JPS5927546B2 - Video equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an imaging device, and particularly to an imaging device having an optical deflector that performs reciprocating rotation.

Imaging devices, detection and tracking devices, etc. that utilize infrared rays generally use a photon type infrared detector, and scan the object surface by combining this with an optical scanning system.

FIG. 1 shows a simplified system diagram of a conventional infrared imaging device.
In FIG. 1, light emitted from a point P on an object surface 1 is turned into a real image by an imaging optical system, such as a convex lens 2, and is projected onto an infrared detector 3 (hereinafter simply referred to as the detector). However, an optical deflector, in the case of the figure, a plane mirror 4 is installed in a part of the optical path to bend the optical path, and a detector 3 is placed on this bent optical path.
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If the plane mirror 4 is arranged in this manner and rotated as shown by the arrow 5, the real image of the object surface 1 will move on the detector 3, so that object surface scanning will be performed. In the above-mentioned imaging device, when the plane mirror 4 is rotated back and forth as shown by the arrow 5, it is difficult to keep the rotational angular velocity ω constant due to the inertia of the plane mirror 4, and the value of ω is difficult to maintain. changes sinusoidally over time.

If the rotational angular velocity ω of the plane mirror 4 changes in this way, the moving speed of the real image described above will no longer be constant. This has the disadvantage of causing distortion. Therefore, in the conventional device, the plane mirror 4 is fixed to the torsion bar 7, and the torsion bar 7 is caused to vibrate torsionally. At this time, the electromagnetic force for driving the torsion bar 7 is controlled to keep ω constant over a certain angular range. I was trying to make it happen. In FIG. 1, the electronic circuit system around the detector 3 and the cathode ray tube 6 is omitted. However, the above-mentioned conventional imaging device requires a torsion bar and its driving means (twisting force applying means), and has drawbacks such as generation of noise and large power consumption.

The present invention has been made in view of the above-mentioned points, and it is an object of the present invention to provide a new video device that does not require a torsion bar and is capable of obtaining distortion-free video only by devising an electronic circuit system. .

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a video device according to the present invention will be described in detail below with reference to the drawings. Note that the same reference numerals are used for equivalent parts in each figure below. FIG. 2 shows the configuration of an embodiment of the present invention as a simplified system diagram, and the amplifier for the electric signal output from the detector 3 and the like are omitted for convenience.

The electrical system of this embodiment is formed around a timing signal generation circuit 70. This signal generating circuit 70 regulates the timing of the operations of the respective blocks 8, 9, and 10 connected thereto. Of these, block 8 generates a horizontal scanning signal, and block 9 generates a vertical scanning signal.
These two signals are respectively applied to the deflection plates of the cathode ray tube 6 to perform a well-known sweeping operation.

However, in this embodiment, a waveform different from the normal sweep waveform is used as the horizontal scanning signal, and this point will be described in detail later. Both of the above-mentioned processes 8 and 9 (hereinafter referred to as horizontal sweep circuit and vertical sweep circuit, respectively)
A synchronizing signal for the timing signal generating circuit 70 is supplied from the timing signal generating circuit 70.

The timing signal generation circuit also supplies an operation timing regulation signal to the block 10. Next, the block 10 in this figure shows the drive mechanism that rotates the rotary mirror 4 and the generation circuit of the power signal supplied thereto as one block for convenience, and the timing of generation of the power signal is shown as one block. It is controlled by a timing signal generation circuit 70.

Therefore, in this embodiment, the synchronization of all signals is guaranteed within the timing generation circuit 70, and there is no need to obtain a synchronization signal from the drive mechanism. The block 10 will hereinafter be referred to as the drive. Now, one of the main features of the present invention is that one of the scanning signals, in the embodiment shown in FIG. use.

