JPS6247612A - Focus detecting device - Google Patents

Abstract

PURPOSE:To perform desired focusing operation by selecting the closest object distance information in one-shot AF mode and selecting distance information which is closest to last measured object distance information in continuous AF mode. CONSTITUTION:Charge coupled devices 52-54 take measurements of distance of areas 11-13 surrounded with the dotted image of a finder visual field image 10 respectively. A selector 64 performs switching as to which of an absolute value circuit 67 and a subtractor circuit 66 the output signal of an arithmetic circuit 76 is outputted to on the basis of the output signal of a mode setting circuit 65 which sets the one-shot AF mode in which focus detection is performed once on every focus detecting operation or the continuous AF mode in which the focus detection is performed continuously in the focus detecting operation. In the one-shot AF mode, the closest object distance information is stored in a memory circuit 75 eventually and in the continuous AF mode, the object distance information closest to the last measured object distance information is stored in the circuit 75. Focusing operation is carried out on the basis of the data of the circuit 75 and an invariably desired object is focused.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a focus detection device for a camera that divides a photographic screen into a plurality of focus detection areas and obtains distance measurement information for a plurality of objects.

(Prior art and its problems) Conventionally, a camera equipped with a focus detection device has a distance measurement mark near the center of the shooting screen, and the subject to be photographed is placed within the mark to take a picture. If the subject was outside the center of the screen, it would be out of focus, making it difficult to use. Some cameras are equipped with a focus lock device that allows you to focus on areas other than the center of the screen, but they are difficult to use for beginners. In addition, some cameras automatically measure the distance of multiple subjects and select the closest subject distance information from multiple subject distance information to focus on, but the subject you want to focus on is not necessarily the closest one. It is often difficult to use because it is not necessarily located far away.

Furthermore, when a close-range object jumps into the screen during continuous autofocus (AF, ie, automatic focus detection) operation, the focus position shifts significantly, which is undesirable. -This kind of phenomenon is more likely to occur with reflex cameras and video cameras because they perform continuous autofocus.

For this reason, it has a configuration that automatically measures the distance of multiple subjects within the shooting screen, and among the multiple subjects measured,
There are cameras that give priority to focusing on the closest subject (for example, Japanese Patent Laid-Open No. 51-14
(See Publication No. 6028).

With normal photography lenses, the closest subject is often the main subject, and the method is to hold the camera, decide on the composition, adjust the autofocus, and then release the shutter (single-AP).
), the above method can be said to be a preferable method, but for cameras such as video cameras that require continuous focus adjustment and shooting (continuous AF), there is no time to decide the composition each time, and it is difficult to Objects often suddenly jump into the distance. At this time, the focus position shifts significantly, and even after the object disappears, it takes some time for the original subject to come into focus, making it difficult to use.

The present invention has been made in view of the above-mentioned problems, and it is possible to always focus on the desired subject without being affected by the object even if there is an object at a distance closer than the subject to be photographed. It is an object of the present invention to provide a focus detection device that is suitable for a continuous automatic focus detection type camera that can perform focus adjustment in a short time.

(Means for Solving the Problems) The first invention of the present application has a switching means for switching between a one-shot automatic focus detection mode and a continuous automatic focus detection mode, and when in the one-shot automatic focus detection mode, the The closest subject distance information is selected, and when in continuous automatic focus detection mode, the subject distance information closest to the subject distance information measured circularly is selected and focus detection of the photographing lens is performed. It is said that

That is, the first invention of the present application is a camera that divides the photographing screen into multiple detection areas and obtains a number of subject distance information. When in continuous automatic focus detection mode, which performs focus detection continuously, the focus detection area that outputs the distance signal closest to the previously measured distance is automatically selected, and the focus detection area that exists within that area is automatically selected. It is designed to focus on the subject.

The second invention of the present application is that the focusing distance range for the next distance measurement is automatically or manually set based on the distance measurement value obtained by circular distance measurement in the continuous automatic focus detection mode. It is characterized by the fact that

In other words, in the second invention of the present application, when the measured object distance deviates significantly from the previously measured object distance, the previous measured distance value is set to the maximum depth of field within the manual setting range. The photographic lens is controlled using the distance measurement value shifted to .

