JP2982169B2 - Mounting structure of color separation prism - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting structure for a color separation prism, and more particularly to a mounting structure for a color separation prism used in a television camera or the like.

[Conventional technology]

As is well known, a color television camera uses a color separation prism to convert the subject light from a photographing lens into an R (red) component,
(Green) component and B (Blue) component are decomposed, and these are taken out of an electric signal of each color component by a solid-state image pickup device such as a CCD or an image pickup tube and processed by an image signal processing circuit, and then displayed on a television screen. The subject's image.

Such a color separation prism is fixed in a housing, the front end of the housing is connected to a photographing lens, and at each end of the housing, a CCD, an imaging end is provided at each of the R, G, and B emission ends of the color separation prism. An imaging means such as a tube is attached.

The most important characteristic of such a color imaging device is a registration characteristic. The registration characteristics are based on the green channel (Gch), and convert the amount of image deviation from the red channel (Rch) and the amount of image deviation from the blue channel (Bch) into a TV book (TV book). It is expressed as. Such misregistration is considered to occur due to thermal expansion and contraction of the housing due to a change in environmental temperature, thermal expansion and contraction of the prism.

Of these, deformation due to thermal expansion distortion of the prism can be reduced by selecting a bonding agent for the prism or by bringing the thermal properties of the member directly bonded to the prism closer to the prism material.

When the color separation prism is mounted on the housing, the color separation prism is screwed to the housing at one or two fixed points.

[Problems to be solved by the invention]

However, since the housing is formed asymmetrically, when the ambient temperature changes, the housing thermally expands or contracts, and the optical axes of R, G, and B may be shifted irregularly. If the deviation of the optical axes of R, G, and B occurs irregularly, the above-described deviation of the registration occurs.

Conventionally, when such a misregistration occurs, it cannot be adjusted at all in the case of a CCD. In addition, in the case of an image pickup tube, it is possible to electrically correct the registration deviation, but there is a problem that a correction circuit for this is separately required.

The present invention has been made in view of such circumstances, and provides a mounting structure for a color separation prism that can maintain a constant registration even when a housing is thermally expanded or contracted due to a change in environmental temperature. With the goal.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a base plate having a color separation prism that separates subject light from a photographing lens into light of each wavelength component of R (red), G (green), and B (blue). In the mounting structure of the color separation prism that is mounted on the housing through
R in a direction orthogonal to each emission end face of the color separation prism,
Out of a plurality of intersections of perpendicular lines having the same length and lowered from the optical axes of the light of the wavelength components of G and B, among the intersections O1 located on the same side with respect to the emission direction of the optical axes, the housing The base plate is fixed to the housing at an intersection O of the perpendicular extending toward the housing with the housing or at a point where the intersection O is dynamically the center.

[Action]

According to the present invention, the point at which the color separation prism (16) is fixed to the housing (12) is defined by the optical axes (52, 54, 54) of B, G, and R.
Of the intersections of perpendicular lines (58, 60, 62) of the same length lowered from 56), the point is set based on the point (O1) located on the same side. This allows the optical axes (52, 54, 56) to move by the same amount in the same direction even when the housing (12) thermally expands or contracts. Will be minimal.

〔Example〕

Hereinafter, preferred embodiments of a mounting structure for a color separation prism according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a plan sectional view showing a color separation optical system to which the present invention is applied, and FIG. 2 is a sectional view taken along line II-II in FIG. As shown in the figure, the housing of the color separation optical system 10
12, a photographing lens 14 is disposed in front of the housing 12,
A color separation prism 16, which will be described later, is disposed in the inside. Further, an image pickup tube (blue) 24 and an image pickup tube (green) 26 , An image pickup tube (red) 28 is attached via brackets 30, 32, 34, respectively. The housing 12 is made of, for example, Al
The image pickup tubes 24, 26, and 28 are formed asymmetrically in relation to the mounting of the image pickup tubes 24, 26, and 28 at the respective output ends of the color separation prism 12.

The color separation prism 16 is mounted on the housing as shown in FIG.
12 is fixed to one inner surface 12A. That is, the base plate 36 is adhered to the upper surface of the glass color separation prism 16 in FIG.
A screw 40 is screwed into the boss 38 of the base plate 36 from the upper surface of the housing 12, and the color separation prism 16 is fixed in the housing 12. The screwing position of the screw 40 will be described later. The base plate 36 is made of a material having the same thermal expansion coefficient as the color separation prism, for example, ceramic.

FIG. 3 shows the structure of a known color separation prism 16. The color separation prism 16 has first, second, and third prisms 42, 46, and 44 for separating the subject light from the photographing lens 14 into B, R, and G components. First prism 42 and second prism
And the second prism 46 and the third prism 44 are joined at their respective contact surfaces.

With such a configuration, the color separation prism 16 separates the B, G, and R components of the subject light 50 in the directions of the optical axes 52, 54, and 56.

