JPS63990B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an imaging method in which a moving object is turned into a still image by a shutter, and the image is captured by a two-dimensional imaging device having an accumulation effect to obtain an imaging signal with little deterioration in image quality.

Generally, when a moving object is imaged with an image pickup tube such as a vidicon or a two-dimensional image pickup device having an accumulation effect such as a solid-state image pickup camera, image quality deterioration such as image blur occurs in an image reproduced from an image pickup signal. That is, an imaging device having an accumulation effect has a period corresponding to the vertical scanning period,
For example, the optical information incident through the imaging lens is accumulated on the target surface, and the accumulated optical information is read out in the next scan, so if the object moves within the accumulation time, the amount of movement is This will cause image blur. To give a specific example, when a pattern with a diameter of 0.5 mm moving at 0.5 m per second within the imaging field of view is imaged by a normal television camera with a vertical scanning period of 16.7 ms, the accumulation time mentioned above is:
Since it is 16.7ms, the pattern is 8.3 within this time.
mm, and this amount of movement becomes the amount of image blur, resulting in an image blur that is 17 times the pattern diameter.

Furthermore, although there is no problem with solid-state imaging cameras, with ordinary television cameras that use image pickup tubes, the optical information of a certain field remains for 5 to 8 fields, as shown in the signal survival rate characteristic diagram in Figure 1. Due to this afterimage, the previous screen information is superimposed on the predetermined screen information, causing image quality deterioration.

In this way, apart from solid-state imaging cameras with extremely low resolution, in solid-state imaging cameras with normal resolution or normal television cameras, one scanning period is finite and slow, and in the image pickup tube there is an afterimage. For example, when a moving object is imaged with these imaging devices and the image signal obtained is processed to measure the pattern of the object, if the image is captured using the normal imaging method, the image of the image signal as described above is The blur made pattern measurement difficult.

Therefore, in this kind of pattern measurement department,
Conventionally, a method has been adopted in which a moving object is momentarily illuminated at a predetermined timing with a flash discharge lamp such as a strobe light source, and a moving image is captured as a still image. However, this imaging method using flash discharge lamps has the disadvantage that the light emission wavelength of the flash discharge lamp is limited and the light source becomes close to a point light source, which reduces the degree of freedom of illumination, and places significant restrictions on the object to be imaged. Since the lifespan of flash discharge lamps is relatively short, ranging from 100,000 to 1 million times, the running costs of the system are high, and they also have disadvantages such as the generation of ozone and flash light, which can be unpleasant for workers.

In order to further improve the shortcomings of flash discharge lamps, a method has been proposed in which a moving object is captured as a still image using a shutter.
In general, this conventional method opens and closes the shutter in synchronization with each vertical scan of the imaging device and constantly captures images, resulting in image quality deterioration due to afterimages.Also, it is necessary because the movement of the object and the exposure timing are asynchronous. However, it has the disadvantage that it is not possible to image a moving object at an optimal imaging position.

The present invention has improved such conventional drawbacks, and its purpose is to always stop a moving object at an optimal imaging position using a shutter, and to obtain an imaging signal with less deterioration in image quality such as image blur. . Examples will be described in detail below.

FIG. 2 is a block diagram of the imaging method of the present invention, which is applied to the observation section of a pattern recognition device, in which 1 is a television camera, 2 is a moving object, 3 is an illuminator, 4 is a position detection circuit, 5 is an external synchronization signal generation circuit, 6 is a shutter control circuit,
7 is a shutter drive circuit, 8 is a signal selection circuit, 9 is a pattern recognition circuit, 11 is an imaging lens, 12 is an imaging tube, 13 is a shutter mechanism, 14 is an imaging surface, 15
is a pulse motor, 16 is its rotating shaft, 17
is the shutter blade, and a to g are signals of each part.

As shown in the figure, the present invention includes an imaging lens 11,
A normal television camera having an image pickup tube 12, a horizontal/vertical polarization system, a video amplification system, etc. (not shown),
A shutter mechanism 13 is added to configure a television camera 1 with a shutter, and the television camera 1 is constantly scanned with the shutter closed while the moving object 2 is not within a predetermined imaging field of view. 2 arrives within the imaging field of view, the shutter is opened at a predetermined timing to be described later, and the image of the moving object 2 is instantaneously exposed by the normal illuminator 3 onto the imaging surface 14 of the imaging tube 12, and one field immediately after this exposure is This image pickup signal is used, for example, for pattern measurement in this case.

