Abstract: A filter wheel and a spectrometer including the filter wheel are disclosed. The filter wheel has a first support structure on which a first plurality of filters are mounted and a second support structure on which at least one filter is provided. A radiation source generates a radiation beam, and a beam splitter splits the radiation beam into a first detection path and a second detection path. The first plurality of filters are selectively movable into the first detection path. The at least one filter on the second support structure is arranged to be disposed in the second detection path. The spectrometer includes a first radiation detector that detects radiation that passes through the selected filter in the first detection path, and a second radiation detector that detects radiation passing through the filter in the second detection path.

Abstract: A light-filtering module includes a light-source module, a dichroic mirror and a first image unit. The light-source module outputs a light beam. The dichroic mirror divides the light beam into a first colored light and a dual colored light. The first image unit provides the first colored light with image information. The light-filtering module includes a light-filtering unit and a driving unit. The light-filtering unit is located between the dichroic mirror and the first image unit is located at a light path of the first colored light. The driving unit includes a coupling element coupled to the light-filtering unit and a driving element utilized to drive the coupling element. The driving element drives the light-filtering unit, switching between a first status and a second status by the coupling element. A wide-wavelength spectrum and a narrow-wavelength spectrum are provided when the light-filtering unit is in the first and second statuses, respectively.

Abstract: A wavelength-specific optical switch combines one or more tunable filters and bandblock reflectors such that the absorption or reflection of selected wavelength bands in the optical spectrum (visible, near infrared, or near ultraviolet) can be switched on and off. The wavelength switch is programmable, multifunctional, general-purpose, solid-state optical filter. The wavelength switch may serve as a tunable notch or bandblock filter, a tunable bandpass filter, a tunable highpass or lowpass filter, or a tunable band reflector. The wavelength switch has particular, but not exclusive, application in optics as a filter, band reflector, and as a means of isolating particular wavelengths or wavelength bands from a collimated light stream for transmission to, or rejection from, a sensor.

Abstract: An incident-light controlling apparatus has a first aperture in a substrate, a diaphragm blade which rotates around an axis, and controls light passing through the first aperture, by the diaphragm blade rotating alternately between a first stationary position coinciding with the first aperture, and a second stationary position retracted from the first aperture, a permanent magnet joined directly to the diaphragm blade, at a position of the axis of rotation of the diaphragm blade, and magnetized in a direction of a plane of rotation of the diaphragm blade, and a pair of coils having a winding around cores disposed such that an end portion of each coil faces the magnet. The diaphragm blade rotated alternately between the first and second stationary positions due to an interaction between a generated magnetic field upon passing an electric power, and a magnetic field generated due to the magnet.

Abstract: A light fixture having at least one light source for generating a beam of light, a plurality of color filters are rotatable into position to intercept the light beam. The color filters are fixed to the color wheel by a central spring which has a number of radial protruding tongues for fixation of the color filters. The color filters are removable yet are secured in a correct position by radial protrusions formed between the color filters an circular outer protrusion located outward of the color filters so as to form a cavity that surrounds the color filter at both sides as well as at outward. Inward of the color filters, they are fixed by the protruding tongue that presses them down and keeps them in place. This leads to a nearly perfect fixation of each color filter, which can be exchanged if necessary.

Abstract: A diaphragm device with which individual wavelengths or ranges of wavelengths in the path of a beam of spectrally dispersed light can be suppressed. Such a diaphragm device comprises at least one array of diaphragms, wherein the individual diaphragms of the array are arranged in a definite relation to each other and may be coupled in the path of the beam and each diaphragm of the array in the coupled state is arranged in a given relation to an individual wavelength or a range of wavelengths.

Abstract: An optical performance is deteriorated by a minute phase difference of transmission wave front of an ND filter. In a light quantity adjusting device which includes an ND filter (P1) for attenuating a quantity of light passing through an aperture formed by diaphragm blades (S11 and S12) and in which a cover ratio of the aperture by the ND filter (P1) is changed, setting is conducted such that a phase difference between lights with a predetermined wavelength ? which pass through regions (N11, N12, and N13) of the ND filter (P1) with different transmittances inside the aperture becomes substantially 0?, substantially 1?, or substantially 2? in a state in which the aperture is completely covered with the ND filter (P1).

