JPH04174409A - Focus detecting device - Google Patents

Abstract

PURPOSE:To make highly precise focus detection in plural distance measuring visual fields possible through a pair of picture element lines by suitably establishing the construction of an optical means to form the distribution of light quantity on a body image formed through an objective lens on the face of a light receiving means and the construction of a masking means to specify plural distance measuring visual fields. CONSTITUTION:Surrounding field lens part 33b has a multiple hole mask 34 and the exit pupil face 28 which 1 are set in a conjugating relation, and projects the centers of the openings 34a, 34b of the multiple hole mask 34 at the center of the exit pupil. Optical fluxs passing through the openings 34a, 34b of the multiplehole mask 34 severally enter the lens parts 35a, 35b of a reimaging lens 35, and severally form the secondary image of a body image on the faces of a pair of line sensors 36a, 36b of an optical transfer element 36. A pair of the secondary images are photoelectrically transferred by the line sensors 36a, 36b, and the fixed computation is executed for a signal obtained at the above time to determine the imaging state at an axially outside point of an objective lens.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a focus detection device suitable for photographic cameras, video cameras, etc., and in particular, it divides the exit pupil of an objective lens into a plurality of regions, and a focus detection device that passes through each region. The light flux is used to form a light intensity distribution for multiple object images, and the relative positional relationship of these multiple light intensity distributions is determined, and the so-called image shift method is used to find multiple distance measurement points within the shooting screen or arbitrary measurement points. The present invention relates to a focus detection device suitable for performing focus detection using a focal point as an object.

(Prior Art) Conventionally, there is a method called an image shift method as a light-receiving focus detection method that uses a light beam passing through an objective lens and has relatively high detection accuracy.

Among the focus detection devices using this image shift method, a focus detection device that performs focus detection for the central part of the shooting range and a plurality of other areas is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-120.
This is proposed in Publication No. 518.

13 to 15 are schematic diagrams of a part of the focus detection device proposed in the publication.

FIG. 13 shows a perspective view, FIG. 14 shows a vertical cross-sectional shape, and FIG. 15 shows a positional relationship between a pixel column and a light amount distribution of a photoelectric conversion device consisting of a single chip.

Reference numeral 42 denotes a multi-hole field mask, which has long sides in the lateral direction in the figure, has rectangular apertures arranged in parallel, and is arranged in the vicinity of the intended imaging plane of the objective lens (not shown). 43 is a filter that blocks light with a wavelength longer than near-infrared light, and 5o is a division, which is placed slightly apart from the intended image formation plane of the objective lens. The division 50 includes lens parts 50a, 50b, and 5 having different optical functions as described later.
0c.

50d, 50e, 50f, and 50g, and these parts are formed by changing either the lens thickness or the radius of curvature of the lens surface, or both. Moreover, instead of the division 50, a combination of an optical system such as a Fresnel lens in which different prisms are arranged for each aperture of a multi-hole field mask and a biconvex lens can be used.

51 is a convex lens, 53 is a two-image forming lens, these lenses form a re-imaging lens unit with a two-hole aperture 52 in between, and the convex lens 51 converts incident light into a state close to parallel light, and has an optical effect. (described in Japanese Patent Publication No. 62-33564), and a two-image forming lens 53 formed by joining two convex lenses 53a and 53b side by side forms two secondary images of the object image formed by the objective lens. In the drawing, the two-hole aperture 52 described above is a vertically long elliptical opening 52a arranged in the horizontal direction.

52b.

54 is a concave lens for field curvature correction, and is arranged on a transparent plastic package 56 that houses a charging conversion device 55 (FIGS. 14 and 15). Note that the division 50, the convex lens 51, and the concave lens 54 of the reimaging lens unit are either vertically shaped or are rotationally symmetrical spherical lens systems.

The light flux passing through the aperture 42 a = 42 g of the multi-hole field mask 42 is divided into lens portions 50 a, 50 b, 50 c, and 50 d of divisions 50 as shown in FIG.

