JPS587964B2 - Kiyori Sokutei Souchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photoelectric focusing device for a reflex camera.

An electro-optical focusing device for a reflex camera, in which a portion of the light of the objective lens pupil is split through an annular reflector for the focusing device, and then a movable diaphragm and a movable Scanning devices with photoelectric receivers are well known.

This known device has the disadvantage that, due to the focusing device, the branched light beam components disappear for the recording.

At the same time, very small dot-like or slit-like parts of the subject image are involved in the measurement, so in order to increase the product of the field of view and the aperture to obtain a sufficiently large light flow, it is necessary to Large diameter sections have to be used for measurements and are therefore not suitable for other purposes.

Furthermore, objectives of different apertures and different focal lengths are each associated with a unique focusing device adapted to the objectives.

However, such a configuration comes with significant costs.

The object of the invention is to provide a focusing device for reflex cameras which does not have the above-mentioned drawbacks and which requires minimal technical outlay.

This object is achieved according to the invention by arranging at least one prismatic focusing plate as a correlator and a spatial frequency filter in the vicinity of the image plane of the objective lens of the camera in a photoelectric focusing device of a reflex camera. The light beam from the object is divided laterally by the different light beam deflection effects of the prism-shaped portions (for example, pyramid-shaped portions) of the focusing plate, and the light beams from the subject are divided into at least two optical paths among the laterally divided partial image beams. Each photoelectric receiver is arranged such that the output signals of these photoelectric receivers are push-pull and focused at selected spatial frequencies based on the physical or geometric beam splitting method used. the output terminal of the photoelectric receiver is connected to an indicating device and/or an adjustment device for displacing the objective lens of a camera along the optical axis; This is accomplished by directing the output signal of the photoelectric receiver to indicate or modify, or cause to indicate and modify, the adjustment state of the camera objective lens.

Note that an optical correlation device is formed by the objective lens, the prism focusing plate, and the photoelectric receiver.

At this time, the output of the photoelectric receiver system changes depending on the relative position of the imaging plane and the grating.

The reason is that the image of the object is a grid (spatial frequency filter)
When creating an image on the grating, an image of the object is created on the grating, the brightness of which is distributed in various ways. This is because it differs depending on the relative position between the grid and the grid.

Each image with a certain brightness distribution has a fixed spatial frequency spectrum attached to it, and when the image is out of focus (that is, the spatial frequency filter surface and the imaging plane of the objective lens do not match), , the low-frequency spatial frequency component is strong and the high-frequency spatial frequency component is suppressed, and as the image of the objective lens approaches the spatial frequency filter surface, the high-frequency component related to the image becomes strong, and the low-frequency spatial frequency component is suppressed. It goes so far as to suppress frequency components.

Now, the spatial frequency filter placed on the image receiving surface has the function of filtering the spatial frequency components corresponding to those lattice constants from the spatial frequency of the image of the object, so the spatial frequency components corresponding to the lattice constants The strength of the component changes depending on whether it is in focus or out of focus.

That is, the spatial frequency component filtered as above is
It has the greatest strength when it is in focus.

The output from the photoelectric receiver is therefore also correspondingly maximized.

The two receivers of a photoelectric receiver system are 180 degrees apart from each other.
It produces a push-pull output when stimulated by light streams that are out of phase by .

The output produced in this way is a mixture of strong steady light rays that are unrelated to whether the incident light stream is in focus or not, so the spatial frequency extracted to determine whether the incoming light stream is in focus is It is prepared for cases where it is difficult to recognize changes in relative intensity, and such steady light components are eliminated by employing the difference between two signals whose phases are shifted by, for example, 180°. Only the vibrating component of the extracted spatial frequency is doubled and extracted.

In this case, an optical beam deflection means, for example in the form of a pentaprism, can be provided between the prism type focusing plate (hereinafter referred to as prism pin 1 plate) and the Yoshimitsu electric receiver.

Regarding the optical path to the photoelectric receiver, it is advantageous to provide a concave mirror connected to a Penck prism, a field diaphragm and a condenser lens, respectively.

In order to use interchangeable lenses with different aperture areas, it is also possible to provide optical biasing means that allow optronic analysis of several aperture widths or regions.

Several photoelectric receivers can be provided which can be switched if necessary.

In a particular embodiment, the prism focusing plate is resiliently supported and means are provided in known manner for varying it in at least one coordinate direction.

The prism focusing plate can advantageously be designed as a non-periodic laser.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The novel apparatus of the present invention will be described below with reference to embodiments of the accompanying drawings.

The invention is based on the principle of optical correlation, which optical correlation device basically comprises an imaging system and at least one spatial frequency filter arranged close to the imaging plane of the imaging system. It consists of one arrangement, for example a prismatic focusing plate, such as an optical grating, and at least one photoelectric receiver system arranged after this arrangement.

The imaging system images the object to be measured onto the structure, which filters a spatial frequency from the object image that is determined according to its pitch (screen or grating pitch).

The filtered light beam stimulates a photoelectric receiver system, which generates an electrical signal proportional to the focus state of the object on the arrangement.

