Abstract:
An optical element has a marker provided in the form of an optical fault at a predetermined location in the effective optical area thereof for positioning. The optical fault is a marker  1   a  provided at a specific location on the effective optical area of the optical element  1  preferably in the form of a projection, a recess, a tinted portion, a different refraction portion, an air bubble, or a particle on or in the optical element  1 . More preferably, the marker  1   a  is located at or around the center of the optical element  1  and its area size is not greater than 0.4% of the effective optical area of the lens  1.

Description:
The priority Japanese Patent Application Numbers 2005-51590 and 2006-23285 upon which this patent application is based is hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to optical elements such as a lens, a mirror, a prism, a filter and a diffractive optical element, for use in optical equipment such as camera machines including a digital camera, a camera-equipped mobile telephone and the like, projection machines including a video camera, a liquid crystal projector, a liquid crystal rear projector and the like, a telescope, and a microscope, optical information equipment such as an optical pickup, and optical communication equipment such as an optical transceiver module and an optical switch, and also relates to a method of manufacturing the same. 
   2. Description of the Related Art 
   In general, an optical system in optical equipment such as a camera machine is configured by a combination of optical elements including a large number of lenses, mirrors, prisms, filters and diffractive optical elements. Further, the optical system is combined with components including a light-emitting device such as an LED, an image display device such as an LCD, a photodetector such as a photodiode or a CCD; thus, an optical equipment is configured. It is essential for assembling the optical system or the optical equipment to correctly align those components with an optical axis. If the optical system or the optical equipment is dislocated from the optical axis, there arises a problem of skew and blurring of an image, so that good image forming performance cannot be obtained. 
   Conventionally, the optical system has been fabricated by assembling the finely sized optical components including lenses in a frame. As disclosed in JP-A 2003-172807, a technique is known where a lens barrel includes two groups of lenses secured in a frame. It is common in the prior art that the lenses are mounted to a frame for aligning with the optical axis at a practically acceptable degree of precision. 
   As digital cameras have been marketed widely, some types of them are built in mobile telephones. It is thus desired for reducing of the overall dimensions that the lenses in the optical system are as small as 3 mm in diameter. In addition, a variety of CCDs as the photodetectors have been developed with reduction of the size and improvement of the precision. As the result, the alignment with the optical axis during the manufacturing process will be more troublesome. In fact, the degree of precision for alignment with the optical axis is measured in about micrometers. More specifically, the tolerance of lens diameter is as small as substantially about tens micrometers. It is hence impractical that the degree of accuracy for alignment with the axis depends on the conventional manner of mounting the optical components to a housing. 
   For compensation, another technique is disclosed in JP-A 2002-72078 where a marker is provided around the lens by dry etching for use as a reference in the action of alignment with the optical axis. However, the area for such a marker will hardly be spared when the lens is significantly reduced in the overall size. 
   SUMMARY OF THE INVENTION 
   It is hence an object of the present invention to provide an optical element arranged for being positioned at higher accuracy with much ease and a method of manufacturing the optical element. 
   An optical element according to the present invention comprises a marker provided in the form of an optical fault at a specific position on the effective optical area of the optical element for positioning of the optical element. 
   The optical element according to the present invention may be modified in which the optical fault provided as the marker for positioning is a projection, a recess, a tinted portion, or a different refraction portion of the optical element or an air bubble or a particle in the optical element. 
   As a preferred embodiment of the present invention, an optical element comprises an optical fault provided as the marker for positioning preferably in the form of a projection, a recess, a tinted portion, or a different refraction portion, an air bubble, or a particle provided at the specific position on the effective optical area of or in the optical element. 
   In the optical element according to the present invention, the marker is located on the effective optical area. Since no extra space outside the effective optical area is required unlike the prior art, the optical element can favorably be reduced in the overall size without sacrificing the space for the marker. 
   Herein, the effective optical area refers to a region where light can pass in design. Accordingly, the marker in the present invention is located in a region where light passes in design. 
   Preferably, the effective size of the marker is not greater than 200 μm. When its effective size is not greater than 200 μm, the marker can be monitored within the viewing field of a common optical microscope. More particularly, the minimum of the effective size of the marker is equal to a level that can be monitored within the viewing field of a common optical microscope or not smaller than 10 μm or preferably not smaller than 50 μm. If the marker is smaller than 10 μm in the effective size, its identification with a common optical microscope will be difficult. When smaller than 50 μm, the marker will be monitored with difficulty. 
   The effect size of the marker means an extension that can effectively be utilized for correctly positioning the component by the marker and may be a maximum of the diameter. More particularly, when the marker is arranged of a circular shape, its diameter represents the effective size. When the marker is of an ellipse or oval shape, its longer diameter represents the effective size. When the marker is of a rectangular shape such as a square, its diagonal line represents the effective size. 
   As will be described later, the effective size may be equal to an area surrounded by the marker(s) provided around the center of the optical element. 
