JPH0359849A - Image data recording device - Google Patents

Abstract

PURPOSE:To reproduce the light and darkness of a background by providing an AC bias means, a frequency modulation means and 1st and 2nd magnetic heads for recording outputs of the AC bias means and the frequency modulation means on a magnetic recording medium respectively. CONSTITUTION:A measuring picture data C is inputted to a signal distributor 30, and is distributed to be outputted to two output lines. One distributed output is inputted to a band pass filter 31 to be band-separated, and only a high frequency component is outputted. The other distributed output is inputted to a low pass filter 32 to be band-separated, and only a low frequency component is outputted. Then, only the low frequency component of the measuring picture data is frequency-modulation(FM)-recorded, while the others, i.e. a distance data A, a rotary synchronizing signal B and the high frequency component of the measuring picture data are AC-bias-recorded. By this method, a DC component of an input picture data can be reproduced, and the picture data can be reproduced including light and darkness of its background part.

Description

Detailed Description of the Invention [Industrial Field of Application] This invention relates to an image recording system for recording noisy image data, such as image data of a tunnel wall surface, on a magnetic recording medium.
The present invention relates to an image data recording device.

[Conventional technology]

For example, Japanese Patent Application No. 61-273380 and Japanese Patent Application No. 62-23 are used as devices for detecting cracks occurring on the walls of tunnels in waterways, roads, railways, etc.
No. 6618 has already been filed by the present applicant.

In these technologies, laser light is irradiated onto the tunnel wall,
This method utilizes the phenomenon that when this laser scattered light is measured from a direction different from the irradiation direction, if there is a crack, the laser scattered light becomes significantly smaller due to a shadowing phenomenon.

That is, in these conventional techniques, as shown in FIGS. 7 and 8, a scanning device 2 and a sensing device 3 are mounted on a vehicle 1, and image data of a tunnel wall surface 4 is obtained using these devices. A pulse generator 5 for measuring travel distance is attached which outputs a number of pulse signals proportional to the travel distance by interlocking the vehicle.

The scanning device 2 includes a laser oscillator 6, a mirror holder 7, a motor 8, and the like.

When a laser beam L from the laser oscillator 6 is incident on a mirror 9 fixed to a mirror holder 7 rotated by a motor 8, the laser beam L is reflected by the mirror 9, and then is incident on the tunnel wall surface 4. As a result, the tunnel wall surface 4 is scanned along the circumferential direction.

In this way, the person 1 is placed approximately perpendicularly to the tunnel wall surface 4.
The emitted laser beam L is vertically opposed and scattered by the tunnel wall surface 4.

The sensing device 3 is separated from the condenser lens 1o and the light receiving sensor 11, and the condensing lens 10 and the light receiving sensor 11 are arranged at a predetermined distance from the mirror 9 so as to receive the scattered light. The crack occurrence position is detected by subjecting the output of the light receiving sensor 11 to 1iTij image processing.

Note that the scanning device 2 is provided with a half mirror 12 and a light receiving sensor 13.
A light reception signal is output from each rotation of the laser beam. That is, the output of the light receiving sensor 13 is used as a rotation synchronization signal.

By the way, the total Jll+ image data (output of the light receiving sensor 11), distance data (output of the distance measurement pulse generator 5) and rotation period signal (output of the light receiving sensor 13) obtained by such FM configuration are transmitted to the vehicle 1. The information is temporarily recorded on magnetic tape by an on-board VTR device (video tape recorder). The magnetic tape on which the data has been recorded is played back after the measurement by the vehicle is completed, and the playback signal is further stored in a memory such as RAM.
Next, the crack is recognized by being recorded on a recording device and subjected to image processing, and the recognized image is output to a printer, monitor, etc.

By the way, in such a device, a VTR is used to record the data in the above-mentioned total 1IIJ, as described above, and the recording method of the VTR has conventionally been generally a frequency modulation (FM) recording method or an AC bias recording method. Direct recording methods such as the following are used.

[Problem to be solved by the invention]

However, although the above-mentioned FM recording method has the advantage of being able to record direct current and low frequency signals and having little noise in the reproduced signal, it does not use the recording bandwidth of the VTR over the entire frequency range. There are inconveniences, i.e.
In FM recording, a total of 7 complete signal representations of 1p1 data are recorded.
In order to do this, the recording bandwidth of the VTR needs to be N times the frequency range of 41 frequencies for a total of 11111 data. Conversely, V
There is a problem that only 1/N of the recording band width of TR can be used.

Furthermore, in the AC bias recording method, (1) the DC component of the data signal cannot be reproduced because it is affected by the differential characteristics of the magnetic head, and the brightness and darkness of the background cannot be reproduced;

■A lower limit is set for the data recording frequency band.

■The S/N ratio is lower than that of FM recording.

There are other problems.

[Means to solve the problem]

In the present invention, an image data recording apparatus for recording image data on a magnetic recording medium includes a frequency separation means for separating image data into a high frequency component and a low frequency component, and an alternating current bias signal applied to the frequency separated high frequency component signal. AC bias means for superimposing, frequency modulation means for frequency modulating the frequency-separated low frequency component signal, and first and second frequency modulation means for respectively recording each output of the AC bias means and the frequency modulation means on the magnetic recording medium. 2 magnetic heads.

