Disc cartridge and photon mode optical information recording/reproducing apparatus

A disc cartridge accommodating a photon mode optical information recording medium is provided with a disc case having an opening section, and a shutter movably disposed between a closing position to close the opening section and an opening position to open the opening section. The disc case includes a light path bending portion for bending a clearance between the shutter at the closing position and the disc case at least at two points. Stray light propagating in the clearance between the disc case and the shutter is bent at least at two points.

BACKGROUND OF THE INVENTION

I. Technical Field

The present invention relates to a disc cartridge and a photon mode optical information recording/reproducing apparatus used for recording/reproducing photon mode optical information.

II. Description of the Related Art

A common disc-shaped recording medium (hereinafter, referred to as a medium) represented by magnetooptical recording or phase change recording is rotatably contained in a disc case. The disc case includes an opening section through which the outer surface of the medium is exposed and a slidable shutter for opening and closing the opening section.

Since an optical disc information recording/reproducing apparatus records and reproduces information by substantially focusing a laser light to a diffraction limit, information recording/reproducing characteristics are degraded upon an occurrence of dust adherence or accumulation to or on the outer surface of the medium. Particularly, since the medium features in being portable and providing compatibility among information recording/reproducing apparatuses, it has been a big problem to prevent the intrusion of dust into the case or the adherence of dust to the outer surface of the medium outside the information recording/reproducing apparatuses. Accordingly, a great number of proposals have been made such as those to improve dust resistance and those concerning the construction of disc cases and disc cartridges to prevent damage on recording surfaces of media, for example, as disclosed in Japanese Unexamined Patent Publication No. 2000-40331 and Japanese Unexamined Patent Publication No. 2004-14115.

On the other hand, a photon mode optical information recording/reproducing apparatus has been proposed as a candidate for a next-generation large-capacity storage device. The photon mode optical information recording/reproducing apparatus adopts recording and reproducing methods different from the conventional optical disc devices, and a hologram memory device, for example, as disclosed in Japanese Unexamined Patent Publication No. 2004-139711 can be cited as a typical example. In a hologram memory optical information recording system such as a hologram memory optical system adopting a shift multiplexing recording method proposed by Psaltis et al., a beam from a laser light source has its diameter expanded by a beam expander and, then, this beam is split by a half mirror. One of the split beams passes a spatial light modulator and is focused on a hologram medium by a Fourier transform lens to become a signal light. The other beam is irradiated to the same position as the signal light on the hologram medium to become a reference light. The hologram medium is constructed such that a holographic medium such as photopolymer is sealed between two glass substrates, and interference fringes of the signal light and reference light are recorded.

In the spatial light modulator, a two-dimensionally arranged optical switch array is provided, and the respective optical switches are independently turned on and off in accordance with an input signal to be recorded. For example, in the case of using a spatial light modulator of 1024 cells×1024 cells, information of 1 M bits can be simultaneously displayed. The information of 1 M bits displayed on the spatial light modulator when a signal light passes the spatial light modulator is converted into a two-dimensional light beam array. This light beam array is recorded as interference fringes on the hologram medium. In order to reproduce the recorded signal, only the reference light is irradiated to the hologram medium and a diffracted light from a hologram is received by a CCD element.

The aforementioned hologram memory optical information recording system is characterized in that angle multiplexing recording is possible to realize a large-capacity optical recording system since the holographic medium is as thick as about 1 mm and the interference fringes are recorded as a thick grating, i.e. a so-called Bragg grating. Instead of changing an incident angle of the reference light, it is also possible to realize angle multiplexing recording by shifting the irradiation position of the reference light in the form of a spherical wave. Specifically, there are utilized slight changes in the incident angle of the reference light sensed by the respective parts of the medium upon shifting the recording position by slightly rotating the disc-shaped medium. When the thickness of the holographic medium is 1 mm, wavelength selectivity specified by the intensity of the reproduced signal is 0.014 degrees at full width at half maximum. When the reference light NA is 0.5 and the hologram size is 2 mmφ, recording density realized at this time is 600 G bits/inch2if a hologram is recorded in a multiplexing manner at intervals of about 20 microns. This is equivalent to 730 GB in a 12 cm disc capacity.

Japanese Unexamined Patent Publication No. 2004-362743 shows a holographic disc cartridge. A Japanese Unexamined Patent Publication No. 2004-362743 discloses a locking mechanism for preventing an inadvertent opening of a slide shutter.

A medium used in the optical information recording/reproducing apparatus with an optical photon mode is made of a so-called photosensitive material in the nature of the recording method. Thus, this medium has sensitivity to lights having wavelengths below a visible light region such as ultraviolet rays and green lights. If a non-recorded area of the medium is photosensitized before recording, this has presented a problem of fatally degrading the characteristics such as a reduction of a recordable capacity. Although the disc cartridges for optical discs (magnetooptical discs, CDs, DVDs, etc.) disclosed in Japanese Unexamined Patent Publication No. 2000-40331 and Japanese Unexamined Patent Publication No. 2004-14115 have effective constructions in terms of dust resistance, it is substantially impossible to optically completely shield the media since there is no concept of complete shielding. Thus, if an attempt is made to apply the disc cartridge construction for optical discs to those used in photon mode optical information recording/reproducing apparatuses, there has been a problem of causing the above characteristic degradation, for example, by a stray light entering through a clearance between the slide shutter and the cartridge case. Although it is disclosed that the slide shutter slides relative to a cartridge shell in the disc cartridge of Japanese Unexamined Patent Publication No. 2004-362743, there is a possibility of creating a clearance between the cartridge shell and slide shutter due to the vibration of the slide shutter or the like since the slide shutter is merely placed on the cartridge shell. Accordingly, complete light shielding is difficult in this disc cartridge.

SUMMARY OF THE INVENTION

Accordingly, in view of the above problems, an object of the present invention is to make it difficult to degrade optical characteristics of a photon mode optical information recording medium with a simple construction.

In order to accomplish the above object, the present invention is directed to a disc cartridge accommodating a photon mode optical information recording medium, comprising a housing having an opening section, and a shutter disposed to be movable between a closing position to close the opening section and an opening position to open the opening section, wherein at least one of the housing and shutter includes a light path bending portion for bending a clearance between the shutter at the closing position and the housing at least at two points.

In the present invention, since stray lights propagating in the clearance between the housing and shutter is bent at least at two points by the light path bending portion, it can be made difficult for the stray lights entering through the clearance to reach the photon mode optical information recording medium even if there is the clearance between the housing and shutter, thereby making the degradation of the optical characteristics of the photon mode optical information recording medium more difficult to occur. Further, it can be suppressed to complicate the construction of the disc cartridge since the light path bending portion is simply provided at the housing or shutter.

The present invention is also directed to a photon mode optical information recording/reproducing apparatus for at least either recording or reproducing information in or from a photon mode optical information recording medium, comprising a holder for holding the above disc cartridge, and a structural element including a light shielding plate for suppressing the entrance of stray lights into the disc cartridge and attachable to the holder.

In the present invention, the degradation of the photon mode recording medium can be suppressed since the entrance of stray lights into the disc cartridge can be suppressed by the light shielding plate upon the optical recording.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, best modes for embodying the present invention are described in detail with reference to the accompanying drawings.

First Embodiment

The entire constructions of disc cartridges according to embodiments of the present invention and the complete light shielding capability of an optical information recording medium in which information is recorded in a photon mode are described.

Photon mode optical information recording media such as hologram media (hereinafter, merely referred to as “media”) generally contain a reaction inhibitor for easiness to handle. Thus, the media have nonlinear photosensitivity and are not photosensitized under the irradiation of low-power lights. Specifically, if an amount of light irradiated to the medium is equal to or below 100 nanojoules/cm2, optical characteristics are not degraded even if the light irradiation to the medium should be continued for a long time. Accordingly, what is at issue in the present invention is to prevent the entrance of stray lights equal to or above the above light irradiation amount, and a state of irradiation equal to or below the above light irradiation amount is called a completely light-shielded state. In this specification, that “the completely light-shielded state has been reached” is written as “the realization of complete light shielding” or merely “complete light shielding”.

Although the “disc-shaped medium” is described in this specification, this does not intend to limit the shape of the medium to a disc shape. In other words, it is sufficient for the media to be rotatable or movable plate-shaped media. In this case as well, similar effects can be obtained for the essence of the present invention.

