JPH0572612A - Camera using film with magnetic storage part - Google Patents

Abstract

PURPOSE:To prevent the omission of a reproducing signal and to reduce the occurrence of read errors caused by external noise. CONSTITUTION:Frame number discriminating means 101 and 109 for discriminating whether or not the number of photographic frames attains a specified number, and a conversion level varying means 101 which varies a conversion level for converting an analog signal to a digital signal in an A/D conversion circuit 108b in accordance with the discrimination by the means 101 and 109 are provided, so that the conversion level for converting the analog signal reproduced by a magnetic head 4 to a digital signal is varied according to whether or not the number of photographic frames attains the specified number, that is, corresponding to the change of a film feeding speed because of changing a film winding amount to a film take-up spool.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head for reproducing information written in a magnetic storage unit provided in a film during film feeding, and for amplifying an analog signal reproduced by the magnetic head. An amplifier circuit, an A / D converter circuit for converting an analog signal from the amplifier circuit into a digital signal,
The present invention relates to an improvement of a camera using a film with a magnetic storage unit, which is provided with a film feeding means for feeding a film.

[0002]

2. Description of the Related Art In recent years, a film having a magnetic storage unit is used, and photographing information such as shutter speed, aperture value, date, title, etc. is written in the magnetic storage unit by a magnetic head.
A camera that reads out the photographing information as needed is proposed in US Pat. No. 4,864,332 and the like.

By the way, a film winding spur of a camera
As the film is wound around the film, the winding diameter of the film winding spool gradually increases, and the film feeding speed increases. That is, the film feeding speed is different between the first frame and the last frame.

[0004]

When information is read by the magnetic head during film feeding, the magnitude of the signal level detected by the magnetic head is proportional to the film feeding speed. In other words, the film feeding speed of the first frame is relatively slow,
The level of the signal detected by the magnetic head is low, and the film feeding speed increases toward the final frame, so the signal level detected by the magnetic head increases.

The digital conversion level of an A / D (analog-digital) converter arranged in the magnetic reproducing circuit is
Magnetic head 4 as much as possible so as not to be affected by external noise
It is desirable to set the level higher than the level in the non-driving state, that is, in the steady state. However, if it is set to such a high and constant level, the film feeding speed is slow in the first frame as described above. The signal level reproduced during the state is low, so that a signal which does not reach the digital conversion level is generated, which may result in an information reading error.

Further, if the digital conversion level is set lower and constant than the level in the steady state, it is easily affected by external noise regardless of the film feeding speed, and the noise is digitally converted. There is a possibility that the reproduction signal is different from the signal (write signal).

SUMMARY OF THE INVENTION In view of the above points, an object of the present invention is to provide a camera using a film with a magnetic memory unit, which can prevent the omission of a reproduction signal and reduce the occurrence of reading errors due to external noise.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a frame number discriminating means for discriminating whether or not the number of photographed frames of a film has reached a predetermined frame number, and an A / D according to the discrimination of the frame number discriminating means And a conversion level changing means for changing a conversion level for converting an analog signal into a digital signal in the conversion circuit.

[0009]

The conversion level changing means changes the film feeding speed depending on whether or not the number of filmed frames has reached a predetermined number, that is, the amount of film wound around the film winding spool. Corresponding to the change of, the conversion level for converting the analog signal reproduced by the magnetic head into a digital signal is changed.

[0010]

1 to 4 are views showing a mechanical structure in a first embodiment of the present invention, and FIG. 1 is a perspective view showing a main part of a camera.

In FIG. 1, 1 is a film cartridge, 2 is a film provided with a magnetic memory (magnetic track) T, and 3 is a perforation (P1, P2) of the film 2.
And the like), and the photosensor 4 for feeding the film at a fixed length is in sliding contact with the magnetic track T of the film 2,
A magnetic head 5 for writing or reading information is located at a position facing the magnetic head 4 with the film 2 interposed therebetween.
The pad has a function of pressing the film 2 against the magnetic head 4.

