JPH04287009A - Automatic focusing camera - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus camera equipped with a line of sight detection device.

0002

2. Description of the Related Art Conventionally, as a means for measuring distance by dividing the photographic screen, for example, Japanese Patent Laid-Open No. 60-262004 is known. In addition, as a means for detecting the line of sight of the photographer observing the finder, Japanese Patent Application Laid-Open No. 1-241511
Publications such as Japanese Patent Application Laid-open No. 2-5 are known. Furthermore, Japanese Patent Application Laid-Open No. 2-63040 is known as means for selecting a distance measurement area from gaze position information.

0003

[Problems to be Solved by the Invention] However, since conventional autofocus cameras use distance measurement values that use the entire range of the range, it is difficult for the photographer to truly focus within the range. It is difficult to accurately focus on the subject. Therefore, a method has also been proposed in which the screen or a part thereof is divided into a plurality of parts and the focus position is calculated from the results of distance measurement at each position. In this case, possible methods include adopting the distance measurement result of the closest focal point from among multiple distance measurement results, or adopting the distance measurement result of a place where the contrast of the output of the photoelectric conversion element for distance measurement is high. However, it is not always the case that the subject intended by the photographer will be in focus. Therefore, a method of detecting the photographer's gaze point and employing the distance measurement results of the distance measurement area corresponding to this point may be considered. However, in this case as well, there is a problem in that accurate focusing is difficult when the photographer's intention is to focus on multiple subjects, or as a result, to focus on a subject with depth. .

The present invention has been made in view of the above-mentioned conventional problems, and its object is to provide an autofocus camera that can better reproduce the photographer's focusing intention.

[0005]

[Means for Solving the Problems] In order to solve such problems, the autofocus camera according to the present invention uses the point-of-gaze position information obtained by the line-of-sight detecting device to obtain the information from the distance measuring device corresponding to the point of interest. By weighting the distance measurement results according to the aperture of the photographing lens, the focus position can be adjusted in accordance with the photographer's intention.

[0006]

[Operation] In the present invention, since the focal position of the photographic lens is determined according to the aperture of the photographic lens and the distance measurement result observed by the photographer, the photographer's intention can be more accurately reproduced even when the subject is deep. Automatic focus adjustment is possible.

[0007]

Embodiments Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of an autofocus camera according to the present invention. In the same figure, 1
0 is a control device consisting of a CPU, 11 is a line-of-sight detection device that detects the gaze point in the screen by gazing at the subject that the photographer intends to focus on, and 12 is a device that divides the screen into multiple parts and then divides them. 13 is a photographic lens; 13 is a photographic lens;
Reference numeral 14 denotes a photographic lens drive device that moves the focal position of the photographic lens 13 to a predetermined position according to instructions from the control device 10, and 15 denotes a photographic lens diaphragm that narrows down the aperture of the photographic lens 13 to a predetermined aperture according to instructions from the control device 10. control device, 1
Reference numeral 6 indicates a storage device for storing the threshold value necessary for control and the divided distance measurement results, and 17 indicates a storage device for storing the threshold value necessary for control, and a storage device 17 for storing the divided distance measurement results. It is a warning device to notify the
This warning device 17 may be, for example, installed with a buzzer to notify the user with a sound, or may be provided with an LED display in the viewfinder. Reference numeral 18 denotes an input signal generating device, and this input signal generating device 18 is used when the photographer gazes at the subject he or she wants to focus on, and by activating this input signal generating device 18, the position information of the gaze point is fixed, and the control device 10 It is assumed that this gaze point position information can be captured. This input signal generating device 18 can be easily constructed using, for example, a push button.

FIG. 2 is a perspective view illustrating the configuration of the distance measuring device shown in FIG. In the figure, 21 is a photographing lens, 22 is a field mask for limiting unnecessary light flux to the distance measuring device 12, and 23 is for correcting the spectral sensitivity of the photoelectric conversion element 24 incorporated in the distance measuring device 12. This is an infrared absorption filter. Reference numeral 24 denotes a photoelectric conversion element that re-images the subject image using a re-imaging lens 25, and a CCD is used for this photoelectric conversion element 24 so that the luminance distribution of this re-image formation can be detected. In this case, the photoelectric conversion element 24a has a reimaging lens 2.
The subject image is re-imaged by 5a. Further, a subject image is similarly formed on the photoelectric conversion element 24b by the re-imaging lens 25b. The images on the re-imaging lenses 25a and 25b correspond to the subject image passing through the opening on the long side of the field mask 22. Similarly, the object image passing through the opening on the short side of the field mask 22 is re-imaged onto the photoelectric conversion elements 24c, 24d by re-imaging lenses 25c, 25d. 25 (2
5a, 25b, 25c, 25d) are re-imaging lenses, 26
is an aperture mask installed in front of the re-imaging lens 25 to restrict unnecessary light beams from entering the photoelectric conversion element 24, and this aperture mask 26 is installed in front of the re-imaging lens 25a.
, 25b, 25c, and 25d.
, 26b, 26c, and 26d are provided. 27 is a correction lens, and this correction lens 27 has an aperture mask aperture 26a,
Conjugate images 21a, 21b, 21 of 26b, 26c, 26d
The photographing lens 21 is arranged so as to form an image of the lenses c and 21d.
Avoiding the restriction of the luminous flux by the exit pupil.

