11:5
`United States Patent
`5,933,183
`[11] Patent Number:
`[45] Date of Patent:
`Aug.3, 1999
`Enomoto et al.
`
`US005933183A
`
`[54] COLOR SPATIAL LIGHT MODULATOR AND
`COLOR PRINTER USING THE SAME
`
`displays”, O plus E (a magazine), Oct. 1994, No. 179, pp.
`90-94.
`
`[75]
`
`Inventors: Jun Enomoto; Hiroaki Nakamura,
`both of Kanagawa, Japan
`
`[73] Assignee: Fuji Photo Film Co., Ltd., Kanagawa,
`Japan
`
`[21] Appl. No.: 08/763,662
`
`[22]
`
`[30]
`
`Filed:
`
`Dec. 11, 1996
`
`Foreign Application Priority Data
`
`Dec. 12,1995
`Dec. 13,1995
`
`[JP]
`[JP]
`
`Japan vecesesssssecsssssseeseseesseone 7-323310
`Japan oo eeeseeeen ene cnee 7-324656
`
`Int. ChSee HOAN 1/40; GOID 9/42
`[S51]
`[52] U.S. Che cece 347/241; 347/239; 359/224;
`359/292
`[58] Field of Search oer 347/239, 241;
`359/223, 224, 292
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`3/1989 Sangyoji et al. cesses: 349/2
`4,810,058
`w 347/238
`4,875,057 10/1989 Hedigeret al.
`...
`
`. 347/241
`5,047,789
`/1991 Kanayamaetal.
`9/1991 Gelbart oo. eceeeeceeeeees 347/239
`5,049,901
`2/1998 Venkateswar .....cceeeeeeee 358/298
`§,721,622
`
`OTHER PUBLICATIONS
`
`G. Toley et al.: “S7—6 Recent Advances in Actuated Mirror
`Array (AMA) Projector Development”; Aura Syss., Inc. El
`Segundo, USA. Daewoo Elect., Seoul, Korea.
`“Mirrors on a Chip”; IEEE Spectrum, Nov. 1993; pp. 27-31.
`“Digital Micromirror Device Imaging Bar for Hardcopy”;
`Nelsonet al.; Digital Imaging Venture Project Texas Instru-
`ments Inc., P.O. Box. 655474. M/S 440, Dallas Texas
`75265-5474; SPIE vol. 2413; pp. 58-65.
`“Micromirrors and Digital Processing”; Photonics Spectra;
`May 1995; pp. 118-124.
`
`Primary Examiner—N. Le
`Assistant Examiner—Lamson D. Nguyen
`Attorney, Agent, or Firm—Sughrue, Mion, Zinn, Macpeak
`& Seas, PLLC
`
`[57]
`
`ABSTRACT
`
`A color spatial light modulator has red, green, and blue
`micromirror arrays juxtaposed in parallel. Each micromirror
`array has a number of micromirrors each formed witha filter
`for reflecting specific color light. As data “1” is written to a
`memory cell of an SRAM,the micromirrortilts by +@ and
`enters a valid reflection state in which spotlight ts utilized.
`As data “0”is written, the micromirror tills by -0 and enters
`an invalid reflection state in which spot lightis not utilized.
`A data write control circuit converts image data into mirror
`drive data and writes it to SRAM. Three-color parallel line
`light beams generated bythe three-color micromirror arrays
`are projected by a projector lent onto color paper. A three-
`color imageis printed line sequentially on the color paper.
`
`N. Nishida: “Micro machines and optical techniques (2),
`Digital micromirror devices (DMD)andtheir applications to
`
`17 Claims, 11 Drawing Sheets
`
`10
`
`PCNA Ex. 1040
`U.S. Patent No. 9,955,551
`
`PCNA Ex. 1040
`U.S. Patent No. 9,955,551
`
`
`

