Patent Publication Number: US-2005133698-A1

Title: Optical apparatus and image production apparatus

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to an optical apparatus and an image production apparatus.  
      An image forming apparatus such as a projector and a printer (refer to, for example, Japanese Patent Laid-Open No. 2003-140354, hereinafter referred to as Patent Document 1) wherein a flux of light from a one-dimensional image production apparatus is scanned by an optical scanning block and projected to an image forming block to form a two-dimensional image is disclosed in and known from, for example, Japanese Patent No. 3,401,250 (hereinafter referred to as Patent Document 2) and Japanese Patent No. 3,164,825 (hereinafter referred to as Patent Document 3). The one-dimensional image production apparatus disclosed in Patent Document 2 and Patent Document 3 includes an optical element wherein a plurality of diffraction grating-optical modulation elements (GLV: Grating Light Valve) are arranged in a one-dimensional array. In the following description, such an optical element as just mentioned is sometimes referred to as diffraction grating-optical modulation apparatus. Usually, the diffraction grating-optical modulation apparatus (optical element) further includes a light transmitting member made of a glass plate and opposed to a plurality of diffraction grating-optical modulation elements for transmitting incoming light incoming into the diffraction grating-optical modulation apparatus and outgoing light outgoing from the diffraction grating-optical modulation apparatus therethrough. The diffraction grating-optical modulation elements are produced applying a micromachine production technique and are formed from diffraction gratings of the reflection type. The diffraction grating-optical modulation elements have a light switching action and display an image by electrically controlling on/off (transmission/interception) of light. In particular, light emitted from the diffraction grating-optical modulation elements of the diffraction grating-optical modulation apparatus is scanned by a scanning mirror to obtain a two-dimensional image. Accordingly, to display a two-dimensional image formed from M×N (for example, 1,920×1,080) pixels, the diffraction grading-optical modulation apparatus should be formed from N (=1,080) diffraction grating-optical modulation elements. Further, for color display, three image production apparatus each including such a diffraction grating-optical modulation apparatus as just described should be used.  
       FIG. 8  schematically shows a diffraction grating-optical modulation apparatus including diffraction grating-optical modulation elements and particularly shows arrangement of lower electrode  22 , fixed electrodes  31 , movable electrodes  32  and so forth of the diffraction grating-optical modulation elements  21 .  FIG. 9A  is a schematic partial sectional view taken along line B-B of  FIG. 8  showing a fixed electrode  31  and so forth, and  FIGS. 9B and 10A  are schematic partial sectional views taken along line A-A of  FIG. 8  showing a movable electrode  32  and so forth. Further,  FIG. 10B  is a schematic partial sectional view taken along line C-C of  FIG. 8  showing a fixed electrode  31 , a movable electrode  32  and so forth. Here, the movable electrode  32  before it is displaced is shown in  FIG. 9B  and on the left side in  FIG. 10B , and the movable electrode  32  after it is displaced is shown in  FIG. 10A  and on the right side in  FIG. 10B . Further, in  FIG. 8 , slanting lines are applied to the lower electrode  22 , fixed electrodes  31  and movable electrodes  32  and support portions  23 ,  24 ,  25  and  26  to clearly indicate them.  
      Referring to FIGS.  8  to  10 B, a diffraction grating-optical modulation element  21  shown includes a lower electrode  22 , belt-shaped (ribbon-shaped) fixed electrodes  31  and belt-shaped (ribbon-shaped) movable electrodes  32 . The lower electrode  22  is formed on a support member  12 . Meanwhile, the fixed electrodes  31  are supported on the support portions  23  and  24  and extend above the lower electrode  22 . The movable electrodes  32  are supported on the support portions  25  and  26  and extend above the lower electrode  22  in a juxtaposed relationship with the fixed electrodes  31 . Each of the diffraction grating-optical modulation elements  21  is composed of three fixed electrodes  31  and three movable electrodes  32 . The three movable electrodes  32  are collectively connected to a control electrode connected to a connection terminal section not shown. Meanwhile, the three fixed electrodes  31  are collectively connected to a bias electrode. The bias electrode is common to the plurality of diffraction grating-optical modulation elements  21  and is grounded through a bias electrode terminal section not shown. Also the lower electrode  22  is common to the plurality of diffraction grating-optical modulation elements  21  and is grounded through a lower electrode terminal section not shown.  
      If a voltage is applied to any movable electrode  32  through the connection terminal section and the control electrode and another voltage is applied to the lower electrode  22  (actually the lower electrode  22  is in a grounded state), then electrostatic force (Coulomb force) is generated between the movable electrode  32  and the lower electrode  22 . The movable electrode  32  is displaced downwardly toward the lower electrode  22  by the electrostatic force. Based on such displacement of the movable electrode  32 , a diffraction grating of the reflection type is formed from the movable electrode  32  and the fixed electrode  31 .  
      Here, if the distance between adjacent ones of the fixed electrodes  31  is represented by d (refer to  FIG. 10B ), the wavelength of light (incident angle: θ i ) incoming to the movable electrode  32  and the fixed electrode  31  by λ and the diffraction angle by θ m , then the following expression is satisfied: 
 
 d [sin(θ i )−sin(θ m )]= m·λ 
 
 where m is the order and assumes the values 0, ±1, ±2, . . . . 
 
