Abstract: A lens includes a lens body, and an electro-active section (liquid crystals and a diffraction section) that is provided to a region of part of the lens body. The lens includes a pair of electrodes that are embedded in the lens body, that are electrically connected to a focal length modification section, that extend downward from an upper side end of the lens body, and that are disposed substantially parallel to each other spaced apart in a width direction orthogonal to an up-down direction of the lens body. Lower ends of the pair of electrodes are disposed spaced apart from the electro-active section in the up-down direction of the lens body.

Abstract: The present disclosure relates to cantilevered and divergent view wearable optical systems that redirect an optical path, and provide for optimal ergonomics coupled with vision enhancement and vision magnification. Methods of use, devices, and kits are also contemplated.

Abstract: Clip-on sunglasses for plastic eyeglass frames are shaped more like a bracket, with a nearly 90° bend to accommodate the thickness of plastic eyeglass frames. The ends of the bracket also angle for 45° towards each other to avoid hitting the nose piece of the plastic eyeglass frame. In the clip-on sunglasses, a latch controls two arms to rotate the arms up to a 45° angle with respect to a pair of plastic eyeglass frames. The arms are formed in three bent portions so as to extend away from an interconnecting rod portion. The three bent portions of the arms allows the latch to fit the shape of the plastic eyeglass frame along the bridge portion of the eyeglass frame as effectively as possible and minimizes movement of the clip-on sunglasses relative to the eyeglass frame.

Abstract: An optical modulator includes: an optical modulator chip having an optical waveguide having a bent waveguide portion that is bent between a light input end portion and a light output end portion, a bias electrode provided between the light input end portion and the bent waveguide portion along the optical waveguide, and a signal electrode provided between the bent waveguide portion and the light output end portion along the optical waveguide; a bias input terminal configured to input a bias voltage, the bias input terminal being electrically connected to the bias electrode, and a signal input terminal configured to input an electric signal, the signal input terminal being provided closer to a receiver configured to receive an electric signal than the bias input terminal and being electrically connected to the signal electrode.

Abstract: Disclosed herein are methods, apparatus, and systems for perturbing an optical beam propagating within a first length of fiber to adjust one or more beam characteristics of the optical beam in the first length of fiber or a second length of fiber or a combination thereof, coupling the perturbed optical beam into a second length of fiber and maintaining at least a portion of one or more adjusted beam characteristics within a second length of fiber having.

Abstract: A modulator drive circuit, including: a first transistor having: a first output terminal connected to a first reference voltage, a second output terminal connected to a first output terminal of the modulator drive circuit, and a control terminal; and a second transistor having: a first output terminal connected to a second reference voltage different from the first reference voltage, a second output terminal connected to the first output terminal of the modulator drive circuit, and a control terminal.

Abstract: Method for determining the characteristics of a system for generating at least one pattern of light, the method comprising: a) providing a desired pattern of light, b) expressing the amplitude and the phase of the output pulse of the system as a function of the input laser pulse and in function of the characteristics of the system to obtain a calculated output pulse, the input laser pulse having a duration below or equal to 1 nanosecond, c) determining at least one characteristic of the system by minimizing a distance between the calculated output pulse and the desired output laser pulse.

Abstract: A display panel includes a plurality of amplifying circuits arranged in a non-display area and a plurality of gate lines. An input terminal of the amplifying circuit is connected to an output terminal of one or more cascade circuit. An output terminal of the amplifying circuit is connected to a gate line. The amplifying circuit is configured to adjust an output signal from the connected cascade circuit to be a scanning signal and output the scanning signal to the gate line. A liquid crystal display using the display panel is also proposed. The present disclosure simplifies the gate driving circuit, thereby solving the problem of unstable signal transmitting among various stages in the gate driving circuit.

Abstract: Disclosed is a foldable display device. According to an embodiment of the present invention, the foldable display device includes a first body and a second body that are formed in the same shape as a plate and are arranged symmetrically with each other, and a hinge device assembled to connect the first body and the second body to each other, such that the hinge device rotates within an opened state range where the first and second bodies are placed on the same plane and within a closed state range where the first and second bodies overlap each other.

