JPS5923511B2 - Imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an imaging device using an image pickup tube, and more particularly to a video camera particularly suitable for a facsimile system.

Two-dimensional information such as documents and photos can be captured using a video camera.
A facsimile system can be considered that converts the image into a dimensional still image signal, transmits the still image signal wirelessly or wired to another location, and forms a copy of a document, photograph, etc. on recording paper or the like on the image receiving side.

By the way, the shapes of documents, photographs, etc. are not necessarily constant, and may vary, such as squares or rectangles. Even if the shape changes in this way, it is possible to photograph the entire object with a television camera having a raster aspect ratio of 3:4. However, unnecessary parts unrelated to the subject are created, and if an image is considered as a collection of pixels, the number of pixels that convey subject information is limited, and image quality inevitably deteriorates. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an imaging device that transmits a video signal that can obtain a finely reproduced image even if the shape of a subject changes.

To achieve the above object, the present invention has a horizontal deflection means, a vertical deflection means, and a lens for enlarging and reducing an image corresponding to an object. a horizontally polarized sawtooth generator for supplying a polarized sawtooth wave; a vertically polarized sawtooth generator for supplying a vertically polarized sawtooth wave to said vertical deflection means; and maintaining a constant slope of said horizontally polarized sawtooth wave. a horizontal scanning period changing circuit that changes the horizontal scanning period while keeping the horizontal scanning period constant; and a horizontal scanning period changing circuit configured to change the slope of the vertical deflection sawtooth wave while keeping the vertical scanning period constant, The horizontal scanning period in the horizontal scanning period changing circuit is formed so that it changes in inverse proportion to the horizontal scanning period so that it becomes smaller when the period is increased, and the scanning area is kept approximately constant. The present invention relates to an imaging device comprising a vertical polarization sawtooth wave slope changing circuit formed so that the slope of the vertical polarization sawtooth wave changes in conjunction with a change in the scanning period.

The above invention provides the following effects.

(b) When the subject is small, the large nozzle can be used to enlarge the image and increase the resolution. In this case, in the present invention, the horizontal polarization sawtooth wave and the vertical polarization sawtooth wave are changed so that the scanning area is kept constant, so it is possible to keep the imaging time (scanning time) of the subject constant. . Therefore, processing and transmission of the imaging output obtained from the imaging tube is facilitated. (b) Since the horizontal scanning period changing circuit and the vertical deflection sawtooth wave slope changing circuit are configured to work together, imaging of a constant scanning area can be easily achieved.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, which schematically shows the whole of a still image signal forming device for facsimile according to an embodiment of the present invention, a lens 3 is arranged on the front surface of a television image pickup tube 1 via a mechanical shutter 2. .

The mechanical shutter 2 is opened only at the moment when the subject to be transmitted or recorded is captured on the image pickup tube 1 as a still image. Of course, like a general television camera, the shutter 2 is kept open when obtaining moving information. The image pickup tube 1 must have the ability to hold the still image accumulated on the photoconductive film 4 for several tens of seconds, that is, it must be a T-type image pickup tube with a low dark current. Image pickup tubes 1 that satisfy this condition include PbO tubes (Plumbicon) and CdSe tubes (Calnicon), which are currently used in TV cameras at broadcasting stations. A VT terminal 7 to which a voltage VT is applied is connected to the transparent electrode 5 of the image pickup tube 1 via a resistor 6. A video amplifier circuit 9 is also connected via a capacitor 8. The video amplifier circuit 9 has the same configuration as a video amplifier of a general television camera,
A standard video signal obtained when this imaging device is used in the same way as a general television camera is sent to an output terminal 10 connected here. A signal processing circuit 11 is also connected to this video amplifier circuit 9, and the signal obtained when this device is used in narrowband operation is processed by this signal processing circuit 11 to become a first narrowband video signal. . The details of the signal processing circuit will be described after referring to FIG. A variable speed magnetic recording and reproducing device 12 is connected to the output terminal of the signal processing circuit 11, and a first narrowband video signal obtained from the signal processing circuit 11 is recorded in the magnetic recording and reproducing device 12. The details of the configuration of the magnetic recording/reproducing device 12 will be described later with reference to FIGS. 3 to 5, so only an outline will be given here. It is composed of That is, the signal reading speed is configured to be lower than the signal writing speed. Therefore, from the output terminal 13, a second narrowband video signal whose frequency band is even narrower than the first narrowband video signal input to the magnetic recording/reproducing device 12 is obtained. This secondary narrowband video signal has a frequency band that can be transmitted using a general telephone line. Image pickup tube 1 in Figure 1
is designed to be able to perform both standard beam scanning and slow beam scanning.

