JPS6145207A - Focusing detecting device - Google Patents

Abstract

PURPOSE:To reduce the number of photodetecting elements and the quantity of computation and to make a real-time decision by calculating the phase difference between Fourier transform components of incident light images on the basis of output signals from respective photodetecting element arrays of two photodetection parts, and detecting a focusing state. CONSTITUTION:A optical distributing element where luminous flux from an image forming lens 1 is passes while divided into the 1st and the 2nd areas is arranged between the lens 1 and the expected image forming position of the lens 1. Two photodetection parts 200 formed of the 1st and the 2nd photodetecting element arrays which vary in effective photodetection efficiency in a sine and a cosine wave shape and the 3rd uniform photodetecting element array are provided; the luminous flux of the 1st area is incident on one group and that of the 2nd area is incident on the other. Electric output signals of the photodetection parts 200 are inputted to an analog arithmetic circuit 30 to calculate the phase difference between Fourier transform components of the two groups. This phase difference data is sent to a display circuit 40 to display a front focus, in-focus, or rear focus state, and a lens driving circuit 50 is operated on the basis of data on the defocusing extent calculated by the analog arithmetic circuit 30 to drive the lens 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a focus detection device for detecting the focus state of an imaging lens in an optical device such as a still camera, a video camera, or an Mt4 mirror.

(Conventional Technique W) The conventional focus detection device is explained using a camera with a 7-focus camera as an example. As shown in Figure 1, light from a subject 2 passing through a photographic lens 1 is divided into two parts by a movable observation mirror 3,
One of the lights reflected by C is guided to a finder optical system consisting of a seven orcasing screen 4, a pentaprism 5, and the like. Also, a bar 7 formed at the center of the movable mirror 3
The other light that has passed through y-3a is totally reflected by the sub-mirror 6b for focus detection provided on the back side of the movable mirror 3, and this reflected light is divided into a number of points with the center of the reflected light as a boundary. The beam is separated into a first beam and a second beam by a light distribution element 10 which divides the beam into a first area and a second area. The separated first and second light beams are optically transferred to the film 6.
The light is guided to the light receiving section 20 located at or near the position of the planned image forming plane that is conjugate with the 0 plane. The light receiving section 20 includes a first light receiving element array that mainly receives the first light beam separated by the light distribution element 10 and a second light receiving element array that mainly receives the second light beam separated by the same light distribution element 10. It has columns and rows.

Then, the Fourier transform components in the frequency space are determined as a mouse corresponding to the light distribution of the subject group incident on each of the first light receiving element row and the second light receiving element row of the light receiving unit 20, and based on this value. [This is designed to perform focus detection.

That is, the respective outputs of the plurality of light receiving elements forming each of the first and second light receiving element rows are ai and bi, and the outputs ai and bi are amounts corresponding to the light convergence distribution of the subject image. If the Fourier transform component related to the Mochima frequency stone of ai is Aj, then the 7-Flier transform component A is as shown in the following equation.

Here, N is the number of light receiving elements forming the light receiving element array.

Therefore, when the Fourier transform component A1 is used, the Fourier transform component B1 of the output bi of the light receiving element array located at a position displaced by the distance 1111 fo from the same component Aj becomes as shown in the following equation.

bi ''''(i-A6) Therefore, the Fourier transform component B is as shown in the following equation.

= A2 · exp (-2yt-e io/N) The two object images are proportional to each of the relative displacements io of the subject images that are changing relative to each other. Therefore, the in-focus state can be determined by obtaining the 7-lier transform values of each of the two subject images and detecting the phase difference between them.

An example of a method for electrically obtaining a more precise 7-lier transform value is to calculate the output terminals of each of a plurality of light receiving elements forming a light receiving element array, as described in Japanese Patent Application Laid-open No. 54-104859. There is a device that is connected to a circuit and uses the same circuit to determine the 7-lier transform value purely electrically. However, according to this method, it is necessary to use an arithmetic circuit with an extremely complicated configuration, which results in an increase in size, a large amount of calculation time, and lacks real-time performance, making it less practical.

