JPH03179410A - Projection system for automatic focus detection - Google Patents

Abstract

PURPOSE:To project a pattern on the entire area of the principal part of a photographic picture plane and to enable highly accurate focus detection at many points in the photographic picture plane by specifying the pattern of a light emission part and the constitution of a lighting system and a projection means. CONSTITUTION:The specific pattern 2 is projected on a subject side by the projection means 1 and its reflected pattern image is photodetected by a photodetection system to detect the focus of a photography system. Then the projection means has (n) lens parts 11 - 14 which are arranged having their optical axes on the same plane and are nearly equal in refractive index and 0.36<phipXnXd and phipXd<S/(f+delta) hold, where phip is the refracting power of the lens parts, (d) the peak interval of the lens parts, (f) the focal length of the lens parts, delta the air converted optical path length from the pattern to the light source 3 of the lighting system, and S the length of the light source in the plane containing the optical axes of the lens parts. Consequently, the pattern is projected on the wide-range subject with excellent image forming performance and distance measurement is performed at, specially, plural points on the subject with high accuracy.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a light projection system for automatic focus detection suitable for photographic cameras, cine cameras, video cameras, etc. We aim to expand the distance measurement range in passive and active automatic focus detection, which is suitable for detecting the focus of a shooting system by projecting light toward the side and receiving the pattern image reflected from the subject side. The present invention relates to a light projection system for automatic focus detection that is designed to improve focus detection accuracy.

(Prior Art) Conventionally, two types of focus detection methods have been used in photographic cameras, cine cameras, video cameras, and the like.

One is the passive method proposed in, for example, Japanese Patent Application Laid-open No. 54-159259, and the other is the passive method proposed in, for example, Japanese Patent Application Laid-Open No.
Sushi Tiht proposed in Publication No. 7-154206 etc.
Among these, the active method detects focus by projecting, for example, an infrared beam from the camera side toward the subject and receiving the reflected beam from the subject. It has the advantage of being able to perform focus detection with high accuracy even when the contrast is low. However, when the subject is far away, the amount of reflected light flux decreases, resulting in a decrease in focus detection accuracy.

The passive method is a method that detects focus by detecting the imaging state of the subject image by the i-tip thread using a detection means installed in a part of the camera, and even if the subject is far away, it can focus at a relatively high degree of 1rr. It has the advantage of being detectable. However, there is a drawback that the focus detection Irr degree decreases when the subject side is dark or when the contrast of the subject is low.

One method to improve this drawback is, for example,
This is proposed in Publication No. 10. In this publication, a fixed pattern is projected from the camera side toward the subject using a light projection system.
We have proposed a so-called pattern projection type automatic focus detection device that detects the focus of a photographing system by detecting a reflected pattern image from an object with a detection system on the camera side.

On the other hand, among recent automatic focus detection apparatuses, various so-called multi-point distance measurement type focus detection apparatuses have been proposed, which perform distance measurement by selecting any one point from among a plurality of points within a photographic screen. The above-described pattern projection method can also be used as an effective method in this multi-point distance measurement type focus detection device.

Generally, in a multi-point distance measuring type focus detection device, it is necessary to simultaneously project a pattern onto a wide range of areas on a subject.

(Problems to be Solved by the Invention) Generally, there are various methods for simultaneously projecting a pattern onto a plurality of areas serving as distance measurement points over a wide range of subjects.

For example, there is a method of using a large pattern and projecting it over a wide range using a light projection system.

However, this method requires the use of a large light source to illuminate the pattern to ensure even illuminance, and the aberrations of the projection system must be well corrected over a wide angle of view, making it difficult to use the entire projection system. There was a problem with increasing the size.

There is also a method of projecting a fine pattern using a wide angle projection lens with a short focal length. However, with this method, first of all, it is difficult to create a fine pattern, and it is also difficult to make the aperture of the projection lens wide. Therefore, the pattern is projected onto a distant subject with sufficient light intensity. The problem was that it was difficult to do.