Abstract: A light adjusting apparatus includes a substrate (10, 40) having an aperture, a plurality of incident light adjusting units (20a, 20b, 20c) each moving in a same plane, and a plurality of driving units (50a, 50b, 50c) respectively driving the incident light adjusting units (20a, 20b, 20c), and adjusts an incident light passing through the aperture by mutually moving the incident light adjusting units (20a, 20b, 20c) with the driving units to an aperture position that is center-aligned with the aperture and a retracted position that is retracted from the aperture. An incident light adjusting unit that is moved to the aperture position is positioned by contacting with at least one of other incident light adjusting units that are retracted from the aperture.

Abstract: An optical filter device switches two different optical filters through a frame with the optical filters received therein and being received in a seat formed on a casing. A driver fixed on the casing is employed to drives the frame through a gear fixed on the casing and engaged to the frame.

Abstract: A switching mechanism for a camera includes: a control unit; a driving device coupled with and actuated by the control unit; a first gear set coupled with the driving device; a second gear coupled with the first gear set and centrally provided with a rotary shaft having a shaft hole formed with threads; a spindle being female-connected to the shaft hole and which has an axial surface formed with outer threads corresponding to the threads of the shaft hole, thus allowing the second gear to move along and relative to the spindle; and a translation member positioned perpendicular to the spindle and provided with a rack for engaging with the second gear and thus driving the translation member to move perpendicular to the spindle. The second gear drives or does not drive the rack as the engagement therebetween is made or broken.

Abstract: A color wheel has one or a plurality of color filter segments made from a first material, typically glass, having a coefficient of thermal expansion that is substantially different from a carrier, which is made from a second material, typically aluminum. An intermediate washer or coating is disposed in between the segment(s) and the carrier, and has a coefficient of thermal expansion either equal to the segment(s) or in between that of the segment(s) and the carrier. The segment(s) is/are adhered to the washer or coating via a rigid or strong adhesive capable to withstand the strong centrifugal forces associated with rotating the color wheel and the filter segments at high speed.

Abstract: A flexible medium for a scrolling color changer and method of making thereof. The medium is made by applying an ink using a Meyer Rod which has varying cell lengths along its length. This leaves varying size cells of ink at different locations along the length of the medium. The ink has special characteristics whereby its evaporation rate and viscosity are carefully controlled. The viscosity is such that an amount of levelling will occur will be equal to the distance between any cells, but that cell to cell levelling will not, in general, occur.

Abstract: The invention relates to a device supplying an electrical signal for which a characteristic, for example, the voltage is adjustable. The device has a connector at one end of a cable to supply this signal to another electrical device. This connector comprises a transmission means of a light signal for which a visible characteristic depends upon the electrical signal produced. One improvement consists in the light signal coming from a source of white light that is colour modulated by filters. These filters are mechanically integrated into a mobile part belonging to the adjustment means of the signal supplied. The invention also relates to a system comprising the device supplying the signal and the device to be connected, the latter device features a mark identifying the light signal compatible with the electrical signal to receive.

Abstract: A diaphragm device with which individual wavelengths or ranges of wavelengths in the path of a beam of spectrally dispersed light can be suppressed. Such a diaphragm device comprises at least one array of diaphragms, wherein the individual diaphragms of the array are arranged in a definite relation to each other and may be coupled in the path of the beam and each diaphragm of the array in the coupled state is arranged in a given relation to an individual wavelength or a range of wavelengths.

Abstract: A method for enhancing underwater imaging affected by image degradation effects, the method comprising: acquiring at least one image of an underwater scene using an imaging device; determining information regarding distances of parts of the scene relative to the imaging device; and reconstructing an image of the underwater scene using a physics-based mathematical model, compensating image characteristics influenced by distance-dependent underwater degradation effects including veiling light, using the information on the distances of parts of the scene from the imaging device, and compensating distance-dependent underwater degradation effects relating to the distance of illumination sources from the scene.

Abstract: A color wheel module includes a color wheel having a side face defining a plurality of color regions and a detection region, a light source for emitting light beams toward the side face of the color wheel and a light detection device for detecting the light beams from the color regions and the detection region in order to locate position of the color regions and the detection region.