`

`U.S. Patent
`
`Aug, 3, 1999
`
`Sheet 1 of 11
`
`5,933,183
`
`FIG. 1
`
`FIG. 2A
`
`FIG. 2B
`
`FIG. 2C
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`

`U.S. Patent
`
`Aug.3, 1999
`
`Sheet 2 of 11
`
`5,933,183
`
`FIG. 3
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`FIG. 4
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`

`

`U.S. Patent
`
`Aug.3, 1999
`
`Sheet 3 of 11
`
`5,933,183
`
`FIG
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`

`

`U.S. Patent
`
`Aug, 3, 1999
`
`Sheet 4 of 11
`
`5,933,183
`
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`U.S. Patent
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`Aug.3, 1999
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`Sheet 5 of 11
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`5,933,183
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`U.S. Patent
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`Aug.3, 1999
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`Sheet 6 of 11
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`Aug.3, 1999
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`Sheet 7 of 11
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`U.S. Patent
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`Aug.3, 1999
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`Sheet 8 of 11
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`5,933,183
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`U.S. Patent
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`Aug, 3, 1999
`
`Sheet 9 of 11
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`5,933,183
`
`FIG. 16
`
`
`
`20
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`

`

`U.S. Patent
`
`Aug.3, 1999
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`Sheet 10 of 11
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`5,933,183
`
`FIG. 17
`
`97
`
`
`
`

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`U.S. Patent
`
`Aug.3, 1999
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`Sheet 11 of 11
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`5,933,183
`
`FIG. 18
`
`113
`
`