50e, 50f, and 50g, and form secondary images of the object on the photoelectric conversion device 55, respectively.

Figure 15 shows this situation, with 60a and 60b,
---60m and 60n and 62a and 62b are a set of pixel rows (line sensors) consisting of a large number of pixels, 62a,
A filter having a bandpass characteristic approximately equal to the emission wavelength of an object illumination device (not shown) is formed on the filter 62b. Aperture images 61a to 61n of the apertures 42a to 42g of the multi-hole visual field mask 42 correspond to these pixel columns.
is projected, and a secondary image of the object is formed inside this. At that time, the width of each aperture of the multi-hole viewing mask 42, the width of the light shielding zone 42h...42m between each aperture, and the photoelectric conversion device 55
Mask 42 according to the width of the upper pixel row and the pitch of the pixel row.
Since the refractive power of the optical system relaying the and device 55, especially each lens part of the division 50 and the re-imaging lens unit, is adjusted, the light-shielding zone 42h-...4 of the multi-hole field mask 42 is adjusted.
2m prevents a part of the luminous flux emitted from each predetermined aperture from entering a pixel column other than the pixel column (line sensor) corresponding one-to-one with this aperture.

Further, the field mask image is created by the action of the apertures 52a, 52b and the lens portions 53a, 53b.
Two apertures are formed side by side in the horizontal direction, and two of the objects inside the aperture are formed in parallel in the horizontal direction, and
The next image moves in the direction of the arrow and in the direction of B. Therefore,
Since each set of pixel rows detects the relative interval of the light intensity distribution regarding the pair of secondary images based on the photoelectric conversion output, it is possible to know the focus state of the objective lens for multiple distance measurement positions. I can do it.

(Problems to be Solved by the Invention) A conventional focus detection device that performs distance measurement in a plurality of areas requires one pair of pixel rows (line sensor) for one distance measurement field of view. For this reason, if the number of distance measurement fields of view is increased, it is necessary to increase the number of pixel rows accordingly, and the chip size of photoelectric conversion elements such as CCDs tends to increase. Generally, in manufacturing CCD etc.
As the area increases and becomes larger, it becomes technically more difficult.

The present invention provides a focus detection device using an image shift method.
By appropriately setting the configuration of the optical means that forms the light amount distribution regarding the object image formed by the objective lens on the surface of the light receiving means, and the configuration of the mask for specifying multiple distance measurement fields, it is possible to achieve a simple configuration. In particular, it is an object of the present invention to provide a focus detection device that can perform focus detection with high precision in a plurality of distance measurement fields using a pair of pixel rows (line sensors).

(Means for Solving the Problems) The focus detection device of the present invention uses optical means disposed on the image plane side of the objective lens to detect an object image by using light fluxes that have passed through different regions of the exit pupil of the objective lens. A plurality of light intensity distributions are formed on a surface of a light receiving means through a mask having a plurality of apertures, a relative positional relationship of the plurality of light intensity distributions is determined by the light receiving means, and an output signal from the light receiving means is used. When determining the in-focus state of the objective lens, the optical means receives the light beam that has passed through the aperture of the mask and a split field lens that is made up of a plurality of field lenses that have mutually different optical axes and is arranged near the intended image plane. and a re-imaging lens that guides light onto the means surface, and each of the plurality of field lenses has an optical function of projecting an exit pupil image of the objective lens onto the mask surface, and each of the field lenses has an optical axis. The intervals are set such that portions of the exit pupil images overlap each other on the mask surface, and furthermore, at least one of the plurality of apertures of the mask overlaps a portion of the exit pupil image formed on the mask surface. It is characterized by being arranged so as to be located within an overlapping area of the two.

In this shrub invention, the plurality of apertures of the mask are arranged in a one-dimensional direction, and the vicinity of the intended imaging plane of the objective lens is arranged in the same direction as the direction in which the plurality of apertures of the mask are arranged. It is characterized in that a movable mask having one movable opening is arranged.

