Recording and/or reproducing apparatus with a disc cartridge temperature sensor

A recording and/or reproducing apparatus into which a disc cartridge accommodating a disc is loaded and in which information signals are adapted to be recorded on or reproduced from the disc. A temperature sensor is provided within the apparatus for contacting with and sensing the temperature of the disc cartridge. By this temperature sensor, the temperature of the loaded disc cartridge is sensed and an output of a light source of an optical head is controlled on the basis of the sensor output to effect recording and/or reproduction of the information signals under an optimum operating state.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a recording and/or reproducing apparatus in which 
a disc cartridge having a disc-shaped recording medium for writing and/or 
reading information signals accommodated in a cartridge proper is loaded 
and in which recording and/or reproduction of the information signals is 
effected on or from the recording medium in the disc cartridge. More 
particularly, it relates to a recording and/or reproducing apparatus 
provided with a temperature sensor for sensing the temperature of a disc 
cartridge loaded therein, and to a disc cartridge loaded into a recording 
and/or reproducing apparatus for sensing the temperature of a recording 
medium accommodated within a cartridge proper. 
2. Description of the Prior Art 
In a recording medium adapted for recording and/or reproducing information 
signals by magnetic, optical or photomagnetic means, the temperature of 
the recording medium during writing or reading is crucial since it 
influences recording and reproduction significantly. 
In the case of a magneto-optical disc, for example, a high laser power is 
required during recording or erasure because the temperature of a magnetic 
thin film needs to be raised to higher than a Curie temperature, while a 
lower laser power is required during reproduction for which the recorded 
information is not demagnetized. These laser powers need to be determined 
as a function of the temperature of the recording medium that is, it needs 
to be set to a value which will allow for optimum recording or 
reproduction of information signals. For example, it may occur that, even 
if the recording laser power is set to an optimum value for a certain 
temperature of the recording medium, the recording laser power may become 
too high or too low due to changes in the recording medium temperature, 
such that the direction of magnetization cannot be inverted 
satisfactorily. Similarly, if the laser power during the reproduction or 
erasure is too high or too low, it may occur that the recorded information 
signals are demagnetized or are not erased completely. 
The conventional practice for sensing the temperature of the recording 
medium is to provide the cartridge proper with a small orifice through 
which the recording medium temperature is sensed by means of a radiation 
thermometer provided in the recording and/or reproducing apparatus to 
permit a laser to be radiated at an optimum laser power as a function of 
temperature changes of the recording medium. 
However, in this case, fine dust and dirt may intruded through the orifice 
into the inside of the cartridge to cause errors in information signals to 
which interfere with recording or reproduction. Although the orifice may 
be stopped when not in use, it becomes necessary to provide a member for 
stopping the orifice and means for permitting the sliding of the member, 
as well as driving means for sliding the member on the recording and/or 
apparatus, resulting in an increased number of component items and 
increased costs. On the other hand, the temperature of an order of 
30.degree. to 40.degree. C. cannot be measured accurately with a radiation 
thermometer. 
There has also been proposed by the Japanese Patent KOKAI Publication No. 
1-191329(1989) an arrangement in which a temperature sensor for sensing 
the temperature of a recording medium is mounted integrally on an optical 
head and adapted to be moved therewith radially of the recording medium 
for sensing the temperature of the recording medium. 
However, in this case, the temperature of the recording medium can not be 
measured accurately by reason of a gap between the temperature sensor and 
the recording medium. Thus a laser beam cannot be irradiated at an optimum 
laser power as a function of the prevailing temperature of the recording 
medium, so that information signals cannot be recorded satisfactorily. 
OBJECT AND SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a recording and/or 
reproducing apparatus adapted for sensing the temperature of a disc 
cartridge loaded therein. 
It is another object of the present invention to provide a recording and/or 
reproducing apparatus whereby the temperature of the recording medium of 
the loaded disc cartridge may be sensed accurately and recording and/or 
reproduction may be made under an optimum condition based on the thus 
sensed temperature. 
It is yet another object of the present invention to provide a disc 
cartridge adapted for sensing the temperature of a recording medium 
accommodated within a cartridge proper. 
A recording and/or reproducing apparatus according to the present invention 
is provided, within the inside thereof, with a temperature sensor adapted 
for contacting with a disc cartridge loaded therein for sensing the 
temperature of the disc cartridge. 