Reference numeral G denotes a film feeding mechanism for transmitting the output of the film feeding motor 1 to the fork 70, the details of which will be described later with reference to FIG. 57 is a film winding spool.

The film cartridge 1 used in this embodiment has the following structure proposed in US Pat. No. 4,834,306.

That is, the film passing slit and the film 2 having one end fixed to the supply spool and wound around the supply spool, and the film 2 which is arranged coaxially with the supply spool and spreads in the radial direction of the outermost periphery of the film. Film 2 regulated by the regulatory department
The pressing member (not shown) that prevents the outermost periphery of the film from substantially contacting the inner wall of the film cartridge, and a part of the pressing member are deformed so that the outermost peripheral portion of the film is prevented from being restricted in the radial direction of the pressing member. The fork 70 is provided with a releasing portion (not shown) for continuously releasing and a guiding portion (not shown) for guiding the portion of the film 2 released from the regulation to the film passage slit.
The supply of a supply spool (not shown) engaged in the direction of extruding the film 2 prevents the slippage between the outer periphery of the film 2 and the pressing member due to the expansion of the outermost circumference due to the loosening of the film 2 caused by the rotation of the film 2. The driving force is applied to enable the film 2 to be extruded from the film cartridge 1.

The film 2 is extruded from the inside of the film cartridge 1 by a film feeding mechanism which will be described later, and then the film winding spool 57 of the camera is formed by a known means.
It is wound up and sent.

2 to 4 are views showing a concrete example of the structure of the film feeding mechanism G. As shown in FIG.

In these figures, reference numeral 51 denotes a film feeding motor, which rotates normally when the film is wound (in the direction of arrow B in FIG. 3) and reversely when the film is rewound (in the direction of arrow C in FIG. 4). Reference numeral 52 is a pinion gear fixed to the rotation shaft of the motor 51. Reference numeral 53 denotes a first sun gear, which meshes with the pinion gear 52. 54 is a first planetary gear that meshes with the first sun gear 53. 55
Connects the first sun gear 53 and the first planetary gear 54, and rotatably holds the first planetary gear 54 while generating frictional force between the first sun gear 53 and the first planetary gear 54. It is a first connecting lever that revolves around the first planetary gear 54 about the first sun gear 53 as the center of rotation when the first sun gear 53 rotates. The first sun gear 53, the first planetary gear 54, and the first connecting lever 5
5 constitutes a known planetary gear mechanism. Reference numeral 56 is a spool gear which meshes with the first planetary gear 4 only when the film feeding motor 51 is rotated in the normal direction. Reference numeral 57 is a film winding spool that is fixed to the spool gear 56 and moves integrally.

Reference numeral 58 denotes a first idler gear that is constantly meshed with the first sun gear 53, 59 is a large gear portion 59a and a small gear portion 59b, and the large gear portion 59a is a first idler gear 58 that is meshed with the first idler gear 58. Two-stage gear, 60 is the first
A second idler gear that meshes with the small gear portion 59b of the two-stage gear 59, 61 is a third idler gear that meshes with the second idler gear 60, 62 is a second sun gear that meshes with the third idler gear 61, and 63 is It is a second planetary gear that meshes with the second sun gear 62. 64 is the third
This planetary gear is engaged with the second sun gear, like the second planetary gear 13. Reference numeral 65 connects the second sun gear 62, the second planetary gear 63 and the third planetary gear 64 with arm portions 65a and 65b, respectively, and holds each planetary gear rotatably while generating frictional force. The second planetary gear 63 and the third planetary gear 64 revolve around the second sun gear 62 as a rotation center by the rotation of the second sun gear 62. .. The second sun gear 62 and the second and third planetary gears 63, 64
A known planetary gear mechanism is configured by the second connecting lever 65 and the second connecting lever 65.