In FIG. 1, objective lens 2 focuses an image of an object (not shown) onto the surface of prism focusing plate 3. In FIG.

This different beam deflection effect of the prismatically shaped parts (for example pyramid shaped parts) results in an energy separation between each two object image points offset from each other by half the grating constant.

Also, due to the light beam deflection effect, exit pupils 28', 29', 30', and 31' (FIG. 2) are formed which are laterally shifted and partially overlap each other.

The outer part of the exit pupil, which is not useful for visual or unaided observation via the eyepiece 59, is imaged by lenses 57, 58 onto the plane in which the diaphragm 15, 16, which defines the field of measurement, is located.

These apertures are designed to match the appearance or field of view
. , 20 to 2.0 m, and the objective lens 2 having an average standard focal length is designed to form an image with a size approximately corresponding to the aperture area of the diaphragm.

Concentrators 13, 14 located behind guide the light beams passing through the apertures 15, 16 to one photoelectric receiver 6, 7, respectively.
The output signal of the photoelectric receiver is applied to a balanced amplifier (push-pull amplifier) 8.

The output terminal of the amplifier 8 is connected to an indicating device 9 for indicating the maximum of the difference signal of the receivers 6,7.

At the same time, the output of the amplifier 8 is also connected via a switch 10' to a servomechanism 10, which is actuated by closing the switch 10' and illuminates the objective lens 2 until the aimed object is brought into focus. Move along the axis.

The above-described servomechanism is capable of quickly and manually performing rough focusing while observing the pointing device, and then finely focusing by closing the switch 10'.

Also, at the output terminal of the amplifier 8, in place of the indicating device 9, there is a device that generates the following blinking signal outside the image field of view, that is, a device that aims the object at the center of the field of view and at the same time aligns it to the side of the retina of the naked eye. It is also possible to connect a light blinking device that generates a light blinking signal that utilizes the physiological optical property of the rod-like body, which is highly sensitive to brightness.

In FIG. 1, the new device for focusing is shown in one coordinate perpendicular to the optical axis.

It goes without saying that a second coordinate direction can also be involved in the measurement by mounting a receiver pair rotated by 90° with respect to the illustrated receiver pair.

This is especially necessary when the object to be aligned has a periodic structure parallel to one coordinate direction.

For an even clearer signal, the prism focus plate 3 can be formed aperiodically.

FIG. 2 shows the pupil condition resulting from the configuration of the prism focusing plate of the device shown in FIG. 1 when the prism focusing plate is viewed from below.

As can be seen from this figure, the eyepiece lens 59 is located at a portion where the light rays corresponding to four adjacent pupils overlap.

In contrast, the two photoelectric receivers 6, 7 are each spatially arranged so that they receive only one pupil's rays.

Since alternating signals are obviously easier to process (especially amplify) than direct current signals, the measurement signal is obtained in the form of an alternating signal.

For this purpose, the prism focusing plate can be elastically supported by an elastic wire 60, as shown in FIG.

In each coordinate direction defined by the photoelectric receiver pair, a drive for acting on the prism focusing plate is arranged in the form of a piezoelectric rod 18, which is energized by an oscillator (not shown) and causes the prism to move. Displace the focusing plate vibrokinetically.

The device shown in FIG. 3 is provided for oscillating movements in two mutually perpendicular directions.

4 to 7 show examples of the structure of a reflex camera of the device according to the invention.

In this case, a roofed and easily replaceable Penck prism 35 of known type is used, and the measuring base lines of the two objectives 2 and 2' of different apertures are used, so that in each case the measuring beam is It is designed to go to two photoelectric receivers 6 and 7.

FIG. 4 shows the ray path in the pentagonal prism 35 essentially expanded, whereas FIG. 7 shows the refracted ray path in side view.

5 and 6 show the back and front sides of the prism 35. FIG.

Light rays passing near the periphery of objective lens 2 (edge rays)
passes through the reflecting mirror 23, reaches the focusing plate 3, then passes through the condensing lens 32, and in turn passes through the roof-like surface 50 of the pentagonal prism 35, and the 2.
In the two reflecting mirrors 37, 38 and the two concave mirrors 39, 40 provided on the prism surface 61, the prism surface 36 again
The exit windows 41, 42 on the lower side of the reflectors 37, 38 are reflected back down the sides of the mirrors 37, 38 for intermediate imaging in the plane of the apertures 15, 16, as already mentioned in FIG. exit.

The condensing lenses 13, 14 image the exit pupil belonging to a portion (FIG. 2) of the exit pupil region of the objective 2 at the location of the reflectors 39, 40 onto the photoelectric receivers 6, 7.

Between the reflectors 39, 40, the light rays corresponding to the overlapping adjacent pupil areas (FIG. 2) exit through the prism surface 61 and enter the visual observation eyepiece 59 belonging to the prism surface. enter.

In FIG. 4, the rays corresponding to the objective 2' with a smaller aperture are indicated by single arrows, and the rays corresponding to the objective 2 with a larger measurement reference line are indicated by double arrows.

