JPS63291040A - Illuminating device for detecting focus - Google Patents

Abstract

PURPOSE:To attain the detection of focus on an optical axis and out of the optical axis by curving a projection pattern corresponding to the astigmatism characteristic of a light projecting lens in order to agree the focusing position of a projection pattern image. CONSTITUTION:An illuminating device includes a light source 4, the projection pattern 21 arranged just before the light source 4 and the light projecting lenses 3 and 20 which project the projection pattern 21 on an object and the projection pattern 21 is formed to be curved corresponding to the astigmatism characteristic of the light projecting lens 3 in order to agree the focusing position of the projection pattern image on the object on the optical axis and out of the optical axis. Namely, focusing position of the projection pattern image projected on the object is agreed both on the optical axis and out of the optical axis. Thus, the detection of focus is always attained on the optical axis and out of the optical axis even if the focus detecting area on the object is altered according to the length of the focal distance of a used photographing lens 1.

Description

Detailed Description of the Invention [Industrial Application Field] This invention relates to focus detection used in a camera equipped with a TTL focus detection device that detects the focus adjustment state of a photographic lens using incident light passing through the photographic lens. The present invention relates to a lighting device for use.

[Conventional technology]

When performing focus detection using a TTL type focus detection device, focus detection becomes difficult or impossible when the subject is dark or the contrast of the subject is low. In such cases, focus detection is aided by illuminating the subject with a lighting device attached to the camera, or by projecting a projection pattern built into the lighting device onto the subject to provide contrast. (See, for example, Japanese Unexamined Patent Publication No. 138222/1982).

[Problem that the invention seeks to solve]

In a focus detection device that has a so-called multi-division focus detection area, in which the focus detection area is provided not only near the optical axis of the photographic lens but also at a position away from the optical axis, the The position of the focus detection area outside the optical axis changes. With R1, wide-angle lenses shift further in a direction off the optical axis, and telephoto lenses shift closer to the optical axis.

Therefore, a focus detection illumination device suitable for a focus detection device having a multi-divided focus detection area is one that can illuminate a wide range of objects from near the optical axis to off the optical axis and can project a focus detection projection pattern. However, conventional focus detection illumination devices do not take into account the focus position of the projected pattern image off the optical axis.

Therefore, when designing a light projection lens in consideration of the focus position of the projection pattern image off the optical axis, if the light projection lens is composed of a single lens, it is necessary to make one or both surfaces of the lens aspherical. Although it is possible to reduce aberrations to a level that causes no practical problems, it is not possible to reduce both spherical aberration and astigmatism at the same time. When the spherical aberration is large, the pattern projected onto the subject becomes obscured and cannot be used for focus detection. In addition, when astigmatism is large, the focused position of the projection pattern differs between on the optical axis and off the optical axis, so there is a problem that the range of object distance mi that can provide contrast differs depending on the projection pattern. will occur.

In addition, although it is possible to reduce both spherical aberration and astigmatism by configuring the projecting lens with multiple lenses, it has the disadvantage of complicating the structure, increasing the size, and increasing costs. However, I was unable to hire him.

[Means for solving problems]

This invention curves the projection pattern in accordance with the astigmatism characteristics of the projecting lens, and matches the focus position of the projection pattern image on the subject not only on the optical axis but also off the optical axis, making it possible to detect the focus. The range is the same both on and off the optical axis, and multiple focus detection areas are set on the optical axis of the photographing lens and off the optical axis, and focus detection is performed using light passing through the photographic lens. In a focus detection lighting device suitable for a camera equipped with a focus detection device that performs The projection pattern is configured in a curved shape corresponding to astigmatism characteristics of the projection lens so as to match the focus position of the projection pattern image on the subject on the optical axis and off the optical axis. It is.

[For production]

Since the projection pattern image projected onto the subject is in focus both on and off the optical axis, the focus detection area on the subject changes depending on the focal length of the photographic lens used. However, focus detection is always possible both on and off the optical axis.

〔Example〕

The present invention will be explained in detail below. Figure 1 is a diagram explaining the principle of an active automatic focus detection system (hereinafter referred to as active AP) that projects focus detection illumination light from the camera side toward the subject and performs focus detection based on the reflected light from the subject. Reference numeral 1 designates a photographing lens that is replaceably attached to the camera body, 2 a focus detection module provided within the camera body, 4 an auxiliary illumination light source for focus detection, and 3 a floodlight lens. Illumination light emitted from the auxiliary illumination light source 4 is collected by the projection lens 3 and projected onto the subject. The width of the projected light beam at that time is 6a.

61]. On the other hand, 5a and 5b are active A,
This shows the focus detection range of F. Out of the light reflected by the subject, the light in the range not shown in 5a and 5b passes through the photographic lens 1 and forms an image on the focus detection module 2. used for.

