JPH0664225B2 - Focus adjustment device - Google Patents

Description

The present invention relates to a focus adjusting device for a camera, which divides a photographing screen into a plurality of focus detection areas and obtains a plurality of subject distance measurement information.

(Prior Art and its Problems) Conventionally, as a camera including a focus adjustment device, a camera that performs focus adjustment on a subject in one area has been proposed.

By the way, a camera equipped with the conventional focus adjustment device described above,
A distance measuring mark is provided near the center of the shooting screen, and the subject to be shot is placed within that mark.When the subject is outside the center of the screen, it is out of focus and difficult to use. It was

In order to solve such a problem in a camera provided with a conventional focus adjusting device, there has been proposed one in which a main subject is automatically discriminated from among subjects in a plurality of areas to perform focus adjustment (for example, Japanese Patent Laid-Open Publication No. Sho. 59-146028).

However, in an ordinary photographing lens, the subject at the shortest distance is often the main subject, and even in the above-mentioned camera, focus adjustment is performed on the closest subject. Therefore, even if the camera is used to repeatedly perform focus adjustment on the same subject, when an object at a short distance jumps into an area different from the area capturing the subject during the repetition, Focus adjustment is performed on the object. At this time, the camera has a drawback that it is hard to use because the focus position is largely deviated and there is a time until the original subject is in focus even after the object disappears.

The present invention has been made in view of the above problems, and even if an object is located at a distance closer than the subject to be photographed, the subject is always focused on without being affected by it. It is an object of the present invention to provide a focus adjusting device that can be used.

(Means for Solving the Problems) In order to achieve the above object, the first focus adjustment device according to the present invention is a focus adjustment device for selectively performing focus adjustment on a subject in a plurality of areas in a shooting screen. A device for detecting object distance information in each area, selecting means for selecting the area based on the object distance information, and for an object in the area selected by the selecting means It has a focus adjusting means for performing focus adjustment, and a control means for repeating the operations of the detecting means, the selecting means and the focus adjusting means, and the selecting means has the object distance information closest to the object distance of the previously selected area. It is characterized in that the area detected by the detection means is selected.

In order to achieve the above object, a second focus adjusting device according to the present invention is a focus adjusting device which selectively performs focus adjustment on a subject in a plurality of areas in a shooting screen, and Detecting means for detecting a focus state on the subject; selecting means for selecting the area based on the focus state; focus adjusting means for performing focus adjustment on the subject in the area selected by the selecting means; Means, a selecting means, and a control means for repeating the operations of the focus adjusting means, wherein the selecting means is an area in which the focus state indicating the object distance closest to the object distance of the previously selected area is detected by the detecting means. It is characterized by selecting.

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

The principle of focus detection of the focus adjustment device according to the present invention is to detect the correlation position of two images formed by subject light fluxes that have respectively passed through the first portion and the second portion of the photographing lens sandwiching the optical axis of the photographing lens. Then, distance measurement is performed, and FIG. 1 shows an example of the focus detection optical system.

In FIG. 1, a condenser lens L ₁ is arranged near a position equivalent to the focal plane F of the taking lens L ₀ through a mask Q, and a mask (aperture mask) P behind the condenser lens L ₁ is provided. Imaging lenses L ₂ and L _{3 in the two} apertures
Are arranged on the image plane 1 of the charge-coupled device (CC
The left and right line sensors using D) are arranged respectively.
The condenser lens L ₁ has a function of forming an image of the entrance pupils of the imaging lenses L ₂ and L _{3 in} the exit pupil of the photographing lens L ₀ .
The image forming lenses L ₂ and L ₃ are for forming an image that is primarily formed near the focal plane F as a secondary image on the line sensor.

The image of the object to be focused is formed in front of the focal plane F, that is, the re-imaging 3a and 4a of the so-called front-focused image 2a in the area of the line sensor approach the optical axis OA, and on the contrary, rearward. The re-imaging images 3b and 4b of the pin 2b move away from the optical axis OA.
The distance between two corresponding points of the re-imaging images 3c and 4c of the image 2c in the case of focusing has a specific size determined by the configuration of the optical system. Therefore, if the light distribution pattern of the image on the line sensor is converted into an electric signal and the relative positional relationship between them is obtained, the distance to the object to be focused can be known.