Reference numeral 66 is a fourth idler gear, which is the second of the second connecting lever 65 when the film feeding motor 51 is rotated in the forward direction.
When the motor 51 rotates in the reverse direction, it engages with the second planetary gear 63 and does not engage with the third planetary gear 64 by rotating the sun gear 62 in the left direction about the right side of the second connecting lever 65. This is a gear that meshes with the third planetary gear 63 and does not mesh with the second planetary gear 63 by rotating in the direction. 67 has a large gear portion 67a and a small gear portion 67b, the large gear portion 67a has a second two-stage gear that meshes with the fourth idler 66, and 68 has a large gear portion 68a and a small gear portion 68b. Part 6
Reference numeral 8a denotes a third two-stage gear that meshes with the small gear portion 67b of the second two-stage gear 67, 69 denotes a fork gear that meshes with the small gear portion 68b of the third two-stage gear 68, and 70 denotes the fork. A fork which rotates integrally with the gear 66, thereby rotating a supply spool (not shown) in the film cartridge 1 to extrude and wind the film 2 from the inside of the cartridge 1. ..

Reference numeral 71 denotes a stopper provided on a camera body (not shown) for regulating the position of the first connecting lever 55 in the leftward rotation direction.

In the above structure, after the film cartridge 1 is loaded in the cartridge chamber (not shown), the film feeding motor 51 (pinion gear 52) is shown in FIG.
Is rotated in the direction of arrow B (normally rotated), the first sun gear 53 is rotated clockwise, and the action of the first connecting lever 55 causes the first planetary gear 54 to rotate. Revolves clockwise around the first sun gear 53 as a center of rotation, and then meshes with the spool gear 56, the driving force of the film feeding motor 51 is transmitted to the spool gear 6, and the film take-up spool. -Le 57 will rotate clockwise.

Further, the driving force is supplied to the first two-stage gear 59, the second idler gear 60, through the idler gear 58 which is another gear meshing with the first sun gear 53.
It is transmitted to the second sun gear 62 via the third idler gear 61. Therefore, since the second sun gear rotates counterclockwise, the action of the second connecting lever 65 causes the second planet gear 63 and the third planet gear 64 to rotate about the second sun gear. It revolves counterclockwise and eventually the second planetary gear 63 comes into mesh with the fourth idler gear 66. As a result, the driving force in the B direction of the film feeding motor 51 is transmitted to the fourth idler gear 66 as a counterclockwise driving force, and further, the second two-stage gear 67 and the third two-stage gear 68. Is transmitted to the fork gear 69 via
The forks 70 rotate clockwise.

Here, the gear ratio of the gear train is constructed as follows.

The peripheral speed of the film winding spool 57 is "V1", and the fork 70 is used for film cartridge 1
When the speed of the film 2 extruded from the film is “V2”,
There is a relationship of “V1> V2”.

When the film 2 is extruded from the film cartridge 1 by the clockwise rotation of the fork 70, the leading end of the film is moved by a known means (a nail provided on the film winding spool 57). The perforation P of the film 2 is hooked, or the film 2 is pressed against the film take-up spool 57 provided on the camera body side. It is wound around the winding spool 57.
After that, the film 27 is wound only by the rotation of the film winding spool 57 by the film feeding motor 51, for the reason described below.

Due to the relationship of "V1>V2", when the film 2 is wound around the film winding spool 57, the film winding spool 57 interposes the film 2 on the fork gear 69 and the third gear. The second planetary gear 6 is transmitted in the order of the step gear 68, the second two-step gear 67, and the fourth idler gear 66.
4th idler gear 66 than the clockwise rotation speed of 3
The counterclockwise rotation speed of is faster, but at this time, the fourth idler gear 66 bounces off the second planetary gear 63,
This is because the second planetary gear 63 and the fourth idler gear 66 are disengaged from each other for a moment, and the difference in speed is absorbed.

Next, the operation of rewinding the film will be described.

This operation will be described with reference to FIG. 4. When the film feeding motor 51 is rotated in the direction of arrow C, the first connecting lever 55 and the first planetary gear 54 become the first sun gear 5.
It revolves counterclockwise around the rotation center 3 until the end portion 55a of the first connecting lever 55 contacts the stopper 71. Therefore, the first planetary gear 54 and the spool gear 56
The engagement with is released.

