120-2 face the third transparent electrodes 120-3 and the fourth transparent electrodes 120-4, and are bonded together via a sealant 140 provided around the peripheries of the first substrate 111 and the second substrate 112. A liquid crystal is sealed in the space surrounded by the first substrate 111 (more specifically, the first alignment film 131), the second substrate 112 (more specifically, the second alignment film 132), and the sealant 140, and a liquid crystal layer 150 is provided between the first substrate 111 and the second substrate 112.

[0026] The first liquid crystal cell 100-1 and the second liquid crystal cell 100-2 differ from the third liquid crystal cell 100-3 and the fourth liquid crystal cell 100-4 in the arrangement pattern of the transparent electrodes 120. In the first liquid crystal cell 100-1 and the second liquid crystal cell 100-2, the first transparent electrode 120-1 and the second transparent electrode 120-2 extend in the y-axis direction, and the first transparent electrode 120-1 and the second transparent electrode 120-2 are alternately and repeatedly arranged in the x-axis direction. In addition, the third transparent electrode 120-3 and the fourth transparent electrode 120-4 extend in the x-axis direction, and the third transparent electrode 120-3 and the fourth transparent electrode 120-4 are alternately and repeatedly arranged in the y-axis direction. In contrast, in the third liquid crystal cell 100-3 and the fourth liquid crystal cell 100-4, the first transparent electrode 120-1 and the second transparent electrode 120-2 extend in the x-axis direction, and the first transparent electrodes 120-1 and the second transparent electrodes 120-2 are alternately and repeatedly arranged in the y-axis direction. Also, the third transparent electrode 120-3 and the fourth transparent electrode 120-4 extend in the y-axis direction, and the third transparent electrode 120-3 and the fourth transparent electrode 120-4 are alternately and repeatedly arranged in the x-axis direction.

[0027] As can be understood from the above description, the arrangement patterns of the transparent electrodes 120 of the third liquid crystal cell 100-3 and the fourth liquid crystal cell 100-4 rotated by 90 degrees overlap with the arrangement patterns of the transparent electrodes 120 of the first liquid crystal cell 100-1 and the second liquid crystal cell 100-2. That is, in the optical element 10, four liquid crystal cells 100 are stacked so that the arrangement patterns of the transparent electrodes 120 of two liquid crystal cells 100 are rotated by 90 degrees from the arrangement patterns of the transparent electrodes 120 of the other two liquid crystal cells.

[0028] For example, a rigid substrate having light-transmitting properties, such as a glass substrate, a quartz substrate, or a sapphire substrate, is used as each of the first substrate 111 and the second substrate 112. Alternatively, for example, a flexible substrate having light-transmitting properties, such as a polyimide resin substrate, an acrylic resin substrate, a siloxane resin substrate, or a fluororesin substrate, can also be used as each of the first substrate 111 and the second substrate 112.

[0029] Each of the first transparent electrode 120-1, the second transparent electrode 120-2, the third transparent electrode 120-3, and the fourth transparent electrode 120-4 functions as an electrode for forming an electric field in the liquid crystal layer 150. Each of the first transparent electrode 120-1, the second transparent electrode 120-2, the third transparent electrode 120-3, and the fourth transparent electrode 120-4 is made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO).

[0030] Each of the first alignment film 131 and the second alignment film 132 aligns the long axes of the liquid crystal molecules in the liquid crystal layer 150 in a predetermined direction. That is, when no voltage is applied to the transparent electrode 120, the liquid crystal molecules in the liquid crystal layer 150 are oriented according to the alignment characteristics of the first alignment film 131 or the second alignment film (for convenience, the long axis direction of the liquid crystal molecules will be referred to as the alignment direction of the liquid crystal molecules below). Each of the first alignment film 131 and the second alignment film 132 is made of a polyimide resin or the like. The first alignment film 131 and the second alignment film 132 may be given alignment characteristics by an alignment treatment such as a rubbing method or a photo-alignment method. The rubbing method is a method of rubbing the surface of the alignment film in one direction. The photo-alignment method is a method of irradiating the alignment film with linearly polarized ultraviolet light.