In addition, with any of the methods mentioned above, it is difficult to project a pattern onto the subject surface with high resolution, and it is especially difficult to project a pattern with good optical performance over a wide angle of view while reducing the size of the projection lens. The problem was that it involved aberration correction, which was very difficult.

As a proposal to solve these problems, Japanese Patent Application Laid-Open No. 63-47710 proposes a system in which a plurality of illumination light sources are used to create the above-mentioned large pattern image. However, such a configuration 7+−Ll 'J /rSl
n+ 1111, 8 H-t' M +In science Mτ
HA PE4 Wl 1-Jh ihu hm I don't know.

In addition, there is a light projection system for automatic focus detection that projects a pattern over a wide area on a subject, such as Japanese Patent Laid-Open No. 62-247312, although the purpose is different.

According to the publication, the projection lens is composed of a plurality of lens parts whose optical axes are shifted, so that a pattern can be projected well on both a long-distance subject and a short-distance subject.
The pattern is effectively projected over a wide range of areas on the subject to enable focus detection.

The present invention appropriately arranges each element of the light projection system that has a certain pattern, projects the pattern on a wide range of subjects with good imaging performance, and in particular, performs distance measurement at multiple points on the subject with high accuracy. The purpose of the present invention is to provide a light projection system for automatic focus detection that can perform automatic focus detection.

(Means for Solving the Problems) The light projection system for automatic focus detection of the present invention allows the light projection means to repeatedly illuminate a predetermined pattern illuminated by the illumination system.
AEshi E1. ilk'II? 't*7! II-A)6,
Fn+Jr4q+, tkp< In a light projection system for automatic focus detection that detects the focus of a photographing system by receiving a turn image with a light receiving system, the light projection means are arranged so that their optical axes are located on the same plane. It has n lens parts (n is an integer of 2 or more) having substantially equal refractive power, the refractive power of the lens parts is φp, the distance between the vertices of the n lens parts is d, and the light emitting means is When the focal length is f, the air-equivalent optical path length from the pattern to the light source of the illumination system is δ, and the length of the light source of the illumination system in the plane containing the optical axes of the n lens sections is S, then 0. .36< φ, xnxd...la)
φ, xd< S/(f+δ) ・・・・・・(b)
It is characterized by satisfying the following conditions.

(Embodiment) FIG. 1 is a schematic view of a main part of an embodiment in which the present invention is applied to a part of an imaging system, and FIG. 2(A) is a perspective view of the light projection system of FIG. 1. FIG. 1 shows a case where the light projecting system according to the present invention is applied to a photographing system having a passive type automatic focus detection device of a so-called phase difference detection type.

In the figure, reference numeral 101 denotes a light projection system, which has a configuration as described later and projects a pattern onto the subject when the subject is dark or when the contrast is low and focus detection cannot be performed using a passive method. 21 is a photographing lens (objective lens). The photographing lens 21 forms an image of the subject on a photosensitive surface 30, and the subject is illuminated with natural light such as sunlight on a focus detection unit 102 having a configuration as described later through the semi-transparent surface of the quick return mirror 22 and the sub-mirror 23. An image (in the case of a passive method) and a pattern image projected onto the subject by the light projection system 101 (in the case of an active method) are guided.

As shown in FIG. 2(A), the light projection system 101 in this embodiment includes a pattern 2 having an IA pattern extending in the horizontal direction, and a light projection means (hereinafter also referred to as a "light projection lens") that projects the pattern 2 onto the subject side. ) 1, and an illumination system 3 having a light source such as an LED having a relatively large light emitting part for illuminating the pattern 2.

FIG. 2(B) is a schematic diagram showing the aperture state of the light projecting lens l when viewed from the front. The projection lens 1 is shown in Fig. 2 (A).
, As shown in (B), the lens section 1 has an optical axis 15 that forms a pattern image in the same direction as the optical axis of the photographing lens 21.
1, a lens section 12, a lens section 13 having an optical axis 16 that forms a pattern image in a direction different from the optical axis of the photographic lens 21, and a pattern image formed in a direction different from the optical axis of the photographic lens 21. A lens portion 1 having an optical axis 17 that
It has four lens parts having substantially equal refractive powers. Among these, the lens portions 11 and 12 have the same optical axis 15 and have the same optical function. In addition, the optical axes 15 and 16 of each lens part
．． 17 exists in a plane parallel to the direction in which the pattern 2 is assembled.

and these four lens parts of the projection lens 1, 11.1
2.13.14, the pattern 2 is changed to, for example, the fourth pattern. As shown in FIG. 5, pattern images 31, 32, and 33 are projected onto three different areas on the subject, with some parts overlapping each other. Note that the pattern image 31 is an image formed by the lens portions 11.12.