FIG. 2 shows the appearance of a camera incorporating an active AP based on the above principle, and the camera body 10 is provided with a window 12 for projecting auxiliary illumination light onto a subject.

FIG. 3 is an explanatory diagram of the configuration of a focus detection optical system having a plurality of focus detection areas. In FIG. 3(a), reference numeral 11 indicates a photographing lens, and 100a to 100d indicate regions on the pupil plane of the photographing lens 1 through which the focus detection light flux passes. 1
．． 01 is a focus detection area mask placed immediately after the expected focal plane (not shown) of the photographic lens, and as shown in the figure, it has three apertures 101. a, 101b.

101c are provided, and these determine three focus detection areas on the photographic screen. The aperture 101b is provided approximately at the center of the photographing screen, and the aperture 101b is
c is provided in an area other than the center of the photographic screen. These three openings 1.01a, 101b.

The shape of the aperture 101c is a rectangle, and the aperture 101b is arranged in the center of the imaging screen with its longitudinal direction facing left and right, and the apertures 101a and 101C are parallel to the lateral direction of the aperture 1.01b, that is, the aperture 101b and They are arranged at symmetrical positions with respect to the optical axis OL of the photographic lens in a direction forming a right angle. Note that this arrangement shows one example, and is not limited to this.

102a, 102b, and 102c are the openings 1.01a, respectively.

A condenser lens placed immediately after 101b and 101c, and aperture mask openings 1033 to 1033 to be described later.
03f on the exit pupil plane of the photographing lens 11. Reference numeral 103 denotes an aperture mask in which six aperture mask openings 1038 to 103f are provided. The aperture mask apertures 103a and 1.03b are condenser lenses, and the aperture mask apertures 100a and 100b form images on the exit pupil plane of the photographic lens 1.02b, respectively.
3c and 103d are 100d and 100c, respectively, on the exit pupil plane of the photographing lens 11 by the condenser lens 102a.
The aperture mask apertures 103e and 103f form images 100d and 100c, respectively, on the exit pupil plane of the photographic lens 11 by the condenser lens 102c. In this way, the aperture mask apertures 103a-1, 03f function to determine the focus detection light flux area within the exit pupil plane of the photographing lens 11.

Immediately after the aperture mask 103, an imaging optical member 104 as shown in FIG. 3(b) is arranged, and the imaging optical member 1
04 is formed with six imaging lenses 104a to 104f, each with an aperture mask aperture 103a to ]03f.
is placed in the optical path of the These imaging lenses 10
4a to 104f are sensors 106a and 106b of a focus detection light receiving unit 106, which will be described later, and whose images are formed near the focal plane.

This is for re-imaging onto 106c.

Reference numeral 106 denotes a focus detection light receiving section, which is composed of one-dimensional sensors 106a, 1061), and 106c such as COD.

The sensor l06a includes an imaging lens 104a, 104. A sensor I06b is placed at a position to receive the image formed by b.
is located at the position where it receives the image formed by the imaging lenses l04e and 104f, and the sensor 106c is located at the position where the imaging lens 104f receives the image formed by the imaging lens 104e.
．． c and 104d. That is, these sensors 106a,
1061) and 106C are aperture mask aperture 1, respectively.
．． 03a and 103b, 103c and 103d, 103
e and 103f are arranged along the same direction, for example, an image formed through the aperture mask aperture 1.03a and an image formed through the aperture mask aperture 103b. Since the image is formed on the standard part and the reference part on the sensor 106a, the in-focus state of the photographic lens can be detected by finding the correlation between the outputs of the standard part and the reference part.

The arrangement direction of aperture mask openings 103a and 103b is opening 1.
An aperture mask opening 103 is provided along the longitudinal direction of 01b.
c and 103d are arranged in the longitudinal direction of the aperture 101a, and the aperture mask apertures 103e and 103f are arranged in the longitudinal direction of the aperture 101C, so the direction of the sensor 106a and the sensor 106b are and 106c by 90°. sensor 106
Since sensors 106b and 106c are arranged in the horizontal direction, they have a focus detection ability for subjects with contrast in the horizontal direction, and sensors 106b and 106c are arranged in the vertical direction, so they have a focus detection ability for subjects with contrast in the vertical direction. It has focus detection ability.

FIG. 4 shows a viewfinder field image of the camera, where 200 indicates the entire photographing screen, and 200a.

Areas indicated by 200b and 200c are focus detection areas, and sensors '106a, 106b, 106c
Compatible with the light receiving surface.

Next, an embodiment of the light projection optical system of the present invention will be described.

