JPH05341111A - Color separation prism device - Google Patents

Abstract

PURPOSE:To make the color reproductions of a natural light and the reflected Tight equal to each other without raising cost by arranging a 45 deg.-oblique double refracting plate in front of the incident surface of a prism device for separating the color of an incident light. CONSTITUTION:An input image is resolved into each color of RGB by a three- color resolving gap-less prism 1, and solid image pickup elements 2a-2c for each color of Rch (red channel), Gch (green channel), and Bch (blue channel) are mounted in the rear of each color, respectively. The incident surface of the prism 1 has a 45 deg.-oblique double refracting plate 3, a horizontal double refracting plate 4, and an IR cut filter 5. When the incident light is a linear polarized component, the beam of the incident linear polarized light is double- refracted in 45 deg. direction by the 45 deg.-oblique double refracting plate 3, and separated into P-wave and S-wave. To improve resolution, the solid image pickup elements 2a, 2b of Rch and Gch are horizontally shifted by P/2 (P is a horizontal image pitch). When the separated width (d) is small, the integrated color is the same as a circular polarized light, and the color reproductions of natural light and the reflected light can be made equal to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color separation prism device used in a three-plate type video camera or the like.

[0002]

2. Description of the Related Art FIG. 3 shows a structural example of a color separation prism device used in a conventional three-plate video camera. In the figure, the prism 11 is a three-color separation type gapless prism, which separates an input image into RGB color components. Behind RGB of the prism 11, solid-state image pickup devices 12a, 12b, 12c are provided, respectively. Now, the white light that has entered the prism 11 is divided into Gch (green channel), Bch (blue channel), and Rch (red channel). Therefore, the solid-state image pickup devices 12a to 12c are arranged at the respective positions. Again prism 1
1 has a vertical birefringent plate 13, a horizontal birefringent plate 14, I
The R cut filter 15 and the λ / 4 phase plate 16 are arranged as illustrated. Since the dichroic film of the prism has different spectral characteristics between S-polarized light and P-polarized light, the λ / 4 phase plate 16 is placed in front of the incident surface of the prism 11, and
As shown in FIG. 3B, incident linearly polarized light is shown in FIG.
This is because the circularly polarized light is changed to the circularly polarized light and the light is incident on the prism 11. Therefore, the light rays incident on the prism 11 include P-polarized waves and S-polarized waves evenly. 3 (b),
FIG. 3C shows the polarization of light rays at points b and c in FIG.

FIG. 4 shows an example of spectral characteristics of a conventional prism device. In this figure, since the light rays incident on the dichroic film of the prism 11 include P waves and S waves evenly,
Both natural light and reflected light can reproduce the same color.

[0004]

However, in such a conventional color separation prism device, it is necessary to add a new crystal filter as a λ / 4 phase plate, which is disadvantageous in that the cost becomes high.

The present invention has been made in order to solve the above-mentioned conventional problems, and a color separation prism device which can make the color reproduction of reflected light the same as the natural need without increasing the price. The purpose is to provide.

[0006]

The invention according to claim 1 of the present application is a color separation prism device for color-separating incident light.
It is characterized in that a 45 ° oblique birefringent plate is arranged in front of the entrance surface of the prism device.

The invention of claim 2 of the present application is characterized in that the prism device is a gapless prism.

According to a third aspect of the present invention, red (R channel), green (G channel) and blue (B channel) solid-state image pickup devices are arranged on the exit surface of the prism device, respectively.
P / 2 channel and R channel solid-state image sensor
(P: horizontal pixel pitch), the 45 ° oblique birefringent plate is separated from the horizontal pixel pitch P by the following expression d = √2 × P / 4. It is characterized by being arranged as follows.

[0009]

According to the present invention having such a feature, the light rays incident on the prism are separated into the P wave and the S wave by the 45 ° oblique birefringent plate arranged on the prism entrance surface. However, if the separation width is small, the integrated light becomes the same as circularly polarized light, and the color reproduction of natural light and reflected light can be made the same.

[0010]

1 is a view showing a color separation prism device according to an embodiment of the present invention. In the figure, reference numeral 1 is a gapless prism for separating three colors, which separates an input image into RGB colors. Behind the respective colors to be separated, solid-state image pickup devices 2a to 2c for Rch, Gch, and Bch are mounted respectively in the same manner as in the conventional example. In this embodiment, a 45 ° oblique birefringent plate 3, a horizontal birefringent plate 4 and an IR cut filter 5 are provided on the entrance surface of the prism 1.

Assuming that the incident light is a linearly polarized light component as shown in FIG. 1B, the 45 ° oblique birefringent plate 3 birefringes the incident linearly polarized light beam in the 45 ° direction. Then, upon birefringence, as shown in FIG. 1C, it is separated into P wave and S wave.
Therefore, the incident light is separated into S wave and P wave and is incident on the prism 1. 1B and 1C are diagrams showing polarization components at points b and c.

FIG. 2 shows the spectral characteristics of this embodiment.
In this embodiment, the light beam incident on the dichroic film of the prism 1 is separated into S wave and P wave. In this embodiment, since the gapless prism 1 is used, the separation width is larger than that of a prism having a gap.
As indicated by the broken line, the waves have different spectral characteristics. However, when the separation width shown in FIG. 1C is d and the horizontal pixel pitch of the solid-state image sensor is P, the arrangement is such that d = √2 × P / 4. Here, in the three-plate prism device, the R-channel and G-channel solid-state image pickup devices are arranged so as to be horizontally offset by P / 2 in order to improve resolution. Therefore, if the separation width is small, the integrated color is the same as circularly polarized light. Therefore, the color reproduction of natural light and reflected light can be made the same.

[0013]

As described in detail above, according to the present invention, the functions of both the λ / 4 phase plate and the vertical birefringent plate can be achieved with only one 45 ° oblique birefringent plate. Therefore, the effect of reducing the price can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a color separation prism device according to an embodiment of the present invention.

FIG. 2 is a diagram showing spectral characteristics of the present embodiment.

FIG. 3 is a configuration diagram of a conventional color separation prism device.

FIG. 4 is a spectral characteristic diagram of a conventional color separation prism device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Prism 2a-2c Solid-state image sensor 3 45-degree diagonal birefringent plate 4 Horizontal birefringent plate 5 IR cut filter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yutaka Takahashi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A color-separating prism device for color-separating incident light, wherein a 45 ° oblique birefringent plate is arranged in front of an incident surface of the prism device. 2. The color separation prism device according to claim 1, wherein the prism device is a gapless prism. 3. The red (R channel), green (G channel), and blue (B channel) solid-state image pickup devices are arranged on the exit surface of the prism device, and the G-channel and R-channel solid-state image pickup devices are arranged in the P-type. / 2 (P: horizontal pixel pitch)
The 45 ° oblique birefringent plate is arranged so that the following equation d = √2 × P / 4 holds with the horizontal pixel pitch P when the separation width is d. The color separation prism device according to claim 2.