   According to the present invention, the marker may be provided in the form of preferably a projection, a recess, a tinted portion, or a different refraction portion of the optical element or an air bubble or a particle in the optical element. For example, the projection may be fabricated with a die which has a recessed region provided at the corresponding region thereof for use in the action of shaping the optical element. The recess may similarly be fabricated with a die which has a raised region thereof. The recess may also be fabricated by machining, wet etching, or dry etching of the surface of the optical element. 
   The tinted portion may be fabricated when the surface of the optical element is tinted with a die, a pigment containing ink, or a paint by, e.g., an ink jet technique. 
   The different refraction portion, the air bubble, or the particle in the optical element may be fabricated by a different refraction material, an air bubble, or a particle impregnated in the optical element during the manufacturing process. 
   According to the present invention, the marker is preferably provided at the center or around the center of the optical element. When the marker is around the center of the optical element, it is embodied by a set of markers arranged in symmetrical relationship. It is noted that the center represents all center regions along the optical axis and may be in or on the optical element. The term “optical axis” represents a chain of the major axes of the optical elements provided in the optical system. 
   The optical element according to the present invention may be modified in which it is made entirely or partially of an organic polymer material. Preferably, the marker is positioned at the organic polymer material region of the optical element. 
   The organic polymer material may be selected from energy setting resins such as thermoplastic resin or ultraviolet curing resin, thermosetting resins, and organic/inorganic composite materials. More specifically, examples of the organic polymer material include organic metal polymer prepared by hydrolyzing and polymerizing metal alkoxide, acrylate resin, epoxy resin, urethane resin, urethane acrylate resin, polyester acrylate resin, epoxy acrylate resin, their combination, and their mixture with a dispersed form of particles of metal oxide such as SiO 2 , TiO 2 , ZrO 2 , or Nb 2 O 5 . 
   The optical element according to the present invention may be modified in which the organic polymer material is provided in the form of a layer on a substrate of a glass material. For example, the optical element is a composite aspherical lens having an organic polymer layer provided as an aspherical lens on a spherical glass lens. The substrate may be made of, rather than glass, any optical resin such as ARTON resin produced by JSR, ZEONEX resin produced by Nippon Zeon, or OKP4 produced by Osaka Gas Chemicals (each in trade name). 
   The optical elements according to the present invention may include a lens, a mirror, a prism, a filter, and a diffractive optical element. 
   As a first aspect of the present invention, a method of manufacturing the optical element which is made entirely or partially of an organic polymer material and has a marker provided therein or thereon is characterized in that while the organic polymer material is shaped with a die(s) which has a marker forming region, the marker is shaped with the marker forming region. 
   The marker forming region of the die may be a raised region or a recessed region. 
   Alternatively, the die may have a filling inlet provided therein for introducing the organic polymer material or its pre-cured, liquid form as so arranged that when the organic polymer material or its pre-cured, liquid form is introduced, a burr which then turns to the marker can be produced at its location, thus allowing the filling inlet to serve as a marker forming region of the die. Accordingly, the filling inlet in the die can serve as the marker forming region. 
   When the optical element is manufactured by providing an organic polymer layer on the surface of a substrate, the action of positioning the die in relation to the substrate may be conducted according to a second aspect or a third aspect of the present invention. 
   As the second aspect of the present invention, a method of manufacturing the optical element is characterized by the steps of measuring the diameter of both the substrate and the die, calculating from a difference in the measurement, when each of the substrate and the die has been pressed against the reference surface, a dislocation along the horizontal from the reference surface and moving the substrate or the die away from the reference surface by a distance equal to the dislocation thus to position correctly along the horizontal, and while the substrate and the die remain correctly positioned along the horizontal, moving the substrate or the die in the vertical until the substrate and the die come into direct contact with each other and shaping the organic polymer material with the die. 
   Using the method of the second aspect, the positional alignment between the substrate and the die can be conducted with much ease. 
   As the third aspect of the present invention, a method of manufacturing the optical element is characterized by the steps of, when the substrate is a spherical lens, placing the die provided with the filling inlet on the spherical lens, which remains seated along the horizontal with its spherical side facing upwardly, so that the filling inlet faces downwardly to extend along the vertical, illuminating the spherical lens with an autocollimator light across the filling inlet of the die and correctly positioning the spherical lens and the die along the horizontal when the autocollimator light is reflected by the spherical side and passed through the filling inlet, and while the spherical lens and the die remain correctly positioned along the horizontal, moving the substrate or the die along the vertical to press the die against the substrate for shaping the organic polymer material. 
   Using the method of the third aspect, the positional alignment between the spherical lens and the die can be conducted easily and accurately. 
   An optical system according to the present invention comprises at least one of the foregoing optical elements. The optical system according to the present invention comprises a construction including at least one optical element which has an optical function of diverging or focusing a ray of light to develop an optical image. Accordingly, the optical system is constructed by at least a lens, a mirror, a prism, a filter, a diffractive optical element, or any other optical element for diverging or focusing a ray of light to develop an optical image. 
   As the optical system includes the optical element provided with a marker for positioning, its assembly can readily be conducted through accurate positioning. 
