Lighting device and driving method thereof

Abstract

The lighting device includes a light source, an optical element including at least two liquid crystal cells overlapping each other on the light source, and a control device that drives the optical element. Each of the at least two liquid crystal cells has a plurality of first electrodes and a plurality of second electrodes alternately arranged in a stripe shape, a liquid crystal layer on the plurality of first electrodes and the plurality of second electrodes, and a liquid crystal layer on the liquid crystal layer, the liquid crystal layer intersecting the plurality of first electrodes and the plurality of second electrodes, and a plurality of third electrodes and a plurality of fourth electrodes alternately arranged in a stripe shape. The control device is configured so that a first input signal and a second input signal of a pulse width modulation system are input to the control device. The control device is further configured to convert the first input signal and the second input signal into a first output signal and a second output signal of a pulse amplitude type, respectively, according to a duty ratio, and supply the first output signal and the second output signal to the optical element.

Description

Technical Field

[0001] One embodiment of the present invention relates to a lighting device and a driving method thereof. For example, one embodiment of the present invention relates to a lighting device and a driving method thereof that utilize the alignment of liquid crystals for light distribution control. Background Art

[0002] There is known an optical element, so-called a liquid crystal lens, which utilizes the fact that by controlling the voltage applied to the liquid crystal, the alignment of the liquid crystal is controlled and the refractive index of the liquid crystal layer changes. Since the light from the light source can be diffused by controlling the refractive index of the liquid crystal layer by disposing this optical element on the light source, a lighting device capable of performing light distribution control can be provided (for example, see Patent Document 1).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2021-117344 Summary of the Invention

[0006] Technical Problem to be Solved by the Invention

[0007] An object of one embodiment of the present invention is to provide a lighting device and a driving method thereof having a novel structure. For example, an object of one embodiment of the present invention is to provide a lighting device and a driving method thereof that can perform light distribution control based on an input signal in a pulse width modulation method.

[0008] Technical Solution for Solving the Technical Problem

[0009] One embodiment of the present invention is a lighting device. The lighting device includes a light source, an optical element, and a control device that drives the optical element. The optical element is configured to transmit the light emitted from the light source and includes at least two liquid crystal cells that overlap each other. The at least two liquid crystal cells each have a plurality of first electrodes and a plurality of second electrodes that are alternately arranged in a stripe shape; a liquid crystal layer on the plurality of first electrodes and second electrodes; and a plurality of third electrodes and a plurality of fourth electrodes that are arranged on the liquid crystal layer, cross the plurality of first electrodes and the plurality of second electrodes, and are alternately arranged in a stripe shape. The control device is configured to be input with a first input signal and a second input signal in a pulse width modulation method that specify the diffusion degree of the diffusion of light by the optical element in the direction in which the plurality of first electrodes extend and in the direction in which the plurality of third electrodes extend. The control device is further configured to convert the first input signal and the second input signal into a first output signal and a second output signal in a pulse amplitude method according to the duty ratio and supply them to the optical element.

[0010] One embodiment of the present invention is a driving method for a lighting device. The lighting device includes a light source, an optical element, and a control device for controlling the optical element. The optical element is configured to transmit light emitted from the light source and includes at least two liquid crystal cells overlapping each other. The at least two liquid crystal cells each have a plurality of first electrodes and a plurality of second electrodes alternately arranged in a stripe pattern; a liquid crystal layer on the plurality of first electrodes and second electrodes; and a plurality of third electrodes and a plurality of fourth electrodes arranged on the liquid crystal layer, intersecting with the plurality of first electrodes and the plurality of second electrodes and alternately arranged in a stripe pattern. The driving method includes inputting a first input signal and a second input signal in a pulse width modulation mode, which specify the diffusion degrees of the optical element for diffusing light in the direction in which the plurality of first electrodes extend and in the direction in which the plurality of third electrodes extend, into the control device, and converting the first input signal and the second input signal into a first output signal and a second output signal in a pulse amplitude mode respectively according to the duty ratio and supplying them to the optical element. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic perspective view of a lighting device according to one embodiment of the present invention.

[0012] Figure 2 is a block diagram showing the structure of a lighting device according to one embodiment of the present invention.

[0013] Figure 3 is a schematic end view of a lighting device according to one embodiment of the present invention.

[0014] Figure 4 is a schematic end view of a lighting device according to one embodiment of the present invention.

[0015] Figure 5 is a schematic top view showing the electrode pattern of a liquid crystal cell included in the optical element of a lighting device according to one embodiment of the present invention.

[0016] Figure 6 is a schematic top view showing the electrode pattern of a liquid crystal cell included in the optical element of a lighting device according to one embodiment of the present invention.

[0017] Figure 7 is a schematic end view for explaining light diffusion by the optical element of a lighting device according to one embodiment of the present invention.

[0018] Figure 8 is a schematic end view for explaining light diffusion by the optical element of a lighting device according to one embodiment of the present invention.

[0019] Figure 9 is a block diagram showing the structure of the control device of a lighting device according to one embodiment of the present invention.

[0020] Figure 10 It is a schematic diagram showing a driving method of a lighting device according to one embodiment of the present invention.

[0021] Figure 11 It is a flowchart illustrating an example of a driving method of a lighting device according to one embodiment of the present invention.

[0022] Figure 12 It is a flowchart illustrating an example of a driving method of a lighting device according to one embodiment of the present invention.