Switches 16 and 17 connected to the horizontal deflection coil 14 and the vertical deflection coil 15 respectively are for switching between the above-mentioned standard beam scanning and slow beam scanning.
When it is applied to contact a, the beam scans at a low speed, and contact b
If the beam is cast at , standard beam scanning will occur. Therefore, the contact b of the changeover switch 16 is connected to a drive circuit 19 in which the output of the standard horizontal synchronizing signal generation circuit 18 is connected to its human power, similar to a general television camera, and the contact b of the changeover switch 17 is A drive circuit 21 is connected to which the output of the standard vertical synchronization signal generation circuit 20 is coupled to its human power. On the other hand, a low-speed horizontal drive circuit 22 is connected to a contact a of the switch 16, and a low-speed vertical drive circuit 23 is connected to a contact b of the switch 17. Reference numeral 24 denotes a clock pulse generator which generates clock pulses of a frequency equal to the frequency at which the beam is switched during low-speed beam scanning.

Since the beam switching in the image pickup tube 1 is performed to divide one horizontal scanning period into several hundred parts, the output frequency of the clock pulse generator 24 is higher than the frequency of the horizontal synchronizing signal and vertical synchronizing signal during slow beam scanning. Becomes large. Therefore, a horizontal synchronization signal for the slow scan mode is formed by a 1/n frequency divider 25 connected to the clock pulse generator 24, and a 1/n frequency divider 25 connected to the clock pulse generator
The NO frequency divider 26 forms the vertical synchronization signal for the slow scan mode. A sawtooth wave generator 27 for forming a sawtooth wave for horizontal scanning is connected between the 1/n frequency divider 25 and the drive circuit 22.

Further, a sawtooth wave generator 28 for forming a sawtooth wave for vertical scanning is connected between the 1/NO frequency divider 26 and the drive circuit 23. Note that the 1/n frequency divider 25 is provided with a changeover switch 29 for changing the horizontal scanning period by switching the frequency division ratio between 1, -, and -. A changeover switch 30 is connected to selectively connect resistors R, , R2, and R3 to change the slope of the vertically polarized sawtooth wave. The details of the functions of the changeover switches 29 and 30 will be described later with reference to FIGS. 4 is configured so that only the scanning pattern can be changed while keeping the scanning area constant. Therefore, the frequency divider 25 and the switch 29 form a horizontal scanning period changing circuit, and the resistors Rl, R2, R3 and the switch 30 form a vertical deflection sawtooth wave slope changing circuit. The tarok pulse generator 24 is also connected to the signal processing circuit 11 for sampling and holding, and is further connected to the beam switching pulse generator 31.

