JPS5922922B2 - Optical system focal position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting the focal position of a camera, optical measuring instrument, sleep or other optical system.

The light image that has passed through the optical system is projected onto two deflection prisms that are alternately combined, and divided images that are generated depending on the focusing state on the prisms are projected onto two photoelectric elements with scanning slits. As an example of a device that detects the focal position of an optical system by projecting the light onto the respective objects, there is a device described in Japanese Utility Model Publication No. 46-24925.

In addition, the light from the light source, which is the object, is passed through a deflection prism to form two beams of light in different directions.The light beams are incident on the eye during sleep, and the reflected light from the fundus of the eye is passed through a lens system and onto the scanning slit. The focal position of the eye to be examined is detected by forming an image, receiving the light corresponding to each light beam by two photoelectric elements at the passing position of the slit, and comparing the phases of the voltage pulses applied to each photoelectric element. has also been proposed.

However, all of these known techniques require two photoelectric elements, and these photoelectric elements are very expensive, especially when used to detect weak light, and the detection device itself is expensive. I have no choice but to.

Furthermore, since two detectors each including a photoelectric element are used, the entire device becomes large, and it is difficult to make adjustments that take into account differences in sensitivity, fatigue, etc. between the two detectors.

SUMMARY OF THE INVENTION In view of the deficiencies of the prior art, it is an object of the present invention to provide an apparatus that can detect the focal position of an optical system using only one photoelectric element. For example, when the light images passing through the optical system are projected onto two deflection prisms that are combined alternately, depending on the state of formation of the light images on the prisms, when the prisms are in the focused position, two deflection prisms are projected. The images passing through the deflection prism coincide with each other, and if the prism is out of focus, the two image parts will be misaligned.

In the present invention, when such a divided image method is used, the divided images are projected onto the slits while scanning the slits corresponding to each divided image portion at a constant interval, that is, with a phase difference. The passing light is received by one photoelectric element. In this case, the prism position becomes the detection surface, and if this detection surface is at the focal point, the voltage pulses applied to the photoelectric element will be regular depending on the positional difference of the slits. Also, if the prism is out of focus, the pulse interval will be different from the slit phase difference. The light from the photoelectric is passed through a deflection prism to form two beams with different directions, and these beams are incident on the human eye.The reflected beam from the fundus is passed through a lens system to form an image at a common position with respect to the fundus. In this method, the fundus of the eye to be examined becomes the detection surface, and if the eye to be examined is emmetropic, the two light beams will be focused in the same phase, but if the eye is nearsighted or farsighted, they will be focused in different phases. If configured to image, the focal position can be detected in the same manner as described above.

Furthermore, when the light image that has passed through the optical system is focused on the detection surface, the two image parts have a certain distance, that is, a phase relationship, and the focal position is off the detection surface. In some cases, it is also possible to adopt a configuration in which the two image portions deviate from the above-mentioned fixed phase relationship in either direction, and in this case, the scanning slits corresponding to the two image portions may be arranged as described above. They may be provided in a phase relationship different from the fixed phase relationship, for example, at the same position.

The focal position detection device for an optical system of the present invention projects a light beam from a light source onto a detection surface as two light beams with different directions, and depending on the focusing state on the detection surface, the focal position is adjusted to the detection surface. If they have a predetermined phase relationship with each other, and the in-focus position deviates from the detection surface in one direction, there is a positional deviation in one direction from the predetermined phase relationship, and if it deviates in the other direction, there is a positional deviation in the opposite direction. an optical system including a deflection prism that forms a light source image consisting of two parts; a single photoelectric conversion element that receives the light beam of the optical system; The predetermined phase relationship includes a slit scanning means that combines slits in pairs with different phase relationships and alternately guides the two light beams to the photoelectric conversion element, and a phase detection unit that detects the phase of the output signal of the photoelectric conversion element. and a focusing means for performing focusing based on the phase detected by the phase detecting means.

Embodiments of the present invention will be described below with reference to the drawings.

Figures 1 and 2 show an example of a device for detecting the imaging state of a subject S, in which 1 is a lens that can be moved in the optical axis direction Tc, 2 and 3 are lenses that are combined in opposite directions. In the deflection prism, a plane P passing through the intersection of the slopes of prisms 2 and 3 and perpendicular to the optical axis constitutes a detection plane, and depending on the image formation state of the subject S on this plane P, the image of the subject S is When the image is focused on P, the images of the subject S passing through the prisms 2 and 3 coincide with each other as shown in Figure 3a, and the images of the subject S
If the in-focus position of the image of subject S deviates from the plane P to the left or right in FIG. causing misalignment. The light passing through this prism passes through a relay lens 4 and is co-imaged onto a slit plate 5. As shown in FIG. 2, the slit plate 5 has a plurality of slits formed at radial positions corresponding to the image portion passing through the prism 3 and at radial positions corresponding to the image portion passing through the prism 3. The slit 5a is formed at regular intervals in the circumferential direction, and the slit 5b is formed at an intermediate position between the slits 5a.