Next, a focus detection method using the focus detection unit 102 shown in FIG. 1 will be explained using FIG. 3. Figure 3 is the first
FIG. 2 is an exploded perspective view of the optical system of the focus detection unit 102 shown in the figure. In FIG. 3, the mirror 26 shown in FIG. 1 is omitted.

This embodiment shows a focus detection device for multiple distance measurement, which is capable of measuring distances in multiple (three locations in the figure) areas of the subject image formed by the objective lens 21.

In the figure, reference numeral 24 denotes a field mask, which has openings 24a to 24c corresponding to a plurality of distance measurement areas, and is disposed near the intended imaging plane of the objective lens 21. A field lens 25 is arranged near the intended image plane.

28 is a secondary optical system, and two lenses 28a are arranged symmetrically with respect to the optical axis of the objective lens 21.

28b. Reference numeral 29 denotes a light receiving means, and a plurality of pairs of light receiving element arrays (line sensors) 29al and 29a2, 29b1 and 29b2 corresponding to multiple distance measurements are arranged behind the two lenses 28a and 28b.
．． It has 29c1 and 29c2.

27 is an aperture and the two lenses 28a.

28b and two inlet portions 2 arranged in front thereof.
7a and 27b.

Note that the field lens 25 has an aperture 27a of the collimator 27.
, 27b on each region of the exit pupil of the objective lens, and the pre-tinted light transmitted through each region forms a light quantity distribution on the light receiving element array.

In the focus detection device shown in this embodiment, when the imaging point of the objective lens 21 is on the front side of the f constant imaging plane, for example, the object image or pattern formed on the two light receiving element rows 29bl and 29b2, respectively. When the light intensity distributions of the two images become close to each other and the image forming point of the objective lens 21 is behind the intended image forming plane, the two light receiving element arrays 29bl
.

The light quantity distributions formed on the respective portions 29b2 are separated from each other. Moreover, two light receiving element rows 29bl, 29b
The amount of deviation in the light intensity distribution formed on each of the objective lenses 2 and 2 is
Since there is a certain functional relationship with the amount of defocus of the objective lens 21, the amount of defocus is calculated by an appropriate calculation means, and the direction and amount of defocus of the objective lens 21 are detected.

FIGS. 4 and 5 show pattern images 31 and 3 when pattern 2 is projected onto a subject by the light projection system 101 according to the present invention.
2.33 and the distance measurement field of view 34°35.36. FIG. FIG. 4 corresponds to the case on the wide-angle side when the IUe lens is a wide-angle lens or a zoom lens, and FIG. 5 corresponds to the case on the telephoto side when the photographing lens is a telephoto lens or a zoom lens.

In FIGS. 4 and 5, pattern images 31°, 32.33 are lens portions 11° (12) and 13.1 of the projection lens 1, respectively.
4 represents the image of pattern 2. Ranging field of view 34
, 35 and 36 are the openings 24a of the field mask 24 in FIG.
~24c.

Typically, a -eye reflex camera is equipped with photographic lenses of various focal lengths. For this reason, a focus detection device that detects focus from multiple points within the photographic screen using the light rays that have passed through the photographic lens has a rangefinding field of view or is fixed relative to the photographic screen; Changes depending on focal length.

On the other hand, in a light projection system that projects a pattern onto a subject without passing through the photographic lens as in this embodiment, the projection range of the pattern remains unchanged with respect to the focal length of the photographic lens. Therefore, the position of the distance measuring field with respect to the projected pattern image changes as shown in FIGS. 4 and 5 depending on the focal length of the photographing lens.

