Abstract: The invention provides flash imaging devices that include an optical change component that undergoes a change in response to an applied stimulus, a substrate and a stimulus element. Also provided are articles that include the subject devices, as well as methods of making and using the same.

Abstract: According to an embodiment, a distance measuring device includes a light source, a reflection device, a first photodetector and a calculation unit. The reflection device includes a reflection surface configured to scan an object to be measured with light by reflecting the light, and configured to reflect scattered light of the light scattered on the object to be measured. The first photodetector detects the scattered light. The calculation unit calculates a distance from the reflection surface to each of positions on the object to be measured based on a detection result of the first photodetector. The first photodetector includes a photoelectric conversion element including a plurality of detection regions each having different detection sensitivity of the light. The detection regions are arranged in order according to an incident position of the scattered light from the object to be measured at each of positions having the different distance.

Abstract: A photosensor is provided with a sensor circuit assembly. The sensor circuit assembly includes alight emitter, a light receiver, a light-emitter support, a light-receiver support, and a connecting part. The light emitter and the light receiver face each other. The light-emitter support extends from and supports the light emitter. The light-receiver support extends from and supports the light receiver. The connecting part connects one end of the light-emitter support with one end of the light-receiver support. The connecting part includes a seal and a connection terminal that protrudes from the seal. The connection terminal includes a first press-contact part, and a first pressure part that presses the first press-contact part in a press-contact direction.

Abstract: A single-channel phase conjugation apparatus includes a spatial light modulator and a single-channel optical sensing and generating unit. The spatial light modulator receives a light having a wavefront scattered by a scattering object. The single-channel optical sensing and generating unit senses a phase control wavefront of an output light focused by the spatial light modulator and outputs a light having a phase conjugation wavefront by changing a direction of the output light in a reverse direction depending on the phase control wavefront.

Abstract: The present application discloses a display panel comprising a display substrate in a display area and a display circuit board electrically connected to the display substrate; a touch button in a touch button area and a touch button circuit board electrically connected to the touch button; and a connecting line for connecting the display circuit board and the touch button circuit board, the connecting line substantially outside of the display area.

Abstract: Optical ports providing passive alignment connectivity are disclosed. In one embodiment, an optical port includes a substrate having a surface, a photonic silicon chip, a connector body, and a plurality of spacer elements. The photonic silicon chip includes an electrical coupling surface, an upper surface and an optical coupling surface. The optical coupling surface is positioned between the electrical coupling surface and the upper surface. The photonic silicon chip further includes at least one waveguide terminating at the optical coupling surface, and a chip engagement feature disposed on the upper surface. The connector body includes a first alignment feature, a second alignment feature, a mounting surface, and a connector engagement feature at the mounting surface. The connector engagement feature mates with the chip engagement feature. The plurality of spacer elements is disposed between the electrical coupling surface of the photonic silicon chip and the surface of the substrate.

Abstract: An apparatus, system, and method for a mobile, low-cost headset for 3D point of gaze estimation. A point of gaze apparatus may include an eye tracking camera configured to track the movements of a user's eye and a scene camera configured to create a three-dimensional image and a two-dimensional image in the direction of the user's gaze. The point of gaze apparatus may include an image processing module configured to identify a point of gaze of the user and identify an object located at the user's point of gaze by using information from the eye tracking camera and the scene camera.

Abstract: An ultra-thin planar device is used for arbitrary waveform formation on a micrometer scale, regardless of the incident light's polarization. Patterned perforations are made in a 30 nm-thick metal film, creating discrete phase shifts and forming a desired wavefront of cross-polarized, scattered light. The signal-to-noise ratio of these devices is at least one order of magnitude higher than current metallic nano-antenna designs. The focal length of a lens built on such principle can also be adjusted by changing the wavelength of the incident light. All proposed embodiments can be embedded, for example, on a chip or at the end of an optical fiber.

Abstract: A testing device for testing an inner surface of a rotationally symmetrical cavity in a workpiece has a measuring head which defines an axial direction, and on which an optical system is situated. The optical system is in image transmission connection with an image recorder and a downstream evaluation apparatus. The testing device also has an illumination arrangement for illuminating an imaging area of the inner surface which is detected by the optical system. The illumination arrangement is designed and configured for illuminating the inner surface which is detected by the optical system. The illumination arrangement can illuminate the inner surface to be tested from different illumination directions in order to generate shadow images of the topography of the inner surface. The evaluation apparatus is designed and configured for determining the topography based on the shadow images recorded by the image recorder.