(Embodiment) FIG. 1 is a perspective view of the main part of a first embodiment of the present invention, and FIGS. 2 and 3 are schematic views of the main part in the xz plane (cross section) of FIG. 1.

In the figure, 1 is an objective lens, and 28 is an exit pupil of the objective lens 1. (In addition, the objective lens 1 is omitted in FIG. 1.) 31 is a movable mask, which has one opening 31a, and is arranged in the vicinity of the intended imaging plane of the objective lens 1.

FIG. 2 shows a case where the aperture 31a of the movable mask 31 is located on the optical axis, and FIG. 3 shows a case where the aperture 31a is located off the optical axis.

The end of the movable mask 31 is fixed with a support plate 22.

The support plate 22 has a screw thread formed thereon and engages with a lead screw 21a of the stepping motor 21. The movable mask 31 is moved in parallel in the X direction of arrow C (D) by driving the stepping motor 21 in the direction of arrow A (B).

Note that instead of moving the movable mask 31, a liquid crystal display panel may be used so that the corresponding area can be electrically switched to be transparent.

A fixed mask 32 has three slit-shaped openings 32a, 32b, and 32c extending in the X direction. The movable mask 31 has three openings 32a to 32 of the fixed mask 32.
Take three positions corresponding to c. In addition, the fixed mask 32
Three or more openings may be provided in the opening, and in this case, the movable mask 31 takes a position corresponding to the number of openings.

33 is a divided field lens, and three field lenses 33a, 33b correspond to the three apertures 32a, 32b, 32c of the fixed mask 32.

It consists of 33c. 88a, 88b, and 88c are optical axes of field lenses 33a, 33b, and 33c, respectively, and are different from each other. In the figure, optical axes 88a to 88c are parallel to each other.

34 is a porous mask, which has four openings 34a to 34a in the X direction.
It has 34d. 35 is a re-imaging lens, and includes four lenses 35a to 35d corresponding to the four apertures 34a to 34d of the porous mask 34. Reference numeral 37 denotes a light receiving means, which is composed of a transparent resin package in which a photoelectric conversion element 36 is enclosed. The photoelectric conversion elements 36 are a pair of line sensors 36a in which a plurality of elements are arranged in the X direction.

It consists of 36b.

In this embodiment, the movable mask 31, fixed mask 32, support plate 22, stepping motor 21, etc. constitute one element of the mask means. The split field lens 33, reimaging lens 35, etc. constitute each element of the optical means.

Next, the operation of each element will be explained using FIGS. 2 and 3.

FIG. 2 is a schematic diagram when the aperture 31a of the movable mask 31 is located on the optical axis of the objective lens 1. The light beam for focus detection passes through the opening 031a of the movable mask 31 and the opening 32a of the fixed mask 32, and then enters the field lens portion 33a at the center of the divided field lens 33. This split field lens 33 has the porous mask 34 and the exit pupil plane 28 of the objective lens 1 in a conjugate relationship at the center, and in particular projects the centers of the two apertures 34b and 34c of the porous mask 34 onto the center of the exit pupil 28. ing.

Furthermore, the light flux passing through the openings 34b and 34c of the porous mask 34 is directed to the lens section 3 of the re-imaging lens 35 placed behind it.
5b and 35c, respectively. The lens portions 35b and 35c of the re-imaging lens 35 place the intended image-forming surface of the objective lens 1 and the light-receiving surface (line sensor) of the photoelectric conversion element 36 in a conjugate relationship, and charge the secondary images of the pair of object images. Formed on the light-receiving surface of the conversion element. With this re-imaging lens 35,
A pair of line sensors 36a and 36b each consisting of a large number of pixels are disposed on the photoelectric conversion element 36 where an image of the aperture 32a of the fixed mask 32 is formed. Note that the line sensors 36a and 36b are arranged in the X direction. This line sensor 36a.

The back-projection image 36b becomes the distance measurement field of view.