(Example) Embodiments of the present invention will be described below with reference to the accompanying drawings.

The focus detection principle of the focus detection device according to the present invention is to detect the correlated position of two images created by the subject light beams that have passed through the first and second parts of the photographic lens that sandwich the optical axis of the photographic lens. FIG. 1 shows an example of a focus detection optical system.

In FIG. 1, the photographing lens L. A condenser lens L is disposed via a mask Q in the vicinity of a position equivalent to the focal plane F of
, L3 are arranged, and left and right line sensors using, for example, charge-coupled devices (COD) are arranged on their imaging planes l, respectively. Condenser, lens L, is imaging lens L
, , acts to form an image of the entrance pupil of L3 within the exit pupil of the photographing lens L0.

The imaging lenses L t and L 3 are for secondarily forming an image primarily formed near the focal plane F onto the line sensor.

The image of the object to be focused is formed in front of the focal plane F, so-called front-focus image 2a is re-imaged in the line sensor area 3a and 4a, each approaching the optical axis OA,
On the contrary, the re-imaging 3b of the rear bin 2b.

4b move away from the optical axis OA. The distance between the two mutually corresponding points of the re-imaged images 3c and 4c of the in-focus image 2C has a specific size determined from the configuration of the optical system. Therefore, by converting the light distribution pattern of the image on the line sensor into electrical signals and determining their relative positional relationship, the distance to the object to be focused can be determined.

FIG. 2 shows a schematic diagram of a single-lens reflex camera equipped with a focus detection device according to the present invention.

In FIG. 2, the photographing lens L. A part of the light transmitted through the semi-transmitting mirror 5 is reflected by the total reflecting mirror 6 and enters the focus detection monoule 7. Further, the light reflected by the semi-transmissive mirror 5 enters the finder optical system 8. A photographing lens located below the pentaprism 8a of the finder optical system 8. An electro-optical element 9 is arranged at the planned focal plane.

This electro-optical element 9 is for displaying the distance measurement area.

Figure 3 shows the viewfinder field image. In FIG. 3, 10 is the entire visual field image, and three areas 11, 12 and 13 surrounded by dotted lines are focus detection areas. In this embodiment, there are three focus detection areas, but the number is not limited to this. In the following, a case will be described in which three focus detection areas 11, 12 and 13 are provided.

4(a) and 4(b) show details of the electro-optical element 9 shown in FIG. 2. Transparent electrodes 9b, 9b, and 9b3 having shapes as shown in are coated. These transparent electrodes 9b, 9b, and 9b3 are formed in shapes corresponding to the outer shapes of the focus detection areas 11, 12, and 13, respectively, in FIG. 3.

9C is an electrochromic film such as tungsten oxide or iridium hydroxide, and 9d is an electrolyte. When the electrochromic material is tungsten oxide,
Coloring is achieved by setting the transparent electrode side to a positive potential and applying electricity. 9f is a colorless and transparent glass plate, the inner surface of which is coated with a transparent electrode 9e having a shape as shown in FIG. 4(b).

Therefore, the transparent electrodes 9 b, 9 b, or 9 b,
By supplying electrical energy between the transparent electrode 90 and the transparent electrode 90, the focus detection area is displayed. For example, in Figure 4 (b
), if electricity is applied between the transparent electrodes 9b and 9e, only the corresponding focus detection area 11 can be displayed in the finder. This is used to indicate the area where focus detection is currently being performed, as will be described later.

FIG. 5 shows an example of a focus detection optical system having a plurality of focus detection areas.

In FIG. 5, Lo is a photographing lens, and La and Lb
is the photographic lens L. It shows the area through which the focus detection light flux passes on the pupil plane. 21 is a focus detection area mask placed immediately after the planned focal plane, and openings 21a, 21b, and 21c formed in this focus detection area mask 21
is the three focus detection areas on the shooting screen + 1.12.13
(See Figure 3).

An opening 21a on the focus detection area mask 21.

