Method for inspecting radio wave reflecton device

Abstract

This method for inspecting a radio wave reflection device is a method for inspecting a radio wave reflection device having a plurality of reflection elements arranged in a row direction and a column direction. The plurality of reflection elements each comprise a patch electrode, a common electrode overlapping the back surface side of the patch electrode, and a liquid crystal layer between a plurality of the patch electrodes and the common electrode, wherein: the radio wave reflection device constitutes a radio wave reflection plate that is irradiated with first light from a light source located above the radio wave reflection device via a first polarizing plate; an imaging device located above the ratio wave reflection device captures an image of the radio wave reflection plate via a second polarizing plate having a transmission axis orthogonal to the transmission axis of the first polarizing plate; and it is determined whether each reflection element is good or not on the basis of the presence or absence, within the image, of second light obtained by the first light being reflected by the radio wave reflection plate.

Description

Inspection method for radio wave reflecting devices

[0001] The present invention relates to a method for inspecting a radio wave reflecting device.

[0002] Radio wave reflecting devices are used to deliver radio waves to areas (dead zones) where radio waves are difficult to reach, such as the valleys between high-rise buildings. Examples of radio wave reflecting devices that have been disclosed include a configuration in which a main array element (dipole element), a subarray element (parasitic element), and a common electrode (ground electrode) are arranged with a dielectric substrate sandwiched between them, with the subarray element being disposed close to the main array element (Patent Document 1), and a configuration in which the array element and the common electrode (ground electrode) sandwich a dielectric substrate, with the common electrode having a periodic loop shape (Patent Document 2).

[0003] JP 2011-019021 A JP 2010-226695 A

[0004] A radio wave reflector uses a dielectric substrate. However, if the portion corresponding to this dielectric substrate is replaced with a liquid crystal layer, the dielectric anisotropy of the liquid crystal material can be utilized, making it possible to vary the directionality of the reflected waves. A radio wave reflector using a liquid crystal material has a configuration in which reflecting elements are arranged in a matrix, similar to a planar array antenna with a patch array. A radio wave reflector controls the direction of radio wave reflection by changing the dielectric constant of the liquid crystal layer that forms each reflecting element through the voltage applied between the electrodes. Therefore, to determine whether a radio wave reflector is good or bad, it is necessary to inspect the operation of each reflecting element. However, radio wave reflectors using liquid crystal have the problem of requiring a great deal of time to inspect each reflecting element individually, resulting in reduced productivity.

[0005] In view of such problems, one object of one embodiment of the present invention is to provide an inspection method that can determine the quality of a reflecting element of a radio wave reflecting device by observing the entire surface at once.

[0006] A method for inspecting a radio wave reflecting device according to one embodiment of the present invention is a method for inspecting a radio wave reflecting device having a plurality of reflecting elements arranged in row and column directions, each of the plurality of reflecting elements having a patch electrode, a common electrode overlapping the back side of the patch electrode, and a liquid crystal layer between the plurality of patch electrodes and the common electrode, which constitute a radio wave reflector. A light source located above the radio wave reflecting device irradiates a first light onto the radio wave reflecting device through a first polarizing plate, and an imaging device located above the radio wave reflecting device captures an image of the radio wave reflector through a second polarizing plate having a transmission axis perpendicular to the transmission axis of the first polarizing plate, and the quality of the reflecting elements is judged based on the presence or absence of a second light reflected by the radio wave reflector of the first light in the image.

[0007] A method for inspecting a radio wave reflecting device according to one embodiment of the present invention is a method for inspecting a radio wave reflecting device having a plurality of reflecting elements arranged in row and column directions, each of the plurality of reflecting elements having a patch electrode, a common electrode overlapping the back side of the patch electrode, and a liquid crystal layer between the plurality of patch electrodes and the common electrode, forming a radio wave reflector, a light source positioned above the radio wave reflecting device irradiates a first light onto the radio wave reflecting device through a third polarizing plate, an imaging device positioned above the radio wave reflecting device captures an image of the radio wave reflector 120 through the third polarizing plate, and the quality of the reflecting elements is judged based on the presence or absence of a third light reflected by the radio wave reflector 120 of the first light in the image.

[0008] 1 shows a plan view of a reflecting element used in a radio wave reflecting device according to one embodiment of the present invention. FIG. 1 shows a cross-sectional view of a reflecting element used in a radio wave reflecting device according to one embodiment of the present invention. FIG. 2 shows a state in which a reflecting element used in a radio wave reflecting device according to one embodiment of the present invention is operating, showing a state in which no voltage is applied between the patch electrode and the common electrode. FIG. 3 shows a state in which a reflecting element used in a radio wave reflecting device according to one embodiment of the present invention is operating, showing a state in which a voltage is applied between the patch electrode and the common electrode. FIG. 4 shows a configuration of a radio wave reflecting device according to one embodiment of the present invention. FIG. 5 shows a schematic diagram illustrating how the direction of travel of a reflected wave is changed by a radio wave reflecting device according to one embodiment of the present invention. FIG. 6 shows a configuration of a radio wave reflecting device according to one embodiment of the present invention. FIG. 7 shows a cross-sectional view of a reflecting element in a radio wave reflecting device according to one embodiment of the present invention. FIG. 8 shows a cross-sectional view of an inspection device used in inspecting a radio wave reflecting device according to one embodiment of the present invention. FIG. 9 shows a plan view for explaining a method for inspecting a radio wave reflecting device according to one embodiment of the present invention. FIG. 10 shows a plan view for explaining a method for inspecting a radio wave reflecting device according to one embodiment of the present invention. FIG. 11 shows a cross-sectional view for explaining a method for inspecting a radio wave reflecting device according to one embodiment of the present invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different forms, and should not be construed as being limited to the description of the following exemplary embodiments. For clarity of explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual form. However, these are merely examples and are not intended to limit the interpretation of the present invention. Furthermore, in this specification and each drawing, elements similar to those previously described with reference to the previous drawings are designated by the same reference numerals (or reference numerals with a, b, etc. suffixed thereto), and detailed descriptions may be omitted as appropriate. Furthermore, the letters "first" and "second" attached to each element are convenient labels used to distinguish each element and have no further meaning unless otherwise specified.

[0010] In this specification, when a component or region is referred to as being "on (or under)" another component or region, unless otherwise specified, this includes not only the case where it is directly above (or directly under) the other component or region, but also the case where it is above (or under) the other component or region, i.e., the case where another component is included between the component or region and above (or under) the other component or region.

[0011] 1A and 1B show a reflecting element 102 used in a radio wave reflecting device 100 according to one embodiment of the present invention. Fig. 1A shows a plan view of the reflecting element 102 as seen from above (the side where radio waves are incident), and Fig. 1B shows a cross-sectional view between A1 and A2 shown in the plan view.