Hereinafter, a first embodiment of the present invention is described.FIGS. 1A to 1Care exterior views and a section of a disc cartridge according to the first embodiment of the present invention.

InFIGS. 1A to 1C, identified by1is a disc case as a housing, by2a shutter and by3a disc-shaped medium used in photo-mode recording.

The disc case1is configured to have a rectangular shape in plan view and a specified thickness. The disc case1is hollow.

The disc case1has an opening section40formed in a range extending from one side surface portion1ato middle parts of an upper surface portion1band a lower surface portion1c. This opening section40is formed to have a rectangular shape in plan view, and opposite edge portions40aof the opening section40are parallel to each other. The opposite edge portions40amean the left and right edge portions inFIG. 1Cand indicate a pair of edge portions facing each other and constituting the upper surface portion1b(or a pair of edge portions facing each other and constituting the lower surface portion1c).

The shutter2is attached to the disc case1. The shutter2has a first lateral portion2acorresponding to the upper surface portion1bof the disc case1, a second lateral portion2bcorresponding to the lower surface portion1cof the disc case1and a connecting portion2cconnecting the first and second lateral portions2a,2b. The first and second lateral portions2a,2bare respectively formed to have the same rectangular shape, and arranged in parallel with the upper surface portion1band lower surface portion1cof the disc case1. The connecting portion2cis formed to have the same width as the first and second lateral portions2a,2b, and arranged in parallel with the side surface portion1aof the disc case1.

The shutter2is constructed to be movable between a closing position to close the opening section40(seeFIG. 1A) and an opening position to open the opening section40(seeFIGS. 1B and 1C). The shutter2is biased from the opening position toward the closing position by a biasing member such as a spring member (not shown) or the like accommodated in the disc case1.

The shutter2has shutter-side recesses43as an example of light path bending portions. The shutter-side recesses43are formed in the opposite end surfaces of the shutter2in a moving direction of the shutter2. The respective shutter-side recesses43are recesses having rectangular cross sections, and are formed in the first lateral portion2a, connecting portion2cand second lateral portion2bof the shutter2as shown inFIG. 2, so that any of the upper surface portion1b, side surface portion1aand lower surface portion1cof the disc case1is insertable thereinto. Since parts of the shutter2are inserted in parts of the disc case1, no optical clearance is formed between the shutter2and the disc case1.

When the shutter2is at the closing position as shown inFIG. 1A, the medium3is completely light-shielded. When the shutter2is at the opening position as shown inFIG. 1B, a part of the medium3is exposed to the outside. When the shutter2is at the opening position, a clamp bar of an optical recording/reproducing apparatus is, for example, accessible to a recording/reproducing area of the medium3and a clamp hole3a. It should be noted thatFIG. 1Cis a section of the disc cartridge along a cut plane I inFIG. 1B.

InFIG. 1A, the medium3is accommodated in the disc case1and completely light-shielded by the shutter2at the closing position and the disc case1. For example, as conceptually shown inFIG. 3, the edge portions40aat the opposite sides of the opening section40of the disc case1are inserted in the shutter-side recesses43when the shutter2is at the closing position. Thus, propagation paths of stray lights are bent at two points in the clearance between the disc case1and shutter2. Specifically, as shown by arrows A in FIG.3, the stray lights propagating from the outside of the disc case1toward the inside of the disc case1pass outside and along the disc case1toward the back side of the shutter-side recesses43and are then bent inward of the disc case1(first point). These stray lights propagating inward of the disc case1are bent to propagate along the disc case1(second point) in the shutter-side recesses43as shown by arrows B inFIG. 3. The stray lights bent at two points reach the inside of the disc case1, but the medium3is completely light-shielded since amounts of the stray lights are very small. SinceFIG. 3is drawn to facilitate the description, it does not necessarily dimensionally coincide withFIG. 1C.

Thus, the medium3can be completely light-shielded from external lights as long as the shutter2is not open as shown inFIG. 1B. The open state of the shutter2shown inFIG. 1Bis realized, for example, in the optical information recording/reproducing apparatus. At this time, an external force can be applied to open or close the shutter2, for example, by providing the optical information recording/reproducing apparatus with a shutter opening mechanism having an arm or the like.

The disc case1is comprised of two parts, e.g. an upper housing and a lower housing, and the medium3can be sealed in its accommodated state by constructing the upper and lower housings to be fittable or adherable to each other over the entire circumference of a connecting portion. By forming any one of the side surfaces of the disc case1by a detachable part, the medium3can be easily accommodated into the disc case1. In such a case, the medium3can be sealed by constructing this part to be fittable into or adherable to the disc case1over the entire circumference.

Since the medium3contains a material for photon-mode recording, an operation of accommodating the medium3needs to be performed under the irradiation of lights in a wavelength band where the medium3is not substantially photosensitized or in a darkroom where complete light shielding is possible. In the case of fabricating the disc cartridge in this way, there is no likelihood of the entrance of stray lights through the aforementioned fitting portion or adhering portion. However, in order to reliably exclude the stray lights through the clearances, it is also effective to seal up the above fitting portion or adhering portion, for example, with a seal tape made of a light reflecting material or light absorbing material capable of light shielding.

The essential point of the present invention is to realize complete light shielding between the disc case1and shutter2. As descried above, the medium3used in optical information recording using an optical photon mode is a so-called photosensitive member in the nature of the recording method and has sensitivity to lights having wavelengths equal to or below a visible light region. Thus, if a non-recorded area of the medium3is photosensitized, there is a problem of fatally degrading the characteristics such as a reduction of a recordable capacity. However, as described above, the photon mode optical information recording medium such as a holographic medium actually contains a reaction inhibitor for easiness to handle. Therefore, the medium has a nonlinear photosensitive characteristic and is not photosensitized under the irradiation of low-power lights. Specifically, if an amount of light irradiated to the medium3is equal to or below 100 nanojoules/cm2, optical characteristics are not degraded even if the light irradiation should be continued for a long time. Accordingly, the present invention aims to prevent the degradation of the characteristics of the medium caused by the entrance of stray lights equal to or above the above light irradiation amount. In the disc cartridge shown in this embodiment, for example, even under the direct sunlight, stray lights entering the inside of the disc case1can be remarkably attenuated and an amount of light irradiated to the medium3can be reduced to or below several 10 nanojoules/cm2if the shutter2is closed. This can eliminate a possibility of degrading the characteristics of the medium3due to an optical factor at least outside the optical information recording/reproducing apparatus.

Preferably, an exposed state of the medium3as shown in this embodiment is, in principle, realized only in the photon mode optical information recording/reproducing apparatus. Accordingly, it is necessary that the shutter2for realizing the complete light shielding cannot be easily opened when the medium3is outside the optical information recording/reproducing apparatus. In order to accomplish this, it is possible to provide a locking mechanism in the disc case. As shown inFIG. 4, a locking member46is for preventing the shutter2from being opened outside the optical information recording/reproducing apparatus or the like and provided in the disc case1. The locking member46includes a stopper47and a displacing mechanism for displacing this stopper47. This displacing mechanism is comprised of a spring member49having the base end thereof fixed to the disc case1and a magnet50fixed to the leading end of this spring member49. By having one end thereof fixed to the magnet50, the stopper47is displaceable between a locking position and an unlocking position as the spring member49extends and contracts. When the stopper47is at the locking position, a projection53provided in the shutter2is in contact with the stopper47, whereby the shutter2is locked. On the other hand, when the stopper47is at the unlocking position, the stopper47is not in contact with the projection53of the shutter2, whereby the shutter2is unlocked. The magnet50is, for example, movable toward an external magnet52disposed in the optical information recording/reproducing apparatus. By arranging the external magnet52and the magnet50in the disc case1such that parts thereof having the same polarity approach each other, the spring member49is compressed when the disc cartridge is set in the optical information recording/reproducing apparatus. Thus, the stopper47at the locking position is moved to the unlocking position and the shutter2can be unlocked. AlthoughFIG. 4shows an example in which the locking position is attained when the spring member49is extended and the unlocking position is attained when the spring member49is compressed, the locking position may be attained upon the compression of the spring member49and the unlocking position may be attained upon the extension of the spring member49. Further, the locking member46may be made accessible (for the unlocking operation) by forming a window (worked so as not to hinder the complete light shielding, e.g. by fitting a valve inside the disc case) through which, for example, a very thin needle-like pin is inserted.