Immediately after 21b and 21c are condenser lenses 2, respectively.
2a, 22b and 22c are arranged. These condenser lenses 22a, 22b and 22c have aperture masks 23a to 23f as photographic lenses L. The image is formed within the exit pupil of the That is, the aperture masks 23a and 23b are connected to the photographing lens L by the condenser lens 22a. The images are respectively formed on areas La and Lb within the exit pupil of the aperture mask 23.
c and 23d are photographic lenses L formed by condenser lenses 22b. The images are respectively formed on areas La and Lb within the exit pupil of .

Further, the aperture masks 23e and 23'f are formed by the condenser lens 22c in the area L within the exit pupils of the photographic lenses I and O.
Images are formed on a and Lb, respectively. In this way, the aperture mask 23
a to 23f are photographing lenses I; This is to determine the focus detection light flux areas La and Lb within the exit plane.

Immediately after the aperture masks 23a to 23F, an imaging lens 24
a to 24f are arranged respectively. These imaging lenses 24a to 24f are photographic lenses L. This is a guide for secondarily forming an image formed near the focal plane F on the line sensor 26. The lindrical lens 25 arranged immediately after the imaging lenses 24a to 24f has an aperture mask 23a.
It has a refracting power only in the direction orthogonal to the direction in which the lines 23f to 23f are lined up, and the image in that direction is reduced and formed on the line sensor 26.

Since the line sensor 26 is shorter in the vertical direction than in the horizontal direction (the direction in which the aperture masks 23a to 23f are lined up), this linear lens 25 reduces the image in the vertical direction more than in the horizontal direction, thereby reducing the focus detection area. , but is not required. 2'6a to 26c are CCD
The sensor 26a is an image sensor composed of one-dimensional sensors such as imaging lenses 24a, 24. The sensor 26b is located at a position where it receives the image formed by the imaging lens 24C924d, and the sensor 26c is located at a position where it receives the image formed by the imaging lens 24e and 24r. are placed in their respective positions. Therefore, the sensors 26a, 26b, and 26c can separately measure distances in three different areas (focus detection areas 11, 12, and 13) on the photographic screen.

FIG. 6 shows a side view of the focus detection optical system shown in FIG. 5 above.

FIG. 7 shows another embodiment of the focus detection optical system, and only the points different from FIG. 5 will be described below.

In FIG. 7, 21' is a focus detection area mask in which only one rectangular opening 31 is provided. 22
A condenser lens is placed immediately after the focus detection area mask 21', and its function is the same as that of the condenser lenses 22a to 22c shown in FIG. In this example, the sensors 26°a, 26'b and 26°C of the line sensor 26
Above, the images of 2 Via, 2 Via B, and 2 ViC on the focus detection area are arranged in a staggered manner. That is, a part of the image formed on sensor 26°a is also formed on sensor 26°b, and a part of the image formed on sensor 26°b is also formed on sensor 26°a and 26°C. It is also imaged. Further, a part of the image formed on the sensor 26°a is also formed on the sensor 26''b.In this way, the focus detection area 21'
The images of a, 21'b and 2bC are arranged so as to overlap with each other and are imaged on the line 7'26'2. This happens when the camera vibrates due to camera shake, etc.
Taking lens L due to sudden change in focus detection area. This is to prevent the focus position from shifting significantly. FIG. 8 shows the above sensors 26°a, 26°b, on the photographing screen.
26'C's viewing area is shown. Area 11' is the range of sensor 26a, and area 12' is the range of sensor 26a.
Area 13' is the sensor 26'c within the range of 6'b.
This is the range that can be seen.

FIG. 9 shows an AP having multiple focus detection areas according to the present invention.
This is an example of the right camera circuit configuration.

The configuration and operation of the circuit shown in FIG. 9 will be explained below.

A clock supply circuit 50 generates a lock necessary for system operation. 51 is a drive circuit which receives a clock from the clock supply circuit 50 and drives a charge-coupled device (hereinafter abbreviated as COD) 52. Drives CCD53 and CCD54.

55-57 are AD converters for AD converting the analog signals output from the CCDs 53-54. 58-6
0 is a memory for storing digital signals output from the AD converters 55 to 57. In addition, CCD52.
53 and 54 are sensors 26b, 26a and 26C1 in FIG. 5, sensors 26°b, 26°a and 26C in FIG.
6'C respectively.

Gate circuits 61 to 63 are connected to the output ends of the memories 58 to 60 and sequentially output signals from the memories 58 to 60 to the arithmetic circuit 76 in response to signals output from the clock supply circuit 50.

The arithmetic circuit 76 is for converting each output signal of the CCD 52 to CCD 54 into a signal corresponding to object distance information or defocus amount information.

The selector 64 selects one-shot AP, which performs focus detection once for each focus detection operation (for example, pressing the shutter button one step), and continuous AP, which performs focus detection continuously during the focus detection operation. In the AP mode, it is also possible to select a shooting distance range setting mode in which the shooting distance range is set and a shooting distance range free mode in which the shooting distance range is not set. The output signal of subtraction circuit 6
6 or the absolute value circuit 67.

The comparison circuit 68 compares the output of the absolute value circuit 67 and the output of the memory circuit 72, and outputs a high level signal when the output of the absolute value circuit 67 is smaller than the output of the memory circuit 72. .The gate circuit 71 is the comparator circuit 6.
When the output of 8 becomes high level, the output of the absolute value circuit 67 is output to the memory circuit 72), so the memory circuit 72 receives the smaller value of the output value of the absolute value circuit 67 and the memory value of the memory circuit 2 things are stored.

The register 69 is a register that stores a certain value (a sufficiently large constant, for example, a value corresponding to ■ in the shooting distance), and is used to initialize the memory circuit 72, and is used to supply a clock at the beginning of the focus detection operation. circuit 5
By supplying the pulse e from 0 to the gate circuit 70, the value is loaded into the memory circuit 72.

Lens ROM73 is the photographing lens L. established individually,
The shooting lens L. The focal length f1 release FNo, etc. of , are stored. This lens ROM 73 outputs focal length information r and aperture information F to the calculation circuit 83 when the mode setting circuit 65 is in the continuous AP mode and the shooting distance range setting mode is selected. Arithmetic circuit 83
calculates the depth of field by calculating the subject distance information stored in the memory circuit 77 and the focal length information f1 and aperture information F output from the lens ROM 73.

The MAX circuit 84 detects the maximum depth of field distance from the output of the arithmetic circuit 83, and the MIN circuit 85 detects the minimum depth of field distance from the output of the arithmetic circuit 83.

The comparison circuit 86 compares the object distance information stored in the memory circuit 75 with the maximum depth of field distance output from the MAX circuit 84 and outputs a high or low level signal. Further, the comparison circuit 87 compares the subject depth of field distance stored in the memory circuit 75 and outputs a high or low level signal. The logic circuit 88 is
A logic signal is output according to the combination of high or low signals output from comparison circuits 86 and 87. The selector 89 selects and outputs one output from among the outputs of the memory circuit 75, MAX circuit 84, and MIN circuit 85 in accordance with the output of the logic circuit 88. That is, the object distance information in the memory circuit 75 is
4 and within the depth of field distance range of the M I N circuit 86, the information of the memory circuit 75 is output, and the object distance information of the memory circuit 75 is within the maximum field distance range of the M A X circuit 84. When it is larger than the depth distance, the maximum depth of field distance information of the MAX circuit 84 is outputted, and the memory circuit 7
When the subject distance information No. 5 is smaller than the maximum depth of field distance output from the MIN circuit 85, the MIN circuit 85
This outputs the minimum depth of field distance information. The gate circuit 74 outputs the output data of the C0Ds 52 to 54 converted into body distance information or defocus amount information of the memory circuit 58 to the memory circuit 75 in accordance with the signal output from the comparison circuit 68.

The comparator circuit 68 compares the output of the absolute value circuit 67 and the output of the memory circuit 72, and outputs a high level signal when the output of the absolute value circuit 67 is smaller than that of the memory circuit 72. Therefore, at that time, the gate circuit 61
CCD52~CCD outputting signals via ~63
The output signals of memory circuits 58 to 60 which have memorized the output of 54 are stored in memory circuit 75.