In this embodiment, the above-mentioned shutter mechanism 13 includes a pulse motor 15 as shown in the figure, and a black opaque shutter blade having a shape as shown in FIG. 17, and the relationship between the pulse motor 15, the shutter blade 17, and the imaging tube 12 is such that the window 31 provided on one circumference of the shutter blade 17 passes in front of the imaging surface 14 of the imaging tube 12. It is determined. Therefore, when the pulse motor 15 rotates by a predetermined angle in response to a drive signal to be described later, the shutter blade 17 rotates, and the window 31 causes the image pickup surface 1 to be rotated.
Exposure is performed on the effective area of 4 for a predetermined time,
After exposure, the light blocking portion 32 other than the window 31 of the shutter blade 17 stops in front of the imaging surface 14 and operates to substantially block light. In addition, the third
In the figure, 33 is a hole into which the rotating shaft 16 is inserted, 34 is a hole for a mounting screw, and 35 is a hollow portion.

The exposure time of the shutter mechanism 13 can be set to be sufficiently shorter than one vertical scanning period (for example, 16.7 ms) of the television camera 1 depending on the rotation speed of the pulse motor 15, etc., so that the image of the moving object 2 is It is accumulated on the imaging surface 14 in a short time, and an imaging signal with less image blur can be obtained. In addition, the shutter is opened and closed during the main scanning of the TV camera 1.
In other words, by performing the main scanning during the vertical blanking period, the image of the moving object is uniformly accumulated on the imaging surface and main scanning is performed, so that the top or bottom of the obtained image is not cut off and the image is uniform and A stable imaging signal can be obtained. Furthermore, since the television camera 1 always scans with the shutter closed while the moving object 2 is not present at the predetermined imaging position, this scanning eliminates the afterimage of the previous field and slight leakage from the closed shutter. Unnecessary images caused by light are completely erased, and the next time the exposure is performed, image quality deterioration due to afterimages will not occur as in the conventional method.

In order to operate the television camera 1 in this manner, a position detection circuit 4, an external synchronization signal generation circuit 5, a shutter control circuit 6, a shutter drive circuit 7, and a signal selection circuit 8 are provided in this embodiment. .

The external synchronization signal generation circuit 5 is entirely composed of logic circuits except for the output level conversion section, and generates various synchronization signals a necessary for the television camera 1 and outputs them to the television camera 1, so that the television camera 1 can be connected to the television camera 1 as described above. It is always operated at a predetermined scanning cycle,
On the other hand, the horizontal synchronizing signal and the signal selection circuit 8 shown in FIG.
It outputs a vertical synchronizing signal b as shown in FIG. 1, and also outputs a vertical blanking signal c as shown in FIG.

The position detection circuit 4 detects the period during which the moving object 2 exists within the imaging field of view of the television camera 1. For example, as shown in FIG. A light emitter 53 and a light receiver 54 are arranged to sandwich the path of the object 2 for detection. For example, as shown in FIG. 4C, a position detection signal d which becomes "0" only during the period when the moving object 2 exists within a predetermined imaging field of view is output to the shutter control circuit 6. In FIG. 5, 55 is the imaging area of the television camera 1, arrow 56 is the horizontal scanning direction, arrow 57 is the vertical scanning direction, 58 is the shutter opening, and arrow 59 is the moving direction.

Further, the shutter control circuit 6 receives the position detection signal d and the vertical blanking signal c, and processes them logically so that immediately after the position detection signal c becomes "0", as shown in FIG. For example, the vertical blanking signal of FIG. E
A shutter control signal f consisting of a plurality of pulses as shown in FIG. The shutter operation is performed at the timing shown in FIG. The shutter drive circuit 7 faithfully amplifies the power of the shutter control signal f from the shutter control circuit 6 to the extent that the pulse motor 15 can operate, and is composed of, for example, a switching transistor and a DC power supply.

Further, the signal selection circuit 8 selects an imaging signal of one field period immediately after exposure from among the output signals constantly outputted from the television camera 1 and outputs it to the pattern recognition circuit 9 in the subsequent stage, and the signal selection circuit 8 selects the imaging signal for one field period immediately after exposure from among the output signals constantly outputted from the television camera 1 and outputs it to the pattern recognition circuit 9 in the subsequent stage. The shutter opening signal e of No. 6 and the horizontal and vertical synchronization signals b of the external synchronization signal generation circuit 5 are input, and based on these signals, the shutter opening signal e as shown in FIG.
A gate signal indicating a field period is formed, and the image signal g from the television camera 1 is sampled and output using this gate signal. The reason why the imaging signal of the first field immediately after exposure is used in this way is that the shutter is closed after exposure, and most of the accumulated information is lost due to the beam scanning of the first field, as shown in Figure 1. ,2
This is because the scanning signals after the field are attenuated and cannot be used. In this signal selection, in addition to outputting the entire imaging signal of one field immediately after exposure to the pattern recognition circuit, it is also possible to output the image by partially removing the left, right, top, and bottom edges of the screen, for example.