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

In FIG. 2, a part of the light transmitted through the taking lens L ₀ passes through the semi-transmissive mirror 5, is reflected by the total reflection mirror 6, and enters the focus detection module 7. The light reflected by the semi-transmissive mirror 5 enters the finder optical system 8. The taking lens L located below the penta prism 8a of the finder optical system 8
_The electro-optical element 9 is arranged on the focal plane of ₀ . The electro-optical element 9 is for displaying a distance measuring area.

Fig. 3 shows a viewfinder image. In FIG. 3, 10 is the entire visual field image, and the three areas 11, 12 and 13 surrounded by the dotted lines are the focus detection areas. Although the number of focus detection areas is three in this embodiment, it is not limited to this. Below are three focus detection areas 11,1
The case of having 2 and 13 will be described.

4 (a) and 4 (b) show the details of the electro-optical element 9 shown in FIG. 2, which is a colorless transparent glass plate.
The inner surface of 9a is coated with transparent electrodes 9b ₁ , 9b ₂ and 9b ₃ having a shape as shown in FIG. 4 (b). These transparent electrodes 9b ₁ , 9b ₂ and 9b ₃ are shaped so as to correspond to the outer shapes of the focus detection areas 11, 12 and 13 of FIG. ₃ , respectively. 9c is an electrochromic film of tungsten oxide, iridium hydroxide or the like, and 9d is an electrolyte. When the electrochromic material is tungsten oxide, the transparent electrode side is colored by applying a positive potential and energizing. 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 9b ₁ , 9b ₂ or 9b
_The focus detection area is displayed by supplying electric energy between ₃ and the transparent electrode 9e. For example, it is possible in the fourth diagram (b), if current between the transparent electrode 9b ₁ and 9e, to display only the focus detection areas 11 corresponding thereto in the viewfinder. This is for indicating the area where focus detection is currently performed, as will be described later.

An example of a focus detection optical system having a plurality of focus detection areas is shown in FIG.

In FIG. 5, L ₀ is a taking lens, and La and Lb are regions on the pupil plane of the taking lens L _{0 where} the focus detection light flux passes. Reference numeral 21 denotes a focus detection area mask arranged immediately after the planned focal plane.
The openings 21a, 21b and 21c formed on the screen are 3 on the shooting screen.
Two focus detection areas 11, 12 and 13 are determined (see FIG. 3).

Apertures 21a, 21b and 21c on the focus detection area mask 21
Immediately after this, condenser lenses 22a, 22b and 22c are arranged, respectively. These condenser lenses 22a, 22b and 22c
Is for forming the aperture masks 23a to 23f within the exit pupil of the taking lens L ₀ . That is, aperture masks 23a and 23b
Are imaged on the areas La and Lb in the exit pupil of the taking lens L ₀ by the condenser lens 22a, respectively, and the aperture masks 23c and 23d are formed.
Is imaged on the areas La and Lb in the exit pupil of the taking lens L ₀ by the condenser lens 22b. Also, aperture mask
The condenser lenses 22c form images 23e and 23f on the areas La and Lb in the exit pupil of the taking lens L ₀ , respectively. As described above, the aperture masks 23a to 23f determine the focus detection light flux regions La and Lb in the exit surface of the taking lens L ₀ .

