Abstract:
Light emitted from a light source such as LED and reflected by a fingertip is guided by a cover member onto a light receiving surface of an imaging element. A second resin part is provided that is in contact with the cover member and a resin molded part sealing the imaging element. The reflected light guided by the cover member is made to reach the light receiving surface via the second resin part and the resin molded part, traveling along a path spaced apart from an air layer.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an optical pointing device and particularly to an optical pointing device adapted for installation in portable information terminals such as cellular phones. The present invention also relates to electronic equipment having the optical pointing device. 
       BACKGROUND ART 
       [0002]    Portable information terminals such as cellular phones and PDAs (Personal Digital Assistants) have conventionally employed user interfaces using keypads, which are composed of a plurality of buttons for input of numbers and characters and direction buttons. 
         [0003]    In recent years, display units of portable information terminals have been made capable of displaying graphics and usable in two-dimensional manner. In nowadays when functions of portable information terminals are brought near to those of computers with operations of the terminals made complex, methods of performing operations for desired functions with use of the menu keys and other function keys as direction keys have been becoming difficult to employ as a method of input into such portable information terminals because the operations cannot be performed easily. Accordingly, demands have been increasing for pointing devices that can be operated like mice and touch pads used in computers. 
         [0004]    In such a background, there has been proposed a method of extracting change in a contact surface by observing, by an imaging element, a pattern of a fingertip or the like in contact with a pointing device. There has been also proposed a method of converting a motion of a fingertip into input signals by illuminating a contact surface with a light source, imaging a pattern of the contact surface on an imaging element by lenses, and detecting change in the pattern. 
         [0005]    For instance, such a pointing device is disclosed in WO 2006/011711 A1 (Patent Literature 1). 
         [0006]    The pointing device has a cover glass, a light source part, and a light receiving part, and the light source part is composed of a light source and a light source guide. Light emitted from the light source is reflected at a specified angle and is then projected onto the cover glass. The light projected onto the cover glass and having penetrated an upper surface of the cover glass is reflected by a surface of a finger. The light reflected by the surface of the finger penetrates a back surface and is projected onto the light receiving part. The light receiving part is composed of a reflecting mirror, a condenser lens and an optical image sensor. The light reflected by the reflecting mirror is imaged by the condenser lens so as to be provided to the optical image sensor. As the optical pointing device, there are proposed a device filled with air as medium between the optical components and a device employing an optical waveguide for minimizing the loss of the light therebetween. 
         [0007]    Another optical pointing device is disclosed in WO 2006/019218 A1 (Patent Literature 2). 
         [0008]    The optical pointing device has a first waveguide, a second waveguide, an image sensor, a cover glass, and a light source part. The first waveguide has a first reflecting surface and a first planoconvex lens that form a single body, and the second waveguide has a second planoconvex lens and a second reflecting surface that form a single body. 
         [0009]    Light emitted from the light source is projected onto an object and is reflected by the object. The light reflected by the object is refracted by the first reflecting surface and the refracted light is then condensed while passing through the first and second planoconvex lenses. The light having passed through the first and second planoconvex lenses is refracted by the second reflecting surface and is imaged on the image sensor. Spaces between the optical components are filled with air as medium. 
         [0010]    Still another optical pointing device is disclosed in WO 2005/088435 A1 (Patent Literature 3). 
         [0011]    The optical pointing device is composed of a light source for emitting light to an object, an object plane for receiving the light emitted from the light source, an optical lens for reflecting an image from an image acquisition surface, and an optical sensor for receiving the image reflected from the optical lens and converting the image into an electrical signal. Spaces between the components are filled with air as medium. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         Patent Literature 1: WO 2006/011711 A1 
         Patent Literature 2: WO 2006/019218 A1 
         Patent Literature 3: WO 2005/088435 A1 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0015]    The inventor found out that the conventional optical pointing devices may cause deterioration in optical properties resulting from the loss of light and/or may fail to satisfactorily detect displacement of a finger. 
         [0016]    The inventor also found out that these problems are caused by imaging optical systems of the conventional optical pointing devices making use of air layers between the optical components. In the conventional devices, the light is refracted because of difference between refractive indices of the components and a refractive index of air. Accordingly, variation in gaps between the components that is caused by variation in assembly, use for long time, impact from the exterior provided by vibrations or the like, etc. may cause the loss of the light, which may deteriorate the optical properties. This may make it impossible to satisfactorily detect displacement of the finger. Additionally, deposit of dust, foreign matter, and/or the like in the gaps may also deteriorate the optical properties. 
