JPH02264212A - Automatic focus adjusting device - Google Patents

Abstract

PURPOSE:To improve defocusing due to a measurement path parallax deviation occurring to a short-distance subject by dividing a projection and a photodetection optical path and putting them in charge of an orientation. CONSTITUTION:Part of a visible light cut filter 61 arranged in front of projection and photodetection lenses 8 and 9 is made wedgelike to divide the optical path into two and one optical path crosses an optical axis of photography at a normal subject distance of 2 - 3m. The other optical path crosses the optical path of photography almost at a minimum distance within a photographable distance range of, e.g. 0.6m. Consequently, the defocusing due to the distance measurement parallax deviation at a short distance is improved and performance deterioration at other subject distances can be precluded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an automatic focusing device for a photographic lens, particularly an active distance measuring device, and relates to an optical system for distance measuring.

[Prior Art] Various systems have been known and proposed as automatic focusing devices for photographic lenses. For example, a method that performs focus detection based on the contrast information of the subject and information about the image shift of the subject is called a passive range finder. A system that performs focus detection by receiving a diffusely reflected signal and evaluating this signal is called an active distance measuring device.

The latter type of active rangefinder requires the projection of near-infrared light or ultrasonic waves, and is relatively disadvantageous from an energy standpoint. On the other hand, the former type of passive rangefinder lacks contrast, which is a weak point. It has positionality with respect to the subject.

By the way, a method that uses all or part of the photographic optical system when performing distance measurement is called a TTL method, while a method that has an optical system for focus adjustment separate from the photographic optical system is called external distance measurement. ing. In addition, external distance measurement has the advantage that a sufficient baseline length can be ensured compared to the TTL method, so that accurate distance measurement is possible. The present invention relates to an improvement of an automatic focus adjustment device using an active external distance measurement method according to these classification methods.

Next, the general configuration and operation of this active external ranging method will be explained.

FIG. 1 shows a so-called four-group zoom type photographic lens. In the figure, reference numeral 1 denotes a lens group for focus adjustment, and by changing its position in the optical axis direction, the focusing (object) distance changes. It should be noted that the further the lens group is moved toward the subject, the more it is possible to focus on a subject at a closer distance. Here, if the amount of movement a from the position of the lens group when in focus on an object at infinity (hereinafter referred to as the amount of front lens extension) is X, and the focusing distance of the subject is R, then 1/R and X are approximately proportional to each other. It is in. Therefore, due to this relationship, in order to focus on an object directly in front of the lens using the lens group, it is necessary to extend the front lens abnormally large, and the closest distance that can actually be photographed is approximately 1.2 m. things were common. Also, vignetting around the screen is also related to this setting of the closest distance. That is, the closest distance is determined within a range that does not cause vignetting around the effective screen over the entire zoomable focal length range.

Reference numeral 2 denotes a lens group for varying magnification, and the focal length changes by changing the position of this lens group in the optical axis direction. Reference numeral 3 denotes a lens group for correction, which works in conjunction with the variable magnification lens group during zooming in order to keep the focal plane constant even when variable magnification is performed. 4 is an aperture, and 5 is a lens group for image formation.

Further, 6 indicates a focal plane.

FIGS. 2 to 4 are diagrams showing the basic principles of the four-group zoom lens described above and the well-known automatic focusing system of the active external distance measuring system.

In Fig. 2, 8 is a light emitting element such as an IRED, 9 is a projection lens for projecting light onto the subject, 10 is a person who is the subject, and 11
is a light-receiving lens for forming an image of the diffusely reflected light of the projected light beam hitting the subject onto the light-receiving element 7; 7 is the light-receiving element; A;
It is divided into two areas (B) and can be diagnosed by extracting the amount of light received from each area. In the figure, since the reflected light from the object 1o is imaged at the center of the light receiving elements A and B, the outputs from both sensors A and B are approximately equal. That is, a spot is imaged at a position as shown in FIG. 3(a). Further, if the subject changes from this state to the position 10', the reflected light beam will move in the direction of area A, following the dashed-dotted line in FIG. That is, the fourth
As shown in figure (b), the relationship is A sensor output > B sensor output. Moreover, when the object is 10'', the relationship becomes reverse as shown in FIG. 3 (c), and the relationship becomes B sensor output>A sensor output.