[0023] Figure 13 It is an equivalent circuit of a processing circuit included in a driving circuit of a lighting device according to one embodiment of the present invention. Detailed Embodiments

[0024] Hereinafter, various embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention can be implemented in various ways without departing from its gist, and the description of the embodiments illustrated below should not be construed as a limitation on the present invention.

[0025] For the sake of clearer illustration, the width, thickness, shape, etc. of each part may be schematically shown compared with the actual situation, but this is only an example and should not be regarded as a limitation on the interpretation of the present invention. In this specification and each figure, for elements having the same function as those in the figures that have already appeared, the same reference numerals are used, and repeated descriptions are omitted. This symbol is used when representing a plurality of structures having the same or similar overall structures, and when representing these structures individually, a hyphen and a natural number are added after the symbol.

[0026] In this specification and the claims, when describing that another structure is disposed on a certain structure, in the case of only being labeled as "above", unless otherwise specifically stated, it should be understood to include both the case where another structure is disposed directly above in contact with a certain structure and the case where another structure is disposed above a certain structure via another structure.

[0027] In this specification and the claims, when describing that two structures are "orthogonal", it not only refers to the state where the two structures intersect vertically (90°), but also includes the state where they intersect at an angle of 90° ± 10°. When describing that two structures are "parallel", it includes the case where the angle between the extending directions of the two structures is 0° ± 10°.

[0028] Next, a lighting device 100 and its driving method related to one embodiment of the present invention will be described.

[0029] 1. Configuration of the Lighting Device

[0030] Figure 1This is a schematic perspective view showing the configuration of the lighting device 100 according to an embodiment of the present invention. As Figure 1 shown, the lighting device 100 includes an optical element 110, a light source 102, and Figure 1 a control device not shown in the figure. The lighting device 100 may further include an input device ( Figure 1 not shown in the figure) for outputting a signal for controlling the optical element 110 and inputting it to the control device 150. The input device may also be configured to be able to control the intensity of the light of the light source 102 via the control device or directly.

[0031] The light source 102 is arranged and configured to emit light toward the optical element 110. There is no limitation on the light-emitting element included in the light source 102. For example, a light-emitting diode (LED), a cold cathode tube, etc. may be used.

[0032] The optical element 110 is arranged on the light source 102 and configured to allow the light emitted from the light source 102 to pass through. The optical element 110 includes at least two liquid crystal cells 120 overlapping each other on the light source 102. The number of liquid crystal cells 120 included in the optical element 110 may be three or more. In the optical element 110 shown in Figure 1 the figure, four liquid crystal cells (a first liquid crystal cell 120-1, a second liquid crystal cell 120-2, a third liquid crystal cell 120-3, and a fourth liquid crystal cell 120-4) are arranged on the light source 102 in the order approaching the light source 102. In the following description, the lighting device 100 having an optical element 110 including four liquid crystal cells 120 will be described as an example. In addition, the direction from the light source 102 toward the optical element 110 is defined as the z direction.

[0033] The light emitted from the light source 102 is incident on the first liquid crystal cell 120-1 and emitted from the fourth liquid crystal cell 120-4. As will be described later, in the lighting device 100, the diffusion of light can be controlled by the liquid crystal cells 120 included in the optical element 110, and the light distribution of the light emitted from the optical element 110 can be changed. That is, the light from the light source 102 can be processed, and the shape of the surface (irradiation surface) of the object irradiated with the light can be changed.

[0034] Figure 2 This shows a block diagram representing the configuration of the lighting device 100. As Figure 1 , Figure 2As shown, each liquid crystal cell 120 is connected to a connector 108 such as a flexible printed circuit (FPC) substrate and is connected to a control device 150 via the connector 108. Thus, the optical element 110 is controlled by the control device 150. The control device 150 may be configured to be connected to the light source 102 to control the light source 102. Although not shown, as described above, the light source 102 may also be directly controlled by the input device 104. The control device 150 and the optical element 110 will be described in detail below.

[0035] 2. Optical Element

[0036] Along Figure 1 Schematic views of the end faces of the optical element 110 along the dash-dotted line A-A' and the dash-dotted line B-B' orthogonal thereto are shown in Figure 3 and Figure 4 . As shown in these figures, each of the first liquid crystal cell 120-1 to the fourth liquid crystal cell 120-4 has a first substrate 122 and a second substrate 124 facing each other, and a plurality of first electrodes 126-1, a plurality of second electrodes 126-2, a plurality of third electrodes 126-3, a plurality of fourth electrodes 126-4, a first alignment film 128-1, and a second alignment film 128-2 are provided therebetween. The plurality of first electrodes 126-1 and the plurality of second electrodes 126-2 are provided on the first substrate 122, and the first alignment film 128-1 is formed on these electrodes. The plurality of third electrodes 126-3 and the plurality of fourth electrodes 126-4 are provided under the second substrate 124 and are disposed between the second substrate 124 and the second alignment film 128-2. The first substrate 122 and the second substrate 124 are fixed to each other by a sealing material 132, and a liquid crystal layer 130 is sealed in a space surrounded by the first substrate 122, the second substrate 124, and the sealing material 132. An adhesive 134 that transmits visible light is provided between adjacent liquid crystal cells 120, whereby the adjacent liquid crystal cells 120 are fixed to each other. For example, an acrylic resin-based adhesive or an epoxy resin-based adhesive can be used as the adhesive 134.