Immediately after the aperture masks 23a to 23f, image forming lenses 24a to 24f are arranged, respectively. These imaging lenses 24a-24f are
This is for secondarily forming an image formed near the focal plane F of the taking lens L ₀ on the licensor 26. Cylindrical lens 25 arranged immediately after the imaging lenses 24a to 24f
Has a refractive power only in the direction orthogonal to the arrangement direction of the aperture masks 23a to 23f, and reduces the image in that direction onto the line sensor 26 to form an image. In this cylindrical lens 25, since the line sensor 26 has a short vertical direction with respect to the horizontal direction (arrangement direction of the aperture masks 23a to 23f), the focus detection area is reduced in the vertical direction by reducing the image in the vertical direction from the horizontal direction. But it is not essential. 26a to 26c are CCD
Is an image sensor configured by a one-dimensional sensor, such as a sensor 26a at a position for receiving an image formed by the imaging lenses 24a, 24b, and a sensor 26b forms an image formed by the imaging lenses 24c, 24d. At the light receiving position, the sensor 26c is arranged at each of the positions for receiving the images formed by the imaging lenses 24e and 24f. Therefore, the sensors 26a, 26b, 26c can measure distances separately in three different areas (focus detection areas 11, 12, 13) on the photographing screen.

FIG. 6 is a side view of the focus detection optical system shown in FIG.

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,
Only one rectangular opening 31 is provided. Reference numeral 22 is a condenser lens disposed immediately after the focus detection area mask 21 ', and its function is the condenser lens 22a shown in FIG.
Same as ~ 22c. In this example, the image of 21'a, 21'b and 21'c on the focus detection area is formed on the sensors 26'a, 26'b and 26'c of the line sensor 26. There is. That is, a part of the image formed on the sensor 26'a is also formed on the sensor 26'b, and a part of the image formed on the sensor 26'b is formed on the sensors 26'a and 26'c. It also forms an image. A part of the image formed on the sensor 26'c is also formed on the sensor 26'b. In this way, the images of the focus detection areas 21'a, 21'b and 21'c are arranged so as to overlap each other and form an image on the line sensor 26 '. This is because when the camera vibrates due to camera shake,
This is to prevent the focus position of the taking lens L ₀ from being largely displaced due to a sudden change in the focus detection area. FIG. 8 shows an area on the photographing screen where the sensors 26'a, 26'b, 26'c look. Area 11 'is the range covered by sensor 26'a, area 12' is the range covered by sensor 26'b, and area 13 'is the range covered by sensor 26'c.

FIG. 9 shows an embodiment of the circuit configuration of an AF camera having a plurality of focus detection areas according to the present invention.

The configuration and operation of the circuit shown in FIG. 9 will be described below.
Reference numeral 50 is a clock supply circuit, which generates a clock necessary for system operation. A drive circuit 51 receives a clock from the clock supply circuit 50 and drives a charge coupled device (hereinafter abbreviated as CCD) 52, CCD53 and CCD54.

Reference numerals 55 to 57 are AD converters for AD converting the analog signals output from the CCDs 53 to 54. 58-60 is AD converter 55-
It is a memory for storing the digital signal output from the 57. The CCDs 52, 53 and 54 are the sensors 26 shown in FIG.
b, 26a and 26c, sensors 26'b, 26'a and 2 of FIG.
It corresponds to 6'c respectively.

Reference numerals 61 to 63 denote gate circuits connected to the output terminals of the memories 58 to 60, which sequentially output the signals of the memories 58 to 60 to the arithmetic circuit 76 according to the 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 according to subject distance information or defocus amount information.

The selector 64 is a one-shot AF that performs focus detection once for each focus detection operation (for example, an operation that presses the shutter button one step) and a continuous AF (continuous AF) that continuously performs focus detection during the focus detection operation. In AF, the shooting distance range setting mode for setting the shooting distance range and the shooting distance range free mode for not setting can be selected.) The signal output from the mode setting circuit 65 sets the arithmetic circuit 76. The output signal of is output to the subtraction circuit 66 or output to the absolute value circuit 67.

The comparison circuit 68 compares the output of the absolute value circuit 67 with the output of the memory circuit 72, and the output of the absolute value circuit 67 is the memory circuit 72.
When it is smaller than the output of, the high level signal is output. Since the gate circuit 71 outputs the output of the absolute value circuit 67 to the memory circuit 72 when the output of the comparison circuit 68 becomes high level, the memory circuit 72 stores the output value of the absolute value circuit 67 and the memory value of the memory circuit 72. The one with the smaller value will be stored.