[0031] In the liquid crystal cell 100, alignment characteristics are imparted to the first alignment film 131 and the second alignment film 132 so that the alignment direction of the liquid crystal molecules is perpendicular to the extension direction of the transparent electrode 120. For convenience, in Figures 3A and 3B, the alignment direction of the liquid crystal molecules in the liquid crystal layer 150 is indicated using arrows and symbols with a cross inside a circle. The arrows represent the alignment direction of the liquid crystal molecules aligned parallel to the paper surface, and the symbols with a cross inside a circle represent the alignment direction of the liquid crystal molecules aligned perpendicular to the paper surface. In the first liquid crystal cell 100-1 and the second liquid crystal cell 100-2, the alignment direction of the liquid crystal molecules on the first substrate 111 side is the x-axis direction, and the alignment direction of the liquid crystal molecules on the second substrate 112 side is the axial direction. In the third liquid crystal cell 100-3 and the fourth liquid crystal cell 100-4, the alignment direction of the liquid crystal molecules on the first substrate 111 side is the y-axis direction, and the alignment direction of the liquid crystal molecules on the second substrate 112 side is the x-axis direction.

[0032] An adhesive material containing epoxy resin or acrylic resin is used as the seal material 140. The adhesive material may be an ultraviolet curing type or a thermosetting type.

[0033] The liquid crystal layer 150 contains liquid crystal. The liquid crystal layer 150 can refract light passing through it or change the polarization of the light passing through it depending on the orientation direction of the liquid crystal molecules in the liquid crystal. Nematic liquid crystal or the like is used as the liquid crystal of the liquid crystal layer 150. The liquid crystal described in this embodiment is a positive type, but it is also possible to apply a negative type instead of a positive type by changing the orientation direction of the liquid crystal molecules when no voltage is applied to the transparent electrode 120. In addition, it is preferable that the liquid crystal contains a chiral agent that imparts a twist to the liquid crystal molecules.

[0034] 3. Optical Characteristics of Liquid Crystal Cell 100 The optical characteristics of the liquid crystal cell 100 will be described with reference to FIGS. 4A and 4B.

[0035] 4A and 4B are schematic cross-sectional views illustrating the optical characteristics of the liquid crystal cell 100 included in the optical element 10 of the lighting device 1 according to one embodiment of the present invention. Specifically, Fig. 4A shows the liquid crystal cell 100 in a state where no voltage is applied to the transparent electrode 120, and Fig. 4B shows the liquid crystal cell 100 in a state where a voltage is applied to the transparent electrode 120.

[0036] As shown in FIG. 4A , the liquid crystal molecules on the first substrate 111 side in the liquid crystal layer 150 are aligned in the y-axis direction, and the liquid crystal molecules on the second substrate 112 side in the liquid crystal layer 150 are aligned in the x-axis direction. Therefore, when no voltage is applied to any of the first transparent electrode 120-1 to the fourth transparent electrode 120-4, the alignment direction of the liquid crystal molecules in the liquid crystal layer 150 changes from the y-axis direction to the x-axis direction as they move from the first substrate 111 to the second substrate 112, and the alignment is twisted by 90 degrees. In this case, the polarization plane (or polarization axis) of light passing through the liquid crystal layer 150 is rotated by 90 degrees in accordance with the alignment direction of the liquid crystal molecules. In other words, the light passing through the liquid crystal layer 150 is optically rotated. Specifically, of the light incident on the first substrate 111, a first polarized component 1000-1 having a polarization axis in the x-axis direction has its polarization axis rotated by 90 degrees when passing through the liquid crystal cell 100, and is emitted from the second substrate 112 with its polarization axis in the y-axis direction. Furthermore, of the light incident on the first substrate 111, a second polarized component 1000-2 having a polarization axis in the y-axis direction has its polarization axis rotated by 90 degrees when passing through the liquid crystal cell 100, and is emitted from the second substrate 112 with its polarization axis in the x-axis direction.

