JPH03179409A - Projection system for automatic focus detection - Google Patents

Abstract

PURPOSE:To project illumination light on the entire area of the principal part of a photographic picture plane and to enable highly accurate focus detection at many points on the photographic picture plane by specifying the constitution of each lens part of a projection means. CONSTITUTION:The illumination light from a light source 200 is projected on a subject side by the projection means 1 and the reflected illumination light is photodetected by a photodetection system to detect the focus of a photography system. The projection means have (n) lens parts 11 - 14 which are arranged having their optical axes on the same plane and are nearly equal in refracting power and 0.36<phipXnXd and phipXd<S/f 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 projection means, and S the length of the light emission part of the light source in the plane containing the optical axes of the lens parts. Namely, the respective elements of the projection system which projects the illumination light from the light source having a light emission surface of specific size on the subject side are arranged properly. Consequently, the illumination light is projected on the wide-range subject in an excellent state and distance measurement is performed at, specially, plural points on the subject with high accuracy.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a light projection system for automatic focus detection suitable for photographic cameras, cine cameras, video cameras, etc. In passive and active automatic focus detection, which are suitable for detecting the focus of a photographic system by emitting illumination light and receiving the illumination light reflected from the subject side, focus detection is performed while expanding the distance measurement range. The present invention relates to a light projection system for automatic focus detection with improved 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.
This is an active method proposed in Publication No. 7-154206 and the like.

Among these, the active method is a method that performs focus detection by emitting, for example, an infrared beam from the camera side to the subject side and receiving the reflected beam from the subject, even when the subject side is dark or the contrast of the subject is low. However, it has the advantage of being able to perform focus detection with high precision. However, when the subject is far away, the amount of reflected light flux decreases and the focus detection granularity decreases.

The passive method detects the focus by detecting the imaging state of the subject image by the imaging system using a detection means installed in a part of the camera, and allows relatively high-grained focus detection even when the subject is far away. There are some advantages to being able to do that. However, when it is dark on the subject side or the contrast of the subject is low, the focus detection granularity decreases.

One way to overcome this shortcoming is, for example, in the
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.

Among recent automatic focus detection devices, various so-called multi-point distance measurement type focus detection devices have been proposed, which perform distance measurement by selecting any one point out of 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 uniform illumination, 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.

In addition, I! which uses a fine pattern and has a short focal length and wide angle of view. There is a method of projecting images using an optical lens. 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, with such a configuration, the above-mentioned problem of correcting aberrations of the light projecting lens cannot be solved.

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.

In the present invention, each element of a light projection system that projects illumination light from a light source having a light emitting surface of a predetermined size toward the subject is appropriately arranged. emits light,
In particular, an object of the present invention is to provide a light projection system for automatic focus detection that can perform distance measurement at multiple points on a subject with high precision.

(Means for Solving the Problems) The light projection system for automatic focus detection of the present invention projects illumination light from a light source onto the subject side using a light projection means, and receives the illumination light reflected from the subject side. In a light projection system for automatic focus detection, which detects the focus of the photographing system by receiving light from the system,
The light projecting means has n lens parts (n is an integer of 2 or more) having substantially equal refractive powers arranged so that the optical axes are located on the same plane, and the refractive power of the lens parts is is φ2, the distance between the vertices of the n lens parts is d, and the focal length of the light projecting means is f.
, where S is the length of the light emitting part of the light source in the plane containing the optical axes of the n lens parts, 0.36<φ, x
n x d...” ” (a) φ, Xd<
It is characterized by satisfying the condition S/f...(b).

(Embodiment) Fig. 1 is a schematic diagram of the main parts of an embodiment when the present invention is applied to a part of the Wi shadow system, and Fig. 2 (A) is a perspective view of the 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 same figure, reference numeral 101 is a light projection system, which has the configuration described later when the subject is dark and focus detection cannot be performed using the passive method. When the contrast is low, a predetermined pattern is projected onto the subject side. 21 is a photographing lens (objective lens).The photographing lens 21 forms a subject image on the photosensitive surface 3o, and the quick return mirror
A subject image illuminated with natural light such as sunlight (in the case of a passive method) and a light projection system 101 are transmitted to a focus detection unit 102 configured as described later through a semi-transparent surface of No. 2 and a sub-mirror 23.
The image illuminated by the illumination light projected onto the object by the projection system 101 or the image of the pattern 2 formed on the light emitting surface 200 of the light source projected onto the object surface by the projection system 101 (in the case of the active method) is guided respectively. It's shining.

FIG. 2(A) shows a case where a predetermined pattern 2 is formed on the light emitting surface 200 of the light source and the pattern 2 is projected toward the subject.

In this embodiment, when simply projecting illumination light to the subject side, the light emitting surface 200 on which no pattern is provided is used as a light source, and when a pattern is projected onto the subject side, the light emitting surface 200 is used as a light source on that surface. Light emitting surface 20 provided with pattern 2
0 is used.

The method of projecting illumination light with a predetermined angle of view onto the subject during focus detection and using the subject image within the range illuminated by the illumination light is the same as when a pattern is projected onto the subject. can be handled.

Therefore, in the following embodiment, a pattern 2 is formed on the light emitting surface 200 as shown in FIG.
A case will be described in which the pattern 2 is projected onto the subject side and the image of pattern 2 is used.

As shown in FIG. 2(A), the light projection system 101 in this embodiment includes a light emitting surface 200 constituting a light source on which a pattern 2 having a striped pattern extending in the horizontal direction is formed.
It has a light projecting means (hereinafter also referred to as a "light projecting lens") 1 that projects a pattern 2 formed on the surface 0 onto the subject side.

FIG. 2(B) is a schematic diagram showing the aperture state of the projection lens 1 when viewed from the front. The projection lens l is shown in Figure 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, and a lens section 1 having an optical axis 16 that forms a pattern image in a direction different from the optical axis of the photographing lens 21;
3, and a lens section 14 that also has an optical axis 17 that forms a pattern image in a direction different from the optical axis of the photographic lens 21.
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. Furthermore, the optical axes 15, 16 .
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 and 14, the pattern 2 is changed to, for example, the fourth pattern. As shown in FIG. 5E, 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.

In this embodiment, a focus detection device for multiple distance measurement is shown, which is capable of measuring distances in a plurality of areas (three areas in the figure) of the object 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 2902.

27 is an aperture and the two lenses 28a.

Two openings 2 corresponding to and arranged in front of 28b
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 light beams transmitted through each region form 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 located in front of the intended imaging plane, for example, the object image formed on the two light-receiving element rows 29bl and 29b2, or the pattern 2 When the light intensity distributions for the images of are close to each other and the image forming point of the objective lens 21 is on the rear side of the intended image forming surface, the two light receiving element rows 29bl
.

The light amount 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 photographic lens is a wide-angle lens or a zoom lens, and FIG. 5 corresponds to the case on the telephoto side when the photographic 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. Therefore, with a focus detection device that detects focus at multiple points within the photographic screen using the light rays that have passed through the photographic lens, the field of view for distance measurement 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, in order to project a pattern onto a wide range of areas on a subject corresponding to a plurality of distance measuring points, a projecting lens is used as a plurality of lens units 11. (
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 line 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 the 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 i-shadow system and on both sides thereof, so that the pattern image is projected near the center of the photographic screen where there is a high probability that the main subject is located. This prevents the images from overlapping each other.

In order to improve the imaging performance of the pattern images 31, 32, 33, the area where the pattern images 31, 32. As mentioned above, the optical axes of the lens parts 11, 12, 13, and 14 constituting the light projection lens 1 are arranged in a plane parallel to the line direction of the pattern, and the refractive powers of each lens part are approximately equal. I have to.

This prevents positional deviation of the pattern image and deviation of the imaging magnification, thereby enabling highly accurate focus detection.

In addition, in this embodiment, each lens portion 11.12 of the light projecting lens 1
, 13 and 14, and control the light intensity ratio of the pattern image formed at the center and the periphery of the photographic screen so that the ratio of the distance traveled by the pattern image becomes a desired value. There is.

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) appropriately defines the placement of the center position of the pattern image (in the case of illumination light, the illumination range) on the subject, and conditional expression (b) specifies the placement of the center position of the pattern image (in the case of illumination light) on the subject. When using illumination light, it is used to continuously project the illumination range).

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, 31 to 33 represent the pattern images shown in FIGS. 4 and 5, and 15a.

16a and 17a are the lens portions 11 (12) in FIG. 2, respectively;
13 and 14 indicate the center positions of pattern images 31 to 33 corresponding to the optical axis, 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 axes of each lens section 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. 44 is a thin lens 41~
It represents the virtual image created by the optical members existing after 43, and the light emitting part 2 of the illumination light source that formed the pattern 2 in FIG.
It is a virtual image of 00. The projection system of the virtual image 44 is the lens section 11~
14 and an optical member having no refractive power, the light emitting part 200 of the illumination light source forming the pattern 2 is arranged at a position separated from the lens parts 11 to 14 by the air-equivalent optical path length. It turns out.

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 (m point interval) is d,
Assuming that the refractive power of the thin lenses 41 to 43 is φ1, the projection system is usually configured so that the pattern is imaged on a sufficiently distant subject, so the thin lenses 41 to 43 and the pattern 2 are
The distance between the virtual images 44 of the light emitting section 200 that have formed is approximately 1
/φ2. Also, the optical axis 15 of the lens part
and 16 and the optical axes 15 and 17 are 01, then d, φ2. The following relationship holds true between θ2.

tin θ2-φ, xd ・・・・・・■Also, in Fig. 6, if the focal length of the photographing lens is F, the size of the horizontal photographing screen is 36 mm, so the boundary line of the horizontal photographing screen and the photographing If the angle formed by the optical axis is Ow, then the angle is θ. The following relationship holds between and focal length FW.

janθW = 1 8/Fw ---...
- ■ Now, when projecting a pattern image continuously onto a subject using a projection lens consisting of a lens section that has zero optical axes spaced apart by a distance d on the same plane, the entire pattern image If it is assumed that the overlapping of pattern images is sufficiently small with respect to the angle θ6 between the boundary of the projection range and the photographing optical axis, then the projection range is tanθ.

is n of tanθ2 regarding the position of the center of the pattern in equation
/ Since it is doubled, the following relationship holds: tanθ^ = φ, In the case where 11 is used, in order to project a pattern image onto substantially the entire area of the main part of the shadow screen, it is necessary to configure the light projection system so as to satisfy the following relationship from equations (1) and (2).

0, 36 X −<φ, xnxd...
・・■F.

The above-mentioned conditional expression (a) is F, which is the focal length of the photographic lens in equation (2). =50mm and J! The ratio of the main part of the white screen is 0
It was calculated as 250%.

Focal length IIt50mm is the focal length that is generally considered a standard lens for 35mm eye reflex cameras, and focal lengths on the telephoto side are considered to be telephoto lenses, and are commonly used in many photographic lenses. In the focal length 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%. If the range is narrower than this, the effectiveness of the distance measuring device that measures multiple points within the photographic 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 size in the horizontal direction (stripe direction of the virtual image of the pattern) of the virtual image 4'4 of the light emitting unit 200 of the illumination light source provided with pattern 2 is S. shall be. 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. .

6j can be expressed by the following relational expression.
anθC= (S, /2) / (1/φP) ・
......■Currently, 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. ~
The light emitting section 200 in which the pattern image 2 according to 43 is formed
The virtual image 44 is projected onto the ranges 31 to 33 having the size of a path or the like around the center positions 15a to 17a.

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 above-mentioned angles θ and θ are adjusted. should be set so that it satisfies the following relational expression.

tan θ, <2 tan θ0... Substituting the 0 formula and the ■■ formula into the ■■ formula results in the following.

φ, xd<S. /(l/φP) ・・・・・・■■
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 include a light projecting lens that has an aperture divided into a plurality of lens sections having refractive power such as a light projecting lens, or a light projecting means that includes a light projecting lens and other lenses. Alternatively, it is also possible to further increase the projection magnification of the pattern by shortening the focal length of the entire light projecting means by combining lenses with negative refractive power. The above-mentioned conditional expression (b) was derived by modifying the equation (2) assuming such a light projecting means.

FIG. 9 shows an embodiment of the light projecting means according to the present invention in which a light projecting lens having a plurality of lens parts having refractive power such as a path and one lens having positive refractive power are combined. FIG. The figure shows the projection range of pattern 2 projected from one lens section 41. In the same figure, 41
．． 44 correspond to each element in FIG. 8, respectively. 9th
In the figure, the thin lenses 41 to 43 corresponding to the plurality of lens parts of the light projecting lens shown in FIG.
Only 1 is shown as a representative. In FIG. 9, reference numeral 46 denotes a lens with positive refractive power, which is shown as a thin lens that constitutes a light projecting means in combination with the thin lens 41. 20
0 is a light emitting part of an illumination light source provided with a pattern 2 corresponding to FIG.

44 are virtual images of the light emitting portions 200 of the illumination light sources provided with the pattern 2 formed by the thin lenses 46, respectively. 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 for the light emitting unit 200 provided with pattern 2 in FIG.
It is expressed using the position and size of the virtual image 44.

Here, a similar relational expression will be expressed using the position and size of the light emitting section 200 of the illumination light source provided with pattern 2 shown in FIG.

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 projection means is generally configured to project a pattern image onto a sufficiently distant subject, the distance from the rear principal point position 47 to the light emitting section 200 provided with pattern 2 is equal to the focal length f of the entire light projection means. is set almost equal to. Therefore, as shown in FIG. 9, when the horizontal size of the light emitting part 200 of the illumination light source provided with pattern 2 is S, 11
The projection range of the pattern image by the thin lens 41 that projects the pattern image near the optical axis of the M2 lens is the angle θ0 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.

tanθc = (S/2)/f,,,,
,・Substituting the 0 expression and the ■■ expression into the ■■ expression results in the following.

φP xd<S/f...
...■ That is, the above-mentioned conditional expression (b) is obtained.

If Equation 0, that is, conditional expression (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 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, 200 is a light emitting part of a light source provided with pattern 2, and 41 and 46 are lenses each having a positive refractive power corresponding to the thin lens in FIG. 9. 49 is a transparent resin in which a light emitting part 200 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 (the illumination range in the case of illumination light).

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 a path, and the light projecting means. A light source having a light emitting surface of a predetermined size or a pattern with a predetermined pattern and a light source for illumination are arranged at the rear, and the conditional expression (a
) and conditional expression (b), for example, when a photographic lens is attached to a -eye reflex camera, p<
A light projection system has been achieved that makes it possible to project H bright light or pattern images.

Incidentally, the light emitting part 2 of the illumination light source is provided with the pattern 2 of the present invention.
00 can be easily achieved by forming electrodes arranged on the surface of a light emitting element such as an LED into a predetermined pattern.

Above, we have explained the case where the light emitting part 200 of the illumination light source is provided with the predetermined pattern 2. This pattern is particularly useful when the present invention is used in combination with a passive focus detection device such as a single-lens reflex camera. It is valid. Furthermore, the present invention can be fully applied to the case where a light source having a light emitting surface without a pattern is used as described above.

(Effects of the Invention) According to the present invention, by setting each structure of the light emitting part pattern of the light source for illumination, the lens part of the light projecting means, etc. as described above, photographing can be performed while maintaining good optical performance. It is possible to achieve a light projection system for automatic focus detection that can project illumination light or a pattern onto substantially the entire area of the main part of the screen, and can 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, 200 is a light emitting surface, 11 to 1
4 is a lens section, 15 to 17 are optical axes, 21 is a photographic 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 2 Figure (A) Figure (B) Figure 0 7 Figure 17α Figure 1

Claims (2)

[Claims] (1) Light projection for automatic focus detection that detects the focus of the photographing system by projecting illumination light from a light source onto the subject side using a light projection means, and receiving the illumination light reflected from the subject side using a light receiving system. In the system, the light projecting means consists of n pieces (n
has lens parts (an integer greater than or equal to 2), the refractive power of the lens part is φ_p, the apex interval of the n lens parts is d,
When the focal length of the light projecting means is f and the length of the light emitting part of the light source in a plane including the optical axes of the n lens parts is S, 0.36<φ_p×n×d φ_p×d< A light projection system for automatic focus detection, characterized in that it satisfies the following condition: S/f. (2) The light projection system for automatic focus detection according to claim 1, wherein a predetermined pattern is formed on the light emitting part surface of the light source.