Abstract:
A tape cassette has a cassette case with top face, under face, front face, rear face, and a pair of right and left side face portions. A pair of supply and take-up tape containers sides is provided in the cassette case. A tape is wound around a pair of reels and contained in the pair of tape containers. A first wall portion connects the rear and right side face portion with each other and forms part of the take-up side tape container. A second wall portion connects the rear and left side face portion with each other and forms part of the supply side tape container. A first prism portion extends from the rear face portion to the right side face portion and refracts or reflects light from a light emission element of a recording and reproducing apparatus for detecting presence and absence of the tape cassette.

Description:
This application is a continuation of Ser. No. 09/588,372, filed Jun. 7, 2000, now U.S. Pat. No. 6,587,306. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a tape cassette formed of a high transparency material and having tape ends thereof detected and a tape cassette of which the presence/absence is detected. 
     2. Description of the Related Art 
     (Conventional Tape Cassette Regarding the Detection of a Tape End) 
     The applicant of the present application proposed a tape cassette, as the conventional tape cassette of this type, disclosed by Japanese Utility Model Examined Application Publication No. 63-25595. FIG. 1 is a partially-cut perspective view of the tape cassette; FIG. 2 is a plan view of a lower case portion thereof; FIG. 3 is a perspective view of part S shown in FIG. 2; FIG. 4 is a perspective view of part E of FIG. 2; and FIG. 5 is a perspective view of part F of FIG.  2 . 
     In FIGS. 1 and 2, a cassette case  1  consists of a lower case portion  2  and an upper case portion  3 . The case portions  2  and  3  are assembled with their respective junction surfaces abutting on each other. A pair of tape containers  4 ,  4  are provided in this cassette case  1 . Reels  5 ,  5  are rotatably arranged in the paired tape containers  4 ,  4 , respectively. A tape (not shown) is wound around the paired reels  5 ,  5  and constituted so that the rotation of the reels  5 ,  5  allows the traveling of the tape. Also, a cover lock container  6  is provided on one front end portion of the cassette case  1  to be surrounded by wall portions  10   d  and  10   e . A cover lock member  7  is rockably arranged in the cover lock container  6 . The cover lock member  7  locks a cover (not shown) to a closed position. While a cassette is inserted into a recording and reproducing apparatus, the position of the cover is changed to an unlocked position. 
     A light emission element insertion hole  11  is provided at the central position of the lower case  2  to be surrounded by the wall portion  10   a . While the tape cassette is being installed into the recording and reproducing apparatus, the light emission element  12  of the recording and reproducing apparatus is arranged in the light emission insertion hole  11 . The recording and reproducing apparatus is provided with a pair of right and left light reception elements  13   a  and  13   b . The paired light reception elements  13   a  and  13   b  are positioned outward of the right and left sides of the tape cassette, respectively while the tape cassette is being installed into the recording and reproducing apparatus. The tape cassette is also provided with sensor optical path holes  14   a  to  14   e  and  17   a  to  17   d  in wall portions  10   a  to  10   e  and  16   a  to  16   d , respectively, which are positioned on straight lines L1 and L2 coupling the position of the light emission element  12  with the paired right and left light reception elements  13   a , and  13   b , respectively. 
     To be specific, the light which advances from the light emission element  12  in right direction, is introduced into the tape container  4  by way of the sensor optical path hole  14   a  of the right semicylindrical wall portion  10   a  constituting the light emission element insertion hole  11  and the sensor optical path hole  14   b  of the wall portion  10   b  constituting tape container  4 . FIG. 3 shows the sensor optical path holes  14   a  and  14   b  provided in the lower case portion  2 . It is noted that sensor optical path holes (not shown) are also provided at the corresponding positions of the upper case  3 . To be exact, the holes of the upper and lower cases  2  and  3  constitute the respective sensor optical path holes. After the light which is introduced into the tape container  4  passes through the tape traveling path on which the pulled-out tape travels, the light is introduced to the outside of the tape cassette by way of the sensor optical path hole  14   c  of the wall portion  10   c  constituting the tape container  4 , the sensor optical path hole  14   d  of the wall portion  10   d  constituting the cover lock container  6  and the sensor optical path hole  14   e  of the wall portion  10   e  on the side surface of the cassette (which wall portion also serves as one constituting the cover lock container  6 ) and reaches the light reception element  13   a . FIG. 4 shows the sensor optical path holes  14   c  to  14   e  provided in the lower case portion  2 . It is noted that sensor optical path holes are also provided at the corresponding positions of the upper case portion  3  (except for the sensor optical path hole in the wall portion on the side surface of the cassette). To be exact, the holes of the upper and lower case portions  2  and  3  constitute the respective sensor optical path holes. 
     The light which advances from the light emission element  12  in left direction, is introduced into the tape container  4  by way of the sensor optical path hole  17   a  of the left semicylindrical wall portion  16   a  and the sensor optical path hole  17   b  of the wall portion  16   b  constituting the tape container  4 . FIG. 3 shows the sensor optical path holes  17   a  and  17   b  provided in the lower case portion  2 . It is noted that sensor optical holes (not shown) are also provided at the corresponding positions of the upper case  3 . To be exact, the holes of the upper and lower case portions  2  and  3  constitute the respective sensor optical path holes. After the light which is introduced into the tape container  4  passes through a tape traveling path on which the pulled-out tape travels, the light is introduced to the outside of the tape cassette by way of the sensor optical path hole  17   c  of the wall portion  16   c  constituting the tape container  4 , the sensor optical path hole  18   a  of a tape pad  18  which is a transparent member and the sensor optical path hole  17   d  of the wall portion  16   d  on the side surface of the cassette and reaches the light reception element  13   b . FIG. 5 shows the sensor optical path holes  17   c  and  17   d  and the optical path hole  18   a  of a tape pad  18  provided in the lower case portion  2 . It is noted that sensor optical path holes are also provided at the corresponding positions of the upper case portion  3 , respectively (except for the optical path hole in the wall portion on the side surface of the cassette). To be exact, the holes of the upper and lower case portions  2  and  3  constitute the respective sensor optical path holes. 
     The wall portions  10   c  to  10   e ,  16   a  to  16   d  and the like which constitute the sensor optical path holes  14   c  to  14   e  and  15   a  to  15   d  on the optical path for the light from the light emission element  12  which comes out of the tape container  4 , are colored with a low light reflectance color. In FIGS. 4 and 5, the colored portions of the lower case portion  2  are indicated by hatching. The corresponding portions of the upper case portion  3  are colored, as well. 
     With the above constitution, the light which advances from the light emission element  12  in right direction reaches the tape traveling path by way of the sensor optical path holes  14   a  and  14   b . If a tape on the tape traveling path is a magnetic recording layer tape part, it does not transmit light and the light does not reach the light reception element  13   a . If the tape on the tape traveling path is a high light transmittance leader tape part, it transmits light and the light reaches the light reception element  13   a  by way of the sensor optical path holes  14   c  to  14   e . Further, the light which advances from the light emission element  12  in left direction reaches the tape traveling path by way of the sensor optical path holes  17   a  and  17   b . If the tape on the tape traveling path is a magnetic recording layer tape part, it does not transmit light and the light does not reach the light reception element  13   b . If the tape on the tape traveling path is a high light transmittance leader tape part, it transmits light and the light reaches the light reception element  13   b  by way of the sensor optical path holes  17   c ,  18   a  and  17   d . Using the difference in the output voltages of the light reception elements  13   a  and  13   b  between a case where the tape on the tape traveling path is the magnetic recording layer tape part and a case where the tape is the leader tape part, it is detected whether the tape end is at a take-up side or a supply side. 
     Meanwhile, the light from the light emission element  12  contains not only components advancing toward the light reception elements  13   a  and  13   b  but also those which may be reflected by the flanges of the reels  5 , the inner surface of the cassette case  1  and the like and which may reach the light reception elements  13   a  and  13   b  without passing the tape traveling path. Further, there are cases where external light is incident on the interior of the cassette case  1  from the windows or the like on the upper surface of the tape containers  4  of the tape cassette, the incident light is reflected by the flanges of the reels  5 , the inner surface of the cassette case  1  and the like and reaches the light reception elements  13   a  and  13   b  without passing the tape traveling path. 
     Here, if the cassette case  1  itself is formed out of a low light reflectance material such as a black material, the quantity of light which reaches the light reception elements is very small. Due to this, the light reception elements  13   a  and  13   b , less likely, malfunction. Conversely, if the cassette case  1  itself is desired to be formed out of a material having high light reflectance or high transparency, the quantity of the above-stated unnecessary light which reaches the light reception elements  13   a  and  13   b  becomes disadvantageously large. 
     In spite of the above fact, according to the conventional case, portions close to the light reception elements  13   a  and  13   b  are colored with a low light reflectance color, thereby making it possible to sufficiently attenuate the unnecessary light at those positions and to prevent the light reception elements  13   a  and  13   b  from malfunctioning. In other words, it is possible to produce a colorful tape cassette without the need to consider the color of the cassette case  1  and the like. 
     (Tape Cassette Regarding the Detection of the Presence/Absence of the Tape Cassette) 
     The tape cassette is employed in various apparatuses beside the recording and reproducing apparatus. They involve, for example, an operational cassette changer for a duplicator. FIGS. 6 and 7 show an example of usage of the cassette changer. In FIGS. 6 and 7, a recording and reproducing apparatus  101  is a tape dubbing apparatus having two cassette drives and the like. A cassette changer  103  is coupled to one cassette insertion port of the recording and reproducing apparatus  101  through a coupling portion  102 . 
     The cassette changer  103  has a cassette tray  105  slidably arranged in a changer main body  104 . The cassette tray  105  is moved between a cassette reference position and the cassette delivery position of the recording and reproducing apparatus  101 . A pair of cassette stoppers  107  are provided above the cassette tray  105  so as to hold a tape cassette  106  at a cassette set position. The paired cassette stoppers  107  are moved to be apart from each other (in arrow directions shown in FIG.  6 B), whereby the tape cassette  106  drops into the cassette tray  105  while being guided by rollers  108 . 
