WO2002099495A1

WO2002099495A1 - Focus display unit

Info

Publication number: WO2002099495A1
Application number: PCT/JP2002/005436
Authority: WO
Inventors: Tadashi Sasaki; Masao Wada; Tetsuji Inoue; Ryoji Kumaki; Shinobu Nakamura; Haruo Tominaga; Hiroyuki Horiguchi; Hideaki Sugiura; Masayuki Sugawara
Original assignee: Fuji Photo Optical Co., Ltd.; Nippon Hoso Kyokai
Priority date: 2001-06-04
Filing date: 2002-06-03
Publication date: 2002-12-12
Also published as: JP2002365710A

Abstract

A focus display unit which displays a focus-status information on the camera’s view finder to enable the camera man to make a high-precision focus adjustment while allowing him to identify an accurate focusing position when a focus adjustment is made by manual focusing. Two image devices (B, C) having different light-path lengths are provided in addition to an image device (A) for picking up recording images, and light from an object of imaging to be shone onto the image device (A) is divided and beamed onto the image devices (B, C). Focal point evaluation values are obtained from video signals from the image devices (B, C), whether a focus status is in a front-focus, in a rear-focus or in sharp focus is detected based on the comparison between these evaluation values, and the result is displayed on a view finder (12) as focus information.

Description

Focus display device

The present invention relates to a focus display device, and more particularly to a focus display device that displays a focus state of a photographing lens on a viewfinder or the like of a camera. Background technology

Conventionally, when a photographer manually adjusts the focus of a shooting lens for a TV camera by manual focusing, he or she mainly checks the image on a small monitor called a viewfinder attached to the camera. Is going.

However, since the viewfinder is small, it is difficult to check the focus state in detail, and when it is checked on a large monitor, defocus may be observed. This is especially true for 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.

The present invention has been made in view of such circumstances, and when performing focus adjustment by manual focus or the like, a focus display device that enables a photographer to perform high-accuracy focus adjustment while accurately grasping the focus position. The purpose is to provide. Disclosure of the invention

In order to achieve the above object, a focus display device according to the present invention detects whether the focus of a taking lens is in a front focus state, a rear focus state, or an in-focus state with respect to an imaging surface of an imaging unit of a camera. The focus state of the photographing lens is selected from a front focus state, a rear focus state, and a focus state based on the focus state detected by the focus state detection means. And focus information display means for displaying focus information so as to be able to grasp the focus state.

Preferably, the focus information display means displays the focus information on a viewfinder of a camera.

Preferably, the focus state detecting means captures subject light incident on a photographic lens by a plurality of imaging means having different optical path lengths, and a focus evaluation value based on a high frequency component of an image signal captured by each imaging means. Is acquired, and the focus state is detected based on the magnitude relation of the acquired focus evaluation values.

Preferably, at least one of the plurality of imaging units also serves as an imaging unit for imaging a video image.

According to the present invention, the focus information is displayed on, for example, a viewfinder so that the focus of the photographing lens can be determined to be in the front focus state, the rear focus state, or the in-focus state. In such a case, it is possible to perform highly accurate focus adjustment while accurately grasping the in-focus position based on the focus information. BRIEF DESCRIPTION OF THE FIGURES

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

FIG. 2 is a diagram showing an embodiment of a configuration of an image pickup device that picks up an image for video and an optical system in which an image pickup device for focus state detection is arranged;

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

Fig. 4 is a diagram showing the state of the focus evaluation value with respect to the focus position when a certain subject is photographed;

Figures 5 (A), 5 (B), and 5 (C) show examples of display of focus information; FIGS. 6 (A), 6 (B), and 6 (C) show examples of focus information. 7 (A), 7 (B), 7 (C) are diagrams showing other display examples of focus information; FIG. 8 is a diagram showing a processing procedure of the CPU. The flow chart shown; Figure 9 is a diagram showing a case where the focus information is displayed in a portion other than the viewfinder;

FIG. 10 is a diagram showing a case where focus information is displayed in a portion other than the viewfinder. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of a focus display device according to the present invention will be described 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 the figure is, for example, an image sensor (two-dimensional CCD) A that is built into a television camera and captures an image for a video output from the camera to the outside. In addition to the imaging device, an imaging device (two-dimensional CCD) B and an imaging device (two-dimensional CCD) C for detecting a focus state 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 attached to the television camera at different optical path length positions.

