JPS6155620A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To improve the accuracy of range finding especially in a camera for photographing animation etc. by dividing a range finding area of a sensor as required, and finding the distance of a subject from respective area. CONSTITUTION:Signals from a sensor 19 are A/D converted 24, and picture elements are allotted to memories 41-43 in a gate 40. Hpfs of respective areas are calculated in arithmetic units 44-46, and a value k at which Hf makes zero crossing is found. When values of k obtained by arithmetic units 44-46 are k44-k46, circuits 47-49 calculate k44-k45, k44-k46, k45-k46 respectively. On the other hand, a depth calculating circuit 51 calculates the depth under the photographing condition as the width of the values k basing on information of aperture and information of focal distance of photographing lens system. A comparator circuit 50 compares ¦k44-k45¦, ¦k44-k46¦, ¦k45-k46¦ with the value k, and all are less than the value k, all of subject distances are judged to be within the depth of focus. On the other hand, information of distance k44-k46 is evened off 52, and necessary amount of shifting of a lens is calculated by an arithmetic circuit 57 from information of focal distance, etc. and a motor 27 is driven.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic focus adjustment device for use in photographing devices such as video cameras and still cameras, and in particular to an automatic fish point adjustment device that can select different distance measuring modes depending on the distance measuring object. It is related to.

2. Description of the Related Art Conventionally, various automatic focus detection devices are known that detect the distance of an object to be measured and display distance information after adjusting a photographic lens. For example, a device disclosed in US Pat. No. 4,185,191 that uses a photoelectric sensor to obtain ranging information is widely known, but it has the following problems.

(1) When the sensor cannot extract the contrast of the object to be measured under low brightness.

(No) When the object to be measured has a low contrast and the photoelectric sensor cannot extract its features.

(3) When the object to be ranged has the same contrast characteristics as the sensor repeats in the same direction as the longitudinal direction.

(4) When there are objects to be measured at different distances Pi11C within a photoelectric centimeter.

In such cases, conventional methods include determining that distance measurement is not possible and stopping the motor, or forcing the ice to move in one direction to find the focal point, or bringing it to a predetermined stopping position. However, it was difficult to say that the measures were sufficient, especially when shooting videos.

The present invention provides a means for stabilizing the unstable distance measurement operation in the shooting condition as described in the above-mentioned conventional example, and reflecting the shooting intention of the photographer to a certain extent, and as a result, making it possible to shoot a smooth and easy-to-see video. This is what we present.

Before explaining specific embodiments of the present invention, an optical layout diagram of an automatic focus adjustment device suitable for implementing an example of an automatic focus adjustment device to which the present invention can be applied is shown below. is a lens element, and 2 is a small lens group for re-forming the image of the pupil plane of the lens element. In this diagram, it is depicted as consisting of 2 small lenses, but in reality there are more than 20. Common. 5 to 6 indicate each pixel of a light receiving element made of a COD element, for example, pixels 3 and 4 correspond to the small lens 2-1, pixels 5 and 6 correspond to the small lens 2-2, and the pixel 6 corresponds to the small lens. The pixel 4 looks at the aperture part 8 through the lens 2-1, and the pixel 4 looks at the aperture part through the small lens 2-1. Similarly, pixel 5 looks at the aperture 8 portion through the small lens 2-2, and pixel 6 looks at the aperture portion through the small lens 2-2. As mentioned above, in reality, the small lenses and sensors are arranged in more than 20 rows counted as small lenses.If we assume that 2-1 is the n-th small lens and 2-2 is the n-19th small lens, then the explanation will be as follows. Therefore, the pixel that looks at aperture 8 through the nth lens is An, the pixel that looks at 7 is Bn, the pixel that looks at aperture 8 through the n-1st lens is An-1, and the pixel that looks at aperture A is Bn.
-1.

The F° plane is the focal plane of the lens. That is, assuming a video camera, the imaging surface position (equivalent position) of the imaging tube is 7.

Therefore, by changing the position of the lens 1 in the left-right direction, the distance to the object at which one plane (support) can be correctly imaged will vary, and if the image of an object at the focusing distance is captured as the output of the OCD array, An=Bn%An- , :Bn 1, whereas when capturing the image of an object that is not within the focusing distance, An=Bm,
It becomes n←m.

In FIG. 1, when distance R1 becomes the focusing distance of lens 1, the images of 9 points fall on pixels An and Bn (3, 4), and 10
The image of the point falls into the An-1t Bn-1 pixel (5,6).

Looking at it the other way, rays 11 and 12 intersect at point 10,
Rays 13'' and 14 intersect at point 9.

FIG. 2 is a diagram showing the output of the light-receiving element array explained with reference to FIG. 1, with the position of the light-receiving elements plotted on the horizontal axis. This figure shows a case where the positions of An and Bn are shifted by four pixels in the light receiving element, and if this shift is detected, out-of-focus can be detected.

FIG. 3 shows a block configuration diagram when the above automatic focus adjustment device is incorporated into an actual video camera. In the figure, 1 is a focus adjustment lens group called the front lens in the photographic lens system, and 15 is often composed of two groups, a variable power system and a correction system, which make the focal length of the photographic lens variable. 16 is a half prism, 17 is a total reflection lens group, 2-118 is an AF system lens group, and 19 is a sensor (L) that includes the small lens array and light receiving element array described in FIG. , 20 is an iris meter, 21 is an iris blade, 22 is an imaging system lens, 2
5 is a solid-state image pickup plate as an image sensor in this figure;
24 is a second converter which converts the signal obtained from the sensor into a digital signal; 25 is a cptr which makes judgments such as in-focus, out-of-focus, etc. based on this information and focal length information;
6 is a motor drive circuit, 27 is an AF motor for varying the position of lens group 1, 28 is an encoder for detecting position information of lens group 1, and 29 is for detecting focal length information of a photographing lens. It is an encoder device.

Various calculation means in the CPU 25 are known, but
For example, goods = ΣCIA(L-Bn's l l An+1-B
In-focus is determined when Hf calculated by n I ) is approximately zero.

Here, A in Fig. 2, force-V and Bnn curve deviation and direction,
To calculate (that is, the degree of defocus and the distinction between maepin and atopin), Hpf=Σ(l An+k ”B+11 1An+ +
+-nl), Hp is variable from k=-a to a.
Calculate f. Here, the value of a is determined by the number of small pins mentioned above.

Figure 4 shows the calculation results when the horizontal axis is k and the vertical axis is Hl)f, where 31 = 0 and Hpf =:
Therefore, it can be considered that the image is in focus in this state. On the other hand, in 30, k is negative, and in 32, k is positive, HI, and f is zero.The degree of υ blur is calculated based on the sign of k at this time, the front focus, the rear focus, and the absolute value of k. It depends on A, B and υ, but if k is negative, it will be a rear pin, then a result of 30 will be a rear pin, and a result of 32 will be a front pin.

Hereinafter, a case will be described in which an embodiment of the present invention is constructed using the above-mentioned automatic focus adjustment device in combination.

Figures 5 to 14 show the basic idea of the present invention and some
An example is shown below. Although this component, which is a feature of the present invention, can be achieved by the system configuration in cpσ25 shown in FIG. 5, its contents will be explained here mainly using a block configuration diagram and a flowchart.

Figures 5 and 6 show the arrangement of the photographing field of view for the distance measuring sensor used in the present invention, and Figure 5 shows the photographing screen size 35 of the conventional device and information for distance measurement within it. The exposed part shows a position 56 occupied by a distance measurement field where a so-called distance measurement sensor is arranged. The length of this distance measuring field of view is determined by the pitch of the small lenses 2 and the focal length of the multi-lens optical system 18, etc., as described in the description of the prior art example.

Figure 6 shows an example in which the distance measurement area 1, that is, the distance measurement field of view, is divided into n equal parts as shown in Figure 5, and distance measurement can be performed in each area, and the distance measurement area is divided into three parts. This is what is illustrated. That is, in this example, the conventional distance measurement field of view 36 is temporarily divided into Q=3 areas 37 to 39, and distance measurement information is extracted from each of the three areas as the distance measurement results.

As the number of divisions in the distance measurement field of view increases, distance information from multiple points can be obtained, but conversely, the accuracy of each distance measurement deteriorates. Therefore, no
The numerical value depends on the specs of the camera lens that uses this method and the way of thinking when designing it. In the following examples, n=
Example 3 will be described below.

