JPS62173413A - Focus detecting device - Google Patents

Abstract

PURPOSE:To convert a focus detecting speed to a high speed by constituting plural focus detecting optical systems in symmetrical positions of an optical axis of an objective lens. CONSTITUTION:A visual field mask 101, a field lens 102, a diaphragm 103 and a secondary image forming lens 104 are placed in said order, on an optical axis of an objective lens. The visual field mask 101 has a cross-shaped through- hole, and controls an air image of an object to be photographed, which has formed an image by the objective lens 106. The field lens 102 projects the dia phragm 103 to an exit pupil 108 of the objective lens 106, and sets the dia phragm 103 and the exit pupil 108 to a conjugate relation. The diaphgram 103 has four pieces of fan-shaped opening parts 103a-103d for setting the optical axis as a point symmetry, and the exit pupil 108 of the objective lens 106 is divided into four pieces of areas 108a-108d. The secondary image forming lens 104 has four pieces of lens parts 104a-104d corresponding to four pieces of opening parts 103a-103d of the diaphragm 103, and a visual field mask image 109 is formed on a photoelectric converting element 105 which has been placed in the rear side of the secondary image forming lens 104.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a focus detection device for a camera or the like.

More specifically, the present invention relates to improving the detection speed of a focus detection device that detects the in-focus state of an objective lens based on object brightness distribution in multiple directions.

(Prior Art) Conventionally, a focus detection optical system is provided, in which two images are formed by the light beams transmitted through different parts of the pupil of an objective lens, and a photoelectric conversion element that photoelectrically converts the formed images. A focus detection device is known that detects the in-focus state of an objective lens based on the luminance of a subject.

However, there may be cases where detection cannot be performed if the direction of the object brightness distribution does not correspond well to the foot exit direction.

To deal with this, the focus detection device can be used to achieve good detection accuracy even when the subject brightness distribution is deflected by adjusting the relative positional relationship between the two images multiple times. be.

(Problem to be Solved by the Invention) However, the amount of change in defocus in the relative positional relationship of two images in front of each other may be uneven depending on each focus detection optical system, or each positional relationship may be uneven. When the photoelectrically converted signal outputs are individually taken out from the photoelectric conversion elements and sent to the arithmetic means connected thereto, there is a problem that the focus detection speed is delayed.

The present invention has been made in view of these conventional problems, and its purpose is to increase the speed of focus detection.

(Means for Solving the Problems) +IRF In order to achieve the objective described above, the focus detection device according to the present invention is arranged on the optical axis of the objective lens in the conventional focus detection device of Moe, and is arranged on the optical axis of the objective lens. A plurality of focus detection optical systems are constituted by a secondary imaging lens having a plurality of lens parts at point-symmetric positions, and a diaphragm disposed in front of the secondary imaging lens and having an aperture corresponding to the lens part, A configuration is adopted in which the photoelectric conversion element is provided with an equivalent circuit that adds the corresponding signal outputs of the pixel columns of the photoelectric conversion element corresponding to each focus detection optical system.

(Example) Hereinafter, an example of the focus detection device according to the present invention will be described based on the drawings.

1 to 9 show a first embodiment of a plurality of division means of a focus detection optical system constituting the present invention.

In this embodiment, a field mask 1 is placed on the optical axis of the objective lens.
01, a field lens 102, an aperture 103, and a secondary imaging lens 104 are arranged in this order. The field mask 101 has a cross-shaped transparent hole, and has an objective lens +
The objective lens IO[i
This is to regulate the aerial image of the subject formed by the The field lens 102 uses the aperture 103 as the objective lens 1.
06 exit pupil 108, aperture 103 and exit pupil 10
8 in a conjugate relationship. As shown in FIG. 2, the diaphragm 103 has four sector-shaped openings 03a and 103b symmetrical about the optical axis.

103c and 103d, and the exit pupil 108 of the objective lens 106 is divided into four areas 108a as shown in FIG.
.

It is divided into 108b, 108c, and 108d. The secondary imaging lens 104 has four openings 103a, 103b, 10 of the aperture 103, as shown in FIG.
Four lens parts 104a, 1 corresponding to 3c, 103d
04b, 104c, and 104d, and forms the field mask image 109 on a photoelectric conversion element 105 arranged on the rear side of the secondary imaging lens 104.