The relative spacing of the above-mentioned secondary image changes in the directions shown by arrows F and E depending on the imaging state of the objective lens 1 with respect to the intended imaging plane, so after charge conversion, a prescribed calculation is performed. The imaging state of the objective lens 1 is obtained by applying

FIG. 3 is a schematic diagram when the aperture 31a of the movable mask 31 is located at a position off the optical axis of the objective lens 1, and corresponds to the case of multi-point distance measurement. The light beam for focus detection is transmitted through the aperture 31a of the movable mask 31 and the aperture 32b of the fixed mask 32.
After passing through the field lens 33, the light enters the field lens section 33b around the divided field lens 33.

The optical axis 88b of the field lens section 33b around the divided field lens 33 is different from the optical axis of the objective lens 1. The peripheral field lens portion 33b is a porous mask 3
4 and the exit pupil plane 28 of the objective lens 1 are placed in a conjugate relationship, and the centers of the apertures 34a, 34b of the porous mask 34 are projected onto the center of the exit pupil. Opening 3 of porous mask 34
4a.

The light beam passing through 34b is transferred to the lens portion 35 of the re-imaging lens 35.
a and 35b, respectively, and form secondary images of the object image on the surfaces of the pair of line sensors 36a and 36b of the charge conversion element 36, respectively.

As in the case of the on-axis distance measuring field shown in FIG. The imaging state of the objective lens 1 at an external point is determined. Note that the distance measuring system on the side of the aperture 32c of the fixed mask 32 is symmetrical with respect to the optical axis, so a description thereof will be omitted.

FIG. 4 is an explanatory diagram of the porous mask 34 in FIG. 1, and shows the positional relationship with the exit pupil image.

In the figure, 90a, 90b, and 90c are the central field lens section 33a and the peripheral field lens section 33b of the divided field lens 33, respectively.

33c is an exit pupil image of the objective lens 1. The openings 34b and 34c of the porous mask 34 are inside the exit pupil image 90a.
However, the opening 34 of the porous mask 34 is inside the exit pupil image 90b.
a and 34b are porous masks 34 inside the exit pupil image 90c.
The openings 34C and 134d are set to be located respectively. The openings 34b and 34c of the porous mask 34 are located in the common area of the two exit pupil images 90b and 90c, and the light beams from the two distance measurement fields 32a and 32b selectively enter these depending on the position of the movable mask 31. . By configuring the aperture of one mask 34 to receive light beams from two distance measurement fields, the sensor area can be reduced by reducing the projection of the expected image formation plane of the objective lens 1 and the charging conversion element 36. A plurality of fixed masks 32 can be made smaller.
It is possible to guide the luminous flux from the apertures (32a, 32b, 32c) onto the same pixel column of the line sensor. This makes it possible to measure distances at multiple locations using a pair of line sensors.

5 and 6 are a perspective view of the main parts showing the entire camera when the focus detection device based on the first embodiment of the present invention is applied to a single-lens reflex camera, and a sectional view of the main parts showing a part of the inside thereof. be.

In Fig. 5, 87 is a release button, 5 is a setting dial that can be operated with the index finger of the right hand, DSP is a liquid crystal display,
8 is a ranging field selection mode button that can be operated with the thumb of the left hand.

In FIG. 6, reference numeral 9 denotes focus detection means, which includes each element after the movable mask 20 in FIG.

10 is a camera body, 11 is a lens barrel that holds the objective lens 1 movably in the direction of the optical axis 12, and 13 is a main mirror, which, together with a sub-mirror 14, converts the object light that has passed through the objective lens 1 into a finder system. It is separated into focus detection means 9. 15 is the focusing plate, 16 is the Bentataha prism,
Reference numeral 17 indicates an eyepiece lens, which constitutes a finder system.

FIG. 7 is a circuit diagram showing an embodiment of a camera equipped with an automatic focusing device according to the present invention.

In the figure, PRS is a camera control device, and includes, for example, a CPU (central processing unit) and ROM inside.