     A cassette press arm  110  sliding along a guide rail  109  is also provided at the changer main body  104 . The cassette press arm  110  presses the side surface of the tape cassette  106 , whereby the tape cassette  106  can be moved from the cassette reference position of the cassette tray  105  to a cassette eject position (cassette position) on a storage  111 . The storage  111  is provided laterally of the cassette tray  105 . The changer main body  104  is provided with cassette presence detection means  112  for detecting whether or not the tape cassette  106  is at the cassette ejection position on the storage. 
     The cassette presence detection means  112  has a light emission portion  112   a  and a light reception portion  112   b  receiving a detected light from the light emission portion  112   a . The optical path CC of the detected light which has reached the light reception portion  112   b  from the light emission portion  112   a  is set to pass the cassette ejection position which is the cassette position. 
     Next, the function of the above-stated constitution will be described. As indicated by virtual lines shown in FIGS. 6A and 6B, the tape cassette  106  is set at the cassette position. In a start mode, the paired cassette stoppers  107  are moved to be away from each other and the tape cassette  106  drops into the cassette reference position on the cassette tray  105 . Then, the cassette tray  105  moves to the cassette delivery position of the recording and reproducing apparatus  101  and the tape cassette  106  is installed into the recording and reproducing apparatus  101 , thereby starting dubbing. When dubbing is finished, the tape cassette.  106  is ejected from the recording and reproducing apparatus  101  and returned onto the cassette tray  105 . Thereafter, the cassette tray  105  is moved to the cassette reference position and the tape cassette  106  at the cassette reference position is pressed by the cassette press arm  110  and ejected to the cassette ejection position (a state shown in FIGS.  7 A and  7 B). 
     If the next tape cassette  106  is put at the cassette set position, a start mode is selected and dubbing is executed through the same operation process stated above. If a user removes the tape cassette  106  from the cassette ejection position, detected light from the light emission portion  112   a  is not shielded by the tape cassette  106  and reaches the light reception portion  112   b . Thus, the cassette presence detection means  112  detects that the tape cassette  106  is not at the cassette ejection position and then the tape cassette  106  is ejected to the cassette ejection position through the same operation process stated above. On the other hand, if the user does not remove the tape cassette  106  completed with dubbing from the cassette ejection position, detected light from the light emission portion  112   a  is shielded by the tape cassette  106  and does not reach the light reception portion  112   b . Thus, the cassette presence detection means  112  detects that the tape cassette  106  is at the cassette ejection position, whereby even if there is a tape cassette  106  to be completed with dubbing, the tape cassette  106  is prohibited from being ejected to the cassette ejection position. 
     (Tape Cassette Regarding the Detection of a Tape End) 
     According to the above-stated conventional tape cassette, it is required to color the portions of the cassette case  1  near the light reception elements  13   a  and  13   b . Due to this, a coloring step which is quite laborious is included in processing steps, with the result that production efficiency disadvantageously, greatly deteriorates and demand for mass production cannot be disadvantageously met. 
     Further, there is demand for forming the cassette case  1  itself out of a high transparency material. In that case, if the portions of the cassette case  1  are colored with a low light reflectance color, the color disadvantageously differs from an originally intended color. 
     (Tape Cassette Regarding the Detection of Presence/Absence of the Tape Cassette) 
     If there is demand for forming the cassette case itself of the cassette  106  out of high transparency material and the tape cassette  106  is formed according to the demand, there is a possibility that a detection error occurs to the cassette presence detection means  112  described above. That is, even if the tape cassette  106  is at the cassette ejection position, the detected light from the light emission portion  112   a  transmits the cassette case and reaches the light reception portion  112   b  and the cassette presence detection means erroneously detects that the cassette is absent. If such an erroneous detection is made, the next tape cassette  106  is fed to the cassette ejection position even while the tape cassette  106  is at the cassette ejection position. As a result, the earlier tape cassette  106  drops from the storage  111  and damaged or, if the storage  111  has a drop preventive wall, a heavy load is applied to the cassette press arm  110  and the cassette changer  103  and the like are damaged. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide a tape cassette to solve the above-stated problems and capable of preventing malfunction in tape end detection irrespectively of the characteristics (color, transparency and reflectance) of a cassette case without extreme deterioration of production efficiency and capable of maintaining a color originally intended for the cassette case as much as possible if the cassette case itself is formed out of a high transparency material. 
     It is also an object of the present invention to provide a tape cassette to solve the above-stated problems and capable of preventing a cassette detection error even if a cassette case is formed out of a high transparency material. 
     To achieve the above object, there is provided a tape cassette having a pair of reels rotatably provided in a pair of tape containers, respectively, a tape being wound around the pair of reels and contained in the pair of tape containers, the tape consisting of a magnetic recording layer tape part and high light transmittance leader tape parts added to both ends of the tape, respectively, and having sensor optical path holes provided on wall portions, respectively, on a straight line coupling a position of a light emission element of a recording and reproducing apparatus with a position of a light reception element of the recording and reproducing apparatus so that light from the light emission element is introduced into the tape containers and light passing through tape running paths of the tape containers comes out of the tape containers and reaches the light reception element while the tape cassette is installed into the recording and reproducing apparatus, wherein a light shielding portion having a light shielding effect is provided around at least one of the sensor optical path hole right after the light from the light emission element comes out of one of the tape containers and next the sensor optical path hole. 
     According to the present invention, since a light shielding portion having a light shielding effect is provided around at least one of the sensor optical path hole right after the light from the light emission element comes out of one of the tape containers and next the sensor optical path hole, it suffices to provide light shielding portions around the two sensor optical path holes at most. Thus, it is possible to prevent malfunction in tape end detection irrespectively of the characteristics (color, transparency and reflectance) of the cassette case, capable of responding to the demand of mass production without greatly deteriorating production efficiency, and capable of maintaining a color originally intended for the cassette case as much as possible if the cassette case itself is formed out of a high transparency material. 
     In a preferred embodiment of the present invention, the light shielding portion is provided to have right and left widths of about not less than 1 mm from a center of an optical path coupling the position of the light emission element with the position of the light reception element by the straight line and to spread over an entire height of at least one of the wall portion right after the light from the light emission element comes out of one of the tape containers and the next wall portion. 
     According to this embodiment, it is possible to ensure preventing malfunction in tape end detection. 
     In a preferred embodiment of the present invention, the light shielding portion is formed out of a light shielding member bonded to at least one of the wall portion right after the light from the light emission element comes out of one of the tape containers and the next wall portion. 
     According to this embodiment, since it suffices to bond the light shielding members to two wall portions at most, it can be expected that production efficiency further enhances. 
     In a preferred embodiment of the present invention, the light shielding portion is constituted by forming the wall portion right after the light from the light emission element comes out of at least one of the tape containers and the next wall portion itself, out of a light shielding member to be colored with two colors when forming a cassette case. 
     According to this embodiment, since it suffices to form the cassette case to be colored with two colors, it can be expected that production efficiency further enhances. 
     In a preferred embodiment of the present invention, the light shielding portion is constituted by attaching a light shielding holder having the sensor optical path hole to at least one of the wall portion right after the light from the light emission element comes out of at least one of the tape containers and the next wall portion. 
     According to this embodiment, since it suffices to attach the light shielding holders to two wall portions at most, it can be expected that production efficiency further enhances. 
     Further, to achieve the above object, there is provided a tape cassette having a pair of reels rotatably provided in a pair of tape containers, respectively, a tape being wound around the pair of reels and contained in the pair of tape containers, the tape consisting of a magnetic recording layer tape part and high light transmittance leader tape parts added to both ends of the tape, respectively, and having sensor optical path holes provided on wall portions, respectively, on a straight line coupling a position of a light emission element of a recording and reproducing apparatus with a position of a light reception element of the recording and reproducing apparatus so that light from the light emission element is introduced into the tape containers, light passing through tape running paths of the tape containers comes out of the tape containers, passes through a cover lock container and reaches the light reception element while the tape cassette is installed into the recording and reproducing apparatus, wherein a cylindrical protrusion having a light shielding effect is provided at a cover lock member arranged in the cover lock container, and a sensor optical path hole arranged on the straight line coupling the position of the light emission element with the position of the light reception element is provided at the cylindrical protrusion while the cover lock member is at an unlock position. 
     According to the present invention, even if unnecessary light is incident on the sensor optical path hole of the cylindrical protrusion, it abuts on the inner surface of the sensor optical path hole and shielded by the absorption effect thereof. Thus, it is possible to prevent malfunction in tape end detection irrespectively of the characteristics (color, transparency and reflectance) of the cassette case, capable of responding to the demand of mass production without greatly deteriorating production efficiency, and capable of maintaining a color originally intended for the cassette case as much as possible if the cassette case itself is formed out of a high transparency material. 
     Moreover, to achieve the above object, there is provided a tape cassette having a pair of reels rotatably provided in a pair of tape containers, respectively, a tape wound around the pair of reels and contained in the pair of tape containers, the tape consisting of a magnetic recording layer tape part and high light transmittance leader tape parts added to both ends of the tape, respectively, and having sensor optical path holes provided on wall portions on a straight line coupling a position of a light emission element of a recording and reproducing apparatus with a position of a light reception element of the recording and reproducing apparatus so that light from the light emission element is introduced into the tape containers and light passing through tape running paths of the tape containers comes out of the tape containers and reaches the light reception element while the tape cassette is installed into the recording and reproducing apparatus, wherein at least one of an upper flange and a lower flange of each of the pair of reels is formed out of a reflection light attenuating material and a reflection light attenuating color. 
     According to the present invention, since unnecessary light abuts on the flange portions of the reels and shielded by the absorption effect thereof, it is possible to prevent malfunction in tape end detection irrespectively of the characteristics (color, transparency and reflectance) of the cassette case, capable of responding to the demand of mass production without greatly deteriorating production efficiency, and capable of maintaining a color originally intended for the cassette case as much as possible if the cassette case itself is formed out of a high transparency material. 
     Furthermore, to achieve the above object, there is provided a tape cassette provided with a light emission portion and a light reception portion for receiving detection light from the light emission part at an apparatus side, an optical path of the detection light reaching the light reception portion from the light emission portion set to pass a cassette position, and used with an apparatus for detecting presence and absence of the tape cassette depending on whether the detection light from the light emission portion reaches the light reception portion, wherein a cassette case is formed out of a high transparency material, and a prism portion for refracting or reflecting incident light in an emission direction in which the incident light does not reach the light reception portion is provided at a position of the cassette case on the optical path of the detection light. 
