JPH05232304A - Color separation prism device - Google Patents

Abstract

(57) [Abstract] [Purpose] A color that can ensure high zoom tracking performance with high image quality and no intermediate blur during zooming in a two-plate, three-plate camera using an inner focus type zoom lens. A decomposing prism device is provided. [Structure] Processing size variation of prism 6a, imaging surface 7
The absolute value of the optical path length is adjusted to correct the flange back change due to the position variation of a, the thickness variation of the sealing glass 7b, the thickness variation of the crystal optical filter 11, etc., and then the position of the imaging surface 7a of the prism 6a is used as a reference. By sliding the prisms 6b and 6c in the directions of the arrows to adjust the relative optical path lengths between the prisms 6a and the prisms 6b and 6c, the zoom tracking curve can be made to match the design value.

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 for an inner focus type zoom lens mounted on a video movie or the like.

[0002]

2. Description of the Related Art In recent years, with the spread of video movies, it has become common to use an inner focus type zoom lens capable of autofocusing from just before the lens to infinity. In addition, the demand for higher image quality is also increasing. A two-plate or three-plate camera using a color separation prism is generally used for high image quality, and a color separation prism device with high image quality and high zoom tracking performance is required for an inner focus type zoom lens. There is.

A conventional color separation prism device will be described below with reference to the drawings. FIG. 3 shows the configuration of a conventional color separation prism device. As shown in FIG. 3, the first group lens 21,
A second lens group 22, a third lens group 23, which is a variable power lens, and a fourth lens group 24, which is a focusing lens, are provided in a lens barrel 25, and are in contact with a color separation prism 26 at a prism mounting surface 25a. The color separation prism 26 includes a prism 26a for separating green light, a prism 26b for separating blue light, and a prism 26c for passing red light.
It is composed by. Prism 26a, prism 2
The solid-state image sensor 27, the solid-state image sensor 28, and the solid-state image sensor 29 are bonded to the exit surfaces of the prism 6b and the prism 26c, respectively, and 27a, 28a, and 29a are the image surfaces, 27b, and 27b.
28b and 29b are sealing glasses. Color separation prism 2
6 is fixed to the lens barrel 25 by a mounting member 30. Reference numeral 31 is a crystal optical filter that functions as a low-pass filter and an infrared light cut filter, and is fixed to the lens barrel 25.

The operation of the color separation prism device configured as described above will be described below with reference to FIGS. 3 and 4.

As shown in FIG. 3, the optical path length of the color separation prism 26 is adjusted by sliding the prisms 26b and 26c in the directions of the arrows with reference to the position of the image pickup surface 27a of the prism 26a. After the adjustment is completed, the mounting member 30 is adhesively fixed to the color separation prism 26 so that the incident surface of the color separation prism 26 and the prism mounting surface 25a of the lens barrel 25 are positioned at a constant interval determined by optical design. ing.

FIG. 4 shows the second group lenses 22 and 4 during zooming.
8 is a zoom tracking curve showing the positional relationship of the group lens 24. During zooming, the fourth group lens 24 is the second group lens 2
Focusing state during zooming (zoom tracking performance) by moving according to the zoom tracking curve determined in advance by the position information of 2 and the subject distance
Keep

[0007]

However, in the above-described conventional configuration, the processing size variations of the prisms 26b and 26c, the positional variations of the imaging surfaces 28a and 29a, are caused by adjusting the optical path length relative to the prism 26a.
The thickness variations of the sealing glasses 28b and 29b are corrected to 3
It is possible to obtain high image quality and high resolution by the plate method,
Flange back changes due to variations in the processing dimensions of the prism 26a, variations in the position of the imaging surface 27a, and variations in the thickness of the sealing glass 27b are not corrected by the amount of the flange back, and are the reference for the second group lens 22 and the fourth group lens 24 when adjusting the focus of the zoom lens. Since the correction is performed by shifting the position, if the flange back becomes longer,
Shows a zoom tracking curve as shown by a dashed line and, when it becomes short, a broken line. Therefore, during zooming, there is a problem in that a large error occurs between the zoom tracking curve of the design value and the focus shift in the zoom intermediate range. In particular, in the two-plate and three-plate type cameras, since color separation prisms are used, there are many factors that cause variations in the flange back, and this is a major problem in cameras having high image quality and high resolution.

The present invention solves the above-mentioned problems of the prior art and uses an inner focus type zoom lens.
An object of the present invention is to provide a color separation prism device having a very high zoom tracking performance in a three-plate camera.

[0009]

In order to achieve this object, a color separation prism device of the present invention is a solid-state image pickup device fixed to the color separation prism and the exit surface of the color separation prism in an inner focus type zoom lens. It consists of an element and a mounting member for mounting the color separation prism on the zoom unit, and the mounting member changes the flange back due to variations in the processing dimensions of the color separation prism, variations in the imaging surface position of the solid-state image sensor, and variations in the thickness of the sealing glass. Quantity,
The color separation prism is fixed to the color separation prism in a state in which the absolute value of the flange back is adjusted by changing the distance between the incident surface of the color separation prism and the surface of the mounting member on which the zoom lens is mounted.