A beam switching pulse generator 31 generates a beam switching pulse synchronized with a clock pulse, and applies it to a beam switching circuit 32 for intermittently changing the first grid voltage of the image pickup tube 1. As a result, the beam is switched and projected only during low-speed beam scanning. As is clear from FIG. 2, the signal processing circuit 11 in FIG. 1 includes a sample hold circuit 33a, a low-pass filter 33b1, a pseudo dark current generation circuit 34, a marker addition circuit 78, and the like. The sample and hold circuit 33a described above is a known circuit that samples and holds each peak value of the pulsed output intermittently obtained from the video amplifier circuit 9 during narrowband operation, based on a clock signal. The pass filter is coupled to the output of the sample and hold circuit 33a to obtain an output corresponding to the envelope of the sampled and held intermittent output waveform. This circuit immediately adds a frequency signal that can be distinguished from an image signal as a marker. The pseudo dark current generating circuit 34 is a newly provided correction circuit, and its output is coupled to one input terminal of the differential amplifier 35.

Since the narrowband video signal DC component reproducing amplifier 36 is coupled to the other input terminal of the differential amplifier 35, an output obtained by subtracting the pseudo dark current signal from the video signal is obtained from the differential amplifier 35. When a signal is read out by slow beam scanning in the image pickup tube 1, the charge corresponding to the image accumulated on the photoconductive surface gradually changes due to the dark current, and the influence of the dark current differs depending on the scanning time. come. For example, in the first horizontal scanning period of one frame, there is almost no effect of dark current, but in the last horizontal scanning period of one frame, the video output is significantly affected by dark current. Therefore,
In this device, in order to eliminate the influence of the dark current mentioned above,
When receiving a pulse from the terminal 37 indicating the start of reading in the image pickup tube 1, the pseudo dark current generating circuit 34 is activated, and a triangular wave whose output increases as time passes as shown in a waveform 38 is generated. The dark current component of the narrowband video signal obtained from the output of the DC component regeneration amplifier 36 gradually increases as scanning progresses, but a pseudo dark current commensurate with this dark current is generated from the pseudo dark current generation circuit 34. , differential amplifier 3
Since it is subtracted from the video signal at step 5, differential amplifier 3
At the output of No. 5, a video signal that is less affected by dark current that changes with the progress of scanning can be obtained. FIG. 3 is a plan view schematically showing the variable speed (speed switching type) magnetic recording/reproducing device 12 in the device shown in FIG. 1, and FIG. 4 is a circuit diagram showing a part of its electrical circuit. be.

This variable speed magnetic recording device 12 has a pair of reels 39, 4.
0, equipped with a cow Yapstan 41 and a pinch roller 42,
The magnetic tape 43 is configured to run using a center drive system. Further, the tape running speed during playback is configured to be smaller than the tape running speed during recording. Further, during forward direction feeding as indicated by arrow 44, recording is performed by recording magnetic head 45, and during reverse direction feeding as indicated by arrow 46, reproduction is performed by reproducing magnetic head 47. Therefore, the capstan 41 and the reel 39,
40 rotations are reversed when switching from recording to playback. In this device, recorded signals are read by running the magnetic tape 43 in the reverse direction, but unlike audio signals, video signals may be read in the reverse direction. Furthermore, since this device switches the tape speed to a low speed during playback, it is possible to output a second narrowband video signal having a narrower frequency band than the recorded first narrowband video signal.
The output of this device 12 thereby becomes a signal that can be transmitted over a general telephone line. Note that 48 in FIG. 3 is an erasing magnetic head. Before moving on to the explanation of FIG. 4, the recording and reproducing method will be explained with reference to FIG. Magnetic tape 43 capable of
Start recording and playback from the state where the disc is wrapped.