     According to the present invention, if the tape cassette is at the cassette position, the detection light from the light emission portion is refracted or totally reflected by the prism portion and does not reach the light reception portion. Thus, it is possible to prevent a cassette detection error in the tape cassette with a high transparency cassette case. 
     In a preferred embodiment of the present invention, the prism portion is formed integrally with the cassette case. 
     According to this embodiment, since the prism portion is formed simultaneously with the cassette case, the prism portion can be easily produced at low cost. In addition, compared with a case of providing a light shielding member at the position of the prism portion, this embodiment has advantages in that an assembly step is not necessary and problems such as attachment error, peeling and the like can be avoided. 
     In a preferred embodiment of the present invention, the prism portion is provided at a position of the cassette case on which the detection light emitted from the light emission portion is incident first. 
     According to this embodiment, since the distance from the prism portion to the light reception portion is long and it is possible to prevent the detection light from reaching the light reception portion even if a prism deviation angle is set small, the degree of freedom for prism design increases. 
     In addition, to achieve the above object, there is provided a tape cassette provided with a light emission portion for cassette presence and absence detection and a light reception portion for cassette presence and absence detection receiving detection light from the light emission part at an apparatus side, an optical path of the detection light reaching the light reception portion from the light emission portion set to pass a cassette position, and used with an apparatus for detecting presence and absence of the tape cassette depending on whether the detection light from the light emission portion reaches the light reception portion, and provided with a light emission portion for cassette end detection and a light reception portion for cassette end detection receiving detection light from the light emission portion at an apparatus side, and used with an apparatus for detecting presence and absence of a tape end depending on whether the detection light from the light emission portion reaches the light reception portion, wherein a light shielding member is provided on an optical path for tape end detection to block passage of unnecessary light deviated from the optical path; and the light shielding member is extended and an extended portion of the light shielding member is arranged on an optical path for cassette presence and absence detection. 
     According to the present invention, the prevention of malfunction in tape end detection is ensured for a high transparency cassette case, and further it is possible to prevent a cassette detection error without increasing the number of parts and deteriorating assemblage. 
     Further, to achieve the above object, there is provided a tape cassette used with an apparatus for detecting a tape terminal end depending on whether tape end detection light from a light emission portion reaches a light reception portion, wherein a prism portion for refracting or reflecting the tape end detection light from the light emission portion in an emission direction in which the light does not reach the light reception portion, is provided on a wall around an optical path notch through which the tape end detection light passes. 
     According to the present invention, since the tape end detection light from the light emission portion is refracted or totally reflected by the prism portion and does not reach the light reception portion, it is possible to prevent a cassette detection error in a tape cassette with a high transparency cassette case. 
     Also, to achieve the above object, there is provided a tape cassette provided with two light emission portions for cassette presence and absence detection and two light reception portions for cassette presence and absence detection receiving detection lights from the light emission portions at an apparatus side, first and second optical paths of first and second detection lights reaching the light reception portions from the light emission portions, respectively, set to pass a cassette position, and used with an apparatus for detecting presence and absence of the tape cassette depending on whether the first detection light and second detection light from the respective light emission portions reach the respective light reception portions; and provided with two light emission portions for tape end detection and two light reception portions for tape end detection receiving detection lights from the light emission portions at an apparatus side, third and fourth optical paths of third and fourth detection lights reaching the light reception portions from the light emission portions, respectively, set to pass the tape position, and used with an apparatus for detecting presence and absence of a tape end depending on whether the third detection light and fourth detection light from the light emission portions reach the respective light reception portions, wherein a cassette case is formed out of a high transparency material; prism portions for refracting or reflecting the first and second detection lights for cassette presence and absence detection in a direction in which the first detection light and second detection light do not reach the respective light reception portions, are provided at positions of the cassette case on first and second optical paths of the first and second lights for cassette presence and absence detection, respectively; and light shielding members are provided on third and fourth optical paths of third and fourth lights for tape end detection to block passage of unnecessary light deviated from the third and fourth optical paths, respectively. 
     According to the present invention, it is possible to ensure preventing malfunction in tape end detection for a high transparency cassette case and to prevent a tape cassette presence/absence detection error. 
     Moreover, to achieve the above object, there is provided a tape cassette provided with two light emission portions for cassette presence and absence detection and two light reception portions for cassette presence and absence detection receiving detection lights from the light emission portions at an apparatus side, first and second optical paths of first and second detection lights reaching the light reception portions from the light emission portions, respectively, set to pass a cassette position, and used with an apparatus for detecting presence and absence of the tape cassette depending on whether the first detection light and second detection light from the respective light emission portions reach the respective light reception portions; and provided with two light emission portions for tape end detection and two light reception portions for tape end detection receiving detection lights from the light emission portions at an apparatus side, third and fourth optical paths of third and fourth detection lights reaching the light reception portions from the light emission portions, respectively, set to pass the tape position, and used with an apparatus for detecting presence and absence of a tape end depending on whether the third detection light and fourth detection light from the light emission portions reach the respective light reception portions, wherein a cassette case is formed out of a high transparency material; a prism portion for refracting or reflecting the first detection light for cassette presence and absence detection in a direction in which the first detection light does not reach the light reception portion, is provided at a position of the cassette case on a first optical path of the first detection light; a first light shielding member is provided on a second optical path of the second detection light for cassette presence and absence detection, a second light shielding member is provided on a third optical path of the third detection light for tape end detection to block unnecessary light deviated from the third optical path; and a third light shielding member is provided on a fourth optical path of the fourth detection light for tape end detection to block unnecessary light deviated from the fourth optical path. 
     According to the present invention, it is possible to ensure preventing malfunction in tape end detection for a high transparency cassette case and to prevent a tape cassette presence/absence detection error. 
     In a preferred embodiment of the present invention, the first light shielding member is extended and an extended portion of the first light shielding member is set as the second light shielding member. 
     According to this embodiment, it is possible to reduce the number of parts and the number of assembly steps and to enhance production efficiency. 
     The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 shows prior art regarding the detection of a tape and is a partially cut perspective view of a tape cassette; 
     FIG. 2 shows prior art regarding the detection of a tape and is a plan view of a lower case portion; 
     FIG. 3 shows prior art regarding the detection of a tape and is a perspective view of part S of FIG. 2; 
     FIG. 4 shows prior art regarding the detection of a tape and is a perspective view of part E of FIG. 2; 
     FIG. 5 shows prior art regarding the detection of a tape and is a perspective view of part F of FIG. 2; 
     FIGS. 6A and 6B are a plan view and a front view, respectively showing a state in which a conventional cassette changer is used; 
     FIGS. 7A and 7B are a plan view and a front view, respectively showing a state in which a conventional cassette changer is used; 
     FIG. 8A shows the first embodiment of the present invention and is a plan view of a lower case portion; 
     FIG. 8B is a perspective view of part E of FIG. 8A; 
     FIG. 9 shows the first embodiment of the present invention and is a schematically longitudinal sectional view of a tape cassette; 
     FIG. 10 is a perspective view of the important parts of a lower case portion in the second embodiment according to the present invention; 
     FIG. 11 is a perspective view of the important parts of a lower case portion in the third embodiment according to the present invention; 
     FIG. 12 is a perspective view of the important parts of a lower case portion in the fourth embodiment according to the present invention; 
     FIG. 13 is a perspective view of the important parts of a lower case portion in the fifth embodiment according to the present invention; 
     FIG. 14 show the fifth embodiment of the present invention and is a perspective view of a light shielding holder; 
     FIG. 15 shows the sixth embodiment of the present invention and is a perspective view of the important parts of a lower case portion; 
     FIGS. 16A and 16B shows the seventh embodiment of the present invention and are a side view and a front view of a cover lock member, respectively; 
     FIG. 17A is a sensor output characteristic view while the white (transparent) cassette case is used and the right and left widths (light shielding range widths) of the light shielding portion are changed in the first to sixth embodiments; 
     FIG. 17B shows the right and left widths (light shielding range widths) of the light shielding portion; 
     FIG. 18 shows a list of malfunction evaluation results of the first and second embodiments and the comparison examples; 
     FIG. 19 shows the eighth embodiment of the present invention and is a schematic cross-sectional view of a tape cassette; 
     FIG. 20 shows the eighth embodiment of the present invention and is a perspective view of the important parts (corresponding to part F of FIG. 8A) of a lower case portion; 
     FIG. 21 shows the ninth embodiment of the present invention and is a perspective view of the important parts of the lower case portion; 
     FIG. 22 shows the tenth embodiment of the present invention and is a perspective view of the important parts of the lower case portion; 
     FIG. 23 shows the tenth embodiment of the present invention and is a perspective view of a tape pad; 
     FIG. 24 shows the eleventh embodiment of the present invention and is a perspective view of the important parts of the lower case portion; 
     FIG. 25 shows the twelfth embodiment of the present invention and is a perspective view of the important parts of the lower case portion; 
     FIG. 26 shows a list of malfunction evaluation results of the eighth to eleventh embodiments and the comparison examples; 
     FIG. 27 shows the thirteenth embodiment of the present invention and is a schematically cross-sectional view of a tape cassette; 
     FIGS. 28A to  28 C show the fourteenth embodiment of the present invention, wherein FIG. 28A is a plan view of a tape cassette from which only the upper surface portion of a cassette case is removed, FIG. 28B is a back view of the tape cassette and FIG. 28C is a side view of the tape cassette; 
     FIG. 29 shows the fourteenth embodiment of the present invention and shows the part of MM of FIG. 28A in partial enlargement view; 
     FIG. 30 shows the fourteenth embodiment of the present invention and shows the optical path of detection light incident on the prism portion on the side surface portion; 
     FIG. 31 shows the fourteenth embodiment of the present invention and shows the optical path of detection light incident on the prism portion on the back surface portion; 
     FIG. 32 shows the fifteenth embodiment of the present invention and shows prism portions arranged in part MM of FIG. 28A in partial enlargement view; 
     FIGS. 33A to  33 C show the sixteenth embodiment of the present invention, wherein FIG. 33A is a plan view of a tape cassette from which only the upper surface portion of a cassette case is removed, FIG. 33B is a back view of the tape cassette and FIG. 33C is a side view of the tape cassette; 
     FIG. 34 shows the sixteenth embodiment of the present invention and is a partial enlargement view of part NN of FIG. 33C; 
     FIG. 35 show the sixteenth embodiment of the present invention and show the optical path of detection light incident on the prism portion on the bottom portion; 
     FIGS. 36A to  36 C show the seventeenth embodiment of the present invention, wherein FIG. 36A is a plan view of a tape cassette from which only the upper surface portion of a cassette case is removed, FIG. 36B is a back view of the tape cassette and FIG. 36C is a side view of the tape cassette; 
     FIG. 37 shows the eighteenth embodiment of the present invention and a partial plan view of a tape cassette from which only the upper surface portion of a cassette case is removed; 
     FIG. 38 shows the eighteenth embodiment of the present invention and is a perspective view of important parts showing a state before the light shielding member is attached; 
     FIG. 39 shows the eighteenth embodiment of the present invention and is a perspective view of important parts showing a state the light shielding member has been attached; 
     FIG. 40 shows the nineteenth embodiment of the present invention and a plan view of a tape cassette from which only the upper surface portion of a cassette case is removed; 
     FIGS. 41A to  41 C show the nineteenth embodiment of the present invention, wherein FIG. 41A is an explanatory view of the surrounding of the optical path notch of the cassette case of the tape cassette, FIG. 41B shows the optical path of tape end detection light if the prism portion is provided and FIG. 41C shows the optical path of tape end detection light if the prism portion is not provided. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiments of the present invention will be described hereinafter with reference to the accompanying drawings. 