         [0017]    An object of the invention is to provide an optical pointing device and electronic equipment that have optical properties resistant to deterioration and that are excellent in product quality. 
       Solution to Problem 
       [0018]    In order to solve the problem, an optical pointing device according to an aspect of the present invention comprises a light source for irradiating an object; a light guide member for guiding light emitted from the light source and reflected by the object; an imaging element having a light receiving surface for receiving the light guided by the light guide member; a first resin part sealing the imaging element; and a second resin part in contact with the light guide member and the first resin part such that the light guided by the light guide member reaches the light receiving surface via the second resin part and the first resin part. 
         [0019]    According to the invention, the light emitted from the light source, reflected by the object, and guided by the light guide member reaches the light receiving surface via the second resin part and the first resin part and is thus prevented from coming into contact with any air layers in a path from the light guide member to the light receiving surface. Thus prevented are refraction of the light that may be caused by difference between refractive indices of the components and a refractive index of air, variation in gaps between the components that may be caused by variation in assembly, use for long time, impact from the exterior provided by vibrations or the like, etc., and deterioration in optical properties that may be caused by loss of the light. Additionally prevented is deterioration in the optical properties that may be caused by deposit of dust, foreign matter, and/or the like in the gaps. Therefore, the optical properties resist being deteriorated and displacement of a finger can satisfactorily be detected. 
         [0020]    According to the invention, the prevention of the variation that might be caused by the gaps between the components ensures excellent product quality, increases a yield, and improves productivity. 
         [0021]    In one embodiment, the first resin part has a recess on a side thereof facing the light guide member, and the second resin part fills the recess. 
         [0022]    According to the embodiment, the first resin part having the recess on the side thereof facing the light guide member and the second resin part filling the recess permit a thickness of a product to be reduced. Thus a thin optical pointing device can be provided. 
         [0023]    According to the embodiment, because a thickness of the second resin part can be considered to be equivalent to a depth of the recess, formation of the recess with high precision in advance ensures accurate adjustment of the thickness of the second resin part, remarkable improvement in product quality, and excellent optical properties. 
         [0024]    In one embodiment, the recess opens in a direction or directions generally perpendicular to a direction of a normal line of the light receiving surface. 
         [0025]    According to the embodiment, the recess opens in the direction(s) generally perpendicular to the direction of the normal line of the light receiving surface. When the recess is filled with the second resin part, therefore, excess resin can be made to escape to outside through the opening(s) of the recess. Accordingly, a quantity of the resin in the second resin part can easily be controlled and application of the resin can be stabilized. 
         [0026]    Electronic equipment according to another aspect of the present invention comprises the above-described optical pointing device of the invention. 
         [0027]    According to the invention, the provision of the optical pointing device of the invention ensures remarkable improvement in operability and quality retainability for an operation part. 
       ADVANTAGEOUS EFFECTS OF INVENTION 
       [0028]    According to the optical pointing device of the invention, in the optical path for imaging light reflected from an object on the imaging element, the reflected light reaches the imaging element without passing through any air layers. Thus the reflected light reaches the imaging element without refraction in air layers. Additionally, deposit of foreign matter such as dust between the optical components is prevented. Accordingly, variation of individual difference that might be caused by contact of the reflected light with air layers is prevented, so that productivity and product quality can remarkably be improved. 