[0037] (1)Substrate

[0038] The first substrate 122 and the second substrate 124 are configured to transmit at least visible light among the light emitted from the light source 102. For example, a light-transmissive substrate such as a glass substrate or a quartz substrate can be used as the first substrate 122 and the second substrate 124. The first substrate 122 and the second substrate 124 may contain light-transmissive polymers such as polyimide, polyamide, polycarbonate, acrylic resin, and polysiloxane. The plurality of liquid crystal cells 120 are appropriately arranged on the light source 102 such that the normal direction of the first substrate 122 and the second substrate 124 is the z direction and the main plane is the xy plane.

[0039] (2)Electrode

[0040] Each electrode 126 functions as an electrode for forming a lateral electric field in the liquid crystal layer 130. The electrode 126 can use a conductive oxide that transmits visible light, such as indium / tin oxide (ITO) or indium / zinc oxide (IZO). Alternatively, the electrode 126 can include a metal such as aluminum, tantalum, molybdenum, tungsten, or an alloy thereof. However, in order to ensure light transmittance with respect to visible light, it is preferable to form the electrode 126 in a mesh shape with a plurality of openings.

[0041] As Figure 3 and Figure 4 shown, the first electrode 126-1 and the second electrode 126-2 are arranged in a stripe shape, parallel to each other, and alternately arranged. Therefore, one second electrode 126-2 is provided between adjacent first electrodes 126-1, and one first electrode 126-1 is provided between adjacent second electrodes 126-2. Similarly, the third electrode 126-3 and the fourth electrode 126-4 are also arranged in a stripe shape, parallel to each other, and alternately arranged. Therefore, one fourth electrode 126-4 is provided between adjacent third electrodes 126-3, and one third electrode 126-3 is provided between adjacent fourth electrodes 126-4. However, the extending directions of the first electrode 126-1 and the second electrode 126-2 cross or are orthogonal to the extending directions of the third electrode 126-3 and the fourth electrode 126-4.

[0042] Here, between the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, the extending directions of the first electrode 126-1 and the second electrode 126-2 are the same as each other, and the extending directions of the third electrode 126-3 and the fourth electrode 126-4 are also the same as each other. Between the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4, their relationship is the same. However, between the second liquid crystal cell 120-2 and the third liquid crystal cell 120-3, the extending directions of the first electrode 126-1 (or the second electrode 126-2) are orthogonal to each other, and the extending directions of the third electrode 126-3 (or the fourth electrode 126-4) are also orthogonal to each other. Although not shown, in the case where the optical element 110 is composed of two liquid crystal cells 120, the optical element 110 can be configured such that between these liquid crystal cells 120, the extending directions of the first electrode 126-1 (or the second electrode 126-2) are the same as each other, and the extending directions of the third electrode 126-3 (or the fourth electrode 126-4) are also the same as each other. Below, as Figure 3 and Figure 4 shown, the extending direction of the first electrode 126-1 and the second electrode 126-2 of the first liquid crystal cell 120-1 is set as the y direction, and the extending direction of the third electrode 126-3 and the fourth electrode 126-4 is set as the x direction, and the description will continue.

[0043] As an example,Figure 5 and Figure 6 are respectively schematic top views showing the patterns of the electrodes 126 formed on the first substrate 122 and the second substrate 124 of the liquid crystal cell 120. As Figure 5 shown, a plurality of first electrodes 126-1 and a plurality of second electrodes 126-2 arranged in a striped pattern are provided on the first substrate 122. The plurality of first electrodes 126-1 are electrically connected to each other to form a comb-like pattern. Similarly, the plurality of second electrodes 126-2 are also electrically connected to each other to form a comb-like pattern. The comb patterns of the first electrodes 126-1 and the second electrodes 126-2 extend to one side of the first substrate 122 and are electrically connected to the connector 108 (refer to Figure 1 ). Connection wirings 144 and 146 for electrically connecting the third electrode 126-3, the fourth electrode 126-4, and the connector 108 are provided on the first substrate 122.

[0044] Similarly, a plurality of third electrodes 126-3 and a plurality of fourth electrodes 126-4 arranged in a striped pattern are provided on the second substrate 124. The plurality of third electrodes 126-3 are electrically connected to each other to form a comb-like pattern, and the plurality of fourth electrodes 126-4 are also electrically connected to each other to form a comb-like pattern (refer to Figure 6 . It should be noted that, for ease of understanding, Figure 6 the state viewed from the Z+ direction is shown in the same manner as Figure 5 , and the respective electrodes provided through the substrates are represented by solid lines). The comb patterns of the third electrodes 126-3 and the fourth electrodes 126-4 extend to one side of the second substrate 124 to form terminals 140 and 142. When the first substrate 122 and the second substrate 124 are bonded to each other, the terminals 140 and 142 are electrically connected to the connection wirings 144 and 146 via a conductive material (not shown), respectively. Therefore, a voltage can be applied to all the electrodes 126 from the control device 150 via the connector 108 arranged on the first substrate 122 to drive the liquid crystal cell 120. The same applies to other liquid crystal cells 120. Therefore, the plurality of liquid crystal cells 120 can be driven independently of each other.

[0045] (3) Alignment layer

[0046] In each liquid crystal cell 120, the first alignment layer 128-1 covers the plurality of first electrodes 126-1 and the plurality of second electrodes 126-2, and the second alignment layer 128-2 covers the plurality of third electrodes 126-3 and the plurality of fourth electrodes 126-4. The alignment layer 128 includes a polymer such as polyimide. Each alignment layer 128 is given alignment characteristics through an alignment treatment such as a rubbing method or a photo-alignment method. Thus, it functions to align the liquid crystal molecules included in the liquid crystal layer 130 in a certain direction. Hereinafter, the direction in which the alignment layer 128 aligns the liquid crystal molecules so that their longitudinal directions are aligned will be referred to as the alignment direction.