     (Embodiments of a Tape Cassette Regarding the Detection of a Tape End) 
     First to seventh embodiments concern the constitution of a tape cassette relating to the detection of a tape end at a take-up side (tape winding side); eighth to twelfth embodiments concern the constitution thereof relating to the detection of a tape end at a supply side (tape supply side); and the thirteenth embodiment concerns the constitution thereof relating to the detection of tape ends at both the take-up side and the supply side, i.e., the constitution of the tape cassette which deals with both the take-up side and the supply side. 
     FIGS. 8A,  8 B and  9  show the first embodiment of the present invention. Specifically, FIG. 8A is a plan view of a lower case portion  2 , FIG. 8B is a perspective view of part E of FIG.  8 A and FIG. 9 is a schematically longitudinal sectional view of the tape cassette. In FIGS. 8A,  8 B and  9 , the same constituent elements as those described in the conventional tape cassette regarding the detection of a tape end will not described herein to avoid repetitive description and only different constituent elements will be described. It is noted that the same constituent elements as those of the conventional tape cassette regarding the detection of the tape end are denoted by the same reference symbols to help understand the invention. The same thing is true for the other drawings. 
     In the first embodiment, a portion close to a light reception element  13   a  is not colored with a low light reflectance color unlike the conventional tape cassette but a light shielding member  20 , serving as a light shielding portion  15 , is bonded around a sensor optical path hole  14   c  just after light from a light emission element  12  comes out of a tape container  4  at a right side (take-up side), as shown in FIG.  8 B. The light shielding member  20  is formed out of a light shielding material with a light shielding color and a sensor optical path hole  21  is provided on a portion corresponding to a sensor optical light hole  14   c.    
     The light shielding member  20  is provided to have right and left widths D each of not less than about 1 mm from the center of an optical path coupling the position of the light emission element  12  with that of the light reception element  13   a  by a straight line L1 and to spread over the entire height of a wall portion  10   c . The reason for setting each of the right and left widths D at not less than about 1 mm will be described later in detail. 
     Although FIG. 8B only illustrates the lower case portion  2 , an upper case portion  3  has a wall portion (not shown) at an opposite position to that of the wall portion  10   c , as well. The entire height of the wall portion  10   c  means a total of the heights of the upper and lower case portions  2  and  3 . Although the following drawings illustrate only the lower case portion  2 , too, the upper case portion  3  has wall portions (not shown) at opposite positions, respectively. If the wall portions are processed, the same process is conducted thereto as that of the wall portions of the lower case portion. Further, the light shielding portion  15  to be described in the second and the following embodiments is also provided to have right and left widths D each of about not less than 1 mm from the center of an optical path coupling the position of the light emission element  12  with that of the light reception element  13   a  by the straight light L1 and to spread over the entire height of the wall portion  10   c.    
     With the above-stated constitution, light  22  advancing straight to the light reception element  13   a , among the light from the light reception element  12 , reaches a tape traveling path by way of sensor optical path holes  14   a  and  14   b . If a tape T on the tape traveling path is a magnetic recording layer tape part, the tape T does not transmit light and the light does not, therefore, reach the light reception element  13   a . If the tape T is a high light transmittance leader tape part, it transmits light and the light reaches the light reception element  13   a  by way of sensor optical path holes  14   c  to  14   e.    
     Further, among light from the light emission element  12 , unnecessary light  23  which does not advance straight to the light reception element  13   a  and unnecessary light  23  incident into the cassette case  1  from a window or the like on the upper surface of the tape container  4  of the tape cassette may be reflected by the upper and lower flanges  5   a  and  5   b  of a reel  5 , the inner surface of the cassette case  1  and the like and directed toward the light reception element  13   a  without passing the tape traveling path. Since most of the unnecessary light  23  which may possibly reach the light reception element  13   a  is abutted against the light shielding member  20  and then shielded by the member  20 , the ratio of the unnecessary light which reaches the light reception element  13   a  is very low. 
     Accordingly, it is possible to prevent malfunction in the detection of a tape end irrespectively of the characteristics (color, transparency and reflectance) of the cassette case  1 . In the production of a tape cassette, it suffices to simply bond the light shielding member  20  to the wall portion  10   c . Unlike the conventional tape cassette, therefore, the production efficiency of the tape cassette in this embodiment does not deteriorate greatly. Furthermore, the light shielding member  20  may be bonded to only one wall portion  10   c  which is not on the outer surface of the cassette case  1 . Therefore, if the cassette case itself is made of a high transparency material, a color originally intended for the cassette case  1  can be maintained as much as possible. 
     FIG. 10 is a perspective view of the important parts of the lower case portion  2  in the second embodiment according to the present invention (corresponding to FIG.  8 B). In the second embodiment shown in FIG. 10, a light shielding member  20  serving as a light shielding portion  15  is bonded not to a portion just after light from a light emission element  12  comes out of a tape container  4  but bonded around the next sensor optical path hole  14   d . In FIG. 10, the light shielding member  20  is shown bonded to a wall portion  10   d  at a wall portion  10   c  side. Needless to say, the member  20  may be bonded to a wall portion  10   d  at a wall portion  10   e  side. The remaining constituent elements are the same as those in the first embodiment, which description will not be, therefore, given herein. 
     It can be expected that the second embodiment provides the same function and advantages as those of the first embodiment. 
     As a modification of the first and second embodiments, the light shielding member  20  may be bonded around the sensor optical path hole  14   c  right after light from the light emission element  12  comes out of the tape container  4  and the next sensor optical path hole  14   d . Since this modification can further enhance unnecessary light shielding effect, it is possible to further prevent malfunction in detecting the tape end of a tape T. In this case, however, the light shielding member  20  is bonded to the two portions and is slightly disadvantageous in production efficiency. Nevertheless, the production efficiency of this modification is sufficiently advantageous over the conventional cassette case. 
     FIG. 11 is a perspective view of the important parts of a lower case portion  2  in the third embodiment of the present invention (corresponding to FIG.  8 B). In the third embodiment shown in FIG. 1, a light shielding portion  15  is provided around a sensor optical path hole  14   c  right after light from a light emission element  12  comes out of a tape container  4 . This light shielding portion  15  is constituted by forming a wall portion  10   c  itself out of a light shielding member with two colors in the formation of a cassette case  1 . FIG. 11 shows that a light shielding material portion is indicated by hatching. 
     In the third embodiment as in the case of the first embodiment, it is possible to prevent malfunction in the detection of a tape end irrespectively of the characteristics (color, transparency and reflectance) of the cassette case  1 . Besides, if the cassette case  1  itself is formed out of a high transparency material, a color originally intended for the cassette case  1  can be maintained as much as possible. Furthermore, since it suffices to form the wall portion  10   c  with two colors in the production of the tape cassette, production efficiency does not extremely deteriorate differently from the conventional tape cassette. 
     FIG. 12 is a perspective view of the important parts of a lower case portion  2  in the fourth embodiment of the present invention (corresponding to FIG.  8 B). The fourth embodiment shown in FIG. 12 differs from the third embodiment in that not a wall portion right after light from a light emission element  12  comes out of the tape container  4  but the next wall portion  10   d  is colored with two colors. The remaining constituent elements are the same as those in the third embodiment, which description will not be, therefore, given herein. 
     It can be expected that the fourth embodiment provides the same function and advantages as those of the third embodiment. 
     As a modification of the third and fourth embodiments, the wall portion  10   c  right after light from the light emission element  12  comes out of the tape container  4  and the next wall portion  10   d  may be formed out of a light shielding material and to be colored with two colors. Since this modification can further enhance unnecessary light shielding effect, it is possible to further prevent malfunction in the detection of a tape end. Although the two portions are colored with two colors, this modification provides the same production efficiency as those of the third and fourth embodiments and is not disadvantageous over the third and fourth embodiments. 
     FIGS. 13 and 14 show the fifth embodiment according to the present invention. FIG. 13 is a perspective view of the important parts of a lower case portion  2  (corresponding to FIG. 8B) and FIG. 14 is a perspective view of a light shielding holder. In the fifth embodiment shown in FIG. 13, a light shielding portion  15  is provided on a wall portion  10   c  right after light from a light emission element  12  comes out of a tape container  4 . The light shielding portion  15  is constituted by attaching the light shielding holder  23  shown in FIG. 14 to the wall portion  10   c.    
     Namely, a sensor optical path hole like that in the wall portion  10   c  of the preceding embodiments is not provided but an area indicated by longitudinal hatching in FIG. 13 is notched. The light shielding holder  23  shown in FIG. 14 is attached to the wall portion  10   c  which is formed to be short, by stopping stopper pieces  23   b  at the wall portion  10   c . The light shielding holder  23  is formed out of a light shielding material with a light shielding color. A sensor optical path hole  23   a  is provided in the light shielding holder  23  on a portion corresponding to the sensor optical path hole  14   c  and the paired stopper pieces  23   b ,  23   b  stopped at upper and lower wall portions  10   c  (an upper case portion side of which is not shown) are formed to protrude integrally with each other. 