In addition, since the dark current characteristics, sensitivities, etc. of each of the plurality of light-receiving elements forming the light-receiving element array do not completely match, accurate Fourier transform components cannot be obtained.Furthermore, since the area of each light-receiving element is small, the output This method has the drawback that it takes a long time to accumulate charge to obtain the ff number, and as a result, the response becomes poor.

(Purpose) The purpose of the present invention is to detect a shifted image of a subject image, find the Fourier transform component of this lateral shift, and find the phase difference in the frequency space to perform focus detection. It is an object of the present invention to provide a focus detection device that can perform real-time processing using an extremely simple configuration of the light-receiving confectionery fa' without determining the fc component.

(IA required) The focus detection device according to the fJHc of the present invention has a first light-receiving element array consisting of a plurality of light-receiving elements whose effective light-receiving efficiency changes in a sine wave pattern, and a first light-receiving element array in which the effective light-receiving efficiency changes in a cosine wave pattern. A second light-receiving element array consisting of a plurality of light-receiving elements with equal effective light-receiving efficiency and a third light-receiving element array consisting of a plurality of light-receiving elements with equal effective light-receiving efficiency form a set of light-receiving sections m, and this light-receiving section Two sets of light receiving elements are arranged, and the light beams obtained by dividing the luminous flux from the grouping lens into two are incident on each of the two sets. The in-focus state a of the woven lens is detected by determining the phase difference between the Fourier transform components of the optical images incident on the two sets of light receiving sections based on the output signals.

(Example) The present invention will be explained below based on one embodiment.

First, an example of the light distribution element and the light receiving section in the focus detection device according to the present EJAK will be explained in the second section. This will be explained with reference to FIG.

In FIGS. 2 and 3, the light distribution element 100 has a structure similar to that of the focus detection device described in, for example, Japanese Unexamined Patent Publication No. 59-15207. is a band-shaped mask having a width S. Masks 1021 to 102n made of an impermeable film are arranged with a pitch T and 1
One piece is formed.

A light receiving section 200 is provided in close contact with the lower surface of the light distribution element 100 configured as described above. This light receiving section 20
0 has an insulating substrate 201 having approximately the same outer shape as the glass substrate 101, and the mask 102. ~102n first light receiving element array 204. Second light receiving element array 210. A set of light receiving sections consisting of three rows of third light receiving element row 216, first light receiving element row 207. Second
The light receiving element array 213. Two sets of light receiving sections are formed with one set of light receiving sections consisting of the third light receiving element row 21903 rows.

The one set of first light receiving element rows 204 is connected to the mask 10.
1111i1 light receiving elements 202. with a pitch T of 21 to 102n. ~202n are arranged in a straight line parallel to the mask, and the shape of each light receiving element 2021~202n in the parallel direction is calculated by dividing the shape of one cycle of the sine wave into four as conceptually shown in diagram N4. The light receiving elements a to d are arranged repeatedly. These light receiving elements 2
The base end of each of 021 to 202n is a straight connecting part 2
03 is connected. And the first of this set
Each light receiving element 202 . of the light receiving element array 204 . ~202n, that is, between 2021 and 202□.

Between 2022 and 20230, 202. Between 2024 and 2024
Each of the above light receiving elements 202. ~202n and symmetrical light receiving element 205. ~205n are arranged. This light receiving element 205. ~205n is the above connection part 203
are connected by a connection 206 similar to that of the first
A light receiving element array 207 is formed.

The first light-receiving element array 204, 207 and i-screen 1 of each set above.
02, to 102n, as shown in FIG. The first light flux Q1tQ1... of the first region with the light flux plane orthogonal to the formation plane of 102n as the boundary is mainly the light receiving system element 202. .about.202n, and similarly the second
The luminous flux Q2 #Q2... is the main component, and the light receiving element is
The light is trapped so as to be incident on the first light receiving element array 207 formed by 205n.