[0012] 1A and 1B , the reflective element 102 includes a dielectric substrate 104, a counter substrate 106, a patch electrode 108, a common electrode 110, a first alignment film 112a, a second alignment film 112b, and a liquid crystal layer 114. Within the reflective element 102, the dielectric substrate 104 can be considered as a single layer, i.e., a dielectric layer. The patch electrode 108 is provided on the dielectric substrate 104, and the common electrode 110 is provided on the counter substrate 106. The common electrode 110 is disposed on the rear surface of the patch electrode 108. A first alignment film 112a is provided on the dielectric substrate 104 to cover the patch electrode 108, and a second alignment film 112b is provided on the counter substrate 106 to cover the common electrode 110. The patch electrode 108 and the common electrode 110 are disposed opposite each other, with a liquid crystal layer 114 disposed between them. A first alignment film 112 a is interposed between the patch electrode 108 and the liquid crystal layer 114 , and a second alignment film 112 b is interposed between the common electrode 110 and the liquid crystal layer 114 .

[0013] The patch electrode 108 preferably has a shape that is symmetrical with respect to the vertically and horizontally polarized waves of the incident radio wave, such as a square or circular shape in a plan view. However, this is merely a preferred example and is not limited to this shape. FIG. 1A shows a case where the patch electrode 108 is square in a plan view. The shape of the common electrode 110 is not particularly limited, and it has a shape that extends over substantially the entire surface of the opposing substrate 106 so as to have a larger area than the patch electrode 108. The material for forming the patch electrode 108 and the common electrode 110 is not limited, and they may be formed using conductive metals or metal oxides. A first wiring 118 may be provided on the dielectric substrate 104. The first wiring 118 is connected to the patch electrode 108. The first wiring 118 can be used to apply a control signal to the patch electrode 108. Furthermore, when multiple reflecting elements are arranged, the first wiring 118 can be used to connect a patch electrode to an adjacent patch electrode.

[0014] Although not shown in FIGS. 1A and 1B , the dielectric substrate 104 and the counter substrate 106 are bonded together with a sealant. The dielectric substrate 104 and the counter substrate 106 are disposed opposite each other with a gap therebetween, and the liquid crystal layer 114 is provided within the area surrounded by the sealant. The liquid crystal layer 114 is provided to fill the gap between the dielectric substrate 104 and the counter substrate 106. The gap between the dielectric substrate 104 and the counter substrate 106 is 20 to 100 μm, for example, 50 μm. A patch electrode 108, a common electrode 110, a first alignment film 112 a, and a second alignment film 112 b are provided between the dielectric substrate 104 and the counter substrate 106. Therefore, to be precise, the gap between the first alignment film 112 a and the second alignment film 112 b provided on the dielectric substrate 104 and the counter substrate 106, respectively, is the thickness of the liquid crystal layer 114. Although not shown in FIG. 1B, a spacer may be provided between the dielectric substrate 104 and the opposing substrate 106 to maintain a constant gap therebetween.

[0015] A control signal that controls the orientation of liquid crystal molecules in the liquid crystal layer 114 is applied to the patch electrode 108. The control signal is a DC voltage signal or a polarity inversion signal in which positive and negative DC voltages alternate. The common electrode 110 is grounded or receives a voltage at an intermediate level of the polarity inversion signal. Application of the control signal to the patch electrode 108 changes the orientation state of the liquid crystal molecules contained in the liquid crystal layer 114. A liquid crystal material having dielectric anisotropy is used for the liquid crystal layer 114. For example, nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, or discotic liquid crystal can be used for the liquid crystal layer 114. The dielectric constant of the liquid crystal layer 114 with dielectric anisotropy changes depending on the change in the orientation state of the liquid crystal molecules. The reflective element 102 can change the dielectric constant of the liquid crystal layer 114 by applying a control signal to the patch electrode 108, thereby delaying the phase of the reflected wave when reflecting radio waves.

[0016] The frequency bands of radio waves reflected by the reflective element 102 are the very high frequency (VHF) band, the ultra high frequency (UHF) band, the super high frequency (SHF) band, the submillimeter wave (THF) band, and the extra high frequency (EHF) band. The liquid crystal molecules in the liquid crystal layer 114 change their orientation in response to a control signal applied to the patch electrode 108, but the orientation hardly changes with the frequency of the radio waves irradiated onto the patch electrode 108. Therefore, the reflective element 102 can control the phase of the reflected radio waves without being affected by the radio waves themselves.

[0017] FIG. 2A shows a state (referred to as the "first state") in which no voltage is applied between the patch electrode 108 and the common electrode 110. FIG. 2A shows a case in which the first alignment film 112a and the second alignment film 112b are horizontal alignment films. In the first state, the long axes of the liquid crystal molecules 116 are aligned horizontally relative to the surfaces of the patch electrode 108 and the common electrode 110 by the first alignment film 112a and the second alignment film 112b. FIG. 2B shows a state (referred to as the "second state") in which a control signal (voltage signal) is applied to the patch electrode 108. In the second state, the liquid crystal molecules 116 are oriented with their long axes perpendicular to the surfaces of the patch electrode 108 and the common electrode 110 due to the action of an electric field. The angle at which the long axes of the liquid crystal molecules 116 are aligned can be set to a direction intermediate between the horizontal and vertical directions depending on the magnitude of the control signal applied to the patch electrode 108 (the magnitude of the voltage Vn between the common electrode and the patch electrode).

[0018] When the liquid crystal molecules 116 have positive dielectric anisotropy, the dielectric constant is higher in the second state than in the first state. Also, when the liquid crystal molecules 116 have negative dielectric anisotropy, if they are vertically aligned in advance, the apparent dielectric constant is higher in the second state than in the first state. When the liquid crystal molecules 116 are horizontally aligned, the apparent dielectric constant is already high, so that the orientation does not change significantly from the horizontal alignment even when an electric field is applied. The liquid crystal layer 114, which has dielectric anisotropy, can also be considered a variable dielectric layer. The reflective element 102 can control the phase delay (or non-delay) of the reflected wave by utilizing the dielectric anisotropy of the liquid crystal layer 114.

[0019] The reflecting element 102 is used as a radio wave reflector that reflects radio waves in a predetermined direction. It is preferable that the reflecting element 102 attenuates the amplitude of the reflected radio waves as little as possible. As is clear from the structure shown in Fig. 1B, when radio waves propagating through the air are reflected by the reflecting element 102, the radio waves pass through the dielectric substrate 104 twice. The dielectric substrate 104 is formed of a dielectric material such as glass or resin.

[0020] 2. Radio Wave Reflector Next, the structure of a radio wave reflector in which reflecting elements are integrated will be described.

[0021] 2-1. Radio Wave Reflecting Device A (Single-Axis Reflection Control) FIG. 3 shows the configuration of a radio wave reflecting device 100a according to one embodiment of the present invention. The radio wave reflecting device 100 has a radio wave reflecting plate 120. The radio wave reflecting plate 120 is composed of a plurality of reflecting elements 102. The plurality of reflecting elements 102 are arranged, for example, in a column direction (the X-axis direction shown in FIG. 3 ) and a column direction (the Y-axis direction shown in FIG. 3 ) intersecting the column direction. The reflecting elements 102 are arranged so that the patch electrodes 108 face the radio wave incident surface. The radio wave reflecting plate 120 is flat, and a plurality of patch electrodes 108 are arranged in a matrix within the surface of this flat plate.