     This fifth embodiment, as in the case of the first embodiment, can prevent malfunction in the detection of a tape end irrespectively of the characteristics (color, transparency and reflectance) of a cassette case  1 . If the cassette case  1  itself is formed out of a high transparency material, a color originally intended for the cassette case  1  can be maintained as much as possible. Besides, since it suffices to attach the light shielding holder  23  to the wall portion  10   c  in the production of a tape cassette, production efficiency does not extremely deteriorate differently from the conventional tape cassette. 
     FIG. 15, which shows the sixth embodiment according to the present invention, is a perspective view of the important parts of a lower case portion  2  (corresponding to FIG.  8 B). In the sixth embodiment shown in FIG. 15, a light shielding portion  15  is provided on a wall portion  10   d  next to a portion right after light from a light emission element  12  comes out of a tape container  4 . The light shielding portion  15  is constituted by attaching the light shielding holder  23  shown in FIG. 14 to the wall portion  10   d . The specific constitution is the same as that of the fifth embodiment, which description will not be, therefore, given herein. 
     It can be expected that the sixth embodiment provides the same function and advantages as those of the fifth embodiment. 
     As a modification of the fifth and sixth embodiments, the light shielding holder  23  may be attached to the wall portion  10   c  right after light from the light emission element  12  comes out of the tape container  4  and to the next wall portion  10   d . Since this modification can further enhance unnecessary light shielding effect, it is possible to further prevent malfunction in the detection of a tape end. In this modification, however, the light shielding holder  23  is attached to the two portions and is slightly disadvantageous in production efficiency. Nevertheless, it is sufficiently advantageous over the conventional cassette case. 
     FIGS. 16A and 16B show the seventh embodiment according to the present invention. FIG. 16A is a side view of the cover lock member  25  and FIG. 16B is a front view of the cover lock member  25 . The cover lock member  25  shown therein is arranged in a cover lock container  6  as shown in FIG.  8 A. The cover lock member  25  is formed out of a light shielding material with a light shielding color and consists of a plate portion  25   a , rotation support portions  25   b  fixed to the upper end of the plate portion  25   a , respectively, a pressed portion  25   c  provided to protrude from the lower end of the plate portion  25   a , a stopper claw  25   d  for stopping a cover (not shown) and a cylindrical protrusion  25   e  provided almost at the center of the plate portion  25   a  to protrude at the opposite side to the pressed portion  25   c  and the stopper claw  25   d.    
     A sensor optical path hole  26  is provided in the cylindrical protrusion  25   e . The sensor optical path hole  26  is preferably set longer as far as it does not interferes in the container  6 . The cylindrical protrusion  25   e  is inclined downward at a cover locking position (which is a position shown in FIGS.  16 A and  16 B). If the pressed portion  25   c  is pressed in the course of the insertion of a cassette, the cylindrical protrusion  25   e  rotates with the rotation support portion  25   b  used as a fulcrum in an arrow direction in FIG.  16 B and it is then put at an unlock position. At the unlock position, the cylindrical protrusion  25   e  is put horizontally and the sensor optical path hole  26  of the protrusion  25   e  is arranged on a straight line L1 coupling the position of the light emission element  12  with that of the light reception element  13   a.    
     According to the seventh embodiment, light advancing straight to the light reception element  13   a , among the light from the light emission element  12 , enters the cover lock container  6  (shown in FIG. 8A) by way of the tape container  4  (shown in FIG. 8A) and the light is incident on the sensor optical path hole  26  of the cylindrical protrusion  25   e . The incident light is emitted without abutting on the inner surface of the sensor optical path hole  26  and reaches the light reception element  13   a  by way of the sensor optical path hole  14   e . Conversely, the above-stated unnecessary light does not normally advance straight to the light reception element  13   a  but is incident on the sensor optical path hole  26  of the cylindrical protrusion  25   e , abutted on the inner surface of the sensor optical path hole  26  having a length M and shielded by the absorption effect of the hole  26 . In the seventh embodiment, therefore, only the cover lock member  25  is worked, so that it is possible to prevent malfunction in the detection of a tape end irrespectively of the characteristics (color, transparency and reflectance) of the cassette case  1 , to prevent the deterioration of production efficiency and to thereby respond to the demand of mass production. Besides, if the cassette case itself is formed out of a high transparency material, a color originally intended for the cassette case  1  can be maintained. 
     While the seventh embodiment is advantageous if utilized solely as stated above, it is also possible to combine the seventh embodiment with the first to sixth embodiments. By combining so, the advantage of preventing malfunction further enhances. 
     In the seventh embodiment, the cover lock member  25  itself is formed out of a light shielding material with a light shielding color. It is also possible to form only the cylindrical protrusion  25   e  out of a light shielding material with a light shielding color. It is noted, however, that the light among the unnecessary light which abuts on the plate portion  25   a  and the like of the cover lock member  25  can be shielded by the absorption effect of the cover lock member  25  if the member  25  itself is formed out of a light shielding material with a light shielding color and the unnecessary light shielding effect enhances. Thus, it is preferable that the cover lock member  25  itself is formed out of a light shielding material with a light shielding color. 
     FIG. 17A is a sensor output characteristic chart while colorlessness (transparency) is used as the color of the cassette case  1  and each of the right and left widths (light shielding range widths) D of the light shielding portion is changed in the first to sixth embodiments. FIG. 17B shows each of the right and left widths (light shielding range widths) D of the light shielding portion. It is noted that the virtual line of FIG. 17B indicates the region of the light shielding portion  15  in the first to sixth embodiments. Here, although already explained above, the right and left widths D of the light shielding portion  15  mean right and left widths from the center of an optical path coupling the position of the light emission element  12  with that of the light reception element  13   a  by a straight line L1. If the width D is set at not less than 1 mm, desired light shielding effect can be obtained, which will be described hereinafter. 
     In the detection of a tape end, it is assumed that a threshold value is around 3V and the sensor malfunctions if a sensor output voltage is not less than 3V even in a state in which a magnetic recording layer tape part is to be detected, and the sensor normally functions if the sensor output voltage is not more than 3V. 
     As shown in FIG. 17A, if a light shielding range width is zero, i.e., the light shielding portion  15  is not at all provided around the sensor optical path hole  14   c  (or  14   d ), the sensor output voltage is 5V and the sensor malfunctions. If the light shielding portion  15  is provided around the sensor optical path hole  14   c  (or  14   d ) and the width D is gradually increased, the sensor output voltage has a gradual decrease. If each of the right and left widths D of the light shielding portion  15  becomes about 1 mm, the sensor output voltage is not more than 3V. If the width D is not less than 2 mm, the sensor output voltage drops down to not more than 1V. This is because unnecessary light is shielded by the shielding portion  15  and thereby the quantity of the unnecessary light which reaches the light reception element  13   a  decreases. This demonstrates that the quantity of the unnecessary light which reaches the light reception element  13   a  largely depends on the right and left widths D of the light shielding portion  15 . 
     The unnecessary light which reach the light reception element  13   a  include upper and lower reflected lights reflected by the flange  5   a  of the reel  5  or the like and right and left reflected lights reflected by the wall portions of the cassette case  1 . The upper and lower reflected lights highly likely reach the light reception element  13   a  but are shielded by the shielding portion  15 . This follows that even if the entire periphery of the sensor optical path hole  14   c  (or  14   d ) is not shielded, unnecessary light can be effectively shielded. 
     As can be understood from the above and as show in FIG. 17A, even if the lateral side of the sensor optical path hole  14   c  (or  14   d ) is not shielded, a sensor output of not more than 3V can be held and there is less possibility of malfunction by setting the respective left and right widths D of the shielding portion  15  at not less than 1 mm. 
     FIG. 18 shows a list of malfunction evaluation results of the first and second embodiments and their comparison examples. A comparison example 1 is a case where a light shielding portion is provided around the sensor optical path hole  14   a  of the wall portion  10   a  before light from the light emission element  12  is incident on the tape container  4 . A comparison example 2 is a case where a light shielding portion is provided around the sensor optical path hole  14   b  of the wall portion  10   b  before light from the light emission element is incident on the tape container  4 . A comparison example 3 is a case where a light shielding portion is provided around the sensor optical path hole  14   e  of the last wall portion  10   e  after light from the light emission element  12  comes out of the tape container  4 . 
     In a sample A, the color of the cassette case is colorless (transparent). In a sample B, the color of the cassette case is smoke (translucent). In a sample C, the color of the cassette case is red (non-transparent). In a sample D, the color of the cassette case is black (non-transparent). As a measurement equipment, a commercially available VTR was used. 
     The symbols of the evaluation results mean as follows. Symbol ◯ means that the sensor normally functions with the commercially available VTR; symbol Δ means that the detection voltage of the sensor is high and the sensor sometimes malfunction with the commercially available VTR; symbol X means that the sensor always malfunctions with the commercially available VTR. As can be seen from FIG. 18, the embodiments of the present invention can prevent the sensor from malfunctioning in the detection of a tape end irrespectively of the characteristics (color, transparency and reflectance) of the cassette case  1 . 
     FIGS. 19 and 20 show the eighth embodiment according to the present invention. FIG. 19 is a schematically longitudinal sectional view of a tape cassette and FIG. 20 is a perspective view of the important parts of a lower case portion (corresponding to part F in FIG.  8 A). The eighth embodiment will be compared with the conventional case. It is noted that the same constituent elements as those in the conventional case will not be described herein to avoid repetitive description and only different constituent elements will be described with reference to FIGS. 19 and 20. 
     Namely, in the eighth embodiment, a portion close to a light reception element  13   b  is not colored with a low reflectance color unlike the conventional tape cassette. As shown in FIG. 20, a light shielding portion  15  is provided around the sensor optical path hole  17   c  of a wall portion  16   c  right after light from a light emission element  12  comes out of a tape container  4  at a left side (supply side). The light shielding portion  15  is constituted by bonding a light shielding member formed out of a light shielding material to be colored with a light shielding color to the wall portion as in the case of the first embodiment, forming the wall portion  16   c  itself out of a light shielding material to be colored with two colors in the production of the cassette case  1  as in the case of the third embodiment or attaching a light shielding holder to the wall portion  16   c  as in the case of the fifth embodiment. 