As shown in FIGS. 4 and 5, in this embodiment, a plurality of lens units 11, 11, 12, 12, 12, 12, 12, 12, 12, 11, 12, 11, 12, 12, 11, 11, 10, 11, 10, 11, 11, 11, 22, 22, 22, 22, 32, 32, 22, 22 have been explained,,,,,which projecting lenses are used to project a pattern onto a wide area,on a subject corresponding to a plurality of distance measuring points. (
12), 13.14 to form a plurality of pattern images 31°32.33 on the subject, so that no matter what focal length the photographic lens has, it can be This allows for excellent focus detection.

In particular, in this embodiment, the pattern 2 is a striped pattern made up of lines of different widths, and the light receiving means 29 is constituted by a one-dimensional light receiving element array (line sensor) such as a CCD. The striped direction of the pattern and the arrangement direction of the light-receiving element rows are made perpendicular, thereby improving the accuracy of detecting the contrast of the object in the direction in which the light-receiving element rows are arranged.

In this embodiment, the three pattern images 31, 32 and 33 are arranged so that they partially overlap each other on the subject, so that the distance measuring field of view 35 is
and 36 overlap with pattern images 31 and 32, respectively,
Also, even when the pattern images 31 and 33 are placed in a portion overlapping each other, the focus detection accuracy is prevented from decreasing.

Then, two or more (in this example, two) pattern images are projected in substantially the same direction as the optical axis of the imaging system and on both sides thereof, so that the pattern images are projected near the center of the imaging screen where the main subject is likely to be located. Try not to overlap each other.

In order to enable highly accurate focus detection even if the distance measurement field of view is located in the area where the pattern images 31, 32, 33 overlap with each other, it is necessary to improve the imaging performance of the area where the pattern images 31, 32, 33 overlap with each other. As described above, the optical axes of the lens sections 11, 12, 13, and 14 constituting the projection lens 1 are arranged in a plane parallel to the direction of pattern formation, and the refractive power of each lens section is approximately equal. I have to.

This prevents positional deviation of the pattern image and deviation of the imaging magnification, making it possible to perform highly accurate focus detection.

In addition, in this embodiment, each lens portion 11.12 of the light projecting lens 1
．． 13. The aperture area of 14 is appropriately set, and the light intensity ratio of the pattern image formed at the center and the periphery of the photographic screen is controlled so that the ratio of the reach distance of the pattern image becomes a desired value. .

Next, the structural features of each element of the light projection system in this embodiment will be explained.

As shown in FIGS. 4 and 5, the distance between the three distance measurement fields 34, 35, and 36 on the subject increases as the focal length of the photographic lens becomes shorter. The present invention is a photographic lens with a standard focal length commonly used in single-lens reflex cameras (
Hereinafter referred to as the "standard lens". ), the purpose of this is to enable a pattern image to be projected over almost the entire area of the main part of the photographic screen when the lens is attached, thereby improving focus detection accuracy. To achieve this, a commonly used photographic lens with a short focal length (hereinafter referred to as a "wide-angle lens") is required to have a configuration that can project a pattern image onto substantially the entire area of the main part of the photographic screen.

In this embodiment, in order to satisfy such conditions, the above-mentioned two conditional expressions (a) and (b) are satisfied in the configuration shown in FIG. 2.

In the embodiment shown in FIG. 2, the above-mentioned conditional expression (a>) is used.

(b) shows the case when n=3. Lens part 1
1.12 is counted as one because it shows the same optical effect.

Conditional expression (a) is for appropriately specifying the arrangement of the center position of the pattern image on the subject, and conditional expression (b)
is for continuously casting a plurality of pattern images on the subject.

Next, the technical contents of conditional expression (a) and conditional expression (b) will be explained using FIG. 6, FIG. 7, FIG. 8, and FIG. 9.

In FIG. 6, σ) 31 to 33 represent the pattern images shown in FIGS. 4 and 5, and 15a.

16a and 17a are lens portions-11 (12) in FIG. 2, respectively.
, 13 and 14 indicate the center positions of the pattern images 31 to 33 corresponding to the optical axes, and 40 indicates the range of the photographic screen corresponding to when a wide-angle lens is used.