It is a 1-chip microcomputer with RAM, EEPROM (Electrically Erasable Programmable ROM), and A/D conversion functions, and according to the camera sequence program stored in the ROM, automatic exposure control function, automatic focus detection function, Performs camera operations such as winding and rewinding the film. EEFROM is a type of nonvolatile memory, and various adjustment data are written in the process.

PRS communicates with peripheral circuits and lenses using communication signals So, SI, and 5CLK, and controls the operation of each circuit and lens.

SO is the data signal output from PRS, SL is PRS
The data signal 5CLK input manually is a synchronization signal of the signals So and Sl.

LCM is a lens communication buffer circuit, which applies lens power supply ■L to the lens when the camera is in operation, and serves as a buffer for communication between the camera and the lens when the signal CLCM from PRS is at a high potential level.

When PRS sets CLCM to °H° and sends predetermined data from SO in synchronization with 5CLK, LCM goes to SCL via the camera-lens interface.

Each SO outputs buffered signals LCK and DCL to the lens. At the same time, the buffer signal of the signal DLC from the lens is applied to Sl, and PRS synchronizes with 5CLK to Sl.
Manually input lens data from

SDR is a drive circuit for a line sensor device 5NS (line sensors 26a, 26b in FIG. 1) for focus detection;
Selected when signal C5DR is H', So, SI, 5C
Controlled from PRS using LK.

The signal CK is the CCD driving clock φ1. The signal INTEND, which is a clock for generating φ2, is a signal that notifies PRS that the accumulation operation has ended.

The output signal O8 of the SNS is the clock φ1. It is a time-series image signal synchronized with φ2, and after being amplified by an amplifier circuit in the SDR, it is output to the PRS as an AOS. PRS is AO
5 is manually input from the analog input terminal, synchronized with C, and sequentially stored in a predetermined address of the RAM after A/D conversion by the internal A/D conversion function.

Same < AGC, which is the output signal of SNS, is AGC in SNS
This is the output of the GC control sensor, and is input to the SDR and used for SNS storage control.

FIG. 8 shows an example of photoelectric conversion outputs of two images formed on the sensor arrays SAA and SAB. The output of SAA is A(i), S
Let the output of AB be B(i).

In this example, the number of pixels of the sensor is 40 pixels (i=0, ・
-, 39).

Signal processing methods for detecting the image shift amount PR from image signals A(i) and B(f) are disclosed in Japanese Patent Application Laid-open Nos. 58-142306, 1982-107313, and 1982-10.
Publication No. 1513, Japanese Patent Application No. 160824/1986, and the like are disclosed.

spc is a metering sensor for exposure control that receives light through the photographic lens, and its output 5spc is input to the analog input terminal of PRS, and after A/D conversion is used for automatic exposure control 4 (AE). .

DDR is a switch sense and display circuit, which is selected when the signal CDDR is 'H' and outputs So, $1,5.
Controlled from PRS using CLK. That is, the display member DS of the camera is displayed based on the data sent from the PRS.
It changes the display of P and informs the PRS of the on/off status of various operating members such as a release button (not shown) (linked to switches SWI and SW2) and a mode setting button.

SWI and SW2 are switches linked to the release button 87, and when the release button 87 is pressed in the first step, the SW is activated.
I is turned on, and then SW2 is turned on by pressing in the second stage. The control device PRS performs photometry and automatic focus adjustment when SW1 is turned on, and performs exposure control and subsequent film winding using SW2 as a trigger.

The SW2 is connected to the "interrupt input terminal" of the control device PR3, which is a microcomputer, and even if a program is being executed when SW1 is on, an interrupt is generated by turning on SW2, so that control can be immediately transferred to a predetermined interrupt program.

DCM is a setting dial buffer circuit, and switches SWA and S according to the operation of the setting dial 5 shown in FIG.
Based on the change in the state of WA, the rotation direction and number of pulses are determined by the signals RM and L.
It is output to the control device PRS as M and CNT.

SW3 is a switch linked to the distance measurement field of view selection mode button 8 shown in FIG. It changes depending on.

MDRI and MDR2 are drive circuits for film feeding and shutter spring winding motors MTRI and MTR2, and signals MIF, MIR, and M2F.