As described above, since stray lights propagating in the clearances between the disc case1and shutter2are bent at least at two points by the light path bending portions in the first embodiment, it can be made difficult for the stray lights entering through the clearances to reach the medium3despite the presence of the clearances between the disc case1and shutter2. This can make it difficult to degrade the optical characteristics of the medium3. In addition, it can be suppressed to complicate the construction of the disc cartridge since the light path bending portions are provided in the disc case1or shutter2.

In the first embodiment, the light path bending portions are formed by the shutter-side recesses formed in the shutter in which the edge portions of the opening section in the housing are inserted when the shutter is at the closing position.

Accordingly, when the shutter is at the closing position, the edge portions of the opening section in the housing are located in the shutter-side recesses. Thus, stray lights are bent at least at two points upon propagating in the clearances between the housing and shutter, wherefore it can be made difficult for the stray lights to reach the photon mode optical information recording medium. Further, the entrance of stray lights can be suppressed with a simple construction of only providing the recesses in the shutter.

Second Embodiment

FIGS. 5A and 5Bshow a disc cartridge according to a second embodiment of the present invention. InFIGS. 5A and 5B, identified by4is a disc case as a housing, by5a shutter movably mounted in the disc case4and by6a disc-shaped medium used in photon mode recording.FIG. 5Ais a section showing a state where the shutter5is closed and the medium6is completely light-shielded andFIG. 5Bis a section showing a state where the shutter5is open and the medium6is partly exposed to the outside.

The shutter5has a first lateral portion5acorresponding to an upper surface portion4bof the disc case4, a second lateral portion5bcorresponding to a lower surface portion4cof the disc case4and a connecting portion (not shown) connecting the first and second lateral portions5a,5b. In the second embodiment, any of the first lateral portion5a, second lateral portion5band connecting portion is in the form of a flat plate having no recesses formed at the opposite ends thereof.

Similar to the first embodiment, the disc case4has an opening section56rectangular in plan view. Housing-side recesses58as an example of light path bending portions are provided at edge portions of the opening section56in this disc case4. The housing-side recesses58are formed at the opposite edge portions of the opening section56with respect to a moving direction of the shutter5. The respective housing-side recesses58are recesses of the disc case4having rectangular cross sections. Thus, the inner surfaces of the housing-side recesses58and the shutter5inserted thereinto are substantially parallel to each other. The respective housing-side recesses58are formed in the upper surface portion4a, side surface portion and lower surface portion4b.

When the shutter5is at the closing position, the opposite ends of the shutter5are inserted in the housing-side recesses58. In other words, parts of the shutter5are inserted in parts of the disc case4. Thus, stray lights propagating in clearances between the disc case4and the shutter5are bent at two points. Specifically, as shown by arrows A inFIG. 5A, the stray lights propagating from the outside of the disc case4toward the inside of the disc case4pass outside the shutter5toward the back sides of the housing-side recesses58and are then bent inward of the disc case4(first point). These stray lights propagating inward of the disc case4are bent to propagate along the shutter5in the housing-side recesses58(second point) as shown by arrows B inFIG. 5A. Since the stray lights are bent at two points before reaching the medium6, an amount of light reaching the medium6is remarkably reduced, whereby the medium6can be completely light-shielded. When the shutter5is opened, the rear end (left end inFIG. 5A) of the shutter5move toward the back sides of the housing-side recesses58at the shown left side, whereas the front end (right end inFIG. 5A) of the shutter5comes out of the housing-side recesses58at the shown right side.

According to our examination, lights can be effectively completely shielded by setting widths S of the clearances between the disc case4and shutter5to or below 200 μm. By setting the widths S of the clearances to or above 100 μm, smooth opening and closing movements of the shutter5can be ensured.

In order to stabilize the widths S of the clearances, it is possible to arrange spacers60between the disc case4and shutter5, for example, as shown inFIGS. 6A and 6B. The spacers60may be fixed to the disc case4or shutter5. The spacers60may be configured to have a narrow shape extending in the moving direction of the shutter5. The spacers60are arranged in the housing-side recesses58located in the upper surface portion4a, lower surface portion4band side surface portion4cof the disc case4and function as guides for the shutter5. In this way, a light-shielding effect can be ensured and smooth opening and closing movements of the shutter5can be realized. By adopting a disc cartridge construction shown in this example, even under the direct sunlight, stray lights entering the inside of the disc case4can be remarkably attenuated and an amount of lights irradiated to the medium6can be reduced to or below 10 nanojoules/cm2if the shutter5is closed. This can eliminate a possibility of degrading characteristics of the medium6due to an optical factor at least outside the optical information recording/reproducing apparatus.

Further, as shown inFIG. 7, guide grooves61for holding the spacers60may be formed in the housing-side recesses58. These guide grooves61are formed in the inner surfaces of the housing-side recesses58and extend in the opening and closing directions of the shutter5. The spacers60are held by being disposed in these guide grooves61.

As described above, in the second embodiment, the light path bending portions are formed by the housing-side recesses formed at the edge portions of the opening section in the housing so that the shutter at the closing position is located therein.

Accordingly, when being at the closing position, the shutter is located inside the housing-side recesses. Thus, stray lights are bent at least at two points upon propagating in the clearances between the disc case and shutter, wherefore it can be made difficult for the stray lights to reach the photon mode optical information recording medium. Further, the entrance of stray lights can be suppressed with a simple construction of only providing the recesses in the housing.

Further, the clearances of the housing and shutter are set equal to or larger than 100 μm and equal to or smaller than 200 μm in the second embodiment.

In this embodiment, smooth opening and closing movements of the shutter can be ensured by setting the clearances to or above 100 μm, and the entrance of stray lights can be effectively suppressed by setting the clearances to or below 200 μm.

Although each of the housing-side recesses58at the opposite sides is formed to be one recess and the shutter5is formed by one plate material in this example, the disc case4and shutter5may be constructed to be engaged with each other at a plurality of positions to provide a plurality of overlapping portions of the disc case4and shutter5, for example, as shown inFIG. 8. In this construction, the light path bending portions include shutter-side recesses63provided in the shutter5and housing-side recesses58provided in the disc case4. In the shown example, two shutter-side recesses63are provided in the thickness direction of the shutter5and three housing-side recesses58are provided in the thickness direction of the shutter5. When the shutter5is at the closing position, the opposite ends of the shutter5are located in the housing-side recesses58and the edge portions of the opening section in the disc case4are located in the shutter-side recesses63. Thus, stray lights propagating in the clearances between the disc case4and shutter5are bent at ten points.

In this mode, the light path bending portions include a plurality of shutter-side recesses formed in the shutter and a plurality of housing-side recesses formed in the edge portions of the opening section in the housing and, when the shutter is at the closing position, the edge portions of the opening section in the housing are located in the respective shutter-side recesses and the shutter at the closing position is located in the respective housing-side recesses.

Accordingly, the number of times stray lights propagating the clearances between the housing and shutter are bent can be increased. Therefore, the entrance of stray lights can be effectively reduced.

The other construction, functions and effects are similar to those of the first embodiment.

Third Embodiment

FIGS. 9A and 9Bshow a disc cartridge according to a third embodiment of the present invention. In the third embodiment, housing-side recesses are tapered.

InFIGS. 9A and 9B, identified by7a disc case, by8a shutter movably mounted in the disc case7and by9is a disc-shaped medium used in photon mode recording.FIG. 9Ais a section showing a state where the shutter8is closed and the medium9is completely light-shielded, andFIG. 9Bis a section showing a state where the shutter8is open and the medium9is partly exposed to the outside.

In the third embodiment, light path bending portions are formed by housing-side recesses formed in the opposite edge portions of an opening section65. A housing-side recess (hereinafter, “shielding-side groove”)66shown at the right side is a groove into which a front end portion8aof the shutter8is inserted when the shutter8is closed. This shielding-side groove66is a tapered recess whose width is narrowed toward the back side. The width mentioned here means a dimension in the thickness direction of the shutter. The shutter8and disc case7are in contact in the shielding groove66.