Therefore, the light beam incident on one area 108a of the exit pupil 108 of the objective lens 106 is transmitted through the field mask 101, the field lens I02, the aperture 10, and the diaphragm 108 as shown in FIG.
The light passes through the aperture 103d of No. 3 and the lens portion 104a of the secondary imaging lens 104, and forms an image on the photoelectric conversion element 105 as a field mask image 109a as shown in FIG. Similarly, other regions 108 of the exit pupil 108 of the objective lens 106
The luminous flux incident on b, 108c, l08d is shown in Fig. 5 (a
), through the corresponding parts as shown in (b),
As shown in FIG. 6, the visual field mask image 109b, IO! lc
, 109d on the photoelectric conversion element 105. Therefore, the light beam incident on the objective lens 106 is divided into four focus detection optical systems.

The photoelectric conversion element +05 on which the field mask image 109 is formed in this manner has field mask images 109a and +09b.

Pixel columns 105a and 10 corresponding to 109c and 109d
5b, 105c.

105d are arranged in a cross shape, and these pixel rows 10
Each field mask image 109a, l09b, 109c, +09 by 5a, l05b, 105c, 105d
d is photoelectrically converted and taken out as a signal output.

Note that each of the field mask images 109a, 109b, 109
c.

The illuminance distribution of 109d moves in the direction of the arrow relative to the in-focus state as shown in FIG. On the other hand, in a rear-focus state where an object behind the subject is imaged on the expected imaging plane, the object moves in the direction of the arrow relative to the in-focus state, as shown in FIG. 7(b). For this reason, each field mask image 109
The outputs obtained from a, 109b, 109c, and 109d have output waveforms 110, 111, 1 as shown in FIG.
12, 113, 114, and 115 are formed.

That is, FIG. 8(a) shows the focused state, and FIG. 8(b) shows the front focus state, resulting in output waveforms 112 and 113 that are close to the output waveform 110°III of FIG. 8(a). Figure 8 (
In C), the output waveform of FIG. 8(a) in the rear pin state is +10.
Output waveforms 114 and 115 are spaced apart from Ill.

A and B shown in FIGS. 8(a) and 8(b) are the 9th
Each pixel column 105a, 105b, 105c as shown in the figure
, 105d, where A is the pixel column]05a,
105c is a set, and B is a set of pixel columns 105b and 105d.

10 to 15 show a second embodiment of the plurality of divisions of the focus detection optical system constituting the present invention.

In this example, the field mask is 116, the field lens is 102, the aperture is 117, and the secondary imaging lens is 1.
18. A photoelectric conversion element is indicated by 119, and each part thereof is indicated by annotations a, b, c, and d.

The difference from the first embodiment is that the through hole of the field mask 116 is square, and the opening 1t7a of the diaphragm [17].

1] 7b, 117c, and 117d are made into elliptical shapes that overlap by parallel movement, and a prism 1I8e is provided on the rear side of the lens portions 118a, 118b, 118c, and 118d of the secondary imaging lens 118.

1]8f, 118g, ]18h are provided.

In this embodiment, the field mask 116 has a square through-hole because it is easier to manufacture than the cross-shaped one in the first embodiment.

] The reason why 17c and 117d are made into elliptical shapes that overlap by parallel movement is because of the output waveform 11 in FIG. 8 in the first embodiment.
2 , I 13 , 114 , and l 15 have been improved from having a mirror image relationship to have a congruent relationship as shown in FIG.
8 lens parts +18a, 118b, 118c, 118d
Prisms 118e, +18f, l18g, 11 on the rear side of
The reason why 8h is provided is to enable aberration correction. Note that the aperture 1t7a of the diaphragm 117, +17
b, 117c, and 117d are square openings 136a and 136b as shown in FIG.

136c and 136d may also be used. Also, the first
Field mask images 125a, 125b, 125c in Figure 3
, 125d correspond to a, b, c, d of the through holes of the field mask 116 in FIG.

According to the first and second embodiments described above, the plurality of focus detection optical systems are divided into symmetrical positions with respect to the optical axis of the objective lens 106, so that the field masks 109a, 109b
, l09c, l09d, 125a, 125b,
125a and +25d are imaged on the photoelectric conversion elements 105 and 109 with point symmetry about the optical axis, so the illuminance distribution when out of focus has the same amount of movement for each pair of pixel rows A and B, Further, the amount of movement is the same for the sets A and B of pixel columns.