[0022] The radio wave reflecting device 100a has a structure in which multiple reflecting elements 102 are integrated on a single dielectric substrate 104. As shown in FIG. 3 , the radio wave reflecting device 100 has a structure in which the dielectric substrate 104 on which multiple patch electrodes 108 are arranged and the counter substrate 106 on which a common electrode 110 is provided are stacked, with a liquid crystal layer (not shown) provided between the two substrates. The radio wave reflecting plate 120 is formed in the area where the multiple patch electrodes 108 and the common electrode 110 overlap. The cross-sectional structure of the radio wave reflecting plate 120, when viewed from the individual patch electrodes 108, is the same as the structure of the reflecting element 102 shown in FIG. 1B . The dielectric substrate 104 and the counter substrate 106 are bonded together with a sealant 128, and a liquid crystal layer (not shown) is provided in the area inside the sealant 128.

[0023] The dielectric substrate 104 has a region facing the opposing substrate 106, as well as a peripheral region 122 extending outward from the opposing substrate 106. A first drive circuit 124 and a terminal section 126 are provided in the peripheral region 122. The first drive circuit 124 outputs a control signal to the patch electrode 108. The terminal section 126 is a region for forming a connection with an external circuit, and is connected to, for example, a flexible printed circuit board (FPC) (not shown). A signal for controlling the first drive circuit 124 is input to the terminal section 126.

[0024] As described above, a plurality of patch electrodes 108 are arranged in the column direction (X-axis direction) and the column direction (Y-axis direction) on the dielectric substrate 104. Furthermore, a plurality of first wirings 118 extending in the column direction (Y-axis direction) are arranged on the dielectric substrate 104. Each of the plurality of first wirings 118 is electrically connected to a plurality of patch electrodes 108 arranged in the column direction (Y-axis direction). In other words, the plurality of patch electrodes 108 arranged in the column direction (Y-axis direction) are connected by the first wirings 118. The radio wave reflecting plate 120 has a configuration in which a plurality of patch electrode arrays connected by the first wirings 118 are arranged in a row in the column direction (X-axis direction).

[0025] The plurality of first wirings 118 arranged on the radio wave reflecting plate 120 extend into the peripheral region 122 and are connected to a first driving circuit 124. The first driving circuit 124 is capable of outputting control signals of different voltage levels to each of the plurality of first wirings 118. As a result, in the radio wave reflecting plate 120, a control signal is applied to each of the plurality of patch electrodes 108 arranged in the column direction (X-axis direction) and the column direction (Y-axis direction) for each column (each patch electrode 108 arranged in the column direction (Y-axis direction)).

[0026] The radio wave reflecting device 100a applies a control signal to each set of the plurality of patch electrodes 108 arranged in the column direction (Y-axis direction), thereby controlling the reflection direction of the reflected wave of the radio wave incident on the radio wave reflector 120. In other words, the radio wave reflecting device 100a can control the propagation direction of the reflected wave of the radio wave irradiated to the radio wave reflector 120 in the left and right directions in the drawing, centered on a reflection axis VR parallel to the column direction (Y-axis direction).

[0027] 4 shows a schematic diagram illustrating how the direction of propagation of a reflected wave changes depending on the two reflecting elements 102. When radio waves are incident on reflecting elements 102a and 102b with the same phase, different control signals (V1≠V2) are applied to reflecting elements 102a and 102b, resulting in a larger phase change in the reflected wave from reflecting element 102b than from reflecting element 102a. As a result, the phase of reflected wave R1 reflected from reflecting element 102a differs from the phase of reflected wave R2 reflected from reflecting element 102b (in FIG. 4, the phase of reflected wave R2 leads the phase of reflected wave R1), and the apparent direction of propagation of the reflected wave changes obliquely.

[0028] This principle can be applied to the radio wave reflecting device 100a shown in FIG. 3, and for example, by controlling the amount of phase change by the reflecting elements for each row, the reflection direction can be controlled in one axis direction.

[0029] 2-2. Radio wave reflecting device B (two-axis reflection control) The radio wave reflecting device 100a shown in Fig. 3 has a single reflection axis VR, so it is possible to control the reflection angle in the direction of the reflection axis VR as the axis of rotation. In contrast, this embodiment shows an example of a radio wave reflecting device 100b that can perform two-axis reflection control. The following explanation will focus on the differences from the radio wave reflecting device 100a.

[0030] The radio wave reflecting device 100b has a plurality of second wirings 132 extending in the row direction (X-axis direction). The plurality of first wirings 118 and the plurality of second wirings 132 are arranged to intersect with an insulating layer (not shown) sandwiched therebetween. The plurality of first wirings 118 are connected to a first drive circuit 124, and the plurality of second wirings 132 are connected to a second drive circuit 130. The second drive circuit 130 outputs a scanning signal.

[0031] 5B shows an enlarged view of an arrangement 102m of four patch electrodes 108 and two first wirings 118 and second wirings 132. Each of the four patch electrodes 108 is provided with a switching element 134. The switching (on and off) of the switching element 134 is controlled by a scanning signal applied to the second wiring 132. When the switching element 134 is turned on, the patch electrode 108 is electrically connected to the first wiring 118 and a control signal is applied to it. The switching element 134 is formed of, for example, a thin-film transistor. With this configuration, it is possible to select a plurality of patch electrodes 108 arranged in the row direction (X-axis direction) for each row and apply control signals of different voltage levels to each row.

[0032] 5A can control the direction of travel of the reflected wave in the left-right direction of the drawing, centered on a reflection axis VR parallel to the column direction (Y-axis direction), for radio waves irradiated onto the radio wave reflector 120. In addition, the radio wave reflecting device 100b can also control the direction of travel of the reflected wave in the up-down direction of the drawing, centered on a reflection axis HR parallel to the column direction (X-axis direction). In other words, because the radio wave reflecting device 100b has a reflection axis VR parallel to the column direction (Y-axis direction) and a reflection axis HR parallel to the column direction (X-axis direction), it can control the reflection angle in the direction about the reflection axis VR as the rotation axis and in the direction about the reflection axis HR as the rotation axis.

[0033] This principle can be applied to the radio wave reflecting device 100b shown in FIG. 5A. For example, by independently controlling the amount of phase change by the reflecting elements in both columns and rows, the reflection direction can be controlled in both uniaxial and biaxial directions.

[0034] 6 shows an example of the cross-sectional structure of a reflective element 102 in which a switching element 134 is connected to a patch electrode 108. The switching element 134 is provided on a dielectric substrate 104. The switching element 134 is a transistor and has a stacked structure of a first gate electrode 138, a first gate insulating layer 140, a semiconductor layer 142, a second gate insulating layer 146, and a second gate electrode 148. An undercoat layer 136 may be provided between the first gate electrode 138 and the dielectric substrate 104. A first wiring 118 is provided between the first gate insulating layer 140 and the second gate insulating layer 146. The first wiring 118 is provided so as to be in contact with the semiconductor layer 142. A first connection wiring 144 is provided in the same layer as the conductive layer that forms the first wiring 118. The first connection wiring 144 is provided so as to be in contact with the semiconductor layer 142. The connection structure of the first wiring 118 and the first connection wiring 144 to the semiconductor layer 142 shows a structure in which one wiring is connected to the source of the transistor and the other wiring is connected to the drain.