Fig. 2 shows the configuration of the optical system in which the imaging elements A, B, and C are arranged. As shown in Fig. 2, the subject light that has passed through the taking lens is split by the first prism P1, and the first prism One object light reflected by P1 is incident on 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 taken by the image sensor B Is incident on. Then, the subject light that has passed through the first prism Pl, the second prism P2, and the third prism P3 enters the image sensor A. It should be noted 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 taking lens. On the other hand, if the amount of subject light incident on the image sensor B and the image sensor C is large, the amount of subject light incident on the image sensor A is small, and the originally required image for video becomes dark. It is preferable that the amount of subject light incident on the imaging device B and the imaging device C be as small as possible with respect to the amount of subject light incident on the imaging device A. You.

If the optical paths of the subject light incident on these image sensors A, B, and C (the optical axes of the respective image sensors) are shown on the same straight line, as shown in FIG. 3, the optical path length of image sensor B is the shortest. The optical path length of the element C is the longest, and the optical path length of the image sensor A is intermediate between the optical path lengths of the image elements 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. The configuration of the optical system that divides the subject light into the imaging elements A, 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 signal. The signal is output to Pew Finder 12 installed on the camera via 10. As a result, the image captured by the image sensor A is displayed on the viewfinder 112 or the like.

On the other hand, the image signals of the subject imaged by the image sensor B and the image sensor 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 converted. Is converted to a signal of a focus evaluation value indicating 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. The circuit for deriving the focus evaluation value signal based on the video signal obtained from the image sensor B will be described. First, the video signal obtained from the image sensor B is input to a high-pass filter (HPF) 14 and the video signal High frequency components are extracted. The high frequency component signal extracted by the HPF 14 is converted into a digital signal by the A / D converter 16. Then, only digital signals corresponding to pixels in a predetermined focus area (for example, the center of the screen) of the digital signals for one screen (one field) are extracted by the gate circuit 18 and then extracted. The values of the digital signals in the range are added by the adder 20. As a result, 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 used as a signal of the focus evaluation value indicating the degree of sharpness of the image in the focus area by the CPU 30. Given to.

Similarly, based on the video signal obtained from the image sensor C, the 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 is performed. The value signal is provided to CPU 30. Various synchronization signals are given from the synchronization signal generation circuit 32 shown in the figure to the imaging devices A, B, C, the gate circuits 18 and 26, and the like. Synchronization is achieved. In addition, a vertical synchronization signal (V signal) for each field of the video signal is supplied to the synchronization signal generation circuit 32 to the CPU 30.

The CPU 30 detects, based on the focus evaluation value signals obtained from the image pickup device B and the image pickup device C, whether the current focus of the imaging lens is in the front focus state, the rear focus state, or the in-focus state. I do. Then, focus information indicating the focus state is output to the mixer 10 and superimposed on the video signal from the image sensor A, and displayed on the viewfinder 12. Fig. 4 shows the focus position of the photographic lens on the horizontal axis, that is, the focus adjustment position using a focus ring, etc., and the vertical axis shows the focus evaluation value.The focus evaluation value for the focus position when an object is photographed is shown. FIG. The curve a shown by a solid line in the figure indicates the focus evaluation value with respect to the focus position of the imaging lens, assuming that the focus evaluation value was obtained based on the video signal obtained from the imaging device A, and the dotted line in the figure. Curves b and c shown by indicate the focus evaluation values obtained from the imaging devices B and C, respectively, as described above.

In the figure, the focus position F3 where 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 image sensor B is a value corresponding to the focus position F1 by the curve b, and the focus evaluation value obtained from the image sensor C corresponds 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 because the values are the values. That is, when the focus position of the taking lens is set closer to the focus position F3, which is the focus position, the focus evaluation value obtained from the image sensor B is higher than the focus evaluation value obtained from the image sensor C. In this state, the focus of the taking lens is It is in the state of.

On the other hand, it is assumed that the focus position of the taking 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. In other words, when the focus position of the taking 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 the focus evaluation value obtained from the image sensor B. In this state, which is larger than that, the focus of the taking lens is in a state of rear focus.

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

From the above, the CPU 30 compares the focus evaluation value obtained from the image sensor B with the focus evaluation value obtained from the image sensor C, and determines the power of the image sensor B and the obtained focus evaluation value. If is larger than the focus evaluation value obtained from the image sensor C, the focus of the photographing lens is determined to be the state of the previous pin. 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 photographer can grasp the focus state determined as described above. Figures 5 (A), 5 (B), 5 (C), Figures 6 (A), 6 (B), 6 (C), and Figures 7 (A), 7 (B), 7 (C) FIG. 5 is a diagram illustrating a display example of focus information.