FIG. 3 shows an example of a distance measurement area divided within a screen using the distance measurement device shown in FIG. In this example, a cross-shaped distance measurement area is arranged in the center of the photographic screen 31, but it may be arranged separately into a plurality of distance measurement areas. Further, in this example, the distance measurement area is divided into 11 parts in the long side direction of the screen and 7 parts in the short side direction, but the number of divisions is not limited to this.

In FIG. 4, for the sake of simplicity, only the distance measurement area in the long side direction of FIG. 3 will be taken up and the number of divisions will be reduced to eight. FIG. 4(a) shows the divided range-finding areas and the subject image superimposed on the range-finding areas. Figure 4(b)
FIG. 4A shows the distance measurement area corresponding to FIG. 4A on the horizontal axis and the distance measurement value on the vertical axis, and schematically shows how the distance measurement result changes depending on the depth of the subject. FIG. 4C shows a gaze point that the photographer intends to focus on, superimposed on the distance measurement area. The photographer gazes at the subject he or she wants to focus on, and operates the input signal generator 18 for fixing the positional information of the gaze point. At this time, a distance measurement value is calculated based on the gaze point position detected by a known line of sight detection device and the corresponding divided distance measurement area. By repeating the above operations, a plurality of pieces of gaze point position information and corresponding distance measurement values can be calculated. In this example, two positions are detected, but more positions may be detected. FIG. 4(d) shows only two distance values corresponding to the gaze point position extracted from the eight distance values shown in FIG. 4(b). As described above, more distance measurement values may be extracted depending on the point of interest. In this figure as well, the vertical axis represents the measured distance value, and the region r between the two dashed lines is the range that requires good resolution. Figure 4(e) is for comparing the area r that requires good resolution obtained from Figure 4(d) and the size of the good resolution range, so-called depth of focus, which varies depending on the brightness of the aperture of the photographing lens. FIG. The double-headed arrows represent the range of depth of focus that varies depending on the aperture. A narrower depth of focus range corresponds to a brighter aperture. The white circle is the center of the depth, and you can assume that the film surface is at this position. As shown in (a) of FIG. 4(e), if the depth of focus is deeper than the region r where the photographer requires resolution, good resolution can be obtained in the range of the region r. In this case, the focal position of the photographic lens is determined according to the average value of the measured distance values corresponding to the gaze point (the photographic lens is driven so that the average value of the measured distance values becomes 0). However, if the depth of focus is shallow compared to area r as shown in (d) in Figure 4(e), sufficient resolution cannot be given to the intended subject, so it is better to warn the photographer to that effect. good. This warning allows the photographer to take measures such as narrowing down the aperture or adjusting the position of the subject. Furthermore, even in such a case, it is preferable to focus the photographing lens so that sufficient resolution can be obtained at least at one point. Therefore, in the example of (d) in FIG. 4(e), the concept of giving priority to the closest object is uniformly adopted, and the focus of the photographing lens is set to the closest object. Figure 4(e) mentioned above
), the focal position of the photographic lens is determined depending on the aperture determined by the photographer or automatically determined by the camera, that is, depending on the depth of focus. take measures. As a specific example, (
Consider the following processing, including a) and (d). Determine the absolute value ratio from the depth of focus D (F) obtained from a predetermined aperture F and the closest distance measurement result Lne and the closest distance measurement result Lin among the multiple distance measurement results obtained from the line of sight detection device. H=
Calculate Abs{(Lin-Lne)/D(F)} (
Abs here means absolute value). If this absolute value ratio H
If is sufficiently smaller than 1, for example, if H≦H1=0.5, the focal position difference between a plurality of subjects can be ignored, so the distance measurement value Lt for controlling the photographic lens may be the arithmetic mean of Lne+Lin. That is, Lt=W1×Lne+W2×Lin, where the weighting coefficients W1=0.5 and W2=0.5. If the absolute value ratio H>H2=1, resolution cannot be obtained for all the subjects intended by the photographer. In this case, priority is given to the closest subject, which has been proposed in the past. In other words, the weighting coefficient W1 is brought closer to 1, and the weighting coefficient W2 is
=1-W1. At this time, as described above, it is also possible to provide a means for notifying the photographer by display or sound warning that not all of the subjects intended by the photographer can be resolved. Although the switching points H1 and H2 of the absolute value ratio H are set to 1 and 0.5 here, they are not limited to this and may be set to further appropriate values. Also, between these switching points, that is, between H1≦H<H2, W1 can be set to 0.5 as shown in FIG. 5(a), 1 as shown in FIG. 5(b), or W1 as shown in FIG. 5(c) It is also possible to use an increasing function like . Threshold values H1, H2 and weighting coefficients W1, W used here
Depth of focus D (F) determined by 2 and lens aperture F
may be stored in the storage device 16. From the above measures, as shown in (a), (b), (c), and (e) in Figure 4(e), as the depth of focus becomes shallower (the measured distance value for determining the focal position of the photographic lens ) is weighted more closely.