The set of second light receiving element rows 210 is also formed of n light receiving elements 2081 to 208n and a connecting portion 209 in the same manner as described above. ~208n each shape is the third
As conceptually shown in the figure, light receiving elements A to D are repeatedly arranged by dividing the shape of one period of a cosine wave into four. In addition, each light receiving element 2 of the second light receiving element row 210
08. A light receiving element 211. ~211n are arranged. The shape of the light receiving elements 2111 to 211n is the same as that of the light receiving element 208. ~208n, and each light receiving element 2111~211n is connected by a connecting part 1212 similar to the above connecting part 209, forming a second light receiving element array 213. And the second
The first light beam Q is applied to the light receiving element array 210.

(see FIG. 5) is mainly incident on the second light receiving element array 213, and the second light beam Q2 (see FIG. 5) is mainly incident on the second light receiving element array 213.

Furthermore, one set of third light receiving element array 216 also includes n light receiving elements 214 . ~214n
and the connecting portion 215, and the same light receiving element 2141.
The shapes of ~214n are the light receiving elements 2021~202n.

2051-205n1208. ~208n, 211.
~211n, each having a maximum height of 7, and each having a uniform angular shape. Between each of the light receiving elements 214 to 214n, that is, 214. and 214□0, between 2142 and 21430, 1214. and 2
In the valleys between 144 and 144, the light receiving element 214
1 to 214n, each having the same shape as the light receiving element 217. ~2
17n are arranged symmetrically. This light receiving element 217
．． ~217n are connected by a connection part 218 similar to the connection part 215 described above, and are connected to the third light receiving element array 2 of the other set.
It is now 19. The first light beam Q, (see FIG. 5) is mainly incident on the third light-receiving element array 216,
The second light beam Q2 (see FIG. 5) is mainly incident on the third light-receiving element array 219.

Note that the connection portion 203.2 (16, 209, 212,
The width of each of the connecting portions 215 and 218 is kept narrow so that the light incident on the connecting portions 203 . . . can be substantially ignored.

In addition, the first to third light receiving element rows 204, 207°2
10. The width of 215, 216, 219 in the column direction is preferably as small as possible, preferably about 1 mm, and the width in the direction perpendicular to the column direction is such that the width of the first light receiving element array 204, 207 is about 100 μm. 2 light receiving element rows 210, 213
The width of the third light receiving element array 216, 2 is approximately 100 μm.
The width of 19 is preferably 50 μm @ degree. This is to create a position where the amount of light from the subject can be considered to be approximately the same. In addition, each connection portion 206, 206, 209, 21
From 2°215.218, each light receiving element row 204, 207,
210, 213, 216° and 219 light receiving outputs can be extracted.

In order to perform focus detection based on the output of the light receiving section 200 that has received the luminous flux divided by the light distribution element 100, the electric output signal from the light receiving section 200 is subjected to analog calculation as shown in the bx diagram in FIG. It is input to the circuit 30, and the phase difference of 12 sets of Fourier transform components is determined by the circuit 30. This phase difference data is sent to the display circuit 40, and the display circuit 4 displays the front bin, in-focus, and rear bin. Furthermore, the lens driving circuit 50 operates based on the defocus data obtained by the analog calculation circuit 30, and the fine woven lens 1 can be driven.

Light receiving elements 202-202, 205. The effective width 1 n Wlls of ~205n is expressed as W2B = 1 + sin (2πfo a: ) using the longitudinal seat w4x of the first light receiving element rows 204, 207.

Similarly, the light receiving element 208. ~208n, 211. ~21
Effective width W of 1n. 0 is the second light receiving element array 210, 213
Using the coordinate X in the longitudinal direction, it is expressed as W, c= 1 + Cog (2πfo s ).

Note that fo is each light receiving element array 204, 207, 210,
Each light receiving element 202 to 202 in each of 213,
205. ~1 n 205n, 2081~208n, 211. ~211
It represents the frequency of a sine wave or cosine wave divided into four at n.