The B component and the G component of the subject light 50 thus decomposed,
The R component is converted into an electric signal by the image pickup tubes 24, 26, and 28, respectively, and processed by an image signal processing circuit (not shown). Then, the image of the subject is displayed on a television screen.

FIG. 4 is a schematic view showing a mounting position of the screw 40 shown in FIG. As shown in FIG. 4, the point O, which is the mounting position of the screw 40 for fixing the color separation prism 16 to the housing 12, is a perpendicular line 58 of the same length lowered from each of the optical axes 52, 54, 56 of B, G, R. , 60, 62, on the same side, that is, the optical axes 52, 5
Intersection O1 located on the right side in the light traveling direction of 4, 56
, The vertical line A (see FIG. 2) extending toward the housing 12 is set at the intersection with the housing 12. Optical axis 5
There are four intersections of perpendicular lines 58, 60, and 62 of equal length that are lowered from 2, 54 and 56, but the intersections located on the same side in the light traveling direction of the optical axes 52, 54 and 56 are the intersections There is only one point O1, and the intersection O of the perpendicular A extending from the intersection O1 toward the housing 16 with the housing 16 is the fixed point of the prism 16.

The operation of the structure for mounting the color separation prism according to the present invention having the above-described structure is as follows.

Since the color separation prism 16 is fixed to the housing 12 at the point O described above, when the housing 12 thermally expands or contracts, its optical axes 52, 54, and 56 are the same around the point O in the same direction. It moves by a certain amount. Therefore, although the optical axes of R, G, and B are shifted from those before thermal expansion or thermal contraction, the shift amount of the optical axes 52 and 54 with respect to the optical axis 54 of the G component is a reference value, that is, the housing 12 is thermally expanded. Alternatively, since the relative amount does not change compared to the state before contraction, the registration can be kept constant.

Here, the prism size is 2/3 inch size and A
Using the housing of l, the above-mentioned reference value is a value at the time of setting at an ambient temperature of 20 ° C. When this temperature is lowered to −20 ° C., the optical axes 52, 54, and 56 of R, G, B become FIG. From the position of the reference value indicated by the solid line, it was found that the position was moved by 8.2 μ in the directions of arrows A ₁ , A ₂ , and A ₃ , respectively, whereby the registration did not change.

In the above embodiment, the color separation prism 16 is fixed to the housing 12 at one point O using a screw 40.
It is not limited to this. That is, FIG. 5 (A),
The screws 40, 40 may be fixed on both sides of the point O at the same distance as shown in FIG. 5B, or the screws 40, 4 as shown in FIG. 5C.
0 and 40 may be arranged at the vertices of an equilateral triangle so that point O is located at the center of gravity of the equilateral triangle. Further, as shown in FIG. 5 (D), the screws 40 may be arranged at the vertices of a square, and the point O may be arranged at the intersection of the diagonal lines. In other words, if the point O is a mechanical center point, the same operation and effect can be obtained as in the case of fixing at the point O during thermal expansion or thermal contraction. Not done.

In the above embodiment, the housing was formed of Al, but Mg,
It may be formed of a metal such as SUS or Ti. Although the base plate 36 is formed of ceramic, it may be formed of a material such as Ti or glass having a coefficient of thermal expansion close to that of the prism. Further, the base plate 36 is not limited to a single plate, and may be formed by stacking on a connecting plate.

In the above embodiment, the imaging tube is used as the imaging unit.
A solid-state imaging device such as a CCD may be used.

〔The invention's effect〕

As described above, according to the mounting structure of the color separation prism according to the present invention, the point at which the color separation prism is fixed to the housing is defined by the intersection of the perpendicular lines of equal lengths lowered from the R, G, and B optical axes. Of these, since the intersection O1 located on the same side is set as a reference, the deviation of registration can be kept to a minimum.

[Brief description of the drawings]

FIG. 1 is a plan sectional view showing an embodiment of a separation optical system to which a mounting structure for a color separation prism according to the present invention is applied, FIG. 2 is a sectional view taken along line II-II in FIG. FIG. 4 is a plan view of the color separation prism, FIG. 4 is an explanatory view showing a mounting position of the color separation prism according to the present invention, and FIG. 5 is an explanatory view showing an application example of a mounting position of the color separation prism according to the present invention. is there. 10: color separation optical system, 12: housing, 14: photographing lens, 16: color separation prism, 24, 26, 28 ... imaging tube,
52, 54, 56 ... optical axis, 58, 60, 62 ... perpendicular.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 9/09-9/097

Claims (1)

(57) [Claims] An object light from a photographing lens is R (red), G
In a mounting structure of a color separation prism in which a color separation prism for separating light of each wavelength band component of (green) and B (blue) is mounted on a housing through a base plate, R in the direction of
Out of a plurality of intersections of perpendicular lines having the same length and lowered from the optical axes of the light of the wavelength components of G and B, among the intersections O1 located on the same side with respect to the emission direction of the optical axes, the housing A mounting structure for a color separation prism, wherein the base plate is fixed to the housing at an intersection O of a perpendicular line extending toward the housing or at a point where the intersection O is mechanically the center.