`

`5,933,183
`
`1
`COLOR SPATIAL LIGHT MODULATOR AND
`COLOR PRINTER USING THE SAME
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`light
`invention relates to a color spatial
`The present
`modulator and a color printer using the same. More
`particularly,
`the invention relates to a color spatial
`light
`modulator having small size mirrors disposed in a line or
`matrix,
`for each which the light reflection direction is
`variable for projecting a specific color spot light, and to a
`color printer using such a color spatial light modulator for
`image formation.
`2. Description of the Related Art
`A spatial light modulator has a function of deflecting a
`propagation direction of incidentlight, and so it is used, for
`example, as an on/off controller of a laser optical system for
`controlling propagation of a laser beam. Conventionally, an
`ultrasonic light modulator has been used which deflects a
`laser beam by ultrasonic wave. Recently, a mirror type
`spatial
`light modulator has been proposed which has a
`number of small size mirrors (hereinafter called
`micromirrors),
`the tilt angle of each micromirror being
`changed to control deflection. Mirror type spatial
`light
`modulators include digital micromirror devices (DMD)
`which tilt each micromirror by electrostatic force, piezo-
`electric type drive micromirror devices (AMA) which tilt
`each micromirror by mechanical deformation of a fine
`piezoelectric element, and the like.
`For example, a digital micromirror device has a static
`RAM (SRAM)on each memorycell of which a micromirror
`capable of swinging is formed by semiconductor integration
`techniques. Mirror drive data of one bit, when written to
`each memory cell, tilts the micromirror in a positive direc-
`tion or in a negative direction to change the lightreflection
`direction. The principle and applications of such a digital
`micromirror device are described in a monthly magazine “O
`plus E”, October, 1994, pp. 90-94.
`It is another object of the present invention to provide a
`As one of the applications, this document describes a
`compact color printer simple in structure.
`sequential field type color video projector. In this color video
`In order to achieve the above and other objects, the color
`projector, ilumination light from a white light source passes
`spalial light modulator of this invention has at least one
`through a color filter disk and enters a digital micromirror
`micromirror array andafilter fixedly mounted in correspon-
`45
`device. The colorfilter disk has three sectors of red, green,
`dence with each micromurror of the micromirror array. Adye
`and bluefilters. The digital micromirror device has a number
`filter, an interference filter, or the like is used. A dyefilter is
`of micromirrors disposed in matrix. As “1” is written to a
`directly formed on a micromirror or on a transparent plate
`memory cell, the micromirror tilts by an angle +6 from a
`disposed above micromirrors. The dye filter converts white
`horizontal plane, and as “O”is written,it tilts by an angle -@.
`light into color light in a specific wavelength range, through
`If the redfilter is set in front of the white light source, red;
`absorption and transmission functions thereof. An interfer-
`imagedata of one frameis written to the digital micromirror
`encefilter is formed on each micromirror to reflect light in
`device. As the red image data of “1” is stored in a memory
`a specific wavelength range. Instead of a micromirror, a
`cell,
`this micromirror reflects the red light
`transmitted
`plate (microplate) without a mirror function may be used on
`which an interference filter is formed.
`throughthe red filter toward a projection lens, whereasas the
`red image data of “0”is stored, the micromirrortilts by the ,
`angle -6 and the red light
`is reflected toward a light
`absorption plate.
`The digital micromirror device generates a number of red
`spot lights depending on the tilt angle of each micromirror
`disposed in matrix. Onered light spot correspondsto one red
`pixel. A red imageof one frame constituted of these red light
`spots is projected via a projector lens onto a screen. The grey
`scale of a red image changes with a time period during
`whichthe tilt angle takes +9.
`Next, green image data is written to the digital micromir-
`ror device, and thereafter the green filter is set in front of the
`white light source. A green image of one frame generated by
`
`2
`the digital micromirror device is projected onto the screen.
`Thereafter, blue image data is written and a blue image of
`one frame is projected from the digital micromirror device
`onto the screen. While the color filter disk is rotated at high
`speed,
`image data of each color is written to the digital
`micromirror device synchronously with the timing of the
`setting of each color filter so that three color images are
`sequentially projected onto the screen at high speed and an
`image of full color synthesized on the screen can be
`observed.
`
`light modulator
`type spatial
`A conventional mirror
`requires a rotatable color filter disk in order to display or
`record a color image. This colorfilter disk complicates the
`structure of a video projector and makesthe projector bulky.
`Knowncolor printers for recording a color image on a
`photosensitive material include a CRT type, a laser type, a
`liquid crystal type, and the like. The CRT type colorprinter
`requires a large CRT and a complicated CRT drivercircuit.
`Thelaser type color printer basically performs line exposure
`so that the intensity of a laser beam is modulated in the unit
`of pixel. This takes a long time for intensity modulation.
`Since an exposure time of one pixel is short, a reciprocity
`law failure of photosensitive material may occur. Compen-
`sation for this is very cumbersome. The liquid crystal type
`color printer requiresa light source of high intensity because
`the transmittance of each pixel is small. Furthermore, since
`an aperture efficiency (vignetting factor) of each pixel is
`small, the image quality is not good.
`The micromirror device has advantages of a low light
`attenuation coefficient and a large aperture efficiency. It is
`therefore advantageousif the micromirror device is utilized
`in a color printer. However this color printer using the
`micromirror device uses a rotatable color filter disk and the
`structure is made complicated.
`SUMMARYOF THE INVENTION
`
`It is a principal object of the present invention to provide
`a color spatial light modulator capable of dispensing with a
`rotatable color filter disk.
`
`10
`
`15
`
`20
`
`°
`
`40
`
`According to a preferred embodiment of the invention,
`the color spatial light modulator has at least first to third
`micromirror arrays extending in parallel. The first to third
`micromirror arrays are provided with red, green, and blue
`filters, respectively. A plurality of micromirror arrays with
`the same color filters may be juxtaposed.
`According to another preferred embodiment of the
`invention, the color spatial light modulator has a plurality of
`micromirror arrays disposed in parallel, and micromirrors of
`the arrays arc disposed in matrix. The samecolor filter is
`provided for each micromirror. According to still another
`preferred embodimentof the invention, red, green, and blue
`color filters are formed on micromirrors in a mosaic pattern.
`
`60
`
`65
`
`