Therefore, when the leading edge formed on the N1 light receiving element rows 204 and 207 is photoelectrically converted, the electrical output represents the Fourier transformed component of the same amount of light. Then, the light amount distribution of the amount of light formed on each light receiving element row 204 and 207 is adjusted. a(x)-I. b(&), and the electrical output Poa(s) of each light receiving element array 204, 207, POb(
s) is as shown in the following formula.

Poa(s) = f engineering. a(ri ・(1+sin
(2rf(, a: month dxx J' i., (s) dg
+J'I. a(J) esin (2yr fo”)
dg ””(1)Pob(s) = f ”ob □・
(1+sin (2rr, ”))d”=J'I.

b(J)dz+J'I. b(g)-sin(2gfoa
:) ds −, −(2).

The second term in the above equations (1) and (2) is the frequency f.

is the sine wave component of the Fourier series transform component in .

However, the first term in equations (1) and (2) above is a term that is not a Fourier variation component and represents the total optical cover of the amount of light.

In order to remove this term, the third light receiving element array 216.21
9 is crossed out. The fifth light-receiving element row 216, 2
Each light receiving element 214 at 19K. ~214n, 217
Since the light-receiving area between ゜ and 217n is constant, the third
Electricity output P of each of the light-receiving element arrays 216 and 219. a
(F)tPOb(F) is expressed by the following formula.

POb(F):==f-ob(idx...(4)
Therefore, by estimating the above equation (3) from the above equation (1), in other words -P, then P. a, 8). 2(F), it is possible to obtain only the sine wave component of the Fourier transform component.

In addition, the cosine wave component of the Fourier transform component can also be obtained from the single output of the second light receiving element array 210, 213 and the third light receiving element array 216, 219 in the same manner as described above.

And distribution work to the light. a(-f) and engineering. b (3) match when in focus, and as the focus shifts, the light amount distributions shift toward opposite sides in the uniaxial direction.

This is how it works. If the sine wave component and cosine wave component of the Fourier series transform components for the two optical images with b < sr are found, the relative displacement amount of the two object edges in the χ axis direction can be found It will be done.

Next, the relative x of the edges of the two objects when they are in an out-of-focus state
@ direction deviation? An example of how to obtain o will be explained.

11 First to third light receiving element rows 204, 210
, 216. b(3:) is x, bG''J = Ioa (
x so ).

Therefore, the Fourier transform component A(fQ) at the frequency fo, which is determined by the electrical outputs of the first to third light-receiving element arrays 204, 210° 216, is expressed by the following equation.

A(fo)"J'"□B(")" eXp (-i
2πf,,z=) -----(5) Also, the Fourier transform component B(fQ) at the frequency f0 determined by the electrical output of the first to third light receiving element arrays 207, 213°219 is expressed by the following equation. Goes to 5.

B(1o) = ffob (g) ・exp (-t
2 x fox ) Therefore B((o) ” A(f,) eXp (-12KfO
&, ) @--- (6). From [above (5)
) is divided by the above equation (6) to obtain the phase difference φ between the two. is φ. It is found as =2π'o”o.

Here, the phase difference φ. This is because, as shown in FIG. 7, is obtained as the arctangent of the imaginary term Im divided by the real term. Therefore, the offset ta-0 is zo=φ. /2πf, −@---(8).

Furthermore, if the P number of the imaging lens is known and F is the aperture value), then the defocus amount of the imaging lens 2° can be obtained as Z = 2F, Z-o---(9) . Therefore, from the output of each photodetector array, the above formula (force (
8) By performing the calculation in (9), the amount of defocus can be determined directly during the process.

In addition, if the F number of the finely woven lens is not known, the size of the exit pupil image incident on the light receiving section is detected using the F number detection method described in JP-A-58-218613, for example. Then, after finding the F number from K, it is a good idea to find the defocus Ikzo from the above equation.