   A method of manufacturing an optical equipment according to the present invention is provided in which the optical equipment is manufactured from a combination of one of the foregoing optical elements and a component having a marker or a pattern provided as the marker. The method comprises the steps of placing any of the optical element and the component so that the marker or the pattern is aligned with a specific location in the viewing field of a microscope, and while the microscope remains fixed at its position along the horizontal, placing the other, the component or the optical element, so that the marker or the pattern is aligned with a specific location in the viewing field of a microscope thus to correctly position the optical element and the component along the horizontal. 
   Using the method, the optical element and the component can be positioned and assembled together easily and accurately thus to construct an optical system. 
   An optical equipment according to the present invention comprises the optical system described above. Examples of the optical equipment according to the present invention are optical equipment including a camera machine such as a digital camera or a camera-equipped mobile telephone, a projection machine such as a video camera, a liquid crystal projector or a liquid crystal rear projector, a telescope, a microscope, any other device, optical information equipment such as an optical pickup, and optical communications equipment such as an optical transceiver module or an optical switch. 
   The optical equipment according to the present invention may include any component which has a pattern of pixels or electrodes used as the marker. More particularly, the optical equipment according to the present invention may comprise a combination of the optical element of the present invention and a component on which the optical element is positioned and secured. The component is arranged to carry a marker or a pattern used as the marker for correctly positioning the optical element in relation to the component. 
   The optical equipment according to the present invention may also include the inventive optical system for developing a focused image. 
   Preferably, the area of the marker on the optical element in the optical equipment according to the present invention is arranged, when the dynamic range of an image signal to be processed excluding the optical system is D, to be not greater than 1/D the effective optical area. This permits any artifact in a resultant optical image to be lower than the level of noise in the equipment. Accordingly, the marker on the optical element can be fabricated without disturbing the S/N ratio of the image signal. 
   For example, when the dynamic range of a digital camera lens for producing 8-bit gradation of each of the R, G, and B colors is 2 8 =256 (≅48 dB), the area of the marker is set to not greater than 1/256≅0.4% of the effective optical area size of the digital camera lens. Accordingly, assuming that the lens(s) is substantially 3 mm in the diameter, the diameter of the marker can favorably be not greater than 200 μm. 
   The optical element according to the present invention is arranged in which the marker is provided at a specific location of the effective optical area of the optical element in the form of a projection, a recess, a tinted region, or a different refraction region of the optical element or an air bubble or a particle impregnated in the optical element. Since the marker is located within the effective optical area, it can be provided on the optical element of a smaller size. 
   Also, as the marker is used as a reference for alignment with the optical axis, the action of positioning can be conducted at higher accuracy. 
   The method of manufacturing the optical element according to the first aspect of the present invention allows the marker to be shaped with the marker forming region of the die during the action of shaping the organic polymer material, hence improving the ease of fabricating the marker. 
   The method of manufacturing the optical element according to the second aspect of the present invention allows the organic polymer layer to be provided on the substrate with the die having been positioned correctly in relation to the substrate. 
   The method of manufacturing the optical element according to the third aspect of the present invention allows the die to be positioned at higher accuracy over the spherical lens, thus improving the accuracy of shaping the organic polymer layer on the spherical lens. 
   The optical system and the optical equipment with the optical system according to the present invention allows the marker on the optical element to be utilized for alignment of the optical element, thus facilitating the action of assembling and positioning. 
   The method of manufacturing the optical system according to the present invention allows the optical element and the component to be positioned and assembled at higher accuracy but no difficulty, thus improving the positional relationship in the optical system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross sectional view of an optical element showing one embodiment of the present invention; 
       FIG. 2  is a cross sectional view showing the optical element of the embodiment, shown in  FIG. 1 , mounted to a frame; 
       FIG. 3  is a perspective view of a semi-circular frame in which a lens is installed; 
       FIGS. 4A to 4D  are cross sectional views showing steps of positioning and securing the optical element of the embodiment shown in  FIG. 1 ; 
       FIG. 5  is a cross sectional view of a camera module which includes the optical element of the embodiment shown in  FIG. 1  accompanied with an imaging device (CCD); 
       FIG. 6  is a cross sectional view of an optical element showing another embodiment of the present invention; 
       FIGS. 7A to 7D  are cross sectional views showing different forms of a marker according to the present invention; 
       FIGS. 8A to 8E  are plan views showing more different forms of the marker according to the present invention; 
       FIG. 9  is a cross sectional view of an optical element showing a further embodiment of the present invention; 
       FIG. 10  is a side view of a manufacturing equipment where a method of manufacturing an optical element is conducted showing a second aspect of the present invention; 
       FIG. 11  is a plan view of the manufacturing equipment where the method of manufacturing an optical element is conducted according to the second aspect of the present invention; 
       FIGS. 12A to 12C  are side views of the manufacturing equipment where the method of manufacturing an optical element is conducted according to the second aspect of the present invention; 
       FIGS. 13D to 13G  are side views of the manufacturing equipment where the method of manufacturing an optical element is conducted according to the second aspect of the present invention; 
       FIG. 14  is a plan view showing a lens positioned with the use of a V block; 
       FIG. 15  is a cross sectional view of an optical element showing a still further embodiment of the present invention; 
       FIGS. 16A and 16B  are cross sectional views showing a method of manufacturing an optical element according to a third aspect of the present invention; 
       FIG. 17  is a plan view of an optical element showing a still further embodiment of the present invention; 
       FIG. 18  is a cross sectional view taken along the line A-A of  FIG. 17 ; 
       FIGS. 19A and 19B  are cross sectional views showing steps of assembling a hologram unit including the optical diffractive optical element shown in  FIG. 17 ; 
       FIGS. 20A to 20D  are plan views showing the effective size of the marker according to the present invention; 
       FIG. 21  is a schematic cross sectional view of a projector showing a still further embodiment of the present invention; 
       FIG. 22  is a schematic cross sectional view of an optical transceiver module for fiber optic communications showing a still further embodiment of the present invention; 
       FIGS. 23A to 23E  are schematic cross sectional views showing steps of manufacturing the optical transceiver module shown in  FIG. 22 ; and 
       FIG. 24  is a block diagram of a digital camera with the camera module shown in  FIG. 5 , showing a still further embodiment of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Some embodiments of the present invention will now be described in more detail as only illustrative but not restrictive. 