Execute forward/reverse rotation of the motor with M2R.

MDR3 is a drive circuit for the Stellar Dong motor MTR3 (number 21 in Figure 1) for moving the movable mask 20 of the focus detection device, and receives an instruction for the number of drive steps with the signal M3P and the drive direction with the signal M3D, and controls the stepping motor. Distributes pulses for each phase and amplifies current for excitation.

MCI and MG2 are magnets for starting the movement of the leading and trailing shutter curtains, respectively, and are energized by signals SMGI, 5MG2, and amplification transistors TR1 and TR2, and shutter control is performed by PRS.

In addition, switch sense and display circuit DDR.

The motor drive circuits MDRI, MDR2, and shutter control are not directly related to the present invention, so detailed explanations will be omitted.

A signal DCL that is manually input to the intra-lens control circuit LPRS in synchronization with LCK is data of a command from the camera to the lens FLNS, and the operation of the lens in response to the command is determined in advance.

The LPRS analyzes the command according to a predetermined procedure, performs focus adjustment and aperture control operations, and outputs various lens parameters (open F number, focal length, defocus amount vs. extension amount coefficient, etc.) from the output DCL. .

In the example, an example of a single lens with an entire edge is shown.
When a focus adjustment command is sent from the camera, a signal LMF is sent to the focus adjustment motor LMTR according to the drive amount and direction sent at the same time.

Driven by LMR, the optical system is moved in the optical axis direction to adjust focus. The amount of movement of the optical system is determined by the encoder circuit EN.
The signal LMF is monitored by the pulse signal 5ENC of C, and the coefficient is calculated by a counter in the LPR5.

Set LMR to L” and apply S braking to motor LMTR.

When an aperture control command is sent from the camera, a Stellar Dong motor DMTR, which is known for driving an aperture, is driven in accordance with the number of aperture stages sent at the same time. still,
The Stella Dong motor can be oven controlled, so
Does not require an encoder to monitor operation.

Next, the structure of the switches SWA and SWB (FIG. 7) which are switched in conjunction with the setting dial 5 shown in FIG. 5 will be explained using FIGS. 9, 10, and 11.

FIG. 9 is a diagram showing the configuration of switches SWA and SWB provided at the lower part of the setting dial 5 shown in FIG. 5. In FIG. 9, 161 is an electrode pattern section fixed to the camera, and 162 is a rotating section that rotates in conjunction with the rotation of the setting dial.

Reference numeral 163 denotes an electrode provided in the electrode pattern section 161, which together with brushes 169 and 171, a lever 166, and a common electrode pattern section 165, which will be described later, constitutes a switch SWA. 164 is an electrode provided in the electrode pattern section 161, and like the electrode 163, it is connected to the switch S along with brushes 170, 171, lever 162, and common electrode pattern section 165, which will be described later.
It constitutes the WB. Note that 165 is an electrode pattern portion that is grounded and always in contact with the brush 171.

Reference numeral 166 denotes a conductor lever fixedly attached to the rotating portion 162, and the brushes 169, 170, 171 are provided thereon. Reference numeral 167 denotes a recess provided inside the pattern portion 161, and together with a leaf spring 168 provided in the rotating portion 162, constitutes a click.

Figure 10 shows the changes in the states of the switches SWA and SWB when the setting dial 5 is rotated from the click position shown in Figure 9 in the direction B in Figure 9 until the next click. Explain using. Initially, the switches SWA and SWB are in the click position, so both switches SWA and SWB are grounded and become (L, L) as shown in FIG. 10a.

Next, when the setting dial 5 is rotated in the direction B, the rotating part 1
62 also rotates in conjunction, and the brush 170 is no longer in contact with the electrode 164, so the switches SWA and SWB are in the first state.
The position is (L, H) as shown in Figure 0. When the setting dial 5 is further rotated in the direction B, the brush 169 no longer comes into contact with the electrode 163, and the states of the switches SWA and SWB become (H, H) as shown at position C in FIG.