The register 69 is a register that stores a fixed numerical value (a sufficiently large constant, for example, a numerical value corresponding to ∞ at the shooting distance), which initializes the memory circuit 72, and supplies a clock at the beginning of the focus detection operation. When the pulse e is supplied from the circuit 50 to the gate circuit 70, its value is loaded into the memory circuit 72.

Lens ROM73 is provided in the taking lens L ₀ each, the focal length f of the imaging lens L _0, is released FNo etc. are stored. The lens ROM 73 outputs the focal length information f and the aperture value information F to the arithmetic circuit 83 when the mode setting circuit 65 is in the continuous AF mode and the shooting distance range setting mode is selected. The arithmetic circuit 83 calculates the subject distance information stored in the memory circuit 77, the focal length information f and the aperture value information F output from the lens ROM 73,
Calculate the depth of field distance. The MAX circuit 84 is an arithmetic circuit 83
Detects the maximum depth of field distance, 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 subject 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 distance information stored in the memory circuit 75 with the minimum depth of field distance output from the MIN circuit 85, and outputs a high or low level signal. The logic circuit 88 outputs a logic signal according to a combination of high or low signals output from the comparison circuits 86 and 87. The selector 89 selects and outputs one output from the outputs of the memory circuit 75, the MAX circuit 84, and the MIN circuit 85 according to the output of the logic circuit 88. That is, the object distance information of the memory circuit 75 is MAX.
When it is within the depth of field distance range of the circuit 84 and the MIN circuit 86, the information of the memory circuit 75 is output, and the object distance information of the memory circuit 75 is more than the maximum depth of field distance output from the MAX circuit 84. If it is too large, the maximum depth of field distance information of the MAX circuit 84 is output, and the subject distance information of the memory circuit 75 is MI.
When it is smaller than the maximum depth of field distance output from the N circuit 85, the minimum depth of field distance information of the MIN circuit 85 is output. The gate circuit 74 stores the output data of the CCDs 52 to 54, which are stored in the memory circuits 58 to 60 and converted into subject distance information or defocus amount information by the arithmetic circuit 76, according to the signal output from the comparison circuit 68. Output to the memory circuit 75.

As described above, 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 that of the memory circuit 72. Therefore, the output signals of the memory circuits 58 to 60, which store the outputs of the CCDs 52 to CCD 54 which are outputting signals via the gate circuits 61 to 63 at that time, are stored in the memory circuit 75.

As will be described later, in the case of one-shot AF, CCD52-C
Of the CD54s, the one that outputs the closest distance signal is stored in memory, whereas in the case of continuous AF, the CCD that outputs the closest signal to the distance information measured last time. The output will be memorized.

The selector circuit 78 switches between the memory circuit 75 and the selector circuit 89 according to the signal output from the AND circuit G3. That is, the mode setting circuit 65 is
When the AF mode is set and the shooting distance range setting mode is set, the level of the line l ₁ output from the mode setting circuit 65 becomes a high level, so that it is input to the other input end of the AND circuit G3. The output of the selector circuit 78 is input to the arithmetic circuit 79 at the timing of the signal d that has been generated. On the other hand, even if the mode setting circuit 65 is set to the continuous AF mode, the output of the line l ₁ of the mode setting circuit 65 becomes low level when the shooting distance range is in the free mode. The output of G3 also becomes low level, and the output of the memory circuit 75 is input to the arithmetic circuit 79.

The arithmetic circuit 79 calculates the moving amount or the moving amount of the taking lens L ₀ according to the output of the memory circuit 75 or the selector circuit 89. The motor drive circuit 80 outputs a signal when the focus adjustment of the taking lens L ₀ is completed based on the signal of the arithmetic circuit 79. The latch circuit 82 latches the output of the focus determination circuit 81.

AND circuit G4, when the mode setting circuit 65 is set to the one-Shot AF, focus the output line l ₃ of the mode setting circuit 65 becomes the high level, once the output of the focus signal exits the latch circuit 82 is It becomes a high level and thereafter functions to prohibit the operation of the motor drive circuit 80 (once the focus is achieved, the motor is completely stopped).