FIG. 7 is an explanatory diagram for explaining the arrangement of the optical axis of the pot lens portion of the light projection system. In the same figure, 15a to 17a are the center position of the pattern image 31°32.33 in FIG.
0 indicates the range of the photographing screen, 41 indicates the lens sections 11 and 12, 42 indicates the lens section 13, and 43 indicates a thin lens corresponding to the lens section 14 in FIG. Reference numerals 44 and 45 represent virtual images created by optical members existing after the thin lenses 41 to 43, which are the virtual image of pattern 2 in FIG. 1 and the virtual image of the light emitting part 3 of the illumination light source, respectively. Virtual images 44 and 45 are formed by transmitting the pattern 2 and the light emitting part 3 of the illumination light source from the lens parts 11 to 14, respectively, when the projection system is composed of only the lens parts 11 to 14 and an optical member without refractive power. They will be placed at positions separated by the air-equivalent optical path length.

In FIG. 7, the distance between the thin lens 41 and the thin lens 42, and the distance between the thin lens 41 and the thin lens 43 (vertex distance) is d,
Assuming that the refractive power of the thin lenses 41 to 43 is φ2, the distance between the thin lenses 41 to 43 and the virtual image 44 of the pattern is It can be approximately expressed as 1/φ2. Also, optical axes 15 and 16 and optical axes 15 and 17 of the lens part
If the angle formed between them is 02, the following relationship holds between d and φ2°θ2.

tan θ, = φ, If the angle formed by the optical axis is 08, then the angle is θ. The following relationship holds between and focal length 1 m p w.

tanθ, = 1 s/Fw ”-”
``■Now, when a pattern image is continuously projected onto a subject using a projection lens composed of lens parts having n optical axes spaced apart by an interval d on the same plane, the projection range of the entire pattern image is Assuming that the overlap of the pattern images is sufficiently small regarding the angle θ8 formed between the boundary of holds true.

tan θ8 = φ, xnxd/2 -■ Therefore, in the horizontal direction of the photographic screen, if the proportion of the main part is X% of the entire screen, when a wide-angle lens is used as the HIL shadow lens, almost the entire main part of the photographic screen is In order to project a pattern image onto a region, it is necessary to configure the light projection system so as to satisfy the following relationship based on equations (1) and (2).

0, 36 X −<φ, xnxd ・・・・・・
■w The above conditional expression (a) is I! in the 0 expression. The focal length of the shadow lens is F, = 50 mm, and the proportion of the main part of the shooting screen is x
=50%.

The focal length of 711,150 mm is the focal length that is generally considered a standard lens for 35 mm eye reflex cameras, and focal lengths on the telephoto side are considered to be telephoto lenses, and are the focal point of commonly used photographic lenses. In the distance range, it is impossible to achieve a light projection system that projects a pattern image onto substantially the entire area of the main part of the photographic screen. In addition, it is sufficient to set the proportion of the main part of the photographing screen to include a plurality of distance measuring fields arranged within the photographing screen, but in order to clearly distinguish from the situation where the pattern image is projected only in the central part, this In the example, the value of the aforementioned X was set to 50%. In a range narrower than this, the effectiveness of the distance measuring device that measures multiple points within the wL shadow-white screen becomes weak.

FIG. 8 is an explanatory diagram for explaining conditional expression (b) for continuously projecting pattern images onto a subject. In the figure, numerals 15 to 17, 15a to 17a, and 40 to 45 are the same as in FIG. 7. Further, 31 to 33 correspond to the projection range of the pattern image shown in FIG.

In FIG. 8, the distance between the virtual image 44 of the pattern and the virtual image 45 of the light emitting part of the illumination light source is δ. For binding, the size of the virtual image of the light emitting part in the horizontal direction (the silk direction of the virtual image of the pattern) is set to 50.