     In the detection of a tape end at the supply side, the light shielding portion  15  is provided to have right and left widths each of not less than about 1 mm from the center of an optical path coupling the position of the light emission element  12  with that of the light reception element  13   b  by a straight line L2 and to spread over the entire height of the wall portion  16   c . This is true for the following ninth, tenth and twelfth embodiments. The reason for setting the right and left widths at not less than about 1 mm is the same as that already described above. 
     With the above-stated constitution, light  22  advancing straight to the light reception element  13   b , among the light from the light emission element  12 , reaches a tape traveling path by way of sensor optical path holes  17   a  and  17   b . If a tape T on the tape traveling path is a magnetic recording layer tape part, it does not transmit light and the light does not, therefore, reach the light reception element  13   b . If the tape T on the tape traveling path is a high light transparency leader tape part, it transmits light and the light reaches the light reception element  13   b  by way of the sensor optical path holes  17   c ,  18   a  and  17   d.    
     Further, among light from the light emission element  12 , unnecessary light  23  which does not advance straight to the light reception element  13   b  and unnecessary light  23  incident into the cassette case  1  from a window or the like on the upper surface of the tape container  4  of the tape cassette may be reflected by the upper and lower flanges  5   a  and  5   b  of a reel  5 , the inner surface of the cassette case  1  and the like and directed toward the light reception element  13   b  without passing the tape traveling path. Since most of the unnecessary light  23  which may possibly reach the light reception element  13   b  is abutted against the light shielding portion  15  and then shielded by the portion  15 , the ratio of the unnecessary light which reaches the light reception element  13   b  is very low. 
     Accordingly, it is possible to prevent malfunction in the detection of a tape end irrespectively of the characteristics (color, transparency and reflectance) of the cassette case. It suffices to simply bond a light shielding member to the wall portion  16   c  in the production of a tape cassette, to form the wall portion  16   c  to be colored with two colors in the production of a tape cassette or to attach the light shielding holder to the wall portion  16   c . Unlike the conventional tape cassette, therefore, production efficiency does not deteriorate greatly. Furthermore, it suffices to bond the light shielding member  20  to only one wall portion  10   c  which is not on the outer surface of the cassette case  1 , to form the wall portion  16   c  to be colored with two colors in the production of a tape cassette or to attach the light shielding holder to the wall portion  16   c . Therefore, if the cassette case itself is made of a high transparency material, a color originally intended for the cassette case  1  can be maintained as much as possible. 
     FIG. 21 is a perspective view of the important parts of the lower case portion  2  in the ninth embodiment according to the present invention. In the ninth embodiment, a light shielding portion  15  is provided not to a portion just after light from a light emission element  12  comes out of a tape container  4  at a left side (supply side) but provided around the sensor optical path hole  17   d  of the next wall portion  16   d . The light shielding portion  15  is the same in constitution as that in the eighth embodiment. 
     It can be expected that the ninth embodiment provides the same function and advantages as those of the eighth embodiment. 
     As a modification of the eighth and ninth embodiments, the light shielding member  20  may be bonded around the sensor optical path hole  17   c  right after light from the light emission element  12  comes out of the tape container  4  and the next sensor optical path hole  17   d . Since this modification can further enhance unnecessary light shielding effect, it is possible to further prevent malfunction in detecting a tape end. In this case, however, the light shielding portion  15  is provided with the two portions and is slightly disadvantageous in production efficiency. Nevertheless, the production efficiency of this modification is sufficiently advantageous over the conventional cassette case. 
     FIGS. 22 and 23 show the tenth embodiment according to the present invention. FIG. 22 is a perspective view of the important parts of a lower case  2  and FIG. 23 is a perspective view of a tape pad. In the tenth embodiment shown in FIGS. 22 and 23, the tape pad  18  itself, arranged between the sensor optical path hole  17   c  of a wall portion  16   c  right after light from a light emission element  12  comes out of a tape container  4  and the sensor optical path hole  17   d  of the next wall portion  16   d , is constituted as a light shielding portion  15 . Namely, while the tape pad is formed out of a transparent member in the conventional tape cassette, the tape pad  18  is formed out of a light shielding material with a light shielding color in this embodiment and serves as the light shielding portion  15 . In FIG. 22, reference symbol  30  denotes a tape guide. The tape pad  18  is arranged between the tape guide  30  and the wall portion  16   c  for the purpose of preventing a tape from loosening. 
     It can be expected that the tenth embodiment provides the same function and advantages as those of the preceding eighth and ninth embodiments. Further, in the tenth embodiment, it suffices to conduct a step of assembling the tape pad  18  which is naturally necessary. Thus, compared with the conventional tape cassette, production efficiency enhances. 
     FIG. 24 is a perspective view of the important parts of a case portion  2  in the eleventh embodiment according to the present invention. In the eleventh embodiment shown in FIG. 24, a cylindrical light shielding member  31  serving as a light shielding portion  15  is provided between the sensor optical path hole  17   c  of a wall portion  16   c  right after light from a light emission element  12  comes out of a tape container  4  at a left side (supply side) and the sensor optical path hole  17   d  of the next wall portion  16   d  and at a position at which the traveling of a tape is not obstructed. The cylindrical light shielding member  31  is formed out of a light shielding material with a light shielding color and includes therein a sensor optical path hole  31   a  of a length N. 
     The sensor optical path hole  31   a  of the cylindrical light shielding member  31  is preferably set longer as far as it does not obstruct the traveling of the tape. The center of the sensor optical path hole  31   a  is arranged on a straight line L2 coupling the position of the light emission element  12  with that of the light reception element  13   b . Further, the diameter of the sensor optical path hole  31   a  is set to be at least the same as that of the optical path holes  17   a  to  17   d.    
     It can be expected that the eleventh embodiment provides the same function and advantages as those of the seventh embodiment. Namely, unnecessary light does not normally advance straight to the light reception element  13   b  but is incident on the sensor optical path hole  31   a  of the cylindrical light shielding member  31 , abutted on the inner surface of the hole  31   a  with the length N and shielded by the absorption effect of the member  31 . According to the eleventh embodiment, therefore, it is possible to prevent malfunction in the detection of a tape end only by adding the cylindrical light shielding member  31  irrespectively of the characteristics (color, transparency and reflectance) of the cassette case  1 . Besides, if the cassette case  1  itself is formed out of a high transparency material, a color originally intended for the cassette case  1  can be maintained. 
     FIG. 25 is a perspective view of the important parts of a case portion  2  in the twelfth embodiment according to the present invention. In the twelfth embodiment shown in FIG. 25 as in the case of the eleventh embodiment, a light shielding wall portion  32  is newly provided between the sensor optical path hole  17   c  of a wall portion  16   c  right after light from a light emission element  12  comes out of a tape container  4  at a left side (supply side) and the sensor optical path hole  17   d  of the next wall portion  16   d  and at a position at which the traveling of a tape is not obstructed. The light shielding wall portion  32  is formed out of a light shielding material with a light shielding color. A sensor optical path hole  32   a  is formed in the light shielding wall portion  32 . The center of the sensor optical path hole  32   a  is arranged on a straight line L2 coupling the position of the light emission element  12  with that of the light reception element  13   b . Further, the size of the sensor optical path hole  32   a  is set to be the same as at least that of the sensor optical path holes  17   a  to  17   d . This light shielding portion  32  is constituted by separately attaching the portion  32  to the cassette case after the cassette case has been manufactured or by forming the portion to be colored with two colors in the production of the cassette case. 
     It can be expected that the twelfth embodiment provides the same light shielding effect as those of the eighth and ninth embodiments. 
     While the eleventh or twelfth embodiment provides advantages if used solely as stated above, it is also possible to combine it with the eighth to tenth embodiments. By combining so, the advantage of preventing malfunction further enhances. 
     FIG. 26 shows a list of malfunction evaluation results of the eighth to eleventh embodiments and their comparison examples. A comparison example 4 is a case where a light shielding portion is provided around the sensor optical path hole  17   a  of a wall portion  16   a  just before light from a light emission element  12  is incident on a tape container  4 . A comparison example 5 is a case where a light shielding portion is provided around the sensor optical path hole  17   b  of a wall portion  16   b  just before light from the light emission element  12  is incident on a tape container  4 . A comparison example 6 is a case where no light shielding measures are taken. 
     In a sample A, the color of the cassette case is colorless (transparent). In a sample B, the color of the cassette case is smoke (translucent). In a sample C, the color of the cassette case is red (non-transparent). In a sample D, the color of the cassette case is black (non-transparent). As a measurement equipment, a commercially available VTR was employed. 
     The symbols of the evaluation results mean as follows. Symbol ◯ means that the sensor normally functions with the commercially available VTR. Symbol X means that the sensor always malfunctions with the commercially available VTR. As can be understood from FIG. 26, the embodiments of the present invention can prevent the sensor from malfunctioning in the detection of a tape end irrespectively of the characteristics (color, transparency and reflectance) of the cassette case  1 . 
     FIG. 27 is a schematically longitudinal sectional view in the thirteenth embodiment according to the present invention. In the thirteenth embodiment shown in FIG. 27, both an upper flange  5   a  and a lower flange  5   b  of each of a pair of reels  5 ,  5  are formed out of a material attenuating a reflected light with a color (e.g., black) attenuating reflected light. In FIG. 27, the upper flange  5   a  and the lower flange  5   b  of the respective paired reels  5 ,  5  are indicated by hatching. 
     According to the thirteenth embodiment, unnecessary light  23  which does not advance straight to a light reception element  13   b  and unnecessary light  23  which is incident into a cassette case  1  from a window and the like on the upper surface of the tape container  4  of the tape cassette, among the light from a light emission element  12 , are abutted on the inner surfaces of the upper and lower flanges  5   a  and  5   b  of the reels  5  and the reflected light is attenuated, i.e., shielded by the absorption effect of the flanges. Therefore, according to the thirteenth embodiment, it is possible to prevent malfunction in the detection of the tape end only by installing the reels  5  subjected to light shielding processing irrespectively of the characteristics (color, transparency and reflectance) of the cassette case  1 . Besides, production efficiency does not deteriorate and it is, therefore, possible to deal with the demand of mass production. Moreover, if the cassette case  1  itself is formed out of a high transparency material, a color originally intended for the cassette case  1  can be maintained. 