      Thus, where the difference Δh 1  (refer to  FIG. 10B ) in height between the top face of the movable electrode  32  and the top face of the fixed electrode  31  is λ/4, the diffracted light exhibits a maximum intensity.  
      The diffraction grating-optical modulation apparatus  11  is formed such that a plurality of diffraction grating-optical modulation elements  21  are formed on the surface of the support member  12 .  FIG. 11  shows a conceptive sectional view of the diffraction grating-optical modulation apparatus  11 . Referring to  FIG. 11 , the diffraction grating-optical modulation apparatus  11  further includes a light transmitting member  13  formed from a glass plate in the form of a flat plate. It is to be noted that, in  FIG. 11 , the diffraction grating-optical modulation elements are not shown. The support member  12  and the light transmitting member  13  are adhered to each other by a low-melting point metal material layer  14 . The distance (L) from the surface of the support member  12  to the light transmitting member  13  is approximately 0.1 mm.  
       FIG. 13  shows a conceptive partial sectional view of a conventional image production apparatus. Referring to  FIG. 13 , the conventional image production apparatus includes, in addition to the diffraction grating-optical modulation apparatus  11 , a mounting substrate  350  (more particularly, a printed circuit board formed, for example, from a glass epoxy copper-plated laminated plate) and a light source (not shown in  FIG. 13 ). It is to be noted that an assembly of the diffraction grating-optical modulation apparatus  11  and the mounting substrate  350  is hereinafter referred to sometimes as diffraction grading-optical modulation apparatus assembly. A circuit for processing a signal inputted from the outside for driving the diffraction grating-optical modulation apparatus  11  and other circuits are provided on the mounting substrate  350 . The support member  12  is attached to a face  350 A of the mounting substrate  350  by bonding agent  43 . The light source is formed as a laser light source which emits one of red light, green light and blue light which are the primaries of light.  
      Semiconductor chips  40  on which a circuit required to drive the diffraction grating-optical modulation apparatus  11  is formed are attached to the face  350 A of the mounting substrate  350  by bonding agent  44 . The diffraction grating-optical modulation apparatus  11  and semiconductor chips  40  and the semiconductor chips  40  and mounting substrate  350  are electrically connected, for example, by bonded wires. The diffraction grating-optical modulation apparatus  11  and the semiconductor chips  40  are surrounded by a framework member  41  and are embedded in a potting resin  42  to protect the bonded wires.  
       FIG. 12  shows a concept of the image forming apparatus. Referring to  FIG. 12 , the image forming apparatus includes three image production apparatus  101 R,  101 G and  101 B. The image production apparatus  101 R includes a diffraction grating-optical modulation apparatus assembly  102 R and a laser light source (red light emitting semiconductor laser)  100 R. The image production apparatus  101 G includes a diffraction grating-optical modulation apparatus assembly  102 G and a laser light source (green light emitting semiconductor laser)  100 G. The image production apparatus  101 B includes a diffraction grating-optical modulation apparatus assembly  102 B and a laser light source (blue light emitting semiconductor laser)  100 B. It is to be noted that a laser beam of red emitted from the laser light source (red light emitting semiconductor laser)  100 R is indicated by a broken line and a laser beam of green emitted from the laser light source (green light emitting semiconductor laser)  100 G is indicated by a solid line. Further, a laser beam of blue emitted from the laser light source (blue light emitting semiconductor laser)  100 B is indicated by an alternate long and short dash line. The image forming apparatus further includes condenser lenses (not shown) for condensing the laser beams emitted from the laser light sources  100 R,  100 G and  100 B and introducing the condensed laser beams into diffraction grating-optical modulation apparatus  103 R,  103 G and  103 B (each having a configuration and structure same as those of the diffraction grating-optical modulation apparatus  11 ). The image forming apparatus further includes an L-shaped prism  104  for combining the laser beams emitted from the diffraction grating-optical modulation apparatus  103 R,  103 G and  103 B into a single flux of light, and a lens  105  and a spatial filter  106  through which the combined flux of light of the primaries passes. The image forming apparatus further includes an image forming lens (not shown) for focusing the single flux of light having passed through the spatial filter  106  to form an image. The image forming apparatus further includes a scanning mirror (galvano mirror)  107  for scanning the single flux of light having passed through the image forming lens, and a screen  108  on which the light scanned by the scanning mirror  107  is projected. It is to be noted that, where a cylindrical lens is used for the condenser lenses, collimated beams of light condensed to a predetermined spot size in an X direction but collimated to a predetermined width in a Y direction can be introduced into the diffraction grating-optical modulation apparatus  103 R,  103 G and  103 B. The spatial filter  106  is disposed, for example, on the Fourier plane.  
      In the image forming apparatus having such a configuration as described above, in an inoperative state of a diffraction grating-optical modulation element  21  wherein the movable electrode  32  is in a state shown in  FIG. 9B  and on the left side of  FIG. 10B , light reflected by the top faces of the movable electrode  32  and the fixed electrode  31  is intercepted by the spatial filter  106 . On the other hand, in an operative state of the diffraction grating-optical modulation element  21  wherein the movable electrode  32  is in a state shown in  FIG. 10A  and on the right side of  FIG. 10B , ±first order (m=±1) diffracted light diffracted by the movable electrode  32  and the fixed electrode  31  passes through the spatial filter  106 . Where the image forming apparatus is configured in this manner, on/off of light to be projected on the screen  108  can be controlled. Further, the difference Δh 1  in height between the top face of the movable electrode  32  and the top face of the fixed electrode  31  can be varied by varying the voltage to be applied to the movable electrode  32 , and as a result, the intensity of the diffracted light can be varied to perform gradation control.  
      Since the movable electrode  32  is very small in size, a high resolution, a high speed switching operation and display of a wide bandwidth can be achieved with the diffraction grating-optical modulation apparatus. Further, since the diffraction grating-optical modulation apparatus operates with a low application voltage, it is anticipated to implement an image forming apparatus of a very small size. Further, since scanning is performed by the scanning mirror  107 , such an image forming apparatus as described above can represent a very smooth and natural image when compared with a popular two-dimensional image production apparatus such as a projection type display apparatus which uses a liquid crystal panel or the like. Besides, since semiconductor lasers for red, green and blue light of the primaries are used and the light beams of them are mixed, the image forming apparatus has such a superior display performance which cannot be achieved by conventional image forming apparatus in that an image of a very wide natural color regeneration range can be represented.  
      Where such a high luminance as 10 4  lumen is required for the diffraction grating-optical modulation apparatus  11  in such an application as a projector for a theater, the power of the laser beam illuminated upon the diffraction grating-optical modulation apparatus  11  has such a very high value as approximately 50 to 100 W. Accordingly, a great amount of heat is generated in the diffraction grating-optical modulation apparatus  11 , and the heat is transferred to the mounting substrate  350 , resulting in significant thermal expansion of the mounting substrate  350 . It is to be noted that the thermal expansion of the mounting substrate  350  formed from a printed circuit board formed from a glass epoxy copper-plated laminated plate is, for example, approximately 3.1×10 −6 /K. Further, the Young&#39;s modulus of the mounting substrate  350  formed from a printed circuit board formed from a glass epoxy copper-plated laminated plate is, for example, approximately 25 GPa, and the mounting substrate  350  is considered very flexible.  
      If a great amount of thermal expansion occurs with the mounting substrate  350 , then a displacement in position appears between the fixed electrodes  31  and the movable electrodes  32  which form the diffraction grating-optical modulation elements  21 . As described hereinabove with reference to  FIG. 12 , in the image forming apparatus, one pixel is formed and displayed from laser beams (diffracted light of laser beams of red, blue and green) diffracted from the three diffraction grating-optical modulation apparatus  103 R,  103 G and  103 B. Therefore, if a displacement in position appears between the fixed electrodes  31  and the movable electrodes  32  which form the diffraction grating-optical modulation elements  21 , then a displacement occurs among the diffracted lights of laser beams emitted from the diffraction grating-optical modulation apparatus  103 R,  103 G and  103 B for forming and displaying pixels. As a result, color blurring or the like occurs, and it is difficult to form a clean image. As reduction in size and enhancement of the resolution of a diffraction grating-optical modulation apparatus proceeds, the problem of such color blurring and so forth becomes further conspicuous.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide an optical apparatus having a configuration and structure by which, even if heat is generated with optical elements in a diffraction grating-optical modulation apparatus or the like, lights emitted from the optical elements are less likely to suffer from displacement therebetween.  
      According to the first aspect of the present invention, there is provided an optical apparatus, including: 
          an optical element;     a mounting substrate;     a support member; and     a cooling/heat radiating member;     the support member being attached to a first face of the mounting substrate;     the optical element being attached to a second face of the mounting substrate;     the cooling/heat radiating member being attached to the support member;     the optical element and the support member being thermally connected to each other by a heat transmission element provided in the inside of the mounting substrate;     the support member being made of a material having a thermal conductivity of 230 W/m·K or more.        

      According to the second aspect of the present invention, there is provided an optical apparatus, including: 
          an optical element;     a mounting substrate; and     a support member;     the mounting substrate having an opening formed therein;     the support member being attached to one face of the mounting substrate;     the optical element being attached to a portion of the support member which is exposed to the opening formed in the mounting substrate;     the support member being made of a material having a thermal conductivity of 230 W/·K or more.        

      According to the third aspect of the present invention, there is provided an optical apparatus, including: 
          an optical element;     a mounting substrate; and     a support member;     the support member being attached to one face of the mounting substrate in such a manner as to extend from an edge portion of the mounting substrate to the outer side of the mounting substrate;     the optical member being attached to the portion of the support member which extends to the outer side of the mounting substrate;     the support member being made of a material having a thermal conductivity of 230 W/m·K or more.        

      According to the fourth aspect of the present invention, there is provided an image production apparatus, including: 
          a light source; and     an optical apparatus including an optical element for emitting light incoming from the light source, a mounting substrate, a support member, and a cooling/heat radiating member;     the support member being attached to a first face of the mounting substrate;     the optical element being attached to a second face of the mounting substrate;     the cooling/heat radiating member being attached to the support member;     the optical element and the support member being thermally connected to each other by a heat transmission element provided in the inside of the mounting substrate;     the support member being made of a material having a thermal conductivity of 230 W/m·K or more.        

      According to the fifth aspect of the present invention, there is provided an image production apparatus, including: 
          a light source; and     an optical apparatus including an optical element for emitting light incoming from the light source, a mounting substrate, and a support member;     the mounting substrate having an opening formed therein;     the support member being attached to one face of the mounting substrate;     the optical element being attached to a portion of the support member which is exposed to the opening formed in the mounting substrate;     the support member being made of a material having a thermal conductivity of 230 W/m·K or more.        

      According to the sixth aspect of the present invention, there is provided an image production apparatus, including: 
          a light source; and     an optical apparatus including an optical element for emitting light incoming from the light source, a mounting substrate, and a support member;     the support member being attached to one face of the mounting substrate in such a manner as to extend from an edge portion of the mounting substrate to the outer side of the mounting substrate;     the optical member being attached to the portion of the support member which extends to the outer side of the mounting substrate;     the support member being made of a material having a thermal conductivity of 230 W/m·K or more.        

      In the optical apparatus and the image production apparatus according to the first mode of the present invention, the optical element and the support member are thermally connected to each other by the heat transmission element provided in the inside of the mounting substrate. More particularly, the thermal connection is established such that the optical element and one end of the heat transmission element contact directly or indirectly with each other and the support member and the other end of the heat transmission element directly or indirectly contact with each other. Where the area of the portion of the optical element attached to the second face of the mounting substrate (that is, the area of the portion of the optical element which directly or indirectly contacts with the second face of the mounting substrate) is represented by S 0  and the sectional area of the heat transmission element for thermally connecting the optical element and the support member to each other along a plane parallel to the surface of the mounting substrate is represented by S 1  (where a plurality of such heat transmission elements are involved, the total area of the sectional areas of the transmission elements is represented by S 1 ), preferably the areas S 0  and S 1  satisfy a relationship of 0.01×S 0 ≦S 1 ≦0.5×S 0 .  
      In the optical apparatus and the image production apparatus according to the second mode of the present invention, the optical element is attached to the portion of the support member which is exposed to the opening formed in the mounting substrate. The surface of the portion of the support member 
          (1) may be substantially in level with the one face of the mounting substrate,     (2) may be positioned in the inside of the opening formed in the mounting substrate,     (3) may be substantially in level with the other face of the mounting substrate, or     (4) may project from the other face of the mounting substrate.        