FIG. 7 is a block diagram showing the first embodiment of the present invention. In the same figure, the sensor 19 is closer to the subject than p.
The constituent elements are the same as in FIG. 5 and are omitted. In the figure, a signal obtained from a sensor 19 is converted into a digital signal by an Aμ converter 24, and a gate 40 divides one pixel into five mesolis 41-43. If we count Senna's small lenses from the side and name them Rin 1-1624, they are A1-4 B.
are stored in the memory 41, /169 to 7F616 are stored in the memory 42, /1617 to 7524 are stored in the memory 43,
Hpf of each area is calculated by three computing units 44 to 460. If A61-I68 is at 57 in Figure 6, 9-16 is at 38, and 7617-7g624 is at 59.
If we calculate the pixel information at position 44, the calculation result at 44 is the distance information at position 37, and similarly, 45 is 38, and 46 is 39.
This will show the distance information of the position. Arithmetic units 44 to 46
Now, we are looking for k at which the above and < Hf cross zero. Conventionally, based on this k, the direction and amount of movement of the lens group in the photographic lens that is open to the focusing action is calculated immediately from the focal length of the photographic lens, and that lens is driven.
In the method shown in FIG. 7, the difference between the obtained distance information, for example k, is first determined by circuits 47-49. k obtained in 44-46
If t- is 44+, 45+ is 46, in circuit 47, it is 4
The circuit 48 calculates 45 for 4-, the circuit 49 calculates 4s for 44-, and the circuit 49 calculates 46 for -. On the other hand, depth calculation circuit 5
In step 1, the depth under the photographing situation is calculated as the width of k based on the aperture information obtained from an aperture υ meter (not shown) and the focal length information f of the photographing lens system obtained from an encoder or the like. Depending on the embodiment, comparison may be made with a representative width of k without performing depth calculation. Also, the depth referred to here can be freely set according to the design intention.

In the comparator circuit 50, 4s l is added to this k and l ksa -.
A comparison is made to l k44- with 4611 k4s-ka61. As a result l k44-4sl ll k
at- is 461 r l k4s- is all 461 or less, all of the subject distances in the three areas in the screen are determined to be within the depth of field, and conversely, if it exceeds k, all of the subject distances in the five areas are It is determined that there is a conflicting subject in terms of distance and distance that cannot be focused on. In this case, the warning circuit 55 issues a round warning.

There are various known warning methods (for example, lighting an LED in the viewfinder, sounding a buzzer, etc.).

On the other hand, the three distance information obtained by the Hpf calculation circuit are 44
+ k45 r k46 is averaged by the averaging circuit 52.

When 5w56 is connected, the arithmetic circuit 57 outputs focal length information F,
The required movement amount of the lens is calculated based on f, etc., and the motor is driven.

When the variation in the distance information of the same three ranges from 44 to 46 is outside the depth, a warning will be issued, but at that time, the lens control will be such that the 8w56 will be connected even if it is locked or even if the warning is issued. Alternatively, the purpose of dividing the distance measurement field of view described here may be used only for detecting near and far conflicts. In this case, the distance measuring operation is always performed in one normal zone.

FIG. 8 shows another embodiment using the Irf characteristic of the present invention, in which the field of view for distance measurement is divided into n. The feature of the embodiment shown in FIG. 8 is that the photographer can select any one of the two divided distance measurement fields according to his/her will, and the field of view setting for this purpose is set in block 58. Let's do it. This is achieved by an operation knob etc. provided on the outside of the camera.For example, as shown in figure M6, if the distance measurement field of view is divided into three and the left distance measurement field of view 37 is selected, the signal of that part, if the sensor is 1g when it consists of small lens groups from 7161 to A24.
Only the signals from i to 8 pass through the gate 40 and are stored in the memory 59.
will be stocked in

In addition to such division into n, the field of view setting means 58 can also designate arbitrary position lengths depending on the size of the subject.

FIG. 9 shows yet another embodiment using the n-division of the distance measuring field, which is another feature of the present invention. This method determines the lens stop position based on the calculation results.

In other words, in the case of competing subjects, the subject to be photographed is often located on the near side. (For example, consider when there is a person who is a subject in a landscape.) The memory 41, memory 42, and memory 43 contain data for the left, center, and right sides of the distance measurement field of view, as in the embodiment shown in FIG. Each of the three pieces of information is captured in a different color. The arithmetic circuits 44 to 46 calculate H, and the comparator circuits 62 and 63, which calculate the value of zero x 4, compare this value to 1 (g), and as a result of this, the closest object distance is calculated. is selected and transmitted to the arithmetic circuit 61.The arithmetic circuit 61 calculates the direction and amount of focus shift from the focal length information 54 as explained in the conventional example.The result is Mo-
The signal is transmitted to the drive circuit 26, and the motor 2 for driving the lens
7 is the one that drives it.

FIG. 10 shows another embodiment that includes the idea of using the depth calculation described in FIG. 7 as a judgment for focus adjustment operation, and when all subject distances are within the depth range, normal operation is performed, and When the dispersion of the n distance measurement results exceeds a predetermined depth, the lens is driven to stop the lens at the closest subject distance focusing position.

Similar to the embodiment shown in FIG.
When all distance measurement results are within the depth range, 5w64 performs normal distance measurement operation with the entire ONL sensor area as one zone. When the variation is outside the depth, the arithmetic circuit 61 extracts the signal from the memories 41 to 43 that indicates the closest distance, calculates the distance measurement direction and the amount of deviation from the focal length information, and drives the motor 27. It is.