[0037] As shown in FIG. 4B , when different voltages are applied to two adjacent transparent electrodes 120, a potential difference is generated between the two adjacent transparent electrodes 120, generating an electric field (hereinafter referred to as a "transverse electric field") between the two adjacent transparent electrodes 120. In this case, the orientation state of the liquid crystal molecules in the liquid crystal layer 150 changes due to the influence of the transverse electric field. Specifically, the liquid crystal molecules in the liquid crystal layer 150 are oriented so as to be twisted 90 degrees as they move from the first substrate 111 toward the second substrate 112. The liquid crystal molecules on the first substrate 111 side are oriented in a convex arc shape in the y-axis direction due to the transverse electric field between the first transparent electrode 120-1 and the second transparent electrode 120-2, while the liquid crystal molecules on the second substrate 112 side are oriented in a convex arc shape in the x-axis direction due to the transverse electric field between the third transparent electrode 120-3 and the fourth transparent electrode 120-4. The liquid crystal molecules oriented in a convex arc shape have a refractive index distribution, and the polarized component of light having a polarization axis in the same direction as the orientation direction of the liquid crystal molecules is diffused. Specifically, the first polarized component 1000-1 has a polarization axis that is oriented in a direction different from the alignment direction of the liquid crystal molecules on the first substrate 111 side and the second substrate 112 side, and therefore the first polarized component 1000-1 is not diffused on the first substrate 111 side and the second substrate 112 side. On the other hand, the second polarized component 1000-2 has a polarization axis that is oriented in the same direction as the alignment direction of the liquid crystal molecules on the first substrate 111 side and the second substrate 112 side, and therefore the second polarized component 1000-2 is diffused on the first substrate 111 side and the second substrate 112 side.

[0038] The cell gap d, which is the distance between the first substrate 111 and the second substrate 112, is sufficiently larger than the distance between two adjacent transparent electrodes 120 (for example, 8 μm≦d≦50 μm, preferably 10 μm≦d≦30 μm, and more preferably 15 μm≦d≦25 μm). Therefore, the transverse electric field generated on the first substrate 111 side and the second substrate 112 side has almost no effect on the liquid crystal molecules located near the center between the first substrate 111 and the second substrate 112.

[0039] As described above, in the liquid crystal cell 100, the orientation of the liquid crystal molecules in the liquid crystal layer 150 can be changed by applying a voltage to the transparent electrode 120, thereby controlling the diffusion of light passing through the liquid crystal cell 100. In the lighting device 1, each of the four liquid crystal cells 100 included in the optical element 10 is controlled by the control device 30. This allows the lighting device 1 to emit light with a variety of light distributions.

[0040] 5 is a block diagram showing the configuration of the control device 30 of the lighting device 1 according to one embodiment of the present invention. As shown in Fig. 5, the control device 30 includes a data receiving unit 310, a timer management unit 320, a light distribution calculation unit 330, a brightness calculation unit 340, an optical element control unit 350, a light source control unit 360, and a D / A converter 370.

[0041] The control device 30 is a so-called computer. For example, the control device 30 includes a central processing unit (CPU), a microprocessor (MPU), or a graphics processing unit (GPU) that performs arithmetic processing using data or information. The control device 30 also includes a storage device such as a random access memory (RAM), a read-only memory (ROM), a flash memory, a hard disk drive (HDD), or a solid-state drive (SSD), or a communication interface. The control device 30 may be a microcontroller. By executing a predetermined program, the control device 30 functions as a timer management unit 320, a light distribution calculation unit 330, a brightness calculation unit 340, an optical element control unit 350, and a light source control unit 360.

[0042] The data receiving unit 310 receives data related to the illumination light emitted from the lighting device 1 (hereinafter referred to as "illumination light data"). The illumination light data is set by a user and transmitted to the control device 30. The illumination light data includes information related to the light distribution of the illumination light from the lighting device 1 (including information on the light distribution shape and light distribution angle, hereinafter referred to as "light distribution information") and information related to the brightness of the illumination light (hereinafter referred to as "brightness information"). In other words, by setting the illumination light data, the user can change the light distribution angle or light distribution shape of the illumination light from the lighting device 1 or adjust the brightness of the illumination light. Note that the illumination light data may be data that updates previously set illumination light data.

[0043] The timer management unit 320 controls the control signals output from the optical element control unit 350 and the light source control unit 360. The operation of the timer management unit 320 will be described later.