As described later, in the case of a one-shot AP, the CCD
Among the CCDs 52 to 54, the one that outputs the closest distance signal is stored in memory, whereas in the case of continuous AP, the one that outputs the closest signal to the previously measured distance information is stored. The output of the COD will be stored in memory.

The selector circuit 78 switches between the memory circuit 75 and the selector circuit 89 in accordance with the signal output from the AND circuit G3. That is, when the mode setting circuit 65 is set to the continuous AF mode and the shooting distance range setting mode, the mode setting circuit 6
Since the level of line B outputted from 5 becomes high level, the output of the selector circuit 78 is inputted to the arithmetic circuit 79 at the timing of the signal d inputted to the other input terminal of the AND circuit G3. On the other hand, even if the mode setting circuit 65 is set to the continuous AP mode, when the shooting distance range is set to the free mode, the output of the line Q1 of the mode setting circuit 65 is at a low level, so the AND circuit G3 The output of memory circuit 7 also becomes low level.
The output of No. 5 is manually input to the arithmetic circuit 79.

The arithmetic circuit 79 is connected to the memory circuit 75 or the selector circuit 8.
According to the output of 9, the photographing lens L. or,
Calculate the amount of addition. The motor drive circuit 80 operates the photographing lens L based on the signal from the arithmetic circuit 79. Outputs a signal when focus adjustment is completed. A latch circuit 82 latches the output of the focus determination circuit 81.

In the AND circuit G4, when the mode setting circuit 65 is set to one-shot AP, the output line ρ3 of the mode setting circuit 65 becomes high level, so once the focus signal is output, the output of the latch circuit 82 goes high. level,
It functions to prohibit the operation of the motor drive circuit 80 from now on (
Once in focus, the motor comes to a complete stop. ).

In the OR circuit G5, the mode setting circuit 65 is one-shot A.
In the case of P, the output line Q of the mode setting circuit 65 becomes high level, and when one input terminal of the AND circuits Gl and 02 is set to high level and a clock signal is applied, C is outputted from the AND circuits Gl and 02. so that Also,
In the case of a continuous AP, the OR circuit G5 sets the output line Q of the mode setting circuit 65 to a low level so that the clock signal C is not output until the -shift focus signal is output. This is because in the case of a continuous AP, focus adjustment is initially performed based on information from the CCD 52. Here, after the CCD is focused at 52 degrees, the output of the latch circuit 82 becomes high level, so the CCD
Focus adjustment is performed based on information from 52 to CCD 54.

The operation of the focus adjustment device having the above configuration will be explained with reference to the timing chart of FIG. 10.

<One-Shot AF Mode> When performing one-shot AP, set the mode selection button (or a switch etc.) provided on the camera body to one-shot AP mode. Then, the selector circuit 64 is set by the signal output from the mode setting circuit 65 so that the output of the arithmetic circuit 76 is input to the absolute value circuit 67. Further, when the mode selection button is set to the one-shot AP mode, the mode setting circuit 6
The potentials of output lines Q, , Q, and Q3 of 5 are the following first
The result will be as shown in the table. ) [Margin below] Table 1 When the output line 121 of the mode setting circuit 65 is at a low level, the output of the AND circuit G3 is also at a low level, and the selector circuit 78 inputs the signal output from the memory circuit 75 to the arithmetic circuit 79. Configure settings to input. Further, when the output line Q is at a high level, the output of the OR circuit G5 is at a high level, and the input terminals of each of the AND circuits Gl and G2 are set at a high level, so that the clock supply circuit 50
Pulses b and c outputted from the gate circuits 62 and 63 are supplied to gate circuits 62 and 63.

Now, when a focus detection switch (not shown) is turned on by an operation such as pressing the shutter button one step and a focus detection operation is started, a pulse e is first supplied from the clock supply circuit 50 to the gate circuit 70. The fixed value stored in register 69 is stored in memory circuit 72. At the same time, the drive circuit 51 outputs a drive pulse C0D5.
2 to 54, the C0Ds 52 to 54 start an integration operation and output object brightness information. This subject brightness information is A/D converted by A/D conversion circuits 55-57 and then stored in memory circuits 58-60.