Figures 5 (A), 5 (B), and 5 (C) show the focus with the “∞” mark indicating infinity, the “N” mark indicating close proximity, and the arrows “—”, “→”, etc. Fig. 5 (A) shows an example of displaying the status. In the case where the focus state is the front focus, an arrow "-" indicating the direction from "N" to "∞" is displayed and "∞ The flashing “” mark indicates that the in-focus position is at infinity. The front focus display allows the photographer to know that the focus state is the front focus and to set the focus of the photographic lens. It can be easily understood that focusing can be achieved by moving the waste in the direction of infinity. In Fig. 5 (B), when the focus state is the back focus, an arrow "-" indicating the direction from "∞" to "N" is displayed, the "N" mark flashes, and 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 photographic lens in the closest direction. can do. Fig. 5 (C) shows the display when the focus state is in focus, and suggests that the camera is in focus by eliminating the display of the arrow between "∞" and "N". You. With this in-focus display, the photographer can know that the focus state is in focus.

Figures 6 (A), 6 (B), and 6 (C) are in focus, as in Figures 5 (A), 5 (B), and 5 (C), by marking "N" and "∞". An example of displaying the front focus, “F” indicating the front pin, “R” indicating the rear pin, “J” indicating the just focus, and the focus status using arrows “—” and “→” It is. The description of the same display parts as in FIGS. 5 (A), 5 (B) and 5 (C) is omitted. In FIG. 6 (A), when the focus state is the front focus, “F” to “: An arrow “-” indicating the direction of U is displayed, and the “F” mark flashes to indicate that the pin is in front. Fig. 6 (B) shows an arrow “→” indicating the direction from “R” to “J” when the focus state is the back focus, and blinks the “R” mark to indicate the back focus. It is suggested that Fig. 6 (C) shows the display when the focus state is in focus, and the display of the arrows between "F" and "J" and the arrows between "R" and "J" disappear. The flashing “” mark indicates that the camera is in focus.

On the other hand, Fig. 7 (A), 7 (B) and 7 (C) show the mark of "∞" indicating infinity, the mark of "N" indicating close proximity, and the center of the semicircle. This is an example in which the focus state is displayed by an “o” mark indicating a focused position and an “o” mark displayed at a position deviated from the center on a semicircle. Fig. 7 (A) shows that the focus position is in the direction of infinity by displaying "o" near "∞" on the semicircle when the focus state is the front focus. Figure 7 (B) shows that when the focus state is the back focus, the focus position is shifted to the closest direction by displaying "o" near "N" on the semicircle. This suggests that there is. Figure 7 (C) suggests that the camera is in focus by displaying only the “o” mark that indicates the focus position at the center of the semicircle. With such a display, the cameraman can determine whether the focus state is the front focus, the rear focus, or the in-focus state, as in the case of Figs. 5 (A), 5 (B), and 5 (C). In addition, it is possible to easily grasp whether the focus of the photographing lens can be adjusted by moving the focus of the taking lens in infinity or in the closest direction.

FIG. 8 is a flowchart showing a processing procedure of the CPU 30. First, the CPU 30 makes necessary initial settings (step S10), and then generates a synchronization signal synchronized with a vertical synchronization signal (V signal) of a video signal output from the imaging elements A, B, and C by a synchronization signal generation circuit. It is determined whether or not it has been given from step 32 (step S12). If the determination is YES, the focus evaluation value obtained from the image sensor B is read from the adder 20 (see FIG. 1) (step S14), and the focus evaluation value obtained from the image sensor C is added to the adder 28 (step S14). (See Fig. 1) (step S16).

Next, the CPU 30 determines whether or not the focus evaluation value obtained from the image sensor B is equal to the focus evaluation value obtained from the image sensor C (step S18). If the determination is YES, the focus state of the taking lens is in focus as described above, and the view is adjusted as shown in Fig. 5 (C), Fig. 6 (C), or Fig. 7 (C). An in-focus display indicating in-focus is performed on the finder 12 (step S20).

On the other hand, if NO is determined in step S18, it is next determined whether the focus evaluation value obtained from the image sensor B is larger than the focus evaluation value obtained from the image sensor (step S18). S 22). If the determination is YES, the focus state of the taking lens is the front focus as described above, and the viewfinder is shown in Fig. 5 (A), Fig. 6 (A), or Fig. 7 (A). The front pin display indicating the front pin is performed at 12 (step S24). If NO is determined in step S22, the focus state of the photographing lens is the rear pin, and the viewfinder shown in FIG. 5 (B), FIG. 6 (B), or FIG. 7 (B) is used. A post-pin display indicating a rear-pin is displayed on the header 12 (step S26).

When the above process is completed, the process returns to step S12, and the processes of detecting the focus state and displaying the focus state are 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 capturing an image for video, but the imaging device A is used for detecting the focus state. If it is also used as the image sensor, only one special image sensor for detecting the focus state may be used. For example, in FIG. 1, the case where the focus state is detected by the image pickup device A and the image pickup device B without the image pickup device C will be described.First, a focus evaluation value is obtained from a video signal obtained by the image pickup device A. A circuit for acquiring the data is provided in the same way as the HPF 14, the A / D converter 16, the gate circuit 18, and the adder 20 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, and if the magnitudes of these focus evaluation values are equal, the focusing is performed. Is determined and the in-focus display is performed. In this case, precisely, focusing is obtained at an intermediate position between the imaging surface of the imaging device A and the imaging surface of the imaging device B, but the distance between the imaging surface of the imaging device A and the imaging surface of the imaging device B is short. For example, 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, if 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, when 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 focus information may be provided. The display control of the display in this case can be performed by the CPU 30 in the same manner as in the above embodiment. As an example of providing a special display, for example, as shown in Figs. 9 and 10, displays 42 and 48 that display focus information in the frame portion 40 of the viewfinder 12 are provided. It is preferable to place it because it is easy for a photographer to see. 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 displaying a horizontal bar 44, and if the display position of the horizontal bar 44 is at the center, Indicates focus, and if it is shifted up or down, indicates the front or rear focus. Also, the greater the deviation from the center of the horizontal bar 44, the greater the amount of defocus. In the case of FIG. 10, in the left frame portion 40 of the viewfinder 112, there are a plurality of lighting regions 50, 52, 54 arranged in the vertical direction, and a circular lighting region 5 in the center portion. When 0 is lit, it indicates in-focus, and when the upper and lower rectangular lighting areas 52, 54 are lit, it indicates the front focus or the rear focus. As in the case of FIG. 9, the farther the lit area is from the center, the greater the amount of defocus.

In addition, FIGS. 5 (A), 5 (B), 5 (C), FIGS. 6 (A), 6 (B), 6 (C), FIGS. 7 (A), 7 (B), 7 (C) ), The focus information display examples in Fig. 9 and Fig. 10 are merely examples, and any display mode that allows the user to know whether the focus of the taking lens is in the front focus state, the rear focus state, or the in-focus state. The focus information may be displayed in such a manner.

Further, in the above embodiment, the subject light immediately before entering the image pickup device A for video is divided, and the divided subject light enters the image pickup devices B and C for focus state detection. The position at which the subject light incident on the image sensors B and C for detecting the state 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 image sensor for each color. However, the present invention is not limited to the case where the subject light for focus state detection is divided just before the subject light enters the imaging element for a predetermined image as in the above embodiment, and the subject light enters the color separation optical system. Before the focusing, the subject light for focus state detection may be divided. Industrial applicability

As described above, according to the focus display device of the present invention, the focus information is provided to, for example, a viewfinder so that the focus of the photographing lens can be determined to be in a front focus state, a rear focus state, or a focus state. Is displayed, so the photographer can In this case, it is possible to perform high precision while accurately grasping the in-focus position based on the focus information.

Claims

The scope of the claims

1. Focus state detecting means for detecting whether the focus of the taking lens is in front of, behind, or out of focus with respect to the imaging surface of the imaging means of the camera;

Focus information display that displays focus information so that it is possible to grasp whether the focus of the photographing lens is a front focus, a rear focus, or an in-focus state based on the focus state detected by the focus state detection unit. Means,

A focus display device comprising:

2. The focus display device according to claim 1, wherein the focus information display means displays the focus information on a viewfinder of a camera.

3. The focus state detecting means captures the subject light incident on the photographic lens by a plurality of imaging means having different optical path lengths, and evaluates the focus based on the high frequency components of the image signals captured by each imaging means. 2. The focus display device according to claim 1, wherein a value is acquired, and the focus state is detected based on a magnitude relationship between the acquired focus evaluation values.

4. The focus display apparatus according to claim 3, wherein at least one of the plurality of imaging units also serves as an imaging unit for capturing a video image.