[0010]

With this configuration, the zoom tracking performance can be significantly improved in the two-plate, three-plate type camera using the inner focus type zoom lens.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a first lens group 1, a second lens group 2 which is a variable power lens, a third lens group 3 and a fourth lens group 4 which is a focusing lens are held in a lens barrel 5. .. 5a is a prism mounting surface. The color separation prism 6 is a prism 6 that separates green light.
a, a prism 6b for separating blue light, and a prism 6c for passing red light. Prism 6
The solid-state imaging devices 7, 8 and 9 are adhered to the exit surfaces of the a, the prism 6b and the prism 6c, respectively, and the imaging surfaces 7a, 8a and 9a are sealed with sealing glasses 7b, 8b and 9b. The color separation prism 6 has a mounting member 10
It is fixed to the lens barrel 25 by. The crystal optical filter 11 is fixed to the lens barrel 5 so as to function as a low pass filter and an infrared light cut filter.

The operation of the color separation prism device configured as described above will be described below with reference to FIGS. 1 and 4.

As shown in FIG. 1, in adjusting the optical path length of the color separation prism 6, first, the optical system is adjusted in advance so that the flange back becomes a design value. At this time, an optical system for absolute adjustment of the optical path length may be used in which the flange back is set to the design value. In that state, the prism 6a is moved in the direction of the arrow parallel to the optical axis to adjust the gap between the mounting member 10 and the incident surface of the color separation prism 6 to focus and fix the solid-state image sensor 7 of the green channel. By doing so, variations in the processing dimensions of the prism 6a, variations in the position of the image pickup surface 7a, and variations in the thickness of the sealing glass 7b are corrected, and the absolute value of the flange back is adjusted.

During the adjustment, in order to prevent one-sided blurring, the prism mounting surface 5a of the lens barrel 5 and the color separation prism 6 are arranged.
Attention should be paid to the parallelism of the incident surface of. Next, the prism 6a, the prism 6b, and the prism 6 are slid in the directions of the arrows with reference to the position of the imaging surface 7a of the prism 6a.
Relative optical path length adjustment between c is performed.

As described above, according to the present embodiment, the flange back is corrected by adjusting the absolute value of the flange back, thereby correcting the flange back change due to the variation of the processing size of the prism, the image pickup position of the solid-state image pickup element, the thickness variation of the sealing glass, and the like. By matching the actual flange back to the design value,
The zoom tracking curve can be made to match the design value, and extremely high zoom tracking performance that does not cause intermediate blur during zooming can be ensured.

As shown in FIG. 2, by fixing the crystal optical filter 11 of the above embodiment to the mounting member 10 in advance, the absolute value of the optical path length is adjusted even when the optical system for adjusting the absolute value of the optical path length is used. By adjusting the value, it is possible to correct the flange back change due to the thickness variation of the crystal optical filter 11.

[0018]

As is clear from the above description of the embodiments, in the inner focus type zoom lens,
It consists of a color separation prism, a solid-state image sensor fixed to the exit surface of the color separation prism, and a mounting member for mounting the color separation prism on the zoom lens unit. The absolute value of the flange back can be adjusted by changing the distance between the incident surface of the color separation prism and the mounting surface of the zoom lens of the mounting member to determine the amount of change in the flange back due to variations in the imaging surface position of the image sensor and the thickness of the sealing glass. By fixing to the color separation prism in the state of performing, extremely high zoom tracking performance can be realized in the two-plate, three-plate camera using the inner focus type zoom lens.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a color separation prism device according to another embodiment of the present invention.

FIG. 3 is a sectional view of a conventional color separation prism device.

FIG. 4 is a diagram showing a zoom tracking curve showing the positional relationship between the second lens group and the fourth lens group during zooming.

[Explanation of symbols]

 1 1st group lens 2 2nd group lens 3 3rd group lens 4 4th group lens 5 Lens barrel 6 Color separation prism 7 Solid-state image sensor 8 Solid-state image sensor 9 Solid-state image sensor 10 Mounting member 11 Quartz optical filter

Claims (2)

[Claims] 1. A color separation prism device for use in an inner focus type zoom lens, comprising a color separation prism, a solid-state image sensor fixed to an exit surface of the color separation prism, and the color separation prism. And a mounting member for mounting on the color separation prism, wherein the mounting member measures the variation of the flange back due to variations in the processing dimensions of the color separation prism, variations in the image pickup surface position of the solid-state image sensor, and variations in the thickness of the sealing glass. A color separation prism device which is fixed to a color separation prism in a state in which the absolute value of the flange back is adjusted by changing the distance between the incident surface and the zoom lens mounting surface of the mounting member. 2. The color separation prism device according to claim 1, wherein the crystal optical filter is fixed to the mounting member in advance, and then the absolute value of the flange back is adjusted.