Abstract: Disclosed herein includes an assembly structure, including a back cover and a frame. The back cover includes a bottom wall and at least one side wall, wherein the bottom wall and the at least one side wall cooperatively form a housing, and the bottom wall or the at least one side wall is provided with at least one first snap member. The frame includes a load plate and a side plate, wherein the side plate is provided with at least one second snap member. The at least one first snap member and the at least one second snap member are configured to form at least one snap-fit assembly.

Abstract: In one embodiment, the present invention includes a substrate; a detection electrode provided in a display region on a plane parallel to the substrate, the detection electrode including a plurality of metal wires; a first conductive layer provided in a peripheral region located to the outside the display region; a protective layer provided on the detection electrode; a polarizing plate provided above the protective layer; and a second conductive layer provided between the polarizing plate and the protective layer in a direction perpendicular to the substrate. The second conductive layer has a higher sheet resistance than the metal wires and is electrically coupled to the first conductive layer.

Abstract: A light shielding apparatus that may transmit or shield light by using a plurality of PDLC layers, a method of fabricating the light shielding apparatus, and a transparent display device including the light shielding apparatus are discussed. The light shielding apparatus can include first and second substrates facing each other; a first electrode on the first substrate; a second electrode on the second substrate; and first and second polymer dispersed liquid crystal layers between the first electrode and the second electrode, wherein the first polymer dispersed liquid crystal layer includes first droplets having first liquid crystals, and the second polymer dispersed liquid crystal layer includes second droplets having second liquid crystals and first dichroic dyes.

Abstract: A method of preparing a liquid crystal capsule and the use of the liquid crystal capsule. The liquid crystal capsule has advantages in that transmittance and stability are improved and the degree of scattering is uniform.

Abstract: Display device and fabrication method thereof are provided. A display includes a polymer liquid crystal cell, including a first electrode layer, a second electrode layer, and a light-scattering adjustment layer between the first electrode layer and the second electrode layer; and a light source, arranged on a first side of the polymer liquid crystal cell and configured to emit light into the light-scattering adjustment layer. The first electrode layer includes at least one first electrode. The second electrode layer includes at least one second electrode. The display region of the polymer liquid crystal cell includes a plurality of regions having a light-scattering ability increase along a direction away from the light source.

Abstract: The present application discloses a curved display panel having an array of a plurality of pixels along a first direction and a second direction intersecting the first direction. Each of the plurality of pixels includes at least three subpixels of different colors, the at least three subpixels in a same pixel are consecutively along the first direction, a plurality of subpixels consecutively along the second direction in a same row are of a same color from different pixels. The curved display panel includes a display surface curved along a curvature direction. The curvature direction is substantially parallel to the second direction.

Abstract: An array substrate, a display panel and a display device. The array substrate includes a base substrate including a plurality of pixel areas and a first data line on the base substrate and between adjacent pixel areas; a side slope angle of the first data line is not greater than about 60°.

Abstract: A display device panel includes a display area including pixels and a non-display area. Each pixel is connected to one of gate lines and one of data lines. The non-display area includes data pad sections. The non-display area further includes a depiction of a first information code and a depiction of a second information code. The depiction of the first information code is disposed between first two adjacent data pad sections and is apart from an outline of the non-display area by a first distance. The depiction of the second information code is disposed between second two adjacent data pad sections and is apart from the outline of the non-display area by a second distance different from the first distance.

Abstract: A display apparatus includes a first substrate, a plurality of sub-pixel structures, a color filter array, and a display layer. The sub-pixel structures are disposed on the first substrate, and each of the sub-pixel structures includes at least two sub-pixel sub-structures. The color filter array is disposed above the sub-pixel structures, and includes a plurality of filter units. The filter units are divided into a plurality of groups having different colors, and the filter units belonging to the groups having different colors are alternately disposed above the sub-pixel structures. Each of the filter units corresponds to the at least two sub-pixel sub-structures of at least one sub-pixel structure, and the at least two sub-pixel sub-structures of the same sub-pixel structure are adapted to be applied different voltages. The display layer is disposed on the sub-pixel structures.