On the other hand, the housing-side recess (hereinafter, “accommodating-side groove67”) shown at the left side has a rear end portion8bof the shutter8located therein regardless of whether the shutter8is at the closing position or at the opening position. The accommodating-side groove67is comprised of an introducing portion67atapered to narrow its width toward the back side, and an accommodating-side recess67bcommunicating with the back side of the introducing portion67a. The width mentioned here means a dimension in the thickness direction of the shutter. This accommodating-side recess67bis formed to gradually widen its width from the backmost end of the introducing portion67a. The disc case7and shutter8are closest at the backmost end of the introducing portion67a.

In the third embodiment, parts of the shutter8are inserted in parts of the disc case7, and the housing-side recesses66,67are tapered along a moving direction of the shutter8. The shielding-side groove66is narrowed in its width as it extends away from the opening section65of the disc case7, and preferably has a part whose width is smaller than the thickness of the shutter8. By this construction, the shutter8and disc case7come into contact with each other when the shutter8is closed, wherefore the entrance of stray lights through the shielding-side groove66can be effectively prevented.

On the other hand, the contact of the shutter8and disc case7in the accommodating groove67is not preferable in order to smooth opening and closing movements of the shutter8. Accordingly, it is preferable to leave a clearance between the shutter8and disc case7. If the minimum width of this clearance, i.e. the width of the clearance at the backmost end of the introducing portion67ais 100 μm or larger, the shutter8can be smoothly moved. Further, by avoiding the collision of the shutter8with the disc case7as a result of movements of the shutter8, dust production can be prevented. On the other hand, there still remains a small possibility of the entrance of stray lights through the accommodating groove67. Such stray lights entering the disc case7through the accommodating groove67can be reduced by setting the minimum width of the clearance between the disc case7and shutter8, for example, to 200 μm or below.

Generally, in the tapered construction, a light having entered from a wider side toward a narrower side of a clearance propagates while being repeatedly reflected by the tapered wall surface many times. At this time, an incident angle on the wall surface gradually increases as the light propagates toward the narrower side of the clearance defined by the wall surface, and the number of reflection by the wall surface also increases. Thus, the light having entered is attenuated by being scattered or absorbed every time being reflected, wherefore there is an effect that the light hardly reaches the back side (narrower side of the clearance) of the tapered construction. For this reason, it can be understood that the construction of the tapered housing-side recesses66,67as shown in this example is effective in completely light-shielding the medium9. By adopting such a construction, even under the direct sunlight, stray lights entering the inside of the disc case7can be remarkably attenuated and an amount of lights irradiated to the medium9can be reduced to or below 10 nanojoules/cm2if the shutter8is closed. This can eliminate a possibility of degrading characteristics of the medium9due to an optical factor at least outside the optical information recording/reproducing apparatus. The shutter8and disc case7are preferably made of such a material as to absorb stray lights. In such a case, the attenuation of the stray light in the disc case7and shutter8for each reflection can be increased, wherefore a light shielding effect can be further increased. Here, a material obtained by mixing carbon or the like into a so-called plastic material such as polycarbonate, acrylic or vinyl chloride so as to be opaque or capable of light absorption in a visible light region can be cited as an example of such a material as to absorb stray lights.

As described above, the housing-side recess is tapered to gradually narrow its width in this embodiment.

Accordingly, the entrance of stray lights can be made more difficult since the clearance is narrowed along a propagation direction of the stray lights. Thus, the depth of the housing-side recess can be suppressed as compared to the case where the housing-side recess is formed to be parallel. Therefore, the enlargement of the housing can be prevented. Further, the management of the clearance width between the housing and shutter can be moderated, thereby making it easier to produce the disc cartridge.

The housing and shutter is preferably made of a light absorbing material. In this mode, the transmission of stray lights through the housing and shutter can be suppressed, therefore making it more difficult to degrade the optical characteristics of the photon mode optical information recording medium.

Although the width of the accommodating-side recess67bis shown to be widened toward the back side inFIGS. 9A and 9B, the present invention is not limited thereto. In short, similar effects can be obtained if such a clearance as not to hinder opening and closing movements of the shutter8is ensured.

Further, the present invention is not limited to the case where both the shielding-side groove66and the accommodating-side groove67are tapered. For example, one of them may be parallel. However, if one side is formed to be parallel, this groove needs to have a larger depth. Thus, for the miniaturization of the disc cartridge, the housing-side recesses66,67are preferably tapered.

As shown inFIG. 10, the opposite end portions8a,8bof the shutter8may be tapered and the shielding-side groove66and introducing portion67amay be formed to be parallel. In this case as well, clearances between the disc case7and shutter8are tapered.

Although the housing-side recesses66,67are tapered in the third embodiment, the shutter-side recesses43may be tapered in the first embodiment.

The other construction, functions and effects are similar to those of the second embodiment.

Fourth Embodiment

FIGS. 11A and 11Bshow a disc cartridge according to a fourth embodiment of the present invention. In the fourth embodiment, housing-side recesses have a wavy construction. With this construction as well, effects similar to those of the above tapered construction can be obtained.

FIGS. 11A and 11Bshow an example in the case where a medium is light-shielded by a disc case having wavy constructions at its parts for holding a shutter. InFIGS. 11A and 11B, identified by10is a disc case, by11a shutter movably mounted in the disc case10and by12is a disc-shaped medium used in photon mode recording.FIG. 11Ais a section showing a state where the shutter10is closed and the medium12is completely light-shielded, andFIG. 11Bis a section showing a state where the shutter11is open and a part of the medium12is exposed to the outside.

In the fourth embodiment, side walls of housing-side recesses (shielding-side groove66and accommodating-side groove67) formed in the opposite edge portions of an opening section65are formed to have wavy shapes along a moving direction of the shutter11. A part of the disc case10is inserted into the housing-side recesses66,67to hold a part of the shutter11by the disc case10.

Here, for smooth opening and closing movements of the shutter11, the contact of the shutter11and the side walls of the housing-side recesses66,67within the movable range of the shutter11is not preferable. Accordingly, it is preferable to leave clearances between the shutter11and the disc case10. If the minimum width of these clearances is set to or above 100 μm, the shutter11can be smoothly moved. Further, by avoiding the collision of the shutter11with the disc case10as a result of movements of the shutter11, dust production can be prevented. On the other hand, there still remains a small possibility of the entrance of stray lights through the housing-side recesses66,67, but such stray lights entering the disc case10through the housing-side recesses66,67can be reduced by setting the minimum width of the clearances between the disc case10and shutter11, for example, to 200 μm or below. This is because the shape of the space to the shutter11is substantially tapered by adopting one wavy configuration.

By adopting the disc cartridge construction shown in this example, even under the direct sunlight, stray lights entering the inside of the disc case10can be remarkably attenuated and an amount of light irradiated to the medium12can be reduced to or below 10 nanojoules/cm2if the shutter11is closed. This can eliminate a possibility of degrading characteristics of the medium12due to an optical factor at least outside the optical information recording/reproducing apparatus.

As described above, the housing-side recesses are formed to have wavy shapes in which widened parts and narrowed parts alternately repeat in the fourth embodiment.

Since stray lights are difficult to pass the narrowed parts of the housing-side recesses, the entrance of the stray lights can be made more difficult by having a plurality of narrowed parts in the housing-side recesses according to this mode. Thus, the management of the clearances between the housing and the shutter can be moderated, thereby making it easier to produce the disc cartridge.

The attenuation rate of stray lights can be set by selecting the taper angle and taper length in the aforementioned tapered groove construction. In the wavy groove construction of this example as well, the attenuation rate of stray lights can be set by selecting a wave period (or wavelength in a direction parallel to the moving direction of the shutter11) and amplitude (change of the spacing to the shutter11). In a case of making the shutter11and disc case10of such a material as to absorb stray lights, the attenuation of the stray light in the disc case10and shutter11for each reflection can be increased, wherefore a light shielding effect can be further increased.

Although the housing-side recesses66,67are formed to have wavy shapes in the fourth embodiment, the shutter-side recesses43may be formed to have wavy shapes in the first embodiment.

The other construction, functions and effects are similar to those of the third embodiment.

Fifth Embodiment

FIG. 12shows a disc cartridge according to a fifth embodiment of the present invention. In this embodiment, a shutter and a disc case are provided with wall structures for light shielding.

InFIG. 12, identified by13is a disc case, by14a,14bshutters movably mounted in the disc case13and by15a disc-shaped medium used in photon mode recording. Here,FIG. 12is a section showing a state where the shutters14a,14bare closed and the medium15is completely light-shielded.