In the above embodiment, the 7-Liere series transform component at a single frequency is determined in step 5, but since the spatial frequency based on the light image from the subject is over a very wide range, it is difficult to obtain an accurate calculation. Focus detection may become impossible. For this purpose, the first to third light receiving element arrays 20
4,207,210,213,216゜219 By changing the pitch of the light receiving element arrangement in VC, that is, by changing the 1# period of the sine wave and cosine wave, we created a process to create a 7- By determining the y-secondary transform component, focus detection can be performed over a wide range of spatial frequencies based on the light image from the subject.

Further, the arrangement of the light receiving elements forming the light receiving element array is not limited to the arrangement in the above embodiment, but may be configured as shown in FIG. That is, a mask 102. The light-receiving element rows arranged on the lower surface of the light distribution element 100 on which the elements 102o to 102o are formed are arranged as follows. A plurality of light-receiving elements 202 each having a light-receiving surface having a sine drum shape divided into four parts. ~202n and the connection portion 206, and this first light receiving element array 2.
Each light receiving element 202. A plurality of light receiving elements 205 .
~ 205n and the connecting portion 206, and the first light receiving element array 204, 207.
Similarly, the second light receiving element rows 210, 215 are divided into light receiving elements 208. ~
208n and the connection part 209, and the light-receiving elements 2111 to 211n having a light-receiving surface divided into four parts having a cosine wave shape and the connection part 212, and the third light-receiving element array 216
．． 219 is a light receiving element 214 having a uniform light receiving surface. ~2
14n and the connecting portion 215, and the light receiving element 214. ~
214n, the light receiving elements 217.n have uniform light receiving surfaces facing each other in a comb pattern. 217n and the connecting portion 218.

Therefore, in this example, the total width of @1 to the third light-receiving strand arrays 204, 207, 210, 215, 216, and 219 can be shortened, so the light-receiving surface can be used effectively, and the overall size can be made smaller.

In the above embodiment, the shape of the sine wave or cosine wave light receiving element is formed to have the same shape as a part of the sine wave or cosine wave, but as shown in FIG. Determine the width of the light receiving element using the representative sampling value,
The light-receiving elements a to d may have rectangular shapes with different widths, and the light-receiving elements A0 to Do may have different widths, respectively, as shown in FIG. 11 for cosine waves as well.

On the above valley side, each light receiving element 202. ~202n#
205-205, 208-208. 211.
~211n form 1 n f
Although each flJ shape is different,
As shown in FIG. 12, the light-receiving surfaces of the light-receiving elements 2021 to 202n, pots, etc. formed on the upper surface of the 5Kfe edge substrate 201 are formed in the same rectangular shape, and the light-receiving surfaces of the light-receiving elements 2021 to 202n formed on the upper surface of the 5Kfe edge substrate 201 are formed in the same rectangular shape. The distribution element 100 is shown in FIGS. 13(A) to 13(C).
In other words, as described above, the upper surface of the glass substrate 101 is covered with a mask 102. ~102n is formed on the bottom surface of the glass substrate 101! 5 mask 5 as shown in Figure 15 (C)
00 is formed. Light receiving element 20 of the same mask 300
2. The light receiving element 20 is located at a position corresponding to ~202n.
21 to 202n are each divided into sinusoidal openings 30
1. ~301n, and the light receiving elements 2051 to 205
The opening 601.n is also located at the position corresponding to the opening 601.n. Opening 302.~301n similar to .~301n. ~302nC. In addition, the light-receiving cable 208. ~208n, 211. ~211n, the same light receiving elements 208~208, 2
11. Cosinusoidal Sekiguchi 303° to 303n, 304.corresponding to 1 n 211n, respectively. ~604n exists. Furthermore, the light receiving cable 214. ~214n, 217. ~217n
A strip-shaped opening 305 is provided at a position corresponding to .

Therefore, each light-receiving strand 202. ~202n... Since only the necessary light receiving surfaces are exposed and the other parts are shielded from light, disturbance light, internal reflection, etc. can be prevented. Also, in the above example, the openings 3011 to 301n.