Next, when the clock supply circuit 50 outputs the pulse a, the gate circuit 61 is turned on, and the information in the memory circuit 58 is output to the absolute value circuit 67 via the selector 64. The output of the absolute value circuit 67 and the signal of the memory circuit 72 are
The comparator circuit 68 compares the data, but since the memory circuit 72 stores sufficiently large distance information (for example, oo) stored in the register 69, the output of the absolute value circuit 67 is smaller, and therefore the comparator circuit The output of 68 becomes high level. When the output of the comparison circuit 68 becomes high level,
Since the gate circuit 71 is turned on, the signal of the absolute value circuit 67 is stored in the memory circuit 72, and when the output of the comparison circuit 68 becomes high level, the gate circuit 74 is turned on, so the output of the memory circuit 58 is calculated. The signal is converted into a signal corresponding to the object distance in the circuit 76 and stored in the memory circuit 75.

Next, when the clock supply circuit 50 outputs the pulse b, the gate circuit 62 is similarly turned on, and the information in the memory circuit 59 is output to the absolute value circuit 67. Since the memory circuit 72 stores data corresponding to the object distance output from the CCD 52, the comparison circuit 68 compares the object distance information output from the CCD 52 and the object distance information output from the CCD 53. The closer distance information data is stored in the memory circuit 72.

Thereafter, when pulse C is output in the same way, the CCD 54
A comparison is made with the subject distance information output from
Finally, C0D52-54 is the closest distance information,
As explained with reference to FIG. 3, since the user is looking at different areas on the photographic screen, information on the object at the closest distance on the photographic screen is obtained. Data corresponding to the closest object distance information detected in this manner is also stored in the memory circuit 75. After that, when the clock supply circuit 50 outputs the pulse d, the memory circuit 7
The data of No. 5 is calculated by the calculation circuit 79, and the photographing lens L is operated by the motor drive circuit 80.

Focus adjustment is performed. When the focus adjustment is completed, the focus determination circuit 81 outputs a focus completion signal, the output of the latch circuit 82 becomes high level, and the output of the AND circuit G4 becomes high, so that the motor drive circuit 80 stops operating. In this way, the closest subject is brought into focus.

Continuous AP Mode> [A] First, the shooting distance range free mode in which no shooting distance range is set will be described.

Press the mode selection button to select Continuous AF - I side +
! The selector circuit 64 is switched by the signal output from the mode setting circuit 65 so that the outputs of C0D52 to C0D54 are input to the subtraction circuit 66.

Further, when the mode selection button is set to continuous AF and the shooting distance free mode, the potentials of the output line H, ρ2 and Q3 of the mode setting circuit 65 are as shown in Table 2 below.

Table 2 When a focus detection operation is started from this state, subject distance data output from the CCD 52 is input to the subtraction circuit 66 using a pulse a from the clock supply circuit 50. The output of the memory circuit 77 is input to the other input of the subtraction circuit 66, and the absolute value of the difference is compared with a register 69 storing sufficiently large distance information (for example, oo). As a result, the output of the subtraction circuit 66 is stored in the memory circuit 72. In this case, the process described above does not directly involve focus detection. Subtraction circuit 6 in memory circuit 72
When the output of CCD 6 is stored in memory, the information of CCD 52 is stored in memory circuit 75 based on the signal output from comparator circuit 68. The information stored here is object distance information at the center of the photographic screen.

Thereafter, pulses b and C are output from the clock supply circuit 50, but since the output of the OR circuit G5 is at a low level, the signals of the CCD 53 and CCD 54 are not output. Pulses a and b output from the clock supply circuit 50
, c completes the output of all subject distance information on the photographic screen.

Note that in this case, the signals of CCD 53 and CCD 54 are not utilized.

Thereafter, when the clock supply circuit 50 supplies the pulse f to the memory circuit 77, the memory circuit 77
The subject distance information output from 5 is stored in memory. This state continues until the next pulse r is input, so C
It is to be held until the next output of object distance information output from CDs 52 to 54 is completed.