[Effect]

That is, the present invention attempts to separate image data into high frequency components and low frequency components, record the high frequency components using an AC bias method, and record the low frequency components using a frequency modulation (FM) method.

〔Example〕

Hereinafter, the present invention will be described in detail according to embodiments shown in the accompanying drawings.

FIG. 1 shows an embodiment of the present invention, (a
) shows the configuration on the recording side, and (b) shows the configuration on the reproduction side.

In FIG. 1(a), the distance data output from the pulse generator 5 for the distance meter δPJ shown in FIG. be done. The distance data superimposed with a predetermined alternating current bias is then amplified by an amplifier 22 and then written to the first track of the magnetic tape 40 by a recording head 23.

Similar to the above distance data, the rotation period signal output from the light receiving sensor 13 in FIG. Written in recording format.

On the other hand, the measurement image data output from the light receiving sensor 11 shown in FIG. 8 is input to the signal distributor 30, and the distributor 30 distributes and outputs the data to two output lines. One of the distributed outputs is input to a bandpass filter 31, where the filter 31 separates the bands and outputs only high frequency components. The other distributed output is sent to the low pass filter 3
2 and is band-separated by the filter 32,
Only low frequency components are output. Band pass filter 31
The high frequency component signal outputted from the AC bias generator 33 is input to a mixer 34, where the output of the AC bias generator 33 is superimposed. The high frequency component signal on which the AC bias is superimposed is amplified by an amplifier 36 and then written to the third track of the magnetic tape 40 by the recording head 36. On the other hand, the low-frequency component signal output from the low-pass filter 32 is input to the FM modulator 35, where the signal is subjected to frequency modulation, and then input to the recording head 39 via the amplifier 37. The recording head 39 writes on the fourth track of the magnetic tape 40. In this way, in this embodiment, in the data collected by the measurement vehicle, only the low frequency component of the measurement image data is FM modulated and recorded, and the other distance data, rotation synchronization signal, and high frequency components of the measurement image data are recorded. is recorded as an AC bias.

On the other hand, in FIG. 1(b), the distance data recorded on the first track of the magnetic tape 40 is reproduced by a reproducing head 41. In FIG. This reproduced data is amplified by an amplifier 42 and then input to a signal flattener (for example, an equalizer) 43, where the signal is processed to have a flat frequency characteristic. The output of the signal flattener 43 is further transmitted to a synchronization circuit 44.
is input to the waveform shaper 45 via the waveform shaper 45, and is waveform-shaped by these at the same timing as the input signal to the mixer 21,
Further, the signal is amplified by an amplifier 46 to the same level as the input signal.

The reproduction of the rotation synchronization signal is similar to this, and the reproduction head 4
7 from the second track of the magnetic tape 40, an amplifier 48, four signal amplifiers, and a synchronization circuit 50.
, a waveform shaper 51, and an amplifier 52, the signal is subjected to the same signal processing as described above and then output.

That is, the distance data and rotation synchronization signal input to the mixers 21 and 25 are as shown in FIG. 2(a).
These signals, which periodically change at a predetermined level, are recorded using the AC bias method, and after being reproduced and flattened, they become differential waveforms that do not have DC components, as shown in Figure 2 (b). becomes. Therefore, in this embodiment, the differential wave is waveform-shaped at the same timing as the input signal (FIG. 2(c)), and further amplified to the same level as the input signal by amplifiers 46 and 52.

Next, the high frequency components of the measurement image data recorded on the third track of the magnetic tape 40 are reproduced by a reproduction head 53, and then passed through an amplifier 54 and a signal flattener 55, where they are amplified and flattened as described above. (posterior) eye corrector 56. The phase corrector 56 adjusts the high frequency component signal to be the same as the low frequency component signal in order to correct the phase difference caused by the difference in frequency characteristics between the high frequency component signal and the low frequency component signal recorded on the magnetic tape 40. I am trying to add phase correction so that the phase is the same.

The high frequency component signal to which the phase correction has been added is then input to the band pass filter 57.
At step 7, low frequency signals mixed in due to disturbances etc. are removed. Then, the output of the bandpass filter 57 is input to the signal synthesizer 63.

On the other hand, the low frequency signal of the Ishikawa image data recorded on the fourth track of the magnetic tape 40 is reproduced by the reproducing head 58, and is further amplified and flattened by passing through five amplifiers and a signal flattener 60. After that, it is input to the demodulator 61. The demodulator 61 demodulates the input signal to the original signal before FM modulation, and inputs the demodulated signal to the low-pass filter 62 .

The low-pass filter 62 removes high-frequency signals mixed in due to disturbances, etc., and inputs its output to the signal synthesizer 63.

The signal synthesizer 63 combines the high frequency component signal output from the band pass filter 57 and the low frequency component signal output from the low pass filter 62, and restores the original =1 lesson image data.

