Focusing mechanism

The present invention relates to, for example, a bifocal focus adjustment mechanism incorporated in a lens group of a digital camera.

When a near person is imaged in the lower half of the screen and a distant landscape as a background is imaged in the upper half with a digital camera or the like, there is a technique of correcting the focus by so-called tilt correction. When the tilt correction is performed by a camera back equipped with an image pickup device, conventionally, a tilt mechanism is usually provided at a connecting portion between the camera body and the camera back.

However, in such a configuration, since the camera becomes large in size, a proposal to provide a tilting mechanism in the camera back is disclosed (see, for example, Patent Document 1). In this case, an image sensor is provided in which an image sensor is built in a camera back that can be attached to and detached from the camera body, and the image pickup surface of the image sensor is set as the optical axis in a state where the center of the image sensor coincides with the shooting optical axis. It has a built-in tilting mechanism that includes a tilting mechanism that tilts around orthogonal axes.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 9-331476</text></patcit>

<p> By the way, in recent years, with the diversification of needs, there is a demand for a novel idea that has a simpler configuration and can realize correction. That is, it has become desired that such a tilt correction can be realized even with an integrated digital camera having an image sensor inside the camera body. However, since space is limited in such a digital camera, the above-mentioned conventional tilting mechanism cannot be applied as it is.</p><p> The present invention has been made in view of such circumstances, and an object of the present invention is to provide a bifocal focus adjustment mechanism having an extremely simple configuration.</p>

<p> In the focus adjustment mechanism according to the present invention, a focus adjustment plate made of a single optical material having at least an inclined portion in which an incident surface and an exit surface form a predetermined inclination angle is arranged between a lens and an image sensor. In the inclined portion of the focus adjusting plate, the photographing light transmitted through the thin-walled portion is incident on the image sensor as short-distance photographing light, while the photographing light transmitted through the thick-walled portion is incident on the image sensor as long-distance photographing light. I am trying to make it incident.</p><p> According to such a configuration, the photographing light transmitted through the thin-walled portion of the focus adjustment plate arranged between the lens and the image sensor is incident on the image pickup element as short-range photographing light, and the photographing light transmitted through the thick-walled portion. Is incident on the image sensor as long-distance shooting light, so that the upper half of the image sensor can clearly shoot a distant landscape such as the background, and the lower half can clearly shoot a nearby person, both near and far. Focus correction (tilt correction) is possible.</p><p> Further, preferably, the focus adjusting plate further includes a parallel portion in which the incident surface and the exit surface are formed in parallel, and by moving the focus adjusting plate, either the inclined portion or the parallel portion is provided. The shooting light may be transmitted to the camera.</p><p> According to such a configuration, by transmitting the photographing light through the inclined portion of the focusing adjustment plate, the above-mentioned tilt correction becomes possible, and by transmitting the photographing light through the parallel portion of the focusing adjusting plate, the photographing light is transmitted. It can also be used for shooting without tilt correction.</p>

<p> The focus adjustment mechanism according to the present invention captures a lens and a focus adjustment plate made of a single optical material in which the entrance surface and the exit surface form a predetermined inclination angle and the wall thickness changes from a thin portion to a thick portion. It is arranged between the element and the shooting light transmitted through the thin part of the focus adjustment plate is incident on the image pickup element as short-range shooting light, while the shooting light transmitted through the thick part of the focus adjustment plate is incident with the long-distance shooting light. Since the light is incident on the image pickup element, the upper half of the image pickup screen can clearly capture a distant view, and the lower half can clearly capture a nearby person.</p>

Hereinafter, the focus adjusting mechanism according to the best embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of a focus adjustment mechanism, where reference numeral 1 is a diaphragm, 2 is a lens, 3 is a focus adjustment plate, 4 is an infrared cut filter, and 5 is an image sensor such as a CCD or CMOS. The focus adjusting plate 3 is made of a single piece of optical material in which the incident surface 3a and the exit surface 3b form a predetermined inclination angle R1, and either the incident surface 3a or the exit surface 3b (in the illustrated example, the exit surface). 3b) is substantially orthogonal to the optical axis direction, and the focus adjustment plate 3 is arranged between the lens 2 and the image pickup element 5, and the image pickup element 5 is erected so as to be orthogonal to the optical axis direction. ing.

According to such a configuration, the photographing light transmitted through the thin-walled portion 31 of the focus adjustment plate 3 arranged between the lens 2 and the image pickup element 5 is incident on the image pickup element 5 as the short-range photography light 6, and is thickened. Since the photographing light transmitted through the part 32 is incident on the image sensor 5 as the long-distance photographing light 7, for example, as shown in FIG. 2, the upper half of the imaging screen clearly captures a distant view, and the lower half captures a clear image. It is possible to take a clear picture of a nearby person and adjust the focus of both near and far.

As described above, the extremely simple configuration in which one focus adjustment plate 3 is arranged between the lens 2 and the image sensor 5 enables both near and far focus correction (tilt correction), so that a digital camera can be used. It can be formed compactly and can be provided at low cost.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the technical matters described in the claims.

For example, although not shown, in the focus adjusting plate 3 as described above, a portion where the incident surface 3a and the exit surface 3b are parallel to each other is further provided, and the shooting light is transmitted through the parallel portion to cause the tilt as described above. It can also be used for shooting without correction.

Further, the focus adjusting plate 3 can have any shape as long as the incident surface 3a and the exit surface 3b form a predetermined inclination angle R1, and the incident surface 3a or the exit surface 3b is the photographing light. It does not have to be substantially orthogonal to 6c and may be placed at any angle.

The focus adjustment mechanism according to the present invention uses a lens and an image pickup element as a focus adjustment plate made of a single optical material in which the entrance surface and the exit surface form a predetermined inclination angle and the wall thickness changes from a thin portion to a thick portion. The shooting light transmitted through the thin part of the focus adjustment plate is incident on the image pickup element as short-range shooting light, and the shooting light transmitted through the thick part is incident on the image pickup element as long-range shooting light. By doing so, both near and far focal points are corrected (tilt correction), so that the optical system can be configured extremely compactly, which is particularly useful for digital cameras and the like.

The focus adjustment mechanism according to the present invention uses a lens and an image pickup element as a focus adjustment plate made of a single optical material in which the entrance surface and the exit surface form a predetermined inclination angle and the wall thickness changes from a thin portion to a thick portion. The shooting light transmitted through the thin part of the focus adjustment plate is incident on the image pickup element as short-range shooting light, and the shooting light transmitted through the thick part is incident on the image pickup element as long-range shooting light. By doing so, both near and far focal points are corrected (tilt correction), so that it can be widely applied to technical fields such as small cameras that require an extremely compact optical system.

<figref num="1">Configuration explanatory view of the focus adjustment mechanism according to one embodiment of the present invention.</figref><figref num="2">Explanatory drawing of the same bifocal imaging screen</figref>

Code description

2 Lens 3 Focus adjustment plate 3a Incident surface 3b Exit surface 31 Thin-walled part 32 Thick-walled part 5 Image sensor 6 Short-range shooting light 7 Long-range shooting light