Abstract: A lens device comprises: an image-formation optical system that converges an incident luminous flux at an imaging element, to form an image; a diaphragm mechanism provided in the image-formation optical system; and a filter section that is provided on a subject side of the imaging element and through which the luminous flux incident on the image-formation optical system travels, wherein the filter section comprises: an infrared-ray cutoff filter; and a neutral density filter, and wherein the lens device further comprises a filter switching mechanism that places the infrared-ray cutoff filter and the neutral density filter in a range through which the luminous flux travels at the time of photographing of a high-luminance subject.

Abstract: An imaging apparatus may include an infrared cutoff filter capable of being inserted into and extracted from an incident light path to an image sensing device, and may further include a first detecting unit configured to, when the infrared cutoff filter is off the incident light path to the image sensing device, detect whether the difference between current illuminance of a subject acquired from an image signal of the subject sensed by the image sensing device and a reference value of the illuminance of the subject determined after the infrared cutoff filter was extracted is equal to or greater than a first threshold value, and a filter control unit configured to, when the first detecting unit detects that the difference between the current illuminance and the reference value is equal to or greater than the first threshold value, insert the infrared cutoff filter into the incident light path.

Abstract: Provided herein are devices, systems, and methods for multimodal optical imaging. The devices include a filter assembly that is capable of rotary action during real time image acquisition. The systems include such filter assemblies, which are detachable or integrated in the systems. The methods include techniques for capturing image targets using multiple light sources such as white light and fluorescent light.

Abstract: A diaphragm device with which individual wavelengths or ranges of wavelengths in the path of a beam of spectrally dispersed light can be suppressed. Such a diaphragm device comprises at least one array of diaphragms, wherein the individual diaphragms of the array are arranged in a definite relation to each other and may be coupled in the path of the beam and each diaphragm of the array in the coupled state is arranged in a given relation to an individual wavelength or a range of wavelengths.

Abstract: An apparatus for forming an image has one or more lenses in an optical path, at least one angular-sensitive light transmission filter in the optical path, in which transmission varies with change in angular orientation of the filter with reference to the direction of light in the optical path, and a mechanism for adjusting the angle of the light transmission filter.

Abstract: A filter switching device includes: an optical filter unit that is disposed on an optical path of an object light that passes through an image pickup lens of a camera, and can be switched to any one of a plurality of spectral transmission characteristics; a spectral transmission characteristic switching unit that switches a spectral transmission characteristic of the optical filter unit to one of the plurality of spectral transmission characteristics; a filter spectral transmission characteristic information storage unit that stores filter spectral transmission characteristic information, which is information relating to each of the plurality of spectral transmission characteristics; and a filter spectral transmission characteristic information output unit that outputs filter spectral transmission characteristic information corresponding to the spectral transmission characteristic of the optical filter unit to the camera when the spectral transmission characteristic of the optical filter unit is switched.

Abstract: A sequential illumination system for a visual display unit has a light source emitting a polychromatic light beam towards the visual display unit within a wavelength range having at least three primary colors, and a color wheel provided with at least three transmissive or reflective segments for transmitting the light beam along an optical path in such a way that they successively cut the direction of propagation of the beam. The colour segments are distributed on the wheel in such an order that the differences of energies perceived by the visual organ of a standard observer (visual stimuli), are as equivalent as possible during the intersegment transitions, when the segments pass along the optical path of the beam. The illumination system can be used for movie overhead projection devices.

Abstract: A multi-mode color filter 400 having an inner hub region 402 used to mount the color filter 400 to a motor shaft. A first track 404 and a second track 406 of color filter segments are formed on the color filter, as is an optional clear track 406. The first and second tracks each have a different set of color filters. One set of filters is chosen to improve image brightness, another set is selected to improve color saturation. Typically, the set of filters used to improve brightness includes one or more clear segments, while the set of filters selected to improve color saturation does not. Depending on the image being projected, the user or the display controller moves the color wheel to select a particular filter set.

Abstract: A bandstop filter method and system for suppressing ASE noise is disclosed. In one embodiment of the bandstop filter system, there is provided a first switch, having an input port for receiving an optical signal, and two output ports; a bandstop filter coupled to a first of the two output ports of the first switch; and a second switch, having two input ports and one output port, wherein a first of the two input ports of the second switch is coupled to the bandstop filter and a second of the two input ports of the second switch is coupled to a second of the two output ports of the first switch.