At this time, the second sun gear 62 rotates in the clockwise direction, so that the second planetary gear 63 and the third planetary gear 64 are actuated by the second connecting lever 65. The gear 62 revolves clockwise around the rotation center,
The idler gear 66 and the second planetary gear 63 are disengaged from each other, and instead, the fourth idler gear 66 and the third planetary gear 64 are engaged with each other. Therefore, the fork gear 69 rotates counterclockwise, and the fork 70 rotates the supply spool (not shown) in the film cartridge 1 in the reverse direction so that the film 2 is wound into the cartridge 1. Go

FIG. 5 is a circuit block diagram of a camera according to the first embodiment of the present invention.

In FIG. 5, reference numeral 101 is a control circuit configured by a microcomputer or the like for controlling various operations of the camera, 102 is an AF / AE control circuit for controlling the focusing of the photographing lens and the operation of the exposure control shutter, 103 is a film feeding motor for driving the film feeding motor 51.
A driver circuit, 104 is a magnetic head drive circuit for driving the magnetic head 4 to perform an information writing operation, 105
Is a release switch. When this switch is turned on, the camera is released. Reference numeral 106 is a cartridge loading switch which is turned on when the film cartridge 1 is loaded in the camera, and 107 is a back lid switch which is turned on when the back lid is closed. Both of these switches 106 and 107 are turned on. Thereby, the control circuit 101 drives the film feeding motor driver circuit 103 to start the cueing of the first frame of the film 2.

A magnetic reproducing circuit 108 detects the magnetic information written on the magnetic track T of the film 2 via the magnetic head 4, amplifies it as an analog signal and then digitally converts it into information for the control circuit 101. And
A signal amplifier 108a that detects the output from the magnetic head 4 and amplifies the analog signal thereof, and an A / D converter 108 that converts the analog signal amplified here into a digital signal.
b.

Reference numeral 109 is a counting circuit for counting the number of releases of the camera, 110 is a frame number display for displaying the number of frames to be photographed, which is composed of a liquid crystal display, and 111 is the frame number display 1
It is a display driver circuit for driving 10 to count up or count down.

FIG. 6 is a circuit diagram showing a concrete configuration example of the A / D converter 108b shown in FIG.

In the figure, reference numerals 31 and 32 are comparators for digitizing the positive and negative signals (assuming the level in the steady state is "0") of the analog signals amplified by the signal amplifier 108a. , 33 are RS flip-flops for converting the positive and negative signals digitized by the comparators 31, 32 into digital signals, and 34 to 37 are analog switches for switching the signal inversion levels of the comparators 31, 32. , 38 to 43 are resistors for setting the signal inversion levels of the comparators 31 and 32, and these resistance values are set to R38, R39, R40, R.
41, R42 and R43.

The analog switches 34 to 37 operate as follows. That is, the switching signal AS from the control circuit 101
When 1 is input, the analog switches 34 and 35 are turned on, and when the switching signal AS2 is input, the analog switches 36 and 37 are turned on.

Here, the voltage applied to the terminals a and b is Va,
Assuming Vb, the signal inversion levels Vref31 and Vref32 are Vref31 = (R39 + R40) / (R38 + R39 + R40) × Va Vref32 = R43 / (R41 + R42 + R43) × Vb when the analog switches 36 and 37 are in the ON state, and the analog switches 34 and 37 are When 35 is in the ON state, the signal inversion levels Vref31 and Vref32 are Vref31 = R40 / (R38 + R39 + R40) * Va Vref32 = (R42 + R43) / (R41 + R42 + R43) * Vb.

By the way, the film feeding speed of the camera is such that when the rotation speed of the film winding spool 57 is the same, the amount of film 2 wound around the film winding spool 57,
That is, as described above, it is proportional to the winding diameter, and the level of the analog signal detected by the magnetic head 4 is proportional to the film feeding speed. Therefore, the level of the analog signal detected by the magnetic head 4 is proportional to the winding diameter of the film winding spool 57 of the film 2.