Abstract: A method for manufacturing a display device can include forming a thin-film transistor (TFT) array substrate including data lines, gate lines, TFTs at intersections of the data lines and the gate lines, common electrodes, common lines disposed parallel to the gate lines, and connected to the common electrodes, a protective layer on the gates lines, the common lines and the data lines, and a first protrusion protruding from the protective layer; and forming a color filter array substrate including first, second and third color filter layers corresponding to first, second and third sub-pixels, respectively, in which portions of the first, second and third color filer layers overlap each other in an area between two adjacent rows of sub-pixels to form a second protrusion, and the second protrusion overlaps with both one common line among the plurality of common lines and one gate line among the gate lines that is adjacent to the one common line, and the area between the two adjacent rows of sub-pixels is configu

Abstract: Provided is a partial drive-type light source device capable of suppressing coloring of a section intended to be a dark section when a plurality of light-emitting elements is driven in a partial manner. The partial drive-type light source device includes an excitation light source, a phosphor sheet that is disposed at a position separated from the excitation light source and contains a phosphor that releases emitted light in a wavelength region differing from incident light, and a wavelength-selective reflection film that is disposed between the excitation light source and the phosphor sheet and that transmits at least part of light in the wavelength region of the incident light from the excitation light source and reflects at least part of light in the wavelength region of the emitted light from the phosphor sheet.

Abstract: A light source device includes: a substrate; a plurality of light sources disposed on the substrate; a wavelength conversion member disposed to face the plurality of light sources; and a diffusion member disposed between the wavelength conversion member and the plurality of light sources, and configured to uniformize distribution of traveling direction angle of incident light.

Abstract: A liquid crystal display includes: a display panel; and a color conversion layer positioned on the display panel, wherein the color conversion layer includes a scattering layer including a color conversion media layer and scatterers.

Abstract: [Problem] The purpose of the present invention is to provide a method for developing a large anchoring energy by simple processes. [Solution] There is provided a method for manufacturing a liquid crystal alignment film, comprising: a process (I) of mixing a solvent with a photoresponsive polymer to prepare a photoresponsive polymer solution; a process (II) of coating the photoresponsive polymer solution on a substrate, followed by drying at 50 to 100° C. for 1 to 3 minutes and then drying at 120° C. to 180° C. for 5 to 75 minutes to form a coating film; and a process (III) of adjusting a temperature of the coating film while the coating film is irradiated with a light of 200 to 350 nm to 40° C. to 100° C.

Abstract: A column for defining the interval between a TFT substrate and an opposed substrate is formed at a crossing point between a drain line and a scanning line. At the crossing point where the column is formed, the drain line is formed to have a wider width to prevent light leakage. Further, at the crossing point where the column is formed, the scanning line is formed to have a narrower width to prevent increase of capacitance between the drain line and the scanning line. The column is formed at a crossing point corresponding to a specific color, e.g., a blue pixel B, so that a difference in transmittance and in characteristic of thin film transistors due to formation of the column is initially compensated.

Abstract: It is possible to separate each liquid crystal display panel from a mother board in which multiple liquid crystal display panels are formed even with a thin glass substrate, by forming a columnar spacer in the boundary between liquid crystal display panels, forming a scribe line corresponding to the columnar spacer on both sides of the counter substrate and the TFT substrate in the mother board, and forming a separation line between the scribe lines by applying a bending stress to the mother board. Since the columnar spacer is formed in a portion corresponding to the scribe line, the strength in this portion increases, so that the proper scribe lines and break lines can be formed when the thickness of the glass substrate is reduced to about 0.15 mm.

Abstract: A display device according to an exemplary embodiment includes: a substrate; a thin film transistor; a pixel electrode; a common electrode; an insulation layer disposed between the pixel electrode and the common electrode; a roof layer spaced apart from the pixel electrode with a plurality of microcavities disposed therebetween; and a liquid crystal layer disposed in the microcavities; wherein the pixel electrode includes n branch electrodes that extend parallel with each other, a first connection electrode that connects a first end of a first branch electrode and a first end of a second branch electrode, and a second connection electrode that connects second ends of the n branch electrodes, where the n branch electrodes each has a shape that is bent at least once on a plan view, and the first branch electrode includes a first sub-branch electrode and a second sub-branch that are spaced apart from each other.

Abstract: Embodiments of the present disclosure provide a liquid crystal display panel, including: a first substrate; a second substrate; and a liquid crystal layer arranged therebetween; the first substrate includes a plurality of sub-pixels, the sub-pixels are divided into a plurality of repeat units arranged in an array, each repeat units includes a plurality of sub-units arranged in an array; in each repeat units, a first sub-unit, a second sub-unit and a third sub-unit are arranged in both a row direction and a column direction; and each of the first sub-unit, the second sub-unit and the third sub-unit includes at least two color sub-pixels and at least two highlight sub-pixels; in each sub-unit, a total number of the color sub-pixel is equal to a total number of the highlight sub-pixel; a total number of the first, second and third color sub-pixel in each sub-unit is the same.