   Embodiment 1 
     FIG. 1  is a side view of a lens as an optical element showing one embodiment of the present invention. As shown in  FIG. 1 , the lens  1  has a recess or marker  1   a  provided in the center thereof. The marker  1   a  shown in  FIG. 1  is arranged of a circular recessed shape and can thus be implemented with the use of a cutting tool  11  such as a drill. The lens  1  is made of a glass material such as BK7 type, having a diameter of 3 mm. Its marker  1   a  is 200 μm in the diameter and substantially 50 μm in the depth. 
   The lens  1  of the embodiment is intended for use in an 8-bit gradation digital camera and the size of its marker  1   a  is 0.4% of the effective optical area of the lens  1 . As the marker  1   a  is of the circular shape, its effective area is 200 μm in the diameter. It is however desirable to decrease the effective area of the marker  1   a  when the lens is smaller than that of this embodiment or used in another equipment which is higher at the number of gradation bits or in a further equipment such as an analog equipment at a higher S/N ratio which is greater in the dynamic range. 
   Embodiment 2 
     FIGS. 2 to 4  illustrate steps of manufacturing an optical system from a combination of the lens shown in  FIG. 1  and other components. The action starts with securely holding the lens  1  between a pair of semi-circular frames  12  and  13  as shown in the perspective view of  FIG. 3 . 
   More particularly, as shown in  FIG. 2 , the lens  1  is bonded by an adhesive  14  to the inner side of the semi-circular frame  12 . 
   Next, as shown in  FIG. 4A , the lens  1  held in the semi-circular frame  12  is positioned beneath at the focusing point of a microscope  14 . The lens  1  is then moved horizontally until its marker  1   a  is viewed at the scale  14   a  in the viewing field of the microscope  14 . 
   This is followed by lowering the semi-circular frame  12  and the lens  1  by a distance defined by the lens design, as shown in  FIG. 4B , and placing another component or lens  15  at the focusing point of the microscope  14  with the use of, e.g., a vacuum collet and adjusting the position of the lens  15  the same until its marker  15   a  is viewed at the scale  14   a  of the microscope  14 , as shown in  FIG. 4C . 
   Then, the lens  15  is bonded by an adhesive  14  to the semi-circular frame  12 , as shown in  FIG. 4D . 
   The other semi-circular frame  13  is joined to the semi-circular frame  12  to sandwich and secure the two lenses  1  and  15  by adhesive. 
   A resultant optical system in this embodiment is thus composed of the lens  1  with the marker  1   a  and the other lens  15  with the marker  15   a  which have been positioned and assembled together at higher accuracy. 
   The lens  15  in this embodiment is a meniscus lens made of a glass material of SF10 type for constructing a common achromatic mode of the optical system. Alternatively, the optical system may be of another multi-lens complex mode rather than the achromatic mode. Also, the optical system may include any other optical components than the lenses including a wavelength plate, a filter, and a diffractive optical element. 
   Embodiment 3 
     FIG. 5  is a cross sectional view showing a camera module provided as an optical equipment which has an imaging device (CCD)  17  mounted in a housing  16  and aligned with the optical system of the previous embodiment which comprises the lens  1  and the lens  15  secured between the two frames  12  and  13 . 
   In the camera module shown in  FIG. 5 , the positioning of the optical system in relation to the imaging device is conducted by the same manner as of Embodiment 2. It is hence desired to have a marker on the imaging device. Since the imaging device such as a CCD includes a pattern of pixels, its marker may be implemented by the pattern of pixels. Accordingly, the imaging device in this embodiment is provided with no marker and its positional alignment with the optical system is based on the pattern of pixels. 
     FIG. 24  is a block diagram showing a digital camera in which the camera module of this embodiment shown in  FIG. 5  is employed. As illustrated in  FIG. 24 , the cameral module  60  shown in  FIG. 5  is connected to a DA converter  61  which is in turn connected with a digital signal processor  62 . The digital signal processor  62  is connected with a display  63 , an external interface  64 , and an internal memory  65 . With the DA converter  61  of 8-bit type providing a dynamic range of 256, any image interruption produced by the lens with 200 μm of the marker side of Embodiment 1 can be as small as not exceeding the resolution of the DA converter  61 , thus hardly affecting the S/N ratio of each image. 