The shutter is comprised of the first shutter14aand the second shutter14b. These first and second shutters14a,14bare separate parts. The first shutter14ais arranged between an upper surface portion13aof the disc case13and the medium15, and the second shutter14bis arranged between a lower surface portion13bof the disc case13and the medium15.

Opening sections69of the disc case13are not formed in a side surface portion unlike the first embodiment, and independently formed in the upper and lower surface portions13a,13b. Specifically, the disc case13is formed with the upper opening section69in the upper surface portion13aand the lower opening section60in the lower surface portion13b. The first and second shutters14a,14bare movable in opposite directions. Each of the first and second shutters14a,14bis formed by bending a flat plate material.

It should be noted that the opening section69of the disc case13may be formed with a side surface portion as in the first embodiment. In this case, a part of the first shutter14amay cover the opening section69formed in the side surface portion and a part of the second shutter14bmay be placed on the first shutter14a.

In the fifth embodiment, light path bending portions are formed by shutter-side projections L1and housing-side projections L2. Each shutter-side projection L1is formed by bending one end (rear end) of the shutter14a,14bwith respect to a moving direction. The shutters14a,14bare arranged at such positions that the shutter-side projections L1are located at ends of shutter closing directions. Each shutter-side projection L1is bent to extend from a shutter main body14carranged in parallel with the medium15in a direction toward a side opposite to the medium15.

The housing-side projections L2are provided at the upper and lower surface portions13a,13bof the disc case13. The respective housing-side projections L2are formed at such positions as to face the shutter-side projections L1in the closing directions of the shutters14a,14b.

A hollow part in the disc case13is dimensioned such that the shutter-side projections L1are movable in the shutter opening and closing directions. The disc case13is formed with the housing-side projections L2by causing the edge portions of the opening sections69to project toward the medium15. Thus, the vicinities of the opening sections69are made sufficiently narrower than the height of the shutter-side projections L1, and the housing-side projections L2are present in the shutter closing directions of the shutter-side projections L1. Therefore, the shutter-side projections L1are constantly located in the disc case13.

With the shutters14a,14bclosed, spatial clearances are eliminated by the proximate arrangement or contact of the shutter-side projections L1and housing-side projections L2, whereby a light-shielding effect can be obtained. Even if clearances are formed between the shutter-side projections L1and housing-side projections L2, complete light shielding can be realized since stray lights propagating in the clearances are bent at two points. Specifically, as shown in an arrow A inFIG. 13, the stray light propagating in the clearance is, for example, bent along the shutter-side projection L1after propagating the clearance between the shutter main body14cof the first shutter14aand the housing-side projection L2(first point). Then, as shown by an arrow B inFIG. 13, this stray light is bent at the leading end of the shutter-side projection L1after propagating upward (second point). Since the stray light is bent at two points before reaching the medium15, an amount of light reaching the medium15is remarkably reduced, whereby the medium15is completely light-shielded.

If opening and closing movements of the shutters14a,14bare considered, the shutter-side projections L1can be formed only at the rear ends of the shutters14a,14bas shown inFIG. 12. Accordingly, at the front end sides of the shutters14a,14b, it is effective to form housing-side recesses S1as light path bending portions in the disc case13. When the shutters14a,14bare at the closing positions, the front ends of the shutters14a,14bare inserted into these housing-side recesses S1. Thus, the shutter14can be held in the disc case13. Therefore, the complete shielding of the medium15can be realized. In this case, the widths of the clearances between the shutters14a,14band the disc case13are preferably set, for example, to about 100 to 200 μm.

As described above, in the fifth embodiment, the light path bending portions are formed by the shutter-side projections formed by bending the ends of the shutter and the housing-side projections formed at the housing to face the shutter-side projections.

Since stray lights are bent at two points along the housing-side projections and shutter-side projections in this mode, it can be made difficult for the stray lights to reach a photon mode optical information recording medium. In addition, it can be suppressed to complicate the constructions of the shutter and housing.

Although the shutter is comprised of the first and second shutters14a,14bas separate parts in the fifth embodiment, the present invention is not limited thereto. For example, the shutters may be integrally formed as in the first embodiment. In such a case, the shutters cannot be moved in opposite directions unlike the fifth embodiment. Therefore, the upper and lower shutter-side projections L1are respectively provided at the same side (e.g. left side inFIG. 12). In this case, the upper and lower housing-side projections L2are also provided at the same sides of the opening sections69. Accordingly, in this case, the size of the shutter-side projections L1largely influences the thickness of the disc cartridge, which might lead to an increase in the entire thickness of the disc cartridge. Therefore, the shutters14a,14bare preferably constructed to independently open in opposite directions at the upper and lower sides of the disc case13as in the fifth embodiment. This can suppress an increase in the thickness of the disc case13.

The other construction, functions and effects are similar to those of the first embodiment.

Sixth Embodiment

FIGS. 14A and 14Bshow a disc cartridge according to a sixth embodiment of the present invention.

InFIGS. 14A and 14B, identified by16is a disc case, by17a shutter movably mounted in the disc case16, by18a disc-shaped medium used in photon mode recording and by19a skirt portion as an example of an elastic member.FIG. 14Ais a section showing a state where the shutter17is closed and the medium18is completely light-shielded, andFIG. 14Bis a section showing a state where the shutter17is open and the medium18is partly exposed to the outside.

In the sixth embodiment, light path bending portions are formed by a housing-side recess70formed in the disc case16. A rear end portion of the shutter17at a closing position is located in this housing-side recess70, and is inserted toward the back side of the housing-side recess70as the shutter17is opened.

The skirt portion19is made of an elastic material such as rubber, and fixed to the outer surface of an upper surface portion of the disc case16near an opening section71. When the shutter17is at the closing position as shown inFIG. 14A, the skirt portion19made of an elastic member and the shutter17can be held in contact without defining any clearance therebetween. Specifically, the skirt portion19is inclined in a moving direction of the shutter17by a force closing the shutter17. Since the shutter17is biased in a closing direction, a biasing force of the shutter17and an elastic force of the skirt portion19act against each other while the shutter17is closed. Accordingly, the shutter17is held at the closing position and the shutter17and the skirt portion19are kept in close contact, whereby complete light shielding can be maintained. Since the skirt portion19is arranged near the opening section71at the front end side of the shutter17, the shutter17is separated from the skirt portion19while being opened as shown inFIG. 14B. Therefore, the skirt portion19returns to its original stable shape due to its elasticity.

As described above, in the sixth embodiment, one end portion of the shutter at the closing position is insertable into the housing-side recess, and the housing is provided with the elastic member with which the other end portion of the shutter at the closing position is held in close contact.

In this mode, the entrance of stray lights propagating in the clearances between the shutter and the housing-side recess can be suppressed at the one end side of the shutter, whereas the entrance of stray lights can be suppressed by the close contact of the shutter with the elastic member at the other end side of the shutter.

As shown inFIGS. 15A and 15B, the elastic member may be a stopper20made of an elastic material as an example of an elastic structural element. Similar to the skirt portion19, this stopper20is fixed to an outer surface of the disc case16. The stopper20is arranged at such a position that the front end of the shutter17bites in a side surface of the stopper20when the shutter17is closed. Accordingly, when the shutter17is at the closing position, the shutter17bites in the side surface of the stopper20, whereby the shutter17and the stopper20are held in close contact. At this time, a biasing force acting in the closing direction of the shutter17and an elastic force of the stopper20act against each other. Accordingly, the shutter17and the stopper20can be kept in close contact and complete light shielding can be maintained.

The other construction, functions and effects are similar to those of the first embodiment.

Seventh Embodiment

FIGS. 16A and 16Bshow a disc cartridge according to a seventh embodiment of the present invention. The seventh embodiment is one example of the case in which a medium is light-shielded by providing wall structures for light shielding at parts of a shutter and forming grooves engageable with these wall structures in a disc case.

InFIGS. 16A and 16B, identified by21is a disc case, by22a shutter movably mounted in the disc case21and by23a disc-shaped medium used in photon mode recording.FIG. 16Ais a section showing a state where the shutter22is closed and the medium23is completely light-shielded, andFIG. 16Bis a section showing a state where the shutter22is open and the medium23is partly exposed to the outside.

In the seventh embodiment, light path bending portions are formed by shutter-side projections73and housing-side recesses74. The shutter-side projections73are provided at the front and rear ends of the shutter22, and formed by bending ends of the shutter22with respect to its moving directions toward the disc case21(inward).