FIG. 5 is an explanatory diagram of the configuration of the light projection optical system, and FIG. 6(a)
is an XY plane view of the projection optical system shown in Fig. 5, and Fig. 6 (
1)) is the same (XZ plane cross-sectional view is shown. In these figures, 20 is a light projection lens, 21 is a projection pattern formed on a curved surface, 22 is a light emitting part, and three light emitting diodes (1) are shown. JED) 26.27.28 and a cup frame 29°3o provided behind it and equipped with a reflective surface that efficiently guides the light emitted from the LED to the condensing lens.
:n, and a condensing lens 2 provided in front of L E D
3.24.25. The projection pattern 21 has a light-transmitting part and a non-light-transmitting part, and projects the pattern onto the subject to provide a contrast of brightness and darkness. Also, what about the projection lens 20? One surface forms an aspheric surface that reduces spherical aberration, and one surface is a spherical surface. Note that it is also possible to make the I) surface an aspherical surface and the 8th surface a spherical surface, or to make both a and b aspherical surfaces to reduce spherical aberration.

The details of the structure of the light emitting section 22 will be explained with reference to FIG. LEDs 26, 27, 28 are spaced wider than this.
+Δl apart. The reason why the spacing between the LEDs is wider than the spacing between the condensing lenses is to prevent a drop in illuminance for objects off the optical axis. If they are arranged, the light projected from the center of the luminescent agent is within the optical path range shown in mm', but if the L E D is arranged at an interval l + Δl that is wider than the arrangement interval l of the condenser lens. In this case, the light projected from the center of the luminescent material falls within the optical path range indicated by U', and the projected range becomes wider than in the previous case.

FIG. 8 shows changes in the illuminance on the subject when the difference Δl between the distance between the condenser lens and the LED is changed.

In other words, when Δl is 20, the illuminance of part a of the focus detection area on the subject, which corresponds to the left and right focus detection areas used when a short focal length photographing lens is attached, decreases and the focus is Although it becomes undetectable, Δl=0.
When it is set to 2 mm, the illuminance 1 of portion a does not decrease (and focus detection becomes possible).

Next, a configuration in which the projection pattern 21 is a curved surface will be described. The astigmatism of the light projecting lens 20 exhibits aberration characteristics as shown in FIG. 9, for example, and as the distance from the optical axis increases, the astigmatism changes from the sagittal direction (DS direction) to the meridional direction (1) Y direction).
aberration increases. This means that the projection pattern can be changed to 2 in Figure 6.
When the projection lens is formed on a plane as shown by 1', this means that the focused position of the projection pattern on the subject differs between on the optical axis of the projection lens and outside the optical axis. 1st
Figure 0 shows the case where the projection pattern is on the plane and the projection lens 2o.
This is an explanation of the focused position of the projection pattern when the projection pattern is curved according to the amount of astigmatism, and is a point on the optical axis. When the projection pattern is in focus in , the position in focus when the projection pattern 21 is a plane shifts as shown by the dotted line q as the distance from the optical axis increases. A solid line p shows a case where the projection pattern is curved in accordance with the amount of astigmatism of the projection lens so that the in-focus position does not shift. In other words, the position in focus on the light ifl+.

If focus detection is possible using the projection pattern projected onto the subject in the distance range r from L1 to L2 in front and back of the center, if the projection pattern is curved as explained earlier, it will be off the optical axis. However, when the projection pattern is a plane, focus detection is possible in the distance range t from L+' to L2' outside the optical axis. However, focus cannot be detected in the range U from Ll to L12.

Therefore, in the present invention, the projection pattern is curved in accordance with the amount of astigmatism of the projection lens, thereby eliminating the shift in the focus position on the subject on the optical axis or off the optical axis. Note that the astigmatism characteristics of the lens differ between the sagittal direction (DS direction) and the meridional direction (DTY direction), but it should be selected according to the contrast detection direction of the distance measurement area off the optical axis.
For the focus detection device shown in FIG. 3, the sagittal direction is appropriate. Furthermore, in the Z direction, the height of light rays off the optical axis through which they pass is not very high in the Y direction and is not greatly affected by astigmatism, so there is no need to curve the projection pattern. To explain this using Figure 4, which shows the viewfinder field image, the height ΔZ in the Z direction from the optical axis is smaller than the height ΔY in the Y direction from the optical axis, so the projection pattern is the astigmatism of the projection lens. Although it is not greatly affected by aberrations, ΔY is affected by astigmatism, so it is necessary to curve the projection pattern in the Y direction.

Next, the projection pattern will be explained. FIG. 11 shows an example of a projection pattern, in which the four parts indicate light-opaque parts and the white parts show light-transmissive parts. Further, when the focus detection area on the subject by the focus detection device shown in FIG. 3 is projected inversely onto the projection pattern, the position is, for example, focal length f = 28
When a mm wide-angle lens is attached, the areas A, B, and C are indicated by dotted lines in the same figure, and the focus detection areas A and B on both sides are the striped pattern 4 of the projection pattern, respectively.
42.43. Visit and 45.46. , 47, 48, and the focus detection area C in the center can be detected by the contrast of brightness and darkness formed by the thick striped patterns 50, 51 of the projection pattern. Center focus detection area C
includes thin striped patterns 52 and 53 in the projection pattern, but the frequency is too high for the focus detection area C and cannot be resolved, making it impossible to form a contrast that allows focus detection.

