GB2312779A - Prism mounting in apparatus to detect beginning and end portions of magnetic tape - Google Patents
Prism mounting in apparatus to detect beginning and end portions of magnetic tape Download PDFInfo
- Publication number
- GB2312779A GB2312779A GB9708746A GB9708746A GB2312779A GB 2312779 A GB2312779 A GB 2312779A GB 9708746 A GB9708746 A GB 9708746A GB 9708746 A GB9708746 A GB 9708746A GB 2312779 A GB2312779 A GB 2312779A
- Authority
- GB
- United Kingdom
- Prior art keywords
- prism
- light
- holder
- emitting element
- light emitting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/10—Beam splitting or combining systems
- G02B27/14—Beam splitting or combining systems operating by reflection only
- G02B27/143—Beam splitting or combining systems operating by reflection only using macroscopically faceted or segmented reflective surfaces
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
- G02B7/18—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors
- G02B7/1805—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors for prisms
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B15/00—Driving, starting or stopping record carriers of filamentary or web form; Driving both such record carriers and heads; Guiding such record carriers or containers therefor; Control thereof; Control of operating function
- G11B15/02—Control of operating function, e.g. switching from recording to reproducing
- G11B15/05—Control of operating function, e.g. switching from recording to reproducing by sensing features present on or derived from record carrier or container
- G11B15/06—Control of operating function, e.g. switching from recording to reproducing by sensing features present on or derived from record carrier or container by sensing auxiliary features on record carriers or containers, e.g. to stop machine near the end of a tape
- G11B15/08—Control of operating function, e.g. switching from recording to reproducing by sensing features present on or derived from record carrier or container by sensing auxiliary features on record carriers or containers, e.g. to stop machine near the end of a tape by photoelectric sensing
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Geophysics And Detection Of Objects (AREA)
Abstract
Apparatus for detecting beginning and end portions of a magnetic tape travelling on a main base of a VCR comprises light emitting element 61, beam splitting prism 65 and L-shaped prisms 31 for transmitting the light beam to light receiving elements 35. Light splitting prism 65 is secured to the main base 1 using holder 70 having hook portion 71 which is transformed resiliently when protrusions 66 of the prism are inserted into the holder (figs. 4 and 5). Hook portion 71 includes circular guide surface 70 (fig. 3) to facilitate insertion of the prism. Prism assembly is simple, with a reduced likelihood of damage to the prism. Prism 65 preferably has a convex surface (67, fig. 5), and holder 70 includes light-shielding portion 74 to prevent extraneous light from entering the prism and dispersion of the light beam projected from emitting element 61.
Description
APPARATUS FOR DETECTING BEGINNING AND END
PORTIONS OF A MAGNETIC TAPE
The present invention relates to a video cassette recorder ("VCR"); and, more particularly, to an apparatus for detecting beginning and/or end portions of a magnetic tape.
In a magnetic recording/reproducing apparatus such as a video cassette recorder, there is a growing necessity for developing means and/or apparatus for detecting the beginning and/or end portions of a magnetic tape before the magnetic tape is completely wound or rewound to a take-up reel or a supply reel, in order to prevent a damage to the tape which may be inadvertently caused by an abrupt stopping of the operation of a tape travel mechanism.
Generally, for this reason, the magnetic tape in a video cassette includes a transparent portion at the beginning and at the end portions, and a VCR is provided with an apparatus for detecting beginning and/or end portions of the magnetic tape. When the beginning and/or end portions detecting apparatus detects the transparent portion at the beginning or at the end of the magnetic tape, the tape travel is stopped by a microcomputer.
In Fig. 1, there is shown a schematic cross sectional view of a conventional apparatus 10 for detecting beginning and/or end portions of a magnetic tape.
As shown, the beginning and/or end portions detecting apparatus 10 includes a light emitting sensor 20 and a light receiving sensor 30.
The light emitting sensor 20 has an element 21 for emitting a light and a prism 25 for splitting the light beam projected from the light emitting element 21. The light emitting element 21 is mounted on a printed circuit board ("PCB") and the light splitting prism 25 is secured to a main base 1 by inserting its lower end into an opening 2 formed at the main base 1 so that the light emitting element 21 and the light splitting prism 25 are facing each other. Furthermore, in order to improve the locking force of the light splitting prism 25 with respect to the main base 1, the light splitting prism 25 includes an apertured pad portion 26 outwardly extending from its peripheral surface so as to be perpendicular to its lengthwise central axis. The pad portion 26 is secured at the main base 1 by screwing a set screw 3 in and through its aperture (not shown) and a threaded hole 4 formed at the main base 1.