When the setting dial 5 is further rotated in the B direction, the brush 17
0 contacts the electrode 164 again so that the switch SWA, S
The state of the WB is (H, L) as shown at position d in Figure 10.
When the setting dial 5 is subsequently rotated, the states of the switches SWA and SWB become (L, L) again as shown at position Me<a> in FIG. Similarly, when the setting dial 5 is rotated in the opposite direction, the states of the switches SWA and SWB change as shown in FIG.

Therefore, the input ports 11 .corresponding to each of the switches SWA and SWB. Both IO signals (L.

When the signal is L), the dial 5 is in a stable state in the click position as shown in FIGS. It can be determined that it was operated in the direction, or it could be a signal in the opposite direction (L.

When it changes to H), it can be determined that the operation has been made in the C direction.

Such operation of the setting dial 5 is normally used to change the settings of the shutter speed or aperture value, while while the distance measurement field selection mode button 8 (Fig. 5) is pressed, it is used to select the distance measurement field. be done.

In order to select the distance measurement field of view, first, the distance measurement field of view selection mode button 8 shown in FIG. 5 is pressed, and the switch SW3 (shown in FIG. 7) linked thereto is closed. As a result, the camera enters the distance measurement field of view selection mode, and the distance measurement field of view can be selected by operating the setting dial 5, that is, by operating the switches SWA and SWB.

That is, when the ranging field selection mode button 8 is pressed, the signal MDS is given to the control device PR3 by closing the switch SW3 (FIG. 7), and in this state, the setting dial 5 is
When is operated, switches SWA and SWB (Fig. 7)
, a signal 10, If is given to the control device via the buffer circuit DCM.

Incidentally, the PRS detects one click operation of the setting dial 5 and its direction, and sends a motor drive signal corresponding to moving the aperture position of the movable mask 31 to the adjacent distance measurement field position (the aperture of the fixed mask 32) to the motor drive. Output to circuit MDR3.

FIG. 12 is a perspective view of essential parts of a second embodiment of the present invention.

In this embodiment, the same elements as in the first embodiment shown in FIG. 1 are given the same reference numerals.

In this embodiment, the number of distance measurement fields is increased in the vertical direction (y direction) compared to the first embodiment shown in FIG. 1, so that distance measurement can be performed at nine locations in the entire photographing screen. Therefore, the fixed mask 81 has nine apertures 81a to 81a corresponding to the distance measurement field positions.
1i is provided. Further, the charging conversion element 85 constituting the light receiving means 86 includes three pairs of line sensors: line sensors 85a and 85b, line sensors 85c and 85d,
Line sensors 85e and 85f) are installed.

Furthermore, the opening 80a of the movable mask 80 is enlarged in the y direction, and is set to a size that includes the three openings of the fixed mask 81 in the y direction. And 1 of the movable mask 80
Three ranging fields per position function. That is, the first
At the position of the movable mask 80 shown in FIG. 2, the secondary image of the object image within the aperture 81a of the fixed mask 81 is reflected by the line sensors 85a, 85b due to the optical action of the two lens portions 84b, 84c of the re-imaging lens 84. A secondary image of the object image formed above and similarly within the aperture 81b is detected by the line sensor 85c.
, 85d, secondary images of the object image within the aperture 81c are formed on the line sensors 85e, 85f, respectively. The back-projected images of these line sensors form the actual distance measurement field of view.

In this embodiment, as in the first embodiment, by detecting the relative distance between the paired secondary images based on the photoelectric conversion output,
It is possible to know the imaging state of the objective lens 1 in each distance measurement field of view.

Furthermore, when the opening 80a of the movable mask 80 is located at a position corresponding to the openings 81d, 81e, and 81f of the fixed mask 81, the two lens portions 84a of the re-imaging lens 84,
84b, a secondary image of the object image within the opening 81d of the fixed mask 81 is formed on the line sensors 85a, 85b, and similarly a secondary image of the object image within the opening 81e is formed on the line sensors 85c, 85d. 2 of the object image within the aperture 81f
The next image is formed on line sensors 85e and 85f. An opening 81g of the fixed mask 81.

