1.  Field of the Invention
The present invention relates to an information recording apparatus for recording an information signal on an information record medium of a recordable type such as a phase change type optical disk, and an information reproducing apparatus for reproducing the information signal from the information record medium. 
2.  Description of the Related Art
Typically, an optical disk of a read only type has a main record area and sub record areas.  A main information signal indicative of main information, such as video information or music information, is recorded on the main record area.  The sub record areas are respectively disposed on an inner circumference side and an outer circumference side so as to sandwich the main record area between them.  Usually, the sub record area located on the inner circumference side of the main record area is referred to as a lead-in area, and the sub record area located on the outer circumference side of the main record area is referred to as a lead-out area.  For example, as shown in FIG.  1, in a case of a DVD (Digital Versatile Disk) 200, an area between a diameter of 48 mm and a diameter of 116 mm is a main record area 201, an area between a diameter of 46 mm and a diameter of 48 mm is a lead-in area 202, and an area between a diameter of 116 mm and a diameter of 117 mm is a lead-out area 203. 
The lead-in area 202 and the lead-out area 203 are formed in order to optimally read in the main information signal recorded between the innermost circumference track and the outermost circumference track of the main record area 201. 
If it is temporarily assumed that the lead-in area and the leadout area are not present in the read only type optical disk, there may be a possibility of an occurrence of an event described below.  When the main information signal recorded on the innermost circumference track or the outermost circumference track is read in, the movement of a pickup is limited in such a way that the pickup moves towards the innermost circumference track or the outermost circumference track.  At this time, if a disturbance occurs, the movement of the pickup may be not correctly controlled.  Thus, the pickup may pass the innermost circumference track and move further to the inner circumference side or pass the outermost circumference track and move further to the outer circumference side.  Information tracks (pits) are not formed outside the main record area.  Hence, if the pickup goes outside of the main record area, it is impossible to obtain the information necessary for the movement control of the pickup (for example, the information to generate a tracking error signal).  As a result, the movement control of the pickup can not be done in the worst case. 
In order to solve such a problem, the lead-in area 202 is formed further to the inner circumference side of the innermost circumference track in the main record area 201, and the lead-out area 203 is formed further to the outer circumference side of the outermost circumference track in the main record area 201.  And, the information tracks (pits) are formed on the lead-in area 202 and the lead-out area 203.  Special signals indicative of the lead-in area or the lead-out area are recorded on these information tracks as sub information signals. 
Moreover, content information with regard to the main information signal recorded on the main record area, attribute information of the disk and the like are recorded together with the special signals as the sub information signals, depending on the kind of the optical disk. 
As for an optical disk of a recordable type, which is referred to as a xe2x80x9crecordable optical diskxe2x80x9d, a record track, a guide track and pre-pits are formed on its recording surface.  The guide track is a track for guiding a record light beam to the record track (for example, a groove track), and is referred to as a land track, for example.  The pre-pits are pits for recording pre-information to specify positions (addresses) on the disk.  When recording information on the recordable optical disk, a recording apparatus can specify the record position of the information by detecting the guide track and the pre-pits and can correctly control the movement of the pickup and the radiation of the light beam. 
The recordable optical disk also has areas corresponding to the lead-in area and the lead-out area of the read only type optical disk.  The guide track and the pre-pits are also formed in these areas.  When recording the information on the recordable optical disk, the recording apparatus records the above-mentioned special signals (if necessary, the content information and the attribute information) on these areas corresponding to the lead-in area and the lead-out area.  Accordingly, the recordable optical disk after the information is recorded thereon and the read only type optical disk are unified in format.  Therefore, the information recorded on the recordable optical disk can be reproduced by a reproducing apparatus for reproducing the read only type optical disk. 
The area in which the information tracks (pit rows) are formed, namely, the main record area can be recognized by the reproducing apparatus by detecting the special signals recorded on the recordable optical disk.  In a case of a reproducing apparatus which employs a manner of generating a tracking error signal based on a phase difference of a light beam reflected by the pit rows, it is necessary that the main record area can be exactly recognized in order to surely carry out the movement control of the pickup.  Hence, from the viewpoint of such an aspect, it is important to record the special signals. 
In the conventional recording apparatus, when the information is recorded on the recordable optical disk, the main information signal is firstly recorded on the recordable optical disk.  After all the main information signals to be recorded are recorded, the special signals (if necessary, the content information and the attribute information) are recorded on the lead-in area and the lead-out area.  As a result, in order to record the information on the recordable optical disk, the conventional recording apparatus needs not only the recording process of recording the main record information but also the recording process of recording the special signals.  This results in a problem that it takes a long time to carry out the recording process. 
It is therefore an object of the present invention to provide an information recording apparatus and an information reproducing apparatus, which can shorten a time required to record information on an optical disk. 
The above-mentioned object can be achieved by an information recording apparatus in accordance with the present invention.  The information recording apparatus is an apparatus for recording main information and sub information onto an information recording medium, which has a main recording area and a sub recording area.  The main information is input from an external source. 
The information recording apparatus includes: an receiving device that receives the main information input from the external source; an accumulating device that accumulates the main information received by the receiving device; a recording device that records the main information and the sub information to the main recording area and the sub recording area, respectively; and a first controller that determines whether or not an amount of the main information accumulated in the accumulating device is smaller than a predetermined amount, and that controls the recording device. 
In this apparatus, the recording device records the sub information to the sub recording area under a control of the first controller if the first controller determines that the amount of the main information accumulated in the accumulating device is smaller than the predetermined amount, and the recording device records the main information to the main recording area under a control of the first controller if the first controller determines that the amount of the main information accumulated in the accumulating device is not smaller than the predetermined amount. 
When the operation of the information recording apparatus is started, the main information is input from the external source.  This main information is received by the receiving device and accumulated in the accumulating device.  At this time, the first controller determines whether or not the amount of the main information accumulated in the accumulating device is smaller than the predetermined amount.  When the input of the main information has been just started, the amount of the main information accumulated in the accumulating device is smaller than a predetermined amount, so that the recording device records the sub information to the sub recording area under the control of the first controller.  After that, the amount of the main information in the accumulating device increases and reaches the predetermined amount.  At this time, the recording device stops recording the sub information, and then starts to record the main information to the main recording area under the control of the first controller.  If the recording of the main information is started, the amount of the main information in the accumulating device decreases.  As a result, the amount of the main information in the accumulating device becomes smaller than the predetermined amount.  If the amount of the main information in the accumulating device becomes smaller than the predetermined amount, the recording device stops recording the main information, and then starts to record the sub information to the sub recording area.  Such an operation is repeatedly performed.  Thus, both the main information and the sub information are simultaneously recorded to the main recording area and the sub recording area, respectively. 
Hence, the sub information can be effectively recorded, and it is possible to shorten the entire time necessary for the recording process. 
Furthermore, in the apparatus, the receiving device receives the main information from the external source at a predetermined input rate, and the recording device records each of the main information and the sub information at a predetermined recording rate.  In this case, it is preferable that the predetermined recording rate is faster than the predetermined input rate.  Therefore, the time period corresponding to the difference between the recording rate and the input rate can be used for recording the sub information. 
The information recording apparatus may further include: an initializing device that initializes the apparatus; an instruction receiving device that receives an instruction to record the main information to the information recording medium; and a second controller that determines whether or not the instruction receiving device receives the instruction, and that controls the recording device.  In the apparatus having these additional devices, the recording device records the sub information to the sub recording area under a control of the second controller during a time period after the initializing device initializes the apparatus and before the second controller determines that the instruction receiving device receives the instruction.  According to this type of the information recording apparatus, the sub information can be recorded before the recording of the main information is actually started in response to the user""s instruction.  Therefore, the sub information can be effectively recorded, and it is possible to further shorten the entire time necessary for the recording process. 
The information recording apparatus may further include a third controller that determines whether or not a recording of the main information to be recorded is finished, and that controls the recording device.  In the apparatus having such an additional device, the recording device records the sub information to the sub recording area under a control of the third controller after the third controller determines that the recording of the main information to be recorded is finished.  According to this type of the information recording apparatus, the sub information can be recorded to the sub recording area, if an area that the sub information should be recorded remains in the sub recording area at the stage where the recording of the main information has been finished.  Therefore, the sub information can be effectively recorded. 
The above-mentioned object can be achieved by an information reproducing apparatus in accordance with the present invention.  The information reproducing apparatus is an apparatus for reproducing main information recorded on a main recording area of an information recording medium which has the main recording area and a sub recording area, and for recording sub information to the sub recording area.  The information reproducing apparatus includes: a reading/recording device that reads out the main information recorded on the main recording area, and that records the sub information to the sub recording area; an accumulating device that accumulates the main information read out from the main recording area by the reading/recording device; an output device that outputs the main information accumulated in the accumulating device; and a first controller that determines whether or not an amount of the main information accumulated in the accumulating device is smaller than a predetermined amount.  In this apparatus.  the reading/recording device reads the main information recorded in the main recording area under a control of the first controller if the first controller determines that the amount of the main information accumulated in the accumulating device is smaller than the predetermined amount, and the reading/recording device records the sub information to the sub recording area under a control of the first controller if the first controller determines that the amount of the main information accumulated in the accumulating device is not smaller than the predetermined amount. 
According to this information reproducing apparatus, the recording of the sub information and the reproduction of the main information are alternatively carried out, depending on the amount of the main information accumulated in the accumulating device.  This means that the recording of sub information and the reproduction of the main information are substantially carried out at the same time.  Hence, the sub information can be effectively recorded. 
The information reproducing apparatus may further include: an initializing device that initializes the apparatus; an instruction receiving device that receives an instruction to read out the main information from the information recording medium; and a second controller that determines whether or not the instruction receiving device receives the instruction, and that controls the reading/recording device.  In the apparatus having these additional devices, the reading/recording device records the sub information to the sub recording area under a control of the second controller during a time period after the initializing device initializes the apparatus and before the second controller determines that the instruction receiving device receives the instruction.  According to this type of the information reproducing apparatus, the sub information can be recorded before the reading (reproducing) of the main information is actually started in response to the user""s instruction.  Therefore, the sub information can be effectively recorded, and it is possible to further shorten the entire time necessary for the recording process. 
The information reproducing apparatus may further include a third controller that determines whether or not a reading of the main information to be read out is finished, and that controls the reading/recording device.  In the apparatus having this additional device, the reading/recording device records the sub information to the sub recording area under a control of the third controller after the third controller determines that the reading of the main information to be read out is finished.  According to this type of the information reproducing apparatus, the sub information can be recorded to the sub recording area, if an area that the sub information should be recorded remains in the sub recording area at the stage where the reading (reproducing) of the main information has been finished.  Therefore, the sub information can be effectively recorded. 
The nature, utility, and further feature of this invention will be more clearly apparent from the following detailed description with respect to preferred embodiments of the invention when read in conjunction with the accompanying drawings briefly described below.