   It was found through a series of experimental image capturing actions that the quality of pictures produced by the digital camera of this embodiment was favorable with no presence of significant noises and skew. 
   Although the markers or optical faults are provided on the two lenses respectively in this embodiment, they are aligned with each other along the optical axis and their adverse effect will never be doubled. 
   Also, the imaging device in this embodiment is a CCD, it may be implemented by any applicable form such as a C-MOS image sensor. Moreover, the camera module of this embodiment may be applied to a digital cameral, a digital video camera, a camera-equipped mobile telephone, or an automobile mounting camera. 
   Embodiment 4 
     FIG. 6  is a cross sectional view showing a method of molding a resin material in a set of dies to fabricate a lens as the optical element according to a further embodiment of the present invention. As shown in  FIG. 6 , the lens  1  is fabricated by molding the resin material in a set of dies  4  and  5 . With the die  4  having a recess  4   a  provided in the inner side at the center thereof, a marker  1   a  of a raised form can be shaped at the center of the lens  1  during the molding process. 
   The lens  1  is made of a commercial resin material, ARTON (trade name), produced by JSR. The diameter of the lens  1  is 3 mm while the marker  1   a  is 200 μm in the diameter and substantially 50 μm in the height. 
   The material of the lens  1  is not limited to ARTON but may be selected from other commercially available resin materials including ZEONEX (trade name) of Nippon Zeon and OKP4 (trade name) of Osaka Gas Chemicals. 
   The marker  1   a  in this embodiment may also be arranged of such another raised shape as shown in  FIG. 7A  or such recessed shapes as shown in  FIGS. 7B and 7C . Alternatively, the marker  1   a  may be arranged of an annular projection shown in  FIG. 7D  or an annular recess. The shape of the marker  1   a  is not limited to the particular projections or recesses. The marker  1   a  may further be formed from a tinted portion of the lens. 
   The number of the markers is not limited to one but may be two or more such as shown in  FIGS. 8A to 8E .  FIG. 8A  illustrates a rectangular shape at plan view of the marker  1   a .  FIG. 8B  illustrates four of the rectangular markers  1   a . When two or more of the markers are provided, they may preferably be allocated about the center of the optical element or more preferably in symmetrical relationship about the center. As shown in  FIG. 8C , the marker may be a set of triangle shapes of which the vertices face the center of the optical element, thus facilitating the recognition of the center.  FIG. 8D  illustrates a circular shape of the marker similar to that of Embodiment 1.  FIG. 8E  illustrates an annular projection or recess of the marker similar to that shown in  FIG. 7D . The marker may specifically be arranged to carry other data, e.g., the manufacturing number, the manufacturing date, and the specifications of the lens, than the positioning data by modifying its number, size, and arrangement. 
     FIGS. 20A to 20D  are plan views explaining an effective area for positioning with the marker according to the present invention. More specifically,  FIG. 20A  illustrates a group of the markers similar to those shown in  FIG. 8B . As the center of the optical element denoted by the hatching in  FIG. 20A  is surrounded and defined by the markers, it can be the effect area  1   b  for positioning of the optical element. Accordingly, the maximum of the effective area  1   b  can determine the actual effectiveness of the markers according to the present invention. 
     FIG. 20B  illustrates a set of the markers similar to those shown in  FIG. 8C . This also allows the effective area  1   b  to be surrounded and defined by the triangle markers. The maximum of the effective area  1   b  can determine the effectiveness of the markers. 
     FIG. 20C  illustrates a shape of the marker similar to that shown in  FIG. 8E . This also allows the effective area  1   b  to be surrounded and defined by the annular marker  1   a . The maximum or diameter of the effective area  1   b  can determine the effectiveness of the marker. 
     FIG. 20D  illustrates two crossing lines of the marker at a right angle to each other. The effective area  1   b  is defined by the intersection between the two straight lines. The maximum or diameter of the effective area  1   b  can also determine the effectiveness of the marker. 
   The term “marker area” means the size of the marker. 
   Embodiment 5 
     FIG. 9  is a cross sectional view of a lens showing a further embodiment of the present invention. As shown in  FIG. 9 , the lens  1  as an optical element comprises an organic polymer layer  3  provided on a substrate  2 . For example, the organic polymer layer  3  is provided on the substrate  2  made of a spherical surface glass lens, whereby the lens  1  is an aspherical composite lens. 
   The organic polymer layer  3  may be fabricated by shaping an organic polymer coated on the substrate  2  with a molding die  4  as shown in  FIG. 9 . With the molding die  4  having a recess  4   a  provided in the inner side at the center thereof, a marker  3   a  of a raised shape is shaped at the center of the organic polymer layer  3 . 