`

`5,933,183
`
`3
`Acolor printer of this invention has at least three micro-
`mirror arrays and red, green, and blue colorfilters fixedly
`disposed in correspondence with each micromirror array,
`and generates a red spotlight of one line, green spotlight of
`oneline, and blue spotlight of one line. Mirror drive means
`drives each micromirror array in accordance with corre-
`sponding red, blue, and green image data of one line.
`Three-color line light from the color spatial light modulator
`is projected onto photosensitive material by a projector
`optical system. Thefilter is directly formed on each micro-
`mirror or disposed on an input or output optical path of the
`micromirror.Instead of the filter, three color light sources for
`generating light of three primary colors maybe used.
`The color spatial light modulator of this invention uses a
`filter mounted on each micromirror or on a transparent plate
`of a package, for absorbing or reflecting color light in a
`specific wavelength range and allowing specific color light
`to travel. Therefore, a conventional rotary colorfilter plate
`is not necessary. Furthermore, a filter is formed on each
`micromirror or on a transparent plate for hermetically seal-
`ing a package. Therefore, manufacture is easy and manu-
`facturing costs can be reduced.
`The color printer of this invention uses a filter formed in
`correspondence with each micromurrorfor allowing travel of
`colorlight in a specific wavelength range. Therefore, a filler
`drive mechanism for inserting or retracting a three-color
`filter is not necessary. Therefore, the structure of the color
`printer can be simplified and made compact. If a filter
`switching mechanism is used, this switching speed is very
`slow as compared to a very fast displacement time of 20 us
`of a micromirror so that print time becomes long. However,
`since the filter is not inserted or retracted in this invention,
`a print time is not increased.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The above objects and advantagesof the present invention
`will become apparent from the following detailed descrip-
`tion of the preferred embodiments of the invention when
`read in conjunction with the accompanying drawings, in
`which:
`
`light
`
`FIG. 1 is a diagram illustrating a color spatial
`modulator of this invention;
`FIGS. 2A to 2C are diagramsillustrating the operation of
`a micromirror;
`FIG. 3 is a diagram showing a color spatial light modu-
`lator having a single micromirror array for each color;
`FIG. 4 is a diagram showing a color spatial light modu-
`lator having a plurality of micromirror arrays for each color;
`FIG. 5 is a diagram showing a blue spatial light modu-
`lator;
`FIG. 6 is a diagram showing a color spatial light modu-
`lator having micromirrors disposed in matrix;
`FIG. 7 is a diagram showing a color spatial light modu-
`lator having micromirrors of three primary colors disposed
`in a mosaic pattern;
`FIG. 8 is a plan view of a color spatial light modulator
`having a filter formed on a transparent plate of a package;
`FIG. 9 is a cross sectional view of the color spatial light
`modulator shown in FIG. 8;
`FIG. 10 is a schematic diagram of a color line printer of
`the invention;
`FIG. 11 showssignal waveformsillustrating a one line
`record operation;
`FIG. 12 is a block diagram showing an example of a data
`converter using a comparator;
`
`10
`
`15
`
`20
`
`-
`
`40
`
`45
`
`60
`
`65
`
`4
`FIG. 13 shows signal waveformsillustrating a one line