Abstract: A display assembly includes a display unit for displaying an image. The display unit includes a backlight unit configured to provide light. A color conversion layer is positioned adjacent to and configured to receive the light from the backlight unit. A structural layer is positioned adjacent to the color conversion layer and configured to support the display unit. A first stack is positioned adjacent to the structural layer and includes a first thin-film-transistor (TFT) layer, a color filter layer and a first liquid crystal layer. The display unit is configured to be bendable to a fixed shape such that the display unit retains the fixed shape.

Abstract: The present invention provides an array substrate and a manufacturing method thereof. The array substrate includes: a backing plate, a TFT layer arranged on the backing plate, a protective layer covering the backing plate and the TFT layer, a color resist layer arranged on the protective layer, an organic planarization layer set on and covering the color resist layer and the protective layer, and a BPS light-shielding layer arranged on the organic planarization layer. The BPS light-shielding layer includes: a black matrix and a main photo spacer and a sub photo spacer arranged on the black matrix. The organic planarization layer is formed with a first recess in an area thereof that corresponds to at least a part of the black matrix and the first recess is filled up with the black matrix.

Abstract: A liquid crystal display apparatus includes an array substrate, a liquid crystal layer, and an opposite substrate. The array substrate includes a first pixel and a second pixel. The first pixel includes a first active device and a first pixel electrode. The first pixel electrode is electrically connected to the first active device via a first through-hole. The first pixel electrode includes a plurality of first electrode strips extended along a first direction. The first through-hole is located at a first corner of the first pixel electrode. The second pixel includes a second active device and a second pixel electrode. The second pixel electrode is connected to the second active device via a second through-hole. The second pixel electrode includes a plurality of second electrode strips extended along a second direction. The second through-hole is located at a second corner of the second pixel electrode.

Abstract: The present invention discloses an array substrate and a liquid crystal display panel. Each pixel region is connected correspondingly to a data line and two gate line, and each pixel region comprises three sub-pixel electrodes and three switching elements, wherein the first switching element is connected to the first gate line, the first sub-pixel electrode, and the data line, the second switching element is connected to the first gate line, the second sub-pixel electrode and the data line, and the third switching element is connected to the second gate line, a second sub-pixel electrode, and a third sub-pixel electrode. By the above-mentioned technical solution, the present invention can improve the color shift phenomenon when in a large viewing angle and increase the display quality.

Abstract: A liquid crystal display device includes a substrate; a gate electrode on the substrate; a semiconductor pattern layer on the gate electrode; and source and drain electrodes on the semiconductor pattern layer and spaced apart from each other. The source electrode includes: a first facing portion facing the drain electrode; and a first protrusion protruding toward the drain electrode from the first protrusion. The drain electrode includes: a second facing portion facing the source electrode; and a second protrusion protruding toward the source electrode from the second facing portion and facing the first protrusion. The semiconductor pattern layer includes: a source area overlapping the source electrode; a drain area overlapping the drain electrode; and a bridge area connecting the source area with the drain area, and a space defined between the first protrusion and the second protrusion is on the bridge area.

Abstract: The present invention relates to a liquid crystal display including: a lower electrode including a unit pixel electrode; an upper electrode including an upper unit electrode facing the unit pixel electrode; and a liquid crystal layer between the lower electrode and the upper electrode and including a plurality of liquid crystal molecules aligned approximately perpendicular to the surfaces of the lower electrode and the upper electrode in the absence of an electric field, wherein the unit pixel electrode includes a stem forming a boundary between a plurality of sub-regions and a plurality of minute branches extending in different directions in two different sub-regions, the upper unit electrode includes an opening facing the stem and extending parallel to the stem, any alignment aid to pretilt the liquid crystal molecules is absent, and a length of the minute branches is equal to or less than about 53 ?m.