         [0029]    According to the optical pointing device of one embodiment, the first resin part having the recess on a surface thereof on the side of the light guide member and the second resin part filling the recess permit the second resin part to be easily and reliably brought into contact with both the light guide member and the first resin part. In addition, the thickness of the second resin part can accurately be controlled and can be reduced, so that reduction in thickness and attainment of compactness can be effected. Besides, strength of the optical pointing device itself against external pressures can be increased. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0030]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not intended to limit the present invention, and wherein: 
           [0031]      FIG. 1  is a schematic section for illustrating an optical pointing device in accordance with a first embodiment of the invention; 
           [0032]      FIG. 2A  is an enlarged schematic view of an area including a joint part between a resin molded part on an imaging element and a cover member in the optical pointing device of the embodiment; 
           [0033]      FIG. 2B  is an enlarged schematic view of an area including a joint part between a resin molded part on an imaging element and a cover member in a conventional optical pointing device; 
           [0034]      FIG. 3A  is a schematic section of an optical pointing device in accordance with a second embodiment of the invention; 
           [0035]      FIG. 3B  is a perspective view of a resin molded part, as seen from a cover member side, on an imaging element in the optical pointing device in accordance with the second embodiment; 
           [0036]      FIG. 4A  is a schematic section of an optical pointing device in accordance with a third embodiment of the invention; 
           [0037]      FIG. 4B  is a perspective view of a resin molded part, as seen from a cover member side, on an imaging element in the optical pointing device in accordance with the third embodiment; 
           [0038]      FIG. 5A  is a front view of a cellular phone in accordance with a fourth embodiment of the invention; 
           [0039]      FIG. 5B  is a rear elevation of the cellular phone of the fourth embodiment; and 
           [0040]      FIG. 5C  is a side view of the cellular phone of the fourth embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0041]    Hereinbelow, embodiments of the invention will be described with reference to examples of optical pointing devices employing an LED as a light source module. The invention, however, is not limited to configurations of the embodiments below. 
       First Embodiment 
       [0042]      FIG. 1  is a schematic section of an optical pointing device in accordance with a first embodiment of the invention. 
         [0043]    The optical pointing device has a circuit board  21 , an LED  16  as an example of a light source, a light source side resin molded part  20 , a cover member  24  as an example of a light guide member, an imaging element  15 , a resin molded part  40  as a first resin part, and a second resin part  25 . 
         [0044]    The LED  16  irradiates a fingertip  10  as an object. The LED  16  is placed under the cover member  24  and is sealed with the light source side resin molded part  20 . The cover member  24  has a contact surface  11 . The contact surface  11  is placed opposite to the LED  16  with respect to the cover member  24 . A back surface part  13  of the cover member  24  that resides in a direction of emission of light from the LED  16  so as to overlie the LED  16  is slanted with respect to an optical axis M of light emitted from the LED  16 , in the section of  FIG. 1 , so as to form a slope. 
         [0045]    The light emitted from the LED  16  penetrates the back surface part  13  of the cover member  24  while being refracted and thereafter irradiates the contact surface  11  of the cover member  24  from a direction slanted obliquely with respect to the optical axis M of the light emitted from the LED  16 . 
         [0046]    In operation, the fingertip  10  that is the object is in contact with the contact surface  11 . The light projected onto the fingertip  10  from the direction slanted with respect to the optical axis M is reflected and scattered by a back surface of the fingertip  10 . For the sake of better understanding of a state of the finger with respect to the optical pointing device, the fingertip  10  is depicted in  FIG. 1  on a scale smaller than the real in relation to the optical pointing device. 
         [0047]    An image of the fingertip  10  is captured from the contact surface  11  that is a top surface, with respect to a vertical direction, of a prism part  12  serving as a ray bending element of the cover member  24 . The image of the finger that is incident on the prism part  12  undergoes total reflection on the back surface (slope)  13 , and then reflection on a top surface  17  of the cover member  24 , on a reflecting lens  14 , which is an imaging element, on the top surface  17  of the cover, on a bottom surface  18  thereof, and on the top surface  17 , and then passes through the second resin part  25  and the resin molded part  40 , and finally is focused on the imaging element  15 . The focused image of the fingertip  10  is captured as image data. 
         [0048]    The imaging element  15  is sealed with the resin molded part  40 . The second resin  25  is in contact with both the cover member  24  and the resin molded part  40 . In other words, there is no air layer between the second resin  25  and the cover member  24  and there is no air layer between the second resin  25  and the resin molded part  40 . Thus the image is focused on the imaging element  15  without being refracted greatly. 
         [0049]    The image focused on the imaging element  15  is captured as image data into a DSP (Digital Signal Processor) not shown. The imaging element  15  is an image sensor such as a CMOS image sensor or a CCD sensor, which continues picking up images of the contact surface  11  at uniform intervals. Once the fingertip  10  as the object is moved, an image thereof that is picked up is shifted by a given amount from an image that was picked up immediately before. The DSP compares amounts of the shift of the same portion of the image and thereby determines an amount and a direction of movement of the fingertip  10 . More specifically, the image data obtained from the imaging element  15  is subjected to image processing so that movement of a fingerprint on the fingertip  10  reflected in the contact surface  11  is extracted and that the amount and the direction of the movement of the fingertip  10  is determined. 