The diameter of the film winding spool 57 is D, the thickness of the film 2 is d, the pitch of one frame is L, and the aperture when the leading end portion of the film is wound around the film winding spool 57 once. When the char position is the first frame, the film 2 when n frames are wound around the film winding spool 57
The total length Fn of the film is Rn = (n-1) L + Dπ, and the total film length Fm up to the mth round is = {(D-2d) m + dm (m + 1)} π, and how many turns the nth frame is Can be represented by Therefore, the inner winding diameter D of the nth frame
n can be represented by Dn = D + f (m) × 2 × d (where f (m) is a function that rounds down the fractional part of m). Therefore, as an example of this, D = 10 m
Substituting the general numerical values of m, d = 0.14 mm, L = 38 mm, the inner winding diameter of the first frame D1 → "10.28 mm", the inner winding diameter of the 36th frame D36 → "30.60 mm" ..

Therefore, the level of the analog signal is the first
A difference of about 3 times is made between the frame No. 36 and the frame No. 36, and in the conventional case, as described above, the A / D converter 108 in the magnetic reproducing circuit 108 is protected from the influence of external noise.
If the digital conversion level of b is set to a constant value such that the difference from the level in the steady state is as large as possible, a reproduction signal that does not reach the digital conversion level occurs when the film feeding speed is slow, and There is a problem in that reading errors occur, and conversely, if the digital conversion level is set to a constant value that reduces the difference from the steady state level, external noise will occur regardless of the film feeding speed. However, there is a problem in that even noise is digitally converted.

Therefore, in this embodiment, the difference between the digital conversion level and the level in the steady state (when the reproduction signal is not output from the magnetic head 4) is small when the number of frames of the film 2 is small. In addition, when the number of frames to be photographed on the film 2 is large, the difference from the level in the steady state is set to be large.

FIGS. 7 and 8 show output waveforms of the respective portions when the film feeding speed is the first frame and when the film feeding speed is the 36th frame.

More specifically, FIGS. 7 (a) and 8 (a) show detection (reproduction) signals of the magnetic head 4 at the first frame and the 36th frame, respectively. b) is the output signal of the signal amplifier 108a for amplifying its input, and FIGS. 7 (c) and 8 (c) are A / D converters 10 for A / D converting its input.
The output signals of 8b are shown respectively.

Digital conversion level V in FIG. 7 (b)
ref31-a and Vref32-a are Vref31-a = R40 / (R38 + R39 + R40) * Va Vref32-a = (R42 + R43) / (R41 + R42 + R43) * Vb. In this case, analog switches 34 and 35 are ON
It is in a state.

Vref31-b and Vref32-b in FIG. 8 (b)
Is Vref31-b = (R39 + R40) / (R38 + R39 + R40) × Va Vref32-b = R43 / (R41 + R42 + R43) × Vb. In this case, the analog switches 36 and 37 are ON
It is in a state.

FIG. 9 shows the output waveforms of the first frame and the 36th frame, for example, at the intermediate 18th frame. More specifically, FIG. 9A shows the output waveform of the 18th frame. Magnetic head 4
9 (b) shows the output signal of the signal amplifier 108a which amplifies its input, and FIG. 9 (c) shows its input as an A / D.
The output signals of the A / D converter 108b for conversion are shown respectively.

The upper limit peak of the output signal shown in FIG.
Of the digital conversion level V
It is a limit state in which it is larger than ref31-b and smaller than Vref32-b.

Therefore, in this embodiment, the digital conversion levels from the first frame to the seventeenth frame are Vref31-a and Vref31-a.
ref32-a, Vref31-b, Vref32-b after the 18th frame
I am trying to.

Next, the operation of the control circuit 101 will be described with reference to the flowchart of FIG.