That is, a total of 71P1 image data inputted to the signal distributor 30 has DC components superimposed thereon according to the brightness and darkness of the background, as shown in FIG. The high frequency components are recorded and reproduced by the AC bias recording method, and the band pass filter 57 outputs a signal from which the DC components have been removed, as shown in FIG. 3(b), and the low frequency components of the measured image data are By recording and reproducing using the FM recording method, the low-pass filter 62 outputs a DC component signal corresponding to the background as shown in FIG. Figure 3 (d
), a signal having exactly the same form as the input signal is restored.

As described above, in this embodiment, the distance data and the rotation synchronization signal are recorded and reproduced using the AC bias method, and then are processed by the synchronization circuits 44 and 50 and the waveform shapers 45 and 51 at the same timing as the input signal. Added waveform shaping processing. Therefore, the input rotation synchronization signal shown in FIG. 4(a) has completely the same shape as shown in FIG. 4(b), 12!
? will be played.

Incidentally, in the prior art, since synchronization and waveform shaping were not performed after reproduction, the differential waveform and DC component of the reproduced signal could not be reproduced as shown in FIG. 4(c).

In addition, in this embodiment, for the measured image data, the K frequency component is recorded and recorded using the AC bias recording method.
Since the low frequency components are recorded and reproduced using the FM recording method, as shown in Figure 5(b), even the DC component can be reproduced properly, making it possible to reproduce the brightness and darkness of the tunnel wall. .

Incidentally, in the prior art, as shown in FIG. 5(c), since the direct current component was not reproduced, the brightness and darkness of the tunnel wall surface was not reproduced, and an entirely dark image was reproduced.

Figure 6 shows input 1 when pouring only the DC component of the signal.
This is an experimental result showing the relationship between the No. 3 level and the reproduced signal level, and it was confirmed that the input signal can be faithfully reproduced according to this example.

In addition, in this example, the high frequency components of the measurement image are subjected to differential processing, so the edge enhancement effect due to differentiation is obtained, making it possible to emphasize cracks compared to the image, making subsequent recognition processing easier. It can be done.

Incidentally, in this embodiment, the present invention is applied to image data of a tunnel wall surface containing cracks, but the present invention may also be applied to other image signals such as ultrasonic signals that require high-density recording. You may also do so.

〔Effect of the invention〕

As described above, according to the present invention, it becomes possible to reproduce the DC component of input image data, and thereby it becomes possible to faithfully reproduce even the brightness and darkness of the background portion of the image data. Furthermore, it becomes possible to effectively utilize the recording band of the VTR, and high-density reproduction with a low S/N ratio becomes possible.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are block diagrams showing an embodiment of the present invention, FIGS. 2 to 5 are time charts for explaining the operation of the embodiment, and FIG. 6 is an experiment of the embodiment. A graph showing the data, FIG. 7 is an external view showing an example of a vehicle equipped with a tunnel crack measuring device, and FIG. 8 is a conceptual diagram showing an example of the configuration of the tunnel crack meter 11 pJ device. 1...Measuring vehicle, 2...Scanning device, 3...
・Sensing device, 4... Tunnel wall surface, 5... Traveling distance pulse generator, 6... Laser oscillator, 8...
・Motor, 9... Mirror 11. 13... Light receiving sensor, 12... Half mirror
20, 24, 33...AC bias generator, 21.2
5.34... Mixer, 23.27, 38.39... Recording head, 30...
Signal splitter, 31.57...Band pass filter, 32.62...
-Low pass filter, 35...FM modulator, 41.47.53.58...Reproduction head, 44.50
... Synchronous circuit, 45.51 ... Waveform shaper, 56.
. . . Phase corrector, 61 . . . Demodulator, 63 . . . Signal synthesizer. Figure 2 Figure 3 Sword f1 Shibe'IL (V) Figure 4

Claims (3)

[Claims] (1) An image data recording device that records image data on a magnetic recording medium, comprising: a frequency separation means that separates the image data into a high frequency component and a low frequency component; and an AC bias signal that is superimposed on the frequency separated high frequency component signal. AC bias means, frequency modulation means for frequency modulating the frequency-separated low frequency component signal, first and second frequency modulation means for respectively recording each output of the AC bias means and the frequency modulation means on the magnetic recording medium. An image data recording device comprising a magnetic head. (2) a first for reproducing recorded data on the recording medium recorded by the first and second magnetic heads, respectively;
a second reproducing head; demodulating means for demodulating the reproduced data of the second reproducing head; high frequency separating means for separating high frequency components of the reproduced data by the first reproducing head; and from the demodulated data of the demodulating means. 2. The image data recording apparatus according to claim 1, further comprising: low frequency separation means for separating a predetermined low frequency component; and signal synthesis means for synthesizing the respective outputs of the high frequency separation means and the low frequency separation means. (3) further comprising a phase correction means for synchronizing the phase of the reproduction data of the first reproduction head with the phase of the reproduction data of the second reproduction head, and inputting the output of the phase correction means to the high frequency separation means. The image data recording device according to claim (2), wherein the image data recording device is configured as follows.