[0047] In each liquid crystal cell 120, the alignment direction of the first alignment film 128-1 is orthogonal to the direction in which the first electrode 126-1 and the second electrode 126-2 extend. Similarly, the alignment direction of the second alignment film 128-2 is orthogonal to the direction in which the third electrode 126-3 and the fourth electrode 126-4 extend. Therefore, in each liquid crystal cell 120, the alignment directions of the first alignment film 128-1 and the second alignment film 128-2 are orthogonal to each other.

[0048] (4)Liquid crystal layer

[0049] The liquid crystal layer 130 can refract the transmitted light or change the polarization state of the transmitted light according to the alignment state of the liquid crystal molecules. Nematic liquid crystal can be used as the liquid crystal of the liquid crystal layer 130. The liquid crystal layer 130 can include a chiral agent for imparting twist to the liquid crystal.

[0050] (5)Control of light distribution

[0051] The following will use Figure 7 and Figure 8 to illustrate the control of light distribution using the optical element 110. Figure 7 and Figure 8 are schematic end views for illustrating the optical characteristics of one liquid crystal cell 120, corresponding to the state where no voltage is applied to the electrode 126 and the state where voltage is applied to the electrode 126, respectively.

[0052] As Figure 7 shows, according to the alignment direction of the alignment film 128, the liquid crystal molecules on the first substrate 122 side of the liquid crystal layer 130 are aligned in the x direction, and the liquid crystal molecules on the second substrate 124 side of the liquid crystal layer 130 are aligned in the y direction. Therefore, in the electric field-free state where no voltage is applied to any of the first electrode 126-1 to the fourth electrode 126-4, the liquid crystal molecules in the liquid crystal layer 130 will be aligned in a manner of twisting by 90° in the xy plane in the direction from the first substrate 122 toward the second substrate 124. In addition, the light transmitted through the liquid crystal layer 130 will rotate the polarization plane (the orientation of the polarization axis or polarization component) by 90° according to the alignment direction of the liquid crystal molecules. That is, the light transmitted through the liquid crystal layer 130 (more specifically, the polarization component of the transmitted light) is optically active.

[0053] When a voltage is applied to the first electrode 126-1 to the fourth electrode 126-4 so that a potential difference is generated between adjacent electrodes 126, a lateral electric field is generated between two adjacent electrodes 126. As a result, as Figure 8As shown, the liquid crystal molecules in the liquid crystal layer 130 are oriented in a 90°-twisted manner in the xy plane as they move from the first substrate 122 toward the second substrate 124. At the same time, the liquid crystal molecules near the first substrate 122 side are arranged in a convex arc shape relative to the first substrate 122 due to the transverse electric field between the first electrode 126-1 and the second electrode 126-2, and the liquid crystal molecules near the second substrate 124 side are arranged in a convex arc shape relative to the second substrate 124 due to the transverse electric field between the third electrode 126-3 and the fourth electrode 126-4. The liquid crystal molecules arranged in a convex arc shape have a refractive index distribution such that light with a polarization axis in the same direction as the orientation direction of the liquid crystal molecules is diffused. It should be noted that the cell gap d between the first substrate 122 and the second substrate 124 is much larger than the distance between two adjacent transparent electrodes (for example, 8 μm ≤ d ≤ 50 μm, more preferably 10 μm ≤ d ≤ 30 μm, and further preferably 15 μm ≤ d ≤ 25 μm). Therefore, the electric field formed between the above electrodes 126 has almost no effect on the liquid crystal molecules near the center between the first substrate 122 and the second substrate 124.

[0054] The light emitted from the light source 102 includes a polarization component in the x direction (P polarization component) and a polarization component in the y direction (S polarization component). Hereinafter, for the sake of convenience of explanation, the light emitted from the light source 102 is divided into light Lp with a P polarization component and light Ls with an S polarization component for explanation.

[0055] Since the polarization plane of the light Lp incident from the first substrate 122 side is the same as the orientation direction of the liquid crystal molecules on the first substrate 122 side, the light Lp is diffused in the x direction according to the refractive index distribution of the liquid crystal molecules (refer to (1) in Figure 8 ). In addition, the light Lp rotates in the process of passing through the liquid crystal layer 130, and the polarization component changes from the P polarization component to the S polarization component. Since the polarization plane of the S polarization component of the light Lp is the same as the orientation direction of the liquid crystal molecules on the second substrate 124 side, the light Lp is diffused in the y direction according to the refractive index distribution of the liquid crystal molecules (refer to (2) in Figure 8 ).

[0056] On the other hand, since the polarization plane of the light Ls incident from the first substrate 122 side is different (orthogonal) from the orientation direction of the liquid crystal molecules on the first substrate 122 side, the light Ls is not diffused (refer to (3) in Figure 8 ). In addition, the light Ls rotates in the process of passing through the liquid crystal layer 130, and the polarization component changes from the S polarization component to the P polarization component. The P polarization component of the light Ls is different (orthogonal) from the orientation direction of the liquid crystal molecules on the second substrate 124 side, so the light Ls is not diffused (refer to (4) in Figure 8 ).