That is, if a scale is attached to the magnetic tape 43 as shown in FIG. 5, the tape is mounted so that recording is possible from scale 1 to scale 10, and recording is performed. Now, the erasing magnetic head 48 and the recording magnetic head 45 are enabled for operation, the brakes of the first drive mechanism of the reels 39 and 40 are released, the winding by the reel 40 is started, and the first one is moved counterclockwise. When the pinch roller 42 is brought into rolling contact with the capstan 41 which is rotating at a high speed, the magnetic tape 43 starts running at the first speed in the direction shown by the arrow 44. As a result, erasing by the erasing magnetic head 48 starts from the scale 10, and when a recording signal is applied to the magnetic head 45 at the scale 9, an FM signal, for example, is saturated and recorded in the hatched area. If there is no recording signal at scale 2, the tape 4 will start at scale 1 after the marker part indicating the end of one frame has passed.
3 stops running. When reproducing the signal of the first recorded portion immediately after recording or after a certain period of time has elapsed from recording, the rotation direction of the capstan 41 and reels 39, 40 is reversed and rotated in the second direction shown by the arrow 46 at a second speed. The tape 43 is made to run. As a result, from scale 1 to scale 1
The first reproduction is performed by the reproduction head 47 up to 2. Although the recording magnetic head 45 and the reproducing magnetic head 47 are a little apart, since the tape 43 is kept running even after recording is completed, it is possible to perform reproduction from the scale 2 by the reproducing magnetic head 47. The reason why the tape is run beyond the first recorded portion during playback is to uniformly and reduce wear on the tape 43 and to use one tape for a long time. The control to make the playback tape run an extra △L from scale 10 to 12 detects the end of the recording signal at scale 9, and thereby makes the timer configured with a monostable multivibrator compatible with LD. This is accomplished by only operating the device for the specified amount of time. The first playback is scale 12
When recording the second time, press arrow 4.
By running the tape in the direction 4, the area from scale 12 to scale 3 becomes a recording mode area. After the second recording is completed,
A second reproduction is performed from scale 3 to scale 14. As a result, in one recording and playback, the tape 43 moves △L to the left reel 3.
It will be taken up by 9. If the above-described recording/reproducing method is adopted, since reproduction is performed by running in the reverse direction, there is no need to rewind the tape, and rapid reproduction is possible. Furthermore, the number of tape transfers is reduced, and tape wear is reduced. Furthermore, since the tape is moved by ΔL, the wear of the tape becomes uniform and one tape can be used for a long time. Next, referring to FIG. 4, the electric circuit portion of the device shown in FIG. 3 will be described.
are connected to an FM modulator 50 and a bandpass filter 51, respectively, and the primary narrowband video signal includes a one-frame start marker signal 52 and a one-frame end marker signal 53 shown in FIG. 7A. When inputted manually, first, the start end marker signal 52 passes through the bandpass filter 51 and the seventh
The signal becomes the signal shown in FIG. 7B, and the marker signal 52 is detected by the detection circuit 54 connected to the output of the filter 51 in the waveform shown in FIG.

The output of the detection circuit 54 is input to a trigger input terminal of a trigger flip-flop type recording control flip-flop 55. If the output of the flip-flop 55 is at a low level in the set state, the first trigger signal indicating the start of recording is input to the manual terminal, and the output of the flip-flop 55 is inverted to a high level. After being slightly delayed by the delay circuit 56, it is applied to the base of the transistor 58 via the resistor 67, and the transistor 58 is turned on. Since a record setting relay 60 is connected between the power supply terminal 59 and the ground via the transistor 58, the relay 60 is activated when the transistor 58 is turned on, and the switches 61, 62, 63, 64, 65 are activated.
, 66, 67 are activated. Also, the output of the delay circuit 56 is 0.
Coupled to the base of transistor 70 through R-gate 68 and resistor 69, the high level output of flip-flop 55 turns transistor 70 on;
A tape running relay 72 connected through a transistor 70 between the power supply terminal 71 and the ground is activated. When the relay 72 is activated, the reel 3 is activated by the action of an electromagnetic plunger, similar to a general tape recorder (not shown).
The brakes 9 and 40 are released, the pinch roller 42 rolls into contact with the capstan 41, and the tape 43 starts running. Since the device of this embodiment is a three-motor type, it is provided with a reel motor 73 for driving the left reel 39, a reel motor 74 for driving the right reel 40, and a cow-yabustan motor 75. .