[0044] The light distribution calculation unit 330 acquires light distribution information from the illumination light data. Furthermore, the light distribution calculation unit 330 calculates a numerical value (hereinafter referred to as a "first calculated value") for controlling the light distribution in the optical element 10 based on the light distribution information. For example, the light distribution calculation unit 330 calculates, as the first calculated value, the voltage to be applied to the transparent electrode 120 of the liquid crystal cell 100 so as to obtain the light distribution shape and light distribution angle included in the light distribution information. Note that the light distribution calculation unit 330 calculates the voltage to be applied to the first transparent electrode 120-1 to the fourth transparent electrode 120-4 of each of the first liquid crystal cell 100-1 to the fourth liquid crystal cell 100-4 based on the light distribution information. However, for simplicity's sake, the following description will focus on the control by the control device 30 using one transparent electrode 120 out of the plurality of transparent electrodes 120 as an example.

[0045] The brightness calculation unit 340 acquires brightness information from the illumination light data. Furthermore, the brightness calculation unit 340 calculates a value (hereinafter referred to as a "second calculated value") necessary for controlling the brightness of the light source 20 based on the brightness information. For example, if the light source 20 operates by PWM driving, the brightness calculation unit 340 calculates a duty ratio as the second calculated value. Furthermore, for example, if the light source is current-driven, the brightness calculation unit 340 calculates a current value as the second calculated value. For simplicity of explanation, the following description will be given assuming that the light source 20 operates by PWM driving.

[0046] The optical element control unit 350 generates a signal for controlling the optical element 10. The optical element control unit 350 includes a first clock signal generation unit 351 and a first control signal generation unit 352. The first clock signal generation unit 351 generates a first clock signal that controls the timing of the operation of the optical element 10 (more specifically, the liquid crystal cell 100). The first control signal generation unit 352 generates a first control signal including a voltage to be applied to the transparent electrode 120 of the liquid crystal cell 100 based on the first calculated value. For example, the first control signal includes a pulse voltage. The first control signal is output to the optical element 10 in response to the first clock signal. The optical element 10 is electrically connected to a D / A converter 370, and the first control signal is output to the optical element 10 via the D / A converter 370.

[0047] The light source control unit 360 generates a signal for controlling the light source 20. The light source control unit 360 includes a second clock signal generation unit 361 and a second control signal generation unit 362. The second clock signal generation unit 361 generates a second clock signal that controls the timing of the operation of the light source 20. The frequency of the second clock signal is higher than the frequency of the first clock signal. The second control signal generation unit 362 generates a second control signal including a PWM signal corresponding to the duty ratio based on the second calculated value. For example, the second control signal may be a pulse voltage signal corresponding to the duty ratio. The second control signal is output to the light source 20 in accordance with the second clock signal.

[0048] The timer management unit 320 controls the second clock signal generation unit 361 to start or stop outputting the second clock signal. The timer management unit 320 also acquires the first clock signal. When the data receiving unit 310 receives illumination light data, the timer management unit 320 controls the second clock signal generation unit 361 to stop outputting the second clock signal and start outputting the second clock signal synchronized with the first clock signal based on the received illumination light data. As a result, when illumination light data newly set and updated by the user is received, a second control signal synchronized with the first control signal is output to the light source 20.

[0049] 5. Driving Method of Lighting Device 1 To explain the control by the control device 30 in more detail, a driving method of the lighting device 1 will be described with reference to FIGS. 6 and 7. FIG.

[0050] 6 is a flowchart illustrating a method for driving the lighting device 1 according to one embodiment of the present invention. The method for driving the lighting device 1 will be described below in accordance with the order of steps shown in the flowchart of FIG.

[0051] In step S100, data receiving unit 310 receives illumination light data. The received illumination light data is sent to timer management unit 320, light distribution calculation unit 330, and brightness calculation unit 340.

[0052] In step S110, the light distribution calculation unit 330 acquires light distribution information from the illumination light data and calculates a first calculated value based on the light distribution information, and the brightness calculation unit 340 acquires brightness information from the illumination light data and calculates a second calculated value based on the brightness information.

[0053] In step S120, the timer management unit 320 controls the second clock signal generation unit 361 to stop outputting the second clock signal. Note that when the output of the second clock signal is stopped, the second control signal generation unit 362 continues to output the pre-updated second control signal.

[0054] In step S130, the timer management unit 320 acquires the first clock signal generated by the first clock signal generation unit 351.