`record operation of the data converter shown in FIG. 12;
`FIG. 14 is a block diagram showing an example of a data
`converter using an LUT;
`FIG. 15 shows signal waveformsillustrating a one line
`record operation of the data converter shown in FIG. 14;
`FIG. 16 is a diagram illustrating a color printer using three
`color spatial light modulators;
`FIG. 17 is a diagram illustrating a color line printer with
`colorfilters inserted in optical paths; and
`FIG. 18 is a diagram illustrating a color line printer
`capable of recording both a color image and a monochrome
`image.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`FIG. 1 briefly showsa color spatial light modulator of this
`invention. In the color spatial light modulator 10, a filter is
`directly formed on each micromirror of a digital micromirror
`device. A plurality of micromirrors 2 are disposed in matrix.
`Each micromirror 2 is supported and is capable of swinging
`above a static RAM (SRAM) 4 at a post 3 formed at the
`central area of the memory cell. Each micromirror 2 is a
`square having a side length of, for example, 16 um, and ts
`made of a metal thin film such as conductive aluminum.
`Address electrodes 5a and 5b are formed on both sides of
`
`the post 3. The address electrodes 5a and 5b and the
`micromirror 2 constitute a capacitor. The micromirror 2 is
`tilted by static electricity charged between the address
`electrodes 5a and 5b and the micromurror 2. Specifically, one
`of the corners 2a and 25 on a diagonalline passing through
`the post 3 and address electrodes 5a and 56 tilts and contacts
`the silicon substrate on which SRAM 4 is formed. The
`corners on the other diagonal line are suspended bya pair of
`support posts via torsion hinges. Each constituent such as
`micromirror 2 and post 3 is fabricated by knowntransistor
`integration techniques.
`As shown in FIGS. 2A to 2C,a filter 6 is formed on the
`surface of each micromirror 2, and transmits one of red,
`green, and blue light while absorbing light
`in specific
`wavelength ranges. Such filters are not shown in FIG. 1.
`Each filter 6 is formed on the mirror surface by vapor
`deposition, transfer, adhesion, orthe like. Thefilter 6 may be
`an interference filter instead of using a dye filter. An inter-
`ference filter reflects light in a specific wavelength range by
`utilizing light
`interference of a multi-layer
`thin film.
`Therefore, in place of the micromirror 2, a metal thin film
`having a low reflectivity may be formed as a microplate.
`Obviously, a light absorption film may be formed on the
`micromirror and an interferencefilter is formed onthe light
`absorption film.
`Each micromirror 2 is disposed above each memorycell
`7 of SRAM 4. Each memory cell 7 is constituted of a
`flip-flop having at least two transistors. The transistors are
`connectedto the address electrodes 5a and 5b. Onetransistor
`
`of the flip-flop in an active state is ON and the other is OFF.
`Therefore, one of the address electrodes is, for example, +5
`V and the other is 0 V. The mirror drive data determines the
`electrode at +5 V.
`
`If the poweris OFF, the two transistors are OFFsothat the
`address electrodes 5a and 5b are not applied with any
`voltage and the micromirror is not applied with a bias
`voltage. Therefore, the micromirror is horizontal as shown
`in FIG. 2A.
`
`As mirror drive data “0”is written to the memorycell 7,
`the address electrode 5a has 0 V and the address electrode
`
`