A recording and/or reproducing apparatus according to the present invention 
is provided with a temperature sensor for sensing the temperature of the 
disc cartridge on a member adapted for contacting with a disc cartridge 
loaded therein. 
A disc cartridge according to the present invention includes a disc-shaped 
recording medium rotatably accommodated within a cartridge proper which 
has its outer surface formed at least partially of the same material as 
that of the recording medium which recording medium includes a recording 
layer formed on a substrate for writing and/or reading information 
signals. 
A recording and/or reproducing apparatus according to the present invention 
includes a disc cartridge loaded therein for recording and/or reproducing 
information signals on or from a recording medium of the disc cartridge, 
and a temperature sensor mechanism adapted for contacting with a region of 
the disc cartridge formed of the same material as that of the substrate of 
the recording medium for sensing the temperature of the region of the disc 
cartridge. 
The recording and/or reproducing apparatus, provided in one aspect of the 
present invention, includes a temperature sensor which, when a disc 
cartridge comprised of a disc-shaped recording medium accommodated in a 
cartridge proper is loaded in the apparatus, is brought into contact with 
the cartridge proper to sense its temperature so that the temperature of 
the cartridge proper may be determined instantaneously. 
In addition, the recording and/or reproducing apparatus, provided in one 
aspect of the invention, includes a temperature sensor provided on a 
member contacting with the cartridge proper for sensing the temperature of 
the cartridge proper, so that the temperature of the cartridge proper may 
similarly be determined on loading the disc cartridge in the recording 
and/or reproducing apparatus. 
With a disc cartridge, provided in another aspect of the present invention, 
at least a portion of the outer surface of the cartridge proper is formed 
of the same material as the material of the substrate of the recording 
medium. When the disc cartridge is loaded in a recording and/or 
reproducing apparatus provided in a third aspect of the invention, a 
temperature sensor mechanism provided in the recording and/or reproducing 
apparatus is brought into contact with the portion of the cartridge proper 
formed of the same material as the substrate material for sensing its 
temperature. The temperature thus sensed is approximately equal to the 
temperature of the recording medium, because the portion is of the same 
material as the substrate material. Hence, with the disc cartridge of the 
present invention, the temperature of the recording medium accommodated 
within the cartridge proper may be grasped by sensing the temperature of 
the cartridge proper. 
Since no orifice for temperature detection is provided in the present disc 
cartridge, the recording medium may be safeguarded against contamination 
by foreign matter such as dust and dirt. 
With the recording and/or reproducing apparatus, provided in the third 
aspect of the invention, since the temperature sensor mechanism is 
provided therein for contacting with and sensing the temperature of the 
portion of the cartridge proper formed of the same material as the 
material of the substrate of the recording medium, the temperature of the 
portion of the cartridge proper may be grasped instantaneously.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
By referring to the drawings, certain preferred embodiments of the present 
invention will be explained in detail. 
In the first place, a disc cartridge loaded on a recording and/or 
reproducing apparatus according to a first embodiment of the present 
invention will be explained. 
Referring to FIG. 2, the disc cartridge includes a disc 1 as a disc-shaped 
recording medium and a cartridge proper 2 rotatably accommodating the disc 
1. The disc 1 is constituted by a substrate and a recording layer formed 
thereon for writing and/or reading information signals. 
The disc 1 is an optical disc, a magneto-optical disc or a floppy disc, for 
example, having a recording layer on at least one surface, and information 
signals may be written and/or read on or from the recording layer by 
optical or magneto-optical means. A chucking hub 1a is provided at the 
center of the disc 1 for chucking the disc 1 on a disc table provided in 
the recording and/or reproducing apparatus, which will be explained 
subsequently. 
The cartridge proper 2 is constituted by rectangular casings, that is, an 
upper half 2a and a lower half 2b, of a size to accommodate the disc 1 
therein. The upper half 2a and the lower half 2b are formed of the same 
polycarbonate resin as that of the substrate of the disc 1 and are abutted 
and connected to each other to make up the cartridge proper 2. The disc 1 
is accommodated rotatably within the so-assembled cartridge 2. 
