Camera having magnetic head for demagnetizing and recording in demagnetization pattern

A camera arranged to use a film having a magnetic storage part comprises a magnetic head which is arranged to demagnetize a signal pattern previously recorded in the magnetic storage part of the film; and a control circuit which causes the magnetic head to demagnetize the signal pattern previously recorded in the magnetic storage part with a predetermined demagnetization pattern of a frequency lower than the frequency of the signal pattern and to form information to be recorded in the magnetic storage part of the film in the shape of the demagnetization pattern.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a camera of the kind using a film which is 
provided with a magnetic storage part and more particularly to an 
arrangement for recording information in the magnetic storage part. 
2. Description of the Related Art 
The art of magnetically recording information in a suitable part on the 
surface of film for cameras using silver-halide photographic films has 
recently been disclosed in Japanese Laid-Open Patent Application No. SHO 
60-121447 and U.S. Pat. No. 4,864,332. 
Two methods have been considered to be applicable for the camera of this 
kind in writing information in the magnetic storage part of the film. In 
one of the methods, a signal pattern carrying new information is recorded 
in the magnetic storage part of the film by means of a magnetic head after 
old information recorded in the magnetic storage part has been completely 
erased or demagnetized (or degaussed) with the magnetic head. This method 
requires two steps of operation including a demagnetizing step and a 
recording step. The other method is called an over-write method. In the 
over-write method, the signal pattern carrying new information is written 
also by means of a magnetic head in the magnetic storage part of the film 
in an overlapping manner without demagnetizing the old information 
previously recorded in the magnetic storage part. That method utilizes a 
feature of digital recording in which the recording is performed by plus 
or minus saturation in such a way as to make the intensity of recording 
magnetic field larger than that of the saturated magnetic field of a 
recording medium in use. 
In cases where the information recorded in the magnetic storage part is in 
the form of a dense (high-frequency) signal pattern, both the above-stated 
two methods necessitate use of a magnetic head which has a small gap and 
is capable of reading precipitous changes in the signal pattern when 
reading out the information recorded. However, in that instance, if the 
information recorded in the magnetic storage part is in the form of a 
coarse (low-frequency) signal pattern, the magnetic head might fail to 
read the recorded information, because changes in the signal pattern are 
moderate. 
Therefore, when a film developing facility assumes that the camera writes 
information in a dense signal pattern in the magnetic storage part of the 
film, and when the film developing facility is arranged to read the 
information written in the magnetic storage part with a magnetic head 
having a small gap which is designed for reading information written in a 
dense signal pattern from the magnetic storage part of the film, if the 
information is written by the camera in the magnetic storage part of the 
film in a coarse signal pattern, the recorded information tends to become 
hardly reproducible at the film developing facility. 
To solve this problem, the information writing magnetic head of the camera 
must be arranged to be brought into close contact with the film surface 
for forming a dense signal pattern and also to have a small, fine gap. 
Such arrangement necessitates the film to be inserted and moved between a 
pad and the magnetic head. This, however, causes an increase in sliding 
resistance in feeding the film. Also, it necessitates use of some 
mechanism for retracting the magnetic head away from the film before 
inserting the film in between the magnetic head and the pad. This not only 
increases the size of the camera but also makes the structural arrangement 
of the camera complex and results in a cost increase. 
SUMMARY OF THE INVENTION 
This invention is directed to the solution of the above-stated problems. It 
is, therefore, a principal object of the invention to provide a camera 
which is of the kind using a film having a magnetic storage part and is 
simply arranged, without increasing the size and cost thereof, to write 
and record information in the magnetic storage part of the film in such a 
way as to permit the film developing facility to reproduce the recorded 
information without fail. To attain this object, a camera which is 
arranged according to this invention to use a film having a magnetic 
storage part comprises: a magnetic head arranged to demagnetize a signal 
pattern previously recorded in the magnetic storage part of the film; and 
control means arranged to cause the magnetic head to demagnetize the 
signal pattern previously recorded in the magnetic storage part of the 
film with a demagnetization pattern of a frequency lower than the 
frequency of the recorded signal pattern and to form information to be 
newly recorded in the magnetic storage part of the film in the shape of 
the demagnetization pattern. 