`

`5,933,183
`
`5
`5b has +5 V. As a negativebias is applied to the micromirror
`2, the micromirror 2 tilts to the address electrode 5b side and
`its corner 2b contacts the silicon substrate, as shown in FIG.
`2B.
`
`As mirror drive data “1” is written to the memory cell 7,
`the address clectrode 5a has +5 V and the address clectrode
`
`10
`
`15
`
`5b has 0 V. As a negative bias is applied to the micromirror
`2, the micromirror 2 tilts to the address electrode 5a side and
`its corner 2a contacts the silicon substrate, as shown in FIG.
`2C. The micromirror 7 tilts therefore by +0 or by -0 in
`accordance with the mirror drive data value.
`The micromirror 2 has one horizontal state and two tilt
`states. The twotilt states are utilized for image formation. In
`one of the twotilt states, spot light travels from the micro-
`mirror 2 to form an image. For example, while the micro-
`mirror 2 takes +0, spot light from the micromirror 2 is
`guided to an image forming optical path. While the micro-
`mirror 2 takes -8, spot light is not needed sothatit is guided
`to an eliminating optical path. While the micromirror 2 takes
`+0, a valid reflection state (ON state) maintains in which -
`reflection light is utilized for image formation. While the
`micromirror 2 takes —0, an invalid reflection state (OFF
`state) maintains in which reflection light is notutilized for
`image formation. The tonal
`level of an image can be
`represented by changingthe time or occurrence frequency of *
`the valid reflection state of the micromirror 2.
`
`6
`blue filters disposed in line. In this example, eight blue
`micromirror arrays are formed and blue micromirrors are
`disposed in matrix. This blue spatial light modulator 24 is
`used for printing or displaying a blue image of one frame.
`Acolorspatial light modulator 26 shownin FIG.7 has red
`micromirrors 27 with redfilters, green micromirrors 28 with
`green filters, and blue micromirrors 29 with blue filters,
`respectively disposed in a mosaic pattern. This color spatial
`light modulator 20 of a mosaic pattern is used for forming
`an image of one frame althoughit has a low resolution.It is
`also used as a light adjuster (dimmer) of a photographic
`printer.
`A color spatial light modulator is packaged in order to
`prevent dust attachment to each micromirror or breakage of
`the modulator because of abutment of handsor objects. This
`package has a window at its upper surface,
`the window
`having a transparent plate fitted therein. Instead of forming
`a color filter on a micromirror, a color filter may be formed
`on the transparentplate. It is simpler to form colorfilters on
`the transparent plate than to form them on the micromirrors,
`so that manufacture is easy and cost can be reduced.
`TIGS. 8 and 9 show a color spatial light modulator 32
`having color filters formed on a transparent plate (cover
`glass). A package 33 is of a box shape with the upper portion
`being opened, and is madeofplastic or the like. A substrate
`34 formed with three micromirrorarrays like those shown in
`FIG. 3 is housed in the package 33. FIG. 9 shows three
`micromirrors 35 to 37 belonging to the three micromirror
`arrays.
`A transparent plate 40 is fixed to the package 33 at its
`upper opening to hermetically seal the inside of the package
`33. A red filter 41, a green filter 42, and a blue filter 43 of
`a stripe shape are formed on the transparent plate 40,
`corresponding in position to the three micromirror arrays.
`A mask 44 is formed on the transparent plate 40, sur-
`rounding the colorfilters 41 to 43. This mask 44 is formed
`by vapor deposition of black metal, adhesion of black shect,
`or coating of black paint. This mask 44 preventsflair or the
`like, by shielding illumination light incidentto the area other
`than the micromirrors and by shielding unnecessary reflec-
`tion light in the package 33.
`The color filters 41 to 43 and mask 44 may be formed on
`the transparent platc 40 on the inside thereof so that they are
`not stained or scratched.
`
`The colorspatial light modulator 32 shown in FIGS. 8 and
`9 correspondsto the color spatial light modulator 10 shown
`in FIG. 3. Other colorspatial light modulators corresponding
`to those shown in FIGS. 4 to 7 may also be manufactured.
`A color spatial light modulator has an image forming
`function so that it can be used for a color display device such
`as a color video projector and a color printer. The color
`spatial light modulator also has a function of adjusting three
`color components so that it can be used for a photographic
`printer. Applications to a color photographic printer may be
`a light adjuster (dimmer) for adjusting three color compo-
`nents of print
`light
`in accordance with the three color
`densities of a negative image, and an exposure controller for
`controlling red, green, and blue exposure amounts of color
`paper in accordance with the three color densities of a