The upper half 2a and the lower half 2b are formed with rectangular 
apertures 3a, 3b, respectively, extending towards the middle from a side 
edge of the cartridge proper 2 by which the disc cartridge is loaded in 
the recording/reproducing apparatus. By these apertures 3a and 3b, the 
disc 1 accommodated within the cartridge proper 2 and the chucking hub 1a 
are exposed to the outside throughout its inner and outer peripheries. Of 
the upper and lower halves 2a and 2b, the lower half 2b is formed with 
positioning holes 4a, 4b in which are engaged positioning pins, not shown, 
provided on the recording/reproducing apparatus. 
The cartridge proper 2 is provided with a shutter member 5 which is movable 
relative to the cartridge 2 and adapted for opening or closing the 
apertures 3a and 3b. The shutter member 5 is a thin sheet of metal or 
synthetic resin in the shape of a letter U for clamping the front side of 
the cartridge 2 from the upper and lower sides thereof. That is, the 
shutter member 5 is made up of an upper plate section 5a facing the major 
surface of the upper half 2a, a lower plate section 5b facing the major 
surface of the lower half and a front plate section 5c interconnecting the 
upper and lower plate sections. 
The shutter member 5 has its front plate section 5c supported by a front 
side edge of the cartridge proper 2 is movable along the front side edge 
of the cartridge proper 2 as shown by an arrow A in FIG. 2. Except when 
the shutter member 5 is loaded on a drive device, the shutter member is 
biased by a torsion coil spring mounted within the cartridge proper 2 for 
closing the apertures 3a and 3b. Hence, under the normal state, the disc 1 
is protected by the shutter member 5 against accidental external force or 
intrusion of dust and dirt into the cartridge 2. 
An embodiment of the recording/reproducing apparatus, into which the above 
disc cartridge is loaded for recording and/or reproducing on or from the 
disc 1 of the disc cartridge, is hereinafter explained. 
In the present embodiment, the recording/reproducing apparatus is explained 
as an apparatus for recording/reproducing information signals on or from a 
magneto-optical disc. 
In the present apparatus, shown in FIG. 1, a spindle motor 7 adapted for 
chucking and rotating the disc 1 accommodated in the cartridge proper 2 is 
provided on a chassis 6. On the foremost part of the spindle motor 7, 
there is mounted a disc table 7a for attracting the chucking hub 1a of the 
disc 1 for rotatably supporting the disc 1. On the chassis 6, there is 
provided height position setting pin 8 supporting the cartridge 2 to 
prevent the disc 1 loaded on the disc table 7a from abutting on the 
cartridge 2 when the cartridge 2 is loaded on the recording/reproducing 
apparatus. The height position setting pin 8 is adapted for supporting the 
vicinity of the side edge of the lower half 2b on the front side thereof 
provided with the shutter member 5. 
On the chassis 6, there is additionally provided a positioning pin 9 for 
fixing the relative position between the disc 1 and the spindle motor 7 
for assuring stable rotation of the disc 1. The position setting pin 9 is 
provided on the opposite side of the height reference pin 8 with the 
spindle motor 7 in between. The pins 8 and 9 are inserted into positioning 
pins 4a and 4b provided in the lower half 2b of the cartridge proper 2 for 
controlling the positioning of the cartridge proper 2. In this state, the 
disc 1 accommodated within the cartridge proper 2 is loaded on the disc 
table 7a and raised from the inner surface of the lower half 2b out of 
collision with the cartridge proper 2 so as to be rotated within the 
cartridge proper 2. 
The apparatus is provided with an optical head adapted for writing and 
reading information signals on or from the disc 1 accommodated within the 
cartridge proper 2. The optical head is constituted by a semiconductor 
laser 10, an optical system, made up of a collimator lens 11, a beam 
shaping prism 12, a polarization beam splitter 13 and an object lens 14 
and adapted for irradiating a laser beam from the semiconductor laser 10 
in the form of a predetermined small sized spot in the disc 1, and a servo 
system, made up of a sensor lens 15, a beam splitter 16, a servo sensor 
17, a signal sensor 18 and a polarization plate 19 and adapted for driving 
the object lens 14 on the basis of signals from the light reflected from 
the disc 1 for focusing and tracking. 