[0035] A first interlayer insulating layer 150 is provided to cover the switching element 134. A second wiring 132 is provided on the first interlayer insulating layer 150. The second wiring 132 is connected to the second gate electrode 148 through a contact hole formed in the first interlayer insulating layer 150. Although not shown, the first gate electrode 138 and the second gate electrode 148 are electrically connected to each other in a region that does not overlap with the semiconductor layer 142. A second connection wiring 152 is provided on the first interlayer insulating layer 150 and is made of the same conductive layer as the second wiring 132. The second connection wiring 152 is connected to the first connection wiring 144 through a contact hole formed in the first interlayer insulating layer 150.

[0036] A second interlayer insulating layer 154 is provided to cover the second wiring 132 and the second connection wiring 152. Furthermore, a planarizing layer 156 is provided to fill in the step of the switching element 134. By providing the planarizing layer 156, the patch electrode 108 can be formed without being affected by the arrangement of the switching element 134. A passivation layer 158 is provided on the flat surface of the planarizing layer 156. The patch electrode 108 is provided on the passivation layer 158. The patch electrode 108 is connected to the second connection wiring 152 via a contact hole that penetrates the passivation layer 158, the planarizing layer 156, and the second interlayer insulating layer 154. A first alignment film 112a is provided on the patch electrode 108.

[0037] The counter substrate 106 is provided with a common electrode 110 and a second alignment film 112b, as in FIG. 1B . The surface of the dielectric substrate 104 on which the switching element 134 and the patch electrode 108 are provided faces the surface of the counter substrate on which the common electrode 110 is provided, and a liquid crystal layer 114 is provided therebetween. The thickness T of the dielectric substrate 104 can be defined as the length from the surface of the patch electrode 108 on the liquid crystal layer 114 side to the surface of the dielectric substrate 104 opposite the surface on which the patch electrode 108 is provided. In this case, the thickness of at least one insulating layer (undercoat layer 136, first gate insulating layer 140, second gate insulating layer 146, first interlayer insulating layer 150, second interlayer insulating layer 154, planarizing layer 156, passivation layer 158) between the patch electrode 108 and the dielectric substrate 104 can be taken into consideration.

[0038] The layers formed on the dielectric substrate 104 are formed using the following materials. The undercoat layer 136 is formed, for example, of a silicon oxide film. The first gate insulating layer 140 and the second gate insulating layer 146 are formed, for example, of a silicon oxide film or a stacked structure of a silicon oxide film and a silicon nitride film. The semiconductor layer is formed of a silicon semiconductor such as amorphous silicon or polycrystalline silicon, or an oxide semiconductor including a metal oxide such as indium oxide, zinc oxide, or gallium oxide. The first gate electrode 138 and the second gate electrode 148 may be formed, for example, of molybdenum (Mo), tungsten (W), or an alloy thereof. The first wiring 118, the second wiring 132, the first connection wiring 144, and the second connection wiring 152 are formed using a metal material such as titanium (Ti), aluminum (Al), or molybdenum (Mo). For example, they may be formed as a stacked structure of titanium (Ti), aluminum (Al), and titanium (Ti), or a stacked structure of molybdenum (Mo), aluminum (Al), and molybdenum (Mo). The planarization layer 156 is made of a resin material such as acrylic or polyimide. The passivation layer 158 is made of, for example, a silicon nitride film. The patch electrode 108 and the common electrode 110 are made of a metal film such as aluminum (Al) or copper (Cu).

[0039] 6 , by connecting the second wiring 132 to the gate of a transistor used as a switching element 134, connecting the first wiring 118 to one of the source and drain of the transistor, and connecting the patch electrode 108 to the other of the source and drain, a control signal can be applied to a predetermined patch electrode selected from the plurality of patch electrodes 108 arranged in a matrix. By providing the switching element 134 to each patch electrode 108 in the radio wave reflector 120, a control voltage can be applied to each patch electrode 108 arranged in a horizontal row along the first direction (X-axis direction) or each patch electrode 108 arranged in a vertical row along the second direction (Y-axis direction). For example, when the radio wave reflector 120 is upright, the reflection direction of the reflected wave can be controlled in the left-right and up-down directions.

[0040] 3. Inspection Device Next, an inspection device 200 used to inspect the radio wave reflecting device 100 will be described with reference to FIGS.

[0041] The inspection device 200 basically comprises a light source 202, an imaging device 204, a sample stage 206, and a polarizing plate 208. Fig. 7 is a cross-sectional view of an inspection device used to inspect a radio wave reflecting device according to one embodiment of the present invention.

[0042] The light source 202 has an irradiation area capable of irradiating the entire surface of the radio wave reflecting device 100 (the entire surface of the radio wave reflecting plate 120) with, for example, white light. The light source 202 is disposed diagonally above the sample stage 206. The imaging device 204 is disposed so that the light emitted from the light source 202 does not directly enter the imaging device 204. The light source 202 is disposed so that, when the radio wave reflecting device 100 is placed on the sample stage 206, the light emitted from the light source 202 irradiates the entire radio wave reflecting plate 120 of the radio wave reflecting device 100. As will be described in detail later, the radio wave reflecting device 100 is placed on the sample stage 206 so that the light emitted from the light source 202 is incident on the radio wave reflecting plate 120 on which the patch electrodes 108 are arranged. Because the patch electrodes 108 are made of metal, the light source 202 is disposed diagonally above the sample stage 206 so that the light source 202 is not reflected in the radio wave reflecting plate 120 when the radio wave reflecting device 100 is placed on the sample stage 206. The light source 202 may be, for example, a surface-illuminating light source in which light from a halogen lamp is guided by a light guide, or a surface light source using a white LED or a fluorescent lamp.

[0043] The imaging device 204 captures an image of the light LY emitted from the light source 202 through the polarizing plate 208 and reflected by the radio wave reflecting plate 120, via the polarizing plate 208. The imaging device 204 is located above the sample stage 206, at a position where the light reflected by the radio wave reflecting plate 120 is incident. When the radio wave reflecting device 100 is installed on the sample stage 206, the imaging device 204 has a viewing angle that allows it to capture the entire surface of the radio wave reflecting plate 120 as a single image. The imaging device 204 can be, for example, a camera such as a digital camera or a video camera. By using the imaging device 204 to capture the entire surface of the radio wave reflecting plate 120 on which the patch electrodes 108 are arranged as a single image, the time required to observe the entire radio wave reflecting device 100 can be shortened.

[0044] Although the imaging device 204 has been mentioned above, the image of the light LY emitted from the light source 202 through the polarizing plate 208 and reflected by the radio wave reflector 120 may be actually confirmed visually.

[0045] The sample stage 206 has a flat surface so as to be able to stably hold the radio wave reflecting device 100. The sample stage 206 may be provided with a fixing member for fixing the radio wave reflecting device 100, a vacuum chuck, or the like.