Next, when a telephoto lens with a focal length f = 100 m77L is attached, the positions of the focus detection areas are areas A', B', and C' indicated by dashed lines in the figure, and the focal points on both sides are Detection area A1. 'f3/ enables focus detection by the contrast of brightness and darkness formed by the narrowed central portions of the striped patterns 42 and 46 of the projection pattern, respectively. The focus detection area C' in the center enables focus detection by contrast of brightness and darkness formed by thin striped patterns 52 and 53 of the projection pattern.

As a result, it is possible to provide a contrast that allows focus detection to the focus detection areas on both sides even for a photographic lens having a longer focal length. Furthermore, the striped pattern 5 on the projection pattern
5.56.57.58 is due to the variation between the focus detection receiver optical system and the light projection optical system (see Figure 2) located diagonally above it, and the difference between This is a projection pattern provided in response to changes in the position of the projection pattern image projected onto the focus detection area of .

FIG. 12 shows the second side of the projection pattern, which has a polka dot pattern instead of a striped pattern.

By arranging a pattern with a small diameter near the center and a pattern with a large diameter near the periphery, it is possible to provide a contrast that allows focus detection according to the length of the focal length of the photographic lens.

Note that the center circle mark 61 indicates the center of the projection pattern and is used for position adjustment and the like.

As explained above, when forming a projection pattern, a pattern with fine dimensions is placed in the center of the projection pattern to suit a taking lens with a long focal length, and a pattern with large dimensions is placed in the outer periphery of the projection pattern. By adapting this to a photographic lens with a short focal length, it is possible to obtain a lens that can provide sufficient contrast for focus detection to various types of photographic lenses, from lenses with long focal lengths to lenses with short focal lengths.

The drive means for the focus detection illumination device described above is not directly related to the present invention, so only an outline thereof will be provided. That is, a camera equipped with the focus detection illumination device of the present invention is equipped with an automatic focus detection system, which includes a photometry circuit for measuring subject brightness, an arithmetic control circuit, and a focus detection illumination device of the present invention. An LED drive circuit is provided to drive the lighting LEDs. The subject brightness measured by the photometric circuit is input to the arithmetic control circuit, and if it is determined that the brightness is lower than a predetermined reference level and that auxiliary lighting is necessary, a lighting signal is output to the lighting LED, and the lighting L
The configuration is such that the ED is lit. For details, please refer to the patent application filed by the applicant on September 27, 1986.
No. 229313.

In addition to being built into a camera, the focus detection illumination device of the present invention can also be built into an accessory such as a light emitting device that is detachable from the camera.

[The power of invention! ! , :1 As explained above, the present invention adjusts the projection pattern by adjusting the astigmatism of the projection lens so that the focus positions of the projection pattern images projected on the subject on the optical axis and off the optical axis coincide. Since it is curved according to the characteristics, even if the focus detection area on the subject changes depending on the focal length of the photographic lens used, focus can always be detected both on and off the optical axis of the photographic lens. , the multi-segment focus detection device can function effectively even under auxiliary illumination light.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of an active type automatic focus detection system, FIG. 2 is a perspective view of a camera incorporating the active type automatic focus detection system, and FIG. 3(a). (1)) is an explanatory diagram of the configuration of the focus detection optical system, Figure 4 is a diagram showing the viewfinder field image, Figure 5 is an explanatory diagram of the configuration of the light projection optical system, and Figures 6 (a) and (b) are respectively 7 is a sectional view of the light emitting part of the projection optical system in the XY plane and the XZ plane, FIG. Astigmatism characteristic diagram, 10th
The figure is an explanatory diagram of the focused position of the projection pattern when the projection pattern is curved and flat, and FIGS. 11 and 12 are plan views of the first and second embodiments of the projection pattern. 20: Projection lens, 21: Projection pattern, 22: Light emitting section,
23, 24.25: Condensing lens, 26.27.28
: LED. (b) Figure 6

Claims (1)

[Claims] In a focus detection illumination device suitable for a camera equipped with a focus detection device that has multiple focus detection areas set on and off the optical axis of the photographic lens and performs focus detection using light passing through the photographic lens. The device includes a light source, a projection pattern placed immediately in front of the light source, and a projection lens that projects the projection pattern onto a subject, and the projection pattern has a focus position of the projection pattern image on the subject on and off the optical axis. 1. An illumination device for focus detection, characterized in that the illumination device is configured to have a curved shape corresponding to astigmatism characteristics of a projection lens so as to match the astigmatism characteristics of a projection lens.