OR circuit G5, when the mode setting circuit 65 is one-Shot AF, focus by the output line l ₂ of the mode setting circuit 65 becomes the high level, the clock signal one of the input terminals of the AND circuits G1 and G2 as a high level b and c are AND circuits G1
Make it output from G2. Further, the OR circuit G5, in the case of continuous AF is the output line l ₂ of the mode setting circuit 65 as the low level, until once focus signal out so that the clock signal b and c are not outputted. This is because, in the case of continuous AF, the focus adjustment is first performed based on the information of the CCD 52. CC here
D52 is looking at the center of the shooting area. After the focus is once obtained, the output of the latch circuit 82 becomes a high level, so the focus adjustment is performed based on the information of the CCD52 to CCD54.

The operation of the focus adjusting device having the above configuration will be described with reference to the timing chart of FIG.

<One-shot AF mode> When performing one-shot AF, set the mode selection button (or a switch etc.) provided on the camera body to the one-shot AF 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. When the mode selection button is set to the one-shot AF mode, the potentials of the output lines l ₁ , l ₂ and l ₃ of the mode setting circuit 65 are as shown in Table 1 below.

When the output line l ₁ of the mode setting circuit 65 is low level, the output of the AND circuit G3 also becomes low level and the selector circuit 78 outputs the signal output from the memory circuit 75 to the arithmetic circuit 79.
Set to input to. Also, the output line l ₂
Is high level, the output of the OR circuit G5 becomes high level, and one of the input terminals of the AND circuits G1 and G2 becomes high level, so the pulse output from the clock supply circuit 50
b and c are supplied to the gate circuits 62 and 63.

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

Next, when the pulse a is output from the clock supply circuit 50, the gate circuit 61 is turned on, and the information of 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 compared by the comparison circuit 68. Since the memory circuit 72 stores the sufficiently large distance information (for example, ∞) stored in the register 69, The output of the absolute value circuit 67 is smaller, so that the output of the comparison circuit 68 becomes high level. When the output of the comparison circuit 68 becomes high level, the gate circuit 71 is turned on, so that the signal of the absolute value circuit 67 is stored in the memory circuit 72.

Further, when the output of the comparison circuit 68 becomes high level, the gate circuit 74 is also turned on, so the output of the memory circuit 58 is the arithmetic circuit.
At 76, it is converted into a signal corresponding to the subject distance and the memory circuit
Stored in 75.

Next, when the pulse b is output from the clock supply circuit 50,
Similarly, the gate circuit 62 is turned on, and the information in the memory circuit 59 is output to the absolute value circuit 67. Where the memory circuit 72
Since the data corresponding to the subject distance output from the CCD52 is stored in the, the subject distance information output from the CCD52 and the subject distance information output from the CCD53 are
The data of shorter distance information compared by the comparison circuit 68 is stored in the memory circuit 72.

Thereafter, when the pulse c is output in the same manner, the object distance information output from the CCD 54 is compared, and finally the data corresponding to the closest distance information is stored in the memory circuit.
It is stored in 72.

As described with reference to FIG. 3, the CCDs 52 to 54 gaze at different areas on the photographing screen, so that the subject information at the closest distance on the photographing screen is obtained. The data corresponding to the closest object distance information detected in this way is also stored in the memory circuit 75. After that, when the pulse d is output from the clock supply circuit 50,
The data of the memory circuit 75 is calculated by the calculation circuit 79, and the focus of the photographing lens L ₀ is adjusted by the motor drive circuit 80. When the focus adjustment is completed, a focus completion signal is output from the focus determination circuit 81, 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 does not operate. In this way, the closest subject is in focus.

<Continuous AF Mode> [A] First, the shooting distance range free mode in which the shooting distance range is not set will be described first.

When the mode selection button is set to continuous AF and shooting distance range free mode, the selector circuit 64 is switched by the signal output from the mode setting circuit 65, and CCDs 52 to 5 are selected.
The output of 4 is input to the subtraction circuit 66.