The left reel motor 73 has ten power terminals 76 and one power terminal 77.
The right reel motor 74 is connected between the 1st power terminal 76 and the 1st power terminal 77 through a switch 67. The switch 66 and the motor 73 are directly connected through a contact a, or are connected through a contact b and a resistor 79. Further, the switch 67 and the motor 74 are connected through a contact a and a resistor 80, or directly connected through a contact b. The contacts a of the switches 66 and 67 of this reel motor circuit are normally closed contacts that are closed in the playback state, and the contacts b are normally open contacts that are closed in the record state, so when the record setting relay 60 is activated, the switch is closed. Contacts b of 66 and 67 are closed, a DC voltage for tape winding is applied to the right reel motor 74, and a low DC voltage for back tension is applied to the left reel motor 73 via a resistor 79. . Right reel motor 74
are connected in a polarity that rotates the reel 40 counterclockwise in FIG. 3, and the left reel motor 73 is connected in a polarity that rotates the reel 39 clockwise in FIG. Reel 40 overcomes reel motor 73
is rotated counterclockwise to run the magnetic tape 43 in the direction of arrow 44. At this time, the left reel motor 73 to which a low voltage is applied acts to apply back tension. The Chiyapustan motor 75 has a changeover switch 64,
It is connected to ten power supply terminals 82 and one power supply terminal 83 via 65.

That is, in the playback state, the switches 64 and 65 are connected to the power supply through the contacts a and the resistor 84, and the capstan 41 rotates clockwise as shown in FIG. The capstan 41 is rotated counterclockwise as shown in FIG. Therefore, if the relay 60 operates, the switches 64 and 65
Contact b is closed, and the capstan motor 75 is connected to the tape 4.
3 is rotated to feed at a constant speed in the direction of arrow 44. A switch 61 connected to the reproducing magnetic head 47 is opened when the relay 60 is activated, and a switch 62 connected to the recording magnetic head 45 is closed in response to the activation of the relay 60 and connected to the erasing magnetic head 48. The switched switch 64 closes in response to the activation of the relay 60.

Therefore, when the recording setting relay 60 is activated, an erase signal is applied from the terminal 85 to the erase head 48 and the magnetic tape 4 is
Erasing in step 3 is performed and the recording magnetic head 45 becomes ready for recording. FM modulator 50 and switch 6
Since a coupling capacitor 86 and a recording amplifier circuit 87 are connected between 2 and 2, when the switch 62 is closed,
Preparations are now made to record the FMR adjusted video signal. However, during the period when the start marker signal 52 shown in FIG. 7A is being generated, the signal shown in FIG. , transistor 89 turns on. Therefore, while the marker signal is being generated, the video signal transmission line is grounded and the marker signal is not recorded on the tape by the recording head 45. When the start end marker signal disappears and the transistor 89 turns off, the video signal for one frame shown in FIG.
M is recorded. When the recording of the video signal for one frame is completed and the end marker signal 53 shown in FIG. At the same time, the output of the detection circuit 54 is applied as a second trigger signal to the flip-flop 55, and the output of the flip-flop, which has been in a high level output state until now, is inverted to a low level state.