Abstract: A color wheel includes a motor defining a rotating portion, a color filter, a sensor and a processor electrically connected to the sensor. The rotating portion defines a groove at the periphery of the rotating portion to aid the sensor in detecting a color index position of the color filter during transmission of light beams to the rotating portion from the sensor. When portions of light beams are striken the groove of the rotating portion, they are substantially absorbed by the groove and cannot be reflected back to the sensor, thereby the sensor can accurately detect the color index position of the color filter during the rotation of the color filter.

Abstract: A wavelength-specific optical switch combines one or more tunable filters and bandblock reflectors such that the absorption or reflection of selected wavelength bands in the optical spectrum (visible, near infrared, or near ultraviolet) can be switched on and off. The wavelength switch is programmable, multifunctional, general-purpose, solid-state optical filter. The wavelength switch may serve as a tunable notch or bandblock filter, a tunable bandpass filter, a tunable highpass or lowpass filter, or a tunable band reflector. The wavelength switch has particular, but not exclusive, application in optics as a filter, band reflector, and as a means of isolating particular wavelengths or wavelength bands from a collimated light stream for transmission to, or rejection from, a sensor.

Abstract: The invention relates to a device supplying an electrical signal for which a characteristic, for example, the voltage is adjustable. The device has a connector at one end of a cable to supply this signal to another electrical device. This connector comprises a transmission means of a light signal for which a visible characteristic depends upon the electrical signal produced. One improvement consists in the light signal coming from a source of white light that is colour modulated by filters. These filters are mechanically integrated into a mobile part belonging to the adjustment means of the signal supplied. The invention also relates to a system comprising the device supplying the signal and the device to be connected, the latter device features a mark identifying the light signal compatible with the electrical signal to receive.

Abstract: A system in at least some embodiments comprises a housing containing a processor and a base coupled and supporting the housing. The housing comprises a slot adapted to receive a removable template. A slot is provided within the housing. The slot is adapted to receive a removable template. The housing also comprises a light source that shines through the template on to the base.

Abstract: An exemplary color wheel includes a motor, a carrier, a color filter unit, and a fixing member. The carrier includes a main body fixed to the motor and a tapered spindle extending from the main body and away from the motor. The tapered spindle defines an axial hole therein. The color filter unit defines an opening at a central portion thereof. The opening is shaped as but smaller than the tapered spindle and receives a portion of the tapered spindle. The fixing member includes a head pressing on the color filter unit and a shank extending from the head. The shank is engaged in the axial hole of the tapered spindle.

Abstract: The invention concerns with an exposure control mechanism for use in an image pickup apparatus in which a diaphragm aperture formed by a plurality of diaphragm blades moving straightforward in opposite directions is covered by an ND filter, and intends to prevent deterioration of image quality caused by diffraction even in an image pickup device having a small picture size and a short pixel pitch. The image pickup apparatus comprises an exposure control mechanism for adjusting the quantity of light flux entering a shooting lens system. The exposure control mechanism comprises a diaphragm made up of diaphragm blades movable on a plane perpendicular to an optical axis in opposite directions to define a diaphragm aperture, and an ND filter made up of at least two ND filter elements having different transmittances.

Abstract: A color filter assembly rotates around a central axis thereof and includes a carrier defining a radially extending holes, a color filter fixed to the carrier, and a balancing element movably received and selectively positionable along each hole. Selectively positioning the balancing with respect to the central axis allows for statically balancing of mass and adjustment of the center of mass thereby enhancing rotation stability of the color filter assembly.

Abstract: The invention relates to an electronic imaging system such a video camera or digital camera, whose thickness or size is reduced while performance degradation is reduced as much as possible. The system comprises a zoom lens system comprising a first G1, a second G2, a third G3 and a fourth lens group G4 and an aperture stop S, and an electronic image pickup device located on its image side I and covered with a cover glass CG. The image of a subject is formed on the photoreceptive surface of the electronic image pickup device for conversion into electric signals. The system satisfies the following conditions (1) and (2). a?4 ?m??(1) F>a??(2) Here a is the horizontal pixel pitch in ?m of the electronic image pickup device and F is the F-number of the zoom lens system at its wide-angle end.