From this, an automatic system that links the lens group 1 for focusing shown in Fig. 1 with the light receiving element position shown in Fig. 2, and correctly focuses on the subject when the outputs from both sensors A and 8 almost match. A focusing device is configured.

FIG. 4 shows an example of a signal processing circuit of this type of automatic focus adjustment device. In the figure, the light receiving elements 7A and 7B each have an amplifier circuit 12A.

12B1 Bypass filter (HPF) 13A, 13B for cutting DC components, detection circuit 14A, 14B
are connected, and the outputs of the detection circuits 14A and 14B are further connected to integration circuits 15A and 15B. The light emitting element 8 is driven by a drive circuit 22, and the drive circuit 22 receives a control pulse signal (
(not shown), the light emitting element 8 emits pulsed light.

The pulsed reflected light from the object received by the light receiving elements 7A and 7B is then transmitted to the amplifier circuits 12A and 1, respectively.
After the signal is amplified to a predetermined level by bypass filters 13A and 13B, the DC component is removed by bypass filters 13A and 13B, and synchronously detected by detection circuits 14A and 14B. Each synchronously detected signal is integrated and smoothed by integrating circuits 15A and 15B, and a sum and a difference are calculated by an adder 16 and a subtracter 1f. These values are manually input to the comparator 18 and compared with a predetermined level,
When the sum of the integral values reaches a predetermined value dA+6, it is determined that focusing, that is, distance measurement operation is possible, and the absolute value of the difference between the integral values is compared with a predetermined level to determine whether or not focus is achieved. , and whether it is the front pin or the rear pin is detected from the polarity of the difference signal. This detection result is manually inputted to the micro bomber 19, and according to the result, the drive circuit 20 that drives the motor 21 that drives the lens is controlled, and the lens is moved to the in-focus position and stopped. has been done.

The above is a well-known method of automatic focus adjustment using an active external distance measurement method, but there are also other methods, such as using a position sensor that can determine the absolute position of the image instead of a two-area sensor, or using a sensor that is divided into multiple pixels. Using CCD line sensor,
A method may be considered in which the position of the front lens is made variable depending on the result of detecting the distance to the subject.

In addition to using a light-receiving element as an element interlocking with the front lens, there is a method of using a light-receiving lens or a transparent parallel plane plate disposed between the light-receiving lens and the light-receiving element.

FIG. 5 shows a photographic lens including the above-mentioned automatic focus adjustment device. In the figure, reference numeral 23 denotes a lens frame that holds a lens group for focus adjustment, and has a gear portion 24 integrally therein. 25 is a follower part that interlocks the lens frame of this lens group with a light-receiving element (not shown) in the lower part 36 or other elements as mentioned above;
Reference numeral 26 denotes a lens barrel serving as a base, and when the lens group lens frame 23 rotates, it is displaced in the optical axis direction by a helicoid screw provided between the lens barrel 26 and the lens barrel 26.

This performs focus adjustment. Reference numeral 27 denotes a zoom operation ring which rotates integrally with a cam ring (not shown) provided inside the lens barrel 26, thereby operating the lens group 2 for zooming and the lens group 3 for correction. A zooming operation is performed by moving while maintaining a predetermined relationship. 33 is a gear portion integrally provided at the rear of the zoom ring. 29 is the aperture drive meter 3
0 is a lens barrel for holding the relay lens 5. A zoom motor 31 rotates a zoom ring via a gear 32. A focusing motor 34 rotates the focusing ring 23 via a gear 35, thereby moving a group of lenses for focus adjustment in the optical axis direction. 8 is the above-mentioned light emitting element, 9 is the above-mentioned transparent lens, and 8.9 is configured in the block 36. Further, a light receiving lens and a light receiving element are also constructed within the block 36. 38 is a floodlight beam, 37
The photographing optical axis and the emitted light beam intersect at .

FIG. 6 shows a front view of FIG. 5 when viewed from the direction A.

Figure 7 shows the range of the shooting screen at the wide end (wide-angle end), each spot position shows the distance measurement position when the subject distance is 3 m and 1.2 m, and Figure 8 shows the range at the tele end (telephoto end). This is the case. The fact that 3 m is at the center of the screen and the distance measurement position does not change depending on the focal length indicates that the position 37 shown in FIG. 5 is 3 m.

Now, let Xw be the distance between the spot points at the 3m distance measurement position and the 1.2m distance measurement position within the screen.

XT, the focal length at the wide end is fw, and the focal length at the tele end is f, then X T / X w = f t /
There is a relationship f w. Therefore, 1.
The distance to the 2m distance measurement position is constant on the subject, and as shown in Figure 6, suppose that the projection lens optical axis is 50 mm from the photographing optical axis, and 37 shown in the figure is 3
m (3000mm), 30mm on the subject
1f! This means that

This phenomenon in which the distance measurement position deviates from the center of the screen due to the subject distance is called distance measurement parallax shift.

Several methods have been proposed to remove such ranging parallax. An example is shown in FIG. Luns group 1
is focused on the subject 49 at the position 44 shown in the figure, and at this time the light emitting point of the light emitting element 8 is at 45 and the environment of the light receiving elements in the two areas is linked so that it is at 48. When the subject moves to a distant position 50 from this state, the image forming position on the light receiving element moves toward the photographic lens side (upper side in the figure), causing an imbalance in the difference between the A and B outputs.

As a result, it is detected that the object is Maebin, and the lens group 1 is retracted to focus on a more distant object.

Focus on subject 50 at position 43. At this time, as the light emitting point moves from 44 to 43, the light emitting point moves from 45 to 46, and the light receiving position moves from 48 to 47.

In this way, by simultaneously linking both the light emitting element and the light receiving element (or the light emitting lens and light receiving lens, etc. as mentioned above) with the lens group for focus adjustment, it is possible to eliminate distance measurement parallax deviation. Become.

[Problem that the invention seeks to solve]

However, in the case of the device shown in FIG.
Compared to the case where the projected light beam is fixed as shown in Fig. 6, 1. The interlocking mechanism becomes more complicated.

2. Distance measurement accuracy decreases when compared to a device with a fixed projected light beam.

In order to compensate for 3.2, it becomes necessary to improve the accuracy of parts and assembly, or to make the equipment more precise.

It had the following problems.

In order to compensate for the above drawbacks, a method has been proposed in which the projected light beam is made TTL and aligned with the I3 shadow optical axis. Power will decrease.

2. A half prism or the like is required to introduce light into the photographing optical path, which increases the cost.

3. Since half prisms and the like are provided, it becomes disadvantageous when downsizing the lens.

New problems such as these will arise.

On the other hand, there is a growing demand for recent photographic lenses to shorten the closest subject distance that can be photographed.

In the lens type shown in Fig. 1 mentioned above, vignetting of peripheral light occurs especially at wide angle. Structures that allow this are known. However, if the projected light beam remains fixed when such a lens is combined with the automatic focus adjustment device as described above, the distance measurement parallax deviation shown in FIG. 8 will become larger. For example, the closest distance that can be photographed is 0.6m.
In this case, the distance measurement position at the telephoto end will be completely outside the screen.

As mentioned above, in the case of active external distance measurement type automatic focus adjustment devices that fix the emitted light beam, measurement may vary depending on the focal length at the telephoto end, the shooting distance, and the positional relationship between the shooting optical axis and the light emitting lens. Distance parallax became a problem as the distance position sometimes moved off the screen.

In addition, improvements to this problem have been proposed in the past, but
It had several problems as mentioned above.

SUMMARY OF THE INVENTION An object of the present invention is to provide an active external distance measuring type automatic focus adjustment device that solves these problems.

According to the present invention, a light beam emitted from one light emitting element is divided into a plurality of light beams by a simple method as described below, thereby reducing the probability of occurrence of blur caused by distance measurement parallax deviation. It is something.

[Means and structure for solving the problem] A light emitting element placed outside the light beam passing through the photographic lens, a light emitting lens for projecting light from the light emitting element onto the subject, and a base line from the light emitting lens. It has a light-receiving lens arranged at a distance from the light-receiving lens, and a light-receiving element that receives the diffusely reflected light of the light beam imaged on the subject by the light-emitting lens by the light-receiving lens, and the output of the light-receiving element causes the light to be reflected from the photographing lens. In a device that performs focus adjustment, the light path projected onto the subject by the light emitting element and the projection lens is such that a light beam in an annular region excluding the projection optical axis is a light beam on the projection optical axis. The reason for this is that the light is divided and projected in different directions.

〔Example〕

Embodiments of the present invention will be described using FIGS. 10 to 25. First, referring to FIG. 10, the basic principle of the present invention will be explained. 61 is the above-mentioned projection/reception lens 8.9
This is an optical unit that has a light splitting effect and is composed of a parallel glass block part and a prism part that transmit the emitted light and the incident light. It also functions as a so-called visible cut filter, which transmits the near-infrared wavelength of light emitted by the light emitting element while cutting off light in the visible region. After passing through the projection lens 9, the light beam from the light emitting element 8 takes an optical path as shown in FIG. 14th
The figure shows a cross-sectional view of the light projection system and the optical path. Note that the direction of the upwardly refracted light ray, which is the direction in which the photographing lens is arranged, is determined by the refractive index of the prism material and the angle Q shown in FIG. Further, the ratio between the energy of the upward light ray and the energy of the light ray traveling linearly through the optical unit 6 is determined by baa.

Next, in FIG. 11, 51 is a photographing lens, the details of which are the same as in FIG. 5. 52 indicates a photographing optical axis. 1st
The light ray passing through the range indicated by a in FIG. On the other hand, the light ray that passes through the range indicated by b in Fig. 10 becomes the beam 55 shown in Fig. 11 and the subject pressure! ! 5
4, the image is focused on the upper side. Furthermore, when the beam 55 intersects the photographing optical axis at the subject distance 53, the beam 56 is focused downward.

12 and 13 show the imaging positions of the above-mentioned two projected light beams on the telephoto side within the screen. FIG. 12 shows the position of the projected spot image on the subject at 54 shown in FIG. 11, and this spot image 57 is the imaging position of the beam 56 in FIG. are shown respectively. Similarly, FIG. 13 shows the position of the projected spot image on the subject in FIG. 11, 53.
9 indicates the imaging position of the light ray 56 and 60 indicates the imaging position of the light ray 55, respectively.

These two emitted light beams are transmitted through the 15th light beam until they return onto the light receiving element.
The result will be as shown in the figure. In other words, the projected light beam that passed through the area shown in Figure 10 hits the subject and is diffusely reflected, and then from the opposite direction
When it passes through the prism part, it is refracted again and returns to the light receiving element 7 as shown in the figure, but the beam 63 that has passed through the part a goes straight without being refracted, so it does not return to the light receiving element 7. do not have. On the other hand, among the projected light beams that have passed through the range a in Figure 10, the beam light that has passed through part a and returned will form an image on the light-receiving element 7, but the light that has passed through part b is due to the prism effect. The light is refracted and follows the optical path 62, and exits above the sensor, which is the light receiving element 7.

Incidentally, as shown in FIG. 11, let us consider the state of image formation on the light receiving element 7 when both light rays projected with different directions strike the subject 54 or 53 at the same distance. Based on the light receiving element, the spot image 7o shown in FIG. The spot images 71 thus obtained will overlap at the same location.

Also, the light rays 62 and 63 shown in FIG. 15 are focused outside the sensor area at positions 72 and 73 shown in FIG. Therefore, although the total output obtained from the light receiving element is slightly reduced compared to the conventional one, the automatic focus detection function remains the same as the conventional one.

FIG. 17 shows a photographic screen when a persimmon fruit located at a distance of 0.6 m is photographed at the telephoto end, for example. In the conventional case where the light beam is not divided, the distance measurement position is 74, and if this position is the object plane 76 shown in Fig. 18, the persimmon fruit is not in focus and the distance measurement position is 76.
The camera focuses on the distance. 7 gives the most blur
This is a case where the object No. 6 is located at infinity, and since the lens group is at a position corresponding to the focusing position at infinity, the persimmon fruit that is intended to be focused is not focused at all.

FIG. 19 shows a screen according to the first embodiment of the invention shown in FIG. The projected light beam that has passed through part b, which is the prism part in FIG. 10, reaches position 77 and hits the persimmon fruit. 7
Position 4 corresponds to an infinite object. 74
77 if the reflected light does not return to the light receiving element at all.
Since distance measurement is performed only by reflected light from the light receiving element, an image of the spot 77 is formed on the light receiving element as a spot image 78 shown in FIG. 20(A). For this reason, in the conventional example shown in FIG. 17, the persimmon fruit could not be brought into focus, but in this embodiment, it is brought into focus correctly.

Also, if the spot 74 in Fig. 19 is unlucky to hit some object, the distance between the persimmon fruit and the object that the spot 74 hit will cause the spot to move away as shown in Fig. 20 (B) on the light-receiving element. Two images 79.80 are recognized. At this time, the focusing distance of the first lens group is determined by the first
It changes depending on the values of a:b shown in the figure and the respective distances and reflectances of the objects hit by spots 77 and 74, but
The in-focus distance is a certain distance between the distance of the persimmon fruit (0.6 m) and the distance to the object that is hit by the spot 74.
Even so, the situation is much more favorable than that of the conventional example. That is, FIG. 21 is a diagram for explaining the present invention in detail. It is assumed that the situation of the subject being photographed now is exactly the same as that shown in FIG. and upper spot 77
must be in contact with the persimmon fruit, which is the subject.

The horizontal axis represents the distance of the object hit by the lower spot 74. Further, the vertical axis indicates a focus position corresponding to the position where the first lens group actually stops. Since the subject to be focused on is a persimmon fruit, ideally it should be on the line 83. By the way, when there is no upper spot as in the conventional example shown in FIG. 17, the distance is naturally measured using only the lower spot, so a line 81 appears.

According to the configuration of the present invention, what used to be line 81 can be brought closer to line 83 by dividing the spot into two, such as the wavy line 82 shown in the diagonally shaded area in the figure. It is shown by the characteristics. here point 85
When the focusing distance is reached as indicated by , the persimmon fruit, which is the subject, will be slightly blurred, but this is an improvement compared to the conventional configuration of line 81. As mentioned above, the line approaches the ideal line for infinite objects.

As described above, the effect of the present invention is to improve the large distance measurement variation deviation that occurs in close-range objects by dividing the spot into two. On the other hand, 2
There is no deterioration in performance when shooting objects at normal photographing distances such as 3 m and 3 m.

FIG. 22 is an explanatory diagram of actually performing one closest shadow in a photographing lens embodying the present invention. The upward projecting light beam 88 intersects the photographing optical axis at a point 90 at a distance of 0.6 m. Further, the conventional light beam 87 intersects the photographing optical axis at a point 97 at a distance of 3.0 m. Note that the shaded range is the field angle range at the telephoto end of the photographic lens. The upward projected light beam will deviate to the upper side of the screen at a distance greater than the distance of the point 89.

In such a case, if we consider that there is a window frame shown at 93 at 3 m and we are photographing a distant landscape as shown in Figure 23, 92 is the viewfinder angle of view of an electronic viewfinder, etc., and 94 is the subject. It is a certain scenery. In reality, however, there is a window frame as shown in 93. Regardless of the probability of photographing under these conditions, in this case, the conventional projection light ray 87 is projected to an infinite distance, so the reflected light hits the light receiving element. Not going back at all.

Normally, when an output above a certain level cannot be obtained from the light-receiving element, the lens group for focus adjustment moves to the infinite focusing position (the most recessed position). In contrast, the projected light beam 88
When the light ray 87 hits the window frame, there is no output from the light ray 87, so the lens group for focus adjustment moves to a position that focuses on the distance of the window frame outside the screen (not the subject). As a result, the subject, a mountain in the distance, is out of focus.

A way to minimize this problem is to limit the range of distance that can be measured by the light ray 88 to, for example, the closest side of the point 89. For this purpose, it is necessary to make the power of the light beam 88 smaller than that of the light beam 87. For example, assume that the light ray 87 has a power P67 capable of measuring a distance of up to 10 m with respect to a subject with a reflectance of 20%. On the other hand, the power Pa8 of the light ray 88 is set to 1.0 for a subject with a reflectance of 20%. P67 is set so that distance measurement is possible until ON. From this, it can be seen that the power of the light beam 88 is only a few percent of the power of the light beam 87. As a result, although variations occur depending on the reflectance of the subject, the distant landscape that is the subject hardly ever becomes out of focus when photographing as shown in FIGS. 22 and 23. However, if the power is a few percent, line 82 will be at points 84 and 8 in Figure 21.
If it is 5, in addition to focusing on the persimmon fruit, the focus will be closer to line 81, which may make it difficult to obtain the effects of the present invention. From this, in reality, a practically optimal power distribution is selected in the range of several percent to several tens of percent.

As explained above, in an embodiment related to the present invention, in an automatic focus adjustment device using an active external distance measurement method, a part of the visible light cut filter placed in front of the light emitting/receiving lens is formed into a wedge shape. The optical path is divided into two, and one optical path is configured to intersect with the photographing optical axis at the same subject distance of <2 m, 3 m as in the conventional method, and
The other optical path is configured to intersect with the photographing optical axis near the closest distance within the photographable distance range, such as 0.6 m, and more preferably, the other optical path is configured to intersect with the photographing optical axis near the closest distance within the photographable distance range, such as 0.6 m, and more preferably, the power of the other optical path is By adopting a configuration in which the power is kept weak (several percent to several tens of percent), it is possible to significantly improve blur caused by distance measurement variation deviation at close distances, while at the same time degrading performance at other subject distances. An automatic focus adjustment device that prevents this as much as possible can be realized.

By the way, the longitudinal direction of the light-receiving element needs to cover the moving range of the light-receiving spot image, which moves according to the subject distance, but it is necessary to cover the moving range of the light-receiving spot over a wider subject range than before, from infinity to close distance. Then, it becomes necessary to make the light receiving element longer in the longitudinal direction.

However, if you try to make the sensor area wider by making the light-receiving element longer, the influence of external light other than the required infrared light cannot be ignored, and the S/N ratio of the light-receiving output decreases, making it difficult to maintain distance measurement accuracy. It becomes difficult.

Next, in consideration of this problem, an embodiment will be described in which distance measurement can be performed while using a light-receiving element of the same length as the conventional one, that is, without reducing the S/N ratio.

FIG. 24 is a perspective view of a distance measuring optical system according to the present invention, and FIGS. 25(A) and 25(B) respectively show a side cross section of a light receiving optical system as a light projecting optical system and its optical path diagram.

The optical system on the light emitting side has a predetermined inclination angle θ for the closest side distance, and has an annular region centered on the light emitting optical axis excluding the vicinity of this light emitting optical axis. The optical system has a similar inclination angle θ and a disk-like configuration that acts as a prism on the light receiving optical axis.

Now, considering the distance measurement accuracy of the active type, the projected light spot is normally projected and adjusted so that it will focus correctly at around 3m, but at a close distance of about 0.6m, it will be out of focus to some extent. , and a slightly expanded spot image is projected. Since this spread is approximately proportional to the diameter of the light emitting lens, it is possible to increase the diameter of the annular prism portion by sacrificing the diameter of the annular prism. The image becomes larger. Therefore, even if the spot is off the light-receiving element, the edge of the blurred image of the light-receiving spot will be in the sensor area, making it easier to start distance measurement.

By the way, it is most preferable to use an annular region with an outer circumference equal to the maximum effective diameter of the projection lens, but if the diameter of the projection lens is not strictly circular, it is necessary to match it to its minimum effective diameter. . Furthermore, since the optical unit 61 is a separate member from the projection lens, it is preferable to reduce the outer diameter of the prism portion to compensate for the error in optical axis alignment.

On the other hand, the prism portion of the light-receiving lens is preferably provided near the center of the light-receiving lens because the better the imaging performance, the higher the distance measurement accuracy. Note that the shape is not limited to a circle, and may be a polygon such as a rectangle. Alternatively, it may be annular with discontinuous prism regions.

Additionally, the prism part can be placed either on the subject side or on the light emitting/receiving lens side of the optical unit, but the optical unit may also serve as a visible light cut filter, in which case it is best to place it on the lens side for better appearance. It is desirable that the upper protrusion can be eliminated. At this time, it is reasonable to use an angle corresponding to the angle of view of the light emitting/receiving element as the draft angle during plastic molding.

As explained above, in the embodiment of the present invention, in an automatic focus adjustment device using an active external distance measurement method, a portion of the visible light cut filter placed in front of the light emitting/receiving lens is shaped into a wedge shape, thereby reducing the optical path. is divided into two, and one optical path is configured to intersect the photographing optical axis at the same subject distance of <2 m, 3 m as before, and the other optical path is configured to intersect with the photographing optical axis at the subject distance of <2 m, 3 m, etc. It should be configured so that it intersects with the photographing optical axis near a close distance, and more preferably, the other power should be weak (several percent to several tens of percent) compared to the power that passes through the optical path equivalent to the conventional one. As a result, it is possible to realize an automatic focus adjustment device that significantly improves blur caused by distance measurement parallax shift at close ranges and prevents deterioration of performance at other subject distances as much as possible.

[Effects of the Invention] As explained above, in an active external distance measuring type automatic focus adjustment device, by dividing the light emitting and receiving light paths and sharing the pointing directions, it is possible to This has made it possible to improve the out-of-focus problem caused by distance measurement parallax shift that occurred in the past.

[Brief explanation of drawings]

Figure 1 is an optical layout diagram of the most common four-group zoom lens. Figure 2 is a diagram explaining the principle of an active external distance measuring automatic focusing device. Figure 3 is the performance of the imaging spot on the photodetector. 4 is a circuit block diagram of an automatic focus adjustment device, FIG. 5 is a side view of a conventional zoom lens with an automatic focus adjustment device, and FIG. 6 is a front view of a conventional zoom lens with an automatic focus adjustment device. , Figure 7 is a distance measurement screen at the wide end of a conventional distance measurement device, Figure 8 is a distance measurement screen at the tele end of a conventional distance measurement device, and Figure 9 is a conventional distance measurement parallax. FIG. 10 is a perspective view of an embodiment for explaining the principle of the present invention. FIG. 11 is a diagram explaining the principle of dividing the projected light beam into two, which is a feature of the present invention. , Fig. 12 relates to the present invention and shows a distance measurement screen at the telephoto end when the subject distance is 3 m, and Fig. 13 relates to the present invention and shows a distance measurement screen at the telephoto end when the subject distance is 0. 6m at the telephoto end; Figure 14 is an optical cross-sectional view and optical path diagram of the light projection system in Figure 10 which is the first embodiment of the present invention; Figure 15 is the first embodiment of the present invention. An optical cross-sectional view and an optical path diagram of the light-receiving system of the example. Fig. 16 shows the spot image formation position on the light-receiving element. Fig. 17 shows the case of photographing a persimmon fruit at a close distance at the telephoto end. Figure 18 is a cross-sectional view showing a conventional light projection system; Figure 19 is a diagram showing distance measurement positions by beam division, which is a feature of the present invention; Figure 20 (A) is a diagram showing distance measurement positions; A diagram showing the image formation state on the light receiving element when the position indicated by 74 in Fig. 19 is at infinity, and Fig. 20 (B) shows the image forming state on the light receiving element when the position indicated by 74 in Fig. 19 is at a finite distance. Figure 21 is a graph for explaining the effect of the distance measuring device according to the present invention, Figures 22 and 23 are diagrams for explaining subjects that the distance measuring device according to the present invention is not good at photographing , FIG. 24 is a perspective view showing an embodiment of the present invention, and FIG. 25 is a side sectional view of a light projecting/receiving system related to the present invention. (In (Rono (L Relens) Bad Audience Figure 7/) (W Condolence/θ Hanging 1st Otsu Figure/7 Ward C,, 72

Claims (5)

[Claims] (1) A light-emitting element placed outside the light beam passing through the photographic lens, a light-emitting lens for projecting light from the light-emitting element onto the subject, and a light-receiving lens placed at a baseline length away from the light-emitting lens. and a light-receiving element that receives diffusely reflected light of the light beam imaged on the subject by the light-projecting lens by the light-receiving lens, and the device adjusts the focus of the photographing lens by the output of the light-receiving element, The light path projected onto the subject by the light emitting element and the projection lens is a region excluding the projection optical axis, and the luminous flux of an annular region is divided into a direction different from the luminous flux on the projection optical axis and projected. An automatic focus adjustment device characterized by: (2) A light-receiving lens is provided on the object side of the light-receiving element, and an optical unit for dividing an optical path is disposed in front of the light-receiving lens and the light projecting lens. automatic focusing device. (3) It has a light projection means for projecting a beam toward the object side, and a light receiving means for receiving the beam reflected from the object side, and the distance to the object is calculated according to the position of the beam received by the light receiving means. A distance measuring device for measuring a distance, comprising means for dividing the projected beam into two different directions, each having an annular region excluding a region on the optical axis and another region. range device. (4) The third aspect of the present invention is characterized in that the dividing means comprises an optical unit having a prism portion in part.
Distance measuring device described in section. (5) The distance measuring device according to claim 4, wherein the optical unit has a prism section at the center of the light receiving lens in front of the light receiving means.