Therefore, the accuracy of the signal output obtained from these is improved,
Calculations based on this signal output will be faster. Output waveform 122°123.124 in the second embodiment
．． 125 has a congruence relationship, which has the advantage of further improving the accuracy of this signal output.

In addition, (the calculation based on the No. 2 output is
This calculation is performed using a method such as No. 06, for example, the following equation, and the amount of defocus of the objective lens 106 can be determined from this calculation result.

That is, ct= (FO/M)z/ (i +FOZ/ (Mg
)].

where, d is the amount of defocus of the objective lens 106, Z is the relative amount of deviation between the two images, M is the imaging magnification of the secondary imaging system, Fo
is the angle of the light beam passing through the center of the divided pupil area or the optical axis of the objective lens 106, expressed as an F number;
g is the distance between the planned imaging plane and the exit pupil 108 plane of the objective lens 106.

In addition to dividing the focus detection optical system according to the first embodiment or the second embodiment, the present invention adds the signal outputs obtained from each focus detection optical system during calculation using the above-mentioned arithmetic expression or the like.

This addition is performed using the photoelectric conversion element 105°119 shown in FIG.
This is done by an equivalent circuit provided in Note that this timing chart is shown in FIG.

This equivalent circuit may be based on a storage image sensor or may have other structures such as CCD, MOS, etc. All MOSs in this circuit are composed of n-channels, and the timing chart indicates that the MOS is HIGH.
The state changes between low [il 0 FF state]. During the clear period, ΦRES is set to High to clear the accumulated charge.

When ΦRES is set to High, the base potential is fixed to GND, and at the same time, CT and wiring equivalent capacitance Cp are also fixed to GND, and a clearing operation is performed. Next, ΦRES is set to Low, and when the storage period begins, ΦR is set to High, so that the base potential is forward biased with respect to the emitter. At this time, if the forward bias voltage is controlled to exceed VBc, a voltage corresponding to the maximum accumulation value of the pixel column is charged, and a potential corresponding to the maximum value of the vp ratio output is output via the source follower SF. . This maximum output increases while the light is on, as shown in FIG. 17, and is monitored to control the VP ratio output accumulation period. At the same time, the emitter potential of each pixel column is charged to CT. This is because ΦT is controlled to be High during the accumulation period. When the output of the monitor reaches VTII, ΦT is controlled to Low and CT is separated from the emitter Es, so that CT
charging stops. The accumulation period ends in this manner, and the charge charged in the CT corresponding to each pixel is the signal output of each pixel. Next, shift register S
Operate R and read the signal output. This shift register SR is a dynamic register, and the start pulse Φ
ST.

Φl, Φ2, and MRn is turned ON during the High period of ΦI.
state, and the charge charged in CT is equivalent wiring capacitance C
) I can be read out in capacitive divisions. That is, the shift register SR is cleared when ΦST becomes High on the timing chart, and the subsequent Φ1. The block Φ2 sequentially opens MRI to MRn and reads out the signal output charged in the CT. During this time, immediately before setting Φl to High, ΦHR5 is set to High, and the equivalent wiring capacitance CH is set to GN.
Fixed to D and cleared.

In the present invention, the pixel columns 105a, +05b, 105c
, l05d.

Alternatively, MRn of sets A and B of 119a, ] 19b, 119c, and 119d are simultaneously opened by shift register SR, and corresponding pixel columns 105a and +05d of sets A and B, 1
05b and 105c, there are) are +19a and 119d,
The A word outputs of 119b and 119C are simultaneously read and added. That is, if the potential charged to the CTI of pixel column set A is Vl, and the potential charged to the CTI of pixel column set B is V2, then the equivalent wiring capacitance CH when the MRI is opened is
The potential of is obtained as follows, and a potential proportional to (Vl +V2) is obtained.

Therefore, regarding the photoelectric conversion element 105 of the first embodiment, as shown in FIG. 18, the output waveform of the pixel column 105a is 130 (C in FIG. 18(a)), and the output waveform of the pixel column 105C is 131 ( D) in FIG. 18(a), pixel row! 05d
The output waveform of the pixel column 105b is 132 (FIG. 18(b) (7) E), and the output waveform of the pixel column 105b is 133 (FIG. 18(b) F).
Then, as a result of addition, the output waveforms 114 of FIG. 18 G and H are obtained.
．． 1:15 is obtained. .