Also, the mode selection button is continuous AF and
When the shooting distance free mode is set, the mode setting circuit
The potentials of the 65 output lines l ₁ , l ₂ and l ₃ are as shown in Table 2 below.

When the focus detection operation is started from this state, the subject distance data output from the CCD 52 by the pulse a from the clock supply circuit 50 is input to the subtraction circuit 66. The output of the memory circuit 77 is input to the other input of the subtraction circuit 66,
The absolute value of the difference is compared with the register 69 storing sufficiently large distance information (eg, ∞). 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 participate in direct focus detection. When the output of the subtraction circuit 66 is stored in the memory circuit 72, the information of the CCD 52 is stored in the memory circuit 75 by the signal output from the comparison circuit 68. The information stored here is subject distance information at the center of the shooting screen.

After that, pulses b and c are output from the clock supply circuit 50, but since the output of the OR circuit G5 is at low level, CCD5
The signals of 3 and CCD 54 are never output. The output of all the subject distance information on the shooting screen is completed by the pulses a, b, and c output from the clock supply circuit 50.

In this case, the signals of CCD53 and CCD54 are not used.

After that, the pulse f is supplied from the clock supply circuit 50 to the memory circuit
When supplied to 77, the memory circuit 77 stores the subject distance information output from the memory circuit 75. This state continues until the next pulse f is input, so CCD52-5
It is held until the next output of subject distance information output from 4 is completed.

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

Next, when the pulse d is output, focus adjustment is performed by the arithmetic circuit 79 and the mode drive circuit 80 in the same manner as in the one-shot AF mode described above. In this way, the focus adjustment is first performed on the subject in the center of the screen. When the focus adjustment is completed, the output of the focus determination circuit 81 becomes high level, so that the output of the OR circuit G5 also becomes high level and thereafter the pulses b and c are outputted.

When a focus signal is output from the focus determination circuit 81, the clock supply circuit 50 outputs a pulse e to start the next focus detection operation. Similarly, the pulse e causes the memory circuit 72 to be initialized.

When the pulse a is input from the clock supply circuit 50 to the gate circuit 61, the difference S ₁ between the object distance corresponding data of the CCD 52 and the object distance corresponding data at the previous focus adjustment (stored in the memory circuit 77) S ₁ Is obtained by the subtraction circuit 66. As a result of comparison by the comparison circuit 68, since the data initially loaded in the memory circuit 72 is sufficiently large, the subtraction circuit 66
Is stored in the memory circuit 72. The signal stored in the memory circuit 72 corresponds to the difference between the previous subject distance information and the present subject distance information.

Next, when the pulse b is output, the subtraction circuit 66 causes the CCD 53
The difference S ₂ between the object distance correspondence data of 1 and the object distance correspondence data of the previous focus adjustment is obtained. The comparison circuit 68 compares S ₁ and S ₂ and stores the smaller one in the memory circuit 72.

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

Thereafter, in the same manner as in the one-shot AF mode, the amount of extension of the taking lens L ₀ is calculated by the arithmetic circuit 79 at the timing of the pulse d, and the motor drive circuit 80 adjusts the focus. When the focus adjustment is completed, the focus determination circuit 81
Since the pulse g is output to the clock supply circuit 50,
The clock supply circuit 50 outputs the pulse e and shifts to the next focusing.

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

In this case, the mode setting circuit 65 sets the output line l ₁ to the high level (the other lines l ₂ and l ₃ do not change). That is, it is as shown in Table 3 below.

Therefore, the selector circuit 78 switches so that the output of the selector circuit 89 is input to the arithmetic circuit 79 instead of the memory circuit 75.

Only the points different from the shooting distance range free mode will be described below. As a result of processing the subject information output from the CCD52 to CCD54, as described above, 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 last time. The measured object distance information is stored in memory.

The arithmetic circuit 83 calculates the depth of field distance based on the previously measured subject distance information. At this time, the lens ROM73
The focal length f and the aperture value F of the taking lens L ₀ are referred to.