      It is to be noted that, in the case of any of (2) to (4), the portion of the support member which is positioned in the inside of the opening formed in the mounting substrate may sometimes be hereinafter referred to as support member projection.  
      In the optical apparatus and the image production apparatus according to the first mode of the present invention, the heat transmission element may be formed from a via hole for heat transmission formed in the inside of the mounting substrate. The optical apparatus may further include a semiconductor chip including a circuit necessary to drive the optical element, the semiconductor chip being attached to the second face of the mounting substrate. The via hole for heat transmission may be structured such that a through-hole formed in the inside of the mounting substrate is filled up with a material (for example, copper or silver) having a high heat conductivity. Also in the optical apparatus and the image production apparatus according to the second or third mode of the present invention, where a semiconductor chip including a circuit necessary to drive the optical element is attached to the other face of the mounting substrate, preferably the semiconductor chip and the support member are thermally connected to each other by a heat transmission element provided in the inside of the mounting substrate. Further preferably, the heat transmission element is formed from a via hole for heat transmission formed in the inside of the mounting substrate. Preferably, the via hole for heat transmission is configured such that it contacts at one end thereof directly or indirectly with the optical element and contacts at the other end thereof directly or indirectly with the support member. Further, preferably another via hole for heat transmission is configured such that it contacts at one end thereof directly or indirectly with the semiconductor chip and contacts at the other end thereof directly or indirectly with the support member.  
      In the optical apparatus and the image production apparatus according to the second mode of the present invention, the optical apparatus may further include a cooling/heat radiating member attached to the support member. The optical apparatus may further include a semiconductor chip including a circuit necessary to drive the optical element, the semiconductor chip being attached to the portion of the support member which is exposed to the opening formed in the mounting substrate.  
      In the optical apparatus and the image production apparatus according to the third mode of the present invention, the optical apparatus may further include a cooling/heat radiating member attached to the support member. The optical apparatus may further include a semiconductor chip including a circuit necessary to drive the optical element, the semiconductor chip being attached to the portion (which is hereinafter referred to sometimes as support member projection) of the support member which extends to the outer side of the mounting substrate.  
      As the circuit necessary to drive the optical element, for example, a 10- or 12-bit driver and a digital-analog converter (DAC) can be listed.  
      While, in the optical apparatus and the image production apparatus according to the first to third modes of the present invention, the support member is made of a material having a thermal conductivity of 230 W/m·K or more, the upper limit to the thermal conductivity of the support member may essentially be an arbitrary value. Here, preferably the support member is made of aluminum (Al), copper (Cu), a beryllium copper alloy, silver or gold. The thermal conductivities of the materials mentioned are listed in Table 1 hereinbelow. Alternatively, the support member is preferably made of a material of at least two materials selected from a group consisting of the materials mentioned. In this instance, a structure wherein the support member projection made of a certain material and the portion of the support member other than the support member projection made of another material are adhered to each other can be used. It is to be noted that the values of the thermal conductivity given below are those at 0° C.  
                       TABLE 1                                   Thermal conductivity           (W/m · K)                                                    Al   236           Cu   403           Beryllium copper   230           Silver   428           Gold   319                      
 
      In the optical apparatus and the image production apparatus of the first to third modes of the present invention, the mounting substrate can be formed from a printed circuit board. As the printed circuit board, a rigid printed circuit board, a multilayer rigid printed circuit board and a multilayer flex rigid printed circuit board which have wiring lines formed on one or two faces thereof, a metal core printed circuit board and a multilayer metal core printed circuit board which have wiring lines formed on one or two faces thereof, and a metal base printed circuit board, a multilayer metal base printed circuit board, a buildup multilayer printed circuit board and a ceramics circuit board which have wiring lines formed on one or two faces thereof can be listed. The various printed circuit boards can be produced using a conventional production method. Such circuits may be formed by a subtractive method including a panel plating method and a pattern plating method or by an additive method such as a semi additive method or a full additive method. The configuration of a base member which forms the printed circuit board is essentially arbitrary, and the following can be exemplified: combinations of paper/phenol resin, paper/epoxy resin, glass fabric/epoxy resin, glass non-woven fabric/epoxy resin, glass fabric/glass non-woven fabric/epoxy resin, synthetic fiber/epoxy resin, glass fabric/polyimide resin, glass fabric/modified polyimide resin, glass fabric/epoxy modified polyimide resin, glass fiber/bismaleimide/triazine/epoxy resin, glass fabric/fluorocarbon resin, glass fabric/PPO (polyphenylene oxide) resin, and glass fabric/PPE (polyphenylene ether).  
      In the optical apparatus according to the first to third modes of the present invention, a diffraction grating-optical modulation apparatus, a semiconductor laser, a light emitting diode and a digital micromirror device (DMD) can be listed as the optical element. Meanwhile, in the image production apparatus according to the first to third modes of the present invention, a diffraction grating-optical modulation apparatus can be listed as the optical element. Here, the diffraction grating-optical modulation apparatus may particularly be configured such that it includes a lower electrode, a belt-shaped fixed electrode supported above the lower electrode, and a belt-shaped movable electrode supported above the lower electrode in a juxtaposed relationship with the fixed electrode, a plurality of diffraction grating-optical modulation elements each of which includes a diffraction grating formed from the movable electrode and the fixed electrode as the movable electrode is displaced toward the lower electrode by electrostatic force generated through application of voltages to the movable electrode and the lower electrode and acting between the movable electrode and the lower electrode being formed on a surface of the support member.  
      It is to be noted that preferably the diffraction grating-optical modulation apparatus further includes a light transmitting member disposed in an opposing relationship to the fixed electrodes and the movable electrodes for transmitting therethrough incoming light which is to come into the fixed electrodes and the movable electrodes and outgoing light which goes out from the fixed electrodes and the movable electrodes.  
      The fixed electrodes and the movable electrodes which form the diffraction grating-optical modulation apparatus can be produced applying, for example, a micromachine technique. The diffraction gratings formed from the movable electrodes and the fixed electrodes act as diffraction gratings of the reflection type.  
      A silicon semiconductor substrate can be exemplified as a material for forming the support member in the diffraction grating-optical modulation apparatus.  
      As a material for forming the lower electrode and the bias electrodes of the diffraction grating-optical modulation apparatus, at least one metal selected from a group consisting of aluminum (Al), titanium (Ti), gold (Au), silver (Ag), tungsten (W), niobium (Nb), tantalum (Ta), molybdenum (Mo), chromium (Cr), copper (Cu), nickel (Ni), cobalt (Co), zirconium (Zr), iron (Fe), platinum (Pt) and zinc (Zn); an alloy or a compound which contains any of the metallic elements mentioned (for example, a nitride such as TiN or a silicide such as WSi 2 , MoSi 2 , TiSi 2 , or TaSi 2 ); a semiconductor such as silicon (Si) and a conductive metal oxide such as ITO (indium tin oxide), indium oxide or zinc oxide can be exemplified. For production of the lower electrode or the bias electrodes, a known thin film formation method such as a CVD method, a sputtering method, a vapor deposition method, a liftoff method, an ion plating method, an electrolytic plating method, an electroless plating method, a screen printing method, a laser abrasion method, or a sol-gel method may be used to form a thin film of any of the materials mentioned above on the surface of the support member.  
      Further, the fixed electrodes and the movable electrodes of the diffraction grating-optical modulation elements preferably have a two-layer structure of a light reflecting layer (upper layer) and a dielectric material layer (lower layer). In particular, the two-layer structure may be, for example, a laminated structure of an aluminum layer (upper layer) and a SiN layer (lower layer), that of an aluminum layer (upper layer) and a SiO 2  layer (lower layer), that of an aluminum layer (upper layer) to which Si is added and a SiN layer (lower layer), that of an aluminum layer (upper layer and alloy layer of aluminum/copper) to which Cu is added and a SiN layer (lower layer) (as a rate of addition, 0.1 weight % to 5 weight % can be exemplified: this applies similarly in the following description), that of an aluminum layer (upper layer) to which Cu is added and a SiO 2  layer (lower layer), that of a titanium oxide layer (upper layer) and a SiN layer (lower layer), or that of a titanium oxide layer (upper layer) and a SiO 2  layer (lower layer). It is to be noted that the lower layer may have a two-layer configuration of a SiO 2  layer and a SiN layer.  
      Further, in the diffraction grating-optical modulation elements, supporting portions for supporting the fixed electrodes are preferably formed from extensions of the fixed electrodes, and supporting portions for supporting the movable electrodes are preferably formed from extensions of the movable electrodes.  
      In each of the diffraction grating-optical modulation elements, as the difference Δh 0  in height between the top face of the lower electrode and the top face of the fixed electrode, 3.0×10 −7  (m) to 1.5×10 −6  (m), preferably 4.5×10 −7  (m) to 1.2×10 −6  (m), can be exemplified. Further, the difference in height between the top face of the movable electrode and the top face of the fixed electrode when the diffraction grating-optical modulation element is inoperative preferably is as proximate as possible to zero. Furthermore, the maximum value Δh 1-MAX  of the difference Δh 1  (amount of the downward displacement of the movable electrode) in height between the top face of the movable electrode and the top face of the fixed electrode when the diffraction grating-optical modulation element is operative preferably satisfies 
 
