JPH0277001A - Prism for video camera - Google Patents

Abstract

PURPOSE:To preclude a ghost and a flare which appear accompanying the size reduction of a compound spectral prism by carrying out light shielding processing for the corner part between an incidence surface and a projection surface and its peripheral part against the photodetection surface of an image pickup element. CONSTITUTION:A 1st prism 1 and a 2nd prism 7 are joined together on a surface 7, which is a spectral surface. In this cross section of the 1st prism 1, a surface 6 containing the longest side is the incidence surface where light beams 9 and 10 which are converged by a lens are incident and a surface 5 containing the shortest side adjoining to the longest side is a projection surface for light which is diffused spectrally is incident. The photodetection surface of a CCD 3 faces the projection surface 5 across the 2nd prism 2 and the photodetection surface of a CCD 4 faces the surface 7 across the 2nd prism 2. The corner part 16 of the reflecting surface 5 and corner part 16 is shielded from light in the incidence surface 6 of this prism to prevent light 10 from being reflected again by the incidence surface 6. Consequently, the ghost and/or flare which is generated when the light 10 is photodetected by the CCD 3 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a prism for a video camera, and more particularly to a prism for a video camera suitable for a small handheld video camera.

(Prior Art) With the recent development of electronics technology, electronic components such as image sensors have become smaller, and video cameras that use such electronic components have also become smaller and more handheld types have been manufactured. Ta.

On the other hand, in parallel with the miniaturization of video cameras, the resolution of video cameras is also increasing.

This is because a clearer image can be obtained during playback after imaging.

Incidentally, in news video cameras and the like that require particularly high resolution, a composite spectroscopic prism consisting of a plurality of prisms is used to separate the light focused by the lens and improve the resolution.

One such composite spectroscopic prism is shown in FIG.

In Figure 3, 11 is the light 9.10 that is focused by the lens.
I2 is a prism connected to the first prism 11 (hereinafter sometimes referred to as a second prism),
3 and 4 indicate image pickup devices (hereinafter sometimes referred to as CCDs), respectively.

The light 9 collected by a lens (not shown) is separated by a first prism and a second prism, and the light received by the CCD 3 is converted into a luminance signal, and the light received by the CCD 4 is converted into a color signal, for example. , and then electrically synthesized.

(Problems to be Solved by the Invention) A high-resolution video camera having such a composite spectroscopic prism is a large-sized one such as a news video camera, and the composite spectroscopic prism used is also large.

Therefore, in order to improve the resolution of a small handheld video camera, it is conceivable to use a compact composite spectroscopic prism that matches the dimensions of the small video camera.

However, if the size of the compound spectroscopic prism built into the video camera is set so that the exit surface of the light to be separated is the same size as the light receiving surface of the COD, images called ghost and/or flare may appear in the resulting image. and/or light appears, ii! lii statue is disturbed.

This is because in conventional large composite spectroscopic prisms, CCD
This is because stray light that was not received by the CCD, for example, light from a light spot far away from the optical axis of the lens, can now be received by the CCD due to the miniaturization of the compound spectroscopic prism.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to prevent stray light from being received by a CCD, which causes ghosts and/or flares that appear with the miniaturization of composite spectroscopic prisms, and to improve the resolution of small, hand-held video cameras. The purpose of the present invention is to provide a prism for a video camera.

(Means for Solving the Problems) The disadvantages associated with the miniaturization of the composite spectroscopic prism described above can be eliminated by a video camera prism having the configuration of the present invention.

That is, the present invention provides a composite spectroscopy prism for a video camera consisting of a prism of 2 A surface including the shortest side adjacent to the longest side is formed as an exit surface of the light to be separated, and the size of the exit surface is the same as the light receiving surface of an image sensor used in a video camera. The angle between the incident surface and the exit surface is adjusted to prevent light that is reflected far off the optical axis from being re-reflected on the incident surface and received by the image sensor. This prism for a video camera is characterized in that a light-shielding process is applied to the light-receiving surface of an image sensor at the portion and the surrounding portion thereof.

Such a prism for a video camera is suitable for a small video camera with a lens bank focus of 25 mm or less.

(Function) The exit surface of the first prism constituting the composite spectroscopic prism is
As shown in Fig. 3, when the light receiving surface of the CCD 3 is sufficiently larger than the light receiving surface of the CCD 3, the light 10 from a light spot far away from the optical axis of the lens is not received by the CCD 3, so a clear image can be obtained. can be obtained.

On the other hand, if the compound spectroscopic prism is made smaller and the exit surface 5 of the first prism 1 becomes as large as the light-receiving surface of the CCD 3, as shown in FIG. Light of 1° from a point or the like is reflected by the exit surface 5 and re-reflected by the entrance surface 6 and received by the CCD 3, appearing as a ghost and/or flare.

In this regard, in the present invention, light shielding is applied to the peripheral portions of the reflective surface 5 and the corner portions 16 on the incident surface 6 to prevent the light IO from being re-reflected on the incident surface 6.

As a result, ghosts and/or flares that occur when the light IO is received by the CCD 3 can be prevented.

(Example) The present invention will be explained in more detail using FIG.

In FIG. 1, the first prism 1 and the second prism 2 are joined at a surface 7, and the surface 7 serves as a spectral surface.

In the +A11Ji surface of the first prism 1, the surface 6 including the longest side is the incident surface on which the light 9.10 condensed by the lens enters, and the surface 5 including the shortest side adjacent to the longest side is the incident surface. This is the light exit surface.

The light receiving surface of the CCD 3 corresponds to the exit surface 5, and the light receiving surface of the CCD 4 corresponds to the surface 7 via the second prism 2.

In such a first prism, the exit surface 5 has approximately the same size as the light receiving surface of the CCD 3, and the entrance surface 6 has:
A corner 16 with the injection surface 5 and a peripheral portion thereof are cut out to form a cutout 8.

Incidentally, the exit surface 5 in the present invention refers to a surface that is not subjected to the above-mentioned light shielding treatment or the like and from which the separated light can exit.

Further, conventionally, the corners of the prism have been chamfered to protect the prism, but such chamfering cannot achieve the light shielding effect described later.

Next, the operation of the composite spectroscopic prism according to this embodiment shown in FIG. 1 will be explained.

When the light condensed by the lens enters the composite spectroscopic prism shown in FIG. , the light transmitted through the spectral plane 7 is the second
The light passes through the prism 2, is received by the CCD 4, and is converted into a color signal.

On the other hand, the light reflected from the surface 7 is reflected from the entrance surface 6 and is reflected from the exit surface 5.
The light is emitted from the CCD 3, is received by the CCD 3, and is converted into a luminance signal.

Note that the light received by the CCD 3 is converted into a color signal, and the CCD 4
The light received by each of the two may be converted into a luminance signal.

Further, light 10 from an image or a light spot far away from the optical axis of the lens is reflected by the surface 7 and further reflected by the exit surface 5 to reach the cutout portion 8 .

The light 10 that reaches the cutout 8 is scattered and exits the exit surface 5.
The light is not emitted from the camera and is not received by the CCD 3.

In this way, according to the composite spectroscopic prism according to the present example shown in FIG. Therefore, it is possible to prevent ghosts and/or flares that appear when the light 10 is received by the CCD 3,
You can get high-resolution images.

On the other hand, in the small video camera prism shown in FIG. 4, in which the corner 16 of the entrance surface 6 and the surrounding area are not subjected to any light shielding treatment, the image or light spot that is far away from the optical axis of the lens is The reflected light 10 from the exit surface 5 is re-reflected at the corner 16 of the entrance surface 6 and its surrounding area, exits from the exit surface 5, and is received by the CCD 3, resulting in ghost and/or flare. Appears as.

In addition, in the large compound spectroscopic prism used in conventional large video cameras, ghosts and flares do not appear on the incident surface of the first prism, even if no light shielding treatment is applied to the corner with the exit surface and the surrounding area. Very few.

This is because the exit surface of the first prism relative to the light receiving surface of the CCD 3 is sufficiently large. That is, in the small compound prism shown in FIG. 4, even if the light 10 that causes ghosts and/or flares to appear enters the conventional large compound prism shown in FIG. This is because the light is emitted from a direction or position where the light is not received by the light receiving surface.

In the composite spectroscopic prism according to the present embodiment shown in FIG. 1, in order to prevent the light 10 from being re-reflected at the incident surface 6, the corner portion 16 and the surrounding portion thereof are cut out to form a cutout portion 8. Although light is blocked by using the method shown in FIG. 2, light can also be blocked by the method shown in FIG.

FIG. 2 shows a cross section of the first prism 1, and the second
Figure (a) shows a piece of glass 14 with a sand bath on one side joined to a portion corresponding to the corner 16 and its periphery;
In b), a portion 15 corresponding to the corner portion 16 and its periphery on the incident surface 6 is covered with sand to perform light shielding treatment.

These light shielding treatments are effective when the exit surface 5 does not have a cutout, as there is no cutout in the exit surface 5, as in the cutout 8 shown in FIG.

In FIG. 1, a cutout 13 formed near the corner of the exit surface 5 and the surface 7 is also used for light shielding, and the cutout 13 makes it possible to obtain an even clearer image.

In such a composite spectroscopic prism of the present invention, the exit surface 5 is CC
Since it can be miniaturized to approximately the same size as the light receiving surface of the D3, it can be suitably used in small handheld video cameras, especially small video cameras with a lens bank focus of 25 mm or less.

(Effects of the Invention) According to the present invention, it is possible to prevent harmful effects such as ghost and/or flare that appear due to the miniaturization of a composite spectroscopic prism, and therefore it is possible to improve the resolution of a small handheld video camera.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a composite spectroscopic prism according to an embodiment of the present invention, Fig. 2 is a sectional view of an entrance prism showing another embodiment of the invention, and Fig. 3 is a sectional view of a conventional large-scale video camera. FIG. 4 shows a cross-sectional view of the composite spectroscopic prism used, and FIG. 4 shows a cross-sectional view of a composite spectroscopic prism showing a comparative example of the present invention. In the figure, ■...Incoming prism (first prism), 2...Second prism
Prism, 3.4... Image pickup element, 5... Exit surface of first prism 1, 6... Entrance surface of first prism 1, 16... Corner between entrance surface 6 and exit surface 5. . Patent Distributor Co., Ltd. Representative Koshina Iiyama Bunji Kobayashi

Claims (1)

[Claims] A composite spectroscopic prism for a video camera consisting of one or two prisms, the entrance prism into which the light condensed by the lens of the video camera enters, the longest side of the prism in its cross section. The surface including the shortest side adjacent to the longest side is formed as the exit surface of the light to be separated, and the size of the exit surface is the same as the light receiving surface of an image sensor used in a video camera. They are formed to have approximately the same size, and in order to prevent light that is reflected far off the optical axis from being re-reflected on the incident surface and received by the image sensor, the angle between the incident surface and the exit surface is adjusted. 1. A prism for a video camera, characterized in that a light-receiving surface of an image sensor is subjected to a light-shielding treatment on the portion and the surrounding portion thereof. 2. The prism for a video camera according to claim 1, wherein the compound spectroscopic prism is used for a small video camera having a lens back focus of 25 mm or less.