JPH10257510A - Dust proof cover used in common for mask of video camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To integrate a mask for shutting off undesired light made incident onto a color resolving optical system with a cover for dust proof of an optical filter and to prevent a ghost and a flair from generating due to scattered light at an edge of an opening that controls an optical pass area. SOLUTION: An opening 42 to control a passing range of light entering to a color resolving prism 20 is formed to a dust proof cover 40 that surrounds a back side of a neutral density(ND) filter 24 and a color temperature conversion filter 26. A slope is formed so that an inner peripheral face 43 of the opening 42 spreads an aperture area in a thickness direction of the dust cover 40 from an entering face side of the light toward an emission face side. Thus, the undesired light reflected on the inner peripheral face 43 is largely deviated from an incident optical axis of the color resolving prism 20 to prevent a ghost and a flair. Furthermore, an aluminum material is adopted for a material of the dust proof cover 40 and the reflection is more effectively prevented by applying black alumite processing to the entire parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust cover for a video camera, and more particularly to a mask and an optical filter which are disposed in front of a color separation optical system fixed in a camera body and which block unnecessary light. The present invention relates to a dust cover for a video camera in which a cover for dust prevention is integrated.

[0002]

2. Description of the Related Art A three-panel (tube) type broadcast camera has a color separation prism for guiding color light components corresponding to RGB image pickup element plates (tubes), respectively.
After passing through optical filters such as a cut filter, a color temperature conversion filter, and an ND filter, the light enters the color separation prism.

Since the color separation prism has a large number of reflection surfaces, light (unnecessary light) incident from a direction other than the normal incident light path of the prism reflects off the normal reflection light path and reaches the imaging surface. , Ghost and flare easily occur. In order to block such unnecessary light, a mask for removing unnecessary light is conventionally provided in front of the color separation prism. Since scattered light is also generated by the opening edge of the mask, this mask is formed to have a thickness of, for example, about 50 μm, and is adhered to an opening of a dustproof cover provided behind the optical filter.

[0004]

However, the conventional mask must be formed extremely thin as described above. For example, after photo-etching a stainless material,
There is a problem that the manufacturing process is complicated such as black plating, and a process of bonding to the dustproof cover is required, and the operation is complicated.

The present invention has been made in view of such circumstances, and has a simple structure, which can effectively prevent ghost and flare from occurring and prevent dust from adhering to an optical filter. The purpose is to provide a cover.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an optical filter disposed behind a taking lens and a spectral characteristic corresponding to each of RGB image pickup means. And a color separation optical system that divides the color filter into three color components, and a dust cover surrounding the rear of the optical filter, wherein the dust cover is formed of an opaque material in a plate shape. An opening that regulates a range of light that enters the color separation optical system out of the light that has passed through the optical filter, and an inner peripheral surface of the opening has a light intensity in a thickness direction of the dustproof cover. The opening area on the exit surface side is formed larger than the opening area on the entrance surface side.

According to the present invention, the mask for regulating the range of light incident on the color separation optical system is integrated with the dust-proof cover of the optical filter, and the opening for regulating the light passage area is located on the light entrance side. Since the opening area on the emission side is made larger than the opening area of the aperture, unnecessary light reflected on the inner peripheral surface of the opening largely deviates from the incident optical axis of the color separation optical system. Thereby, ghost and flare due to light scattered at the edge of the opening can be prevented. Further, the manufacturing process is simplified as compared with the conventional mask member, and the cost can be reduced.

In addition, scattering of unnecessary light due to the surface of the dustproof cover is reduced by adopting an aluminum material as a material of the cover and subjecting the whole to black anodizing.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of a dust cover according to the present invention. FIG. 1 is a side sectional view of a front end portion of a broadcast camera to which a mask / dustproof cover of a video camera according to the present invention is applied, FIG. 2 is a front view, and FIG. 3 is a top view including a partial cross section. 2 and 3, the camera housing is omitted.

[0010] As shown in FIG.
A lens barrel receiving seat 14 and a mount ring 16 are provided at the distal end of the lens barrel. The mount ring 16 is screwed to the outer periphery of the lens barrel receiving seat 14. After the rear end of the photographic lens barrel (not shown) is fitted into the lens barrel receiving seat 14, the mount ring 16 is By turning it six times, the taking lens is detachably attached to the camera body.

At the rear end of the lens barrel receiver 14, an infrared cut (IR) filter 18 (or a low-pass filter) also serving as a dust proof is held, and behind the lens barrel receiver 14, A prism housing 22 having a column member 46 (see FIG. 3) for supporting the color separation prism 20 is disposed in close contact with the lens barrel receiving seat 14.