[0055] In step S140, the timer management unit 320 controls the second clock signal generation unit 361 to start outputting the second clock signal synchronized with the first clock signal.

[0056] In step S150, a first control signal is output to the optical element 10 in response to the first clock signal, and a second control signal is output to the light source 20 in response to the second clock signal. This causes the light distribution and brightness of the lighting device 1 to change based on the updated illumination light data. In step S140, the first clock signal and the second clock signal are synchronized. This makes it possible to suppress the time lag between the change in light distribution and the change in brightness of the lighting device 1.

[0057] A method for driving the lighting device 1 will be further described with reference to the timing chart shown in Fig. 7. The second control signal shown in Fig. 7 is a PWM value (any value between 0 and 100%) corresponding to the duty ratio. However, to make it easier to understand the rising and falling edges of the pulse in the pulse voltage signal, the second control signal will be described as changing from 0% to 100%.

[0058] FIG. 7 is a timing chart illustrating a driving method of the lighting device 1 according to one embodiment of the present invention. FIG. 7 shows a first control signal generated by the first control signal generating unit 352 and output to the optical element 10. The first control signal is output in response to a first clock signal generated by the first clock signal generating unit 351. Specifically, when the first control signal is updated, the updated first control signal is output to the optical element 10 in synchronization with the rising edge of the first clock signal. FIG. 7 also shows a second control signal generated by the second control signal generating unit 362 and output to the light source 20. The second control signal is output in response to a second clock signal generated by the second clock signal generating unit 361. Specifically, when the second control signal is updated, the updated second control signal is output to the light source 20 at a preset time. For example, the preset time is the time when the first clock signal rises, and the updated second control signal is output to the light source 20 in synchronization with the rising edge of the second clock signal.

[0059] When the data receiving unit 310 receives the illumination light data at time T1, the output of the second clock signal is stopped at time T1. At this time, the second control signal before update (duty ratio 0%) is output to the light source 20.

[0060] Next, the timer management unit 320 acquires the first clock signal and synchronizes the second clock signal with the first clock signal. At time T2 when the first clock signal rises, an updated first control signal (+a / 2V) is output to the optical element 10. Also, at time T2, output of the second clock signal begins, and an updated second control signal (duty ratio 100%) is output to the light source 20.

[0061] At time T3, the data receiving unit 310 receives the illumination light data, but the illumination light data is data in which only the light distribution information is updated. In this case, the output of the second clock signal is not stopped at time T3.

[0062] In the lighting device 1 according to this embodiment, when the light distribution and brightness are changed based on illumination light data, the output of the second clock signal that controls the timing of the operation of the light source 20 is stopped, and then the output of the second clock signal synchronized with the first clock signal that controls the timing of the operation of the optical element 10 is started. That is, in the lighting device 1 according to this embodiment, the operation of the optical element 10 is synchronized with the operation of the light source 20, thereby making it possible to suppress the time lag between the change in light distribution and the change in brightness.

[0063] <Modification>

[0064] A modified example of the method for driving the lighting device 1 will be described with reference to Fig. 8. Note that, in the following, description of the same configuration as that described above may be omitted.

[0065] 8 is a timing chart illustrating a method for driving the lighting device 1 according to one embodiment of the present invention. The second control signal shown in FIG. 8 is also a PWM value (any value between 0% and 100%) corresponding to the duty ratio. However, to make it easier to understand the rising and falling edges of the pulses in the pulse voltage signal, the second control signal will be described as changing from 0% to 100%.

[0066] At time T1, when illumination light data requiring updating of light distribution information and brightness information is received, output of the second clock signal is stopped. At time T2, the first control signal (+a / 2V) updated in synchronization with the rising edge of the first clock signal is output to the optical element 10. Meanwhile, the timer management unit 320 starts the first delay time t ｄｌｙ１ Then, the output of the second clock signal starts after the first delay time t2. As a result, the updated second control signal (with a duty ratio of 100%) is output to the light source 20 in synchronization with the rising edge of the second clock signal. In other words, the updated first control signal is output after the first delay time t2. ｄｌｙ１ A delayed updated second control signal is output.