The above and other objects and features of the invention will become 
apparent from the following detailed description of embodiments thereof 
taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following describes an embodiment of this invention with reference to 
the accompanying drawings. FIGS. 1(a) to 1(d) show signal patterns in the 
magnetic storage part of a film by the embodiment. FIG. 2 is an oblique 
view showing a magnetic head in relation to a portion of the film where 
the magnetic storage part is provided. FIG. 3 is a sectional view showing 
a part of a camera with the magnetic head of FIG. 2 disposed within the 
camera. 
Referring to FIG. 2, the illustration includes a film 1 and known 
perforations 2 which are formed at a given pitch along both edge parts of 
the film 1. A magnetic recording track 3 which is arranged as a magnetic 
storage part on the film 1 has a continuous high-density signal pattern 
digitally recorded beforehand in a magnetic layer, indicating information 
on ISO film sensitivity, a number of frames of the film, etc. A magnetic 
head 4 is provided with a gap which is formed in the direction of 
orthogonally intersecting the longitudinal direction of the magnetic 
recording track 3. The magnetic head 4 is arranged to be away from the 
film 1 at a distance which is about the same as the length of the gap. 
This arrangement enables the signal pattern recorded in the magnetic 
recording track 3 to be demagnetized, when a magnetic head is energized 
with a current. 
In FIG. 3, a reference numeral 5 denotes a camera body. An inner rail 5a is 
provided for restricting the position of the film 1 in the direction of an 
optical axis. An outer rail 5b is provided for restricting the position of 
the film 1 in a direction perpendicular to the optical axis. A known 
pressure plate 6 is arranged to maintain the flatness of the film 1 by 
pushing and urging it toward the camera body 5 with an elastic material 
(not shown). The above-stated magnetic head 4 is buried in the pressure 
plate 6 in a position corresponding to the magnetic recording track 3. 
Referring to FIG. 3, when a shutter which is not shown is opened, the film 
1 is exposed to light in the direction of arrow L. 
Next, the magnetic recording method of this embodiment is described as 
follows: A high-density continuous signal pattern A is previously recorded 
in the above-stated magnetic recording track 3 of the film 1, as shown in 
FIG. 1(a). The camera records, in this magnetic recording track 3, a 
signal pattern B indicating information on a date, a trimming 
magnification, an aperture value, a shutter time value, a title, etc., as 
shown in FIG. 1(b). The signal pattern B is sufficiently coarse as 
compared with the signal pattern A. The magnetic head 4 performs a 
magnetic erasing, or demagnetizing, action on the signal pattern A when 
the signal pattern B is at a high level. As a result of the erasing 
action, a signal pattern C is formed in the magnetic recording track 3 of 
the film 1, as shown in FIG. 1(c). 
If a signal pattern such as the signal pattern C shown in FIG. 1(c) is 
detected in reading the information from the magnetic recording track 3 at 
a film developing facility, an area of the signal pattern where no signal 
is detected is regarded as a low level record and the rest as a high level 
record, as shown in FIG. 1(d). 
FIG. 4 shows a rear view of the camera of this embodiment in a state of 
having its back cover removed. The illustration includes the camera body 
5, a viewfinder 7, a film rewinding fork 8; a film cartridge chamber 9; 
the outer rail 5b; an aperture 10 which is provided for exposing the film 
to light; a sprocket 11 which is interlocked with a film moving-extent 
detecting switch; a film take-up spool 12; and the magnetic head 4. 
FIG. 5 is a block diagram showing the circuit arrangement of the camera of 
FIG. 4. Referring to FIG. 5, a date circuit 25 is arranged to count the 
year, the month and the day. A light measuring circuit 26 is arranged to 
detect the luminance of an object to be photographed. A distance measuring 
circuit 27 is arranged to detect a distance to the object. A magnetic head 
driving circuit 28 is arranged to form a demagnetization (erasing) pattern 
by driving the magnetic head 4. A back cover switch 29 is arranged to 
detect the opening and closing movement of the back cover which is not 
shown. A film switch 30 is arranged to detect the presence or absence of a 
film cartridge within the film cartridge chamber 9. A release switch 31 is 
interlocked with the shutter release button of the camera. A sprocket 
switch 32 is arranged to turn on and off when the sprocket 11 rotates as 
the film moves. A trimming instruction switch 33 is provided for the 
purpose of obtaining a trimmed print of picture from the film. A motor 
control circuit 22 is arranged to control film feeding. A shutter control 
circuit 23 is arranged to control a film exposure. A lens control circuit 
24 is arranged to adjust the focus of the lens to the object. A control 
circuit 21 which is composed of a microcomputer, etc. is arranged to 
control the action of each of the above-stated circuits. 
The camera which is arranged as described above operates as described below 
with reference to FIG. 6 which is a flow chart: 
At a step #1 of FIG. 6: a check is made for the state of the back cover 
switch 29. If the back cover is found to be closed, the flow of operation 
(or program) proceeds to a step #2. If the back cover is open, the step #1 
is repeated. At the step #2: A check is made for the state of the film 
switch 30 to find if a film cartridge is placed in the film cartridge 
chamber 9. If so, the flow proceeds to a step #3. If not, the flow comes 
back to the step #1. At the step #3: An action of winding the whole film 1 
around the spool 12 beforehand which is called "prewinding" is carried out 
by the motor control circuit 22. At a step #4: A check is made for the 
state of the release switch 31 to find if the shutter release button has 
been pushed. If so, the flow proceeds to a step #5. If not, the step #4 is 
repeated. At the step #5: A distance to the object is obtained by the 
distance measuring circuit 27. At a step #6: The luminance of the object 
is obtained by the light measuring circuit 26. At a step #7: The 
photo-taking lens is driven and controlled by the lens control circuit 24 
according to the distance to the object obtained at the step #5 in such a 
way as to adjust the focus to the object. At a step #8: To expose the film 
1 to light, the shutter is controlled by the shutter control circuit 23 
according to the luminance of the object obtained at the step #6. At a 
step #9: To rewind one frame portion of film back into the film cartridge, 
a one-frame film rewinding action is caused to begin by the motor control 
circuit 22. At steps #10 to #13: The one-frame film rewinding action is 
controlled in the following manner: At the step #10, a check is made for 
the state of the trimming switch 33 to find if an instruction for trimming 
has been given. If so, the flow proceeds to the step #11. At the step #11, 
the magnetic head 4 is controlled by the magnetic head driving circuit 28 
in such a way as to demagnetize the signal pattern of the high-density 
signal previously recorded in the magnetic recording track 3 of the film 1 
with a demagnetization pattern which is sufficiently coarser than the 
high-density signal pattern. Information on trimming is recorded by means 
of this demagnetization pattern. The details of the demagnetization 
pattern will be described later on. At the step #12, date information 
including the year, month and day is obtained from the date circuit 25. At 
the step #13, the magnetic head 4 records the date information in the 
magnetic recording track 3 in the form of a demagnetization pattern in the 
same manner as at the step #11. The flow then comes to a step #14. 
At the step #14: The sprocket switch 32 is checked to find if one frame 
portion of the film has been rewound. If so, the flow proceeds to a step 
#15. At the step #15: The film rewinding action is brought to a stop. At a 
step #16: A check is made to find if all the photographable frame portions 
of the film has been used. If not, the flow comes back to the step #4. If 
all the frame portions of the film is found to have been used, the flow 
proceeds to a step #17. At the step #17: The film is rewound into the film 
cartridge for a given period of time before the film moving action is 
brought to a stop. At a step #18: The film switch 30 is checked to find if 
the film cartridge has been taken out from the film cartridge chamber 9. 
If so, the flow comes back to the step #1. 
FIG. 7 shows by way of example the demagnetization pattern recorded at the 
step #11 of FIG. 6. In FIG. 7, a reference symbol SPRO denotes the signal 
output from the sprocket switch 32 which indicates one frame portion of 
the film. More specifically, this signal consists of eight pulses as the 
number of perforation holes within one frame portion of the film is eight. 
A symbol EZ1 denotes a signal indicating a setting value of the trimming 
magnification. During the period when the signal EZ1 is at a high level, 
the magnetic head 4 is driven to demagnetize (degauss) the signal pattern 
of the high-density signal previously recorded in the magnetic recording 
track 3 of the film with a sufficiently coarse pattern in such a way as to 
perform the demagnetization corresponding to two crests of the signal 
SPRO. A symbol EZ2 denotes a signal indicating another setting value of 
trimming magnification. In the case of this signal EZ2, unlike the signal 
EZ1, the magnetization corresponding to three crests of the signal SPRO 
instead of two is performed. 
FIG. 8 shows the magnetic recording in a demagnetization pattern which is 
obtained in accordance with a self-clocking method in a case where the 
magnetic recording by the method shown in FIG. 7 is impossible when the 
amount of information is great as the trimming information and the date 
information obtained at the steps #11 and #13 of FIG. 6 are recorded. 
Referring to FIG. 8, a period of one bit is arranged to be from one rise 
to the next rise of the signal shown. Either "0" or "1" is considered to 
be recorded according to whether a fall of the signal takes place within 
the first half of the period or within the latter half of the period. In 
other words, "0" or "1" is represented according to a relation in length 
between time T1 and time T2. Information of many kinds is recordable by 
varied combinations of them. 
FIG. 9 shows the state of the demagnetization pattern obtained in the 
magnetic recording track 3 on the film 1 as a result of demagnetization 
performed in accordance with the above-stated self-clocking method. 
Referring to FIG. 9, the state of the record thus obtained is as follows: 
A demagnetized part (a portion in which a previously recorded high-density 
signal exits) which is obtained first represents the beginning of data. A 
magnetized part which comes next represents a rise in the clock signal. A 
demagnetized part obtained next represents a fall of the data. 
FIG. 10 is a diagram showing by way of example the circuit arrangement of a 
reproducing apparatus arranged at a film developing facility to read out 
from the film 1 the information recorded in the magnetic recording track 3 
by means of the magnetic head 4 of the camera. Referring to FIG. 10, a 
control circuit 47 which consists of a microcomputer, etc. is arranged to 
perform various control actions on the basis of input information of 
varied kinds. A magnetic head 48 is arranged close to the above-stated 
film 1 to read out from the magnetic recording track of the film 1 the 
information recorded in the form of a high-density signal pattern. A shaft 
49 is arranged to take up the film thereon. Changes in the signal are 
detected by the magnetic head 48 as the film 1 is wound around the film 
take-up shaft 49. A photo-interrupter 50 is arranged to detect the 
perforations 2 provided in the film 1. The result of detection thus 
obtained is used for control over a film feeding process. An amplifier 51 
is arranged to amplify a weak signal output from the magnetic head 48. A 
reference numeral 52 denotes a detection circuit. A numeral 53 denotes a 
comparator. A numeral 54 denotes a reference voltage. A numeral 55 denotes 
a flip-flop. A digital signal which is output from the comparator 53 as 
the result of comparison with the reference voltage 54 is supplied to the 
D terminal of the flip-flop 55. A numeral 56 denotes an amplifier which is 
arranged to amplify a signal output from the above-stated 
photo-interrupter 50. A numeral 57 denotes another detection circuit. A 
numeral 58 denotes another comparator. A numeral 59 denotes another 
reference voltage. A numeral 60 denotes a clock signal generating circuit. 
A digital signal which is output from the comparator 58 as the result of 
comparison with the reference voltage 59 is supplied as a clock signal 
from the clock signal generating circuit 60 to the control circuit 47 and 
the flip-flop 55 in synchronism with the information recorded in the 
magnetic recording track of the film 1. Further, in the case of this 
embodiment, the perforation 2 of the film 1 is utilized as a clock signal 
source. However, this may be changed to arrange a roller to be rotatably 
pushed against the surface of the film and to detect the rotation of the 
roller by means of a pulse disc. 
FIG. 11 is a flow chart showing the contents of the control circuit 47 
shown in FIG. 10, i.e., the reproducing operation to be performed by the 
circuit of FIG. 10 at the film developing facility. Referring to FIG. 11, 
the film is set and the reproducing process begins at a step #21. At a 
step #22: The high-density signal pattern recorded in the magnetic 
recording track 3 of the film 1 is read. Step #23: A check is made for the 
presence of a high-density signal recorded by the camera. If the 
high-density signal recorded by the camera is found, the flow of operation 
proceeds to a step #24. At the step #24: Information is read and 
reproduced with a high degree of density. At a step #25: The flow comes to 
an end. If the high-density signal recorded by the camera is not found at 
the step #23, the flow comes to a step #26. At the step #26: A continuous 
pattern of the high-density signal previously recorded on the film 1 is 
read to be regarded as a high level, while a portion having no record with 
the high-density signal demagnetized by the camera is read to be regarded 
as a low level. At a next step #27: The high and low level signals thus 
obtained are read, and the information which has been recorded in the form 
of the demagnetization pattern on the side of the camera is reproduced in 
a coarse signal pattern. The flow then comes to an end at the step #25. 
FIG. 12 is a flow chart showing the details of the process for reproducing 
the high-density signal pattern executed at the step #22 of FIG. 11. In 
this instance, the information which has been recorded in the magnetic 
recording track 3 of the film 1 in the signal pattern of the self-clocking 
method is reproduced. Referring to FIG. 12, a period of time t1 from a 
rise of each pulse of the magnetizing pattern of the high-density signal 
to the subsequent fall thereof is measured at a step #22-1. At a step 
#22-2: A period of time t2 from a fall of each pulse of the magnetizing 
pattern of the high-density signal to the subsequent rise thereof is 
measured. 
At a step #22-3: A check is made to find if the time t1 is longer than the 
time t2. If so, the flow comes to a step #22-4 to set bit information at 
"1". If the time t2 is found to be equal to or longer than the time t1, 
the flow comes to a step #22-6 to set the bit information at "0". The 
result of this gives information on the signal recorded by the 
above-stated self-clocking method. At a step #22-5: A bit pattern which is 
determined in the above-stated manner is serially read. Then, at the step 
#23 of FIG. 11, the high-density bit pattern thus read is checked to find 
if there is the information which has been recorded by the camera in the 
high-density signal pattern in the magnetic recording track 3 of the film 
1. 