When the power switch of the camera is turned on, the operation from step 100 is started. "Step 100" Cartridge loading switch 106
And the back cover switch 107 are both turned on, and if both are turned on, it is determined that the film cartridge 1 is loaded in the camera, and the process proceeds to step 101. "Step 101" The switching signal AS1 is output to turn on the analog switches 34 and 35, and the digital conversion levels are set to Vref31-a and Vref32-a as shown in FIG. 7 (b). [Step 102] An operation of driving the film feeding motor driver circuit 103 to locate the first frame of the film 2 at the aperture position by the film feeding motor 51.
That is, the film idling operation is started. [Step 103] During the idling operation of the film 2, the magnetic head 4 is driven through the magnetic head drive circuit 104, and the film sensitivity and the number of film frames pre-written on the magnetic track T provided in the film 2 are recorded. Read and store film information such as film type (negative or positive). "Step 104" Here, it is known that the first cueing is completed (for example, by detecting the film feed amount by an encoder, motor energization time, detection of perforation P, etc.). When it is determined that the detection has been performed by, the process proceeds to step 105. "Step 105" The film feeding motor 51 is stopped through the film feeding motor driver circuit 103,
Stop film winding. "Step 106" The frame number display unit 111 is driven through the frame number display driver circuit 110 to display that it is the first frame. [Step 107] The state of the release switch 105 is discriminated, and if it is ON, it is determined that release has been performed and the process proceeds to step 107. "Step 108" The counting circuit 109 is caused to count the number of releases for the film 2 currently in use. [Step 109] The AF / AE control circuit 102 is driven to perform a shooting operation such as an exposure operation by focusing the shooting lens and opening / closing a shutter. "Step 110" The number of film frames read out in step 103 or the number of film frames preset by a known means is compared with the number of frames currently taken to determine whether or not there are remaining film frames. To do. As a result, if there are remaining frames, the process proceeds to step 111, and if there are no remaining frames, the process proceeds to step 118. "Step 111" Whether or not the number of photographed frames has reached the 18th frame is determined based on the count content (the number of releases) of the counting circuit 109 counted in step 108. The digital conversion level is not changed and the process proceeds to step 113. If it is the 18th frame or later, the process proceeds to step 112. "Step 112" The switching signal AS2 is output to turn on the analog switches 36 and 37, and the digital conversion level is Vref31-b, as shown in FIGS. 8 (b) and 9 (b).
Set to Vref32-b. "Step 113" The film feeding motor 51 is driven through the film feeding motor driver circuit 103 to start winding one frame of the next frame. [Step 114] During the winding of the next frame of the film 2, the magnetic head 4 is driven through the magnetic head drive circuit 104, and the photographing information such as the shutter speed and the aperture value is transferred to the magnetic track T corresponding to the photographing frame of the film 2. , Write information such as the date of shooting, or magnetic reproduction circuit 10
The information written on the film 2 is read by driving the magnetic head 4. [Step 115] It is determined whether or not the winding of the next frame of the film 2 is completed. If completed, the process proceeds to step 116. If not completed, the process returns to step 113. "Step 116" The driving of the film feeding motor 51 is stopped through the film feeding motor driver circuit 103 to stop the winding of the film 2, and the process proceeds to step 117. "Step 117" The frame number display driver circuit 110 is instructed to count up the frame number. Then step 1
Return to 06.

If it is determined in step 110 that there are no remaining frames on the film 2, the process proceeds to step 118 as described above. [Step 118] The film feeding motor 51 is driven in the film rewinding direction through the film feeding motor driver circuit 103 to start the rewinding of the film 2 to the film cartridge 1. [Step 119] It is determined whether or not the rewinding of the film 2 into the film cartridge 1 is completed, and if completed, the process proceeds to step 120. If not completed, the process returns to step 118. "Step 120" A series of operations of the camera is ended.

FIG. 11 shows A / in the magnetic reproducing circuit 108.
It is a second embodiment of the present invention showing another configuration example of the D converter 108b, and is different from the first embodiment in that it is configured to perform A / D conversion by one comparator 81. ..

In FIG. 11, reference numeral 81 is an open collector comparator for digitizing the analog signal detected by the signal amplifier 108a for amplifying the analog signal.
Reference numerals 2 and 83 change the output state according to the control signal input from the control circuit 101 and the output of the comparator 81 according to the number of photographed frames, and the comparison voltage (digital conversion level Vref8
(1) has an open collector NAND gate for providing a hysteresis width, and 84 is an inverter for controlling the NAND gate 83 and the PNP transistor 85 via the resistor 91 having a resistance value R91, 85 is ON / O
A PNP transistor for controlling whether to pull up the resistor 90 having a resistance value R91 by FF, 8
6 to 90 are digital conversion levels V of the comparator 81.
These are the resistors that determine ref81.
6, R87, R88, R89. The resistance 88,
It is assumed that the relationship of 89 is “R88 <R89”.