If the summed and combined output waveforms 134 and 135 are calculated to calculate the amount of defocus of the objective lens +06, the amount of defocus of the objective lens +06 is calculated as shown in FIG.
Even if there is a direction with low contrast as in b), focus detection can be performed with high precision, and focus detection can be performed with higher precision than when calculations are performed based on individual signal outputs. This effect is particularly effective when there is no contrast at all in the direction of the subject, such as wr or stripes.

FIG. 19 shows the position of the distance measurement field within the viewfinder field of the camera, where 126 is the Feig field of view, 127 and 128 are the distance measurement fields, and +29 is formed on the focus plate.

Furthermore, the subject image incident on the distance measurement field of view 127 is
5b, l05d, 1] re-imaged on 9b, +19d,
The subject image incident on the distance measurement field of view 128 is a pixel row 105a,
105c.

The image will be re-imaged on 11Qa and 119c.

(Effects of the Invention) As described above, the focus detection device according to the present invention has a plurality of focus detection optical systems arranged at symmetrical positions with respect to the optical axis of the objective lens. The amount of change during focusing is constant regardless of the focus detection optical system, the accuracy of the signal output taken out from the photoelectric conversion element is improved, the calculation speed of the calculation means for calculating the amount of defocus is increased, and the focus detection There is an effect of speed or speeding up. In addition, corresponding I5 of the pixel row of the photoelectric conversion element corresponding to the valley point detection optical system.
Since the signal outputs are added together, 1) the calculation in the rr notation calculation means is simplified, and the speed of focus detection is promoted.

Furthermore, the structure of the present invention has the effect that the feature of effectively exerting a detection function even in a focus detection device having a plurality of focusing optical systems is not inhibited.

[Brief explanation of drawings]

1 to 9 show a first embodiment of the multiple-divided lower stage of the focus detection optical system constituting the present invention, in which FIG. 1 is a perspective view, FIG. 2 is a front view of the aperture, and FIG. The figure is a structural diagram of the secondary imaging lens, Figure 4 is an exit pupil projection diagram of the objective lens, Figures 5 (a) and (b) are divided optical path diagrams of the focus detection optical system, and Figure 6 is a photoelectric conversion element. 7(a) and (b) are simplified diagrams showing the movement direction when out of focus in FIG. 6, and FIG. 8(a), (b), (c) is an output waveform diagram of the signal output extracted from the pixel row of the photoelectric conversion element, No. 9
The figure is a simplified diagram showing the set and arrangement of pixel columns in a photoelectric conversion element, and FIGS.
1 is the same as FIG. 1, FIG. 11 is the same as FIG. 2, FIG. 12 is the same as FIG. 3, FIG. 13 is the same as FIG. 6, and FIG. 15 is the same as FIG. 8. 14 is a diagram showing a modification of FIG. 11, FIG. 16 is an equivalent circuit diagram provided in the photoelectric conversion element, and FIG. 17 is a timing chart of FIG. 16.
FIG. 18 is an output waveform diagram of signal outputs added and synthesized by the equivalent circuit, and FIG. 19 is a diagram showing the position of the distance measuring field of view of the camera. 106...Objective lens +02...Field lens 103.117...Field mask, 103a, 1
03b, 103c. 103d, 117a, +17b, 117c, l]
7d - opening, 104, +18 - secondary imaging lens,
104a, l04b, l04c. +04d, 118a, 118b, 1I8c, 11
8d--lens section, 105, +19-/photoelectric conversion element,
105a, 105b, 105c. 105d, 119a, 119b, 119c, 119d-
- Pixel number patent applicant Canon Co., Ltd.

Claims (1)

[Claims] A device that includes an optical system that forms a pair of object images from a light beam transmitted through an objective lens, and a photoelectric conversion element that receives energy distribution regarding the pair of object images, and detects a focus adjustment state from the output of the photoelectric conversion element, A plurality of sets of the optical system and the photoelectric conversion element are provided with respect to the optical axis of the objective lens,
1. A focus detection device characterized in that the photoelectric conversion element is provided with an equivalent circuit that adds corresponding signal outputs of pixel columns of the photoelectric conversion element corresponding to each focus detection optical system.