Abstract: According to an embodiment, an optical MEMS transducer includes a diffraction structure including alternating first reflective elements and openings arranged in a first plane, a reflection structure including second reflective elements and configured to deflect with respect to the diffraction structure, and an optical element configured to direct a first optical signal at the diffraction structure and the reflection structure and to receive a second optical signal from the diffraction structure and the reflection structure. The second reflective elements are arranged in the first plane when the reflection structure is at rest. Other embodiments include corresponding systems and apparatus, each configured to perform various embodiment methods.

Abstract: The invention relates to an optical system for generating a pattern which changes over time for a confocal microscope. The system includes a light source arrangement, a beam splitter, and a lens arrangement. The beam splitter allows for passage of a light beam proceeding from the light source arrangement in the direction of an object and for deflecting the reflected light beam, reflected by the object in a focal plane, in the direction of a detector. The detector includes a detector pattern for detecting an image of the object. The lens arrangement is between the beam splitter and the object and includes: a light source that generates the light beam, and a device configured to switch a direction of polarization of the light beam to generate a changing projector pattern.

Abstract: An image sensor includes photodiodes arranged in semiconductor material. Each of the photodiodes is identically sized and is fabricated in the semiconductor material with identical semiconductor processing conditions. The photodiodes are organized into virtual large-small groupings including a first photodiode and a second photodiode. Microlenses are disposed over the semiconductor material with each of microlenses disposed over a respective photodiode. A first microlens is disposed over the first photodiode, and a second microlens is disposed over the second photodiode. A mask is disposed between the first microlens and the first photodiode. The mask includes an opening through which a first portion of incident light directed through the first microlens is directed to the first photodiode. A second portion of the incident light directed through the first microlens is blocked by the mask from reaching the first photodiode. There is no mask between the second microlens and the second photodiode.

Abstract: Systems and methods for optical narrowcasting are provided for transmitting various types of content. Optical narrowcasting content indicative of the presence of additional information along with identifying information may be transmitted. The additional information (which may include meaningful amounts of advertising information, media, or any other content) may also be transmitted as optical narrowcasting content. Elements of an optical narrowcasting system may include optical transmitters and optical receivers which can be configured to be operative at distances ranging from, e.g., 400 meters to 1200 meters. Moreover, the elements can be implemented on a miniaturized scale in conjunction with small, user devices such as smartphones, thereby also realizing optical ad-hoc networking, as well as interoperability with other types of data networks. Optically narrowcast content can be used to augment a real-world experience, enhance and/or spawn new forms of social-media and media content.

Abstract: A backlight device includes a plurality of light sources that emit light of different colors from each other, a plurality of color sensors that receive mixed-color light including light emitted from the light sources to detect light emission states of the light sources, a temperature sensor that measures a temperature in a proximity of the plurality of light sources, a brightness conversion unit that separates the mixed-color light to obtain a detection value for each of the light sources by converting values indicating the detected light emission states, and a calculation unit that corrects the obtained detection value by using information indicating a relationship between the measured temperature and a correction value, the calculation unit determining drive values for the light sources based on the corrected detection value.

Abstract: An optical system is provided. The optical system includes a corrector lens that is configured to reduce aberrations in electromagnetic radiation (EMR) received from a window having a window axis of symmetry. A rotation mechanism is coupled to the corrector lens, and is configured to selectively rotate the corrector lens about an optical axis of the corrector lens to maintain a Y-axis of the corrector lens in a same plane as the window axis of symmetry of the window.

Abstract: Devices, systems, and associated methods for capturing three-dimensional (3D) infrared (IR) images are disclosed and described.

Abstract: There is provided in a first form, a system including a detector and a reflector disposed about and proximal to the detector, at least of portion of the reflector being disposed in front of the detector. The reflector is configured to reflect at least a portion of the radiation directed to the system at an angle greater than a first predetermined value onto the detector, and the system is configured so that at least a portion of the radiation directed to the system at an angle less than the first predetermined value directly impinges on the detector.

Abstract: In one aspect, an optical lens assembly (herein referred to also as an optic) is provided that comprises a plurality of lenses (or lens segments) adapted to receive light from a light source, each of said lenses (or lens segments) having an input surface and an output surface and a lateral surface extending between the input and output surfaces. The lenses are arranged relative to one another and positioned relative to the light source such that each of the lenses receives at its input surface a different portion of light emitted by the source, e.g., each lens receives at its input surface light emitted by the source into an angular subtense (solid angle) different than an angular subtense associated with another lens. Each lens (or lens segment) guides at least a portion of the received light to its output surface via reflection, e.g., via total internal reflection (TIR).

Abstract: A constructed photodetector, an optical receiver, and a receiver unit in an optical communication system are disclosed. One example of the disclosed constructed photodetector includes an optoelectronic element having an active area that converts light having a wavelength of interest into electrical signals and a substrate on a face that opposes the active area, where the substrate is non-transparent to light having the wavelength of interest. The constructed photodetector further includes a lens-chip that is at least partially transparent to light having the wavelength of interest, where the lens-chip includes a first side and an opposing second side, where the first side of the lens-chip includes an integrated lens, and where the second side of the lens-chip includes one or more electrical traces. The constructed photodetector further includes at least one connector that provides a physical and electrical connection between the optoelectronic element and the lens-chip.

Abstract: Polarizing beam splitter is disclosed. The polarizing beam splitter includes a first polymeric prism, a second polymeric prism, a reflective polarizer that is disposed between and adhered to a hypotenuse of each of the first and second polymeric prisms, and a hardcoat that is disposed on each of the first and second polymeric prisms. The polarizing beam splitter includes an input major surface and an output major surface. At least one of the input and output major surfaces has a pencil hardness of at least 3H. The polarizing beam splitter has a low birefringence such that when polarized light having a first polarization state enters the optical element from the input major surface and travels through at least 2 mm of the polarizing beam splitter and exits the polarizing beam splitter from the output major surface, at least 95% of light exiting the polarizing beam splitter is polarized has the first polarization state.

Abstract: A scanner and an attenuated total reflection (ATR) objective for use in such scanners are disclosed. The ATR objective includes first and second optical elements and an input port. The input port receives an input collimated light beam that is focused to a point on a planar face of the first optical element by the second optical element such that substantially all of that portion is reflected by the planar face and no portion of the input beam strikes the planar face at an angle less than the critical angle. The second optical element also generates an output collimated light beam from light reflected from the planar thce that is characterized by a central ray that is coincident with the central ray of the input collimated light beam. A light beam converter receives the first collimated light beam and generates the input collimated light beam therefrom.

Abstract: Aspects of the present invention are directed to apparatuses, arrangements, systems and methods for collecting information using one or more modalities. As consistent with one or more embodiments, an apparatus includes first and second scanning mirror arrangements having different scanning axes and respectively facing different directions. The first scanning mirror arrangement directs source light and image light in two paths, and the second scanning mirror arrangement directs image light from a target to the first scanning mirror arrangement. The first and second scanning mirror arrangements cooperatively scan source light from the first scanning mirror and via the second scanning mirror to target locations with at least two degrees of freedom, and direct image light from the target locations.

Abstract: An optical inspection system, the system includes: (i) an image sensor; and (ii) a single optical element, that at least partially surrounds an edge of an inspected object; wherein the optical element is adapted to direct light from different areas of the edge of the inspected object towards the image sensor so that the image sensor concurrently obtains images of the different areas.

Abstract: A portable input device is described. The portable input device can wirelessly send control signals to an external circuit. The control signals can derive from touch or gestures applied to a touch sensitive surface. The control signals can also include a mouse click equivalent control signal generated by mechanical manipulation of the portable input device.

Abstract: Methods, systems, and devices are disclosed for capturing and forming large high quality images using monocentric optical imaging. In one aspect, an optical imaging system includes an optical imaging module that collects light to form an image on an imaging surface, one or more imaging sensors each including an array of optical detectors located away from the imaging surface to receive light representing the image initially formed on the imaging surface and to convert the received light into detector signals, and optical waveguides coupled between the imaging surface and the one or more imaging sensors to receive light from the imaging surface and configured to selectively deliver a desired portion of the received light to the one or more imaging sensors while suppressing undesired stray light from reaching the one or more imaging sensors so that the optical waveguides effectuate an optical aperture stop with a limited angle range for receiving light by the one or more imaging sensors.

Abstract: A system and method are disclosed for reducing light from one or more light sources from entering into a light sensor by reflection off of a visor and/or waveguiding within the visor. In embodiments, a shroud may be provided around the light sensor to block light reflected off of the visor from entering the light sensor. In embodiments, pattern of one or more grooves may be formed in the visor to block light waveguided within the visor from entering the light sensor.

Abstract: An apparatus for outputting directional light includes a light-emitting structure including a light-emitting layer that emits light, and an optical antenna layer disposed on the light-emitting structure, wherein the optical antenna layer includes a light feeder configured to resonate light output from the light-emitting layer and a light reflector configure to reflect light output from the light feeder to have directivity. The light feeder and the light reflector are formed on a surface of the optical antenna layer.

Abstract: A micro-electromechanical apparatus includes a rotary element, at least one restraint and at least two folded springs. The rotary element is capable of rotating with respect to an axis. The folded springs are symmetrically disposed about the axis. Each folded spring has a moving end and a fixed end, the moving end is connected to the rotary element, and the fixed end is connected to the at least one restraint. The moving end is not located on the axis, and the fixed end is not located on the axis. A moving distance is defined as a distance between the moving end and the axis, a fixed distance is defined as a distance between the fixed end and the axis. A spring length is defined as a distance between the moving end and the fixed end. The spring length is varied according to the rotation of the rotary element.

Abstract: There may be provided an evaluation system that may include spatial sensors that include atomic force microscopes (AFMs) and a solid immersion lens. The AFMs are arranged to generate spatial relationship information that is indicative of a spatial relationship between the solid immersion lens and a substrate. The controller is arranged to receive the spatial relationship information and to send correction signals to the at least one location correction element for introducing a desired spatial relationship between the solid immersion lens and the substrate.

Abstract: Provided are a scanner for two-dimensional optical scanning capable of implementing two-dimensional driving by one input signal without an additional structure for modulating a resonance frequency using modulation of the resonance frequency through asymmetry of the scanner itself, and a manufacturing method thereof. In addition, there is provided a manufacturing method of a scanner for two-dimensional optical scanning capable of implementing compact packaging through a micro electro mechanical systems (MEMS) process to miniaturize the scanner, such that it may be used in a micro-miniature system such as an endoscope and capable of increasing precision of the scanner and manufacturing the scanner in various shapes and at a low cost. Further, there is provided a medical imaging apparatus using a scanner for two-dimensional optical scanning capable of providing a medical image having improved quality without crosstalk between axes through separation of resonance frequencies.

Abstract: The present disclosure relates to the active initiation of incident energy-dissipating material from a structure surface coating as a counter measure response for the protection of a structure surface. The active initiation is triggered at a predetermined area or areas on a targeted structure surface in response to incident directed energy sensed on a target surface.

Abstract: A stage apparatus PST is provided with a holder PH, which has a substrate holding surface 33A that holds a substrate P; a stage 52, which supports and moves the holder PH; and a recovery apparatus 60, which is disposed in the vicinity of the holder PH and has lyophilic parts 3, 5 of which at least a part of each is lyophilic, that uses the lyophilic parts 3, 5 to recover a liquid 1. As a result, the infiltration of liquid into the space between the substrate and the holder is prevented, even if performing an exposure treatment by filling the space between a projection optical system and the substrate with the liquid.

Abstract: An example is a lens mirror array in which a plurality of optical elements, which comprises a first lens surface formed at the top of convex portion protruding outwards for converging light, a protrusion which includes a first mirror surface that reflects the light emitted from the first lens surface at the top and a light-shielding surface that has side walls at two sides thereof with respect to a light advancing direction and prevents advance of the light through the side walls, a second mirror surface that reflects the light reflected by the first mirror surface of the protrusion and a second lens surface that images the light emitted from the second mirror surface on an image plane, is arranged in a horizontal scanning direction.

Abstract: The disclosed subject matter provides a nanoaperture having a bottom surface and a side wall comprising gold. A surface of the side wall is passivated with a first functional molecule comprising polyethylene glycol. The bottom surface of the nanoaperture can be functionalized with at least one second molecule comprising polyethylene glycol, for example, a silane-PEG molecule. The second molecule can further include a moiety, such as biotin, which is capable of binding a target biomolecule, which in turn can bind to a biomolecule of interest for single molecule fluorescence imaging analysis. Fabrication techniques of the nanoaperture are also provided.