The projection range of the pattern image by the thin lens 41 that projects the pattern image near the optical axis of the photographic lens is considered only by the light ray passing through the center of the thin lens 41, and the angle between the horizontal boundary line of the pattern and the optical axis is θ. . Now, the refractive power of the plurality of lens parts constituting the projection lens, that is, the refractive power of the thin lenses 41 to 43 in FIG. Therefore, if the distance δO between the virtual image 44 of the pattern and the virtual image 45 of the illumination light source is sufficiently smaller than the distance 1/φP between the virtual image 44 of the pattern and the thin lenses S11 to 43, the thin lenses 41 to 43 The pattern images 44 according to
It is projected onto ranges 31 to 33 having the size of a road or the like around 7a. Here, the distance δ between the virtual image 44 of the pattern and the virtual image 45 of the light emitting part of the illumination light source is δ. is assumed to be sufficiently small, but this interval δ. If δ is set to a large value, it becomes necessary to increase the size of the light emitting section 3 of the illumination light source in order to project a bright pattern image onto a wide range of subjects, leading to an increase in cost. is generally set small as mentioned above.

Since the pattern images 31 to 33 are projected around the center positions 15a to 17a of the pattern images as shown in FIG.
In order to continuously project these three pattern images 31 to 33 onto the subject, the angles θP and θC described above may be set so as to satisfy the following relational expression.

tanθp<2tanθ.・・・・・・Substituting the 0 expression and the ■ expression into the 00 expression results in the following.

φ, xd<S, /(1/φP◆60)・・・・・・00
By configuring a light projection system that satisfies the conditions of the equation, it becomes possible to continuously project the pattern images 31 to 33 onto the subject.

The light projecting means for achieving the object of the present invention may consist of only a light projecting lens having an aperture divided into a plurality of lens sections having refractive power such as time, or may include a light projecting lens and other positive or It is also possible to use a combination of lenses with negative refractive power to shorten the focal length of the entire light projecting means and further increase the projection magnification of the pattern. The above-mentioned conditional expression (b) was derived by modifying the equation (2) assuming such a light projecting means.

FIG. 9 shows an embodiment in which the light projection means according to the present invention is constructed by combining a light projection lens having a plurality of lens parts having refractive power such as time and one lens having positive refractive power. It is a schematic diagram. The figure shows the projection range of pattern 2 projected from one lens section 41. In the same figure, 41
．． 44 and 45 correspond to each element in FIG. 8, respectively. In FIG. 9, only the thin lens 41 is shown as a representative of the thin lenses 41 to 43 corresponding to the plurality of lens parts of the projection lens shown in FIG. 8 for simplicity. In Figure 9, 4
Reference numeral 6 denotes a lens with positive refractive power, which is shown as a thin lens that constitutes a light projecting means in combination with a thin lens 41. 2 and 3 are a pattern and a light emitting part of an illumination light source corresponding to FIG. 1, respectively. 44.45 are each thin lenses 4
6 is a virtual image of the pattern 2 and the light emitting part 3 of the illumination light source. The above equation (2) is the angle θ between the horizontal boundary line of the pattern and the optical axis when considering only the light ray passing through the center of the thin lens 41. The relational expression regarding the above is expressed using the position of the virtual image 44 of pattern 2 in FIG. 9 and the position and size of the virtual image 45 of the light emitting part 3 of the illumination light source.

Here, a similar relational expression will be expressed using the position of pattern 2 in FIG. 9, and the position and size of light emitting section 3 of the illumination light source.

In FIG. 9, 47 indicates a thin lens 41 and a thin lens 4.
6 represents the image-side principal point position of the entire light projecting means. Since the light projecting means is generally configured to project a pattern image onto a sufficiently distant subject, the rear principal point position 47
The distance from to pattern 2 is the focal length 11 of the entire light projecting means.
It is set approximately equal to 1f. Therefore, as shown in FIG. 9, when the air equivalent optical path length of the pattern 2 and the light emitting part 3 of the illumination light source is δ, and the horizontal size of the light emitting part 3 of the illumination light source is S, the light of the photographing lens is The projection range of the pattern image by the thin lens 41 that projects the pattern image near the axis is the angle θ between the horizontal boundary line of the pattern and the optical axis when considering only the light ray passing through the center of the thin lens 41. The equation (1) can be transformed and expressed as follows.

janθC= (S/2)/(f+δ)---
Substituting the 0 expression and the ■ expression into the 00 expression results in the following.

φ, Xd<S/(f+δ)...■ In other words, the above-mentioned conditional expression (b) is obtained.

If formula (2), that is, conditional formula (b) according to the present invention is not satisfied, an area where no pattern image is projected will occur between the plurality of pattern images projected onto the subject, and the photographic lens attached to the photographic lens will be Depending on the focal length, if the distance measurement field of view is placed in such an area, focus detection accuracy will decrease.

FIG. 10 is an explanatory diagram showing a specific configuration of the embodiment shown in FIG. 9. In the figure, 2 is a pattern, 3 is a light source of the illumination system, and 41 and 46 are lenses each having a positive refractive power corresponding to the thin lens shown in FIG. Reference numeral 49 denotes a transparent resin in which a light emitting part 3 of a light source for illumination is sealed.

The embodiment shown in FIG. 10 has the advantage that it is easy to shorten the focal length of the entire light projection system and expand the pattern projection range.

As explained above, the present invention has a light projecting means having a plurality of optical axes in the same plane, a plurality of lens parts having refractive power such as time, and a predetermined position at the rear of the light projecting means. Along with arranging the pattern and the light source for lighting,
By setting each element so as to satisfy the conditional expressions (a) and (b), for example, when a photographing lens is attached to an eye reflex camera, a pattern can be created in almost the entire area of the main part of the photographic screen. We have achieved a light projection system that makes it possible to project images.

(Effects of the Invention) According to the present invention, by setting the configuration of the pattern, the illumination system, and the light projecting means as described above, it is possible to achieve almost the entire main area of the photographic screen while maintaining good optical performance. It is possible to achieve a light projection system for automatic focus detection that can project a pattern and perform highly accurate focus detection at multiple points on the photographic screen.

[Brief explanation of drawings]

FIG. 1 is a schematic view of the main parts of the first embodiment when the present invention is applied to a part of the imaging system, FIG. 2 (A) is a perspective view of the light projection system in FIG. ) is a front view of the light projecting means in FIG. 2(A), FIG. 3 is a schematic diagram of the focus detection unit in FIG. 1, and FIG.
Fig. 5 is an explanatory diagram of a pattern image projected onto the subject side by the light projection system of the present invention, Fig. 6 is an explanatory diagram showing the range of the photographing screen and the projection range of the pattern in the present invention, and Figs. 7 to 9 FIG. 1 is an explanatory diagram of the optical system of the light projecting means showing the features of the present invention.
FIG. 0 is an explanatory diagram of a specific optical system in FIG. 9. In the figure, 101 is a light projection system, 102 is a focus detection unit, 1
1 is a light projecting means, 2 is a pattern, 3 is an illumination system, 11 to 14 are lens sections, 15 to 17 are optical axes, 21 is a photographing lens, 22
is a quick return mirror, 31 to 33 are pattern images,
34 to 36 are distance measuring fields, and 30 is a photosensitive surface. Figure 1 b Figure (A) Figure (B) Figure 5 Figure 0 0 Figure 8 Figure 0 Dormitory Figure 7

Claims (1)

[Claims] (1) Automatic focusing that detects the focus of the photographing system by projecting a predetermined pattern illuminated by the illumination system onto the subject using a light projecting means, and receiving the pattern image reflected from the subject by the light receiving system. In the light projection system for detection, the light projection means has n lens portions (n is an integer of 2 or more) having substantially equal refractive powers and arranged so that their optical axes are located on the same plane. , the refractive power of the lens portion is φ_p, the apex interval of the n lens portions is d, the focal length of the light projecting means is f,
When the air-equivalent optical path length from the pattern to the light source of the illumination system is δ, and the length of the light source of the illumination system in the plane containing the optical axes of the n lens parts is S, 0.36<φ_p× A light projection system for automatic focus detection, characterized in that it satisfies the following condition: n×d φ_p×d<S/(f+δ).