This waveform will be described in detail later, and FIG. 3 shows the basic configuration of the horizontal sweep circuit 8. 11 in this figure
A sawtooth wave generation circuit, 12 a sine wave generation circuit, 13 a sine wave level adjustment circuit, 14 both of the above circuits 11 and 12
This is an adder circuit that adds the outputs of 15a and 1.
5b is a synchronizing signal input terminal, and 16 is an output terminal. The sawtooth wave generation circuit 11 generates a normal sawtooth wave by the synchronization signal applied to the synchronization signal input terminal 15a, while the sine wave generation circuit 12 is synchronized with a separate synchronization signal applied to the terminal 15b = constant frequency. Continuously outputs a sine wave. The frequency of this sine wave is set to twice the repetition frequency of the sawtooth wave, and this is set to the level adjustment circuit 13.
The signal is applied to the adder circuit 14 via. In this way, by adding both the sawtooth wave and the sine wave, a modified sawtooth wave is formed in which the voltage rises faster in the center and lower at both ends, and this waveform is taken out from the output terminal 16.

This output is applied to the horizontal deflection plate of the cathode ray tube as described above. FIG. 4 shows the waveforms of signals appearing in the main parts of the circuit shown in FIG. 3, where A is the output voltage waveform of the sawtooth wave generation circuit 11 and B is the output voltage waveform of the sine wave generation circuit 12. , C is the waveform of the horizontal scanning signal appearing at the output terminal 16.

As mentioned above, the waveform C is applied to the horizontal deflection plate of the cathode ray tube. Note that in waveform C, a diagonal dotted line a shows a sawtooth wave before addition for comparison. The waveform C is a modified sawtooth wave formed by adding waveform A and waveform B. However, the degree of deformation is a sawtooth wave A
It is adjusted by the mixing ratio of sine wave B and sine wave B. In this embodiment, for convenience of understanding, the above-mentioned mixing ratio adjustment is performed by adjusting the output level of the sine wave generation circuit 12 using the level adjustment circuit 13. A separate level adjustment circuit may also be provided on the output side. By using the waveform shown in FIG. 4C as a horizontal scanning signal, it is possible to avoid image distortion due to non-uniform rotational speed of the rotating plane mirror described in the first part of this specification.

This point will be explained below. As described above, when the plane mirror is rotated back and forth, the rotational angular velocity of the plane mirror changes sinusoidally due to the inertia of the plane mirror.

That is, the rotational angular velocity is low near the maximum displacement point of the plane mirror, and high in the middle between the two maximum displacement points. However, for convenience, the term "maximum point" in this case means the point in time when the absolute value of the deviation angle is maximum. Therefore, the time required to scan a constant width on the object surface is long near the maximum displacement point and short in the middle. At this time, if the horizontal scanning signal is a linear sawtooth wave as shown in Figure 4A, the horizontal scanning speed of the electron beam on the CRT surface, in other words, the moving speed of the spot is constant, so Even if the object is located near both the left and right edges of the screen, it will appear wider than when it is near the center. Therefore, if a modified sawtooth wave as shown in FIG. 4C is used as a horizontal scanning signal, the moving speed of the spot on the cathode ray tube surface will be high at the center and low near the edges.

Therefore, the moving distance of the spot on the cathode ray tube corresponding to the same rotation angle of the plane mirror is made uniform over the entire screen, and the above-mentioned image distortion can therefore be prevented.
Figure 5 shows the temporal relationship between the signal waveforms appearing in each part of the circuit shown in Figure 2 and the movement of the rotating plane mirror.I represents the rotation of the plane mirror, and only this graph is vertical. The axis is not voltage but rotation angle. The square wave is a signal appearing at the terminal 15a, and serves as a synchronization signal for driving the plane mirror. The waveform is a square wave with a repetition frequency twice that of the square wave, and the waveform is a square wave with a repetition frequency equal to the square wave but with a slightly lower impulse ratio. This square wave is used as a blanking signal to determine the display period of the screen on the cathode ray tube. A sawtooth wave is a linear sawtooth wave that starts at the same time as the square wave rises, and is shown in waveform A in Figure 4.
Nothing but. Similarly, the waveform corresponds to sine wave B in FIG. To generate each of the above-mentioned waveforms, for example, first generate a square wave, divide the frequency to create a square wave, generate a blanking signal and a sawtooth wave based on the square wave, and generate a fundamental wave from the square wave. All you have to do is extract it and get a sine wave.