[0046] The polarizing plate 208 is a linear polarizing plate that transmits light polarized in one direction out of the light emitted from the light source 202. Therefore, linearly polarized light is illuminated onto the radio wave reflecting device 100. The polarizing plates 208 are arranged on the light source 202 side and the imaging device 204 side. Specifically, as shown in FIG. 7, the polarizing plate 208-1 is arranged between the radio wave reflecting device 100 and the light source 202, and the polarizing plate 208-2 is arranged between the radio wave reflecting device 100 and the imaging device 204. The polarizing plates 208-1 and 208-2 are arranged so that their transmission axes are perpendicular to each other (crossed Nicols). As shown in FIG. 7, the transmission axis TA1 of the polarizing plate 208-1 and the transmission axis TA2 of the polarizing plate 208-2 are perpendicular to each other. The direction in which the liquid crystal molecules 116 of the radio wave reflecting device 100 are aligned in the first state shown in FIG. 2A is parallel or perpendicular to the polarization direction of the light emitted through the polarizing plate 208-1. The polarizing plate 208-1 and the polarizing plate 208-2 are not arranged to face each other, but are arranged to face the radio wave reflecting device 100 or the sample stage 206, respectively.

[0047] With this combination of two polarizing plates, light (linearly polarized component LX) emitted from the light source 202 through the polarizing plate 208-1 is reflected by the radio wave reflecting device 100, and the light (linearly polarized component LY) whose polarization direction is rotated by 90° passes through the polarizing plate 208-2 and enters the imaging device 204. That is, the imaging device 204 does not directly receive the light emitted from the light source 202 to capture an image, but rather receives the linearly polarized component LY whose polarization state has not been maintained by the liquid crystal layer 114. Whether the liquid crystal layer 114 maintains the polarization state of the linearly polarized component LX depends on the bias state between the patch electrode 108 and the common electrode 110. The inspection device 200 of this embodiment utilizes these characteristics of the liquid crystal layer 114 to inspect the quality (whether the reflecting element 102 forming the radio wave reflector 120 is a good product that operates normally or a defective product that does not operate).

[0048] 7 shows an example in which the inspection device 200 is configured with two linear polarizing plates, but the configuration of the polarizing plates is not limited to this example. When a polarizing plate combining a linear polarizing plate and a quarter-wave plate, such as a circular polarizing plate, is used as the polarizing plate 208, the inspection device 200 can be configured with a single polarizing plate. For example, as shown in FIG. 8 , when a circular polarizing plate is used, it is sufficient to arrange a polarizing plate 208C (circular polarizing plate) between the light source 202 and the imaging device 204, without arranging the polarizing plates 208 between the light source 202 and the imaging device 204.

[0049] The polarizing plate 208C polarizes the light LV emitted from the light source 202, removes the polarized light specularly reflected by the radio wave reflecting device 100, and transmits the other light (light LW). The polarizing plate 208C is preferably large enough to cover the radio wave reflecting device 100 or the radio wave reflector 120.

[0050] 4. Inspection Method Next, the inspection method for the radio wave reflecting device 100 will be described with reference to FIG.

[0051] First, the radio wave reflecting device 100 is placed on the inspection device 200 so that it can be observed from above, with the direction from which the patch electrode 108 can be observed being the upper surface. For example, as shown in Fig. 7 , the radio wave reflecting device 100 is placed on a sample stage 206 of the inspection device so that the patch electrode 108 of the reflecting element 102 is on the light source 202 and imaging device 204 side, and the common electrode 110 is on the sample stage 206 side.

[0052] Next, voltages V0 to V2 are applied between the patch electrode 108 and the common electrode 110, and light is irradiated from the light source 202 to the radio wave reflecting device 100 via the polarizing plate 208-1. In this embodiment, voltage V0 indicates that the voltage between the patch electrode 108 and the common electrode 110 is 0 V, and the application of 0 V is also included in the application of voltages. Voltages V0 to V2 are different from one another. Furthermore, the absolute values ​​of voltages V0 to V2 are larger in the order of voltage V0, voltage V1, and voltage V2. These applied voltages are not limited to voltages V0 to V2, and can be set appropriately within a range in which the reflecting element 102 can be set from a low phase difference to a high phase difference.

[0053] The order of applying a voltage between the patch electrode 108 and the common electrode 110 and irradiating light onto the radio wave reflecting device 100 does not need to be as described above. For example, the radio wave reflecting device 100 may be irradiated with light before applying a voltage between the patch electrode 108 and the common electrode 110.

[0054] Furthermore, when each voltage is applied, an image is taken using the imaging device 204 so that the entire surface of the radio wave reflector 120 fits into one image. At this time, the radio wave reflector 120 is photographed through the polarizing plate 208-2.

[0055] Finally, the quality of the reflective element 102 is determined based on the presence or absence of light (linearly polarized component LY) reflected by the reflective element 102 from the light (linearly polarized component LX) in the image captured by the imaging device 204, and the brightness or amount of light of the light (linearly polarized component LY). The presence or absence and brightness or amount of light of the light (linearly polarized component LY) will be described later.

[0056] 9A to 9C, a description will be given of the reflective element 102 in which a desired voltage corresponding to the voltage applied between the patch electrode 108 and the common electrode 110 is applied to the liquid crystal layer. Figures 9A to 9C show plan views of a reflective element used in a radio wave reflecting device according to one embodiment of the present invention.

[0057] A voltage V0 is applied between the patch electrode 108 and the common electrode 110, or no voltage is applied between the patch electrode 108 and the common electrode 110 of the reflecting element 102. When the reflecting element 102 is observed from above at this time, the frame-shaped region 160 does not appear on the outer periphery of the patch electrode 108, as in the reflecting elements 102a and 102b shown in FIG.

[0058] A voltage V1 is applied between the patch electrode 108 and the common electrode 110. When the reflecting element 102 is observed from above at this time, a frame-shaped region 160 appears on the outer periphery of the patch electrode 108, as shown in Fig. 9B. The frame-shaped region 160 surrounds the patch electrode 108 in the top view.

[0059] A voltage V2 is applied between the patch electrode 108 and the common electrode 110. At this time, when the reflective element 102 is observed from above, a frame-shaped region 160 appears around the patch electrode 108, as shown in FIG. 9C . The width of the frame-shaped region 160 shown in FIG. 9C is larger than the width of the frame-shaped region 160 shown in FIG. 9B , similar to the relationship in which the absolute value of the voltage V2 is larger than the absolute value of the voltage V1. Furthermore, because the absolute value of the voltage V2 is larger than the absolute value of the voltage V1, the reflective element 102 can be set with a phase change amount that is larger than the phase change amount that is set in the reflective element 102 when the voltage V1 is applied between the patch electrode 108 and the common electrode 110.

[0060] Next, referring to Fig. 10, a description will be given of light that is irradiated from the light source 202 to the reflecting element 102 via the polarizing plate 208-1 and reflected by the reflecting element 102. Fig. 10 shows a cross-sectional view of a reflecting element in a radio wave reflecting device according to one embodiment of the present invention.

[0061] Of the light emitted from the light source 202, linearly polarized light component LX0 passes through the polarizing plate 208-1, and the light LX0 is irradiated onto the reflecting element 102. The irradiated linearly polarized light component LX0 is specularly reflected by the patch electrode 108. The light reflected by the patch electrode 108 maintains the polarization of the light LX0 and is the linearly polarized light component LX1.