     While both of the paired reels  5 ,  5  are subjected to light shielding processing in the thirteenth embodiment, only one of the right side (take-up side) and the left side (supply side) of the reels may be subjected thereto. Further, while both the upper flange  5   a  and the lower flange  5   b  of each of the paired reels  5  are subjected to light shielding processing in the thirteenth embodiment, only one of the upper flange  5   a  and the lower flange  5   b  may be subjected thereto. 
     While the thirteenth embodiment provides advantages if used solely as stated above, it is also possible to combine the thirteenth embodiment with the preceding first to seventh embodiments or eighth to twelfth embodiments. By combining so, the advantage of preventing malfunction further enhances. 
     While the constitutions of the tape cassette regarding the detection of a tape end at the take-up side in the first to seventh embodiments do not show the light shielding means disclosed by the eleventh and twelfth embodiments, the light shielding means disclosed by the eleventh and twelfth embodiments can be also applied to the take-up side. 
     (Tape Cassette in Embodiments Regarding the Presence/Absence of the Tape Cassette) 
     FIGS. 28 to  31  show the fourteenth embodiment according to the present invention. Specifically, FIG. 28A is a plan view of a tape cassette from which only the upper portion of a cassette case is removed; FIG. 28B is a back view of the tape cassette; FIG. 28C is a side view of the tape cassette; FIG. 29 is a partial enlargement view of part MM of FIG. 28A; FIG. 30 shows the optical path of detected light incident on a prism portion on the side surface of the tape cassette; and FIG. 31 shows the optical path of detected light incident on a prism portion on the back surface thereof. 
     With reference to FIGS. 28A to  28 C, description will be given to the cassette presence detection means  112  at the side of an apparatus (a recording and reproducing apparatus, a cassette changer or the like) in which the tape cassette TTC in the fourteenth embodiment is used. The cassette presence detection means  112  includes a light emission portion  112   a  provided at the apparatus side and a light reception portion  112   b  for receiving detected light from the light emission portion  112   a . The cassette presence detection means  112  is set so that the optical path CC1 (the center of which is shown therein) of detection light reaching the light reception portion  112   b  from the light emission portion  112   a  passes a cassette position by going from the side surface side of the tape cassette TTC through the front surface side thereof. To be exact, the detection light is emitted from the light emission portion  112   a  at a light emission angle of about 30 degrees (15 degrees at one side). 
     Meanwhile, the cassette case  120  of the tape cassette TTC has a generally flat, rectangular parallelopiped shape consisting of an upper surface portion  120   a , a bottom portion  120   b , a pair of right and left side surface portions  120   c , a front surface portion  120   d  and a back surface portion  120   e . The cassette case  120  is made of a high transparency material (e.g., polystyrene). A partition wall  122  is provided in the cassette case  120  to form a pair of tape containers  121 ,  121  and a pair of wound tapes (not shown) are rotatably contained in the paired containers  121 ,  121  respectively. 
     Prism portions  123  and  124  are provided on a portion of the cassette case  120  which portion corresponds to that on the optical path CC1 of the detected light and on which portion the detection light emitted from the light emission portion  112   a  is first incident, or to be specific, on part of the side surface portion  120   c  and the back surface portion  120   e  adjacent the side surface portion  120   c , respectively (FIG. 28A shows an area in which the prism portions  123  and  124  are provided is indicated by hatching). 
     The prism portions  123  and  124  on the side surface portion  120   c  and the back surface portion  120   e , respectively, are formed continuously in parallel as shown in FIG.  29 . They are formed simultaneously with the formation of the cassette case  120  in an integral fashion. The prism portion  123  on the side surface portion  120   c  is formed to have a vertical angle of 30 degrees, whereas the prism portion  124  on the back surface portion  120   e  is formed to have a vertical angle of 60 degrees. 
     With the above-stated constitution, if the tape cassette TTC is put at the cassette position of the apparatus, the detection light from the light emission portion  112   a  is applied thereto about the optical path CC1. As shown in FIG. 30, this detection light is incident on the side surface portion  120   c  at the center of an incident angle of almost 70 degrees (an angle with respect to an incident normal LL1) and emitted at an emission angle of 23 degrees with respect to the incident normal LL1 by the refraction of the prism portion  123 . Accordingly, the detection light is emitted in a direction largely deviated from the optical path CC1 of the incident light. The angle of deviation of the prism portion  123  (difference between the incident angle and the emission angle) is 47 degrees. 
     As shown in FIG. 31, the detection light is incident on the back surface portion  120   e  of the tape cassette TTC at the center of the incident angle of almost 40 degrees (an angle with respect to an incident normal LL2) and emitted to the emission surface  124   a  of the prism portion  124  at a projection angle of 54.5 degrees. Since the critical angle of the prism portion  124  is almost 40 degrees, the detection light is, therefore, totally reflected. Accordingly, the detection light is emitted in a direction largely deviated from the optical path CC1 of the incidence light. As can be seen from the above, the detection light applied to the tape cassette TTC hardly reaches the light reception portion  112   b  by the refraction or reflection of the prism portions  123  and  124  and it is possible to prevent a cassette detection error in the tape cassette TTC with the high transparency cassette case  120 . 
     While the prism portion  123  on the side surface portion  120   c  is formed to have a vertical angle of 30 degrees and the prism portion  124  on the back surface portion  120   e  is formed to have a vertical angle of 60 degrees in the fourteenth embodiment, the prism portions  123  and  124  may be formed so as to refract or reflect incident light in the emission direction in which the light does not reach the light reception portions  112   b.    
     FIG. 32, which shows the fifteenth embodiment according to the present invention, shows prism portions arranged on part MM of FIG. 28A in a partially enlarged view. In the fifteenth embodiment, an inner wall  130  parallel to the side surface portion  120   c  is formed inside the cassette case  120  in addition to the prism portion  123  on the side surface portion  120   c  and the prism portion  124  on the back surface portion  120   e  of the fourteenth embodiment. A prism portion  123  is formed on one surface of the inner wall  130  to have the same vertical angle of 30 degrees as that of the prism portion  123  on the side surface portion  120   c . The remaining constitution is the same as that of the fourteenth embodiment. The inner wall  130  is formed to reach a partition inner wall  122 . With the inner wall  130 , incident light leaked in the corner (in the form of R)  120   f  in which the side surface portion  120   c  and the back surface portion  120   e  cross each other, can be refracted, among the light from the side surface portion  112   a , in an emission direction in which the light does not reach the light reception portion  112   b . Accordingly, it is possible to prevent a cassette detection error in the tape cassette TTC with the high transparency cassette case  120 . 
     FIGS. 33 to  35  show the sixteenth embodiment according to the present invention. Specifically, FIG. 33A is a plan view of a tape cassette from which only the upper surface portion of a cassette case is removed; FIG. 33B is a back view of the cassette case; FIG. 33C is a side view of the cassette case; FIG. 34 is a partially enlarged view of part NN of FIG. 33C; and FIG. 35 shows the optical path of detection light incident on a prism portion on the bottom surface. 
     With reference to FIGS. 33A to  33 C, description will be given first to cassette presence detection means  113  at the side of an apparatus in which the tape cassette TTC in the sixteenth embodiment is used. The cassette presence detection means  113  has a light emission portion  113   a  provided at the apparatus side and a light reception portion  113   b  for receiving detection light from the light emission portion  113   a . The cassette presence detection means  113  is set so that the optical path CC2 (the center of which is shown therein) of the detection light reaching the light reception portion  113   b  from the light emission portion  113   a  may pass a cassette position by going from the bottom side of the tape cassette TTC through the upper surface side thereof. Actually, the detection light is emitted from the light emission portion  113   a  at an emission angle of about 30 degrees (15 degrees at one side). 
     Meanwhile, the cassette case  120  of the tape cassette TTC has a generally flat, rectangular parallelopiped shape consisting of an upper surface portion  120   a , a bottom portion  120   b , a pair of right and left side surface portions  120   c ,  120   c , a front surface portion  120   d  and a back surface portion  120   e  and formed out of a high transparency material (e.g., polystyrene). A partition inner wall  122  forming a pair of tape containers  112  is provided inside the cassette case  120 . A pair of wound tapes (not shown) are rotatably contained in the paired tape containers  121 ,  121 , respectively. 
     A prism portion  125  is provided on a portion of the cassette case  120  which portion corresponds to that on the optical path CC2 of the detection light and on which the detection light emitted from the light emission portion  113   a  is incident first, to be specific, on part of the bottom portion  120   b  (an area in which the prism portion  125  is provided is indicated by hatching to clarify the position thereof in FIG.  33 A). 
     As shown in FIG. 34, the prism portion  125  is formed continuously in parallel and formed simultaneously with the formation of the cassette case  120  in an integrally fashion. The prism portion  125  on the bottom portion  120   b  is formed to have a vertical angle of 30 degrees. 
     With the above-stated constitution, if the tape cassette TTC is put at the cassette position of the apparatus, the detection light from the light emission portion.  113   a  is applied thereto about the optical path CC2. As shown in FIG. 35, this detection light is incident on the bottom portion  120   b  of the tape cassette TTC at the center of an incident angle of almost 20 degrees (an angle with respect to an incident normal LL3) and emitted at an emission angle of 49 degrees with respect to the emission surface  125   a  of the prism portion  125 . Since the critical angle of the prism portion  125  is almost 40 degrees, the detection light is, therefore, totally reflected. Accordingly, the detection light is emitted in a direction largely deviated from the optical path CC2 of the incidence light. As can be seen from the above, the detection light applied to the tape cassette TTC hardly reaches the light reception portion  113   b  by the reflection of the prism portion  125  and it is possible to prevent a cassette detection error in the tape cassette TTC with the high transparency cassette case  120 . 
     While the prism portion  125  on the bottom portion  120   b  is formed to have a vertical angle of 30 degrees in the sixteenth embodiment, the prism portion  125  may be formed so as to refract or reflect incident light in the emission direction in which the light does not reach the light reception portions  112   b.    
     FIGS. 36A to  36 C show the seventeenth embodiment according to the present invention. Specifically, FIG. 36A is a plan view of a tape cassette from which only the upper surface portion of a cassette case is removed; FIG. 36B is a back view of the tape cassette; and FIG. 36C is a side view of the tape cassette. 