`negative image.
`FIG. 10 showsa colorline printer. Infrared light contained
`in white light radiated from a white light source 50 is cut by
`an infrared light filter 51. A condenser lens 52 condenses
`white light toward a color spatial light modulator 10. A
`balance filter 53 performs shading correction so that the
`whole surface of the color spatial light modulator 10 is
`illuminated at a uniform illuminance.
`
`FIG. 3 shows an example of a color spatial light modu-
`lator. The color spatial light modulator 10 has a red micro-
`mirror array 11, a green micromirror array 12, and a blue
`micromiurrorarray 13, respectively disposed in parallel. Each
`micromirror array 11-13 has micromirrors which tilt by
`electrostatic force and are disposed in line at a predeter-
`mined pitch. Each micromirror array has 10 micromirrors in
`the drawing, but has a great numberthereof in actuality. A
`predetermined distance L may be provided between adjacent
`micromirror arrays.
`In the red micromirror array 11, a red filter indicated by
`R is formed on each micromirror. In the green micromirror
`array 12, a green filter indicated by G is formed on each
`micromirror. In the blue micromirror array 13, a blue filter
`indicated by B is formed on each micromirror. A micromir-
`ror array withoutfilters may be added for forming a mono-
`chrome image, in addition to the color micromirror arrays 11
`to 13.
`In a color printer using this color spatial
`light
`modulator, a photosensitive material such as color paper is
`intermittently fed by one line to perform line printing.
`FIG. 4 shows an example of a color spatial light modu-
`lator having a plurality of micromirror arrays for respective
`colors. The color spatial light modulator 15 has three rows;
`of red micromirror arrays 16a to 16c, three rows of green
`micromirror arrays 17a to 17c, and three rows of blue
`micromirror arrays 18a to 18c. With this color spatial light
`modulator 15, the same colorof three lines is recorded at the
`same time so that high speed printing is possible. In this ;
`case, color paper is intermittently fed by three lines. A
`distance of three lines may be provided between micromir-
`ror arrays of different colors.
`FIG. 5 shows an example of a blue spatial light modulator
`20 having one blue micromirror array 21. The blue micro-
`mirror array 21 actually has a great number of micromirrors.
`Forrecord or display of a full-color image, a red spatial light
`modulator, a green spatial light modulator, and a blue spatial
`light modulator are used in combination.
`FIG. 6 showsan area type blue spatial light modulator 24
`having a plurality of juxtaposed blue micromirror arrays.
`Each blue micromiurror array has blue micromirrors with
`
`40
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`45
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`60
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`65
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`5,933,183
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`8
`7
`57. Since the occurrence period of write timing signals is
`Light other than specific colors in white light incident
`halved sequentially, the six-bit image data is pulse-width
`upon the color spatial light modulator 10 is absorbed by a
`modulated so that the total time of valid reflection states
`filter. For example, in the case of a micromirror with a red
`changes with a magnitude of the image data value.
`filter, part of red light in white light is reflected at the surface
`After the lapse of time T1, the data write control circuit 72
`of the red filter, and the remaining red light is transmitted
`writes “Os” into SRAM4to clear it. At the same time or
`throughthe red filter, reflected by the micromirror, and again
`immediately after SRAM4is cleared, one line paper trans-
`transmitted through the red filter. In this manner, each
`port is executed in a time period of T2. Oneline record cycle
`micromirror with a red filter generates red spot light.
`is completed in the time periods of Tl and T2. The color
`The color spatial light modulator 10 has three micromirror
`paper 57 maybe transported continuously. In this case, three
`arrays 11 to 13 as shown in FIG. 3. The color spatial light
`color lines are recorded just after the color paper 57 is
`modulator 10 generates red, green, and blue line light
`transported by one line.
`respectively constituted of red, green, and blue spot light
`Next, the operation of the color line printer constructed as
`aligned in line. Each color line light extends in the width
`above will be described. Upon instruction of printing, the
`direction of color photosensitive material such as color
`controller 65 instructs the data write control circuit 72 to
`paper 57, and is constituted of P light spots where P is the
`clear the color spatial light modulator 10. ‘The data write
`number of micromirrors of each micromirror array 11-13.
`control circuit 72 writes mirror drive data “O” into all
`As the micromirrortilts by +9, it enters the valid reflection
`state and spotlight becomes incident uponthe color paper 57
`via a projector lens 56 to form one pixel. As the micromirror
`tilts by -@ or becomes horizontal,
`it enters the invalid
`reflection state and spot light becomes incident upona light
`absorption plate 55.
`Red, green, and blue three light lines generated by the
`color spatial light modulator 10 are projected in a magnified
`and consecutive state onto the color paper 57 by the pro-
`jector lens 56. The width of each line is MxL where M is a
`magnification factor of the projector lens and Lis a width of
`the micromirror array.
`Three light lines of an image whose color and density are
`an inversion of an image to be recorded on the color paper
`57 are incident upon the color absorption plate 55.
`Therefore, if color photosensitive material is disposed at the
`position of the light absorption plate 55 and a projector lens
`is disposedin front of the color photosensitive material, then
`an image whose color and density are an inversion of an
`image to be recorded on the color paper 57 can be formed
`one line after another. Reference numeral 58 represents a
`balance filter, and reference numeral 59 represents a mask.
`The color paper 57 is nipped with a transport roller pair
`60,
`intermittently pulled out of a supply roll 61 by a
`predetermined amount (MxL), andsent to a take-up roll 62.
`While the color paper 57 is stopped, three parallel light lincs
`are recorded at the same time on the color paper 57. A pulse
`motor 63 for rotating the transportroller pair 60 is controlled
`by a controller 65 via a driver 64.
`‘Three-color image data of one frame is stored in red,
`green, and blue image memories 68, 69, and 70, respec-
`tively. The three-color image data is read in a one-line shift
`state for each color and written to a line memory71.
`As shownin FIG. 11, a data write control circuit 72 reads
`oneline image data for each color fromthe line memory 71.
`Synchronously with a write timing signal from the controller
`71, the data write control circuit 72 sequentially writes as
`mirror drive data one bit after another, starting from the
`highest bit of each image data set, into memory cells 7 of the
`color spatial light modulator 10. First, synchronously with
`the first write timing signal, the highest bits of respective
`image data sets are sequentially written to SRAM 4. Next,
`synchronously with the second write timing signal,
`the
`second highest bits of respective image data sets are written.
`In this example shownin FIG. 11, image data is “101101”.
`In this case, six bits of the image data are written as the
`mirror drive data to the memory ccll 7 in response to six
`write timing signals during a time period of T1. If the mirror
`drive data is “1”, the micromirror enters the valid reflection
`state and reflected spot light is projected onto the color paper
`
`memory cells 7 of SRAM 4. Next, the controller 65 turns on
`the white light source 50 to illuminate the color spatial light
`modulator 10 with white light. In this case, since “0” has
`been written in cach memory ccll 7 of SRAM 4, cach
`micromirror tilts by -9 and has the invalid reflection state.
`Therefore, although specific color light of illumination light
`radiated from the white light source 50 is allowed to travel
`by a filter, the light is reflected toward the light absorption
`plate 55.
`The bluc micromirror array 13 of the color spatial light
`modulator 10 is positioned to the left of a print optical axis
`73, and the red micromirrorarray 11 is positionedto the right
`of the print optical axis 73. With this positioning, red line
`light of the red micromirrorarray 11 is projected on the color
`paper 57 on the upstream (left) side through the projector
`lens 56, and blueline light of the blue micromirror array 13
`is projected on the color paper 57 on the downstream (right)
`side. Therefore, green on the color paper 57 is shifted
`downstream by one line from red, and blue is shifted
`downstream by two lines from red. The controller 65 oper-
`ates to read red image data of the first line from the red
`image memory 68 and to write it to the line memory 71.
`Next, the controller 65 generates six write timing signals in
`the time period T1 at predetermined pitches and sends them
`to the data write control circuit 72.
`
`Upon reception of the first write liming signal, the data
`write control circuit 72 writes as the mirror drive data
`
`highest bits of six-bit red image data into SRAM 4. The
`highest bits of one line are written to memory cells of the red
`micromirror array 11.
`Each micromirror of the red micromirror array 11 enters
`the valid reflection state if the mirror drive data is “1”, fillers
`the incident white light to exit red light, reflects it as red spot
`ligh