The light receiving sensor 30 has a pair of L-shaped prisms 31 for transmitting the light beam reflected from the light splitting prism 25 and a pair of elements 35 for receiving light beams from L-shaped prisms 31. Each of the Lshaped prisms 31 is suitably positioned at a main chassis (not shown) of the video cassette recorder so as to receive the light beam transmitted from each of the light splitting prisms 25 and reflect it to each of the light receiving elements 35.
Each of the light receiving elements 35 is mounted on the PCB so as to receive the light beam reflected from the its corresponding L-shaped prism 31.
With the above-mentioned arrangement, the beginning and/or end portions detecting apparatus 10 detects a difference in the amount of the light beam passing through the magnetic tape traveling between the light splitting prism 25 and the pair of L-shaped prisms 31, and then applies a beginning or an end signal to a microcomputer (not shown) to thereby determine whether the tape is at the beginning or end portions or not.
In such an apparatus, however, there is a possibility that the prism may get damaged during the engaging process of the prism to the main base. Further, in the conventional apparatus described above, there is a possibility that the light beam projected from the light emitting element may get dispersed by its interaction with open air or foreign substances such as dust getting attached thereto.
It is, therefore, a primary object of the invention to provide an apparatus for detecting beginning and/or end portions of a magnetic tape which can be easily assembled to a main base.
It is another object of the invention to provide an apparatus for detecting beginning or end portion of a magnetic tape capable of preventing a dispersion of a light beam projected from a light emitting element incorporated therein.
In accordance with one aspect of the present invention, there is provided an apparatus for detecting beginning and end portions of a magnetic tape traveling on a main base of a video cassette recorder incorporating therein a pair of first prisms and a pair of light receiving elements, which comprises: an element for emitting a light; a second prism for splitting and reflecting the light beam projected from the light emitting element to each of the light receiving elements via its corresponding first prisms; and means tor locking the second prism to the main base, wherein the locking means includes a pair of protrusions provided on a peripheral surface of the second prism and a holder for accommodating the second prism by inserting the protrusions of the second prism thereinto.
In accordance with another aspect of the present invention, there is provided an apparatus for detecting beginning and end portions of a magnetic tape traveling on a main base of a video cassette recorder incorporating therein a pair of first prisms and a pair of light receiving elements, which comprises: an element for emitting a light; a second prism for splitting and reflecting the light beam projected from the light emitting element to each of the light receiving elements via its corresponding first prisms; and means for locking the second prism to the main base, wherein the locking means includes a pair of protrusions provided on a peripheral surface of the second prism and a holder for accommodating the second prism by inserting the protrusions of the second prism thereinto, the holder having a light-shielding portion for preventing unnecessary extraneous light from entering the second prism and preventing dispersion of the light beam projected from the light emitting element into the second prism.
The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments, when taken in conjunction with the accompanying drawings, in which:
Fig. 1 shows a schematic cross sectional view of a conventional apparatus for detecting beginning andlor end portions of a magnetic tape;
Fig. 2 represents a schematic cross sectional view of an apparatus for detecting beginning and/or end portions of a magnetic tape in accordance with the present invention;
Fig. 3 illustrates a perspective view of a holder of an apparatus for detecting beginning and/or end portions of a magnetic tape in accordance with the present invention;
Fig. 4 offers schematic sectional views setting forth an operation of assembling a prism incorporated in the apparatus in Fig. 2 to the holder; and
Fig. 5 depicts a cross sectional view of another embodiment of a beginning and/or end portions of a magnetic tape in accordance with the present invention.
There is shown in Fig. 2 a schematic cross sectional view of an apparatus 50 for detecting beginning and/or end portions of a magnetic tape in accordance with a present invention. It should be noted that the like parts appearing in Fig. 1 to S are represented by like reference numerals.
The inventive apparatus 50 for detecting beginning and/or end portions of a magnetic tape includes a light emitting sensor 60, a substantially cylindrical holder 70 for safely securing the l-ight emitting sensor 60 and a light receiving sensor 30.