The operation of the A / D converter 108b having the above structure will be described below.

The control circuit 101 sends a control signal of "H" to the 17th frame or later depending on the number of frames to be photographed at that time.
If it is up to the frame, a control signal of "L" is sent to the NAND gate 82.
And to the inverter 84.

If it is assumed that the eighteenth frame or later, the control circuit 101 inputs a control signal of "H" to the A / D converter 108b.
Output becomes "L" and the PNP transistor 85 turns on.
As a result, the resistor 90 is in a state similar to that in which the resistor 90 is connected in parallel with the resistor 86.

The NAND gate 83 is an inverter 84.
Since the "L" signal is input from the device, the NAND gate 82 is always in the open state, the output state of the NAND gate 82 is determined by the output of the comparator 81, and the analog signal is not input to the comparator 81, or When the output of the comparator 81 is "L", the output is in the open state and the resistor 88 is ignored. Therefore, the comparison voltage of the comparator 81 at that time, that is, the digital conversion level Vref81-H (V
(corresponding to ref31-b) is Vref81-H = Vcc x R87 / {(R86 x R90) / (R86 + R90) + R87}.

When an analog signal exceeding the digital conversion level Vref81-H is input to the comparator 81,
The output of the NAND gate 82 becomes "L", the resistor 88 is connected in parallel with the resistor 87, and the digital conversion level Vref81-L (corresponding to Vref32-b) of the comparator 81.
Is Vref81-L = Vcc × {(R87 × R88) / (R87 + R88)} / [{(R86 × R90) / (R86 + R90)} + {(R87 × R88) / (R87 + R88)}].

In the case of up to the 17th frame,
Since the output of the comparator 84 is in the open state and the PNP transistor 85 is in the OFF state, the resistor 90 has no influence on the digital conversion level Vref81 and the comparator 8
Digital conversion level Vref8 when the output of 1 is "L"
1-H (corresponding to Vref31-a) becomes Vref81-H = Vcc × R87 / (R86 + R87). Also, the digital conversion level Vref81-L (corresponding to Vref32-a) when the output of the comparator 81 is "H".
Is Vref81-L = Vcc × {(R87 × R89) / (R87 + R89)} / [R86 + {R87 × R89) / (R87 + R89)}].

12 (a) (b) and 13 (a) (b),
From the first frame to the seventeenth frame described above in the second embodiment.
A / D converter 1 up to frame 18 and after frame 18
It is a figure which shows the output waveform of each part of 08b.

FIG. 13 is a plan view of a camera showing the structure of the essential parts of the third embodiment of the present invention. In this embodiment,
Rather than counting the number of frames taken on the film 2, it is detected whether or not the winding diameter of the film 2 wound around the film winding spool 57 of the camera reaches a predetermined size, and the first or the first or second film diameter is detected. Is to change the digital conversion level by the method of the second embodiment.

In FIG. 14, 72 is a cartridge chamber provided in the camera body (not shown), 73 is a spool chamber, and 7 is a spool chamber.
Reference numeral 4 is a film pressure plate, and 75 is a rotatably attached to the camera body. The film 2 is pressed against the film winding spool 57 by a portion 75a so that the auto-rolling can be properly performed. Reference numerals 76 and 76 are springs, one end of which is attached to the camera body and the other end of which is attached to the body roller lever 75, and which applies a rightward biasing force to the body roller lever 75.

Reference numeral 77 is a winding diameter detection switch, and the contact piece 77a can be brought into contact with the 75b portion of the main body roller lever 75, and is deformed by being brought into contact with the main body roller lever 75 by being rotated counterclockwise. It is configured to contact (ON) with.