Abstract: Apparatus and associated methods relate to a light curtain protection system having a passive optical module arranged to receive, from an active optical module, a light signal such that a reflector reflects, through a polarization control module, the light signal to be received by a receiver in the active optical module. In an illustrative example, the polarization control module includes a half-wave plate aligned with the reflector to impart a first predetermined polarization to the reflected light signal such that the reflected light signal corresponds to a second predetermined polarization when received by the receiver. The polarization control module includes optical elements, such as, for example, a linear polarizer, to receive the reflected light such that the optical elements polarizes the received reflected light signal to correspond to a predetermined polarization. In some examples, the light curtain protection system may advantageously require operating power only for the active optical module.

Abstract: A one-dimensional planar beam forming and steering optical phased array chip is a simple building block of a two-dimensional beam forming and steering solid-state lidar, enabling manufacturing of said lidars at high yield and low cost through the use of a plurality of said chips. Innovative photonic integrated circuit chip architectures that follow design for manufacturing rules enable said building blocks.

Abstract: Techniques to determine a distance associated with a surface using time-of-flight (ToF) of pulses of light occurring at a predetermined frequency. A ToF camera may include a light emitter that emits light according to one or more phase delays relative to the configured of a first storage device of multiple storage devices of the ToF camera to receive light, convert to current, and store a charge corresponding to current. For instance, a light emitter may emit pulses at a 0° phase delay (i.e., simultaneously with the opening of the first storage device), a 90° phase delay, a 180° phase delay, and a 270° phase delay. Light captured and stored as energy in the storage devices may be then be analyzed to estimate a distance to a surface of an object in an environment. After estimating a distance between the ToF camera and a surface, the ToF camera may optimize its phase delay to reduce the error associated with a subsequent distance measurement.

Abstract: A solid-state imaging device includes: a first lens layer; and a second lens layer, wherein the second lens layer is formed at least at a periphery of each first microlens formed based on the first lens layer, and the second lens layer present at a central portion of each of the first microlenses is thinner than the second lens layer present at the periphery of the first microlens or no second lens layer is present at the central portion of each of the first microlenses.

Abstract: A micromechanical device for projecting an image and for analyzing an optical spectrum and a corresponding manufacturing method. The device includes: a first light providing unit by which a first light beam is providable to the device; a diffraction unit for diffract the first light beam provided to the device as a function of a diffraction property of the diffraction unit; a second light providing unit by which a second light beam is providable to the device; a micromirror by which the second light beam provided to the device is variably deflectable as a function of a position and/or an orientation of the first micromirror; and a first actuator by which the adjustable diffraction property of the optical diffraction unit and also the position and/or the orientation of the micromirror are adjustable.

Abstract: An optical spectrometer contains a photodiode and a straining mechanism for imposing adjustable strain on the photodiode. The spectrometer includes a measurement apparatus for measuring variation of photocurrent with strain at different values of the adjustable strain imposed by the straining mechanism. Adjusting the strain allows adjustment of the band gap Eg of the photosensitive region of the photodiode, and this determines the cut-off energy for absorption of photons. Measuring variation of photocurrent with strain at different values of the adjustable strain imposed by the straining mechanism allows study of photons within a desired energy range of the band gap energy corresponding to each strain value.

Abstract: A display apparatus including an optical component and an optical fiber component is provided. The display may include an optical component including a sensor, and an optical fiber component configured to transmit the electromagnetic transmission being incident on a front frame, to the sensor. A display apparatus may transmit light being incident from the outside to a sensor of an optical unit through an optical fiber unit, and transmits light being outputted from the sensor of the optical unit to the outside through the optical fiber unit.

Abstract: An image capturing apparatus includes a main body and a rotatable image capturing unit. The main body includes a spherical portion having at least three support points. The rotatable image capturing unit includes an image capturing optical system, and is configured to rotationally move while being supported by the support points. In the rotatable image capturing unit, a gravitational point is located so as to overlap a center of gravity of a polygonal plane formed by connecting the support points and present on a side closer to an image sensor the polygonal plane in a direction perpendicular to the polygonal plane.

Abstract: Backside illuminated photosensitive devices and associated methods are provided. In one aspect, for example, a backside-illuminated photosensitive imager device can include a semiconductor substrate having multiple doped regions forming a least one junction, a textured region coupled to the semiconductor substrate and positioned to interact with electromagnetic radiation where the textured region includes surface features sized and positioned to facilitate tuning to a preselected wavelength of light, and a dielectric region positioned between the textured region and the at least one junction. The dielectric region is positioned to isolate the at least one junction from the textured region, and the semiconductor substrate and the textured region are positioned such that incoming electromagnetic radiation passes through the semiconductor substrate before contacting the textured region.