Another method is to first oscillate a sine wave using a crystal oscillator or the like, shape the waveform to obtain a square wave, and then obtain the waveform and V from the square wave in the same manner as described above. For convenience, the case where the detector is a single element has been explained above, but even when using a detector in which a large number of detecting elements are arranged in a straight line, optical scanning is performed by reciprocating rotation of the reflecting mirror as in the embodiment. The present invention can be applied in the same way.

In the explanations so far, a plane mirror has been used as the optical deflector for the convenience of understanding, but of course there is no essential difference in image distortion when using a concave mirror or a convex mirror. No special consideration is required compared to when a plane mirror is used.

The same applies when a prism or the like is used instead of a reflecting mirror. Furthermore, when using the linear multi-element detector described above, scanning in the direction of the array line of the elements is performed using a charge transfer element, etc., and scanning in the direction perpendicular to this is performed optically; When scanning both horizontally and vertically using a single reflecting mirror, distortion of the image occurs in the vertical direction, but in such a case, as shown in Figure 4C, as in the embodiment. It is sufficient to use a similar waveform as the vertical scanning signal, and the period of the sawtooth wave is simply once or twice per frame (in the case of interlaced scanning).

However, in this case, the density of the scanning lines becomes non-uniform, resulting in
This causes non-uniformity in the brightness of the displayed image.

That is, the brightness is high in areas where the density of scanning lines is high, and the opposite is true in areas where the density of scanning lines is low. To prevent this inconvenience, a correction alternating current signal may be superimposed on the direct current component added to the video signal. This AC signal may be a sine wave having the same frequency as the sine wave in FIG. 5, but it is necessary to shift the phase by π/2 radians (1/4 period) with respect to the sine wave. In other words, a cosine wave is used as the brightness correction alternating current signal. However, since the observer is generally not very sensitive to the brightness at the edges of the reproduced image, the brightness correction AC signal does not need to have a correct cosine waveform.
The video device according to the present invention as described above can obtain high-quality images without distortion without using a torsion bar by simply devising an electronic circuit, so it can completely avoid troubles associated with the use of a torsion bar. This has the advantage that the optical scanning mechanism can be made simple and inexpensive.

Therefore, it is extremely advantageous to apply it to an infrared imaging device or the like that performs optical scanning by reciprocating rotation of an optical deflector.

[Brief explanation of the drawing]

FIG. 1 is a simplified system diagram showing the configuration of a conventional infrared imaging device, FIG. 2 is a simplified system diagram of an embodiment of the imaging device according to the present invention, and FIG. 3 is a diagram of the horizontal scanning signal generation circuit shown in the previous figure. Figure 4 is a block diagram showing the configuration, Figure 4 is a diagram showing the waveforms of signals appearing in the main parts of the circuit shown in Figure 3, and Figure 5 is a diagram showing the waveforms of signals appearing in the main parts of the circuit in Figure 2 and the plane mirror. FIG. 3 is a diagram for explaining the relationship with rotational motion. 1: object surface, 2: convex lens, 3: infrared detector, 4: plane mirror, 6: cathode ray tube, 7 retortion bar.

Claims (1)

[Claims] 1. An optical scanning system that performs optical scanning with an optical deflector that rotates back and forth so that the speed gradually increases in the first half of rotation in the scanning direction and gradually decreases in the second half, and the optical scanning system In an imaging device having a photoelectric conversion system that receives an image of light after passing through the system and generates an electrical signal, and a cathode ray tube for display, the slope is the steepest in the middle between the start point and end point of each scan. , an imaging device that corrects distortion of a displayed image due to speed fluctuations of the optical deflector by applying a signal whose slope gradually becomes gentler as it moves away from the center as a scanning signal to the cathode ray tube. . 2. The video device according to claim 1, wherein the scanning signal is obtained by combining a sawtooth wave and a sine wave. 3. The video device according to claim 1 or 2, further comprising a luminance correction means for lowering the DC level of the video signal in a portion with a high scanning line density than in a portion with a low scanning line density. .