The winding diameter detection switch 77 is connected to the above-mentioned control circuit 101. The control circuit 101 in this embodiment has a structure that when the switch 77 is OFF, for example, in FIG. 6 in the first embodiment. Analog switch A
When S1 is turned on, when it is turned on, the analog switch AS2 is controlled to be turned on.

That is, when the film 2 is wound around the film winding spool 57 and the 18th frame is wound around the film winding spool 57, the body roller lever 75 of the main body roller lever 75 moves. It rotates counterclockwise against the urging force to turn ON the contact pieces 77a, 77b at the portion 75b. This O
When N is detected, the control circuit 101 interlocks with the digital conversion levels from Vref31-a and Vref32-a to Vref31-b.
Change to Vref32-b.

According to each of the above embodiments, the digital conversion level of the A / D converter 108b in the magnetic reproducing circuit 108 is changed according to the number of frames of the film 2 photographed. When converting the read playback analog signal to a digital signal, there is less chance that the playback signal will be lost or that external noise will be converted as data and erroneous information will be output. It becomes possible to do.

[0067]

As described above, according to the present invention,
A frame number discriminating means for discriminating whether or not the number of photographed frames of the film has reached a predetermined frame number, and A /
A conversion level varying means for varying a conversion level for converting an analog signal into a digital signal in the D conversion circuit is provided, and the film winding is performed depending on whether or not the number of filmed frames has reached a predetermined number. The conversion level for converting the analog signal reproduced by the magnetic head into a digital signal is changed in response to a change in the film winding speed on the take-up spool and a change in the film feeding speed. I have to. Therefore, it is possible to prevent the reproduction signal from being omitted and to reduce the occurrence of reading errors due to external noise.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main configuration of a camera according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a gear train of the film feeding mechanism of FIG.

FIG. 3 is a plan view showing an arrangement of gears at the time of film winding of the film feeding mechanism of FIG.

FIG. 4 is a plan view showing an arrangement of gears at the time of film rewinding of the film feeding mechanism of FIG.

FIG. 5 is a circuit block diagram of the camera of the first embodiment of the present invention.

6 is a circuit diagram showing a specific configuration of the A / D converter shown in FIG.

FIG. 7 is a diagram showing a signal waveform of each part when the first frame is wound around the film winding spool in the first embodiment of the present invention.

FIG. 8 is a diagram showing a signal waveform of each part when the final frame is wound around the film winding spool in the first embodiment of the present invention.

FIG. 9 is a diagram showing a signal waveform of each part when the intermediate photographing frame is wound around the film winding spool in the first embodiment of the present invention.

10 is a flowchart showing the operation of the control circuit of FIG.

FIG. 11 is a circuit diagram showing a specific configuration of an A / D converter according to a second embodiment of the present invention.

FIG. 12 is a diagram showing signal waveforms of respective portions when the first to seventeenth frames are wound around the film winding spool in the second embodiment of the present invention.

FIG. 13 is a diagram showing a signal waveform of each part when the 18th and subsequent frames are wound around the film winding spool in the first embodiment of the present invention.

FIG. 14 is a plan view of a camera showing a main part configuration in a third embodiment of the present invention.

[Explanation of sign]

 4 magnetic head 51 film feeding motor 77 roll diameter detection switch 101 control circuit 103 film feeding motor driver circuit 104 magnetic head drive circuit 108 magnetic reproduction circuit 108a signal amplifier 108b A / D converter 109 counting circuit

Claims (1)

[Claims] 1. A magnetic head for reproducing information written in a magnetic storage unit provided in a film during film feeding, an amplifier circuit for amplifying an analog signal reproduced by the magnetic head, and In a camera using a film with a magnetic storage unit, which has an A / D conversion circuit for converting an analog signal from an amplifier circuit into a digital signal and a film feeding means for feeding the film, the number of film frames is predetermined. A frame number discriminating means for discriminating whether or not the number of frames has been reached, and in the A / D conversion circuit according to the discrimination by the frame number discriminating means,
A camera using a film with a magnetic storage section, which is provided with a conversion level changing means for changing a conversion level for converting an analog signal into a digital signal.