Inside the prism housing 22, a filter holding frame 28 holding a light quantity correction (ND) filter 24 and a color temperature conversion (CC) filter 26 is provided with a pin 3.
It is provided so as to be freely rotatable through the “0”. A gear 32 is formed on the center shaft of the filter holding member 28.
2 is a filter switching knob 36 via a connecting gear 34.
The gear 38 is connected to a gear 38 fixed to the shaft.

When the filter switching knob 36 is rotated, a gear 38 fixed to the shaft end of the knob rotates, and the rotating force is transmitted to the filter holding member 28 via the connecting gear 34, and the filter holding member 28 is rotated. Is pin 3
Rotate around 0. By this rotation, the optical filter disposed in front of the color separation prism 20 can be changed.

ND filter 24 and CC filter 2
The rear side of the filter holding member 28 holding the filter 6 is surrounded by a dustproof cover 40 (a dustproof cover also serving as a mask).
This prevents dust from adhering to the optical filter such as the filter 24. Although the configuration of the dust cover 40 will be described in detail later, the dust cover 40 has an opening 42 that regulates the range of light entering the color separation prism 20.

The color separation prism 20 is disposed behind the dustproof cover 40 via a rubber frame (or sponge frame) 44. Since the rubber frame 44 is disposed in close contact between the dust-proof cover 40 and the incident surface of the color separation prism 20, dust is prevented from entering the incident surface of the color separation prism 20. The prism housing 22 is integrally formed with a support member 46 for supporting the color separation prism 20 from the side. On the other hand, a prism base plate 48 made of a ceramic material is adhered to the side surface of the color separation prism 20, and the prism base plate 48 and the support members 46 are fixed by screws 49, 49. The color separation prism 20 is fixed to the prism housing 22.

The color separation prism 20 is composed of three prisms, that is, first, second and third prisms from the light incident side. The light exit surface of the first prism 51 has a blue color (B
A dichroic coat that reflects only the (LUE) component is applied, and a red (RE)
D) A dichroic coat reflecting only the component is applied.

Of the light beam incident on the color separation prism 20, the BLUE component is reflected on the light beam exit surface of the first prism 51, and the reflected light of this BLUE component is emitted from the BLUE channel exit surface of the first prism 51 and is passed through a blue trimming filter. After the color components other than the BLUE component have been removed through the light source 55, an image is formed on a CCD (not shown). BLU
The remaining light flux other than the E component passes through the first prism 51 and enters the second prism 52, and only the RED component is reflected by the dichroic coat on the light flux emission surface of the second prism 52. The RED reflected light is transmitted to the second prism 52
Is totally reflected by the incident surface of the second prism 52 and exits from the exit surface of the RED channel of the second prism 52, and the red trimming filter 56
, And color components other than the RED component are removed, and then an image is formed on a CCD (not shown).

The remaining green (GREEN) component is emitted from the emission surface of the GREEN channel of the third prism 53,
After passing through the green trimming filter 57 and removing color components other than the GREEN component, an image is formed on a CCD (not shown). FIG. 4 is a rear view of the dust cover 40, and FIG. 5 is a cross-sectional view taken along line AA 'in FIG. Dust cover 40
Is formed of an aluminum plate having a plate thickness d = 0.6 mm, and an opening 42 for restricting a range of light entering the color separation prism is formed at a position below the center. Although the shape of the opening 42 is not particularly limited, in the present embodiment, the opening 42 is formed in a long hole shape in which the top and bottom of a circle are linearly cut.

On the left side of the opening 42, a notch 45 is formed to avoid a support member 46 for supporting the color separation prism 20 disposed behind the opening 42. The thickness d of the dust cover 40 is not particularly limited, but is preferably about 0.5 mm to 1 mm. FIG. 6 is an enlarged view of the vicinity of the opening 42. As shown in the figure, the inner peripheral surface 43 of the opening 42 is inclined with respect to the thickness direction of the dust cover 40 so that the opening area increases from the light entrance surface to the light exit surface. A surface is formed. That is, the opening 42 is provided in the dustproof cover 40.
The opening area on the exit surface side is larger than the opening area on the light entrance surface side with respect to the thickness direction.

Further, by using an aluminum material as the material of the dust-proof cover 40 and subjecting the whole to black alumite treatment, it is possible to prevent the scattering of light blocked by the dust-proof cover 40 and to prevent the edge of the opening 42, that is, the inner periphery. Light scattering by the inclined surface 43 can be prevented. Next, the operation of the dust cover that also serves as a mask of the video camera configured as described above will be described.