In this way, the memory circuit 77 stores the previous subject distance information.

Next, when pulse d is output, the aforementioned Wanno Yacht AP
Similarly to the mode, the arithmetic circuit 79 and the mode drive circuit 80
Focus adjustment is performed at . In this way, focus adjustment is first performed on the subject at the center of the screen. When the focus adjustment is completed, the output of the focus determination circuit 81 becomes high level, so the output of the OR circuit G5 also becomes high level, and from then on pulses b and C are output.

When the focus determination circuit 81 outputs a focus signal, the clock supply circuit 50 outputs a pulse e and proceeds to the next focus detection operation. Similarly, the memory circuit 72 is initialized by the pulse e.

When the pulse a is input from the clock supply circuit 50 to the gate circuit 61, the difference S1 between the pulse a and the subject distance window data of the CCD 52 (stored in the memory circuit 77) is determined by the subtraction circuit 66. As a result of the comparison by the comparison circuit 68, the data initially loaded into the memory circuit 72 is sufficiently large, so the output of the subtraction circuit 66 is stored in the memory circuit 72. Here, the signal stored in the memory circuit 72 corresponds to the difference between the previous subject distance information and the current subject distance information.

Next, when pulse b is output, the subtraction circuit 66
Difference S between the subject distance correspondence data of D53 and the subject distance correspondence data at the previous focus 2-node.

is required. Comparison circuit 68 compares SI and 82 and stores the smaller one in memory circuit 72.

In this way, the object distance information of the CCD outputting the signal closest to the previous object distance information is finally stored in the memory circuit 75.

Thereafter, in the same way as in the one-shot AP mode, the amount of extension of the photographing lens Lo is calculated by the arithmetic circuit 79 at the timing of the pulse d, and the motor drive circuit 80) Seven Ki -
Su: j* h 7, Shi! - When the focus adjustment is completed, the pulse g is output from the focus determination circuit 8I to the clock supply circuit 50, so the clock supply circuit 50 outputs the pulse e and moves on to the next focusing step.

[B] Next, the shooting distance range setting mode in which the shooting distance range is set will be explained.

In this case, the mode setting circuit 65 sets the output line Q1 to high level (the other lines Q2 and Q3 remain unchanged). That is, the results are as shown in Table 3 below.

Table 3 Accordingly, the selector circuit 78 switches the output of the selector circuit 89 to be input to the arithmetic circuit 79 instead of the memory circuit 75.

Hereinafter, only the differences from the shooting distance range free mode will be explained. As a result of processing the subject information output from the CCDs 52 to 54, the memory circuit 75 stores the subject distance information closest to the previously measured subject distance information, and the memory circuit 77 stores the subject distance information closest to the previously measured subject distance information. ,
Previously measured object distance information is stored in memory.

The calculation circuit 83 calculates the depth of field distance based on the previously measured object distance information. At this time, the lens RO
The focal length Mf and aperture value F of the photographing lenses I and o are referenced from M73.

The M'AX circuit 84 and the MIN circuit 85 output the maximum field distance and the minimum field distance, which are compared with the object distance information output from the memory circuit 75. As a result, a comparison is made to see if the subject distance information is within the depth of field determined from the previously measured field distance information. If the subject distance information is within the depth of field, that information is output from the selector circuit 89, and if it exceeds the maximum depth of field, the maximum field distance information is output, and the minimum depth of field is If the distance is smaller, minimum field distance information is output. Thereafter, focus adjustment is performed by the arithmetic circuit 79 and motor drive circuit 80.

In the above explanation, we have explained that when using Continuous AF mode, the focus is initially on the center distance measurement area, but this is for the purpose of specifying the subject to focus on first, and the one-shot AF mode is Similarly, you can try to focus on the closest subject, and that usually works.

Also, during continuous AF, if you set the shooting distance range setting mode, the shooting lens L will be set from the previous focused distance. Although the depth of field is calculated from the focal length r and the aperture value F and used as the photographing distance range, it is also possible to manually set the distance range corresponding to the depth of field.