Δ/4 ≦Δh   1-MAX  
 
 where the wavelength of incoming light to the diffraction grating-optical modulation element or the diffraction grating-optical modulation apparatus is represented by λ. Further, the relationship between Δh 1-MAX  and Δh 0  preferably satisfies 
 
Δ h   1-MAX ≦(Δh 0 /3) 
 
 It is to be noted that the difference Δh 1  (amount of the downward displacement of the movable electrode) in height between the top face of the movable electrode and the top face of the fixed electrode can be varied by varying the voltage to be applied to the movable electrode. Since this can vary the intensity of the diffracted light, gradation control can be performed. 
 
      Further, in the diffraction grating-optical modulation elements, the distance d between adjacent ones of the fixed electrodes preferably is, but is not limited to, 1×10 −6  (m) to 2×10 −5  (m), and more preferably 2×10 −6  (m) to 1×1 −5  (m). Further, the gap SP existing between any fixed electrode and an adjacent movable electrode (both of a gap within one diffraction grating-optical modulation element and a gap between adjacent ones of the diffraction grating-optical modulation elements) preferably is, but is not limited to, 1×10 −7  (m) to 2×10 −6  (m), and more preferably 2×10 −7  (m) to 5×10 −7  (m). Further, the width W F  of the fixed electrodes is, but is not limited to, 1×10 −6  (m) to 1×10 −5  (m), and more preferably 2×10 −6  (m) to 5×10 −6  (m) Furthermore, the effective length L F  of the fixed electrodes is, but is not limited to, 2×10 −5  (m) to 5×10 −4  (m), and more preferably 1×10 −4  (m) to 3×10 −4  (m) Meanwhile, the width W M  of the movable electrodes is, but is not limited to, 1×10 −6  (m) to 1×10 −5  (m), and more preferably 2×10 −6  (m) to 5×10 −6  (m). Further preferably, the width W M  of the movable electrodes is equal to the width W F  of the fixed electrodes. Further, the effective length L M  of the movable electrodes preferably is, but is not limited to, 2×10 −5  (m) to 5×10 −4  (m), and more particularly 1×10 −4  (m) to 3×10 −4  (m). It is to be noted that the effective length L F  of the fixed electrodes and the effective length L M  of the movable electrodes signify the lengths of a portion of any fixed electrode and a portion of any movable electrode between supporting portions thereof in the configuration wherein each of the fixed electrode and the movable electrode is supported by the supporting portions.  
      Further, in the diffraction grating-optical modulation apparatus, the numbers of fixed electrodes and movable electrodes which form one diffraction grating-optical modulation element are not particularly limited although, where one fixed electrode and one movable electrode are regarded as a set, at least only one set is required. However, the number of such sets may be three in the maximum. Further, as the arrangement of a plurality of diffraction grating-optical modulation elements in the diffraction grating-optical modulation apparatus, they may be arranged in a one-dimensional array. In particular, the fixed electrodes and the movable electrodes which form the plurality of diffraction grating-optical modulation elements may be juxtaposed along a direction perpendicular to the axial direction of the fixed electrodes and the movable electrodes. The number of the diffraction grating-optical modulation elements may be determined based on the number of pixels required for the optical apparatus or the image production apparatus.  
      As a material for forming connection terminal sections of the diffraction grating-optical modulation apparatus for establishing electric connection to an external circuit and control electrodes for electrically connecting the connection terminal sections and the movable electrodes to each other, such materials used for the lower electrode and the bias electrodes as mentioned hereinabove can be used. Also the method of forming the connection terminal sections or the control electrodes may be a method similar to the method of forming the lower electrode and the bias electrodes described above. It is to be noted that the lower electrode, bias electrodes, connection terminal sections and control electrodes may be formed simultaneously, or the four different kinds of electrodes may be formed simultaneously in an arbitrary combination. Further, the film thickness of the electrodes may be made thicker separately.  
      The light transmitting member may be formed from a glass plate or a plastics plate, for example, a plate made of polymethyl methacrylate (PMMA) or polycarbonate (PC), but is preferably formed from a glass plate.  
      In the diffraction grating-optical modulation elements, the top face of each movable electrode and the top face of each fixed electrode may be in parallel to the top face of the lower electrode, or may be inclined by a blaze angle θ D  with respect to the top face of the lower electrode to form the diffraction grating-optical modulation elements as those of the blaze type so that, for example, only +first order diffracted light may be emitted. Where the diffraction grating-optical modulation elements of the blaze type are employed, an image can be displayed with a high diffraction efficiency of, for example, 60% or more. In applications to image forming apparatus such as a projector, the elements of the blaze type has the smooth response characteristic in the range between the dark level and the middle gradation to the applied voltage. It is also preferable to adopt diffraction grating-optical modulation elements of the blaze type by which image display of high gradations can be achieved readily.  
      In the optical apparatus and the image production apparatus according to the present invention, a heat sink, a Peltier device, a cooling apparatus which circulates water or coolant for cooling and a fan for forced blasting can be used as the cooling/heat radiating member.  
      Attachment of the support member to the first or one face of the mounting substrate in the optical apparatus and the image production apparatus according to the present invention, attachment of the optical element to the second or other face of the mounting substrate in the optical apparatus and the image production apparatus according to the first mode of the present invention, and attachment of the optical element to the support member in the optical apparatus and the image production apparatus according to the second or third mode of the present invention may be performed by a method which uses a bonding agent (for example, a method of applying a bonding agent of the thermosetting type and then heating the bonding agent to effect joining or adhesion). Meanwhile, attachment of the cooling/heat radiating member to the support member may be performed using screws or using a bonding agent (for example, a method of applying an ultraviolet curing resin and then illuminating ultraviolet rays on the resin to effect joining or adhesion).  
      In the image production apparatus according to the first to third modes of the present invention, a semiconductor laser can be used as the light source.  
      Excessive heat generated when light (laser beam) is illuminated on an optical element provided, for example, in a diffraction grating-optical modulation apparatus has a bad influence on the accuracy in position of a component of the optical element (for example, a diffraction grating-optical modulation element on a support member). Therefore, it is necessary to take a sufficient countermeasure against the heat. In the optical apparatus and the image production apparatus according to the first to third modes of the present invention, the support member is made of a material having a thermal conductivity of 230 W/m·K or more so that heat generated when light (laser beam) is illuminated upon the optical element (for example, the diffraction grating-optical modulation apparatus) is radiated through the support member. Consequently, the components of the optical element can be prevented from being influenced by the heat. Therefore, the problems of color blurring and so forth can be eliminated, and further reduction in size, further enhancement in performance, further increase in resolution and further improvement of the picture quality can be achieved by the image production apparatus. Further, the stability in operation of the optical element, optical apparatus and image production apparatus can be raised and the life of them can be increased.  
      Further, since heat generated when light (laser beam) is illuminated on the optical element is radiated through the support member, occurrence of a problem arising from a temperature gradient which is caused by a temperature rise of the optical element (for example, appearance of a void or hillock on the fixed electrodes or the movable electrodes) can be suppressed. Consequently, the durability of the optical element can be improved, and increase of the life of the optical element can be anticipated. It is to be noted that, where appearance of a void or hillock cannot be suppressed, there is the possibility that it may cause deterioration of the dark level, and in the worst case, to electric disconnection, malfunction or the like.  
      In the optical apparatus or the image production apparatus according to the second mode of the present invention, since the opening is provided in the mounting substrate and the optical element is attached to the portion of the support member which is exposed in the opening provided in the mounting substrate, not only simplification in structure can be anticipated, but also the degree of freedom in design is high.  
      Where a semiconductor chip on which a circuit necessary to drive the optical element is provided is attached to the support member, radiation of heat from and cooling of the semiconductor chip can be performed efficiently and besides a wiring process (wire bonding) is facilitated, which contributes to improvement in workability.  
      The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements denoted by like reference symbols. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1A  is a schematic partial sectional view of a diffraction grating-optical modulation apparatus assembly as an optical apparatus of an embodiment 1 of the present invention;  
       FIG. 1B  is a schematic partial sectional view of a diffraction grating-optical modulation apparatus assembly as an optical apparatus as an embodiment 2 of the present invention;  
       FIG. 2A  is a schematic partial sectional view of a diffraction grating-optical modulation apparatus assembly as an optical apparatus of an embodiment 3 of the present invention;  
       FIG. 2B  is a schematic partial sectional view of a diffraction grating-optical modulation apparatus assembly as an optical apparatus according to a modification to the embodiment 2 of the present invention;  
       FIG. 3A  is a schematic partial sectional view of a diffraction grating-optical modulation apparatus assembly as an optical apparatus of an embodiment 4 of the present invention;  
       FIG. 3B  is a schematic partial plan view of a mounting substrate shown in  FIG. 3A ;  
       FIG. 4  is a schematic bottom plan view of the diffraction grating-optical modulation apparatus assembly as the optical apparatus of the embodiment 1 of the present invention;  
       FIG. 5A  is a schematic partial sectional view of a mounting board in the diffraction grating-optical modulation apparatus assembly as the optical apparatus of the embodiment 2 of the present invention;  
       FIG. 5B  is a schematic partial perspective view of the mounting board shown in  FIG. 5A  and a supporting member;  