The MAX circuit 84 and the MIN circuit 85 output the maximum object distance and the minimum object distance, and the object distance information output from the memory circuit 75 is compared. As a result, it is compared whether or not the subject distance information is within the depth of field obtained from the previously measured depth-of-field distance information. When the subject distance information is within the depth of field, the information is output from the selector circuit 89, and when the maximum depth of field is exceeded, the maximum depth of field information is output and the minimum depth of field is output. When the distance is smaller, the minimum field distance information is output. Thereafter, the focus is adjusted by the arithmetic circuit 79 and the motor drive circuit 80.

In the above description, in continuous AF mode, it was explained that the focus was on the center distance measurement area for the first time, but this is for the purpose of first identifying the subject to be focused, one-shot AF As with, you can focus on the closest subject, and in most cases it works.

In the continuous AF mode, if the shooting distance range setting mode is set, the depth of field is calculated from the focal length f and the aperture value F of the shooting lens L ₀ based on the distance at which the focus was focused last time. Although the shooting distance range has been described, a distance range corresponding to the depth of field may be set manually.

Further, during continuous AF, the mode for automatically setting the shooting distance range may be switched to the free mode according to the type of the shooting lens L ₀ used.
For example, the telephoto lens is switched to the shooting distance range setting mode, and the wide-angle lens is switched to the free mode.

(Effect of the Invention) According to the first focus adjustment device of the present invention, since the subject distance information that is closest to the subject distance of the previously measured area selects the area, even if an object at a short distance jumps in. , The difference from the previous subject distance is large, it is determined that it is another subject, focus adjustment is not performed on that object, you can always focus on the desired subject,
Further, since it takes a short time to focus, it is possible to obtain a focus adjusting device suitable for taking a sports photograph or a video camera equipped with a continuous automatic focus adjusting device.

Further, according to the second focus adjustment device of the present invention, the focus state indicating the subject distance closest to the subject distance of the previously selected area selects the area, so that even if a short-distance object jumps in, Since the difference from the previous subject distance is large, it is determined that the subject is another subject, focus adjustment is not performed on the subject, and the desired subject can always be focused in a short time.

[Brief description of drawings]

FIG. 1 is an explanatory view of an example of an optical system for focus detection, FIG. 2 is a schematic configuration diagram of a single lens reflex camera equipped with a focus adjusting device according to the present invention, and FIG. 3 is a viewfinder of the single lens reflex camera of FIG. FIGS. 4 (a) and 4 (b) are perspective views of the electro-optical element and explanatory views of the electrode structure, and FIG. 5 is a view of a focus detection optical system having a plurality of focus detection areas. An explanatory view showing an example, and FIG. 6 is a side view of the focus detection optical system of FIG. FIG. 7 is a perspective view of another embodiment of the focus detection optical system, FIG. 8 is an explanatory view of a viewfinder field image of a single-lens reflex camera equipped with the focus detection optical system of FIG. 7, and FIG. FIG. 10 is a circuit configuration diagram of a camera equipped with an automatic focus adjustment device having a focus detection area, and FIG. 10 is a timing chart for explaining the operation of the circuit of FIG. 7 ... Focus detection module, 8 ... Viewfinder 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 ROM.

Claims (2)

[Claims] 1. A focus adjusting device for selectively adjusting the focus of a subject in a plurality of areas on a photographing screen, comprising: detecting means for detecting subject distance information in each area; and the subject distance information. Selection means for selecting the area based on the above, focus adjustment means for performing focus adjustment on the subject in the area selected by the selection means, and control for repeating the operations of the detection means, the selection means and the focus adjustment means Means for selecting the area in which the object distance information closest to the object distance of the previously selected area is detected by the detecting means. 2. A focus adjusting device for selectively adjusting the focus of a subject in a plurality of areas within a photographing screen, the detecting means detecting a focus state of the subject in each area, and the focus state. Selection means for selecting the area based on the above, focus adjustment means for performing focus adjustment on the subject in the area selected by the selection means, and control means for repeating the operations of the detection means, the selection means and the focus adjustment means. And a selecting means for selecting an area in which a focus state indicating a subject distance closest to the subject distance of the previously selected area is detected by the detecting means.