The housing-side recesses74are formed in the outer surfaces of an upper surface portion21aand a lower surface portion21bof the disc case21. In each of the upper and lower surface portions21a,21b, the housing-side recesses74are formed at the opposite sides of an opening section75with respect to the moving directions of the shutter22.

The respective housing-side recesses74are formed to extend in a direction normal to the moving directions of the shutter22and to have a slightly larger rectangular cross section than the shutter-side projections73. The housing-side recesses74are arranged at such positions as to face the shutter-side projections73when the shutter22is at the closing position.

The shutter22is comprised of a first member22aand a second member22b. As shown inFIGS. 17A and 17B, the first member22ais a plate member having an L-shaped vertical section and is arranged from the upper surface portion21ato a side surface portion21cof the disc case21. The second member22bis a plate member having an L-shaped vertical section and is arranged from the lower surface portion21bto the side surface portion21cof the disc case21. The first member22aand second member22bare placed one over the other on the side surface portion21cof the disc case21. By the shutter22having such a construction, the shutter-side projections73are displaceable between inserted positions where they are inserted in the housing-side recesses74and separated positions where they are separated from the housing-side recesses74. The shutter-side projections73are arranged at the outer side of the disc case21and the separated positions are located more outward than the inserted positions.

The first member22aand second member22bare preferably pulled toward the inner side of the disc case23using biasing means such as unillustrated springs. The first member22aand second member22bmay include, for example, protuberances76in order to be displaced outward along the thickness direction of the disc case21against biasing forces of the biasing means. Then, the shutter-side projections73can be easily moved from the inserted positions to the separated positions utilizing these protuberances76. It should be noted that the protuberances76may have any shape such as a ring shape, hook shape or column shape. The shutter22can be distanced from the disc case21by holding or hooking these protuberances76by means of special members such as members in the optical information recording/reproducing apparatus. However, the protuberances76preferably have a minimum possible projecting distance so as not to impair the shutter function. In other words, it is necessary to prevent the shutter from being opened by human hands. Instead of the protuberances76, the first member22aand second member22bmay be formed with grooves, and the shutter22may be distanced utilizing these grooves.

In the seventh embodiment, the shutter22cannot be easily opened due to the meshing engagement or strong contact of the shutter-side projections73and housing-side recesses74if the shutter22is closed outside the optical information recording/reproducing apparatus. When the shutter22is closed, the medium23can be completely light-shielded similar to the examples described above. Specifically, when the shutter22is at the closing position, the shutter-side projections73are inserted in the housing-side recesses74. Thus, if external stray lights try to enter the disc cartridge, they propagate through clearances between the shutter-side projections73and housing-side recesses74. The stray lights propagating toward the back sides of the housing-side recesses74are bent at the leading ends of the shutter-side projections73(first point). The bent stray lights hit the side walls of the housing-side recesses74to be bent again (second point). The stray lights propagate in the clearances between the side walls of the housing-side recesses74and the shutter-side projections73, and hit the shutter22to be bent again upon coming out of the housing-side recesses74(third point). At this time, if there should be any clearance between the shutter22and disc case21, the stray lights enter the opening section75through this clearance. However, since the stray lights are already bent at three points, an amount of light entering the opening section75can be sufficiently reduced.

In order to open the shutter22, the first member22aand second member22bmay be distanced from the disc case21utilizing the protuberances76and then may be slide in directions substantially parallel to the outer surfaces of the disc case21. In this way, the medium23can be partly exposed.

As described above, in this embodiment, the light path bending portions are formed by the shutter-side projections formed by bending the opposite ends of the shutter and the housing-side recesses formed in the housing in conformity with the shutter-side projections.

Since the shutter-side projections are respectively provided at the opposite ends of the shutter in this mode, the entrance of stray lights can be suppressed at the opposite sides of the shutter, whereby it can be made more difficult to degrade optical characteristics of the photon mode optical information recording medium. By adopting this construction, there can be provided a disc cartridge capable of sufficiently performing complete light shielding with a simple construction. Further, since it becomes difficult for a user, for example, to easily open the shutter and expose the medium unlike conventional optical disc media, a possibility of making media, particularly those for photon mode recording unusable by error operations can be largely reduced.

In the seventh embodiment, the shutter-side projections are formed by bending the ends of the shutter inward, arranged at the outer side of the housing, and displaceable between the inserted positions where they are inserted in the housing-side recesses and the separated positions located more outward than the inserted positions.

In this mode, when the shutter-side projections are at the inserted positions, stray lights are bent at two points, wherefore it can be made more difficult for the stray lights to reach the photon mode optical information recording medium. On the other hand, since the shutter cannot be moved to the opening position unless the shutter-side projections are moved from the inserted positions to the separated positions, an inadvertent opening of the shutter can be prevented when it is not intended to open the shutter.

In the seventh embodiment, the shutter is comprised of a plurality of members, which are constructed to be partly placed one over the other.

In this mode, the shutter can be constructed by a plurality of members while a stray light shielding effect is maintained, whereby a degree of freedom in designing the shutter can be improved.

It should be noted that the shutter22may be integrally formed by a spring member. Specifically, the shutter22may integrally include a first lateral portion, a second lateral portion and a connecting portion connecting the first and second lateral portions. The entire shutter22is deformed as the connecting portion is warped, whereby the shutter-side projections73of first and second lateral portions can be displaced between the inserted positions and separated positions.

The other construction, functions and effects are similar to those of the first embodiment.

Eighth Embodiment

FIG. 18shows a disc cartridge according to an eighth embodiment of the present invention. InFIG. 18, identified by24is a disc case, by25a shutter movably mounted in the disc case24and by26a disc-shaped medium used in photon mode recording.

The disc case24according to the eighth embodiment differs from that of the seventh embodiment in that bulging portions24care provided, but the others are the same as in the seventh embodiment. The bulging portions24care thickened portions so that an upper surface portion24aand a lower surface portion24bof the disc case24project more outward than the shutter25. Thus, the outermost surfaces of the shutter25are located more inward than the outer surfaces of the disc case.

In the eighth embodiment, the housing includes the bulging portions projecting more outward than the shutter.

In this mode, since the bulging portions of the housing project more outward than the shutter, a risk of exposing a photon mode optical information recording medium by a user or the like opening the shutter can be more effectively reduced. By this construction, it becomes more difficult to open the shutter, for example, by fingers or tweezers, wherefore a risk of exposing a non-recorded medium by the user opening the shutter can be even more effectively reduced.

The other construction, functions and effects are similar to those of the seventh embodiment.

Ninth Embodiment

FIGS. 19A and 19Bshow a disc cartridge according to a ninth embodiment of the present invention.

InFIGS. 19A and 19B, identified by27is a disc case, by28a shutter movably mounted in the disc case27and by29a disc-shaped medium used in photon mode recording.FIG. 19Ais a section showing a state where the shutter28is closed and the medium29is completely light-shielded, andFIG. 19Bis a section showing a state where the shutter28is open and the medium29is partly exposed to the outside.

The ninth embodiment differs from the seventh embodiment in that the shutter28is arranged inside the disc case27. Shutter-side projections78are bent toward the disc case27(outward). The shutter-side projections78are arranged inside the disc case27, and separated positions are located more inward than inserted positions. In order to enable a movement of the shutter28, a hollow part in the disc case27is larger than in the seventh embodiment.

Housing-side recesses79are formed in the inner surfaces of upper and lower surface portions27a,27bof the disc case27. In the upper and lower surface portions27a,27b, the respective housing-side recesses79are provided at the opposite sides of an opening section80with respect to moving directions of the shutter28.

The shutter28is comprised of a first member28aand a second member28b. The first member28aopens and closes the opening section80of the upper surface portion27aand the second member28bopens and closes the opening section80of the lower surface portion27b. The first and second members28a,28bmay be so constructed as to be biased from the inner side toward the outer sides of the disc case27by means of biasing means such as unillustrated springs.

In order to open the shutter28, the shutter28may be pressed inward of the disc case27, for example, by means of members in an optical information recording/reproducing apparatus to displace the shutter-side projections78to the separated positions, and the shutter28may be slid in a direction substantially parallel to the outer surfaces of the disc case27in this state to be opened. In this way, the medium29can be partly exposed.