Abstract: A system and method for metered dosage illumination in a bioanalysis or other system. In accordance with an embodiment, an illumination system or subsystem is described that can provide optimized amounts of excitation light within the short exposure times necessary to measure fast biological activity. The amount of light can be precisely measured to provide quantitative results. The light flux can also be precisely controlled to generate only a prescribed minimum amount of light, in order to reduce adverse lighting effects on both fluors and samples. Although the examples herein illustrate the providing of metered dosage illumination in the context of a bioanalysis system, the techniques can be similarly used to provide metered dosage illumination in the context of other types of system. In accordance with various embodiments, the technique is particularly useful in any quality-control, analysis, or assessment-based environment.

Abstract: An optical scanner system comprises a housing, a detector contained within the housing configured to produce at least two resolvable azimuth fields-of-view relative to a center-axis of the housing, and an external scanner rotating relative to the center-axis of the housing, and switching between at least two elevations relative to a nominal optical axis of a receiver. Motion of the housing azimuthally results in the receiver producing a continuous coverage pattern at multiple elevations produced by the external scanner.

Abstract: Systems and methods for optical narrowcasting are provided for transmitting various types of content. Optical narrowcasting content indicative of the presence of additional information along with identifying information may be transmitted. The additional information (which may include meaningful amounts of advertising information, media, or any other content) may also be transmitted as optical narrowcasting content. Elements of an optical narrowcasting system may include optical transmitters and optical receivers which can be configured to be operative at distances ranging from, e.g., 400 meters to 1200 meters. Moreover, the elements can be implemented on a miniaturized scale in conjunction with small, user devices such as smartphones, thereby also realizing optical ad-hoc networking, as well as interoperability with other types of data networks. Optically narrowcast content can be used to augment a real-world experience, enhance and/or spawn new forms of social-media and media content.

Abstract: Methods for detecting and analyzing individual nanoparticles of the same, similar, or different sizes co-existing in a fluid sample using multi-spectral analysis are disclosed. A plurality of light sources may be configured to produce a plurality of light beams at different spectral wavebands. An optical assembly may be configured to combine the plurality of light beams into one or more incident light sheets. Each incident light sheet may illuminate one or more nanoparticles in a liquid sample. One or more image detectors may be configured to detect, using a plurality of wavelengths, light scattered or emitted by one or more nanoparticles. The plurality of wavelengths may correspond to the different spectral wavebands of the plurality of light beams. Related apparatus, systems, techniques, and articles are also described.

Abstract: Provided are a head having improved usability by limiting a movement range of a laser spot and an atomic force microscope having the same. A head according to an exemplary embodiment of the present disclosure is a head measuring bending of a cantilever by using a laser beam reflected on the surface of the cantilever in order to acquire information on a sample surface by using a tip of the cantilever. The head includes: a spot moving means configured to move a laser spot so as to position the laser spot on the surface of the cantilever; and a movement limiting means configured to limit a movement range of the laser spot moved by the spot moving means in a predetermined range.

Abstract: The invention relates to an optoelectronic module, more particularly to an optoelectronic chip-on-board module. The optoelectronic module comprises a substrate, wherein the substrate has a planar design. Furthermore, the optoelectronic module comprises a plurality of optoelectronic components that are arranged on the substrate. Furthermore, the optoelectronic module comprises a lens system having a plurality of lenses. The lens system comprises at least two lenses with different directivities.

Abstract: An optical element for terahertz waves that transmits terahertz-wave incident beams through itself after being compressed into half or less a wavelength of the beam, the optical element comprising: a substrate that allows terahertz waves to be transmitted through itself; and a conductive coat that covers a surface of the substrate and is capable of blocking the waves, wherein the coat has an aperture provided in a circular region and ring-shaped grooves, provided on a surface of the coat, having the same center as the circular region and having radii which increase every fixed length, and wherein in the circular region, four or more fan-shaped tips each having an arc with the same radius of curvature as the radius of the region, are arranged at equal distances toward the center of the circle without contacting each other as the arc contacts an outer periphery of the region.