JPH04177985A - Video camera - Google Patents

Abstract

PURPOSE:To obtain a video picture with high sensitivity by outputting a picture picked up by an image pickup element repetitively after pickup under a specific condition or interpolating and synthesizing plural pictures and outputting an output video signal without changing the field rate of the output signal. CONSTITUTION:Let a field rate of an output video signal be (a) (fields/sec), a field rate picked up actually be (b) (fields/sec), and a shutter speed be (c) (1/sec), then an object is picked up by an image pickup element through an image pickup lens under the condition of a slower field rate than an output video signal (b<a) and of a shutter speed (c>1/a). Then a picked-up picture is repetitively outputted from the image pickup element or plural pictures are interpolated and synthesized and the video signal is outputted without changing the field rate (a) of the output video signal. Thus, the sensitivity against the object at a dark place is improved and each picked-up picture is subject to picture processing with a weight to send the video image of the dark object as the video picture in real time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is particularly applicable to image pickup tubes such as video cameras and broadcast cameras;
The present invention relates to a video camera equipped with an image sensor.

[Conventional technology] Conventional video cameras are not good at photographing dark subjects, and when photographing dark subjects, a method is used to electrically amplify the video signal in order to increase the light receiving sensitivity. Ta.

[Problem to be solved by the invention] When photographing a dark subject in a situation where the illuminance exceeds the limit, if a method is used to electrically amplify the video signal in order to increase sensitivity, noise will also be amplified. The disadvantage was that the signal-to-noise ratio deteriorated and the image quality deteriorated.

This invention was made in order to solve this problem, and is a video camera that can obtain high-sensitivity video images without any serious deterioration even for subjects in dark places below the shooting illuminance limit. The purpose is to provide

[Means for solving the problem] In order to achieve the above object, the field rate of the output video signal is set to a (field/sec),
When actually photographing, the field rate is b (field/sec), and the shutter speed is C (1/sec).
), the image is shot through the imaging lens onto the image sensor at a field rate slower than the output video signal (b<a) and under the shutter speed c > 1/a, and then imaged onto the image sensor. This method repeatedly outputs a captured image, or performs interpolation synthesis from a plurality of images, and outputs the output video signal without changing the field rate a.

[Function] According to the present invention, sensitivity can be increased even for subjects in dark places, and images of dark subjects can be added to video images in real time by adding weight to each carrier image and performing image processing. It is possible to send

[Example] FIG. 1 is a schematic diagram showing a first example of the present invention. In this embodiment, an NTSC signal is taken as an example of the output video signal, and its field rate is 60 (fields/sec) and the shutter speed is approximately 1/sec.
It is 60 seconds or less.

In FIG. 1, A to C are switches, 1 is a CCD (charge coupled device), 2 is an amplifier that amplifies the image signal from the CCD 1, 3 is a sample and hold circuit,
4 is an A/D converter, which converts an analog signal into a digital signal. 5.6 is field memory, CCD
It has a capacity to record the output from the image sensor I, and can be switched by switch A. The interpolation circuit 7 uses the weight table 8 to store the field memory 5.
This circuit performs interpolation by weighting the information from 6. 9
1 is a video signal synthesis circuit, and 10 is a controller for timing the operation of each of the above-mentioned elements and circuits.

FIG. 2 shows an image field and an actual video image field when the image generated by the imaging lens is photographed by the imaging element at a field rate slower than the output video signal and at a shutter speed slower than 1/60 seconds in this embodiment. 2 is a timing chart illustrating the relationship.

In Figure 2, (A) lowers the field rate to 20 fields/sec and lowers the shutter speed to 1/sec.
11 and 12 are odd and even fields, respectively. The horizontal axis shows time; odd field image R11, even field image R12, odd field image R13. 1/2 in the order of
At every 0 sec, images are taken with the shutter speed slower than 1/60 sec. (B) is for a video image, and the field rate is 60 fields/sec
It shows the standard of 13 and 14 correspond to odd and even fields in the video image, respectively. The video images are arranged in the order of R21, R2□, . still,
Images in fields with parentheses like (R2,) are those obtained by image interpolation synthesis.