As described above, in the ninth embodiment, the shutter-side projections are formed by bending the ends of the shutter outward, arranged inside the housing, and displaceable between the inserted positions where they are inserted in the housing-side recesses and the separated positions located more inward than the inserted positions.

In this mode, when the shutter-side projections are at the inserted positions, stray lights are bent at two points, wherefore it can be made more difficult for the stray lights to reach a photon mode optical information recording medium. On the other hand, since the shutter cannot be moved to the opening position unless the shutter-side projections are moved from the inserted positions to the separated positions, an inadvertent opening of the shutter can be prevented when it is not intended to open the shutter. By adopting this construction, there can be provided a disc cartridge capable of sufficiently performing complete light shielding with a simple construction. Further, since it becomes difficult for a user, for example, to easily open the shutter and expose the medium unlike conventional optical disc media, a possibility of making media, particularly those for photon mode recording unusable by error operations can be largely reduced.

The other construction, functions and effects are similar to those of the seventh embodiment.

Tenth Embodiment

FIGS. 20A to 20Cshow a disc cartridge according to a tenth embodiment of the present invention. In this embodiment, a disc case is formed with a plurality of opening sections having different shapes.

InFIGS. 20A to 20C, identified by30is a disc case, by31a shutter movably mounted in the disc case30, by32a shutter having a different shape from the shutter31, by33a disc-shaped medium used in photon mode recording and by34an opening section formed when the shutter32is opened. The opening section34has a different purpose from an opening section82.

Many of generally used photon recording media such as hologram media are made of organic materials. Thus, upon being photosensitized by a light having a specified wavelength, polymerization from monomers to polymers occurs along a light intensity distribution in a medium. This generates a substantial change in the refractive index of the media and the index is recorded. For example, in shift multiplexing holographic recording, a multiplexed hologram is formed while slightly displacing a hologram recording position. Thus, monomers present in a certain area are consumed (changed to polymers) little by little. Generally, since a part or the entirety of a recording light (signal light and reference light) is used as a reproduced light in a holographic recording/reproducing apparatus, polymerization is caused to occur by the reproduced light if there still remain monomers. At this time, since the consumption of the monomers is accompanied by the absorption of the reproduced light and a change in the refractive index of the media, a reproduced signal in the case of reproduction while consuming the monomers and the one in the case of reproduction in a state where there is no monomer consumption differ. Thus, for example, in a state containing a great number of monomers to be actually consumed, there is a problem that the signal changes every time being reproduced. In order to avoid this problem, an incoherent light is normally irradiated to a recorded area of the medium after the completion of the recording to consume all the remaining monomers (generally, called “curing”). Since a light source used for curing preferably emits an incoherent light as described above, an LED or the like is provided in the apparatus in many cases, for example, separately from a laser light source used for optical recording/reproducing. Although it depends on the type of the medium, sufficient light irradiation is necessary for curing in order to completely consume remaining monomers. Accordingly, it is essential to give sufficient energy as an integrated light amount expressed by a product of an irradiation power density and an irradiation time.

FIG. 20Ais a perspective view showing a state where the disc cartridge is outside an optical information recording/reproducing apparatus. Specifically, the both shutters31,32are closed.FIG. 20Bis a perspective view showing a state of the disc cartridge when the disc cartridge is inserted into the optical information recording/reproducing apparatus for optical recording. At this time, the shutter31is opened and the shutter32is closed.FIG. 20Cis a perspective view showing a state of the disc cartridge when curing is performed simultaneously with optical recording in the optical information recording/reproducing apparatus. At this time, the both shutters31,32are open.

The construction shown in this example enables the curing of an already recorded area simultaneously with information recording. Specifically, the disc case30and shutter31, and the disc case30and shutter32are similar to the constructions described above, and the medium is completely light-shielded in the state ofFIG. 20A. In other words, any of the constructions according to the first to ninth embodiments can be adopted for the shutters31and32.

The shutters31,32are preferably independently slidable. For example, if the shutters31,32are separately and independently formed, both are separately movable. Thus, only either one of optical recording and curing can be performed or optical recording and curing can be simultaneously performed.

In the tenth embodiment, the housing is formed with a plurality of opening sections, for each of which the corresponding shutter is provided.

In this mode, the entrance of stray lights can be suppressed even in the case where the housing is formed with a plurality of opening sections having different purposes.

Further, in the tenth embodiment, the respective shutters are independently movable.

In this mode, the respective shutters can be opened according to needs. This can avoid an inadvertent opening of the shutters and can make it more difficult to degrade optical characteristics of a photon mode optical information recording medium.

Although the shutter has an integral construction in the first to fourth, sixth and tenth embodiments, the present invention is not limited thereto and arbitrary openings of the disc case can be formed, for example, by two or more shutters. At this time, similar light-shielding effects can be obtained by placing at least parts of a plurality of shutters arranged at the same opening section one over another or holding parts of the plurality of shutters each other.

Eleventh Embodiment

In order to completely shield lights in a photosensitive wavelength band irradiated to a medium, light shielding by an approach taking into account the materials of the disc case and shutter is necessary in addition to the realization of complete light shielding by the disc cartridge construction as in the above described examples. For example, since a general hologram medium or the like has sensitivity to visible lights (particularly lights having wavelengths equal to or below 550 nm), it is necessary not to use an inexpensive plastic used for general optical disc cartridges, but to use an expensive material containing carbon or the like as materials for the disc case and shutter. Therefore, we studied a mix of a light absorbing material with an inexpensive plastic material and the use of a disc cartridge comprised of a thicker disc case and a shutter.

Specifically, organic pigments having a large characteristic of absorbing lights in a wavelength band equal to or below 550 nm were mixed into polycarbonate, and plates having various thicknesses were produced experimentally. Then, light transmission characteristics of these plates were compared. As a result of this experiment, a relationship between the plate thickness and the transmittance for light having a wavelength of 532 nm was: transmittance of about 3% with a plate thickness of 0.5 mm, transmittance of about 0.005% with a plate thickness of 0.7 mm, transmittance of about 0.0001% with a plate thickness of 1.0 mm and transmittance of about 0.000001% or below with a plate thickness of 2 mm.

Generally, light irradiation intensity under direct sunlight in the case of strongest sunshine is said to be about 80000 luxes (=80000 lumens/m2). Out of it, an energy amount in a wavelength band for photosensitizing the above hologram medium can be thought to be about 100 watts/m2at the outside. Since 1 watt=1 joule/sec., the above energy amount is about 10 millijoules/cm2/sec. On the other hand, the recording of a hologram medium is performed by an energy of about 10 microjoules per hologram having a size of, e.g. 2 mm×2 mm. If the energy of unnecessary lights (in the wavelength band in which photosensitive members react) irradiated to the medium is given 25 millijoules/cm2as an integrated energy, the medium is degraded. In other words, if an uncovered medium is left under strong direct sunlight, it is degraded in about 2.5 seconds. If actual use is considered from these estimation and experimental result, the transmittance of the disc case or shutter needs to be reduced to or below 0.01% so that the integrated energy does not reach 25 millijoules/cm2even if the medium is left, for example, for five hours under the direct sunlight.

From our experimental result was deduced a result that the light irradiation mount to the medium could lie within the aforementioned range with a thickness of about 0.7 mm of above if the above material was used for the disc case, shutter and the like. The thickness of most common hologram media is about 1 mm at present. If a minimum spacing between the medium and the disc case or shutter to ensure a mechanical margin for the rotation of the medium is 0.8 mm (about the same as optical discs such as DVDs), the disc cartridge sufficiently ensuring an optical characteristic degradation can be obtained by setting the thickness of the entire disc cartridge to or above 4 mm. Further, the transmittance of the disc case or shutter needs to be set to or below 0.00007% in order to prevent the integrated energy from reaching 25 millijoules/cm2even if the medium is left for 500 hours under the direct sunlight as a more severe condition. In the case of using a material similar to the above for the disc case, the light irradiation amount to the medium inside can lie within the aforementioned range if the disc case has a thickness of 2 mm or larger. Therefore, the disc cartridge having high reliability can be provided.

Twelfth Embodiment

The disc cartridges capable of complete light shielding and effectively used in photon mode optical information recording are described in the first to eleventh embodiments, whereas an optical information recording/reproducing apparatus using the disc cartridge shown in any one of the first to eleventh embodiments is described in a twelfth embodiment.