       FIGS. 6A and 6B  are schematic partial plan views of the mounting boards in the diffraction grating-optical modulation apparatus assembly as the optical apparatus of the embodiment 2 of the present invention and a modification to the diffraction grating-optical modulation apparatus assembly, respectively;  
       FIGS. 7A and 7B  are schematic partial plan views of modifications to the mounting boards in the diffraction grating-optical modulation apparatus assembly as the optical apparatus of the embodiment 3 of the present invention and the modification to the diffraction grating-optical modulation apparatus assembly, respectively;  
       FIG. 8  is a view schematically showing arrangement of a lower electrode, fixed electrodes and movable electrodes which form a diffraction grating-optical modulation element;  
       FIG. 9A  is a schematic sectional view taken along line B-B of  FIG. 8  showing a fixed electrode and so forth;  
       FIG. 9B  is a schematic sectional view taken along line A-A of  FIG. 8  showing a movable electrode and so forth where the diffraction grating-optical modulation element is in an inoperative state;  
       FIG. 10A  is a schematic sectional view taken along line A-A of  FIG. 8  showing the movable electrode and so forth where the diffraction grating-optical modulation element is in an operative state;  
       FIG. 10B  is a schematic sectional view taken along line C-C of  FIG. 8  showing a fixed electrode, a movable electrode and so forth;  
       FIG. 11  is a conceptive sectional view showing part of a diffraction grating-optical modulation apparatus assembly;  
       FIG. 12  is a conceptive view of an image forming apparatus wherein three diffraction grating-optical modulation apparatus assemblies are combined; and  
       FIG. 13  is a schematic partial sectional view of a conventional diffraction grating-optical modulation apparatus assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Before different embodiments of the present invention are described, a diffraction grating-optical modulation apparatus and a diffraction grating-optical modulation element which are employed commonly in the embodiments are described.  
      Referring to  FIGS. 1A  to  7 B as well as FIGS.  8  to  13 , the diffraction grating-optical modulation apparatus  11  used in the present invention includes a support member  12  and a plurality of (for example, 1,080) diffraction grating-optical modulation elements  21  formed on the surface of the support member  12  similarly to those of  FIGS. 8, 9A ,  9 B,  10 A and  10 B. The diffraction grating-optical modulation apparatus  11  further includes a light transmitting member  13  formed from a glass plate. The diffraction grating-optical modulation elements  21  include a lower electrode  22 , fixed electrodes  31  and movable electrodes  32 . A light transmitting member  13  is disposed in an opposing relationship to the fixed electrodes  31  and the movable electrodes  32  and transmits therethrough incoming light which is to come into the fixed electrodes  31  and the movable electrodes  32  and outgoing light which goes out from the fixed electrodes  31  and the movable electrodes  32 .  
      The lower electrode  22  is made of polycrystalline silicon doped with an impurity and is formed on the surface of the support member  12  formed from a silicon semiconductor substrate. It is to be noted that a protective insulating film (not shown) made of SiO 2  is formed on the surface of the lower electrode  22  so that the lower electrode  22  may not be damaged when the fixed electrodes  31  and the movable electrodes  32  are formed. The belt-shaped (ribbon-shaped) fixed electrodes  31  are supported on and extend above the lower electrode  22  and are juxtaposed with the fixed electrodes  31 , and particularly are supported by support portions  25  and  26  which are extensions of the movable electrodes  32 . The fixed electrodes  31  and the movable electrodes  32  have a laminated structure (rate of addition of Cu: 0.5 weight. %) of a light reflecting layer (upper layer) made of aluminum to which Cu is added and a dielectric material layer (lower layer) made of SiN. It is to be noted that, in the figures, the fixed electrodes  31  and the movable electrodes  32  are represented in one layer.  
      A space defined by the diffraction grating-optical modulation apparatus  11  and the light transmitting member  13  is kept in an airtight state. Hydrogen gas, helium gas, nitrogen gas or mixed gas of them is enclosed in the space. This suppresses deterioration of the fixed electrodes  31  and the movable electrodes  32  arising from a temperature gradient caused by a temperature rise of the diffraction grating-optical modulation elements upon operation thereby to achieve improvement in durability and reliability.  
      The support member  12  and the light transmitting member  13  are joined together by a low-melting point metal material layer  14 . The low-melting point metal material layer  14  may be formed at desired locations of a peripheral edge portion of the surface of the support member  12  and a peripheral edge portion of the light transmitting member  13 . The layer  14  may be formed using a vacuum thin film forming technique such as vapor deposition, sputtering or ion plating. Under certain circumstances, a wire member or a foil member made of a metal material having a low melting point may be placed on or applied to desired locations of the support member  12  and so forth. The junction with the low-melting point metal material layer  14  is performed particularly by heating the low-melting point metal material layer  14 . Specifically, heating of the low-melting point metal material layer  14  can be performed by a known heating method such as heating using a lamp, a laser, a furnace or the like.  
      The low-melting point metal material layer  14  may be made of a low-melting point metal material having a melting point of approximately 120 to 400° C. As such low-melting point metal material, a low-melting point alloy of the tin-gold type such as Au 80 Sn 20  (melting point 260 to 320° C.) can be listed. Also, In (Indium: melting point 157° C.); high temperature solders of the tin (Sn) type such as Sn 80 Ag 20  (melting point 220 to 370° C.) and Sn 95 Cu 5  (melting point 227 to 370° C.); high temperature solders of the lead (Pb) such as Pb 97.5 Ag 25  (melting point 304° C.), Pb 94.5 Ag 5.5  (melting point 304 to 365° C.) and Pb 97.5 Ag 1.5 Sn 1.0  (melting point 309° C.); high temperature solders of the zinc (Zn) type such as Zn 95 Al 5  (melting point 380° C.); standard solders of the tin-lead type such as Sn 5 Pb 95  (melting point 300 to 314° C.) and Sn 2 Pb 98  (melting point 316 to 322° C.); and solder materials such as Au 88 Ga 12  (melting point 381° C.) may be used.  
      The arrangement of the plurality of diffraction grating-optical modulation elements  21  in the diffraction grating-optical modulation apparatus  11  is a one-dimensional array. More particularly, the fixed electrodes  31  and the movable electrodes  32  which form the plurality of (for example, 1,080) diffraction grating-optical modulation elements  21  are juxtaposed along a direction (Y direction) perpendicular to the axial direction (X direction) of the fixed electrodes  31  and the movable electrodes  32 . The total number of the fixed electrodes  31  and the movable electrodes  32  is, for example, 1,080×6.  
      It is to be noted that connection terminal sections (not shown) are provided for electric connection to semiconductor chips  40  on which, for example, a circuit necessary to drive the diffraction grating-optical modulation apparatus  11  is provided such that it is exposed to the outside, and are electrically connected to the movable electrodes  32 . More particularly, each of the diffraction grating-optical modulation elements  21  is composed of three fixed electrodes  31  and three movable electrodes  32 . The three movable electrodes  32  are collectively connected to a single control electrode, which is connected to a corresponding one of the connection terminal sections. Meanwhile, the three fixed electrodes  31  are collectively connected to a bias electrode, which is provided commonly to the plurality of diffraction grating-optical modulation elements  21 . The bias electrode is connected to the semiconductor chips  40  through a bias electrode terminal portion (not shown), which is an extension of the bias electrode, and is grounded. Also the lower electrode  22  is common to the plurality of diffraction grating-optical modulation elements  21 . The lower electrode  22  is connected to the semiconductor chips  40  through a lower electrode terminal portion (not shown), which is an extension of the lower electrode  22 , and is grounded.  
      The connection terminal sections, lower electrode terminal section and bias electrode terminal section (not shown) are provided in a region of the support member  12  on the outer side with respect to the low-melting point metal material layer  14  (refer to  FIG. 11 ). Wiring lines for connecting the terminal sections mentioned and various electrodes (for example, control electrodes, bias electrodes and so forth) have a structure which prevents short-circuiting of the wiring lines by the low-melting point metal material layer  14  (for example, the control electrodes and the bias electrodes are coated with an insulating material layer).  
      If a voltage is applied to any of the movable electrodes  32  while another voltage is applied to the lower electrode  22  from the external circuit through the connection terminal sections, then electrostatic force (Coulomb force) acts between the movable electrode  32  and the lower electrode  22  so that the movable electrode  32  is displaced toward the lower electrode  22 . More particularly, if a voltage is applied to the movable electrode  32  through the connection terminal section and the control electrode from the external circuit and another voltage is applied to the lower electrode  22  through the lower electrode terminal section from the external circuit (actually the lower electrode  22  is in a grounded state), then electrostatic force (Coulomb force) is generated between the movable electrode  32  and the lower electrode  22 . Then, the movable electrode  32  is displaced downwardly toward the lower electrode  22  by the electrostatic force. It is to be noted that the movable electrodes  32  and the lower electrode  22  at a stage before the displacement of the movable electrodes  32  are shown on the left side in  FIGS. 9B and 10B , and the movable electrodes  32  and the lower electrode  22  at another state after the displacement of the movable electrodes  32  are shown on the right side of  FIGS. 10A and 10B . Based on such displacement of the movable electrode  32 , a diffraction grating of the reflection type is formed from the movable electrode  32  and the fixed electrode  31 .  
      The difference Δh 0  in height between the top face of the lower electrode  22  and the top face of the fixed electrode  31  was set to a value given in Table 2 below. Further, the difference in height between the top face of the movable electrode  32  and the top face of the fixed electrode  31  when the diffraction grating-optical modulation element  21  is inoperative is set to a value as proximate as possible to zero. Furthermore, the maximum value Δh 1-MAX  of the difference Δh 1  (amount of the downward displacement of the movable electrode  32 ) in height between the top face of the movable electrode  32  and the top face of the fixed electrode  31  when the diffraction grating-optical modulation element  21  is operative satisfies 
 