With such a circuit configuration, the television camera 1 can be operated as described above, a moving object can always be stopped at an optimal imaging position by the shutter, and an imaging signal with less deterioration in image quality such as image blur can be obtained. .

It has been confirmed through experiments that there is the following relationship between the exposure time of the shutter mechanism 13 and the image quality deterioration of the image signal. In other words, if the exposure time Tsc is within the range that satisfies the following relational expression: Tsc≦minimum required pattern dimension/travel speed (1), image quality deterioration will not substantially occur, and if it is outside this range, it will be extremely Deterioration of image quality occurs. In other words, if the amount by which the target pattern moves within the shutter opening time, that is, the amount of image blur, is within the minimum pattern dimension, image quality deterioration will not substantially occur. The shutter mechanism 13 is adjusted so that the exposure time Tsc satisfies equation (1).
The results of an experiment using the response method using a common picture tube to compare the resolution of this method and the resolution of a conventional imaging method that does not use a shutter when imaging a moving object moving at 0.5 m per second within the imaging field of view. is shown in Figure 6. As shown in the figure, while the conventional imaging method has extremely poor resolution as shown by a curve 61, the imaging method of the present invention has a resolution that is almost the same as the resolution of the imaging signal at rest, as shown by a dotted line 62. The characteristics shown in curve 63 were obtained.

Although the above description has been made of a television camera that uses an image pickup tube with an afterimage phenomenon among two-dimensional imaging devices that have an accumulation effect, it goes without saying that this method can also be applied to solid-state imaging cameras. .

As explained above, in the present invention, a position detection circuit detects that a moving object has arrived at a proper imaging position, and a shutter control and drive circuit opens and closes the shutter within a vertical blanking period immediately after the detection, so that the imaging surface is 1 immediately after this exposure.
Since the field imaging signal is selected by the signal selection circuit and output to the outside, it is possible to always image a moving object at the optimal imaging position, and to obtain an imaging signal with less image blur. Since the image pickup device is scanned with the shutter closed while the camera is not in use, there is an advantage that image quality deterioration due to afterimages is also eliminated. Furthermore, the shutter mechanism composed of a shutter member and a pulse motor has the advantage of being less likely to break down and having excellent durability. Therefore, the present invention can be applied not only to the field of pattern measurement, but also to other fields where image signals are recorded on a videotape or the like and the reproduced image is used to analyze, for example, the motion status of a moving object, or to a television camera mounted on a moving object. It is very effective if you do.

[Brief explanation of the drawing]

Fig. 1 is a signal survival rate characteristic diagram, Fig. 2 is a block diagram of the imaging system of the present invention, Fig. 3 is an explanatory diagram of the structure of the shutter blade, Fig. 4 is an operation waveform diagram of Fig. 2,
FIG. 5 is an explanatory diagram of the position detection method, and FIG. 6 is an explanatory diagram of the resolution of the effect of the present invention. 1 is a television camera, 2 is a moving object, 3 is an illuminator, 4 is a position detection circuit, 5 is a peripheral synchronization signal generation circuit, 6 is a shutter control circuit, 7 is a shutter drive circuit, 8 is a signal selection circuit, 9 is a pattern recognition circuit,
11 is an imaging lens, 12 is an imaging tube, 13 is a shutter mechanism, 14 is an imaging surface, 15 is a pulse motor, 1
7 is a shutter blade.

Claims (1)

[Scope of Claims] 1. In a method of imaging a moving object with a two-dimensional imaging device having an accumulation effect and equipped with a shutter mechanism, the shutter mechanism includes a shutter member having an opening and a shielding part, and the shutter member. and a pulse motor that rotates the moving object, and is controlled by a position detection circuit for the moving object, a detection signal from the position detection circuit, and a vertical blanking signal applied to the two-dimensional imaging device, and drives the pulse motor to open and close the shutter. A shutter control drive circuit for operating the shutter control drive circuit, and a signal selection circuit for selecting an imaging signal of one field immediately after exposure of the two-dimensional imaging device by the shutter control drive circuit, and the shutter control drive circuit for controlling the two-dimensional imaging device when the shutter is closed. After the position detection circuit detects that the moving object has reached a predetermined imaging position, the shutter control drive circuit opens and closes the shutter of the shutter mechanism within a predetermined vertical blanking period. An imaging method characterized in that an image of the moving object is exposed on the two-dimensional imaging device after the operation is completed, and an imaging signal of one field immediately after the exposure is selected and outputted by the signal selection circuit. 2. The imaging method according to claim 1, wherein the shutter time of the shutter mechanism by the output control drive circuit satisfies the following: shutter time≦minimum dimension of pattern/velocity of moving object.