Light incident through the photographing lens mounted on the lens barrel receiving seat 14 is reflected by the IR filter 18 and the C
The light passes through the C filter 26 and travels to the color separation prism 20. The aperture 42 formed in the dust cover 40 regulates the area through which the light beam entering the color separation prism 20 passes. That is, light entering from an optical path greatly deviated from the optical axis of the taking lens is blocked by the dustproof cover 40,
The light does not enter the color separation prism 20. Since the dust-proof cover 40 is treated with black alumite, reflection on the surface is prevented, and return of unnecessary light blocked by the dust-proof cover 40 is also suppressed.

The light passing through the opening 42 of the dustproof cover 40 may be scattered at the edge (inner peripheral surface) of the opening 42, but the inner peripheral surface 43 of the opening 42 is directed toward the emission direction. Since the inclined surface is widened, light incident on the inner peripheral surface of the opening 42 from outside the regular optical path is reflected by the inner peripheral surface 43 and largely deviates from the incident optical axis of the color separation prism 20. Therefore, the possibility that such unnecessary light is imaged on the imaging surface by an optical path other than the normal optical path by the color separation prism 20 is extremely low, and ghost and flare can be reduced.

In the above embodiment, the inner peripheral surface 43 of the opening 42 is inclined such that the opening area increases from the light entrance surface to the light exit surface with respect to the thickness direction of the dustproof cover 40. Is described as an example, but the invention is not limited thereto, and the step 63 may be formed so that the opening area increases from the light entrance surface side to the light exit surface side as shown in FIG. This configuration also has an advantage that the incidence of scattered light due to the edge of the opening 42 can be prevented. The step may be provided in a plurality of steps, or the step and the inclined surface may be combined.

[0024]

As described above, according to the dust cover for a video camera according to the present invention, the mask for regulating the range of light incident on the color separation optical system is integrated with the dust cover for the optical filter. At the same time, since the opening for regulating the light passage area is formed so that the opening area on the emission side is larger than the opening area on the entrance side of light, unnecessary light reflected on the inner peripheral surface of the opening is colored. The ghost and the flare can be prevented from being largely deviated from the incident optical axis of the decomposition optical system. Further, the mask / dustproof cover having such a configuration can simplify the manufacturing process and reduce the cost as compared with the conventional mask member.

In particular, the use of an aluminum plate as the material of the mask and dust cover and the use of black alumite treatment on the entire mask and dust cover can reduce the scattering of unnecessary light due to the surface of the mask and dust cover.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a distal end portion of a broadcast camera to which a mask / dustproof cover of a video camera according to the present invention is applied.

FIG. 2 is a front view of a tip of the broadcast camera shown in FIG. 1;

FIG. 3 is a top view including a partial cross section of a distal end portion of the broadcast camera shown in FIG. 1;

FIG. 4 is a rear view of the cover.

FIG. 5 is a sectional view taken along line AA in FIG. 4;

FIG. 6 is an enlarged view of a main part of FIG. 5;

FIG. 7 is an enlarged view of a main part showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 ... Camera housing 14 ... Lens barrel receiving seat 16 ... Mount ring 18 ... IR filter 20 ... Color separation prism 22 ... Prism housing 24 ... ND filter 26 ... Color temperature conversion filter 40 ... Dustproof cover (mask and dustproof cover) 42 ... Opening 43: Inner peripheral surface

Claims (5)

[Claims] 1. An optical filter disposed behind a photographic lens, and a color separation optical system that divides light passing through the optical filter into three color components having spectral characteristics corresponding to each of RGB image pickup units. Used in a video camera provided with a dustproof cover surrounding the rear of the optical filter, wherein the dustproof cover is formed in a plate shape with an opaque material, and the color separation optical system of light passing through the optical filter. Having an opening that regulates the range of light entering the
A video camera, wherein an inner peripheral surface of the opening is formed so that an opening area on an emission surface side is larger than an opening area on a light entrance surface side in a thickness direction of the dustproof cover. Dustproof cover for mask. 2. An inclined surface is formed on an inner peripheral surface of the opening so that an opening area is increased from a light entrance surface to a light exit surface with respect to a thickness direction of the dust cover. 2. The dust cover according to claim 1, further comprising a mask. 3. A step is formed on an inner peripheral surface of the opening such that an opening area increases from a light entrance surface side to a light exit surface side in a thickness direction of the dustproof cover. 1
Dustproof cover for video camera. 4. The dust cover according to claim 1, wherein the optical filter comprises at least one of an ND filter and a color temperature conversion filter. 5. The mask and dustproof cover for a video camera according to claim 1, wherein the dust and dust cover for a video camera is formed of an aluminum material and is entirely black anodized.