Δ h   1-MAX =λ/4 
 
 where the wavelength of incoming light to the diffraction grating-optical modulation element  21  or the diffraction grating-optical modulation apparatus  11  is represented by λ. 
 
      Further, the relationship between Δh 1-MAX  and Δh 0  satisfies 
 
Δ h   1-MAX   ≦Δh   0 /3 
 
 It is to be noted that the difference Δh 1  (amount of the downward displacement of the movable electrode  32 ) in height between the top face of the movable electrode  32  and the top face of the fixed electrode  31  can be varied by varying the voltage to be applied to the movable electrode  32 . Since this can vary the intensity of the diffracted light, gradation control can be performed. 
 
      Further, the distance d between adjacent ones of the fixed electrodes  31 , the gap SP existing between any fixed electrode and an adjacent movable electrode, the width W F  of the fixed electrodes  31 , the effective length L F  of the fixed electrodes  31 , the width W M  of the movable electrodes  32  and the effective length L M  of the movable electrodes  32  are set to such values as given in Table 2 below. The unit in Table 2 is μm.  
                   TABLE 2                          Δh 0  =   0.85       d =   8.0       SP =   0.40       W F  =   3.6       L F  =   200       W M  =   3.6       L M  =   200                  
 
      An image forming apparatus including the three image production apparatus  101 R,  101 G and  101 B which in turn include the diffraction grating-optical modulation apparatus assemblies  102 R,  102 G and  102 B, which include such diffraction grating-optical modulation apparatus  103 R,  103 G and  103 B (having a configuration and structure same as those of the diffraction grating-optical modulation apparatus  11 ) as described above, and the light sources (laser light sources  100 R,  100 G and  100 B), respectively, may conceptively have a configuration similar to that described hereinabove with reference to  FIG. 12 . Also operation of the image forming apparatus which includes the three image production apparatus  101 R,  101 G and  101 B is similar to that described hereinabove with reference to  FIG. 12 . Therefore, detailed description of the configuration and structure and the operation of the image forming apparatus is omitted herein to avoid redundancy.  
     Embodiment 1  
      An embodiment 1 relates to an optical apparatus and an image production apparatus according to a first mode for carrying out the present invention. The optical apparatus of the embodiment 1 includes an optical element wherein a plurality of diffraction grating-optical modulation elements (GLV) are arrayed in a one-dimensional array. It is to be noted that, in the following description, the optical element is sometimes referred to as diffraction grating-optical modulation apparatus and the optical apparatus is sometimes referred to as diffraction grating-optical modulation apparatus assembly. Further, the image forming apparatus of the embodiment 1 includes the optical apparatus (diffraction grating-optical modulation apparatus assembly) and a light source (semiconductor laser) similarly to that shown in  FIG. 12 . A schematic partial sectional view of the optical apparatus (diffraction grating-optical modulation apparatus assembly) of the embodiment 1 is shown in  FIG. 1A , and a schematic bottom plan view of the optical apparatus (diffraction grating-optical modulation apparatus assembly) is shown in  FIG. 4 . It is to be noted that, in  FIGS. 1A, 1B ,  2 A,  2 B and  3 A, a diffraction grating-optical modulation element and so forth are omitted.  
      More particularly, the optical apparatus (diffraction grating-optical modulation apparatus assembly) of the embodiment 1 includes 
          (A) an optical element (diffraction grating-optical modulation apparatus  11 ),     (B) a mounting substrate  50 ,     (C) a support member  60 , and     (D) a cooling/heat radiating member  70  formed from a heat sink.        