A photoelectric element 6 is arranged behind the slit plate 5 at a position that receives light passing through the slits 5a and 5b. Therefore,
When the image portions passing through the prisms 2 and 3 are in the same phase when viewed in the scanning direction of the slits 5a and 5b, as shown in FIG. This refers to voltage pulses at regular intervals as shown in . If the two image parts are shifted to the left or right as shown in FIG. 3b or c, the photoelectric element 6 is shifted as shown in FIG.
The intervals between the voltage pulses that occur are irregular. By comparing the phase of this pulse using a phase detection circuit (not shown), it is possible to know the deviation between the detection plane and the focal plane, and by moving the lens 1 using this signal as input,
The focal position can be detected automatically. 5 and 6 show an example of performing an eye examination using the apparatus of the present invention, in which light from a light source 11 passes through a lens 12, a target opening 3, and a lens 14, and is reflected by an oblique perforated mirror 15. , enters the eye 17 through the objective lens 16 and forms a target image on the fundus of the eye.

The light reflected by the fundus of the eye 17 to be examined is transmitted through the objective lens 16,
The light passes through the hole of the perforated mirror 15 and the lenses 18, 19, and 20, and is imaged onto the slit plate 21. The slit plate 21 has the same structure as the slit plate 5 in the previous example, and the photoelectric element 22 is arranged behind it in the same manner as in the previous example.
The target 13 has two transparent parts 13 as shown in FIG.
a, 13b, and a deflection prism is disposed in one of the transparent parts 13b, and the light from the light source 11 is projected onto the fundus of the eye 17 to be examined as two luminous fluxes in different directions.

When the target image is focused on the fundus, the images from the two light beams have the same phase as in the previous example, and when the focal position is away from the fundus, the two images have different phases. causing misalignment. Thus, as in the previous example, detection of the focal position is possible. However, in this example, to automatically detect the focus position, target 1
3 and the lens 19 must be moved in synchronization. FIG. 7 shows a modification of the target 13 in the apparatus shown in FIGS. 5 and 6.

That is, in the target 23, the light-transmitting part 23a and the light-transmitting part 23b having a deflection prism are formed with a distance, that is, a phase difference, in the lateral direction. In the focused state, the image in FIG.
Or the distance between images changes as shown by c. When using this target 23, the 9th slit plate is used as the slit plate.
As shown in the figure, it is possible to use a device in which slits corresponding to two images are formed on the same radius line, and the interval between the slits on the slit plate and the phase difference between the images at the focused position are appropriately determined. In this case, regular output pulse intervals as shown in FIG. 4A can be obtained at the in-focus position, and irregular pulse intervals as shown in FIGS. 4B and 4C can be obtained at out-of-focus positions.

As described above, according to the present invention, it is possible to detect the focal position of an optical system by using only one photoelectric element, and the device used can be used in a large amount of space compared to conventional devices. Becomes cheaper.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the optical system arrangement showing an example of a focal position detection device of an optical system that has passed the present invention, Fig. 2 is a front view showing a scanning slit plate and a photoelectric element, and Fig. 3 is a top view of the slit plate. 4 shows the output pulses obtained according to the imaging state, and FIG. 5 shows an example in which the focal position detection device of the optical system to which the present invention is applied is used for optometry. Schematic diagram, FIG. 6 is a front view showing an example of the target used in FIG. 5, FIG. 7 is a front view showing another example of the target, and FIG. 8 is an image obtained using the target in FIG. 7. FIG. 9 is a front view showing an example of a slit plate used with the target of FIG. 7. S...Subject, 1...Luns, 2,3...
... Deflection prism, 4 ... Relay lens, 5 ... Slit plate, 6 ... Photoelectric element.

Claims (1)

[Claims] 1 The light beam from the light source is projected onto the detection surface as two light beams with different directions, and depending on the focusing state on the detection surface, if the in-focus position is on the detection surface, they have a predetermined phase relationship with each other. , if the in-focus position deviates from the detection surface in one direction, there is a positional deviation from the predetermined phase relationship in one direction, and if the in-focus position deviates from the detection surface in the other direction, there is a positional deviation in the opposite direction.
An optical system including a deflecting prism that forms a light source image consisting of two parts, a single photoelectric conversion element that receives the light beam of the optical system, and a predetermined phase relationship corresponding to the light beam of each image part. slit scanning means that combines slits in pairs with different phase relationships and alternately guides the two light beams to the photoelectric conversion element; a phase detection means that detects the phase of the output signal of the photoelectric conversion element; 1. A focus position detection device for an optical system, comprising a focusing means for performing focusing based on a detected phase by the detection means.