FIG. 11 shows a flowchart of the system according to the embodiment of the present invention shown in FIG. 10, and in step 65, Hpf in each zone is calculated. In this example, we use 3 sensors.
Showing an example of division, the right side is C1, l center, and the left side is R, respectively.
, M, L, in step 65, that is, HpfR, Hp
fM and HpfL are calculated. In step 66, a value is calculated from the Hpf of each zone when Hpf crosses zero. In this example, in step 67, the subject distance for each distance measurement zone is determined from this value and the focal length information, and this is calculated as the focal plane position, but this is only to align the parameters for comparison, so step 69 When calculating the depth in the width k, step 67
becomes unnecessary. In step 68, the absolute value of the difference between the focal plane positions calculated in step 67 is calculated, and the depth of focus E (mostly E=2.8・F, where δ is a circle of confusion) calculated in step 69 is calculated. DIZlaX showing M.DELTA.X at the 9th point of the difference .about.D in each zone is compared in step 70 (this is the portion corresponding to the comparison circuit 50 in the M2O diagram). As a result of the determination in step 70, if DIllaX is smaller than E and υ, it is determined that the object is not a conflicting object, so the automatic focus adjustment performs a normal distance measurement operation with the entire sensor area as one zone. On the other hand, DmaX is y4. When l:J) is also large, in step 71 the one closest to the 3 seas is selected and in step 72 specific calculations are performed to rotate the motor. Thereafter, a predetermined Tanabata drive is performed in steps 73 to 75. Figure 12 shows that after detecting a competing object near and far, the aperture υ is changed without simply prioritizing the closest result from the n distance measurement results. This shows another modification example in which the brightness information of the subject is learned from a device etc. and based on this information, the user is asked to select the nearest object and the farthest object. The distance measuring field position to be entered into the circuit 61 is selected.

FIG. 13 shows the result of the brightness information detection 76 after detecting the conflict between far and near in the embodiment described in FIG.
When it is bright, there is a high probability of photographing a distant subject outdoors, so this is a modified example in which the farthest distance measurement result (or an intermediate one depending on the configuration) is used, and when it is dark, the closest distance measurement result is used. .

FIG. 14 is a flow chart showing the operation of the embodiment described in FIG.
In other words, if the object is a conflicting object, it is detected in step 78 whether the brightness is bright or dark according to a predetermined threshold value.If the result of this judgment is that it is dark, step 7
1, the closest distance measurement result is selected, and if it is bright, in this example, the farthest distance measurement result is selected in step 79. The following operations are similar to those in the above embodiment.

As explained above, in the present invention, the distance measurement area of the sensor is divided into n parts as necessary, and the subject distance can be determined from each area. By selecting the distance measurement field of view, it is possible to significantly improve the granularity of distance measurement, especially in cameras for video shooting, such as prioritizing short distances for competing subjects, and selecting priority distances based on brightness information, etc. As such, it is extremely effective as an automatic focus adjustment device.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram of a conventional automatic focus detection device to which the present invention is applied, FIG. 2 is a signal waveform diagram of the F41 illustrated device, and FIG. 6 is an automatic focus adjustment of a video camera to which the first illustrated device is applied. Figure 4 is a diagram showing the detection signal waveform used in the device shown in Figure 1. Figure 5 is an explanatory diagram showing the ranging area in the photographic field of view. Figure 6 is the operation of the diagram shown in Figure 5. 7 is a block diagram of the overall configuration of the automatic focusing device according to the present invention, FIG. 8 is a diagram showing a modification of the device shown in FIG. 7, and FIG. 9 is a diagram of another modification of the device shown in FIG. 10 is a diagram of still another modification of the device shown in FIG. 7, FIG. 11 is an operation flow chart of the device shown in FIG. 10, FIG. 12 is a diagram of still another modification of the device shown in FIG. Still another modification of the illustrated device, FIG. 14 is the thirteenth
Operation 70-chart of the illustrated device Fig. 19...Distance sensor 40...Gate 41.42.4 for setting divided areas
3...Distance information memo for each area +7-44.45.4
6...Arithmetic circuit patent applicant: Canon Co., Ltd.
57Figure 8Figure 9Figure 13

Claims (2)

[Claims] (1) A measurement system that can switch between calculating one object distance using signals within the distance measurement area and calculating n object distances by dividing the distance measurement area into n parts, or use them simultaneously. range device. (2) Claim No. 1 (1) characterized in that the warning device operates under a defined condition in which there is a difference between n distance measurement results.
) Distance measuring device described in item 2.