         [0050]    For the cover member  24 , polycarbonate resin of visible-light absorbing type is preferably used. Epoxy- or silicone-based resin can preferably be used for the light source side resin molded part  20  and the resin molded part  40  that seal the LED  16  and the imaging element  15 , respectively. For means for the sealing can be used molding such as typical transfer molding, injection molding, and potting. Material by which light having wavelengths other than an emission wavelength can be cut off is preferably used for components that the emitted light penetrates because the material provides countermeasures against disturbance light, stray light and the like. Material of the second resin part  25  for eliminating the air layer is preferably capable of cutting off light having wavelengths other than an LED emission wavelength and achieving high degree of adherence to the cover member  24  and the resin molded part  40 . As the material, epoxy-based or silicone-based resin can preferably be used. The second resin part  25  preferably employs material having a refractive index as close to refractive indices of the cover member  24  and the resin molded part  40  as possible. 
         [0051]      FIG. 2A  is an enlarged schematic view of an area including a joint part between the resin molded part  40  on the imaging element  15  and the cover member  24  in the optical pointing device of the embodiment.  FIG. 2B  is an enlarged schematic view of an area including a joint part between a resin molded part  440  on an imaging element  41   v   5  and a cover member  424  in a conventional optical pointing device. 
         [0052]    Referring to  FIG. 2B , in which no resin is applied between the cover member  424  and the resin molded part  440  sealing the imaging element  415 , refraction of reflected light is caused by a difference in refractive index between the cover member  424  and air and a difference in refractive index between the resin molded part  440  and air. The wider a gap therebetween is, accordingly, the more difficult it is to transmit correct optical signals to the imaging element  415 . That is, malfunction of the optical pointing device may be caused by occurrence of the gap resulting from variation on occasion of assembly, external pressures, vibrations or the like. The malfunction may also be caused by dust, foreign matter, and/or the like, which are prone to come into the gap. 
         [0053]    In contrast to that, the present invention shown in  FIG. 2A  has a configuration in which a part corresponding to the gap is occupied by the resin molded part  25  as the second resin part and which is thus resistant to occurrence of a gap. Therefore, the invention reduces the refraction of the reflected light, and is more resistant to malfunction of the optical pointing device than the configuration with the air layer, even if a distance in the gap is increased. 
         [0054]    In addition, the second resin part  25  makes it possible to bond the cover member  24  to the resin molded part  40  therethrough while eliminating the air layer. This results in provision of the optical pointing device that has an increased strength against external pressures and that yields excellent results in environmental tests such as heat cycle test. 
       Second Embodiment 
       [0055]      FIG. 3A  is a schematic section of an optical pointing device in accordance with a second embodiment of the invention.  FIG. 3B  is a perspective view of a resin molded part  140 , as seen from a cover member side, on an imaging element in the optical pointing device in accordance with the second embodiment. 
         [0056]    In the second embodiment, as shown in  FIG. 3A , a recess (difference in level)  155  is formed on a portion of a surface facing the cover member  124  of the resin molded part  140  as a first resin part sealing the imaging element  115 , and is filled with a second resin part  125 . 
         [0057]    According to the second embodiment, a thickness of resin of the second resin part  125  can easily be set equal to a depth of the recess  155 . Therefore, the second resin part  125  can easily be formed into a desired shape, and optical properties can be made excellent. 
         [0058]    Absence of the recess  155  might cause the second resin part to be interposed and pressed between the cover member and the resin molded part and to escape to outside. This might incur a possibility of occurrence of air layers between the cover member and the resin molded part, variation in the thickness of resin of the second resin part, and/or the like, which would make the optical properties inadequate. 
       Third Embodiment 
       [0059]      FIG. 4A  is a schematic section of an optical pointing device in accordance with a third embodiment of the invention.  FIG. 4B  is a perspective view of a resin molded part, as seen from a cover member side, on an imaging element in the optical pointing device in accordance with the third embodiment. 
         [0060]    In the third embodiment, a recess (difference in level)  255  is formed on a portion of a surface facing the cover member  224  of the resin molded part  240  as a first resin part sealing the imaging element  215 . As shown in  FIG. 4B , the recess  255  opens in three directions out of directions generally perpendicular to a direction of a normal line of a light receiving surface  269  (see  FIG. 4A ) of the imaging element  215 . That is, the recess  255  is shaped like a cross and opens on three side surfaces of the rectangular resin molded part  240 . 