Because the former ray has a smaller divergence than the latter ray, after being reflected by the concave mirrors 39 and 40, it is laterally reflected by the prism 35 before exiting from the windows 41 and 42. Additional total reflection occurs at the joined plates 43, 44 (FIG. 6).

The light emitted from the exit window is collected by the exit surfaces 55 and 56 (Fig. 4).
reaches a total internal reflection prism with .

The purpose of the condensing exit surfaces 55, 56 is to reflect only the light of the measuring beam from the areas 39, 40, while avoiding unwanted rays from the area of the eyepiece 59 which have a small inclination with respect to the normal to the hypotenuse of the prism. This is to allow the light to penetrate without being reflected.

The measuring beam reaches the photoelectric receivers 6, 7 via subsequently arranged condensing lenses 13, 14.

FIGS. 8 and 9 show other embodiments of the optical path configuration in a pentaprism 35 having a roof-like ridge.

As in the case shown in FIGS. 4 to 7, the rays of the larger aperture (double arrows) are reflected by two reflectors 45 and 46 provided on the prism surface 36.

However, these mirrors 45, 46, in contrast to the mirrors 37, 38, cover the entire height of the sides of the prism surface 36.

The light rays then impinge on concave mirrors 39,40.

However, the concave mirrors 39, 40 here allow the rays to pass through the otherwise useless surface 49 near 51 and 52 to the window 41,
It is slanted so that it can be ejected through instead of 42.

The light rays of the small aperture then pass through reflectors 45, 46, which are also present in surface 36, and strike concave mirrors 39, 40;
However, instead of the plates 43, 44 (FIG. 6), they are normally guided through the roof surface 50 to the window 5L52.

In this new device, a second switch can be connected or coupled to the switch that closes the control circuit for the focusing drive and can be linked to the exposure measuring device inside the camera. There are advantages.

This ensures that the same image field is used for distance and exposure measurements.

Preferred embodiments for carrying out the present invention are summarized as follows.

(1) An optical beam deflecting means is provided between the prism focusing plate 3 and the photoelectric receivers 6 and 7, such as a pentaprism 35.
A device according to the claims, provided in the form of:

(2) Concave mirror 39.40 field diaphragm 15.16 joined to the pentaprism 35 in the optical path up to the photoelectric receivers 6 and 7
and a condenser lens 13, 14, respectively.

(3) The scope of claim 1 or 2 further comprises an optical biasing means 35 that enables optronic analysis of a plurality of aperture widths 2 and 2' in order to utilize interchangeable lenses with different aperture areas. The device described.

(4) A device according to claim 1 or claim 3, comprising a plurality of photoelectric receivers which can be switched if necessary.

(5) At least one means 18 of known type for resiliently supporting and varying the prism focusing plate 3;
A device as claimed in the claims, which is arranged in two coordinate directions.

(6) The device according to the claims, in which the prism focusing plate 3 is formed into an aperiodic Lasque.

(7) An apparatus according to claim 1, characterized in that a light beam blinking device is connected to the output terminal of the amplifier 8, and the blinking signal is visible in or to the side of the image field of view of the observer.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the principle of the present invention, Fig. 2 is a drawing showing the position of the exit pupil, Fig. 3 is a drawing showing the support and driving part of the prism focusing plate, and Fig. 4 is a drawing showing the state of passage of light rays in the Penck prism. The expanded drawing, Figure 5, is the rear view of the pentaprism.
FIG. 6 is a front view of the pentaprism, FIG. 7 is a side view showing the path of light rays in the pentaprism, and FIGS. 8 and 9 show other examples of the light path configuration in the Penck prism having a roof-like ridge. FIG. 2... Objective lens, 3... Prism focusing plate, 6, 7... Photoelectric receiver, 8...
...Amplifier, 9...Instruction device, 10...
・Adjusting device, 10'...Switch, 13, 14
...Condensing lens, 15,16...Aperture, 35...Penta prism, 36,61...
... Prism surface, 37, 38, 45, 46...
・Reflector, 39, 40... Concave mirror, 41, 42
...Emission window, 43,44...Plate, 50
...Roof surface, 51, 52 ... Window, 5
7, 58... Lens, 59... Eyepiece.

Claims (1)

[Claims] 1. In a photoelectric focusing device for a reflex camera, as a component of the optical correlation device, at least one prism-type focusing plate is arranged near the imaging plane of the objective lens of the camera as a correlator and a spatial frequency filter. This focusing plate laterally splits the light beam from the object by the different beam deflection effects of the prism, and one photoelectric receiver is installed in each of at least two optical paths of the laterally divided partial image light beams. with the output signals of these optoelectronic receivers push-pull and in focus with respect to the spatial frequency selected based on the physical or geometric beam splitting method used. and connecting each output terminal of the photoelectric receiver to an indicating device or an adjusting device for displacing the objective lens of the camera along the optical axis, or the indicating device and the adjusting device;
The above-mentioned device is characterized in that the output signal of the photoelectric receiver is guided to these devices to instruct or modify or to instruct and modify the adjustment state of the objective lens of the camera.