[0057] Thus, light passes through a liquid crystal cell 120, and thus one polarization component is selectively diffused. Although not shown, since the light Ls that has passed through the first liquid crystal cell 120-1 can be diffused in the x-direction and the y-direction by passing through the second liquid crystal cell 120-2 based on the same principle, by using two overlapping liquid crystal cells 120, all polarization components can be diffused in the x-direction and the y-direction. In addition, since the degree of diffusion (diffusion degree) can also be changed by changing the voltage applied to the electrode 126, by overlapping a plurality of liquid crystal cells 120 and controlling the voltage applied to each electrode 126, the light can be arbitrarily diffused in the x-direction and the y-direction. As a result, the shape of the light irradiation surface from the light source 102 can be deformed into various shapes such as a circle, an ellipse, a cross, etc.

[0058] 3. Control Device and Driving Method of Lighting Device Using the Control Device

[0059] (1) Configuration of Control Device

[0060] The control device 150 is a device that determines the voltage applied to the electrode 126 of the liquid crystal cell 120 of the optical element 110 according to an input signal in pulse width modulation mode input from the input device 104, and supplies an output signal in pulse amplitude modulation mode to the electrode 126. As shown in the block diagram of Figure 2 , the control device 150 is connected to a power supply 106, and thus power is supplied to the control device 150. The power supply 106 is configured to generate two different voltages V 1 and V 2 . For example, the power supply 106 can generate voltages V 1 and V 2 of 3.3V and 30V respectively.

[0061] The control device 150 includes a signal generation circuit unit 160 and a voltage application unit 190. The signal generation circuit unit 160 is an integrated circuit having an arithmetic function and operates based on a predetermined program. The signal generation circuit unit 160 is constituted by, for example, a central processing unit (CPU), a microprocessor (MPU), an integrated circuit (IC), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), etc. The signal generation circuit unit 160 may also include a random access memory (RAM) and a non-volatile memory such as a flash memory or a read-only memory. The signal generation circuit unit 160 receives the voltage V 1supply, and performs arithmetic processing on the input signal input from the input device 104 according to a program. As described above, the lighting device 100 is configured to independently control the diffusion of light from the light source 102 in two directions (x direction and y direction). Therefore, the input signal from the input device 104 includes two independent signals (a first signal and a second signal, represented as PWM X and PWM Y in Figure 2 ), and either signal is input to the control device 150 in a pulse width modulation manner. It should be noted that the control device 150 can also be configured such that when the control device 150 controls the light source 102, a signal (Int.) for controlling the intensity and color of the light from the light source 102 is input from the input device 104 to the signal generation circuit section 160. The signal Int. is also input as a pulse width modulation signal.

[0062] Figure 9 FIG. shows a block diagram showing the configuration of the signal generation circuit section 160. The signal generation circuit section 160 includes signal conversion sections (a first signal conversion section 162-1 and a second signal conversion section 162-2) for respectively processing the first signal and the second signal, and each signal conversion section 162 can include a counting circuit 164, a division circuit 166, a processing circuit 168, a filter circuit 170, a correction circuit 172, and a voltage calculation circuit 174 as a voltage application calculation section as main components.

[0063] The counting circuit 164 and the division circuit 166 calculate the duty ratio of the input signal input from the input device 104 to the signal generation circuit section 160. It should be noted that when the duty ratio of the input signal is 1 (100%) or 0 (0%), the potential of the input signal is all High or Low throughout a plurality of frame periods, so sometimes the duty ratio cannot be obtained by the counting circuit 164 and the division circuit 166. Therefore, the processing circuit 168, which is a circuit for performing exceptional processing, is used to generate a signal indicating that the duty ratio is 1 or 0. The filter circuit 170 performs a filtering process on the calculated duty ratio, removes exceptional values, or is used to reduce the deviation of the duty ratio caused by minute changes in the pulse width of each frame of the input signal. Examples of such processing include median filtering processing and average filtering processing. The correction circuit 172 obtains the diffusion degree by referring to a look-up table showing the relationship between the duty ratio of the input signal and the degree of diffusion of the light from the light source 102 through the optical element 110, that is, the diffusion degree. The voltage calculation circuit 174 calculates / decides the voltage supplied to each electrode 126 based on the diffusion degree, and generates a voltage signal to supply to the voltage application section 190. The look-up table can be embedded in the program that operates the signal generation circuit section 160, or stored in a non-volatile memory (not shown).

[0064] The voltage application section 190 (refer toFigure 9 and Figure 2 ), and includes a plurality of pairs of digital-to-analog conversion circuits (DACs) 192 and amplifier circuits (AMPs) 194 corresponding to respective electrodes 126 of the liquid crystal cells 120. In other words, one channel (ch) is formed by a pair of digital-to-analog conversion circuit 192 and amplifier circuit 194, and each electrode 126 is connected to the channel formed by the pair of digital-to-analog conversion circuit 192 and amplifier circuit 194. Therefore, voltages can be independently supplied to the electrodes 126 respectively. The digital-to-analog conversion circuit 192 is connected to the signal generation circuit section 160 through a serial bus such as a serial peripheral interface (SPI). The digital-to-analog conversion circuit 192 and the amplifier circuit 194 are respectively supplied with voltages V 1 and V 2 . The voltage signal output from the signal generation circuit section 160 is converted into a digital signal by the digital-to-analog conversion circuit 192, amplified by the amplifier circuit 194, and supplied to the electrode 126 as a pulse amplitude modulation signal.

[0065] (2) Driving method of the lighting device

[0066] As described above, the first input signal and the second input signal input from the input device 104 are processed by the control device 150. However, since these processes are the same, one input signal is used to describe the driving method of the lighting device 100.