[0067] First delay time t ｄｌｙ１ may be a preset value, or may be a value that varies depending on the amplitude of the voltage applied to the transparent electrode 120, which is included in the first control signal. ｄｌｙ１ may be a value set based on the difference between the first calculated value calculated from the light distribution information before and after updating. The response speed of the liquid crystal of the liquid crystal layer 150 is fast when the difference in voltage applied to the transparent electrode 120 is large, and is slow when the difference in voltage applied to the transparent electrode 120 is small. Therefore, the first delay time t ｄｌｙ１ By setting the above, it is possible to suppress a change in brightness before the light distribution changes.

[0068] In the lighting device 1 according to this modification, the first delay time t ｄｌｙ１By setting the time lag between the change in light distribution and the change in brightness, it is possible to suppress the time lag between the change in light distribution and the change in brightness. In particular, it is possible to suppress the change in brightness before the change in light distribution.

[0069] Second Embodiment In the first embodiment, a method for driving the lighting device 1 that utilizes the rising edge of the first clock signal has been described, but the lighting device 1 can also be driven by a method that utilizes the falling edge of the first clock signal. In this embodiment, another method for driving the lighting device 1 will be described with reference to Fig. 9. Note that, in the following, description of configurations similar to those described in the first embodiment may be omitted.

[0070] 9 is a timing chart illustrating a method for driving the lighting device 1 according to one embodiment of the present invention. The second control signal shown in FIG. 9 is also a PWM value (any value between 0 and 100%) corresponding to the duty ratio. However, to make it easier to understand the rising and falling edges of the pulses in the pulse voltage signal, the second control signal will be described as changing from 100% to 0%.

[0071] FIG. 9 shows a first control signal generated by the first control signal generating unit 352 and output to the optical element 10. The first control signal is output in response to the first clock signal generated by the first clock signal generating unit 351. Specifically, when the first control signal is updated, the updated first control signal is output to the optical element 10 in synchronization with the falling edge of the first clock signal. FIG. 9 also shows a second control signal generated by the second control signal generating unit 362 and output to the light source 20. The second control signal is output in response to the second clock signal generated by the second clock signal generating unit 361. Specifically, when the second control signal is updated, the updated second control signal is output to the light source at a preset time. For example, the preset time is the time when the first clock signal falls, and the second clock signal is stopped in synchronization with the falling edge of the first clock signal. As a result, the second clock signal falls, and the updated second control signal is output to the light source 20 in synchronization with the falling edge of the second clock signal. The timer management unit 320 also starts the second delay time tｄｌｙ２ This increases the stop period of the second clock signal, making it possible to ensure a sufficient time for updating the second control signal at time T2.

[0072] Even if the data receiving unit 310 receives illumination light data at time T1, the unupdated second clock signal is output until the falling edge of the first clock signal, and therefore the unupdated second control signal (duty ratio 100%) is output to the light source 20 at this time.

[0073] Next, the timer management unit 320 acquires the first clock signal and synchronizes the second clock signal with the first clock signal. At time T2 when the first clock signal falls, an updated first control signal (-a / 2V) is output to the optical element 10. Furthermore, at time T2, the output of the second clock signal is stopped. Therefore, at time T2 when the second clock signal falls, an updated second control signal (duty ratio 0%) is output to the light source. Furthermore, the timer management unit 320 calculates the second delay time t ｄｌｙ２ After that, it starts outputting the second clock signal.

[0074] The second delay time t ｄｌｙ２ is the first delay time t ｄｌｙ１ That is, the second delay time t ｄｌｙ２ may be a value set in advance, or may be a value set based on the difference between the first calculated value calculated from the light distribution information before and after updating.

[0075] In the lighting device 1 according to this embodiment, the second delay time t ｄｌｙ２ By setting the time lag between the change in light distribution and the change in brightness, it is possible to suppress the time lag between the change in light distribution and the change in brightness. In particular, it is possible to suppress the change in brightness after the change in light distribution.

[0076] Within the scope of the concept of the present invention, a person skilled in the art may conceive of various modifications and alterations, and it is understood that these modifications and alterations also fall within the scope of the present invention. For example, even if a person skilled in the art appropriately adds or deletes components or modifies the design of each of the above-described embodiments, or adds or omits steps or modifies conditions, these modifications are also included within the scope of the present invention as long as they maintain the gist of the present invention.