The low level signal is sent through delay circuit 56 so that transistors 58 and 70 are turned off with a delay. As a result, all of the recorded tape portion is transferred to the playback magnetic head 4.
7 to the right in FIG. 3, the relays 60 and 72 are switched to a non-operating state. When relays 60 and 72 become inactive, switch 61 closes and switch 6
2 and 63 are opened, and the contacts a of switches 64, 65, 66, and 67 are closed to switch to a playable state, and at the same time, the tape drive mechanism comes to a stopped state. That is, the pinch roller 42 is separated from the capstan 41, the reel stand is put into a braking state, and tape running is stopped. When reading out a recorded signal, a playback switch (not shown) is operated, or the playback signal is manually read out from the terminal 90 using an automatic reversing circuit. Since the terminal 90 is connected to the preset terminal of the play flip-flop 91, when a low-level reproduction signal is input, a high-level output is generated from the flip-flop 91, and the transistor 70 is turned on. Therefore, the tape 1 drive relay 72 is activated and the tape starts running. In this regeneration state, since the relay 60 is not operating, the contacts a of the switches 64, 65, 66, and 67 are kept closed. Therefore, the capstan motor 75 rotates in the opposite direction to that during recording, and because it is energized via the resistor 84, it rotates at a slower speed than during recording. In addition, the left reel motor 73 is energized by the winding voltage without using a resistor.
Since the right reel motor 74 is energized by the back tension voltage through the resistor 80, the left reel motor 73 overcomes the right reel motor 74 and rotates the reel 39 clockwise. The output circuit of the reproducing magnetic head 47 includes a switch 6.
1. Since the coupling capacitor 92, the reproduction amplification circuit 93, and the output terminal 94 are connected in sequence, recording is performed while the switch 61 is closed and the magnetic tape 43 is running at low speed in the opposite direction indicated by the arrow 46. A reproduced output of the signal is available at terminal 94.

Since the tape 43 is running at a slower speed than when it was recorded, this reproduction output is a secondary narrowband U-arm signal whose band is narrower than that of the human-powered video signal, and is a signal sufficient to be transmitted through a telephone line. An envelope detection circuit 9 consisting of a diode 95, a capacitor 96, and a resistor 97 is connected between the regenerative amplifier circuit 93 and the clear terminal of the flip-flop 91.
8. Since the amplifier 99, the monostable multivibrator 100, and the differentiating circuit 108 consisting of the capacitor 106 and the diode 107 are connected in sequence, the flip-flop 91 is cleared at the trailing edge of the output pulse of the monostable multivibrator 100, and its Output switches to low level.

That is, the signal shown in FIG. 7D having a width from t1 to T2 corresponding to one frame of the video signal shown in FIG. 7A is obtained at the output of the amplifier 99. No video output on T2,
When switched to a low level, this trailing edge triggers the monostable multivibrator 100 to generate a pulse with a time width corresponding to the LD in FIG. When the trailing edge of the delay pulse corresponding to the LD is reached, the play flip-flop 91 is cleared by this pulse trailing edge signal, the transistor 70 is turned off, and the relay 72 is deactivated. Therefore, the magnetic tape 43 stops after running from scale 9 to scale 12, where there is no recording signal. Returning to FIG. 1 again, the switch 29 that changes the frequency division ratio of the frequency divider 25 and the switch 30 that changes the vertical deflection current are interlocked, and when the contact a of the switch 29 is closed, the switch 30 is closed. When the contact b of the switch 29 is closed, the contact b of the switch 30 is closed.
is closed, and when the contact c of the switch 29 is closed, the switch 3
0 contact c is closed.