The light emitting sensor 60 has an element 61 for emitting a light and a prism 65 for splitting the light beam projected from the light emitting element 61. The light emitting element 61 is suitably mounted on the PCB and the light splitting prism 65 is secured to the main base l using the holder 70 which will be described in detail later, so that the light emitting element 61 and the light splitting prism 65 are facing each other. Further, the light splitting prism 65 is, on its peripheral surface, provided with a pair of protrusions 66, each of which is tapered along a lengthwise central axis of the light splitting prism 65 and is circumferentially spaced from each other by a predetermined degree, e.g., 180 degrees.
The substantially cylindrical holder 70 made of a resilient material includes a hook portion 71 for engaging with the light splitting prism 65 and a body portion 73 for engaging with the main base 1. As shown in Fig. 4, the resilient property of the holder 70 allows the hook portion 71 to be transformed resiliently when the protrusions 66 of the light splitting prism 65 are inserted into the holder 70 to thereby accommodate the light splitting prism 65. The holder 70 is formed on the main base 1, e.g., using outsert mold method. The holder 70 may also be an independent member. In this case, the holder 70 is mounted at the main base 1 by inserting its lower end portion to the opening 2 of the main base 1.
As shown in Fig. 3, the hook portion 71 is provided with a circular guide surface 72 for facilitating an insertion of the light splitting prism 65 into the holder 70 at an introducing portion of the light splitting prism 65, i.e., the upper end of the holder 70. To be more specific, the diameter of the guide surface 72 gradually decreases in such a way that the lower end of the light splitting prism 65 is smoothly inserted into the holder 70 without getting damaged.
Inside diameter of the body portion 73 is substantially similar diameter to that of the light splitting prism 65 to allow the light splitting prism 65 to be tightly fitted into the holder 70.
In addition, as shown in Fig. 5, it is preferable that the light splitting prism 65 has a convex-shaped surface 67 for converging the light beam projected from the light emitting element 61 and that the holder 70 further includes a light-shielding portion 74 for preventing the unnecessary extraneous light from entering the light splitting prism 65 and preventing dispersion of the light beam projected from the light emitting element 61 into the light splitting prism 65, the light-shielding portion 74 downwardly extending from the lower end of the holder 70.
Returning to Fig. 2, the light receiving sensor 30 has a pair of L-shaped prisms 31 for transmitting the light beam reflected from the light splitting prism 65 and a pair of elements 35 for receiving a light beam projected from L-shaped prisms 31. Each of the L-shaped prisms 31 is suitably positioned at a main chassis (not shown) of the video cassette recorder so as to receive the light beam transmitted from each of the light splitting prisms 65 and reflect it to each of the light receiving elements 35. Each of the light receiving elements 35 is mounted on the PCB so as to receive the light beam reflected from its corresponding L-shaped prism 31.
With the above-mentioned arrangement, the beginning and/or end portion detecting apparatus 50 detects a difference in the amount of the light beam passing through the magnetic tape traveling between the light splitting prism 65 and the pair of L-shaped prisms 31, and then applies a beginning or an end signal to a microcomputer (not shown) to thereby determine whether the tape is at the beginning or the end portions or not.
In such an apparatus, since the prism is secured to the main base through the holder, it is easy and simple to assemble the prism and a possibility of a damage of a prism is reduced. Further, it is possible to preventing unnecessary extraneous light from entering the light splitting prism and to prevent the dispersion of the light beam projected from the light emitting element.
Although the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.
Claims (8)
1. An apparatus for detecting beginning and end portions of a magnetic tape traveling on a main base of a video cassette recorder incorporating therein a pair of first prisms and a pair of light receiving elements, which comprises:
an element for emitting a light;
a second prism for splitting and reflecting the light beam projected from the light emitting element to each of the light receiving elements via its corresponding first prisms; and
means for locking the second prism to the main base,
wherein the locking means includes
a pair of protrusions provided on a peripheral surface of the second prism and
a holder for accommodating the second prism by inserting the protrusions of the second prism thereinto.
2. The apparatus of claim 1, wherein the holder has a substantially cylindrical shape.
3. The apparatus of claim 2, wherein the holder is, at its upper end, provided with a guide surface for facilitating an insertion of the second prism into the holder.