FIG. 6 is a diagram showing an automatic focusing algorithm. In the same figure, the process starts at step 601 (hereinafter abbreviated as S601), and in S602, it is determined whether automatic focus adjustment is to be performed using the position information of the point of interest or automatic focus adjustment that does not use the position information of the point of view. This selection can be set in advance using a switch installed on the camera body. Here, if the gaze point position information is not used, it is omitted. S60
In step 3, the line of sight detection device is activated to calculate the position of the gaze point. In step S604, it is determined whether the input signal generating device 18 has instructed to fix the gaze point position information (hereinafter referred to as locking). If it is not locked, the routine moves to a more urgent routine other than this one. If locked, S
In 605, the distance measurement value of the corresponding area is calculated. In S606, the locked number counter is incremented by one. This is called the number of locks. In S607, it is determined whether the number of locks is 1, and if it is 1, there is no need to weight it according to the aperture of the photographic lens, so the process moves to a routine that adjusts the focal position of the photographic lens according to the distance measurement value obtained in S605. . If the number of locks is plural, the process moves to S608, a routine in which a weighted distance measurement value according to the aperture is calculated and the focus position of the photographing lens is adjusted. Although the initialization of the number of locks and gaze point position information used in S606 is not particularly clarified,
Initialization may be performed by a release, or an initialization input device such as a push button may be provided instead of a release in consideration of usability for continuous shooting. Of course, the number of locks and the gaze point position information must be initialized when the camera is powered on.

Next, a flowchart for calculating the weighted distance measurement value in S608 is shown in FIG. 7 based on the embodiment of FIG. 5(c). In the same figure, the depth of focus D (F) according to the brightness of the aperture F of the photographic lens controlled in S701 is set in advance by CP.
Reference from the table recorded in U. Alternatively, the depth of focus D(F) may be determined by multiplying the F number of the aperture F by a predetermined value. In S702, among the distance measurement values corresponding to the gaze point position information, the closest distance measurement value Lne and the distance measurement value closer to infinity are set as Lin. In S703, the absolute value ratio H=Abs{(L
in-Lne)/D(F)}. In S704, the magnitude relationship between the absolute value H and the threshold values H1 and H2 is compared, and depending on the result, the process branches to S705, S706, and S707. In S705, S706, and S707, weighting coefficients W1 and W2 are determined. In S708, the weighting coefficient W1
, W2 to calculate the weighted distance measurement value L.

[0013]

[Effects of the Invention] As explained above, according to the present invention, an extremely excellent effect is achieved in that focus adjustment can be easily performed taking into account the depth of focus that varies depending on the aperture, by gazing at the subject to be focused on. can get.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of an autofocus camera according to the present invention.

FIG. 2 is a perspective view showing the configuration of a distance measuring device.

FIG. 3 is a diagram showing distance measurement areas within the screen.

FIG. 4 is a diagram illustrating a process of calculating a distance value corresponding to a gaze point.

FIG. 5 is a diagram showing a weighting function of distance measurement values depending on the depth of focus.

FIG. 6 shows a flowchart of an autofocus camera according to the present invention.

FIG. 7 is a diagram showing a flowchart illustrating weighting of measured distance values.

[Explanation of symbols]

10 Control device 11 Line of sight detection device 12 Distance measuring device 13 Photography lens 14 Lens drive device 15 Lens aperture control device 16 Storage device 17 Warning device 18 Input signal generator

Claims (3)

[Claims] 1. Distance measuring means capable of measuring distance by dividing the photographing screen, lens driving means driving the photographing lens to a predetermined focal position, and line of sight detection detecting the position of the photographer's gaze point in the finder. 1. An autofocus camera, comprising: means and information processing means for determining a focal position of a photographing lens from information on positions of two or more points of gaze. 2. The autofocus camera according to claim 1, further comprising a focus position determining means for determining the focal position of the photographing lens depending on the depth of focus from aperture information of the photographing lens. 3. The automatic camera according to claim 1, further comprising a warning means for warning the photographer when the object corresponding to the point of gaze cannot be brought into focus with a predetermined aperture of the photographing lens. focus camera.