         [0061]    According to the optical pointing device of the third embodiment, extending to the side surfaces of the resin molded part  240 , the recess  255  opens in the directions generally perpendicular to the direction of the normal line of the light receiving surface  269  of the imaging element  215 . When the recess  255  is filled with the second resin part  125 , therefore, excess thereof can be made to flow in directions shown by arrows A, B, and C in  FIG. 4B  and can be discharged to outside through openings  270 ,  271 , and  272 . That is, the openings  270 ,  271 , and  272  serve as flow parts for resin. Accordingly, the recess  255  can be filled with the second resin part  125  so that neither gap nor excess resin exists. Thus a quantity of the second resin can easily be controlled and the second resin part can stably be applied to the recess  255  regardless of individual difference. In the third embodiment, the recess  255  of the resin molded part  240  sealing the imaging element  215  has the three openings  270 ,  271 , and  272 . In the invention, however, the recess of the resin molded part sealing the imaging element may have one opening or two, four or more openings. 
       Fourth Embodiment 
       [0062]      FIG. 5A  is a front view of a cellular phone in accordance with a fourth embodiment of the invention, and  FIG. 5B  is a rear elevation of the cellular phone.  FIG. 5C  is a side view of the cellular phone. 
         [0063]    As shown in  FIGS. 5A and 5B , the cellular phone as the portable information terminal has a monitor side enclosure  301 , an operation side enclosure  302 , a mike part  303 , ten-keys  304 , a monitor part  305 , a speaker part  306 , and an optical pointing device  307  of the invention. 
         [0064]    The speaker part  306  and the mike part  303  are used for input and output of audio information. The monitor part  305  is used for output of video information and is used, in the fourth embodiment, also for display of information inputted from the optical pointing device  307 . 
         [0065]    In the fourth embodiment, as shown in  FIG. 5A , the optical pointing device  307  is placed above the ten-keys  304 . A manner of placement and orientation of the optical pointing device  307 , however, are not limited thereto, as a matter of course. 
         [0066]    The cellular phone of the fourth embodiment is of folding type having an upper enclosure and a lower enclosure connected to each other through hinges as shown in  FIGS. 5A through 5C . It is needless to say, however, that cellular phones in which the optical pointing device of the invention can be installed are not limited to those of folding type. Nevertheless, mainstream of cellular phones is of folding type as in the fourth embodiment and those having thicknesses not larger than 10 mm in folded state have been emerging. In consideration of portability, the thickness thereof is a critical factor. 
         [0067]    In the operation side enclosure  302  shown in  FIGS. 5B and 5C , components defining or determining a thickness thereof are the mike part  303 , the ten-keys  304 , and the optical pointing device  307 , in disregard for internal circuit boards and the like not shown. The optical pointing device  307  is the thickest of those components. Therefore, reduction in a thickness of the optical pointing device  307  is critical because that directly leads to reduction in the thickness of the cellular phone. As described with reference to  FIGS. 3A ,  3 B and  4 A,  4 B, reduction in the thickness of the optical pointing device of the invention can easily be attained. Accordingly, the cellular phone of the fourth embodiment can easily be reduced in thickness and made compact. 
         [0068]    Though the optical pointing device of the invention is installed in the cellular phone in the fourth embodiment, the optical pointing device of the invention can of course be installed not only in cellular phones but also in PDAs, personal computer system units, microwave ovens or any other electronic equipment having input devices. Also, it should be understood that the light source usable in the optical pointing device of the invention is not limited to LED but may be a light emitting device such as semiconductor laser element, other than LED. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10 : fingertip 
           11 : contact surface 
           12 : prism part 
           13 : back surface 
           14 : reflecting lens 
           15 ,  115 ,  215 ,  415 : imaging element 
           16 : LED 
           17 : top surface of a cover member 
           18 : bottom surface of the cover member 
           20 : resin molded part 
           21 : circuit board 
           24 ,  124 ,  224 ,  424 : cover member 
           25 ,  125 ,  225 : second resin part 
           40 ,  140 ,  240 ,  440 : resin molded part 
           69 ,  269 : light receiving surface 
           155 ,  255 : recess 
           270 ,  271 ,  272 : opening 
           301 : monitor side enclosure 
           302 : operation side enclosure 
           303 : mike part 
           304 : ten-keys 
           305 : monitor part 
           306 : speaker part 
           307 : optical pointing device