One of most important factors of a photon mode optical information recording/reproducing apparatus is the light shielding of a medium during information recording. Since common optical recording/reproducing apparatuses represented by magnetooptical discs and DVDs do not necessitate an optical covering structure, an external light brought in through a clearance of a medium inserting portion or the like reaches a disc cartridge and a medium. However, in a photon mode optical information recording/reproducing apparatus, sufficient stray light shielding needs to be performed when a medium is exposed in the apparatus.

Accordingly, we considered the following construction.FIG. 21shows an exemplary construction for suppressing the entrance of stray lights to the exposed medium upon the optical recording in an optical information recording/reproducing apparatus.

InFIG. 21, identified by35is a disc cartridge having a complete light shielding construction by enclosing a medium, by36a tray as a holder for holding the disc cartridge35in the optical information recording/reproducing apparatus, and by37aand37bstructural elements having parts that come into contact with the disc cartridge35or tray36without any clearance to it. The tray36and structural elements37a,37bare provided in the optical information recording/reproducing apparatus.

For example, in the case of adopting a holographic recording method of the transmission type, a light irradiating portion and a signal light receiving portion of an optical head85are arranged at the opposite sides of the disc cartridge35as shown inFIG. 22. The light irradiating portion includes a signal section85afor irradiating a signal light beam to the medium35athrough a lens and a reference section85bfor irradiating a reference light beam to the medium35athrough a lens. Further, the signal light receiving portion includes a signal section85chaving an imaging device85eor the like for detecting the signal light beam, and a reference section85dhaving a beam stopper85for the like on which the reference light beam is incident. The signal light beam and reference light beam are incident on the medium35ain different directions in a Y-Z plane. In the case of adopting an angle multiplexing method as the holographic recording method, multiplexing recording needs to be performed by changing the incident angles of the signal light beam and reference light beam in the Y-Z plane inFIG. 22. Further, in the case of recording in an arbitrary area extending from the inner periphery to the outer periphery of the medium35a, the entire optical head85including the lenses, the imaging device85eand the like needs to be moved along a radial direction (Y-direction inFIG. 22) of the medium35a. Thus, it is essential that any of the tray36and the structural elements37aand37bdoes not hinder an optical or mechanical access of an optical part such as the optical head85to the medium35a.

Thus, as shown inFIG. 21, an opening section36bis formed in a bottom surface portion36aof the tray36, whereas the structural elements37a,37bare provided with light shielding plates37cat the opposite sides of an opening section of the disc cartridge35. The opening section36bof the tray36is formed in a range including the opening section of the disc cartridge35placed on the bottom surface portion36a.

Each of the structural elements37a,37bis attached to the tray36, and includes a main portion37d, leg portions37eformed at the opposite ends of the main portion37d, and the light shielding plates37cprovided on the main portion37d. The structural elements37a,37bare coupled to the tray36by holding the tray36by both leg portions37e. The tray36is sandwiched between the structural elements37a,37b.

Each main portion37dhas substantially the same shape as the bottom surface portion36aof the tray36, and is formed with an opening section37f. This opening section37fis formed in a range including the opening section of the disc cartridge35.

The light shielding plates37cin the form of flat plates are provided at the opposite sides of the opening section37fin a tangent direction (X-direction) of the medium35a. In other words, since the optical head85is movable along the radial direction (Y-direction) of the medium, the light shielding plates37care not provided at the opposite sides of the opening of the disc cartridge35with respect to Y-direction.

The light shielding plates37care wall structures standing up in a direction perpendicular to the medium35aand parallel to Y-direction. By the light shielding plates37c, the entrance of stray lights to the medium35afrom the opposite sides with respect to X-direction can be prevented. Thus, considerable light shielding can be performed, for example, in spaces87above and below the disc cartridge35defined by the light shielding plates37cand medium35aand the characteristic degradation of the medium due to an optical factor in the optical information recording/reproducing apparatus can be avoided. Thus, the restriction of the arrangement of members and the like around the tray36in the optical information recording/reproducing apparatus can be suppressed.

As shown inFIG. 23, an optical information recording/reproducing apparatus88is provided with a controller89, the optical head85, a recording/reproducing unit90, a driving mechanism (first driving mechanism)91for the tray36, a driving mechanism (second driving mechanism)92(for the structural elements37a,37b), a shutter opening mechanism93, a driving mechanism (third driving mechanism)94for the optical head85, etc. The first driving mechanism91is for moving the tray36between an outside position and an inside position. The outside position is a position where the tray36is moved out of the apparatus, and the inside position is a position where the tray36is located in the apparatus. The second driving mechanism92is for moving the structural elements37a,37bbetween joined positions and separated positions. The joined positions are positions where the structural elements37a,37bare joined with the tray36, and the separated positions are positions where the structural elements37a,37bare separated from the tray36. The shutter opening mechanism93is for moving a shutter35bof the disc cartridge35between a closing position and an opening position and includes, for example, an arm (not shown) accessible to the shutter35bof the disc cartridge35placed on the tray36at the inside position. The third driving mechanism94is for moving a lens and the like of the light irradiating portion and changing the orientations thereof. This driving mechanism94also moves the optical head85itself.

In the optical information recording/reproducing apparatus, the disc cartridge35is placed on the tray36, for example, serving as a holding mechanism for the disc cartridge35, and this tray36is inserted into the apparatus by means of the first driving mechanism91. Then, the second driving mechanism92moves the structural elements37a,37bfrom the separated positions to the joined positions. Thus, the structural elements37a,37bsandwich the tray36together with the disc cartridge35from above and below and adhere to the tray36. Here, if a recess is so formed in a movable range of the shutter35bas to prevent the contact of the disc cartridge35and the structural elements37a,37b, the shutter can be easily opened and closed. It should be noted that the second driving mechanism may be omitted. In such a case, the structural elements37a,37bare formed to be joined, and the tray36having the disc cartridge35placed thereon is inserted between the both structural elements37a,37b.

When the structural elements37a,37badhere to the tray36, the shutter35bof the disc cartridge35is closed. This shutter35bis preferably opened upon confirming the light shielding by the structural elements37a,37b. For example, sensors95as detectors for detecting a light amount may be arranged in the spaces87. A control operation in this case is shown inFIG. 24. First, when the tray36is moved from the outside position to the inside position to introduce the disc cartridge35into the apparatus (Step ST1), light amounts in the spaces87are detected by the sensors95(Step ST2). In the controller89, judgment is made as to whether or not the opening of the shutter35bis permissible depending on whether or not the light amounts are equal to or below a specified value (Step ST3). The shutter35bis kept at the closing position until the light amounts fall to or below the specified value. When the light amounts fall to or below the specified value, the arm is driven to open the shutter35b(Step ST4). In this way, an inadvertent opening of the shutter35bof the disc cartridge35with stray lights present in the spaces87, for example, due to the trouble of the apparatus can be avoided, whereby the degradation of the medium35acan be effectively suppressed.

In order to avoid the entrance of stray lights through a disc cartridge insertion opening of the optical information recording/reproducing apparatus, the disc cartridge35and structural elements37a,37bare preferably united and moved along the thickness direction of the disc cartridge (vertical direction) after the disc cartridge35is inserted. In this way, light shielding in the spaces formed by the disc cartridge35or tray36and the structural elements37a,37bcan be more effectively performed.

The twelfth embodiment concerns an information recording/reproducing apparatus for at least either recording or reproducing information in or from a photon mode optical information recording medium, and is provided with the holder for holding the disc cartridge, and the structural elements including light shielding plates for suppressing the entrance of stray lights into the disc cartridge and attachable to the holder.

Accordingly, the entrance of stray lights into the disc cartridge can be suppressed by the light shielding plates upon the optical recording, wherefore the degradation of the photon mode recording medium can be suppressed.

The twelfth embodiment is further provided with the detectors for detecting the light amounts in the spaces formed by the disc cartridge and the light shielding plates, and the controller for making judgment as to whether the opening or closing of the shutter is permissible based on the detection result by the detectors.

In this mode, an inadvertent opening of the shutter despite the presence of stray lights due to the trouble or the like of the apparatus can be reliably prevented.

The present invention is applicable to a disc cartridge accommodating a photon mode optical information recording medium and also to an information recording/reproducing apparatus for at least either recording or reproducing information in or from a photon mode optical information recording medium.