FIG. 13 is a flow chart showing the details of the step #26 of FIG. 11 and 
showing, like the flow chart of FIG. 12, a reproducing method in cases 
where information is recorded in the magnetic recording track 3 of the 
film 1 in the form of the signal pattern of the self-clocking method. At a 
step #26-0 of FIG. 13: The periods of time t1 and t2 are measured in the 
same manner as in the steps #22-1 and #22-2 of FIG. 12. At a step #26-1: A 
check is made to find if the time interval of one bit, i.e., "t1+t2", is 
longer than a given length of time T, so as to determine the presence or 
absence of magnetic information of the high-density signal pattern. If 
"t1+t2" is longer than the given length of time T, the flow of operation 
proceeds to a step #26-2. At the step #26-2: This part of the signal is 
considered to be a demagnetization pattern, and the flow proceeds to a 
step #26-3 At the step # 26-3: The data t1 and t2 are received in the same 
manner as at the step #26-0. The flow comes to a step #26-4. At the step 
#26-4: The data "t1+t2" is compared with the length of time T. In this 
flow, a first demagnetization pattern, i.e., the beginning of data, shown 
in FIG. 9 is detected at the step #26-2. At the step #26-4, if the time 
"t1+t2" ceases to be longer than the time T, it indicates that the 
magnetic information of the high-density signal pattern has appeared 
again. In that case, the flow comes to a step #26-5. At the step #26-5: 
The length of time for which the high-density signal pattern continues 
begins to be counted. At a step #26-6: The data t1 and t2 are again 
received. At a step #26-7: The time "t1+t2" is checked to find if it is 
longer than the time T. If so, the flow comes to a step #26-8. At the step 
#26-8: The high-density signal pattern is considered to have come to an 
end, and the time count is brought to a stop. The flow proceeds to a step 
#26-9. At the step #26-9: A length of time for which the demagnetization 
pattern continues begins to be counted. At a step #26-10: The data t1 and 
t2 are obtained, and the flow comes to a step #26-11. At the step #26-11: 
The time "t1+t2" is checked to find if it is longer than the time T. If 
not, the flow comes to a step #26-12. At the step #26-12: The 
demagnetization pattern is considered to have come to an end, and the time 
count is brought to a stop. At a step #26-13: The duration of the 
high-density signal pattern found at the step #26-8 and that of the 
demagnetization pattern are compared with each other to find if the former 
is longer than the latter. If so, the flow comes to a step #26-14 to set 
the bit information at "1". If not, the flow comes to a step #26-15 to set 
the bit information at "0". The flow then comes to a step #26-16 to 
serially read the bit information thus obtained. 
This invention is not limited to the embodiment described in the foregoing. 
The embodiment can be variously changed. For example, information on a 
certain matter may be included in the continuous signal recorded 
beforehand in the magnetic recording track (or magnetic storage part) on 
the film. In this instance, if a reading magnetic head is provided, it 
enables the embodiment to read out the signal of previously recorded 
information before writing information. Further, a known permanent magnet 
may be used in demagnetizing or erasing information recorded on the film. 
In that instance, the permanent magnet must be moved away from the film 
surface if no demagnetizing action is required. Although the use of the 
permanent magnet necessitates the provision of a retracting mechanism, it 
permits simplification of the electrical circuit arrangement within the 
camera. 
Further, in the embodiment described, the magnetic head is arranged such 
that a line connecting the opposed parts thereof is in parallel to the 
surface of the film. However, this arrangement may be changed to perform 
magnetic recording with the film inserted in a gap between the opposed 
parts and to energize the magnetic head as the film is fed. 
In the case of the embodiment described, the invention is applied to a 
camera arranged to use a film which is provided with a magnetic storage 
part. However, the invention is of course likewise applicable to signal 
recording which differs from magnetic recording and to apparatuses other 
than cameras. 
The camera which is of the kind using a film having a magnetic storage part 
and embodies this invention as described in the foregoing is arranged to 
demagnetize a signal pattern previously recorded in the magnetic storage 
part of the film by using a predetermined demagnetization pattern which is 
of a frequency sufficiently lower than that of the signal pattern; to form 
information to be recorded in the storage part with the demagnetization 
pattern. 
The invented arrangement obviates the necessity of bringing the magnetic 
head into close contact with the film surface. This lessens the sliding 
resistance which takes place in feeding the film. Further, since the 
magnetic head is always not in contact with the film, it dispenses with a 
mechanism required for retracting the magnetic head away from the film. 
Therefore, the invented arrangement not only simplifies the structural 
arrangement of the camera but also permits reduction in size and cost 
thereof. Further, since the invention does not require a high degree of 
magnetic recording accuracy for the magnetic storage part of the film, the 
invention permits use of a magnetic head which does not have a high degree 
of accuracy and is available at a low price. Further, the use of the 
above-stated reading magnetic head in addition to the non-contact magnetic 
head permits more effective utilization of information recorded on the 
film.