Abstract: The invention relates to a device for the IR-spectrometric analysis of a solid, liquid or gaseous medium. The device includes a process probe, which has a reflection element. The device additionally includes a linear variable filter, at least one detector element, and a control/evaluation unit. At least one light source is also provided, the light of which is coupled into the reflection element via a collimating optics. At least one optical waveguide having a light input section and a light output section is provided. The light is guided via the light output section of the optical waveguide into a defined region of the linear variable filter. The detector element and the linear variable filter are arranged movably relative to one another over approximately the length of the linear variable filter. The control/evaluation unit determines the spectrum of the medium on the basis of the measured values delivered from the detector element.

Abstract: A color wheel includes a plurality of color filter segments disposed so as to form a disk configuration, and a support member to fixedly set the plurality of color filter segments in place. Each of the color filter segments has a circular outer circumference, an inner circumference measuring shorter than the outer circumference, and two sides each connecting between the outer circumference and the inner circumference. In the color wheel described above, a chamfer is provided at the innermost portion of at least one of the two sides. The chamfer provides a clearance between opposing sides of any two adjacent color filter segments, so as to house burrs that are often formed at the sides, and therefore the opposing sides are fitted closely to each other even when burrs are formed at the sides. Consequently, spokes generated between two adjacent color filter segments can be minimized.

Abstract: An exemplary color wheel includes a motor, a locking member, an annular color filter assembly, and an elastic member. The motor includes a rotating shaft, a stop portion, and a lock-receiving portion. The stop portion is fixed to the rotating shaft, and the lock-receiving portion is defined in the rotating shaft. The locking member is lockably received by the lock-receiving portion. The color filter assembly is disposed on the stop portion. The elastic member is interposed between the color filter assembly and the locking member and is compressed therebetween, so as to push the color filter assembly against the stop portion.

Abstract: A color wheel includes a motor having a rotary shaft, and a filter set sleeved on the rotary shaft. The filter set including a filter plate having a central axis and upper and lower surfaces, and a first and a second packing disposed concentrically and respectively on the upper and lower surfaces of the filter plate. The first packing has a first notch formed therein. The second packing has a second notch formed in an upper surface thereof. An adhering unit is provided in the first and second notches to fix respectively the first and second packing to the upper and lower surfaces of the filter plate.

Abstract: A color wheel unit includes: a color wheel including a plurality of color regions; a motor adapted to rotate the color wheel and including a rotor with a rotary shaft; and a case adapted to house the color wheel and the motor and including a heat radiating means disposed at the outer surface of the case. In the color wheel unit, a first protrusion structure extending radially outwardly is disposed at the outer circumferential surface of the rotor, and a second protrusion structure extending radially inwardly is disposed at the inner surface of the case, wherein the projection area of the second protrusion structure on the plane orthogonal to the rotary shaft of the rotor is overlapped at least partly with the projection area of the first protrusion structure on the plane orthogonal to the rotary shaft of the rotor.

Abstract: A scrolling colour projection system comprising a lamp (4) with a pulsed drive current (20) and a colour scanner (6, 8a, 8b, 8c, 9) for generating a light beam (5b) with a plurality of scrolling colour fields, which is arranged to illuminate a display device (3) to produce a projection of an image generated by the display device. The system further includes a filtering element (31) arranged in the light path between the lamp and the projected image, and the transmission of the filtering element (31) is synchronized with the lamp current so as to cancel an intensity peak in the lamp flux. The filtering element thus effectively removes the impact of the current pulse on the light intensity, resulting in a constant intensity in the projected image, and avoiding any interference patterns.

Abstract: A color wheel for use in projector systems comprises a disc shaped hub, rotatable around a central axis and color filter segments arranged radially to said central axis and affixed to said hub. This color ring is arranged concentrically with respect to said axis and said segments' contour comprising an outer arc, an inner arc and two radial parts. Each of the radial parts comprises a recess arranged such that during assembly of said segments pairs of neighboring recesses form a hole which again engages in a corresponding peg on the hub in a form fitting manner.

Abstract: This invention decreases deformation of a plastic substrate caused by thermal expansion and contraction in an evaporation process of forming a multi-layered film of an ND filter, thus helping prevent wrinkles. The plastic substrate serving as the base of the ND filter is made of a polyimide-based plastic material having a glass transition temperature of 200° C. or more, has a total transmittance of light of 90% or more, and has a haze factor of 0.5% or less. As the multi-layered film, Al2O3 films for reduction of the reflectance and TiOx films for reduction of the transmittance are alternately formed on the substrate.