      The support member  60  is attached by bonding agent  45  for die bonding to a face  50 A of the mounting substrate  50  which is formed from a printed circuit board formed from a glass epoxy copper-plated laminated plate. Meanwhile, the diffraction grating-optical modulation apparatus  11  is connected to the other face  50 B of the mounting substrate  50  by bonding agent  43  for die bonding. It is to be noted that a circuit for processing a signal inputted from the outside for driving the diffraction grating-optical modulation apparatus and other necessary circuits are provided on the mounting substrate  50 . This similarly applies also to embodiments 2 to 4 hereinafter described. Further, the cooling/heat radiating member  70  is attached to the support member  60  by means of screws or a bonding agent. The support member  60  functions as a joining plate for the cooling/heat radiating member  70  formed from a heat sink. The diffraction grating-optical modulation apparatus assembly can be attached to a body section of the image forming apparatus by means of screws, a bonding agent or the like.  
      The diffraction grating-optical modulation apparatus assembly in the embodiment 1 further includes semiconductor chips  40  on which a circuit (for example, a 10-bit or 12-bit driver) necessary to drive the diffraction grating-optical modulation apparatus  11  is provided. The semiconductor chips  40  is attached to the face  50 B of the mounting substrate  50  by bonding agent  44  for die bonding.  
      It is to be noted that, upon bonding wherein the bonding agent  43 ,  44  or  45  is used, it can be used for bonding by heating it, for example, to 130 to 200° C. although this depends upon the specifications of the bonding agent  43 ,  44  or  45 . This similarly applies to the embodiments 2 and 4 hereinafter described.  
      In the embodiment 1, the support member  60  is made of a material having a thermal conductivity of 230 W/m·K, particularly an aluminum (Al) plate having a thickness (t) of 4 mm. More particularly, the support member  60  made of aluminum can be produced by cutting.  
      The diffraction grating-optical modulation apparatus  11  and the support member  60  are thermally connected to each other by a heat transmission element provided in the inside of the mounting substrate  50 , particularly by heat transmitting via holes  51 . The heat transmitting via holes  51  can be obtained by forming through-holes in the mounting substrate  50  and filling a material (for example, copper or silver) having a high thermal conductivity into the through-holes. More particularly, a method of filling a paste-like material (for example, copper paste or silver paste) having a high thermal conductivity into the through-holes by a screen printing method and a method of filling a material (for example, copper) having a high thermal conductivity by a plating method can be used. One end of each of the heat transmitting via holes  51  contacts indirectly (that is, through the bonding agent  43  or  44 ) with the optical element (more particularly, with the support member  12  which composes the diffraction grating-optical modulation apparatus  11 ) or contacts with a semiconductor chip  40 . The other end of the heat transmitting via hole  51  contacts indirectly (that is, through the bonding agent  45 ) with the support member  60 .  
      Further, the diffraction grating-optical modulation apparatus  11  and the semiconductor chips  40 , and the semiconductor chips  40  and wiring lines provided on the mounting substrate  50 , are electrically connected to each other, for example, by bonded wires. The diffraction grating-optical modulation apparatus  11  and the semiconductor chips  40  are surrounded by a framework member  41  (made of a thermosetting resin material). Further, the diffraction grating-optical modulation apparatus  11  and the semiconductor chips  40  are enclosed in potting resin  42  to protect the bonded wires thereof. Where the diffraction grating-optical modulation apparatus  11  and semiconductor chips  40 , and the semiconductor chips  40  and wiring lines provided on the mounting substrate  50  are electrically connected to each other by bonded wires in this manner, the diffraction grating-optical modulation apparatus assembly can be formed in a reduced size and with a reduced weight.  
      In the embodiment 1 and also in the embodiments 2 to 4 hereinafter described, the light transmitting member  13  formed from a glass plate in the form of a flat plate and the support member  12  are joined (attached) together as shown conceptively in  FIG. 11  by a low-melting point metal material layer  14  made of Au 80 Sn 20 .  
      In the embodiment 1, since the support member  60  is used and besides the heat transmitting via holes  51  are provided, heat from the diffraction grating-optical modulation apparatus  11  and heat from the semiconductor chips  40  can be transmitted efficiently to the cooling/heat radiating member  70 . Besides, a high degree of accuracy in position of the diffraction grating-optical modulation element  21 , which is difficult where only a mounting substrate  350  which has a high coefficient of linear expansion (for example, approximately 14×10 −6 /K, which is higher than the coefficient of linear expansion 3.1×10 −6 /K of the support member  12 ), and has a Young&#39;s modulus of approximately 25 GPa and is very flexible, can be assured sufficiently in the embodiment 1 using the support member  60 .  
      Where thermal resistance values (unit: ° C. /W) were calculated with regard to the optical apparatus (diffraction grating-optical modulation apparatus assembly) of the embodiment 1, such values as listed in Table 3 below were obtained. Further, results of calculation of the thermal resistance value with regard to the conventional apparatus shown in  FIG. 13  are listed as those of a comparative example 1 in Table 3. Further, results of calculation of the thermal resistance value with regard to the structure of the embodiment 1 where the heat transmitting via holes  51  are not provided are listed as those of a comparative example 2 in Table 3. It is to be noted that S 1  and S 0  have a relationship of S 1 =0.1×S 0 .  
                               TABLE 3                                       Comparative   Comparative           Embodiment 1   Example 1   Example 2                                                    Diffraction Grating-   0.022   0.022   0.022       Optical Modulation       Apparatus 11       Bonding Agent 43   0.440   0.440   0.440       Mounting Substrate 250   —   7.85    7.85        Heat Transmitting   0.000   —   —       Via Hole 51       Bonding Agent 45   0.085   —   0.085       Support Member 60   0.049   —   0.049       Total   0.596   8.31    8.45                   
 
      From Table 3, it can be discriminated that, where the support member  60  is made of a material having a thermal conductivity of 230 W/m·K or more and the optical element (diffraction grating-optical modulation apparatus  11 ) and the support member  60  are thermally connected to each other by the heat transmission means (heat transmitting via holes  51 ) provided in the mounting substrate  50 , the thermal resistance value in the overall system in the embodiment 1 can be reduced to approximately {fraction (1/14)} when compared with that in the comparative example 1.  
     Embodiment 2  
      An embodiment 2 relates to an optical apparatus and an image forming apparatus according to a second mode for carrying out the present invention. Also the optical apparatus of the embodiment 2 particularly includes an optical element (diffraction grating-optical modulation apparatus) wherein a plurality of diffraction grating-optical modulation elements (GLV) are arrayed in a one-dimensional array. Also the image production apparatus of the embodiment 2 includes the optical apparatus (diffraction grating-optical modulation apparatus assembly) and a light source (semiconductor laser) similarly to that described hereinabove with reference to  FIG. 12 . A schematic partial sectional view of the optical apparatus (diffraction grating-optical modulation apparatus assembly) of the embodiment 2 is shown in  FIG. 1B , and a schematic partial perspective view of a mounting substrate of the optical apparatus (diffraction grating-optical modulation apparatus assembly) is shown in  FIG. 5A . Further, a schematic partial perspective view of the mounting substrate and a support member of the optical apparatus (diffraction grating-optical modulation apparatus assembly) is shown in  FIG. 5B , and a schematic partial plan view of the mounting substrate is shown in  FIG. 6A . It is to be noted that, in  FIGS. 6A, 6B ,  7 A,  7 B and  3 B, the position at which a diffraction grating-optical modulation apparatus is to be disposed is indicated by an alternate long and short dash line, and the position at which a semiconductor chip is to be disposed is indicated by a broken line.  
      More particularly, the optical apparatus (diffraction grating-optical modulation apparatus assembly) of the embodiment 2 includes 
          (A) an optical element (diffraction grating-optical modulation apparatus  11 ),     (B) a mounting substrate  150 , and     (C) a support member  16 Q.        

      The mounting substrate  150  is formed from a printed circuit board formed from a glass epoxy copper-plated laminated plate and has an opening  152  formed therein. The support member  160  is attached to a face  150 A of the mounting substrate  150  by bonding agent  45  for die bonding similarly as in the embodiment 1. The diffraction grating-optical modulation apparatus  11  is attached to a portion (support member projection  161 ) of the support member  160 , which is exposed to the outside through the opening  152  formed in the mounting substrate  150 , by bonding agent  43  for die bonding. The surface of the support member projection  161  is substantially in flush with the other face  150 B of the mounting substrate  150 . Further, the cooling/heat radiating member  70  formed from a heat sink is attached to the support member  160  by means of screws or bonding agent although this is not essential.  
      The diffraction grating-optical modulation apparatus assembly in the embodiment 2 further includes semiconductor chips  40  which in turn include each a circuit (for example, a 10- or 12-bit driver) required to drive the diffraction grating-optical modulation apparatus  11 . The semiconductor chips  40  are attached to the face  150 B of the mounting substrate  150  by bonding agent  44  for die bonding. Further, the semiconductor chips  40  and the support member  160  are thermally connected to each other by heat transmission means provided in the mounting substrate  150 , particularly heat transmitting via holes  151  provided in the mounting substrate  150 . Each of the heat transmitting via holes  151  contacts at one end thereof indirectly (that is, through the bonding agent  44 ) with a semiconductor chip  40 , and contacts at the other end thereof indirectly (that is, through bonding agent  45 ) with the support member  160 .  
      Also in the embodiment 2, the support member  160  is formed from a material having a thermal conductivity of 230 W/m·K or more, more particularly from an aluminum (Al) plate which has a thickness of 4 mm at the support member projection  161  thereof but has another thickness of 1.6 mm at the other portion thereof. More particularly, the support member  160  made of aluminum can be formed by cutting.  
      Also in the embodiment 2, the diffraction grating-optical modulation apparatus  11  and the semiconductor chips  40 , and the semiconductor chips  40  and circuits as wiring lines provided on the mounting substrate  150 , are electrically connected to each other by bonded wires. The diffraction grating-optical modulation apparatus  11  and the semiconductor chips  40  are surrounded by a framework member  41  (made of a thermosetting resin material) and are embedded in potting resin  42  to protect the bonded wires. Where the diffraction grating-optical modulation apparatus  11  and the semiconductor chips  40 , and the semiconductor chips  40  and the circuits as wiring lines, are electrically connected to each other by the bonded wires in this manner, the diffraction grating-optical modulation apparatus can be formed in a reduced size and with a reduced weight.  
      In the embodiment 2, since the diffraction grating-optical modulation apparatus  11  is attached to the portion (support member projection  161 ) of the support member  160  which is exposed in the opening  152  formed in the mounting substrate  150 , heat from the diffraction grating-optical modulation apparatus  11  can be radiated efficiently. Consequently, a high degree of accuracy in position of the diffraction grating-optical modulation element  21  can be assured sufficiently.  
      The thermal resistance value was calculated with regard to the optical apparatus (diffraction grating-optical modulation apparatus assembly) of the embodiment 2. The calculation indicated that the thermal resistance values (unit: ° C./W) of the locations exhibited substantially equal values as those listed in Table 3 and representing the values obtained from the embodiment 1 (more particularly, values increasing by 0.002° C./W).  
      It is to be noted that the opening  152  may be provided in a region spaced away from an edge of the mounting substrate  150  as seen in  FIG. 6A  or may be provided like a cutaway portion along an edge portion  150 C of the mounting substrate  150  as seen in  FIG. 6B .  
     Embodiment 3  
      An embodiment 3 is a modification to the embodiment 2. In the embodiment 2, the semiconductor chips  40  are attached to the face  150 B of the mounting substrate  150 . On the other hand, in the embodiment 3, the semiconductor chips  40  are attached to the portion (support member projection  161 ) of the support member  160  exposed in the opening  152  formed in the mounting substrate  150  by means of bonding agent  44  for die bonding as seen in  FIG. 2A  which shows a schematic partial sectional view of the optical apparatus (diffraction grating-optical modulation apparatus assembly). It is to be noted that a schematic partial perspective view of the mounting substrate  150  is same as that shown in  FIG. 5A , and a schematic partial perspective view of the mounting substrate  150  and the support member  160  is similar to that shown in  FIG. 5B . A schematic partial plan view of the mounting substrate  150  is shown in  FIG. 7A .  
      Except such an attached state of the semiconductor chips  40  as just described, the configuration and structure of the optical element (diffraction grating-optical modulation apparatus), optical apparatus (diffraction grating-optical modulation apparatus assembly) and image production apparatus are same as those described hereinabove in connection with the embodiment 2. Therefore, overlapping description of them is omitted herein to avoid redundancy.  
      It is to be noted that the opening  152  may be provided in a region spaced away from an edge of the mounting substrate  150  as seen in  FIG. 7A  or may be provided in the form of a cutaway portion along the edge portion  150 C of the mounting substrate  150 .  
     Embodiment 4  
      An embodiment 4 relates to an optical apparatus and an image production apparatus according to a third mode for carrying out the present invention. Also the optical apparatus of the embodiment 4 particularly includes an optical element (diffraction grating-optical modulation apparatus) wherein a plurality of diffraction grating-optical modulation elements (GLV) are arranged in a one-dimensional array. Also the image forming apparatus of the embodiment 4 includes an optical apparatus (diffraction grating-optical modulation apparatus assembly) and a light source (semiconductor laser) similarly to the apparatus shown in  FIG. 12 . A schematic partial sectional view of the optical apparatus (diffraction grating-optical modulation apparatus assembly) of the embodiment 4 is shown in  FIG. 3A , and a schematic partial plan view of a mounting substrate and a support member is shown in  FIG. 3B .  
      More particularly, the optical apparatus (diffraction grating-optical modulation apparatus assembly) of the embodiment 4 includes, similarly as in the embodiment 2, 
          (A) an optical element (diffraction grating-optical modulation apparatus  11 ),     (B) a mounting substrate  250 , and     (C) a support member  260 .        