   In this embodiment, the organic polymer layer  3  is made of a mixture of an organic metal polymer prepared by hydrolyzing and polymerizing metal alkoxide and an urethane acrylate resin. As the composite optical element or lens is made of such an organic/inorganic composite material, it can be improved in the thermal resistance and the dimensional stability. 
   Embodiment 6 
     FIGS. 10 to 14  illustrate step of conducting the forming of an organic polymer layer  3  on a substrate  2  with a molding die  4  similar to that of Embodiment 3 shown in  FIG. 9 . 
   This embodiment of the method resides in s a second aspect of the present invention, involving measuring the diameter of the substrate and the die, calculating a dislocation in the position between the substrate and the die from a difference between the two measurements of the diameter, moving either the substrate or the die by a distance equal to the dislocation, and molding the organic polymer layer with the die of which the position is aligned with the substrate across the horizontal. 
     FIG. 10  is a side view of an equipment employing the method of this embodiment.  FIG. 11  is a plan view of the same. As shown in  FIG. 10 , a planar block  22  having a reference surface  22   a  is placed on a stage  25  while a V block  23  is placed on another stage  26 . The V block  23  may be replaced by a micrometer  27  as described later. A lens stage  24  is provided between the two stages  25  and  26 . A die  21  is provided above the lens stage  24 . The die  21  is arranged for movement along the z axis or the vertical direction. 
   Both the planar block  21  and the V block  23  are arranged for movement along the x axis respectively. 
   As shown in  FIG. 11 , the center of a V slot  23   a  in the V block  23  is aligned with the center of the die  21  along a straight line extending in parallel with the x axis. 
   The lens stage  24  is made of a glass material. An ultraviolet light source and a shutter for controlling the transmission of ultraviolet light, both not shown, are provided beneath the lens stage  24 . The ultraviolet light source is provided for emitting an ultraviolet light to cure the organic polymer layer. 
   The method starts with, as shown in  FIG. 12A , lifting down the die  21  and moving the planar block  22  to the right until its reference surface  22   a  comes into direct contact with the die  21 . 
   This is followed by, as shown in  FIG. 12B , lifting up the die  21  and placing a micrometer  27  on the stage  26 . Then, the head of the micrometer  27  is advanced up to the reference surface  22   a  of the planar block  22  before the distance to the reference surface  22   a  is measured. 
   As shown in  FIG. 12C . the die  21  is lifted down once again until its one side comes into direct contact with the reference surface  22   a  of the planar block  22 . Then, the head of the micrometer  27  is moved to come into direct contact with the other side of the die  21  and the distance to the other end of the die  21  is measured. This allows the diameter of the die  21  to be calculated. 
   Then, the lens  1  is placed on the lens stage  24  so that its one side comes into direct contact with the reference surface  22   a  of the planar block  22  as shown in  FIG. 13D . This is followed by advancing the head of the micrometer  27  up to the other side of the lens  1 . This allows the diameter of the lens  1  to be calculated. 
   Then, the planar block  22  is moved to the left by a distance equal to a half the diameter of the lens or the die, as shown in  FIG. 13E . 
   Next, as shown in  FIG. 13F , the V block  23  is placed on the stage  26  in place of the micrometer  27  and moved to the left for carrying the lens  1  leftwardly until the lens  1  comes at one end into direct contact with the reference surface  22   a  of the planar block  22  and its position is thus determined. More particularly, as shown in  FIG. 14 , the lens  1  remains in direct contact with the reference surface  22   a  of the planar block  22  and at its position while being supported by the V block  23 . This is followed by introducing a predetermined amount of the organic polymer material of an uncured form onto the lens  1  and lifting down the die  21 . As the result, the state is as shown in  FIG. 13G . 
   As shown in  FIG. 13G , with the lens  1  remaining pressed down by the die  21 , the shutter beneath the lens stage  24  is released for exposure to ultraviolet light from the ultraviolet light source. The organic polymer layer developed between the lens  1  and the die  21  is then exposed to and cured by the ultraviolet light. 
   As described, the method according to the second aspect of the present invention allows the lens and the die to be aligned and positioned with ease and accuracy for favorably developing the organic polymer layer on the lens. Since the die is positioned at higher accuracy, it can shape the marker on the lens at higher precision. 
   Embodiment 7 
     FIG. 15  is a cross sectional view showing a lens as an optical element according to a further embodiment of the present invention. As shown in  FIG. 15 , the lens  1  comprises an organic polymer layer  3  provided on a substrate  2  made of a glass material. The organic polymer layer  3  has a marker  3   a  provided therein as aligned with the center of the lens  1 . 
   In this embodiment, the organic polymer layer  3  is shaped with the use of a die  4  which has a filling inlet  4   b  provided therein. For the purpose, with the die  4  seating over the substrate  2 , an organic polymer material is fed into a reservoir  4   c  in the die  4  and injected through the filling inlet  4   b  from the reservoir  4   c  to develop the organic polymer layer  3  over the substrate  2 . The organic polymer layer  3  in this embodiment may be equal to that of Embodiment 3. Accordingly, the layer  3  can be cured by ultraviolet light emitted from below. 