Abstract: In a color wheel comprising a plurality of color filter segments arranged so as to form a disk and a support member fixed to the color filter segments, the color filter segments are each outlined only by a circular arc and two straight lines passing through the center of the disk. Consequently, each of the color filter segments is prepared by cutting the material only to the circular arc and the two straight lines, thereby simplifying the production process. And, the support member can be duly and surely positioned such that the center of the support member is set to coincide with the intersecting point of the two straight lines. Thus, the positional accuracy, the component cost reduction, and the production cost reduction can be achieved at the same time.

Abstract: A method for fabricating a monolithic color wheel. The method includes (a) preparing a square transparent substrate; (b) forming a plurality of color filters on the square transparent substrate; and (c) cutting the square transparent substrate and the color filters together along a circular path, to form a color filter disk. Through these steps, a color filter disk of color wheel can be produced with better dynamic equilibrium quality, and will run more quietly and smoothly.

Abstract: A reflective color wheel is adapted to receive composite source light provided by a light source, and includes a plurality of multi-layer light-reflecting sections for splitting the composite source light into a plurality of colored light beam components. Each of the multi-layer light-reflecting sections includes a plurality of light-filtering layers stacked along an axis. Each of the light-filtering layers of each of the multi-layer light-reflecting sections is capable of reflecting light within a predefined distinct wavelength range, and permits transmission of light outside the predefined distinct wavelength range therethrough. Sequences of the light-filtering layers of an adjacent pair of the multi-layer light-reflecting sections are different from each other.

Abstract: An ND filter is made of a transparent substrate having a plane. An optical film is formed on the plane of the transparent substrate. The optical film has a lamination structure including a light absorption film and a dielectric film, and has a variable transmission density. A thickness of either the light absorption film or the dielectric film of the lamination structure is changed in an in-plane direction of the transparent substrate so that the transmission density of the optical film is controlled to vary in the in-plane direction. The light absorption film is composed of a material selected from Ti, Cr, Ni, NiCr, NiFe, NiTi and a mixture thereof, and the dielectric film is formed of SiO2, Al2O3 or a compound thereof.

Abstract: A coating method for a color filter, including the steps of: coating a first photoresist layer on a substrate; forming at least a aligning pattern and a first color film pattern on the first photoresist layer by exposure and development; coating a first dye on the aligning pattern and the first color film pattern; stripping the first photoresist layer; coating a second photoresist layer on the substrate, wherein the aligning pattern and the first color film pattern are formed on the substrate; aligning position by using the aligning pattern of the substrate; forming a second color film pattern on the second photoresist layer by exposure and development; coating a second dye on the second color film pattern; and stripping the second photoresist layer. The invention also discloses an aligning-assembling method for a color wheel, which includes the color filter.

Abstract: A method and a color rendering filter for compensating for deficiency in illumination light from a light source in display systems are provided. The color rendering filter has a color that is determined based upon the spectrum, sensitivity of viewer's eyes over the visible light range, and a pre-determined waveband threshold.

Abstract: A method for balancing a color wheel. The rotational unbalance vector of a driving motor is measured, including its unbalance amount and direction. The unbalance of a color wheel is adjusted to make its unbalance amount to be the same of the driving motor. The color wheel is connected to the driving motor so that the unbalance direction thereof is opposite to each other to reach an expected balance. The color wheel structure includes a set of color filter and a ring, before starting the assembly, adjusting the unbalance vector of the ring and motor shaft first, and then to assemble it and make the unbalance vectors opposite.

Abstract: There is provided a color wheel including a plurality of color filters arranged so as to form a disk, and a retainer member disposed at a center of the disk and formed into a C-ring defining an open mouth portion through which an area of one color filter is exposed. Also, there is provided a color wheel assembly which incorporates the color wheel described above, and which further includes a motor to rotate the color wheel, and a rotational position detector to optically detect a rotational position of the color wheel. Detection light emitted from the detector is set to fall incident on the C-ringed retainer member while the color wheel is rotated thus intermittently impinging on the open mouth portion, namely on the one color filter, which causes the detection light reflected thereby to come out with two different intensities that are sensed by the detector.

Abstract: A process for making a unitary color filter disc includes the steps of preparing a disc member having an annular surface, and providing a plurality of differently colored segments on the annular surface. Each of the colored segments is provided by partially masking the annular surface to expose a part of the annular surface and by directly depositing a coloring film on the exposed part of the annular surface.