FIG. 3 is a diagram simply showing an example of the image interpolation synthesis. α represents an image at time t1, β represents an image at time t3, and γ represents an image at time t2 obtained by interpolating and combining α and β with a certain weight. Also, X+,
N2. N3 indicates a spatially identical point, and the image density at that spatially identical point in each image is expressed as N, , N2 . N3
shall be.

When image interpolation synthesis is performed, the screen density N3 at the spatially identical point X3 at time t2 is xl, and the density N at the point x2 is
,, The time intervals a and b are used as weights to determine an appropriate value for N2 as shown in equation (3) below.

(bN+ +aNz)/(a+b)=N3 (3
) Note that this is just an example, and interpolation and synthesis may be performed using another method. Therefore, in FIG. 2, the image information at R11 in (A) is sent to R21 to R2g in (B) with different weights corresponding to the densities to be interpolated and synthesized as described above. Furthermore, R
23 is the information of the image of R1+ itself, and R24 shows the image obtained by performing interpolation synthesis of the images of RI l and R1□. As shown in the timing chart in Figure 2, the image sensor captures an image at a field rate slower than the output video signal and at a shutter speed slower than 1/60 seconds (R41, R1□, R13), and processes the image. Video image output field rate (R20,
R2□,...).

The operating principle will be explained with reference to FIGS. 1 and 2. First, CCD1
The image from the imaging lens is captured at a frame rate slower than the output video signal and at a shutter speed slower than 1/60 second. The image is designated as R12. R12 is amplifier 2
, sample-and-hold circuit 3, and AD converter 4, and are stored in field memory 5 by switch A. The field memory 6 stores the image R that was captured one time ago.
II is memorized. By operating switches B and C using the controller 10, the images in the field memories 5 and 6 are 7.
The images are entered into an interpolation circuit, and each image is weighted and synthesized using a weight table 8 so that appropriate image interpolation and synthesis can be performed, and a video signal synthesis circuit 9 generates an image for one field of a video image. The video image (R25) is also synthesized by the interpolation circuit with different weights from those of the field memories 5.6 to (R24). Switch B is closed for video image R26, and switch C directly takes out the image from field memory 5 and makes it correspond to video image R26. After photographing R1□, the next image R13 is photographed at a slow shutter speed, and this time it is recorded in the field memory 6 using switch A. Thereafter, following the same procedure as for R1□, (R24), (R25), (R26) , . . . fields corresponding to the video image are synthesized.

The above is an example of capturing an image from a CCD 1, which is an image sensor, at 20 fields/sec. In addition, it is also possible to configure the video images entirely by image processing.

In FIG. 4, <C) and (D) respectively show the case of imaging at a field rate of 30 fields/sec and the case of an actual video image. 15 and 16 indicate odd and even fields in the image sensor, respectively, and the images at that time are R31, R3□, . . . .

17 and 18 are fields corresponding to odd and even fields in a video image, and the image is R41.
, R42... Video image (R43) is R31
, R3□, weights are added to each image, and the images are interpolated and synthesized. The field R44 next to (R4,) has R
The image of 3□ is taken directly, and the next field after R44 (R4g) is obtained by adding weights to the images of R3□ and R33 and combining them by interpolation.

By repeating this operation in the same way, the field rate of the video image is returned to the video image while interpolating and synthesizing the images from the image pickup device.

As is clear from the above examples, it is possible to capture images by selecting the optimal field rate and shutter speed for various conditions of dark objects, and it is also possible to capture images of dark objects in various conditions, such as when the illuminance of a dark object changes continuously. Even in such a case, imaging can be performed by making continuous selections in the same way.

FIG. 5 is a diagram showing an example in which all images from an image sensor are converted into video images by image processing.

(E) and (F) correspond to the case of shooting with a field rate slower than the output video signal and the shutter speed slower than 1/60 seconds, and the case of an actual video image, respectively, and the former (
In E), 19.20 are odd and even fields, respectively, and R51 and R5□ are their images. 21 and 22 in the latter (F) correspond to odd and even fields of the video image, respectively, and (R, , ) and (R, □) indicate the images. The image R52 captured at a shutter speed slower than 1/60 seconds is appropriately weighted together with the previously captured image R5, and the images are interpolated and combined to form a video image (R, 3).
becomes. The next video image (R,4) is R51 and R
By changing the ratio of weights added to 5□, images are interpolated and synthesized again to obtain (R64).