302, ~302n, 3051~503n = 30
4. ~304n, mask 300 instead of providing 305
It is also possible to partially change the transmittance of the light-receiving strands so that the substantial light-receiving efficiency of each light-receiving strand becomes equal in the form of a sine wave or a cosine wave.

Furthermore, the arrangement of the first to third light-receiving element arrays is not limited to a linear arrangement, but may of course be formed, for example, in an arcuate arrangement.

Furthermore, as a light distribution element, Japanese Patent Application Laid-Open No. 58-59418
The focus detection device described in the Japanese Patent Publication No. 57-49841, in which minute Grimems are formed in a row,
It is also possible to use a seven-eye lens formed in a row, such as that used in the distance determining device described in the above publication.

(Effects of the Invention) According to the present invention, the in-focus state can be detected with a small number of light-receiving probes and a small amount of calculation, and the amount of defocus at that time can also be calculated with a simple calculation. In addition, since multiple light-receiving elements are used in parallel to form a light-receiving element row, a large amount of light reception output can be obtained, making it possible to perform more accurate focus detection and integrating each light-receiving element. Since there is no need to extract the output in a format, the in-focus state can be determined in real time, resulting in extremely responsive detection.

[Brief explanation of the drawing]

! ! Fig. 1 is a schematic diagram showing an example of the configuration of a focus detection device for a 7-eye lens camera, and Fig. 2 is an enlarged plan view of a detection section of a focus detection device showing an embodiment of the present invention. , FIG. 3 is an exploded perspective view of the focus detection section shown in FIG. Figure 11 is a partially enlarged view for explaining the arrangement relationship between the light receiving elements and the mask, Figure 3 is a line drawing for explaining the shape of the light receiving elements forming the light receiving element array, and Figure 7 is for explaining the phase difference. Diagram for. FIG. 8 is a block diagram for explaining an example of the operation of the focus detection device of the present invention, 1. FIG. 9 is an enlarged view showing another example of the focus detection section in the focus detection device of the present invention. A plan view, FIGS. 10 and 11 are diagrams showing other shapes of light receiving elements forming a light receiving element array, and FIGS. 8g and 12 are diagrams showing focus detection in a focus detection device showing another embodiment of the present invention. Enlarged plan view of the section, Fig. 13 (A) (B
)(C) are a plan view, a front view, and a bottom view of the light distribution element used in the focus detection section of FIG. 12 above. 1.φ.......Imaging lens 10.100...ψΦ light distribution element 20.200.e...Fist light receiving section 202-202.205. ~205. , 2081-2
08n, 211. 〜1 n 211.214〜214.217〜217 ・・Work Φ
ΦPhotodetector fllf11f1 204.207...First photodetector array 210.2
13-... ■Second light-receiving element row 216.219.O...
・Third light-receiving element row 102-102...Mask 1 n 30......Analog arithmetic circuit (straight true circuit) Figure %10 Figure %11 Procedural amendment (self-proposed) September 1982 18th of the month

Claims (1)

[Scope of Claims] A light distribution element that divides the light beam from the imaging lens into a first region and a second region and passes the light beam is provided between the imaging lens and the planned imaging plane of the imaging lens. a first light-receiving element row made up of a plurality of light-receiving elements whose effective light-receiving efficiency changes in a sinusoidal manner; and a second light-receiving element array made up of a plurality of light-receiving elements whose effective light-receiving efficiency changes in a cosine-wave manner. A third element array consisting of a plurality of light-receiving elements with equal effective light-receiving efficiency.
two sets of light-receiving sections formed by a light-receiving element array, and the light flux from the first region is mainly incident on one set of light-receiving sections, and the light flux from the second region is mainly incident on the other set of light-receiving sections. As shown in FIG. An arithmetic circuit is provided that calculates the phase difference between the Fourier transform components of the optical images incident on the two sets of light receiving sections based on the signal, and the in-focus state of the imaging lens is detected based on the output of this arithmetic circuit. A focus detection device characterized by: