JP2002365710A - Focus display device - Google Patents

Abstract

(57) [Summary] [Problem] By displaying focus information indicating a focus state on a viewfinder of a camera, a cameraman can accurately grasp a focus position while accurately adjusting a focus by manual focus or the like. Provided is a focus display device capable of performing adjustment. An image pickup device for picking up an image for recording is provided with two image pickup devices having different optical path lengths, and subject light incident on the image pickup device is divided into these image pickup devices. And make it incident. Then, the imaging devices B and C
From the video signal from the camera, and based on the magnitude relationship of these focus evaluation values, the focus state is set to the front focus,
It detects whether the camera is in focus or in focus, and displays the result on the viewfinder 12 as focus information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus display device, and more particularly to a focus display device for displaying a focus state of a photographing lens on a viewfinder or the like of a camera.

[0002]

2. Description of the Related Art Conventionally, when a photographer manually adjusts the focus of a photographic lens for a television camera by manually focusing, he or she mainly checks the image on a small monitor called a viewfinder attached to the camera. ing.

[0003]

However, since the viewfinder is small, it is difficult to check the focus state in detail, and out-of-focus is sometimes observed when the viewfinder is checked on a large monitor. This is particularly noticeable in high-definition televisions with high image resolution.

For this reason, the cameraman has a problem that the focus cannot be checked not only with a small viewfinder image but also with sufficient focus adjustment unless other focus checking means are used together.

[0005] The present invention has been made in view of such circumstances, and when performing focus adjustment by manual focus or the like, the focus can be adjusted with high accuracy while the photographer accurately grasps the in-focus position. It is an object to provide a display device.

[0006]

In order to achieve the above object, according to the present invention, the focus of a photographing lens is set to a front focus and a rear focus with respect to an imaging surface of an imaging means of a camera. Focus state detecting means for detecting which of the focus states of focusing or focusing, based on the focus state detected by the focus state detecting means, the focus of the photographic lens is any of front focus, rear focus or focus Focus information display means for displaying focus information so as to be able to grasp whether the object is in focus,
It is characterized by having.

[0007] The invention described in claim 2 is the first invention.
Wherein the focus information display means displays the focus information on a viewfinder of a camera.

[0008] The invention described in claim 3 is the first invention.
In the invention described in the above, the focus state detecting means captures the subject light incident on the imaging lens by a plurality of imaging means having different optical path lengths, based on a high frequency component of an image signal captured by each imaging means. The method is characterized in that a focus evaluation value is acquired, and the focus state is detected based on the magnitude relation of the acquired focus evaluation values.

[0009] The invention described in claim 4 is the invention according to claim 3.
In the invention described in (1), at least one of the plurality of image pickup units also serves as an image pickup unit for picking up a video image.

According to the present invention, the focus information is displayed on, for example, a view finder or the like so that the focus of the photographing lens can be determined to be in a front focus state, a rear focus state, or an in-focus state. At the time of focusing or the like, highly accurate focus adjustment can be performed while accurately grasping the in-focus position based on the focus information.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a focus display device according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing a configuration of a focus display device according to the present invention. The focus display device shown in FIG. 1 is, for example, an image pickup device (two-dimensional CCD) A (built-in image pickup device mounted on a normal camera) which is built in a television camera and captures an image for video output from the camera to the outside. element)
In addition, an image sensor (two-dimensional CCD) for focus state detection
B and an image sensor (two-dimensional CCD) C are provided.
These image sensors A, B, and C are arranged so as to image the subject light that has passed through the photographing lens mounted on the television camera at different optical path length positions.

FIG. 2 shows the configuration of an optical system in which the image pickup devices A, B, and C are arranged. As shown in FIG. 2, the subject light that has passed through the photographing lens is split by the first prism P1, and One object light reflected by the prism P1 is
The light enters the imaging surface of the imaging device C. The other object light that has passed through the first prism P1 is then split at the boundary between the second prism P2 and the third prism P3, and one object light reflected at this boundary is incident on the image sensor B. . Then, the subject light that has passed through the first prism P1, the second prism P2, and the third prism P3 enters the image sensor A. Note that the subject light incident on the imaging device B and the imaging device C is split at the same ratio with respect to the amount of the subject light incident on the first prism P1 through the photographing lens. On the other hand, if the amount of the subject light incident on the imaging device B and the imaging device C is large, the amount of the subject light incident on the imaging device A decreases, and the image for video originally required becomes dark. It is preferable that the light amount of the subject light incident on the imaging device B and the imaging device C is as small as possible with respect to the light amount of the subject light incident on A.

When the optical paths (optical axes of the respective image sensors) of the object light incident on the image sensors A, B, and C are shown on the same straight line, as shown in FIG. The optical path length of the image sensor C is shortest, and the optical path length of the image sensor A is intermediate between the optical path lengths of the image sensors B and C. That is, the image pickup surfaces of the image pickup device B and the image pickup device C are arranged in parallel at the same distance before and after the image pickup surface of the image pickup device A. It should be noted that the subject light is transmitted to the image sensor A,
The configuration of the optical system for dividing into B and C is not limited to the configuration using the prism as shown in FIG.

As shown in FIG. 1, an image signal of a subject imaged by the image sensor A is converted into a video signal of a predetermined format by a camera circuit (not shown), and the video signal is output to the outside of the camera as a video. , Mixer 1
Viewfinder 12 installed on the camera through the camera
Is output to As a result, the image captured by the image sensor A is displayed on the viewfinder 12 or the like.

On the other hand, the image signals of the subject imaged by the image pickup device B and the image pickup device C are converted into video signals of a predetermined format by a signal processing circuit (not shown), and then the sharpness (image contrast) of each image is changed. It is converted into the signal of the focus evaluation value shown. Note that the video signals obtained from the imaging device B and the imaging device C do not need to have the same format as the video signal obtained from the imaging device A. A circuit for deriving a focus evaluation value signal based on a video signal obtained from the image sensor B will be described. A video signal obtained from the image sensor B is first input to a high-pass filter (HPF) 14, and the high-pass filter 14 outputs A band frequency component is extracted. H
The high frequency component signal extracted by the PF 14 is converted into a digital signal by the A / D converter 16. And
After only the digital signal corresponding to the pixel in the predetermined focus area (for example, the center of the screen) of the digital signal for one screen (one field) is extracted by the gate circuit 18, the digital signal in the extracted range is extracted. The signal values are added by the adder 20. Thus, the sum of the values of the high frequency components of the video signal in the focus area is obtained. The value obtained by the adder 20 is given to the CPU 30 as a signal of a focus evaluation value indicating the level of sharpness of the image in the focus area.

Similarly, based on the video signal obtained from the image pickup device C, a focus evaluation value signal is generated by the HPF 22, the A / D converter 24, the gate circuit 26, and the adder 28, and the focus evaluation value signal is generated. Is given to the CPU 30. It should be noted that various synchronization signals are given from the synchronization signal generation circuit 32 shown in FIG. 3 to the respective circuits such as the image pickup devices A, B, and C, and the gate circuits 18 and 26 so that the processing of each circuit is synchronized. I have. In addition, the synchronization signal generation circuit 32 sends the CPU 30
Is provided with a vertical synchronization signal (V signal) for each field of the video signal.

The CPU 30 comprises an image sensor B and an image sensor C
Based on the focus evaluation value signal obtained from the above, it is detected whether the current focus of the photographing lens is in the front focus state, the rear focus state, or the in-focus state. Then, focus information indicating the focus state is output to the mixer 10 and the image sensor A
Superimposed on the video signal from the
To be displayed.

FIG. 4 shows the focus position of the photographic lens on the horizontal axis, that is, the focus adjustment position by a focus ring or the like,
FIG. 5 is a diagram showing the state of the focus evaluation value with respect to the focus position when a certain subject is photographed, with the focus evaluation value taken on the vertical axis. A curve a shown by a solid line in the drawing indicates a focus evaluation value with respect to a focus position of the photographing lens when it is assumed that a focus evaluation value is obtained based on a video signal obtained from the image sensor A. The curves b and c show the focus evaluation values obtained from the imaging devices B and C, respectively, as described above.

In FIG. 2, the focus position F3 at which the focus evaluation value of the curve a is maximum (maximum) is the focus position, but the focus position (focus adjustment position) of the photographing lens is now at the position of F1 in the figure. It is assumed that it is set. At this time, the focus evaluation value obtained from the imaging device B is a value corresponding to the focus position F1 by the curve b, and the imaging device C
Is a value corresponding to the focus position F1 by the curve c, it can be seen that the focus evaluation value obtained from the imaging device B is larger than the focus evaluation value obtained from the imaging device C. That is, when the focus position of the photographing lens is set closer to the focus position F3 which is the focus position, the focus evaluation value obtained from the imaging device B is larger than the focus evaluation value obtained from the imaging device C. In this state, the focus of the photographing lens is in the state of the front focus.

On the other hand, it is assumed that the focus position of the photographing lens is set to the position F2 in the figure. In this case, it can be seen that the focus evaluation value obtained from the imaging device C is larger than the focus evaluation value obtained from the imaging device B. That is,
When the focus position of the photographing lens is set at infinity from the focus position F3, which is the focus position, the focus evaluation value obtained from the image sensor C is larger than the focus evaluation value obtained from the image sensor B, In this state, the focus of the photographing lens is in the back focus state.

When the focus position (focus adjustment position) of the photographing lens is set to the in-focus position of F3 in the figure, that is, when the focus of the photographing lens is in focus,
It can be seen that the focus evaluation values obtained from each of the imaging device B and the imaging device C are equal.

From the above, the CPU 30 compares the focus evaluation value obtained from the imaging device B with the focus evaluation value obtained from the imaging device C, and the focus evaluation value obtained from the imaging device B is If the focus evaluation value obtained from the image pickup device C is larger than the focus evaluation value, the focus of the photographing lens is determined to be the state of the front focus. Conversely, when the focus evaluation value obtained from the image sensor C is larger than the focus evaluation value obtained from the image sensor B, the focus of the photographing lens is determined to be in the back focus state. On the other hand, when the focus evaluation value obtained from the image sensor B is equal to the focus evaluation value obtained from the image sensor C, the focus of the photographing lens is determined to be in focus.

Then, the focus information indicating the focus state is displayed on the viewfinder 12 so that the cameraman can grasp the focus state determined as described above.
FIG. 5, FIG. 6, and FIG. 7 are diagrams showing display examples of focus information. FIG. 5 is an example in which the focus state is displayed by a mark “∞” indicating infinity, a mark “N” indicating close proximity, and arrows “←” and “→”.
(A) shows “N” when the focus state is the previous focus.
And an arrow “←” indicating the direction of “∞” from
The mark “∞” flashes to indicate that the focus position is in the direction of infinity. With this front focus display, the cameraman can know that the focus state is the front focus, and easily understand that the focus can be achieved by moving the focus of the taking lens toward infinity. be able to. FIG. 5B shows an arrow “→” indicating the direction from “∞” to “N” when the focus state is the back focus, and blinks the “N” mark to indicate that the in-focus position is infinite. It suggests that you are in a distant direction. This rear focus display allows the cameraman to know that the focus state is rear focus, and also easily understands that focusing can be achieved by moving the focus of the taking lens in a close direction. Can be. FIG. 5C shows a display in the case where the focus state is in focus, and suggests that focus has been achieved by eliminating the display of the arrow between “∞” and “N”. . This focus display allows the cameraman to know that the focus state is in focus.

FIG. 6 shows the focus state by marks “N” and “∞” as well as FIG. 5, and shows “F” indicating the front pin, “R” indicating the rear pin, and just focus. This is an example in which the focus state is displayed by a mark “J” and arrows “←” and “→”. When the description of the same display portion as in FIG. 5 is omitted, FIG. 6A displays an arrow “←” indicating the direction from “F” to “J” when the focus state is the front focus, and “ By flashing the mark “F”, it is suggested that the front focus is set. FIG. 6B shows an arrow “→” indicating the direction from “R” to “J” and blinks the “R” mark when the focus state is the back focus.
This suggests that it is a back focus. FIG. 6 (C)
Is the display when the focus state is in focus, the display of the arrow between "F" and "J", and the arrow between "R" and "J" disappear, and the mark of "J" blinks This suggests that the camera is in focus.

On the other hand, FIG. 7 shows a mark “∞” indicating infinity, a mark “N” indicating close proximity, a mark “○” indicating a focus position displayed at the center of a semicircle, and This is an example in which the focus state is displayed by a mark “○” displayed at a position deviated from the center on a semicircle. FIG.
(A) indicates that the focus position is in the direction of infinity by displaying “○” near “∞” on the semicircle when the focus state is the front focus, and FIG. 7
(B) indicates that the in-focus position is in the closest direction by displaying “○” near “N” on the semicircle when the focus state is the back focus. FIG.
(C) indicates that focus is achieved by displaying only the mark “○” indicating the focus position at the center of the semicircle. With such a display, the cameraman can grasp whether the focus state is the front focus state, the rear focus state, or the in-focus state, as in the case of FIG. It is possible to easily grasp which direction of infinity or close-up can be achieved for focusing.

FIG. 8 is a flowchart showing the processing procedure of the CPU 30. First, the CPU 30 performs required initial settings (step S10), and then performs image sensor A,
It is determined whether or not a synchronization signal synchronized with the vertical synchronization signal (V signal) of the video signal output from B and C is provided from the synchronization signal generation circuit 32 (step S12). YES
When it is determined that the focus evaluation value obtained from the image sensor B is read from the adder 20 (see FIG. 1) (step S14), the focus evaluation value obtained from the image sensor C is added to the adder 28 (see FIG. 1). ) (Step S1)
6).

Next, the CPU 30 determines whether or not the focus evaluation value obtained from the image pickup device B is equal to the focus evaluation value obtained from the image pickup device C (step S18). If Y
When it is determined to be ES, since the focus state of the taking lens is in focus as described above, FIGS. 5 (C), 6 (C),
Alternatively, focus display indicating focus is performed on the viewfinder 12 as shown in FIG. 7C (step S20).

On the other hand, if NO is determined in the step S18, it is next determined whether or not the focus evaluation value obtained from the image sensor B is larger than the focus evaluation value obtained from the image sensor C ( Step S22). If it is determined as YES, the focus state of the photographing lens is the front focus as described above, and therefore, FIG. 5 (A), FIG. 6 (A), or
As shown in FIG. 7A, a front focus display indicating a front focus is performed on the viewfinder 12 (step S24). Step S
If NO is determined in step S22, the focus state of the photographing lens is the back focus state, and therefore, FIG.
(B) Or, as shown in FIG. 7B, a back focus display indicating a back focus is performed on the viewfinder 12 (step S2).
6).

When the above processing is completed, step S
Returning to step 12, the processing of detecting the focus state and displaying the focus state is repeatedly executed.

As described above, in the above-described embodiment, the imaging devices B and C for detecting the focus state are specially provided in addition to the imaging device A for photographing a video image. If it is also used as an image sensor for detection, only one special image sensor for focus state detection may be used. For example, in FIG. 1, a case where the focus state is detected by the image sensor A and the image sensor B without providing the image sensor C will be described. First, a focus evaluation value is obtained from a video signal obtained by the image sensor A. Circuit to perform
F14, A / D converter 16, gate circuit 18, adder 2
0, so that the focus evaluation value can be input to the CPU 30. Then, the focus evaluation value obtained from the image sensor A and the focus evaluation value obtained from the image sensor B are compared in the same manner as described above. Is determined and the in-focus display is performed. In this case, accurately, focusing can be obtained at an intermediate position between the imaging surface of the imaging device A and the imaging surface of the imaging device B. However, if the distance between the imaging surface of the imaging device A and the imaging surface of the imaging device B is small, The imaging surface of the imaging device A can be set within the range of the depth of focus, and there is no problem even if the video signal obtained by the imaging device A is used for video. On the other hand, when the focus evaluation value obtained from the image sensor B is larger than the focus evaluation value obtained from the image sensor A, it is determined to be the front focus, and the front focus display is performed as described above. Conversely, if the focus evaluation value obtained from the image sensor A is larger than the focus evaluation value obtained from the image sensor B, it is determined that the focus is on the back, and the back focus is displayed in the same manner as described above.

In the above embodiment, the focus information is displayed on the viewfinder 12. However, the present invention is not limited to this, and the focus information may be displayed on a display other than the viewfinder 12. A dedicated display for displaying information may be provided. The display control of the display in this case is performed by the CPU in the same manner as in the above embodiment.
30 can be done. As an example in which a special display is provided, for example, as shown in FIGS. 9 and 10, it is preferable to provide displays 42 and 48 for displaying focus information on the frame portion 40 of the viewfinder 12 because the cameraman can easily see the information. In the case of FIG. 9, in the frame portion 40 on the left side of the viewfinder 12, there is a vertically long display section 46 for displaying the horizontal bar 44, and if the display position of the horizontal bar 44 is at the center, the focus is indicated. If the position is shifted upward or downward, the front pin or the rear pin is indicated. Also, the larger the deviation from the center of the horizontal bar 44, the greater the amount of defocus. In the case of FIG. 10, in the frame portion 40 on the left side of the viewfinder 12, there are a plurality of lighting regions 50, 52, and 54 arranged in the vertical direction. When the upper and lower rectangular lighting areas 52 and 54 are lit, the front pin or the rear pin is indicated. As the lit area is farther from the center part as in the case of FIG.
This shows that the amount of defocus is also large.

The above-mentioned FIGS. 5, 6, 7, 9 and
The display example of the focus information in FIG. 10 is an example, and any method may be used as long as the focus state of the photographing lens can be grasped as a front focus, a rear focus, or an in-focus state. May be displayed.

In the above embodiment, the subject light immediately before entering the image pickup device A for video is divided, and the divided subject light is incident on the image pickup devices B and C for focus state detection. However, the position at which the subject light incident on the imaging devices B and C for focus state detection is divided is not limited to this. For example, when the present invention is applied to a camera that separates subject light into red, green, and blue color components by a color separation optical system and captures a video image with a video imaging element for each color, This is not limited to the case where the subject light for focus state detection is divided just before the subject light enters the predetermined image pickup device as in the embodiment, and the focus is adjusted before the subject light enters the color separation optical system. The subject light for state detection may be split.

[0035]

As described above, according to the focus display apparatus according to the present invention, the focus information is displayed, for example, in view so that the focus of the photographing lens can be grasped as front focus, rear focus, or in focus. Since the image is displayed on the viewfinder or the like, the cameraman can perform accurate focus adjustment while accurately grasping the focus position based on the focus information at the time of manual focus or the like.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a focus display device according to the present invention.

FIG. 2 is an image sensor that captures an image for video,
FIG. 2 is a diagram illustrating an embodiment of a configuration of an optical system in which an imaging element for detecting a focus state is arranged.

FIG. 3 illustrates image sensors A, B, and C when optical paths of subject light incident on image sensors A, B, and C are shown on the same straight line.
It is a figure showing the positional relationship of C.

FIG. 4 is a diagram illustrating a state of a focus evaluation value with respect to a focus position when a certain subject is photographed.

FIG. 5 is a diagram illustrating a display example of focus information.

FIG. 6 is a diagram illustrating a display example of focus information.

FIG. 7 is a diagram illustrating a display example of focus information;

FIG. 8 is a flowchart illustrating a processing procedure of a CPU;

FIG. 9 is a diagram illustrating a case where focus information is displayed in a portion other than a viewfinder;

FIG. 10 is a diagram illustrating a case where focus information is displayed in a portion other than a viewfinder;

[Explanation of symbols]

A, B, C: imaging device (CCD), 10: mixer, 1
2: Viewfinder, 14, 22: High-pass filter (HPF), 16, 24: A / D converter, 18, 26
... gate circuits, 20, 28 ... adders, 30 ... CPU

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/225 G02B 7/11 E 5/232 G03B 3/00 AZ (72) Inventor Masao Wada Tokyo 2-2-1 Jinnan, Shibuya-ku, Japan Broadcasting Corporation Broadcasting Center (72) Inventor Tetsuji Inoue 2-2-1 Jinnan, Shibuya-ku, Tokyo Japan Broadcasting Corporation Broadcasting Center (72) Inventor Ryoji Kumaki Tokyo 2-2-1 Jinnan, Shibuya-ku, Tokyo Japan Broadcasting Corporation Broadcasting Center (72) Inventor Shinobu Nakamura 2-2-1 Jinnan, Shibuya-ku, Tokyo Japan Broadcasting Corporation Broadcasting Center (72) Inventor Haruo Tominaga Tokyo 2-2-1 Jinnan, Shibuya-ku, Tokyo Japan Broadcasting Association Broadcasting Center (72) Inventor Hiroyuki Horiguchi 2-1-1 Jinnan, Shibuya-ku, Tokyo Japan Broadcasting Corporation Inside the Broadcasting Center (72) Inventor Hidekatsu Sugiura 2-2-1 Jinnan, Shibuya-ku, Tokyo Japan Broadcasting Corporation Inside the Broadcasting Center (72) Inventor Masayuki Sugawara 1-1-10 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Association F-term (Reference) in the Broadcasting Research Laboratory 2H011 AA03 BA38 BB03 DA05 2H051 AA08 BA47 BA54 CB04 CB26 CB29 CE14 GA03 GA09 GA14 2H102 AA34 CA34 5C022 AB21 AB44 AC12 AC42

Claims (4)

[Claims] A focus state detecting means for detecting whether the focus of the taking lens is in a front focus state, a rear focus state, or an in-focus state with respect to an imaging surface of the imaging means of the camera; Focus information display means for displaying focus information based on the detected focus state so as to be able to grasp whether the focus of the taking lens is a front focus state, a rear focus state, or an in-focus state. Focus display device. 2. The focus display device according to claim 1, wherein said focus information display means displays said focus information on a viewfinder of a camera. 3. The focus state detecting means captures subject light incident on a photographic lens by a plurality of image capturing means having different optical path lengths, and focuses on the basis of a high frequency component of an image signal captured by each image capturing means. 2. The focus display device according to claim 1, wherein an evaluation value is obtained, and the focus state is detected based on a magnitude relationship between the obtained focus evaluation values. 4. The focus display apparatus according to claim 3, wherein at least one of said plurality of image pickup means also serves as an image pickup means for picking up a video image.