Thus the laser beam radiated from the semiconductor laser 10 is collimated 
by a collimator lens 11 and transmitted through beam shaping prism 12 and 
polarization beam splitter 13 so as to form a small sized spot on the disc 
1 (magneto-optical disc) by means of the object lens 14. The light 
reflected from the magneto-optical disc is transmitted through the object 
lens 14 and split by beam splitter 16 into two lights which are separately 
converged on the servo sensor 17 and the signal sensor 18. The 
polarization plate 19 is provided ahead of the signal sensor 18 for 
converting changes in the polarization state by photomagnetic effects into 
intensity modulation. The servo sensor 17 detects focusing and tracking 
signals in any known manner, such as by an astigmatic method or a 
push-pull method. The detected servo signals are fed back to a lens 
actuator to drive the object lens 14 to effect automatic focusing and 
automatic focusing. 
In the present apparatus, a temperature sensor 20 for contacting with the 
cartridge 2 for sensing its temperature is provided on the chassis 6. The 
temperature sensor 20 is provided in proximity to the positioning pin 9 
and adapted to contact with the cartridge proper 2 on loading the 
cartridge proper 2. That is, when the cartridge proper 2 is supported by 
the height reference pin 8 provided on the chassis 6, and is 
position-controlled by the positioning pin 9, the temperature sensor 20 is 
adapted to contact the lower half 2b of the cartridge proper 2. 
Meanwhile, a central processing unit 21 is connected to the temperature 
sensor 20, and the temperature sensed by the temperature sensor is 
transmitted to the central processing unit 21. In the unit 21, the power 
of the laser light radiated from the semiconductor laser 10 is controlled 
on the basis of the sensed temperature from the temperature sensor 20. 
For writing information signals on the disc 1 in the above described 
recording and/or reproducing apparatus, a bias magnetic field is impressed 
on the disc 1 by a magnetic head 22, facing the object lens 14 with the 
disc 1 in-between, at the same time that a laser beam is radiated by the 
semiconductor laser 10 for converging the laser beam at a recording 
region. 
The laser beam at this time is controlled by the central processing unit 
21, based on the temperature sensed by the temperature sensor 20 
contacting the disc cartridge proper 2, that is, the temperature 
approximately equal to that of the disc 1, so that the beam in outputted 
at an optimum recording power. If the disc temperature is changed as a 
function of occasional recording regions of the disc 1, the disc cartridge 
temperature is instantly sensed by the temperature sensor 20, whereby the 
laser light is outputted at an optimum recording power on the basis of 
occasional changes, in the disc cartridge temperature. 
For reproduction and erasures, the laser light is irradiated at all times 
on the recording surface of the disc 1 at an optimum laser power as a 
function of the disc temperature. Thus there is no risk of demagnetization 
of the recorded information or incomplete erasure, so that satisfactory 
data recording and/or reproduction is assured. 
Also, in the case of an optical disc, an optimum laser power required for 
recording or reproduction may be outputted, depending on occasional 
changes in the disc temperature, so that fluctuations in the pit size are 
not concomitantly produced, so that stable recording/reproducing, is 
assured. 
In the above described embodiment, the laser power is controlled on the 
basis of the sensed disc cartridge temperature, it is also possible to 
control the readout position of recording signals for the magnetic head 22 
based on the sensed temperature. In this case, a sensor for sensing the 
temperature within the apparatus may be separately provided in the 
apparatus and positioning of the magnetic head 22 may be effected on the 
basis of the temperature difference between the temperature detected by 
the sensor and the temperature sensor 20. 
Although the temperature sensor 20 is provided on the chassis 6, the sensor 
20 may also be provided within an inner recess of the positioning pin 9. 
That is, the sensor 20 is embedded within an inner recess of a positioning 
part 99 of the positioning pin 9 contacting with the inner periphery of 
one of the positioning holes 4a, 4b so that the main body of the sensor is 
exposed to the outer surface of the positioning part 9a, while terminals 
20a, 20b of the temperature sensor 20 are led out at a terminal of a shank 
part 9b attached to the chassis 6 and connected to the CPU 21 as shown in 
FIG. 4. 
In this manner, when the cartridge proper 2 is loaded and the positioning 
pin 9 is engaged in the positioning holes 4a in the lower half 2b, the 
temperature sensor 20 provided within the positioning pin 9 is brought 
into contact with the inner periphery of the positioning holes 4a or 4b 
for sensing the temperature of the cartridge proper 2. Based on the sensed 
temperature, a laser light with the optimum laser power controlled by the 
CPU 21 may be outputted, or the readout position of the recording signals 
by the magnetic head may be controlled. 
Alternatively, the temperature sensor 20 may also be provided within an 
inner recess of the height position setting pin 8. To this end, the sensor 
20 is embedded within the interior of a supporting part 8a contacting with 
the cartridge proper 2 so that the main body of the sensor 20 is exposed 
on the outer surface of the supporting part 8a. As in the case of the 
positioning pin 9, the terminals 20a, 20b of the temperature sensor 20 are 
led out at a terminal of a shank part 8b secured to the chassis 6. 
It is noted that, when the temperature sensor 20 is provided within the 
inner recess of the pin 8 or 9, these pins may be formed of a material 
having good head conductivity, such as glass or copper, to assure more 
reliable detection of the cartridge temperature. 
Alternatively, the positioning pin 9 may be formed of a material exhibiting 
good heat conductivity, and the temperature sensor 20 may be directly 
contacted with the positioning pin 9, as shown in FIG. 6. 
The temperature sensor 20 may be provided at any other member than the 
positioning pin 9 which may be contacted with the cartridge proper 2. For 
example, the temperature sensor may be contacted with the height reference 
pin 8 or a shutter opening/closing pin for opening or closing the shutter 
member 5. In this case, the height reference pin 8 or the shutter 
opening/closing pin need to be formed of a material exhibiting good heat 
conductivity. In this manner, the same result as that when the temperature 
sensor 20 is provided within the interior of the pin 9 or 8 may be 
achieved. 
With the above described arrangement, the cartridge proper of the disc 
cartridge and the transparent substrate of the disc 1 are not necessarily 
formed of the same material. The cartridge proper in general is formed 
from synthetic resin, such as ABS resin, whereas the transparent substrate 
of the disc 1 is formed of polycarbonate resin or polymethyl methacrylate 
(PMMA), so that temperature characteristics, for example, of these 
materials differ from each other. Hence, some error is introduced if the 
temperature of the cartridge proper of the disc cartridge is sensed. In 
the following, description is made of second and third embodiments of the 
present invention, in which this problem may be overcome to assure more 
accurate detection of disc temperatures. 
A disc cartridge according to the second embodiment is shown in FIGS. 7 and 
8 and is comprised of a disc 31, as a disc-shaped recording medium, and a 
cartridge proper 32 rotatably accommodating the disc 31, which is 
comprised of a substrate and a recording layer formed thereon for reading 
and/or writing information signals. 
The disc 31 is an optical disc, a magneto-optical disc or a floppy disc, 
for example, having a recording layer on at least one surface, and 
information signals may be written and/or read on or from the recording 
layer by optical or magneto-optical means. A chucking hub 31a is provided 
at the center of the disc 31 for chucking the disc 31 on a disc table 
provided in the recording and/or reproducing apparatus, which will be 
explained subsequently. 
The cartridge proper 32 is constituted by rectangular casings, that is, a 
upper half 32a and a lower half 32b, of a size the accommodate the disc 31 
therein. The upper half 32a and the lower half 32b are abutted and 
connected to each other to make up the cartridge proper 32. The disc 31 is 
accommodated rotatably within the so-assembled cartridge proper 32. 
The upper half 32a and the lower half 32b are formed with rectangular 
apertures 33a, 33b, respectively, extending towards the middle from a side 
edge of the cartridge proper 32 by which the cartridge is loaded on the 
recording/reproducing apparatus. By these apertures 33a and 33b, the disc 
31 accommodated within the cartridge proper 2 and the chucking hub 31a are 
exposed to outside throughout its inner and outer peripheries. It is noted 
that a chucking hub 31a provided centrally of the disc 31 also is exposed 
to outside by these apertures 33a, 33b. 
The cartridge proper 32 is provided with a shutter member 34 which is 
movable relative to the cartridge proper 32 and which is adapted for 
opening or closing the apertures 33a and 33b. The shutter member 34 is a 
thin sheet of metal or synthetic resin in the shape of a letter U for 
clamping the front side of the cartridge proper 32 from the upper and 
lower sides thereof. That is, the shutter member 34 is made up of an upper 
plate section 34a facing the major surface of the upper half 32a, a lower 
plate section 34b facing the major surface of the lower half 32b and a 
front plate section 34c interconnecting the upper and lower plate 
sections. 
The shutter member 34 has its front plate section 34c supported by the 
front side of the cartridge proper 32 and is movable along the front side 
of the cartridge proper 32 as shown by an arrow A in FIG. 2. Except when 
the shutter member 34 is loaded on a recording/reproducing apparatus, the 
shutter member is biased by a torsion coil spring, not shown, mounted 
within the cartridge proper 32 for closing the apertures 33a and 33b. 
Hence, under the normal state, the disc 31 is protected by the shutter 
member 34 against an external force or intrusion of dust and dirt into the 
cartridge proper 32. 
With the present disc cartridge, for detecting the temperature of the disc 
31 accommodated within the cartridge proper 32, a sensed region 36 formed 
of the same material as that of the disc substrate, that is a transparent 
substrate of an optical disc or a magneto-optical disc or a resilient 
substrate of a floppy disc, is provided in the vicinity of a side edge of 
the lower half 32a opposite to the side edge provided with an inadvertent 
erasure inhibit button 35. 
The sensed region 36 is formed integrally with the lower half 32b and 
provided at a position in register with a temperature sensor mechanism 
provided in the recording and/or reproducing apparatus which will be 
explained subsequently. Thus the sensed region 36 is formed of the same 
material as that of the disc substrate by two-color molding so that the 
sensed region of the lower half 32b in contact with the temperature sensor 
mechanism presents a different color from that of the main portion of the 
lower half. In the present embodiment, the sensed region 36 is formed of a 
polycarbonate resin, as is the substrate of the disc 31. 
The above mentioned temperature sensor mechanism is adapted to contact with 
the sensed region 36 for instantly detecting the temperature of the sensed 
region. The sensed temperature is the same as the temperature of the disc 
31 inasmuch as the sensed region 36 is of the same material as that of the 
disc 31. In other words, by sensing the temperature of the sensed region 
36, the temperature of the disc 31 may be determined instantaneously. 
In the present embodiment, a region of the lower half in contact with the 
temperature sensor mechanism is formed with a different color from the 
main region of the lower half by two-color molding so as to be used as the 
sensed region 36. However, the lower half 32a in its entirely may be 
formed of the same material as that of the substrate of the disc 31. Still 
alternatively, a chip formed of the same material as the disc substrate 
may also be applied to that region of the outer surface of the lower half 
32b which is in contact with the temperature sensor mechanism. 
In the following, a recording and/or reproducing apparatus, into which the 
above described disc cartridge is loaded and in which information signals 
are recorded or reproduced on or from the disc 31 of the disc cartridge, 
according to the present invention, is explained. It is noted that the 
apparatus is adapted for recording or reproducing the information signals 
on or from a magneto-optical disc. 
In the present apparatus, as shown in FIG. 9, a laser beam radiated from a 
semiconductor laser is collimated by a collimator lens 38 and transmitted 
through a beam shaping prism 39 and a polarization beam splitter 310 so as 
to be converged by an object lens 311 to form a small-sized spot on the 
disc 31, that is a magneto-optical disc. The light reflected from the 
magneto-optical disc is again transmitted through the object lens 311 and 
reflected by the polarization beam splitter 310 so as to be separated from 
an incident light on the recording medium. The reflected light or return 
light is transmitted through a sensor lens 312 and split by beam splitter 
313 into two lights which are separately converged on a signal sensor 314 
and a servo sensor 315. A polarization plate 316 is provided ahead of the 
signal sensor 314 for converting changes in the polarization state by 
photomagnetic effects into intensity modulation. The servo sensor 315 
detects focusing and tracking signals in any known manner, such as by an 
astigmatic method of a push-pull method. The detected servo signals are 
fed back to a lens actuator, not shown, to drive the object lens 311 to 
effect automatic focusing and automatic focusing. 
A chucking hub 31a of the disc 31 accommodated in the cartridge proper 32 
of the disc cartridge is engaged with a spindle motor 317 provided in the 
recording and/or reproducing apparatus to cause rotation of the disc 31 in 
unison with the spindle motor 317. 
In register with a sensed region 36 provided on the cartridge proper 32 of 
the disc cartridge, there is provided a temperature sensor unit 318, which 
is a temperature sensor mechanism adapted for contacting with the sensed 
region 36 for sensing the temperature of the sensed region 36. The 
temperature sensor unit 318 is provided at the distal end of a compression 
spring 320 provided on a chassis 319 of the main body of the 
recording/reproducing apparatus so that the temperature sensor unit 318 
may be moved vertically towards and away from the sensed region 36 during 
loading of the disc cartridge. More specifically, before loading of the 
disc cartridge, the spring 320 is in its fully extended state. On 
completion of the loading the sensor unit 318 is pressed by the cartridge 
proper 32, so that the spring 320 is in its compressed state. In short, 
the temperature sensor unit 318 is pressed by the spring 320 into pressure 
abutment with the sensed region 36 provided on the cartridge proper 32. 
Meanwhile, a central processing unit 321 is connected to the temperature 
sensor unit 318, and the temperature as sensed by the temperature sensor 
unit 318 is transmitted to the central processing unit 321. The central 
processing unit 321 is provided with a laser drive control circuit whereby 
the power of the laser light radiated from the semiconductor laser 37 is 
controlled on the basis of the sensed temperature from the temperature 
sensor unit 318. 
For writing information signals on the disc 31 in the above described 
recording and/or reproducing apparatus, a bias magnetic field is impressed 
on the disc 31 by a magnetic head 322, facing the object lens 311 with the 
disc 31 in-between, at the same time that a laser beam is radiated by the 
semiconductor laser 37 for converging the laser beam in a recording 
region. The laser beam at this time is controlled by the central 
processing unit 321 on the basis of the temperature of the sensor 36 of 
the cartridge proper 32 as measured by the temperature sensor unit 318 
provided in contact with the sensor region 36, that is a temperature 
approximately equal to the disc temperature, and is outputted at an 
optimum recording power. If the disc temperature is changed as a function 
of occasional recording regions of the disc 31, the temperature at the 
region 36 at this time is instantly sensed by the temperature sensor unit 
318, whereby the laser light is outputted at an optimum recording power on 
the basis of occasional changes in the disc cartridge temperature. 
For reproduction and erasures, the laser light is irradiated at all times 
on the recording surface of the disc 31 at an optimum laser power as a 
function of the disc temperature. Thus there is no risk of demagnetization 
of recorded information or incomplete erasure, so that satisfactory data 
recording and/or reproduction is assured. 
It will be seen from above that, with the recording and/or reproducing 
apparatus recording to a first aspect of the present invention, since a 
temperature sensor unit for detecting the cartridge temperature is 
provided in contact with the cartridge proper, or a temperature sensor 
unit is provided on a member contacting with the cartridge proper, the 
laser power may be controlled to an occasionally optimum value during 
recording, reproduction and erasure on the basis of the sensed temperature 
for realizing stable recording, reproduction and erasure of information 
signals. 
Above all, for recording or reproducing signals on or from a 
magneto-optical disc, the readout position of the magnetic head may be 
controlled on the basis of the sensed cartridge temperature for realizing 
accurate magnetic head positioning. 
With the disc cartridge according to the second aspect of the present 
invention, since at least part of the outer surface of the cartridge 
proper is formed of the same material as that of the substrate of the 
recording medium, the temperature of the recording medium accommodated 
within the cartridge proper may be grasped from the cartridge temperature 
on loading the disc cartridge on a recording and/or reproducing apparatus 
according to a third aspect of the present invention. 
On the other hand, since no orifice or the like for temperature detection 
is provided in the present disc cartridge, the recording medium may be 
protected against contamination by foreign matter, such as dust and dirt. 
Finally, with the recording and/or reproducing apparatus according to the 
third aspect of the present invention, since the temperature sensor unit 
is provided for contacting with and sensing the temperature of a region of 
the disc cartridge which is formed of the same material as the substrate 
of the recording medium of the disc cartridge, on loading the disc 
cartridge, the temperature of the sensed region that is of the recording 
medium, may be grasped instantaneously. The laser power may be controlled 
on the basis of the sensed temperature for achieving satisfactory 
recording and/or reproduction of information signals on or from the 
recording medium.