(R,5) is also given by combining R52 and the next image R53. Thereafter, a video image is created by interpolating and synthesizing all the photographed images in the same manner.

In FIGS. 1 to 5 below, the field rate of the video image is restored by interpolating and synthesizing images taken at a slower field rate and slower shutter speed than the output video signal. Two images are used when performing image interpolation synthesis, but this can also be achieved with three or more images.

FIG. 6 is a diagram showing a second embodiment of the present invention. This embodiment will also be explained using an NTSC signal as an example of the output video signal.

In Fig. 6, (G) and (H) correspond to the case of shooting at a field rate slower than the output video signal and a shutter speed slower than 1/60 seconds, and the case of an actual video image, respectively; the former In (G), 23.24 corresponds to the odd and even fields, R7+, R72, etc. indicate the images, and 25.26 in the latter (H) corresponds to the odd and even fields of the video image, R81, R8□・・
shows the image. Image R7+ is directly equivalent to 4 fields of video image, and the next image R7□ is also Ra
Fill in below s. The conversion ratio of this frame can be selected depending on the current situation, and may also be changed continuously.

As shown in the embodiment of FIG. 6, since images are taken at a shutter speed slower than 1/60 seconds, the sensitivity is increased and it becomes easy to obtain intermittent images even for dark subjects. Furthermore, in this embodiment, it is also possible to directly convert the video images without performing image processing, or to add image interpolation and synthesis as shown in FIG. This makes it possible to obtain an intermittent image that is not completely intermittent or slightly smooth as in the example shown in FIG. 6 even for a dark subject.

It has been described above that by using this embodiment, intermittent images can be obtained for dark subjects, but it is not limited to dark subjects, and by combining it with daylight photography (AE), it can be used in normal bright situations. But it can also be used.

[Effects of the Invention] As proven above, according to the present invention, sensitivity can be increased even for dark subjects, and by adding weight to each captured image and performing image processing, dark subjects can be captured in video images in real time. It is possible to send images of

Furthermore, when a video camera is equipped with a wide converter or the like, the shooting conditions for dark subjects are quite poor (although the present invention can be used to widen the range of usage conditions).

By increasing the sensitivity, it is also possible to darken the F number in the entire zoom range. Darkening the F number also has the advantage of reducing the diameter of the front element of the lens (
Ru. Furthermore, if the sensitivity is made variable for zooming (shutter speed variable), even if the amount of light is insufficient during zooming, it is possible to obtain a sufficient amount of light by increasing the sensitivity.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a first embodiment of the present invention, and Fig. 2 is a schematic diagram showing a first embodiment of the present invention. A timing chart explaining the relationship between the image field and the actual video image field when shooting at a slower shutter speed, Figure 3 is a diagram that briefly shows an example of image interpolation synthesis, and Figure 4 is the captured image. FIG. 5 is a timing chart showing the relationship between the image sensor and the video image; FIG. 5 is a diagram showing an example in which all images from the image sensor are converted into video images by image processing; FIG. The figure shown in FIG. 7 is a timing chart showing the relationship between the captured image and the video image. In the figure. 1: CCD 2: Amplifier 3: Sample and hold circuit 4: A/D converter 5.6: Field memory 7: Interpolation circuit 8: Weight table 9: Video signal synthesis circuit 10: Controller representative Patent attorney 1) Takashi Kita Sunny Figure 2 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] Set the field rate of the output video signal to a(field/
sec), the field rate during actual shooting is b(field/sec), and the shutter speed is c(1/sec).
sec), a field rate slower than the output video signal (b<a) is transmitted through the imaging lens and onto the imaging device.
, and the shutter speed is c>1/a, and then the captured images are repeatedly output on the image sensor, or the field rate of the output video signal is adjusted by interpolating and synthesizing multiple images. A video camera characterized by outputting without changing a.