Abstract: A transparent photovoltaic (TPV) integrated directly into the structure of an electrochromic (EC) device is beneficial in that it can eliminate at least one substrate and provide more uniform coloring. Integration of a transparent photovoltaic with an electrochromic device may also reduce or eliminate the need for an electrical bus on a substrate. In some embodiments, positioning the TPV internally with the EC cell may eliminate the need for additional substrate layers or a conductive layer on one side of the TPV cell. Integrating a PV cell into the EC device can additionally reduce the need for external wiring and an external power supply. Alternatively, the TPV can assist in charging a battery where the battery can be used to power the EC device when there is no sunlight available.

Abstract: Optical beam shaping systems and methods can include an illumination source and a diffractive waveplate diffuser. The diffractive waveplate diffuser includes a layer of patterned optically anisotropic material. In one embodiment, the layer of patterned optically anisotropic material is fabricated in the form of patterned, optically anisotropic liquid crystal polymer. In another embodiment, the layer of patterned optically anisotropic material is a layer of liquid crystal, the diffractive waveplate diffuser also includes two alignment layers and two transparent conductive coatings, and the properties of the liquid crystal layer are controlled by the application of an electric potential between the two transparent conductive coatings. A method is provided for designing the alignment pattern of the layer of optically anisotropic material.

Abstract: A liquid crystal lens includes first and second electrodes facing each other, and a liquid crystal layer interposed between the first and second electrodes. The first electrode includes at least one unit pattern. The unit pattern includes a pattern electrode and an aperture. The pattern electrode is disposed adjacent to a boundary of the unit pattern and the aperture is disposed inside the pattern electrode.

Abstract: A method of delivering a beam of laser-radiation to a workpiece for processing the workpiece comprises transmitting the beam twice through an inactive acousto-optic modulator (AOM) crystal in opposite zero-order directions of the AOM at separate locations on the AOM crystal, before delivering the beam to the workpiece. When laser-radiation is to be blocked from reaching the workpiece, the AOM is activated.

Abstract: According to one embodiment, a cavity with a cavity mode which is coupled to physical systems includes a spherical mirror and a plane mirror. The spherical mirror is provided at a birefringent crystal including the physical systems. The plane mirror is provided at the birefringent crystal opposite to the spherical mirror. The birefringent crystal has a first refractive index to light polarized in a first direction parallel to a polarization direction of the cavity mode on an optical axis of the cavity and a second refractive index to light polarized in a second direction parallel to the optical axis, the second refractive index being different from the first refractive index. A cavity length of the cavity and a mode waist radius of the cavity mode satisfy a specific condition.

Abstract: An electronic device is described. The electronic device includes an image sensor that is configured to capture phase detection data for automatic focusing. The electronic device also includes an automatic focusing module that is configured to dynamically enable or disable transmission of the phase detection data from the image sensor. The automatic focusing module may be configured to enable transmission of the phase detection data from the image sensor in response to detecting a scene change.

Abstract: An illumination apparatus which is capable of appropriately determining whether or not a radiating direction of a flash is deviated from a direction targeted by a user and preventing degradation in user convenience. The illumination apparatus has a movable unit that has a light-emitting unit, and a main body unit that holds the movable unit rotatably in a predetermined direction. A present angle of the movable unit with respect to the main body unit is detected, and a difference between the present angle and a target angle to which the movable unit is to be moved is obtained. When the difference is smaller than a threshold value, it is determined that there is no angular deviation of the movable unit. The threshold value used in the determination varies with the target angle.

Abstract: A camera module includes a substrate having a first main surface mounted with an image sensor, a second main surface on the reverse side of the substrate from the first main surface in the predetermined direction, and is provided with at least one hole extending from the first main surface in the predetermined direction. The camera module further includes a holder which has a boss inserted from the first main surface into the at least one hole, and holds at least one lens. The camera module further includes a fixing part made of adhesive that is cured into an anchor shape. The fixing part fixes the boss inside the at least one hole.

Abstract: One embodiment of a camera module can comprise: a lens unit; a holder coupled to the lens unit; a cover member arranged on the top of the holder, and encompassing the lens unit; an image sensing unit arranged on the lower part of the lens unit and the holder; and a thermoelement formed in a hollow shape and encompassing the lens unit, and arranged such that one surface thereof faces the image sensing unit.