   The marker  3   a  in this embodiment is shaped as a burr in the filling inlet  4   b  of the die  4 . For the purpose, the inner diameter of the filling inlet  4   b  may thus be arranged to range preferably from 50 μm to 200 μm. As the result, the marker  3   a  may be shaped within a range of the diameter from 50 μm to 200 μm. 
   Embodiment 8 
     FIGS. 16A and 16B  are cross sectional views showing steps of a method for positioning the die  4  shown in  FIG. 15  over the substrate  2  according to a third aspect of the present invention, 
   As shown in  FIG. 16A , the method starts with locating the die  4  above the substrate  2  and projecting autocollimator light  6  across the filling inlet  4   b  of the die  4  onto a spherical surface  2   a  of the substrate  2  which is a spherical lens. If the filling inlet  4   b  is dislocated from the center of the spherical lens  2 , it fails to correctly receive a reflection of the autocollimator light  6  from the spherical surface  2   a  to which the autocollimator light  6  has been projected. When the filling inlet  4   b  is correctly aligned with the center of the spherical lens  2 , it can correctly receive a reflection of the autocollimator light  6  from the spherical surface  2   a  which extends along the horizontal as shown in  FIG. 16B , and a detector detects the reflection. 
   It is hence judged from the reflection of the autocollimator light  6  whether or not the filling inlet  4   b  in the die  4  is correctly aligned with the center of the spherical lens  2 . With its filling inlet  4   b  remaining positioned at the center of the spherical lens  2 , the die  4  is lifted down to the spherical lens  2  for depositing the organic polymer layer  3  as shown in  FIG. 15 . As the result, the marker  3   a  can accurately be developed at the center of the spherical lens  2 . 
   Embodiment 9 
     FIG. 17  is a plan view of a diffractive optical element as an optical element according to a further embodiment of the present invention.  FIG. 18  is a cross sectional view taken along the line A-A of  FIG. 17 . 
   As shown in  FIGS. 17 and 18 , the diffractive optical element is arranged by repeating a projection  7   b  and a recess  7   c . In this embodiment, a marker  7   a  of a projection form is provided at the center. 
   The diffractive optical element of this embodiment may be designed as a computer programmable hologram for use in an optical pickup, having three functions: splitting a beam into three components, acting as a beam splitter for separating and directing a return of light from an optical disk towards a photo IC, and providing an astigmatic difference for detection of focusing error. For example, the diffractive optical element may be made of an ARTON resin commercially available from JSR as described with Embodiment 2. 
     FIGS. 19A and 19B  are cross sectional views illustrating steps of fabricating a hologram unit with the diffractive optical element shown in  FIGS. 17 and 18 . 
   As shown in  FIG. 19A , the process starts with mounting a semiconductor laser  32  at a specific position on a photo IC  31 . This step for accurate positioning may be conducted by a common die bonding technique. The photo IC on which the semiconductor laser is mounted is then bonded by a silver paste to a lead frame  33 . The positioning at this step may be assisted by a marker provided as the reference on the lead frame  33 . 
   The resultant lead frame  33  is then placed on the stage of a microscope  14  as shown in  FIG. 19A . At the time, the emitting point of the semiconductor laser  32  is used as a marker for aligning with the center in a scale  14   a  of the microscope  14 . 
   This is followed by placing the diffractive optical element  7  on the lead frame  33  using a vacuum collet holding its sides and adjusting the height of the stage of the microscope  14  so that the marker  7   a  of the diffractive optical element  7  is clearly viewed. Then, while the lead frame  33  and the microscope  14  remain held at the position, the diffractive optical element  7  is adjusted with its horizontal position. More particularly, using the scale  14   a  in the microscope  14 , the marker  7   a  of the diffractive optical element  7  is accurately positioned to the center. Then, the diffractive optical element  7  at the position is joined by adhesive to the lead frame  33 . 
   By the foregoing steps, the diffractive optical element of this embodiment can be assembled together with the semiconductor laser and the photo IC to construct the hologram unit. 
   Embodiment 10 
     FIG. 21  is a schematic cross sectional view showing a projector as an optical equipment according to a further embodiment of the present invention. The projector  40  shown in  FIG. 21  employs an achromatic system  44  similar to that of Embodiment 2 of which the manufacturing steps are shown in  FIGS. 4A to 4D . In the projector  40  of this embodiment, light emitted from an illuminating lamp  41  is passed through an illumination lens  42 , modified by a liquid crystal display (LCD)  43  which produces an optical image, and projected by the optical system  44  on a screen. 
   The lens diameter of the optical system  44  in this embodiment is 50 mm. The marker  1   a  of the lens  1  and the marker  15   a  of another lens  15  in the optical system  44  both are 200 μm in the effective size. Assuming that the projector of this embodiment produces an image of the S/VHS video format at substantially 46 dB of S/N ratio (at 200× enlargement), the diameter of each marker may be 1/D, namely 3.6 mm, or smaller where D is the dynamic range of the video signal. However, the effective size in this embodiment is set to 200 μm because it is visible through an optical microscope. 