[0062] The linearly polarized light component LX0 is irradiated not only onto the patch electrode 108 but also onto the common electrode 110, where it is specularly reflected. At this time, the linearly polarized light component LX0 passes between adjacent patch electrodes 108 in a top view and is reflected onto the common electrode 110. For example, as shown in FIG. 10 , the linearly polarized light component LX0 passes through the liquid crystal layer 114 from between the patch electrode 108 of the adjacent reflective element 102a and the patch electrode 108 of the reflective element 102b, and is reflected onto the common electrode 110. In the reflective element 102 shown in FIG. 9A , a voltage V0 is applied between the patch electrode 108 and the common electrode 110 (a state in which no voltage is applied), and therefore the light reflected onto the common electrode 110 maintains the polarization of the light LX0 and is the linearly polarized light component LX2.

[0063] As described above, because polarizing plate 208-2 is disposed in a crossed Nicol configuration with polarizing plate 208-1, the light of linearly polarized component LX1 and linearly polarized component LX2 is blocked by polarizing plate 208-2 and does not reach image capturing device 204. Since the light of linearly polarized components LX1 and LX2 does not reach image capturing device 204, they are not detected by image capturing device 204 and do not appear in images of the multiple reflective elements 102.

[0064] Therefore, when a voltage V0 is applied between each patch electrode 108 and common electrode 110 in the radio wave reflector 120, if there is no light reflected by the reflective element 102 in the image of the radio wave reflector 120, it can be determined that voltage is being applied normally to the liquid crystal layer 114.

[0065] Next, with reference to Fig. 11, a description will be given of light that is emitted from light source 202 via polarizing plate 208-1 to reflecting element 102 and reflected by reflecting element 102. Fig. 11 shows a cross-sectional view of reflecting element 102 shown in Fig. 9B.

[0066] 11 , the frame-shaped region 160 is the upper surface of a portion of the liquid crystal layer 114. The portion of the liquid crystal layer 114 having the frame-shaped region 160 as its upper surface is liquid crystal oriented by an oblique electric field (up and down arrows) formed between the patch electrode 108 and the common electrode 110 when a voltage V1 is applied between the patch electrode 108 and the common electrode 110. The oblique electric field indicated by the up and down arrows is an example and is not limiting.

[0067] More specifically, the portion of the liquid crystal layer 114 having the frame-shaped region 160 as its upper surface exhibits liquid crystal orientation due to leakage of an oblique electric field formed between the end of the patch electrode 108 or its periphery and the common electrode 110. As shown in FIG. 11 , the leakage of an oblique electric field refers to an electric field formed outside the width 108w of the patch electrode 108 between the patch electrode 108 and the common electrode 110, in contrast to the electric field within the width 108w of the patch electrode 108. Therefore, as shown in FIG. 9B , the liquid crystal orientation due to these electric fields can be seen from above as a frame-shaped region 160 that appears on the outer periphery of the patch electrode 108, and changes depending on the voltage applied between the patch electrode 108 and the common electrode 110.

[0068] Also, as shown in Figure 9B, a portion of the liquid crystal layer that is oriented by an electric field formed outside the width 108w is positioned between the patch electrode 108 and the common electrode 110 so as to sandwich the liquid crystal layer 114 that is oriented by an electric field within the width 108w of the patch electrode 108.

[0069] As described above, the linearly polarized light component LX0 emitted from the light source 202 through the polarizing plate 208-1 is reflected by the patch electrode 108 and the common electrode 110. As described above, the light reflected by the patch electrode 108 is the linearly polarized light component LX1 in which the polarization of the light LX0 is maintained, and the light reflected by the common electrode 110 includes the linearly polarized light component LX2 in which the polarization of the linearly polarized light component LX0 is maintained, and the light LY2 in which the polarization is not maintained.

[0070] The light LY2 passes through a portion of the liquid crystal layer 114 in which the linearly polarized component LX0 is oriented and is reflected by the common electrode 110, or is reflected by the common electrode 110 and passes through a portion of the liquid crystal layer 114 in which the linearly polarized component LX0 is oriented, thereby resulting in a state in which the polarization of the linearly polarized component LX0 is not maintained. A state in which the polarization of the linearly polarized component LX0 is not maintained is, for example, when the light LY2 passes through a portion of the liquid crystal layer 114 in which the linearly polarized component LX0 is oriented and becomes scattered light that is elliptically polarized or unpolarized.

[0071] As described above, the light LY2 is not in a state where the polarization of the linearly polarized light component LX0 is not maintained, and so is not blocked by the polarizing plate 208-2 and can reach the imaging device 204. The light LY2 is detected by the imaging device 204 and appears in an image of the radio wave reflector 120. The light LY2 that appears in the image of the radio wave reflector 120 can appear as light surrounding the patch electrode 108 in a top view, as will be described in detail later.

[0072] Therefore, when a voltage V1 is applied between each patch electrode 108 and the common electrode 110 in the radio wave reflector 120, and the linearly polarized light component LX2 is reflected with uniform brightness or light intensity on the image of the radio wave reflector 120, it can be determined that a voltage is being applied normally to the liquid crystal layer 114.

[0073] Next, with reference to Figure 12, the cross-sectional structure of the reflective element 102 shown in Figure 9C when irradiated with light from the light source 202 via the polarizing plate 208-1 will be described. Figure 12 shows a cross-sectional view of the reflective element 102 shown in Figure 9C. The reflective element 102 differs from the reflective element 102 shown in Figure 11 in that the absolute value of the voltage applied between the patch electrode 108 and the common electrode 110 is greater than the absolute value of the voltage V1. Note that descriptions of configurations that are the same as or similar to the reflective element 102 shown in Figure 11 may be omitted.

[0074] 12 , the frame-shaped region 160 is the upper surface of a portion of the liquid crystal layer 114. The portion of the liquid crystal layer 114 having the frame-shaped region 160 as its upper surface is liquid crystal oriented by an oblique electric field (up and down arrows) formed between the patch electrode 108 and the common electrode 110 when a voltage V2 is applied between the patch electrode 108 and the common electrode 110. The oblique electric field indicated by the up and down arrows is an example and is not limiting.

[0075] The electric field formed when voltage V2 is applied between patch electrode 108 and common electrode 110 is stronger than when voltage V1 is applied between patch electrode 108 and common electrode 110, and as shown in Figures 9B and 9C, the width of the frame-shaped region 160 that appears on the outer periphery of patch electrode 108 becomes larger, and the electric field also becomes larger in Figures 11 and 12.

[0076] As described above, the linearly polarized light component LX0 emitted from the light source 202 through the polarizing plate 208-1 is reflected by the patch electrode 108 and the common electrode 110. As described above, the linearly polarized light component LX1 reflected by the patch electrode 108 is in a state in which the polarization of the linearly polarized light component LX0 is maintained, and the light reflected by the common electrode 110 includes the linearly polarized light component LX2 in a state in which the polarization of the linearly polarized light component LX0 is maintained, and the light LY3 in a state in which the polarization is not maintained.

[0077] The light LY3 passes through a portion of the liquid crystal layer 114 where the light LX0 is aligned and is reflected by the common electrode 110, or passes through a portion of the liquid crystal layer 114 where the light LX0 is aligned and is reflected by the common electrode 110, and thereby the polarization of the linearly polarized component LX0 is not maintained. Because the width of the frame region 160 is larger than when the voltage V1 is applied between the patch electrode 108 and the common electrode 110, the amount of linearly polarized component LX0 that passes through the frame region 160 increases, and the amount of light in a state where the polarization of the linearly polarized component LX0 is not maintained increases compared to the light LY2.