In this device, the product THA×VA of the horizontal scanning period THA and the vertical deflection current IVA when the switches 29 and 30 are connected to the contact a, and the product THA×VA of the horizontal scanning period THA and the vertical deflection current IVA,
The product THBXIVA of the horizontal scanning period THB and the vertical deflection current VA in the state where the switch
It is set so that the product THC×Vc of the horizontal scanning period THC and the vertical deflection current 1vc in the state where the contacts 9 and 30 are connected to the contact c is equal to each other. That is, THA゜×
It is set so that IVA=THBXIVB=THC×c=constant. When the contacts a of the switches 29 and 30 are closed, the area surrounded by the rectangle indicated by solid lines 101 in FIGS. 8A and 8C becomes the beam scanning range. That is, the scanning range has an aspect ratio of 3:4 in a general TV system. Furthermore, when the contacts b of the switches 29 and 30 are closed, the horizontal scanning period THB is shorter than that of the η method while the slope of the horizontal deflection sawtooth wave is kept constant as shown in FIG. On the other hand, as shown in FIG. 10, when the vertical scanning period is kept constant, the amplitude 1VB of the vertical deflection current becomes larger than A, that is, the slope of the vertical deflection sawtooth wave becomes large, and as a result, Dotted line 1 in Figure 8B
A square scanning area (range) indicated by 02 can be obtained. Further, when the contacts c of the switches 29 and 30 are closed, THA<THC and 1>Ivc, and a rectangular scanning range shown by the dotted line 103 in FIG. 8 can be obtained. What we need to pay attention to here is Figure 8A.
The area of the square with an aspect ratio of 3:4 shown by the solid line 101 is the area of the regular square shown with the dotted line 102 in FIG. 8B, and the area of the square with an aspect ratio of 1:2 shown by the dotted line 103 in FIG. This means that each area is equal to the area of the ratio rectangle. As mentioned above, if each pattern has the same scanning area and the same beam scanning speed, it means that the total scanning time is the same, and the resolution is also the same. Further, when slow beam scanning is performed and the beam is switched as in this embodiment, it means that the number of samples is equal in each pattern, and the sampling point density and scanning line density are also equal. Therefore, with this device, the 8th
When imaging a square object as shown by the chain line 104 in Figure A, instead of using the standard scanning pattern shown by the solid line 101, the object image on the image pickup tube is enlarged using the lens 3. , an image is formed as shown by a chain line 104a in FIG.
The scanning pattern is changed to the one shown by the dotted line 102. As a result, the scanning pattern and the imaging of the subject match, and a still image can be read out with good resolution. Furthermore, when transmitting an object as shown by the dashed line 105 in FIG. 8, a pattern with an aspect ratio of 1:2 as shown by the dotted line 103 in FIG. The image of the subject is enlarged and read using the lens 3. High-resolution reading can also be done in this way. When using the device shown in Figure 1 to obtain the same standard video signal as a general video camera, switch 16 and 17 are connected to contact b. Then, the switch 78 is closed and an image is taken.

Thereby, a still image signal or continuous image signal output can be obtained from the terminal 10 in exactly the same way as a general TV camera. On the other hand, when obtaining a still image signal by low-speed beam scanning, standard beam scanning is performed with the shutter 2 closed to erase the afterimage and prepare for writing a still image. Thereafter, switches 16 and 17 are placed at contact point a, and switch 78 is turned off at the same time. As a result, a current for low-speed deflection is supplied from the low-speed horizontal drive circuit 22 to the horizontal deflection coil 14, and a current for low-speed deflection is supplied from the low-speed vertical drive circuit 23. At the same time, the beam switching circuit 3 is transmitted from the beam switching pulse generator 31.
A switching signal is applied to 2. The beam is thus projected onto the photoconductive film 4 in a switched manner, and the video signal is read out intermittently or in a sampled manner. Now, assuming that FIG. 6A is a video signal read out at a standard scanning speed, this readout time is T. It takes several hundred times the read time T1 to read out the data. That is, in standard scanning, one frame is read out in 1/30 seconds, but it is read out in about 20 seconds, for example. Furthermore, if reading is performed over a long period of time, it will be affected by dark current as described above with reference to FIG. 2, so this is corrected using a pseudo dark current. In the signal processing circuit 11, the peak value of the sample output is held in synchronization with the clock pulse, and a signal as shown in FIG. 6B is formed. Sample hold circuit 33a
The output is smoothed by the filter 33b to become a video signal as shown in FIG. 6C, and after dark current correction and addition of magnetic force, it is outputted from the terminal 11a as a first-order narrowband video signal. The first narrowband video signal is a magnetic recording/reproducing device 1
2 and then read out over a long time T2 as shown in FIG. 6D, resulting in an even narrower band.
This becomes a secondary narrowband video signal that can be transmitted over a telephone line or the like. As is clear from the above embodiment, in a facsimile system using a television camera, a horizontal scanning period changing circuit consisting of a frequency divider 25 and a switch 29, and a resistor R are used.
,, R2, R3 and a vertical deflection sawtooth wave slope changing circuit consisting of a switch 30, and only the aspect ratio is changed while keeping the scanning area approximately constant, the aspect ratio can be changed according to the shape of the subject. It becomes possible to form a video signal that can obtain the most precise reproduced image by changing the .