Abstract: A light projecting system of a head-up display, which shows a plurality of virtual images on a windshield, includes at least a light source, a panel assembly, and a mirror assembly. The panel assembly includes a first panel generating a first projecting image and a second panel generating a second projecting image. The mirror assembly is provided between the panel assembly and the windshield to reflect the first projecting image of the first panel and the second projecting image of the second panel to image a first virtual image and a second virtual image on the windshield.

Abstract: A wavelength conversion structure and a projection device are provided. The wavelength conversion structure is disposed on a transmission path of an illumination light beam emitted by a light source of the projection device, and includes a rotary disc, a wavelength conversion material, and a scattering-reflective material. The rotary disc has a light-conversion region and a non-light-conversion region. The light-conversion region surrounds the non-light-conversion region. The wavelength conversion material is disposed on the rotary disc, and is aligned to the light-conversion region. An energy gap of the wavelength conversion material is smaller than photon energy of the illumination light beam. The scattering-reflective material is disposed on the rotary disc, and is aligned to the light-conversion region and not aligned to the non-light-conversion region. An energy gap of the scattering-reflective material is larger than the photon energy of the illumination light beam.

Abstract: This invention is concerning an illumination device that can obtain illumination light efficiently. An illumination device 1 used in, for example, a projection display apparatus includes a light source and a light tunnel 14. The light tunnel 14 includes a light incident port 15, a light emission port 16, a light guide path 17, a reflection surface 20 surrounding the light guide path 17, a phosphor layer 19 that generates fluorescent light LF having a different wavelength range from that of excitation light LE when being excited by the excitation light LE, a condensing optical system 13 that diverges the excitation light LE in the vicinity of the light incident port 15 and guides the diverged light into the light tunnel 14 to irradiate the phosphor layer 19, and a wavelength selection element that reflects the fluorescent light LF toward the light emission port 16.

Abstract: A light source unit includes a plurality of light sources that light source elements which emit laser beams and collimator lenses which collect the laser beams emitted from the light source elements are combined therein. Pencils of light emitted from the light source elements are made to be collected in different collecting degrees between the light sources respectively.

Abstract: A projection system is provided, including: a projection unit to output a projection image; a retardation plate arranged obliquely with respect to an optical axis of the projection image, the retardation plate to modulate a polarization state of the projection image incident thereon; a reflective polarizing plate stacked on a side of the retardation plate opposite to that on which the projection image is incident, the reflective polarizing plate to reflect a first polarization component of the projection image transmitted through the retardation plate; and a retro-reflective element provided along a direction in which the projection image is reflected by the reflective polarizing plate, the retro-reflective element to output reflected light against a direction in which the light is incident, wherein the reflective polarizing plate transmits a second polarization component of the projection image reflected by the retro-reflective element and modulated by the retardation plate.

Abstract: A first holding member holds a first optical system and a first mirror, and has a first junction surface. A second holding member holds a second optical system and a second mirror, and has a second junction surface. A junction portion is configured such that, in a state where the first junction surface and the second junction surface are aligned with each other, the second holding member is capable of being shifted in a direction of both the junction surfaces and rotated around an optical axis, and makes it possible to perform optical axis alignment. An emission-side optical axis of the first optical system and an incidence-side optical axis of the second optical system are aligned with each other, and thus a U-shaped optical path is formed by the first and second optical systems.

Abstract: To provide a projection-type image display apparatus which projects an image on a dome screen and a dome type screen apparatus for image projection. An image display apparatus 100 includes a dome screen 101, a support body 102 configured to support the dome screen 101 so that the dome screen 101 is rotatable around a horizontal axis, two projectors 103 and 104 and a display control apparatus 105, and a chair 106 on which a viewer sits is provided inside space. By rotating the dome screen 101, it is possible to expand a viewing field in a vertical direction.

Abstract: The present invention is related to a smile triggered device (1) for encouraging people to smile, the smile triggered device (1) comprising, a frame (2); a mirror (3) having at least one reflecting surface and installed into the frame (2); a switchable material (4) which can be switched to transparent or non-transparent state and covered on the reflecting surface of the mirror (3); a camera (5) capturing images of the user; a control unit (6) connected to the camera (5) and adapted to processes facial expressions of the user in real time for detecting whether the user smile or not, wherein the control unit (6) changing the state of the switchable material (4) to the transparent state by applying voltage thereto if a smile detected. The mirror (4) function of the smile triggered device (1) is maintained until the user changes his facial expression.