In addition, Continuous AF poetry and the L shooting lens used. It may also be possible to automatically switch between a mode in which the shooting distance range is set and a free mode depending on the type of camera. For example, in the case of a telephoto lens, the mode is switched to the shooting distance range setting mode, and in the case of a wide-angle lens, the mode is switched to the free mode.

(Effects of the Invention) According to the first invention of the present application, in the one-shot AF' mode, the closest subject distance information is discarded among a plurality of pieces of subject distance information, and in the continuous AF mode, the closest subject distance information is discarded. The camera focuses on the subject closest to the subject distance information, so even if there is an object at a close distance, you can always focus on the desired subject without being drawn to it. Since it takes only a short time to focus, it is possible to obtain a focus detection device suitable for sports photography, a video camera equipped with a continuous automatic focus adjustment device, and the like.

According to the second invention of the present application, since the focus adjustable range of the photographing lens is set in consideration of the depth of field, for example, if the measured subject distance deviates significantly from the previous time, Even in this case, it is possible to control the photographic lens and focus on the subject using a distance measurement value that is shifted by the depth of field or manual setting range from the previous distance measurement value.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of an example of a focus detection optical system, Fig. 2 is a schematic configuration diagram of a single-lens reflex camera equipped with a focus detection device according to the present invention, and Fig. 3 is a viewfinder of the single-lens reflex camera shown in Fig. 2. 4(a) and 4(b) are respectively a perspective view of an electro-optical element and an explanatory diagram of an electrode structure. FIG. 5 is an explanatory diagram of a focus detection optical system having a plurality of focus detection areas. An explanatory diagram showing an example. FIG. 6 is a side view of the focus detection optical system of FIG. 5. FIG. 7 is a perspective view of another embodiment of the focus detection optical system, FIG. 8 is an explanatory diagram of a viewfinder field image of a single-lens reflex camera equipped with the focus detection optical system of FIG. FIG. 1O, which is a circuit diagram of a camera equipped with an automatic focus detection device having a focus detection area, is a timing chart for explaining the operation of the circuit shown in FIG. 9. 7... Focus detection module, 8... Finder optical system, 9... Electro-optical element, 26... Line sensor,
26a to 26c, 26'a to 26°c - sensor, 52 to 54... CCD, 64... selector, 65... mode setting circuit, 73... lens RO
M0 Patent Applicant Minolta Camera Co., Ltd. Agent Patent Attorney Aoyama Ao et al. Fig. 1 [gl Fig. 2 a Fig. 3 Fig. 4 (a) i Fig. 6 (24φ (see) (24f) Fig. 8 figure

Claims (5)

[Claims] (1) In a camera equipped with a distance measuring device that automatically measures distances to multiple subjects within the shooting screen, there is a one-shot automatic focus detection mode that performs focus detection once for each focus detection operation, and a one-shot automatic focus detection mode that performs focus detection once per focus detection operation. has a switching means for switching between a continuous automatic focus detection mode in which focus detection is performed continuously at predetermined time intervals, and in the one-shot automatic focus detection mode, the closest object distance information among multiple object distance information is selected. The focus detection device is characterized in that when the continuous automatic focus detection mode is selected, subject distance information closest to the previously measured subject distance information is selected and focus detection of a photographing lens is performed. (2) Continuous automatic focus detection, which performs focus detection continuously at predetermined time intervals during focus detection operations, in cameras equipped with distance measurement means that automatically measure distances to multiple subjects within the shooting screen. mode, and in this continuous auto focus detection mode, the focusing distance range for the next distance measurement is set automatically or manually based on the distance measurement value of the previous distance measurement. A focus detection device characterized by: (3) The focus detection device according to claim 2, wherein the photographing distance range is set based on memory information arranged in a photographing lens of a camera. (4) When the distance measurement value of the next distance measurement exceeds the set shooting distance range, the photographing lens is set at the end of the shooting distance range. The focus detection device described in Section 1. (5) The focus detection device according to claim 2, wherein distance measuring areas of a plurality of objects to be distance measured overlap each other.