     In FIGS. 36A to  36 C, the tape cassette TTC is constituted to be applicable to both the apparatuses in the fourteenth(fifteenth) and sixteenth embodiments. Namely, prism portions  123 ,  124  and  125  are provided on portions of the cassette case  120  corresponding to those on the two optical paths CC1 and CC2 of the detection light (the side surface portion  120   c  of the cassette case  120  and part of the back surface portion  120   e  adjacent the side surface portion  120   c  as described in the fourteenth and fifteenth embodiments and part of the bottom portion  120   b  as described in the sixteenth embodiment), respectively (FIG. 36A shows an area in which the prism portions  123 ,  124  and  125  are provided is indicated by hatching to clarify the positions thereof). The constitutions of the respective prism portions  123 ,  124  and  125  are the same as those described in the fourteenth (or fifteenth) embodiment and the sixteenth embodiment, which description will not be given herein to avoid repetitive description. 
     In the tape cassette TTC in the seventeenth embodiment, even if it is used in either the apparatus in the fourteenth (or fifteenth) embodiment or that in the sixteenth embodiment, detection light applied to the tape cassette TTC hardly reaches the light reception portions  112   b  and  113   b  by either the refraction or reflection of the prism portions  123 ,  124  and  125 . It is, therefore, possible to prevent a cassette detection error in the tape cassette TTC with the high transparency cassette case  120 . 
     In the above-stated fourteenth to seventeenth embodiments, since the prism portions  123 ,  124  and  125  are formed integrally with the cassette case  120  and they are formed simultaneously with the cassette case  120 , the production of the prism portions  123 ,  124  and  125  is easy and production cost can be reduced. Alternatively, the prism portions  123 ,  124  and  125  may be produced separately from the cassette case  120  and then attached to the cassette case. 
     In the above-stated fourteenth, fifteenth and seventeenth embodiments, since the prism portion  123  is provided on the portion of the cassette case  120  on which portion detection light emitted from the light emission portion  112   a  is first incident, the distance from the prism portion  123  to the light reception portion  112   b  is long. Thus, it is possible to prevent the detection light from reaching the light reception portion  112   b  even if the deviation angle of the prism portion  123  is set small, whereby the degree of freedom for the design of the prism portion  123  increases. Alternatively, the prism portion may be provided on the portion of the cassette case  120  on which the detection light emitted from the light emission portion  112   a  is incident not first but second, to be specific, on the front surface portion  120   d.    
     In the above-stated fourteenth to seventeenth embodiments, since the prism portions  123 ,  124  and  125  are provided on the inner surface of the cassette case  120 , there is little possibility that the surfaces of the prism portions  123 ,  124  and  125  are damaged or the like by friction, scratch or the like. 
     In the meantime, light shielding members may be provided at the positions of the prism portions  123 ,  124  and  125  so as to obtain the same advantages as those of the present invention. However, if the prism portions  123 ,  124  and  125  are formed integrally with the cassette case  120 , an assembly step is not necessary compared with a case where the light shielding members are provided. Thus, this embodiment is advantageous in that problems such as attachment error and peeling do not occur and also excellent in design. 
     The above-stated fourteenth to seventeenth embodiments illustrate an example of the tape cassette TTC which can be applied to a case where the optical path CC1 of the detection light passes the cassette position by going from the side surface side of the tape cassette TTC through the front surface side thereof and to a case where the optical path CC2 of the detection light passes the cassette position by going from the bottom side of the tape cassette TTC through the upper surface side thereof. It goes without saying that the present invention is also applicable to cases of optical paths other than CC1 and CC2. 
     In the above-stated fourteenth to seventeenth embodiments, the prism portions  123 ,  124  and  125  are provided only on the portions of the cassette case  120  corresponding to those on the optical paths CC1 and CC2. If similar prism portions  123 ,  124  and  125  are provided symmetrically about a vertical axis, the design of the resultant tape cassette becomes more excellent and the degree of freedom for the design of the cassette presence detection means  112  and  113  increases accordingly. 
     FIGS. 37 to  39  show the eighteenth embodiment according to the present invention. Specifically, FIG. 37 is a partially plan view of a tape cassette TTC from which the upper surface side of a cassette case  120  is removed; FIG. 38 is a perspective view of the important parts of the tape cassette showing a state before a light shielding member  117  is attached; and FIG. 39 is a perspective view of the important parts thereof showing a state that the light shielding member  117  has been attached. 
     In FIG. 37, cassette presence detection means  112  at the side of an apparatus in which the tape cassette TTC in the eighteenth embodiment is used is the same as that in the fourteenth (or fifteenth) embodiment. Therefore, the means  112  is denoted by the same reference symbol as that in the fourteenth (or fifteenth) embodiment and no description will be given thereto. Further, tape end detection means  114  is provided at the apparatus side. The tape end detection means  114  is provided with a light emission portion  114   a  and a pair of tape end detection light reception portions (one of which is not shown therein) for receiving detection light from the light emission portion  114   a . While the tape cassette TTC is being attached to the apparatus, the light emission portion  114   a  is arranged in a wall portion  115   a  having a cylindrical center and the paired light reception portions  114   b  are arranged at external positions on the right and left sides of the tape cassette TTC, respectively. 
     The cassette case  120  of the tape cassette TTC is constituted in the same manner as that in the fourteenth embodiment and formed out of a high transparency material. The wall portion  115   a , a partition inner wall  122 , a wall portion  115   b  and a side surface portion  120   c  on the tape end detection optical path CC3 coupling the light emission portion  114  with the light reception portion  114   b  of the tape end detection means  114  are provided with optical passages  116   a  to  116   e , respectively. A light shielding member  117  is attached to the portion of the light passage  116   d  of the wall portion  115   b . A light passage  117   a  is opened on the portion of the light shielding member  117  which portion contact with the optical path CC3. The light passage  117   a  is constituted to pass detection light passing on the optical path CC3 and to prevent the passage of unnecessary light deviated from the optical path CC3. That is, with this constitution, even if the cassette case  120  is formed out of a high transparency material, it is possible to ensure preventing erroneous detection of a tape end. 
     Furthermore, one end of the light shielding member  117  is formed large and extended to exceed the degree to which the portion of the light passage  116   d  on the wall portion  115   b  is blocked. This extended portion  117   b  is clinched with respect to the portion on which the light passage  117   a  is provided and arranged on the cassette presence detection optical path CC1. 
     In this eighteenth embodiment, only the light passing through the optical path CC3, among the detection light for the detection of a tape end, passes through the light passage  117   a  of the light shielding member  117  and the passage of light deviated from the optical path CC3 is prevented by the light shielding member  117 . Owing to this, if the cassette case is made of a high transparency material, it is possible to ensure preventing the erroneous detection of a tape end. In addition, the passage of the cassette presence detection light is prevented by the extended portion  117   b  of the light shielding member  117 . Owing to this, if the cassette case is made of a high transparency material, it is possible to ensure preventing the erroneous detection of the presence of a cassette. Further, in case of preventing the erroneous detection of the presence of a cassette, the light shielding member  117  for preventing the erroneous detection of a tape end is utilized. Due to this, it is possible to prevent the erroneous detection of the presence of a cassette without increasing the number of parts and without deteriorating assemblage. 
     FIG. 40, which shows the nineteenth embodiment according to the present invention, is a plan view of a tape cassette from which only the upper surface portion of a cassette case is removed. FIG. 41A is an explanatory view of the tape cassette for the surrounding of an optical path notch of the cassette case. FIG. 41B shows the optical path of tape end detection light while a prism portion is provided. FIG. 41C shows the optical path of tape end detection light while a prism portion is not provided. 
     The nineteenth embodiment is intended to prevent a tape end detection error (tape terminal end detection error) in a tape cassette TTC in which tape end detection light CC3 passes through portions other than optical path notches of a high transparency cassette case  120  in a system in which high transparency leader tapes are provided on the both ends of a magnetic tape and a tape terminal end is detected while using tape end detection light (tape terminal end detection light) CC3 from the light emission portion  114   a  of tape end detection means  114 . That is, optical path notches  122   d  and  122   e  are formed in right and left partition walls  122 ,  122  around tape end detection notches  122   b  and  122   c  on the both sides of a right semicylindrical wall  122   a  constituting the insertion hole of the light emission portion  114   a  for the detection of a tape end, respectively. Prism portions  126  and  127  for refracting or reflecting the tape end detection light CC3 from the light emission portion  114   a  in a direction in which the light does not reach the right and left light reception portions  114   b ,  114   b , are provided on the partition walls  122  around the notches  122   d  and  122   e , respectively. 
     Further, prism portions  128  and  129  for refracting or reflecting the tape end detection light CC3 from the light emission portion  114   a  in a direction in which the light does not reach the right and left light reception portions  114   b ,  114   b , are provided on walls around optical path notches  122   f  and  122   g  at the front sides of the right and left side surface portions  120   c  of the cassette case  120 , respectively. The remaining constituent elements are the same as those in the fourteenth embodiment. Accordingly, the same constituent elements are denoted by the same reference symbols and detailed description will not be given thereto. 
     According to the tape cassette TTC in the nineteenth embodiment, the tape end detection light CC3 hardly reaches the right and left light reception portions  114   b ,  114   b  by the refraction or reflection of the respective prism portions  126  to  129 , thereby making it possible to prevent a tape end detection error in the tape cassette TTC with the high transparency cassette case  120 . 
     As shown in FIGS. 41A and 41B, if the prism portion  126  is provided around the notch  112   d  through which the tape end detection light CC3 passes, the light from the light emission portion  114   a  does not advance straight as shown in FIG.  41 B and is refracted or reflected in a direction in which the light does not reach the light reception portion  114   b . In theory, the prism portion may be formed on one surface. However, if the angle of the incident light on the prism portion is small and the prism portion is formed integrally with the cassette case  120 , the advancing components of the light are left due to the curved portion (R portion) provided at the peak or in the corner of the prism portion and surface property thereof and they reach the light reception portions to thereby cause malfunction. In view of this, therefore, if the prism portions  126  to  129  are provided on a plurality of portions of the partition inner wall  122  as shown in FIG. 40, the prevention of malfunction is more ensured. 
     Needless to say, in case of detecting a tape end and detecting whether or not a tape cassette is present, the first to nineteenth embodiments described so far can be arbitrarily selected and combined. 
     It should be understood that many modifications and adaptations of the invention will become apparent to those skilled in the art and it is intended to encompass such obvious modifications and changes in the scope of the claims appended hereto.