[0067] As Figure 10 shown, in the lighting device 100, the input of the diffusivity of the light from the light source 102 in the x direction and the y direction uses the input signal as a pulse width modulation signal. During each frame period, a period corresponding to the diffusivity, a high potential (High) or a low potential (Low) is input from the input device 104. The period of the frame period is 30 Hz or more and 120 Hz or less, preferably 60 Hz or more and 120 Hz or less. When the period of one frame period is within the above range, the voltage applied to the electrode 126 can be held by the capacitance of the liquid crystal layer 130. Through the control device 150, the duty ratio (period of high potential / frame period) of the input signal is converted into the voltage amplitude ratio of the output signal in pulse width modulation mode, and a voltage corresponding to the voltage amplitude ratio is applied to each electrode 126. In the input device 104, for example, a slider or a knob (pinch portion) for specifying the diffusivity of the light is provided, and the diffusivity is input by the sliding amount of the slider or the rotation amount of the knob. The input device 104 may further be configured to be able to adjust the brightness and color of the light from the light source 102.

[0068] Figure 11 and Figure 12An example of a flowchart showing this driving method is presented. In the control device 150, after the start of a frame period, the potential of the input signal is judged to be High or Low at regular intervals (for example, at intervals of 1 / 200 to 1 / 2000 of a frame period) using a clock signal (S100). Here, when it is judged that the potential of the input signal is High (S100: Yes), the counting of High starts in the counting circuit 164 (S102). At this time, if the 1-frame period (i.e., this frame period) has not elapsed, the count of High is incremented by one (S104).

[0069] Next, at regular intervals after the start of this frame period, it is judged whether the input signal maintains a High potential (S106). If the potential of the input signal remains High, it is again judged whether the frame period has elapsed (S103). If the frame period has not elapsed (S103: No), the count of High is again incremented by one (S104), and it is again judged whether the input signal maintains a High state (S106). Then, if the duty ratio is greater than 0% and less than 100%, before the frame period elapses, the potential of the input signal becomes Low (S106: No), so the value of the count accumulated at the time when the potential of the input signal becomes Low corresponds to the High period. This High period is output from the counting circuit 164 to the division circuit 166 (S108).

[0070] On the other hand, when the duty ratio is 100%, a Low signal is not input throughout the 1-frame period (the High potential is maintained throughout the frame period). Therefore, the loop of the above steps S103 to S106 is repeatedly performed throughout the frame period. In addition, in order to indicate that the input signal is always High when the frame period has elapsed (S103: Yes), the flag is set to High being fixed, and for example, the High potential is output as a flag potential indicating this to the processing circuit 168 (S110). The processing in the processing circuit 168 will be described later. After that, when the input signal still maintains High, the flag will be fixed, but when the input signal then becomes Low, the flag will be released, and for example, the Low potential is output as a flag potential for indicating that the input signal has become Low to the processing circuit 168 (S112). That is, in Figure 11 the shown flowchart, from the situation of passing through step S108 to the end, it indicates that before the end of the frame period, the input signal becomes Low. In this case, it returns to the start of this flowchart again, passes through S100 and reaches Figure 12 the flowchart. On the other hand, in the case of ending after passing through step S112, it indicates that the frame period has been completed, returns to the start of this flowchart and starts the next frame period.

[0071] Further, when the potential of the input signal is maintained at Low at the start of the frame period, or when the potential of the input signal changes from High to Low during a frame period as described above (S100: No), the counting of Low starts ( Figure 12 , S120). If one frame period has not elapsed since the start of this frame period, the count of Low is incremented by one (S122). In this case, it is also determined again at regular intervals whether the input signal is High or Low (S124). If the input signal still maintains a Low potential, it is determined again whether one frame period has elapsed (S121), and if one frame period has not elapsed (S121: No), the count of Low is incremented by one again (S122), and it is determined again whether the input signal maintains a Low state (S124). If the duty ratio is greater than 0% and less than 100%, before the end of this frame period, the input signal becomes High (S124: No), so the value of the count accumulated at the time when the input signal becomes High corresponds to the period of Low. This period of Low is output to the division circuit 166 (S126).

[0072] On the other hand, in the case where the duty ratio is 0%, a High signal is not input during this frame period. Therefore, in order to indicate that the input signal is always Low in this frame when one frame period has elapsed, the flag is set to Low being fixed, and for example, a High potential is output to the processing circuit 168 as a flag potential indicating this (S128). The processing in the processing circuit 168 will be described later. After that, when the input signal still maintains Low, the flag will be fixed, but next when the input signal becomes High, the flag will be released, and for example, a Low potential is output to the processing circuit 168 as a flag potential indicating that the input signal has become High (S130).

[0073] The calculation of the duty ratio is performed by the division circuit 166. The sum of the period of High obtained in step S108 and the period of Low obtained in step S126 is output as the frame period, the ratio of the period of High to the frame period is calculated as the duty ratio, and a potential corresponding to the duty ratio is output to the processing circuit 168 (S132). After that, the counting circuit 164 is reset (S134). In this way, in the case where the duty ratio is neither 0% nor 100%, in Figure 11 and Figure 12 In the flowchart shown, after reaching S108 from the start of Figure 11 , it is transferred to Figure 12 again via S100 and then to Figure 11 the flowchart until step S134. Then, when reaching this step S134, this frame period ends, the next frame period starts and returns to Figure 11At the start. In addition, when the duty ratio is 0%, the process starting from Figure 11 goes through S100, S120, S128 to S130, and the frame period ends. After that, the next frame period starts and returns to Figure 11 the start. Additionally, when the duty ratio is 100%, the process starting from Figure 11 goes through steps S100, S110 to S112, and the frame period ends. After that, the next frame period starts and returns to Figure 11 the start.

[0074] When the duty ratio is 100% or 0%, exception handling is performed in the processing circuit 168. An example of the equivalent circuit of the processing circuit 168 is shown in Figure 13 . Figure 13 The illustrated processing circuit 168 has an OR circuit 176, a first multiplexer 178, and a second multiplexer 180. Two input terminals of the OR circuit 176 are connected to the counting circuit 164, and flag signals indicating that the input signal is fixed to High and Low are respectively input. The output terminal of the OR circuit 176 is connected to the selection control input terminal of the second multiplexer 180. Therefore, when the input signal is fixed to High or Low, a selection control signal of High is input to the second multiplexer 180. Two input terminals and the selection control input terminal of the first multiplexer 178 are connected to the counting circuit. A flag signal indicating the potential of the input signal fixed to High is input to one input terminal and the selection control input terminal of the first multiplexer 178, and a flag signal for indicating the potential of the input signal fixed to Low is input to the other input terminal. One input terminal of the second multiplexer 180 is connected to the division circuit 166 and a potential corresponding to the duty ratio is input, and the other input terminal is connected to the output terminal of the first multiplexer 178.

[0075] Therefore, in the case where no flag signal indicating that the potential of the input signal is fixed to High or Low is input, a potential corresponding to a duty ratio greater than 0% and less than 100% calculated by the division circuit 166 is output from the second multiplexer 180. On the other hand, when a flag signal indicating that the potential of the input signal is fixed to High is input to the OR circuit 176, a potential indicating a duty ratio of 100% is output from the second multiplexer 180. Conversely, when a flag signal indicating that the potential of the input signal is fixed to Low is input to the OR circuit 176, a potential indicating a duty ratio of 0% is output from the second multiplexer 180. It should be noted that the configuration of the processing circuit 168 is not limited to the above configuration, and any configured circuit can also be used as long as it can achieve the above functions.

[0076] After the above processing, the signal output from the processing circuit 168 is processed by the filter circuit 170 and the correction circuit 172 to determine the diffusion degree. Based on this diffusion degree, the voltage calculation circuit 174 calculates the voltage supplied to each electrode 126 and supplies it as a voltage signal to the voltage application unit 190.

[0077] The voltage signal output from the signal generation circuit unit 160 is digitally converted by the digital-to-analog conversion circuit 192. As a result, a pulse amplitude modulation signal, that is, an output signal, having an amplitude corresponding to the duty ratio of the input signal is generated. This output signal is amplified in voltage by the amplifier circuit 194 and supplied to the electrodes 126 of the liquid crystal cell 120 via each channel.

[0078] As described above, in the lighting device according to an embodiment of the present invention, the input signal in the pulse width modulation method input from the input device 104 is converted into an output signal in the pulse width modulation method, and the optical element 110 can be controlled using this output signal. Therefore, the lighting device can be connected to various devices without considering the communication method.

[0079] As embodiments of the present invention, the above-described embodiments can be appropriately combined and implemented within a range not conflicting with each other. In addition, the display device based on each embodiment, which is made by a person skilled in the art by appropriately adding, deleting, or designing changes to the components, or by adding, omitting, or changing conditions in the process, as long as it has the gist of the present invention, is also included in the scope of the present invention.

[0080] Even other effects different from the effects brought about by the methods of the above-described embodiments, for other effects that are made clear by the description of this specification or are easily predictable by a person skilled in the art, should naturally be regarded as the effects brought about by the present invention.

[0081] Explanation of reference numerals

[0082] 100: Lighting device; 102: Light source; 104: Input device; 106: Power supply; 108: Connector; 110: Optical element; 120: Liquid crystal cell; 120-1: First liquid crystal cell; 120-2: Second liquid crystal cell; 120-3: Third liquid crystal cell; 120-4: Fourth liquid crystal cell; 122: First substrate; 124: Second substrate; 126: Electrode; 126-1: First electrode; 126-2: Second electrode; 126-3: Third electrode; 126-4: Fourth electrode; 128: Alignment film; 128-1: First alignment film; 128-2: Second alignment film; 130: Liquid crystal layer; 132: Sealing material; 134: Adhesive; 140: Terminal; 142: Terminal; 144: Connection wiring; 146: Connection wiring; 150: Control device; 160: Signal generation circuit section; 162: Signal conversion section; 162-1: First signal conversion section; 162-2: Second signal conversion section; 164: Counting circuit; 166: Division circuit; 168: Processing circuit; 170: Filter circuit; 172: Correction circuit; 174: Voltage calculation circuit; 176: OR circuit; 178: First multiplexer; 180: Second multiplexer; 190: Voltage application section; 192: Digital-to-analog conversion circuit; 194: Amplification circuit.

Claims

1. A lighting device, comprising: a light source; an optical element configured to transmit light emitted from the light source and including at least two liquid crystal cells overlapping each other; and a control device for controlling the optical element; each of the at least two liquid crystal cells has: a plurality of first electrodes and a plurality of second electrodes alternately arranged in stripes; a liquid crystal layer on the plurality of first electrodes and the plurality of second electrodes; and a plurality of third electrodes and a plurality of fourth electrodes arranged on the liquid crystal layer, crossing the plurality of first electrodes and the plurality of second electrodes, and alternately arranged in stripes, the control device is configured to the control device is input with a first input signal and a second input signal in a pulse width modulation method specifying the diffusivity of the optical element for the diffusion of the light in the direction in which the plurality of first electrodes extend and the direction in which the plurality of third electrodes extend, convert the first input signal and the second input signal into a first output signal and a second output signal in a pulse amplitude method respectively according to the duty ratios of the first input signal and the second input signal and supply them to the optical element.

2. The lighting device according to claim 1, wherein, the at least two liquid crystal cells include a first liquid crystal cell, a second liquid crystal cell, a third liquid crystal cell, and a fourth liquid crystal cell arranged from the light source side, the direction in which the plurality of first electrodes of the first liquid crystal cell and the second liquid crystal cell extend crosses the direction in which the plurality of first electrodes of the third liquid crystal cell and the fourth liquid crystal cell extend.

3. The lighting device according to claim 1, wherein, the control device includes a signal conversion unit configured to calculate the duty ratios of the first input signal and the second input signal respectively.

4. The lighting device according to claim 3, wherein, the signal conversion unit respectively has for the first input signal and the second input signal: a counting circuit and a division circuit for calculating the duty ratio; a processing circuit for performing exception processing when the duty ratio is 0 or 1; a filtering circuit for filtering the duty ratio; and a correction circuit for determining the diffusivity according to the duty ratio after the filtering process with reference to a look-up table.

5. The lighting device according to claim 4, wherein, the processing circuit has an OR circuit, a first multiplexer, and a second multiplexer, two input terminals of the OR circuit are connected to the counting circuit, and an output terminal is connected to a selection control input terminal of the second multiplexer, two input terminals and a selection control input terminal of the first multiplexer are connected to the counting circuit, one input terminal of the second multiplexer is connected to the division circuit, and the other input terminal is connected to an output terminal of the first multiplexer.

6. The lighting device according to claim 1, wherein, the control device includes: An applied voltage calculation unit configured to calculate the amplitudes of the first output signal and the second output signal based on the diffusion degree for each of the first input signal and the second input signal; and A voltage application unit that applies a voltage to the optical element according to the amplitudes of the first output signal and the second output signal.

7. The lighting device according to claim 6, wherein the voltage application unit includes a plurality of digital-to-analog converters and a plurality of amplifiers respectively connected to the plurality of first electrodes, the plurality of second electrodes, the plurality of third electrodes, and the plurality of fourth electrodes of the at least two liquid crystal cells.

8. A driving method for a lighting device, the lighting device comprising: A light source; An optical element configured to transmit light emitted from the light source and including at least two liquid crystal cells overlapping each other; and A control device that controls the optical element; Each of the at least two liquid crystal cells has: A plurality of first electrodes and a plurality of second electrodes alternately arranged in a stripe shape; A liquid crystal layer on the plurality of first electrodes and the plurality of second electrodes; And A plurality of third electrodes and a plurality of fourth electrodes arranged on the liquid crystal layer, crossing the plurality of first electrodes and the plurality of second electrodes, and alternately arranged in a stripe shape, The driving method includes: Inputting a first input signal and a second input signal in a pulse width modulation method specifying the diffusion degree of the optical element for the light in the direction in which the plurality of first electrodes extend and the direction in which the plurality of third electrodes extend into the control device; And Converting the first input signal and the second input signal into a first output signal and a second output signal in a pulse amplitude method according to the duty ratio and supplying them to the optical element.

9. The driving method according to claim 8, wherein The at least two liquid crystal cells include a first liquid crystal cell, a second liquid crystal cell, a third liquid crystal cell, and a fourth liquid crystal cell arranged from the light source side, The direction in which the plurality of first electrodes of the first liquid crystal cell and the second liquid crystal cell extend crosses the direction in which the plurality of first electrodes of the third liquid crystal cell and the fourth liquid crystal cell extend.

10. The driving method according to claim 8, wherein The control device includes a signal conversion unit, The driving method includes calculating the duty ratio of each of the first input signal and the second input signal by the signal conversion unit.

11. The driving method according to claim 10, wherein The signal conversion unit includes a counting circuit, a division circuit, a processing circuit, a filtering circuit, and a correction circuit for the first input signal and the second input signal respectively, The driving method includes: Calculating the duty ratio by the counting circuit and the division circuit; Performing exception processing when the duty ratio is 0 or 1 by the processing circuit; Performing filtering processing on the duty ratio by the filtering circuit; and In the correction circuit, determining the diffusion degree according to the duty ratio after the filtering processing with reference to a look-up table.

12. The driving method according to claim 11, Among them, the processing circuit includes an OR circuit, a first multiplexer, and a second multiplexer. Two input terminals of the OR circuit are connected to the counting circuit, and an output terminal is connected to a selection control input terminal of the second multiplexer. Two input terminals and a selection control input terminal of the first multiplexer are connected to the counting circuit. One input terminal of the second multiplexer is connected to the division circuit, and another input terminal is connected to an output terminal of the first multiplexer.

13. The driving method according to claim 8, wherein, the control device includes an applied voltage calculation unit and a voltage application unit. The driving method includes: For each of the first input signal and the second input signal, through the applied voltage calculation unit, calculating the amplitudes of the first output signal and the second output signal based on the diffusion degree; and Through the voltage application unit, applying a voltage to the optical element according to the amplitudes of the first output signal and the second output signal.

14. The driving method according to claim 13, wherein, the voltage application unit includes a plurality of digital-to-analog converters and a plurality of amplifiers respectively connected to the plurality of first electrodes, the plurality of second electrodes, the plurality of third electrodes, and the plurality of fourth electrodes of the at least two liquid crystal cells.

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