81h and 81i can be considered in the same way as optical axis symmetry.

As described above, the line sensors 85a and 85b are used for focus detection at the positions of the openings 81d, 81a, and 81g of the fixed mask 81, and the line sensors 85c and 85d are used for focus detection at the positions of the openings 81e, 81b, and 81h, and the line sensor 85e
, 85f are used for focus detection at the positions of the apertures 81f, 81c, and 81i.

As described above, in this embodiment, focus detection at nine positions within the photographic screen is performed using three pairs of line sensors.

In each of the above embodiments, there is no limit to the number of openings provided in the fixed mask, and any number of openings may be provided. In this case, the number of lenses of the split field lens, the numerical aperture of the mask, and the number of lenses of the re-imaging lens may be determined according to the number of apertures of the fixed mask.

(Effects of the Invention) According to the present invention, the configuration of the optical means, mask, etc. for guiding the light amount distribution related to the object image onto the light receiving means surface from the object image formed by the objective lens is set as described above. As a result, it is possible to achieve a focus detection device that can measure distances in a plurality of areas within the photographic screen using a pair of line sensors as light receiving means.

[Brief explanation of drawings]

FIG. 1 is a perspective view of essential parts of a first embodiment of the present invention, and FIG. Third
The figure is a cross-sectional view of FIG. 1, FIG. 4 is an explanatory diagram of a part of FIG. 1, and FIG. 6th. FIG. 7 is a perspective view of a main part, a sectional view of a main part, and a signal processing circuit diagram when the first embodiment of the present invention is applied to a single-lens reflex camera, and FIG. 8 is an output from the light receiving means according to the present invention. Explanatory diagram of signals, No. 9. 10th. Fig. 11 is a configuration diagram of a setting dial switch when the present invention is applied to a single-lens reflex camera, an operation diagram of the setting dial, and a state diagram of the switch, and Fig. 12 is a main part of a part of a second embodiment of the present invention. The perspective views and FIGS. 13 to 15 are explanatory diagrams of a portion of a conventional focus detection device. In the figure, 1 is an objective lens, 9 is a focus detection means, 10 is a camera body, 31.80 is a movable mask, 21 is a stepping motor, 32.81 is a fixed mask, 33.82 is a divided field lens, and 34.83 is a A mask, 35.84 a re-imaging lens, 36.85 a photoelectric conversion element, 36a. 36b, 85a to 85f are line sensors, 37.8
6 is a light receiving means, and 28 is an exit pupil. Patent Applicant: Canon Co., Ltd. Law Figure 9

Claims (3)

[Claims] (1) By optical means placed on the image plane side of the objective lens,
A plurality of light intensity distributions relating to an object image are formed on the light receiving means surface via a mask having a plurality of apertures using the light beams that have passed through different regions of the exit pupil of the objective lens, and the plurality of light intensity distributions are formed by the light receiving means. When determining the relative positional relationship between the objective lens and the focusing state of the objective lens using the output signal from the light receiving means, the optical means uses a plurality of optical axes having mutually different optical axes arranged in the vicinity of the planned imaging plane. It has a split field lens consisting of a field lens and a re-imaging lens that guides the light flux that has passed through the aperture of the mask onto the light receiving means surface, and each of the plurality of field lenses has an exit pupil of the objective lens. It has an optical function of projecting an image onto the mask surface, and the distance between each optical axis is set so that a portion of the exit pupil images overlap each other on the mask surface. A focus detection device characterized in that at least one aperture is located within a region where exit pupil images formed on the mask surface partially overlap. (2) The focus detection device according to claim 1, wherein the plurality of openings of the mask are arranged in a one-dimensional direction. (3) A movable mask having one aperture movable in the same direction as the direction in which the plurality of apertures of the mask are arranged is disposed near the intended image formation plane of the objective lens. The focus detection device according to claim 2.