   Embodiment 11 
     FIG. 22  is a schematic cross sectional view showing an optical transceiver module for optical fiber communications as an optical equipment according to the present invention. The optical transceiver module  50  for optical fiber communications of this embodiment comprises a light-emitting device  51 , a photodetector  52 , and a wavelength selector filter  55  assembled in a housing  59 . A lens  53  is provided between the wavelength selector filter  55  and the light-emitting device  51  while another lens  54  is provided between the wavelength selector filter  55  and the photodetector  52 . The housing  59  is connected with one end of a fiber optic  56 . The light-emitting device  51  and the lens  53  are mounted on a frame  57  which is anchored to the inner side of the housing  59 . Similarly, the photodetector  52  and the lens  54  are mounted on another frame  58  which is anchored to the inner side of the housing  59 . 
   The lens  53  has a marker  53   a  provided on the center of an effective optical surface thereof. The lens  54  has a marker  54   a  provided on the center of an effective optical surface thereof. The wavelength selector filter  55  has a marker  55   a  provided on the center of an effective optical surface thereof. 
   In action, light emitted from the light-emitting device  51  is passed through the lens  53  and received by the wavelength selector filter  55  where its wavelength is allowed to advance to the one end of the fiber optic  56 . This allows the light emitted from the light-emitting device  51  to be passed to the one end of the fiber optic  56  for transmission of its signal further over the fiber optic  56 . 
   Light received at the one end of the fiber optic  56  in the optical transceiver module  50  is directed to the wavelength selector filter  55  where its wavelength is not transmitted straight but reflected. A reflection of the wavelength from the wavelength selector filter  55  is then passed through the lens  54  and received by the photodetector  52 . This allows the light from the one end of the fiber optic  56  to be received by the photodetector  52  where its signal is demodulated. 
   Both the lenses  53  and  54  in the optical transceiver module  50  of this embodiment is 1 mm in the diameter. The markers  53   a  and the  54   a  of the two lenses  53  and  54  are 200 μm in the effective size. Also, the effective size of the marker  55   a  provided on the wavelength selector filter  55  is 200 μm. The optical transceiver module  50  of this embodiment can hence conduct the action of transmitting and receiving optical signals over the fiber optic  56  without being interrupted by the markers  53   a ,  54   a , and  55   a.    
     FIGS. 23A to 23E  are schematic cross sectional views showing steps of manufacturing the optical transceiver module  50  of the embodiment shown in  FIG. 22 . 
   As shown in  FIG. 23A , the action starts with positioning the light-emitting device  51  to a predetermined location on the frame  57  with the use of an optical microscope  14 . The positioning is made by adjusting a pattern of electrode provided on the light-emitting device  51  to the scale  14   a  in the viewing field of the optical microscope  14 . 
   This is followed by mounting the lens  53  above the frame  57  as shown in  FIG. 23B . The mounting is made by adjusting the marker  53   a  of the lens  53  to the light-emitting device  51  for correct positioning. More particularly, the light-emitting device  51  is aligned with the lens  53  so that its electrode pattern is used as a marker. 
   Then, the frame  57  carrying the lens  53  and the light-emitting device  51  is installed at a predetermined position in the housing  59 , as shown in  FIG. 23C . The wavelength selector filter  55  (bandpass filter) is mounted at an angle of 45 degrees in the housing  59 . More specifically, for positioning and joining the frame  57  to the housing  59 , the marker  55   a  of the wavelength selector filter  55 , and the marker  53   a  of the lens  53 , and the electrode pattern of the light-emitting device  51  are aligned straight along one line before bonding the frame  57  to the inner side of the housing  59 . The bonding may be implemented with not only an adhesive but also any applicable technique such as laser spot welding. 
   This is followed by orientating the housing  59  so that the wavelength selector filter  55  is viewed through an opening  59   a  provided in the housing  59 , positioning the fiber optic  56  so that its distal end is viewed through reflection over the wavelength selector filter  55 , and joining the distal end of the optic fiber  56  to the housing  59  by an adhesive or any applicable means, as shown in  FIG. 23D . More particularly, light is conveyed over the fiber optic  56 , reflected by the wavelength selector filter  55 , and aligned with the marker  55   a  of the wavelength selector filter  55  while being monitored with the optical microscope  14  for correctly positioning the fiber optic  56  in relation to the housing  59 . 
   Then, as shown in  FIG. 23E , the photodetector  52  and the lens  54  are mounted to the housing  59 . More particularly, like the light-emitting device  51  and the lens  53  mounted by the manner shown in  FIGS. 23A and 23B , the photodetector  52  and the lens  54  are positioned and mounted to the frame  58  which is in turn fitted into the opening  59   a  provided in the housing  59 . For positioning and joining the frame  58  to the housing  59 , the light marker  55   a  of the wavelength selector filter  55 , the maker  54   a  of the lens  54 , and the electrode pattern as a marker of the photodetector  52  are aligned straight along one line. Then, the frame  58  is secured to the housing  59  by an adhesive or any applicable means. 
   As set forth above, the light-emitting device  51 , the photodetector  52 , the lens  53 , the another lens  54 , the wavelength selector filter  55 , and the one end of the fiber optic  56  are correctly positioned and assembled to the optical transceiver module  50 .