      The support member  260  is attached to a face  250 A of the mounting substrate  250  by bonding agent  45  for die bonding such that it extends from an edge portion  250 C of the mounting substrate  250 , which is formed from a glass epoxy copper-plated laminated plate, to the outer side of the mounting substrate  250 . Meanwhile, the optical element (diffraction grating-optical modulation apparatus  11 ) is attached to a portion (support member projection  261 ) of the support member  260 , which extends to the outer side of the mounting substrate  250 , by bonding agent  43  for die bonding. Further, the cooling/heat radiating member  70  formed from a heat sink is attached to the support member  260  by means of screws or a bonding agent although this is not essential.  
      The diffraction grating-optical modulation apparatus assembly in the embodiment 4 further includes semiconductor chips  40  on each of which a circuit (for example, a 10- or 12-bit driver) necessary to drive the diffraction grating-optical modulation apparatus  11  is provided. The semiconductor chips  40  are attached to the support member  260  by bonding agent  44  for die bonding.  
      Also in the embodiment 4, the support member  260  is formed from a material having a thermal conductivity of 230 W/m·K or more, more particularly from an aluminum (Al) plate which has a thickness of 4 mm at the support member projection  261  thereof but has another thickness of 1.6 mm at the other portion thereof. More particularly, the support member  260  made of aluminum can be formed by cutting.  
      Also in the embodiment 4, the diffraction grating-optical modulation apparatus  11  and the semiconductor chips  40 , and the semiconductor chips  40  and circuits as wiring lines provided on the mounting substrate  150 , are electrically connected to each other by bonded wires. The diffraction grating-optical modulation apparatus  11  and the semiconductor chips  40  are surrounded by a framework member  41  (made of a thermosetting resin material) and are embedded in potting resin  42  to protect the bonded wires. Where the diffraction grating-optical modulation apparatus  11  and the semiconductor chips  40 , and the semiconductor chips  40  and the circuits as wiring lines, are electrically connected to each other by the bonded wires in this manner, the diffraction grating-optical modulation apparatus can be formed in a reduced size and with a reduced weight.  
      In the embodiment 4, since the diffraction grating-optical modulation apparatus  11  is attached to the support member projection  261 , heat from the diffraction grating-optical modulation apparatus  11  can be radiated efficiently. Consequently, a high degree of accuracy in position of the diffraction grating-optical modulation element  21  can be assured sufficiently.  
      The thermal resistance value was calculated with regard to the optical apparatus (diffraction grating-optical modulation apparatus assembly) of the embodiment 4. The calculation indicated that the thermal resistance values (unit: ° C./W) of the locations exhibited substantially equal values as those obtained from the embodiment 2.  
      Except the foregoing, the configuration and structure of the optical apparatus (diffraction grating-optical modulation apparatus assembly) of the embodiment 4 may be same as those described hereinabove in connection with the embodiment 2. Therefore, overlapping description of them is omitted herein to avoid redundancy.  
      It is to be noted that the semiconductor chips  40  may be attached otherwise to the other face  250 B of the mounting substrate  250  by means of bonding agent for die bonding. In this instance, the semiconductor chips  40  and the support member  260  are preferably thermally connected to each other by heat transmission means provided in the mounting substrate  250 , particularly by via holes for heat transmission. The via holes for heat transmission can be configured such that each of them contacts at one end thereof indirectly (that is, through the bonding agent) with a semiconductor chip  40  and at the other end thereof indirectly (that is, through the bonding agent  45 ) with the support member  260 .  
      While the present invention is described in connection with preferred embodiments thereof, the present invention is not limited to them. The structures and configurations of the diffraction grating-optical modulation elements, optical elements (diffraction grating-optical modulation apparatus), optical apparatus (diffraction grating-optical modulation apparatus assemblies) and image production apparatus are merely illustrative and can be altered suitably. Also the materials which form the various members of the diffraction grating-optical modulation apparatus assemblies, diffraction grating-optical modulation elements, and dimensions of the members and so forth are merely illustrative and can be altered suitably.  
      Where the amount of heat generated from the semiconductor chips is small, the via holes for heat transmission for thermally connecting the semiconductor chip and the support member to each other need not be provided.  
      Although, in the embodiment 2, the support member projection  161  is provided on the support member  160 , the surface of the portion of the support member  160  which is exposed in the opening  152  formed in the mounting substrate  150  may be substantially in level with the face  150 A of the mounting substrate  150  as seen from the schematic partial sectional view of  FIG. 2B . It is to be noted that also the structure just described can be applied to the embodiment 3 or the embodiment 4.  
      While, in the embodiments described above, the support members  60 ,  160  and  260  are made of aluminum (Al), they may otherwise be made of copper (Cu), beryllium-copper alloy, silver or gold. Alternatively, they may be made of a material of at least two materials selected from a group consisting of the materials mentioned. In this instance, the support member is preferably formed in a multilayer structure.  
      While, in the embodiments described above, the top faces of the movable electrodes  32  and the top faces of the fixed electrodes  31  extend in parallel to the top face of the lower electrode  22 , the movable electrodes  32  and the fixed electrodes  31  may be formed as electrodes of the blazed type inclined by a blaze angle θ D  with respect to the top face of the lower electrode  22  so that, for example, only +first order (m=+1) diffracted light may be emitted.  
      While preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.  
     
       FIGS. 1A and 1B 
     
      Diffraction grating-optical modulation apparatus assembly  
     
       FIGS. 2A and 2B 
     
      Diffraction grating-optical modulation apparatus assembly  
     
       FIG. 3A 
     
      Diffraction grating-optical modulation apparatus assembly  
       FIG. 8 , from left, from above  
      To control electrode  
      To control electrode  
      Y direction  
      X direction  
      To bias electrode  
     
       FIGS. 9A and 9B 
     
      X direction  
     
       FIG. 10A 
     
      X direction  
     
       FIG. 10B 
     
      Y direction  
     
       FIG. 12 
     
      Scanning direction  
     
       FIG. 13 
     
      Diffraction grating-optical modulation apparatus assembly