Furthermore, since the scanning period of one frame is kept constant, the transmission time does not change even if the aspect ratio is changed, and signal processing, reproduction, etc. do not become complicated. Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and can be further modified.

For example, the horizontal scanning period and the slope of the vertical deflection sawtooth wave may not be changed step by step using the switches 29 and 30, but may be changed in conjunction with each other.

[Brief explanation of the drawing]

1 is a block diagram showing a still image signal forming device according to an embodiment of the present invention, FIG. 2 is a block diagram showing a signal processing circuit in the device shown in FIG. 1, and FIG. 3 is a block diagram showing the device shown in FIG. 1. A schematic plan view showing the magnetic recording and reproducing device in
FIG. 5 is an explanatory diagram for explaining two methods of recording and reproducing using the device shown in FIG. 3; FIG. 6 is a waveform diagram showing signal states of each part of FIG. 1; Figure 7 is the 4th
Figure 8 is a front view showing the scanning pattern of the image pickup tube in Figure 1. Figure 9 is a waveform diagram showing the signal state of each part in the figure.
A waveform diagram showing the changes in the frequency divider 25 and the sawtooth wave generator 27 when the switch 29 is switched in the device shown in the figure, and FIG. FIG. 3 is a waveform diagram showing changes in the output of In addition, in the symbols used in the drawings, 1 is an image pickup tube, 2 is
1 is a mechanical shutter, 11 is a signal processing circuit, 12 is a fixed head type variable speed magnetic recording/reproducing device, 13 is a secondary narrow band video signal output terminal, 25 is a frequency divider, 27, 28
is a sawtooth wave generator, N29, 3O is a changeover switch, 34
35 is a differential amplifier; 41 is a capstan; 42 is a pinch roller; 43 is a magnetic tape;
4 is an arrow, 45 is a recording magnetic head, 46 is an arrow, 47 is a reproduction magnetic head, 60 is a recording setting relay, 61, 62,
63, 64, 65, 66, 67 are switches, 72 is a relay, 73 is a left reel motor, 74 is a right reel motor, 7
5 is a capstan motor.

Claims (1)

[Claims] 1. An image pickup tube having horizontal deflection means and vertical deflection means, and a lens for enlarging and reducing an image corresponding to a subject, and a horizontal deflection sawtooth wave applied to the horizontal deflection means. a horizontally polarized sawtooth wave generator for supplying a horizontally polarized sawtooth wave generator; and a vertically polarized sawtooth wave generator for supplying a vertically polarized sawtooth wave to said vertical deflection means;
a horizontal scanning period changing circuit configured to change the horizontal scanning period while keeping the slope of the horizontal deflection sawtooth wave constant; and a horizontal scanning period changing circuit configured to change the slope of the vertical deflection sawtooth wave while keeping the vertical scanning period constant; The vertical deflection sawtooth wave is formed so that the slope thereof decreases as the horizontal scanning period increases, inversely proportional to the horizontal scanning period, and the scanning area remains approximately constant. and a vertical deflection sawtooth wave slope changing circuit formed so that the slope of the vertical deflection sawtooth wave changes in conjunction with a change in the horizontal scanning period in the horizontal scanning period changing circuit. 2. The imaging device according to claim 1, wherein the horizontal scanning period changing circuit comprises a frequency divider that generates a horizontal synchronizing signal, and a frequency division ratio changeover switch that changes the frequency division ratio of the frequency divider. 3. The vertical deflection sawtooth wave slope changing circuit comprises a resistance circuit that changes the amplitude of the output current of the vertical deflection sawtooth wave generator, and a resistance changeover switch that is linked to change of the horizontal scanning period. The imaging device according to item 1.