[0077] Furthermore, other effects and advantages brought about by each embodiment that are clear from the description in this specification or that can be appropriately conceived by a person skilled in the art are naturally understood to be brought about by the present invention.

[0078] 1: lighting device, 10: optical element, 20: light source, 30: control device, 100: liquid crystal cell, 100-1: first liquid crystal cell, 100-2: second liquid crystal cell, 100-3: third liquid crystal cell, 100-4: fourth liquid crystal cell, 111: first substrate, 112: second substrate, 120: transparent electrode, 120-1: first transparent electrode, 120-2: second transparent electrode, 120-3: third transparent electrode, 120-4: fourth transparent electrode, 121: terminal portion, 131: first alignment film, 132: second alignment film, 140: sealing material, 150: liquid crystal layer, 160: optical elastic resin layer, 310: data receiving unit, 320: timer management unit, 330: Light distribution calculation unit, 340: Calculation unit, 350: Optical element control unit, 351: First clock signal generation unit, 352: First control signal generation unit, 360: Light source control unit, 361: Second clock signal generation unit, 362: Second control signal generation unit, 370: A / D converter, 1000-1: First polarized light component, 1000-2: Second polarized light component

Claims

1. A lighting device comprising: a light source; an optical element including at least one liquid crystal cell that transmits light emitted from the light source in a diffusible manner; and a control device electrically connected to the light source and the optical element, wherein the control device comprises: an optical element control unit that generates a first control signal to control the at least one liquid crystal cell and outputs the first control signal to the optical element in accordance with a first clock signal; a light source control unit that generates a second control signal to control the brightness of the light source and outputs the second control signal to the light source in accordance with a second clock signal; and a timer management unit that acquires the first clock signal and controls the output of the second clock signal, wherein the timer management unit stops outputting the second clock signal when the first control signal and the second control signal are generated, and starts outputting the second clock signal synchronized with the first clock signal at a set time.

2. The lighting device according to claim 1, wherein the set time is the rising edge time of the first clock signal.

3. The lighting device according to claim 1, wherein the set time is a first delay time from the rising edge of the first clock signal.

4. The lighting device according to claim 3, wherein the first delay time varies depending on the amplitude of the voltage included in the first control signal.

5. An illumination device comprising: a light source; an optical element including at least one liquid crystal cell that diffusibly transmits light emitted from the light source; and a control device electrically connected to the light source and the optical element, wherein the control device comprises: an optical element control unit that generates a first control signal to control the at least one liquid crystal cell and outputs the first control signal to the optical element in accordance with a first clock signal; a light source control unit that generates a second control signal to control the brightness of the light source and outputs the second control signal to the light source in accordance with a second clock signal; and a timer management unit that acquires the first clock signal and controls the output of the second clock signal, wherein the timer management unit stops outputting the second clock signal in accordance with the falling edge of the first clock signal when the first control signal and the second control signal are generated, and the light source control unit outputs the second control signal to the light source when the output of the second clock signal stops.

6. The lighting device according to claim 5, wherein the timer management unit starts outputting the second clock signal after a second delay time has elapsed since the time when output of the second clock signal stopped.

7. The lighting device according to claim 6, wherein the second delay time varies depending on the amplitude of the voltage included in the first control signal.

8. A method for driving an illumination device including a light source and an optical element including at least one liquid crystal cell that transmits light emitted from the light source in a diffusible manner, the method comprising: generating a first control signal that controls the at least one liquid crystal cell and a second control signal that controls the brightness of the light source; stopping output of a second clock signal that controls the timing of operation of the light source; obtaining a first clock signal that controls the timing of operation of the optical element; starting output of the second clock signal synchronized with the first clock signal at a set time after output of the second clock signal has stopped; and outputting the second control signal to the light source in accordance with the second clock signal.

9. The method for driving a lighting device according to claim 8, wherein the set time is the rising edge time of the first clock signal.

10. The method for driving a lighting device according to claim 8, wherein the set time is a first delay time from the rising edge of the first clock signal.

11. The method for driving a lighting device according to claim 10, wherein the first delay time varies depending on the amplitude of a voltage included in the first control signal.

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