4. The apparatus of claim 1, wherein each of the protrusions is tapered along its lengthwise central axis and the holder has a hook portion made of a resilient material so as to be resiliently transformed in accommodating the protrusions.
5. The apparatus of claim 1, wherein the second prism has a convex-shaped surface for converging the light beam projected from the light emitting element, the convex-shaped surface facing the light emitting element.
6. The apparatus of claim 1, further comprising a lightshielding means for preventing unnecessary extraneous light from entering the second prism and preventing dispersion of the light beam projected from the light emitting element into the second prism.
7. The apparatus of claim 6, wherein the light-shielding means is a portion downwardly extending from the lower end of the holder so as to surround the light emitting element.
8. Apparatus constructed and arranged substantially as herein described with reference to or as shown in Figures 2 to 5 of the accompanying drawings.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1019960013760A KR100197363B1 (en) | 1996-04-30 | 1996-04-30 | Structure for fixing a prism of end sensor in a tape recorder |
| KR1019960013761A KR970071607A (en) | 1996-04-30 | 1996-04-30 | Luminescent prism of end sensor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9708746D0 GB9708746D0 (en) | 1997-06-18 |
| GB2312779A true GB2312779A (en) | 1997-11-05 |
Family
ID=26631785
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9708746A Withdrawn GB2312779A (en) | 1996-04-30 | 1997-04-29 | Prism mounting in apparatus to detect beginning and end portions of magnetic tape |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH1097745A (en) |
| GB (1) | GB2312779A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2386204A (en) * | 2002-03-07 | 2003-09-10 | Agilent Technologies Inc | Interconnecting optical components with passive alignment |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2287575A (en) * | 1991-09-03 | 1995-09-20 | Funai Electric Co | A tape end detecting device |
-
1997
- 1997-04-25 JP JP9108969A patent/JPH1097745A/en active Pending
- 1997-04-29 GB GB9708746A patent/GB2312779A/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2287575A (en) * | 1991-09-03 | 1995-09-20 | Funai Electric Co | A tape end detecting device |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2386204A (en) * | 2002-03-07 | 2003-09-10 | Agilent Technologies Inc | Interconnecting optical components with passive alignment |
| US6764227B2 (en) | 2002-03-07 | 2004-07-20 | Agilent Technologies, Inc. | Interconnecting optical components with passive alignment |
| GB2386204B (en) * | 2002-03-07 | 2005-09-07 | Agilent Technologies Inc | Interconnecting optical components with passive alignment |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9708746D0 (en) | 1997-06-18 |
| JPH1097745A (en) | 1998-04-14 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4886220A (en) | Magnetic tape cassette | |
| US4500050A (en) | Magnetic tape cassette | |
| GB2312779A (en) | Prism mounting in apparatus to detect beginning and end portions of magnetic tape | |
| JPS6037738Y2 (en) | tape cassette | |
| US5625516A (en) | Tape end detection mechanism for tape cassette | |
| EP0609546A2 (en) | Integrated light reflecting structure for use in a magnetic tape cartridge | |
| JPH0514341Y2 (en) | ||
| JP2976555B2 (en) | Tape end detection mechanism | |
| US5775615A (en) | VCR having a reel sensor prism device | |
| US5651509A (en) | Recording/reproducing device | |
| JPS6327323Y2 (en) | ||
| KR0181041B1 (en) | Structure for fixing an emission prism of an end sensor | |
| JPS6258060B2 (en) | ||
| KR200173006Y1 (en) | Structure for fixing an emission prism of a sensor | |
| JP2557126Y2 (en) | Tape cassette | |
| JPH0519861Y2 (en) | ||
| JP3009271B2 (en) | Magnetic recording / reproducing apparatus and magnetic tape cassette used therein | |
| JPH0477395B2 (en) | ||
| JPH0413799Y2 (en) | ||
| JPS6012822U (en) | Optical recording information reproducing device | |
| JPH06295487A (en) | Magnetic recording and reproducing device | |
| JPH0127190Y2 (en) | ||
| JPS6327322Y2 (en) | ||
| KR100197363B1 (en) | Structure for fixing a prism of end sensor in a tape recorder | |
| JPS6020221Y2 (en) | magnetic tape cartridge |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |