JPS59193406A - Distance measuring device - Google Patents

Abstract

PURPOSE:To measure exactly a distance by providing a diffraction structure body in an optical system for projecting luminous flux for measuring distance, projecting plural diffracted lights generated by the structure body toward an object to be photographed, and photodetecting its reflected diffracted light by a photoelectric converter. CONSTITUTION:A light emitting source 3 rotates within some angle against a projecting lens 4, and a projecting luminous flux spot is scanned to a long distance side from a short distance side on the surface (ob) of an object to be photographed. The projecting luminous flux is diffracted by a diffraction grating 5, and a zero-order diffracted light 8 and + or - primary diffracted lights 10, 9 are generated. By changing an uneven quantity of the diffraction grating, it is also possible to make the intensity of three spots nearly equal, and when only the center part is mainly measured as to its distance, it is also possible to constitute so that there is a peak in the center spot, by weakening the + or - primary diffracted lights. The distance measuring range is expanded by a portion expanded horizontally of a distance measuring luminous flux 14, and the distance measuring luminous flux 14 can scan enough on the object to be photographed. In this way, a distance to the object to be photographed can be derived exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a distance measuring device used in optical equipment such as cameras, and in particular, a distance measuring light is projected from the device side toward an object, and is reflected by the object. This relates to a so-called active distance measuring device that determines the distance to an object by photoelectrically detecting light and sets the focusing state of the imaging optical system on the object to the correct and in-focus state. .

Figure 1 shows a conventional active distance measuring device, JP-A-54-1.
This is a technique disclosed in No. 13356. In the figure, ED is a light emitting element for projecting light, FD is a photoelectric conversion element for receiving light, LS, LS2 is a lens for the finder optical system, MRl is a half mirror, MR is a total reflection mirror, F
M is the frame for displaying the viewfinder field and distance measuring section, EY
indicates the photographer's eyes.

LS3 is a light projecting lens placed in front of the light emitting element, and the light from the light emitting device FiD1 passes through the lens LS3 and is reflected by the rotating mirror MR to project and scan the subject, and the reflected light from the subject is reflected by the rotating mirror MR. is focused by lens LS and mirror MR3
After being reflected on the surface of the light receiving element FD, the light is incident on the light receiving element FD.

LS5 is held in a lens barrel, as is well known in photographic lens systems, and is supported so as to be able to slide back and forth along the optical axis together with the lens barrel. AD is the aperture, SR is the shutter, PL is the film, spl is the spring that urges the lens barrel in the retracting direction, LG is the rack provided on the lens barrel, G is the binion that meshes with the rack LG, G2 is rotated in a ratchet that rotates together with the pinion a. Mg is a magnet controlled by a circuit described later, AM is a magnet M
It is rotatably supported by an armature lever that is attracted by g1, and a stop pawl AM is formed at one end to engage with the teeth of the ratchet wheel G2. sp is a spring that biases the stop pawl in the direction of engagement with the ratchet wheel G2. OB is an object at a close distance,
OB2 is an object to be photographed at a long distance.

FIG. 2 is a diagram of the output signal of the photoelectric conversion element FD, in which the horizontal axis is time (t) and the vertical axis is the output voltage (V). Q, is the output due to the reflected light from the short distance object OB, and Q,2 is the output due to the reflected light from the long distance object OB.

The mirror MR rotates in conjunction with the lens barrel, and the light from the light emitting element ED scans the subject from close range to infinity. The photoelectric conversion element PD receives reflected light from the subject, and when the peak value of its output signal is detected, the magnet hog is turned off, and the stop claw A of the Amachia lever is turned off.
M is pulled by spring SP and engaged with ratchet wheel G2, and binion G1. The movement of the lens barrel is stopped via the rack LG, and the position of the photographing lens LS is determined.

As described above, when a distance measuring light beam having a circular cross-sectional shape is directed toward a subject to measure a distance, there are the following problems.

In other words, as shown in Fig. 3, in a situation where two people 3a and 2b are located a little distance apart, the distance measuring light beam scanned from 1b to 1a will be The problem is that the distance to the two people cannot be measured because the distance between the two people is smaller than the correct L. For this reason, the photographer of the camera should set the camera so that one of the people is in the center of the screen, measure the distance, have the camera retain the distance measurement information in this state, and then correct the composition of the camera again. A series of photographic operations was required, including setting the camera to the desired state and taking the photograph.

The present invention proposes a distance measuring device for realizing an easy-to-use autofocus camera that solves the above-mentioned problems.

More specifically, the present invention realizes a distance measuring device in which the cross-sectional shape of the projected light beam is not circular but rectangular, thereby expanding the distance measuring range.

FIG. 4 shows a first embodiment of the present invention. In the same figure,
3 is an ID, a light emitting source such as a semiconductor laser, 4 is a light projecting lens, 5 is a phase type diffraction grating provided immediately after the light projecting lens, 6 is a light receiving lens, and 7 is a photoelectric conversion element. The light emitting source 3 is rotated within a certain angle with respect to the projection lens, thereby scanning the projected light flux spot from the near side to the far side on the object plane Ob. In the present invention,
Since the diffraction grating 5 is provided immediately after the projection lens,
The light beam for projection is diffracted by this diffraction grating 5, and 0th-order diffracted light 8 and ±1st-order diffracted light 1O29 are generated.

FIG. 5 shows an enlarged view of this diffraction grating viewed from the subject side.

Therefore, a distance measurement spot is generated on the subject Ob by these three diffracted lights, and this spot scans the subject surface as the light source rotates.

FIG. 6 shows the shape of the projected light spot on the object plane when the rotation of the light source is fixed at a certain angle.

Spot 12 by +1st-order diffracted light, spot 13 by -1st-order diffracted light on both sides of Subill by 0th-order diffracted light
is created, and the shape of the projected light spot becomes three times wider. This projection spot interval is determined by the period P of the diffraction grating provided immediately after the projection lens, and if the first-order diffraction angle is ψ, then the relationship Ps ihψ = λ (λ is the center wavelength of the projection light) tends to occur. The intensity of each spot light is determined by the amount of unevenness of the diffraction grating.

FIG. 7 shows the relationship (diffracted light intensity/incident light intensity) between the amount of unevenness and the diffraction efficiency of 0th-order and ±1st-order diffracted light. Therefore, by changing the amount of unevenness of the diffraction grating, these three spots can be made to have approximately the same intensity. or,
When trying to measure only the center of the spot, ±
It is also possible to make the first-order diffracted light a little weaker so that there is a peak at the center spot and weaker spots on the left and right sides.

Conversely, it is also possible to make the center weak and the left and right spots strong, in which case it becomes easier to detect the peak in the received light signal processing.

As described above, in the distance measuring device according to the present invention, a light beam having a horizontally long cross-sectional shape is projected onto the subject, and as the light source rotates, this light flux scans the subject. Therefore, as shown in Fig. 8, even for objects that cannot be conventionally measured, the distance measuring range is expanded by the horizontal spread of the distance measuring light beam in the present invention. ,
The distance measuring light beam 14 can sufficiently scan the subject.

In this embodiment, the shape of the light receiving surface of the light receiving center is also preferably horizontally elongated, corresponding to the fact that the light beam for projection is elongated laterally. This size should be such that the image 15, which is back-projected from the sensor onto the object plane through the light-receiving lens, has the same shape as the projected light flux, as shown in Figure 9, and at this time the light-receiving signal has a strong peak. Electrical signal processing for determining the presence L1 distance becomes easier.

FIG. 10 shows a second embodiment of the invention. The difference from the first embodiment is that a diffraction grating 17 is also provided in front of the light receiving lens.
The point is that this is provided. In this embodiment, unlike the first embodiment, a photoelectric converter 16 for light reception with a small light-receiving surface size is used to effectively achieve the same function as a photoelectric converter with a large horizontally elongated light-receiving area. I'm making you do it.

In the figure, the reflected light from each of the three spots projected onto the subject is diffracted again by the diffraction grating 17, and a portion of it is incident on the photoelectric converter 16. For example, the 11th
As shown in the figure (&), the reflected light 18 from the 5-pot object by the projecting light beam 8 is diffracted by the diffraction grating 17, but the 0th order diffracted light 19 enters the small light receiving area 16.

Further, as shown in FIG. 11(b), the reflected light 22 from the subject at the spot caused by the projection light beam IO is diffracted by the diffraction grating 17, and -1st order diffracted light 24 enters the light receiving area 16.

Similarly, although not shown, the light reflected from the subject at the spot by the projecting light m9 is diffracted by the diffraction grating 17,
Among them, the +1st order diffracted light enters the light receiving area.

Therefore, in this embodiment, unlike the first embodiment, although a photoelectric converter with a small light receiving area is used, due to the action of the diffraction grating 17, the photoelectric converter with an effectively large light receiving area is used. fulfills the same function.

As shown in FIG. 12, this diffraction grating 17
When the i converter 16 is back-projected onto the ``''C object through the light receiving lens and the diffraction grating, three light beams 26, 27.
It is desirable that the lattice constant (period) be such that the diffracted photoelectric converter images 29, 28, and 31 substantially overlap each other.

The present invention has been described above mainly with regard to the optical system, but regarding the electrical signal processing system, the invention has been described in Japanese Patent Application Laid-Open No. 54-113356.
The technology disclosed in can be used as is. The present invention realizes a high-performance distance measuring device that has a simple configuration and solves the problems of conventional distance measuring devices.

Furthermore, the diffraction grating structure that is effective in the present invention is not limited to the structure shown in FIG. 5, but includes, for example, a diffraction structure having a grating cross-sectional shape as shown in FIG. 13, and other sinusoidal uneven structures. Diffraction gratings etc. having .

Further, the location where the diffraction grating is provided does not have to be near the lens, but may be provided within the light projecting optical system and the light receiving optical system as appropriate.

Further, in this embodiment, a diffraction grating that mainly generates ○th order and ±1st order diffracted light is used, but more diffracted lights may be used.

In general, the present invention is not limited to the embodiments shown in FIGS. 4 and 10, and the present invention is not limited to the embodiments shown in FIGS. 4 and 10. This problem is solved by using the diffracted light from the grating to create a beam of light with a horizontally or vertically long cross-section.
It is also effective for other active distance measuring devices.

Furthermore, the present invention is not limited to spreading the light projection spot in the direction of the distance measurement base line length; for example, by rotating the diffraction grating in FIG. It is also possible to expand. In this case, the light-receiving photoelectric element must also be rotated within the plane by 90 degrees so that the shape of the light emitting spot and the light-receiving surface area are balanced.

[Brief explanation of the drawing]

Fig. 1.2 is an explanatory diagram of the conventional example, Fig. 11.12 is an explanatory diagram of the second embodiment, Fig. 13 is a cross-sectional diagram of a diffraction grating of another form, 3--One luminous flux light emitting source for distance measurement. ,
5.l'L--diffraction grating, 4.6--lens for ranging light beam, 7.16--photoelectric converter. Applicant Canon Co., Ltd.

Claims (2)

[Claims] (1) Distance measurement in which a light beam for distance measurement is projected toward an object, the reflected light from the object is received by a photoelectric converter, and the photographing lens is controlled to move to the in-focus position based on the output signal of the photoelectric converter. In the apparatus, a diffraction structure is provided in a light flux projection optical system for distance measurement, a plurality of diffracted lights generated by the diffraction structure are projected toward a subject, and the plurality of diffracted lights reflected by one subject are transmitted to the photoelectron. A distance measuring device characterized in that it is configured to receive light with a converter. (2) A distance measuring light beam is projected toward an object, and the reflected light from the object is received by a photoelectric converter. In the distance measuring device, a diffraction structure is provided in a distance measurement light beam input optical system that makes the distance measurement light beam reflected by the object enter the photoelectric converter, and a plurality of diffracted lights generated by the diffraction structure is A distance measuring device characterized in that the distance measuring device is configured such that the photoelectric converter receives the light.