[0078] As described above, the polarization of the linearly polarized light component LX0 is not maintained for the light LY3, and so the light LY3 is not blocked by the polarizing plate 208-2 and can reach the imaging device 204. The light LY3 is detected by the imaging device 204 and appears in the image of the radio wave reflector 120. Like the light LY2 described above, the light LY3 appearing in the image of the radio wave reflector 120 can appear as light surrounding the patch electrode 108 in a top view. However, the brightness or light amount of the light LY3 appearing in the image of the radio wave reflector 120 differs from the brightness and light amount of the light LY2 appearing in the image of the radio wave reflector 120. For example, when the absolute value of the voltage V2 is greater than the absolute value of the voltage V1, the brightness of the light LY3 in the image of the radio wave reflector 120 is brighter than the brightness of the light LY2.

[0079] Therefore, when voltage V2 is applied between each patch electrode 108 and common electrode 110 in radio wave reflector 120, light LX3 appears with uniform brightness or light intensity in an image of a plurality of reflective elements 102 that have normally operating reflective elements 102. The light intensity of light LX3 is greater than the light intensity of light LX2, and light LX3 appears brighter than light LX2 in the image of the plurality of reflective elements 102, and it can be determined that voltage is normally applied to liquid crystal layer 114.

[0080] The voltage applied between the patch electrode 108 and the common electrode 110 is not limited to the voltages V0 to V2 as described above, but may be, for example, a voltage greater than the absolute value of voltage V0 and less than the absolute value of voltage V1, or a voltage greater than the absolute value of voltage V1 and less than the absolute value of voltage V2.

[0081] Different voltages may be applied between the patch electrode 108 and the common electrode 110 of adjacent reflective elements 102. For example, a voltage V1 may be applied between the patch electrode 108 and the common electrode 110 of the reflective element 102a shown in Fig. 10 , and a voltage V2 may be applied between the patch electrode 108 and the common electrode 110 of the reflective element 102b. At this time, if the imaging device detects the linearly polarized light component LX3 around the patch electrode 108 of the reflective element 102b and the linearly polarized light component LX2 around the patch electrode 108 of the reflective element 102a, and if the linearly polarized light components LX2 and LX3 appear in the image of the radio wave reflector 120, it can be determined that a voltage is normally applied to the liquid crystal layer 114 of each reflective element 102.

[0082] A different voltage may be applied between the patch electrode 108 and the common electrode 110 between the reflective elements 102 in each column. For example, in the plurality of reflective elements 102 arranged in the column direction shown in FIG. 3 , a voltage V1 may be applied between the patch electrode 108 connected to the first wiring 118a and the common electrode 110, and a voltage V2 may be applied between the patch electrode 108 connected to the first wiring 118b and the common electrode 110. At this time, if the imaging device 204 detects light with uniform brightness around the patch electrode 108 connected to the first wiring 118a, detects light with uniform brightness around the patch electrode 108 connected to the first wiring 118b that is brighter than the light around the patch electrode 108 connected to the first wiring 118a, and captures the linearly polarized light component LX2 and the linearly polarized light component LX3 in the image of the radio wave reflector 120, it can be determined that a voltage is normally applied to the liquid crystal layer 114 of each reflective element 102.

[0083] As described above, the inspection method for the radio wave reflecting device 100 according to one embodiment of the present invention applies a desired voltage between the patch electrode 108 and the common electrode 110 of each of the multiple reflecting elements 102 of the radio wave reflecting device 100, irradiates the radio wave reflecting device 100 with light of linear polarization component LX0 from the light source 202 via the polarizing plate 208-1, and the imaging device 204 captures an image of the radio wave reflecting plate 120 via the polarizing plate 208-2. In the image, the quality of each reflecting element 102 can be determined based on the presence or absence of light reflected by the common electrode 110, or the brightness and amount of light corresponding to the above-mentioned voltage. This quality determination can be performed by observing the entire surface of the radio wave reflecting plate 120 of the radio wave reflecting device 100 at once, thereby shortening the time required to determine the quality of the reflecting element.

[0084] 5. Failure Modes 5-1. Images FIGS. 13 and 14 illustrate images of the plurality of reflective elements 102 when the desired voltage is not applied to the liquid crystal layer 114. FIG.

[0085] A voltage V0 was applied between all patch electrodes 108 and the common electrode 110 of the radio wave reflector 120, and some of the reflecting elements 102 did not operate normally. In Fig. 13, when a voltage V0 was applied between the patch electrodes 108 and the common electrode 110, an abnormal voltage was applied to two rows of multiple reflecting elements 102. Around the patch electrodes 108 of the reflecting elements 102 to which the abnormal voltage was applied, light LY was detected in a state in which the polarization state of the linearly polarized component LX0 reflected by the common electrode 110 was not maintained, and the light LY was reflected in the image.

[0086] In the case of the above-described failure mode, it is assumed that, for example, the first wiring 118 common to the column direction is short-circuited with a wiring, such as the second wiring 132, to which a different potential than that of the first wiring 118 is input.

[0087] 14, when a voltage V0 is applied between the patch electrode 108 and the common electrode 110, an abnormal voltage is applied between the patch electrode 108 and the common electrode 110 of a plurality of reflective elements 102 that are not arranged in a row. Around the patch electrode 108 to which the abnormal voltage is applied, abnormal light LY is detected that is reflected by the common electrode 110 in a state in which the polarization state of the linearly polarized light component LX0 is not maintained, and the light LY is reflected in the image.

[0088] In the case of the above-described failure mode, it is assumed that the switching element 134 to which the patch electrode 108 surrounded by the light LY is electrically connected is defective. Furthermore, in the case of the above-described failure mode, it is assumed that the patch electrode 108 is short-circuited to the second wiring 132 because a voltage is applied between the patch electrode 108 and the common electrode 110 even though the voltage V0 is applied between the patch electrode 108 and the common electrode 110.

[0089] 5-2. Brightness and Light Amount Voltages V0 to V4 are applied between the patch electrode 108 and the common electrode 110, and images of the multiple reflective elements 102 are captured. The absolute values ​​of voltages V0 to V4 are assumed to be such that voltage V0 is the smallest and voltage V4 is the largest. In the images captured at each voltage, the light LY detected around the patch electrode 108 is checked to see if the brightness or light amount of the light LY corresponds to the voltage applied between the patch electrode 108 and the common electrode 110. If the brightness or light amount of the light LY does not correspond to the voltage applied between the patch electrode 108 and the common electrode 110, the following failure modes A to D are assumed.

[0090] An example of the reflective element 102 in failure mode A will be described. When voltages V0 to V4 are applied between the patch electrode 108 and the common electrode 110, light LY detected around the patch electrode 108 is detected with a brightness or amount of light corresponding to the applied voltage from voltage V0 to voltage V2, but is not detected at high potentials from voltage V3 to voltage V4. In failure mode A, it is assumed that there is a defect in the electrical characteristics of the switching element 134 connected to the patch electrode 108.

[0091] An example of a reflective element 102 in failure mode B will be described. When light LY is applied between the patch electrode 108 and the common electrode 110 at voltages V0 to V4, it is not detected at voltages V0 to V2, but is detected at high voltages V3 to V4 with brightness or light intensity corresponding to the applied voltage. This indicates that in failure mode B, the voltage applied to the liquid crystal layer is insufficient. The cause of the insufficient voltage is presumed to be a defect in the electrical characteristics of the switching element 134 connected to the patch electrode 108. Furthermore, if the light intensity is lower than the light LY around the patch electrode 108 of a reflective element 102 that is operating normally, it is presumed that the voltage applied to the liquid crystal layer is insufficient, and that the electrical characteristics of the switching element connected to the patch electrode 108 are defective.

[0092] An example of the reflective element 102 in failure mode C will be described. The light LY is applied between the patch electrode 108 and the common electrode 110 at voltages V0 to V4, but no change is observed. Specifically, the light LY is not detected regardless of the applied voltage. Therefore, in failure mode C, an open defect in the switching element connected to the patch electrode 108, a connection defect between the patch electrode 108 and the switching element, etc. are expected.

[0093] An example of a reflective element 102 in failure mode D will be described. Light LY is applied between the patch electrode 108 and the common electrode 110 at voltages V0 to V4, but no change is observed. Specifically, light LY is detected regardless of the applied voltage. Therefore, in failure mode D, a short circuit between the source and drain of the switching element or a short circuit between the drain and gate is considered, and it is assumed that a voltage from the signal line connected to the source or the gate line connected to the gate electrode is always applied directly to the liquid crystal layer, causing light LY to be detected regardless of whether the switching element is on or off.

[0094] As described above, by observing the presence or absence of light LY or the change in brightness and light quantity depending on the applied voltage, reflective elements 102 in which the desired voltage is not applied to the liquid crystal layer can be classified as defective.

[0095] The above-described embodiments of the present invention may be combined as appropriate as long as they are not mutually inconsistent. Furthermore, even if a person skilled in the art appropriately adds or deletes components or modifies designs, or adds or omits processes or modifies conditions based on the embodiments, such combinations are included within the scope of the present invention as long as they include the gist of the present invention.

[0096] Even if there are other effects and advantages different from those brought about by the aspects of each of the above-mentioned embodiments, those that are clear from the description in this specification or that can be easily predicted by a person skilled in the art are naturally understood to be brought about by the present invention.

[0097] 100: radio wave reflecting device, 100a: radio wave reflecting device, 100b: radio wave reflecting device, 102: reflecting element, 102a: reflecting element, 102b: reflecting element, 102m: arrangement, 104: dielectric substrate, 106: opposing substrate, 108: patch electrode, 108w: width, 110: common electrode, 112a: first alignment film, 112b: second alignment film, 114: liquid crystal layer, 116: liquid crystal molecules, 118: first wiring, 118a: first wiring, 118b: first wiring, 120: radio wave reflecting plate, 122: peripheral area, 124: first driving circuit, 126: terminal portion, 128: sealing material, 130: second driving circuit 132: second wiring, 134: switching element, 136: undercoat layer, 138: first gate electrode, 140: first gate insulating layer, 142: semiconductor layer, 144: first connection wiring, 146: second gate insulating layer, 148: second gate electrode, 150: first interlayer insulating layer, 152: second connection wiring, 154: second interlayer insulating layer, 156: planarization layer, 158: passivation layer, 160: frame-shaped region, 200: inspection device, 202: light source, 204: imaging device, 206: sample stage, 208: polarizing plate, 208-1: polarizing plate, 208-2: polarizing plate, 208C: polarizing plate

Claims

1. A method for inspecting a radio wave reflecting device having a plurality of reflecting elements arranged in row and column directions, each of the plurality of reflecting elements having a patch electrode, a common electrode overlapping the rear side of the patch electrode, and a liquid crystal layer between the plurality of patch electrodes and the common electrode, forming a radio wave reflecting plate, the method comprising: irradiating the radio wave reflecting device with a first light from a light source located above the radio wave reflecting device through a first polarizing plate; an imaging device located above the radio wave reflecting device taking an image of the radio wave reflecting plate through a second polarizing plate having a transmission axis perpendicular to the transmission axis of the first polarizing plate; and judging the quality of the reflecting elements based on the presence or absence of a second light reflected by the radio wave reflecting plate of the first light in the image.

2. A method for inspecting a radio wave reflecting device as described in claim 1, further comprising the steps of: applying a voltage V0 between each of said plurality of patch electrodes and said common electrode; and said voltage V0 being a state in which no voltage is applied between said plurality of patch electrodes and said common electrode.

3. A method for inspecting a radio wave reflecting device as described in claim 2, further comprising: applying a voltage V1, different from the voltage V0, between each of the plurality of patch electrodes and the common electrode; and determining whether the reflecting element is good or bad based on the brightness of the second light in the image.

4. A method for inspecting a radio wave reflecting device as described in claim 3, further comprising the steps of: applying a voltage V2 having a potential greater than voltage V1 to each of the plurality of patch electrodes; and determining whether or not the reflecting element is good based on the brightness of the second light in the image.

5. The method for inspecting a radio wave reflecting device according to claim 1, wherein the imaging device is positioned so as to capture the entire surface of the radio wave reflecting plate in a single image.

6. The method for inspecting a radio wave reflecting device according to claim 1, wherein the light source is a surface light source.

7. A method for inspecting a radio wave reflecting device having a plurality of reflecting elements arranged in row and column directions, each of the plurality of reflecting elements having a patch electrode, a common electrode overlapping the rear side of the patch electrode, and a liquid crystal layer between the plurality of patch electrodes and the common electrode, forming a radio wave reflecting plate, the method comprising: irradiating the radio wave reflecting device with a first light from a light source located above the radio wave reflecting device through a third polarizing plate; an imaging device located above the radio wave reflecting device taking an image of the radio wave reflecting plate through the third polarizing plate; and judging the quality of the reflecting elements based on the presence or absence of a third light reflected by the radio wave reflecting plate of the first light in the image.

8. A method for inspecting a radio wave reflecting device as described in claim 7, further comprising the steps of: applying a voltage V0 between each of said plurality of patch electrodes and said common electrode; and said voltage V0 being a state in which no voltage is applied between said plurality of patch electrodes and said common electrode.

9. A method for inspecting a radio wave reflecting device as described in claim 8, further comprising the steps of: applying a voltage V1, which is different from the voltage V0, between each of the plurality of patch electrodes and the common electrode; and determining whether the reflecting element is good or bad based on the brightness of the third light in the image.

10. A method for inspecting a radio wave reflecting device according to claim 9, further comprising the steps of: applying a voltage V2 having a potential greater than voltage V1 to each of said plurality of patch electrodes; and determining whether said reflecting element is good or bad based on the brightness of said third light in said image.

11. The method for inspecting a radio wave reflecting device according to claim 7, wherein the third polarizing plate is disposed between the radio wave reflecting device and the light source and the imaging device.

12. The method for inspecting a radio wave reflecting device according to claim 7, wherein the imaging device is positioned so as to capture an image of the entire surface of the radio wave reflecting plate in a single image.

13. The method for inspecting a radio wave reflecting device according to claim 7, wherein the light source is a surface light source.