JPH0418308Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to a test pattern projection device used to adjust the performance of an optical device or the operation of an imaging device such as a television camera. When a light amount control section, a so-called grayscale section, consisting of a plurality of minute opaque or semi-transparent sections such as dots is provided, the influence of moiré caused by the halftone dots can be reduced, and a good test pattern image can always be obtained. The present invention relates to a test pattern projection device suitable for use in television cameras and the like.

(Prior Art) Conventionally, in order to obtain a good image, television imaging devices have made various adjustments such as registration adjustment, color temperature adjustment, and gamma adjustment to match each color image of R, G, and B before shooting. I'm going.

In order to simplify the adjustment work at this time, many television cameras currently have a switchable test pattern projection device built into the camera or the taking lens.

The test pattern projection device projects the test pattern onto a predetermined surface such as an imaging surface. Adjustment work for the television camera is performed by using the test pattern image obtained at this time.

Test patterns for television cameras are relatively high-frequency charts consisting of linear or wedge-shaped gratings for focus adjustment, resolution checks, linearity adjustment (correction of geometric distortion due to deflection), and registration adjustment. It consists of a comparatively low frequency chart in the form of a straight line, wedge, or V-shape, and a grayscale chart in which the amount of transmitted light is changed in stages for gamma adjustment.

In order to obtain a predetermined transmittance with high accuracy, the gray scale is made up of a plurality of micro-sized non-transparent or semi-transparent parts, such as halftone dots, in which the amount of transmitted light is controlled in terms of area. That is, a desired transmittance is obtained by changing the number or size of halftone dots.

However, when the gray scale is composed of halftone dots, if the pitch of the halftone dots on the imaging surface is rougher than the scanning line pitch, the halftone dots will be imaged, and the gray area will not have uniform brightness. The structure of halftone dots appears, and it cannot be used as a gray scale.

On the other hand, if the halftone dot pitch is made very fine, the structure of the halftone dots will not be imaged, but diffraction light will occur due to the halftone dots, causing the problem that the test pattern image will be colored.

If you make the halftone dot pitch and scanning line pitch almost the same,
Although the structure of halftone dots does not appear and the influence of diffraction can be reduced, it has the drawback of causing moiré fringes.

(Problem to be solved by the invention) This invention solves the problem of moiré fringes that occur from the halftone dots when the test pattern has a gray scale part such as halftone dots that controls the amount of transmitted light in terms of area. It is an object of the present invention to provide a test pattern projection device that can always project a good test pattern image onto a predetermined surface.

(Means for Solving the Problem) In a test pattern projection device that projects a test pattern onto a predetermined surface using a projection lens, the test pattern includes a halftone dot pattern portion in which halftone dots are arranged on one plane, and a halftone dot pattern portion in which halftone dots are arranged on one plane. It has a linear pattern section in which charts in a straight line or a grid pattern are arranged on a plane different from the section.

Other features of the invention are described in the Examples.

(Embodiment) FIG. 1 is a schematic diagram of an optical system of an embodiment in which the present invention is applied to a part of a television camera.

In the figure, 1 is a light source such as a tungsten lamp, 2 is a condenser lens for condensing the light beam from the light source 1, 10 is a test pattern, 3, 4
are a halftone dot pattern portion and a straight line pattern portion which constitute the test pattern 10, and are arranged on different planes.

As shown in FIG. 2, the halftone dot pattern section 3 is a grayscale section 26 in which halftone dots of different sizes and numbers are arranged in regions 21 to 25 on one plane of the transparent plate 20.
have.

This halftone dot pattern section 3 is used for gamma adjustment of a television camera.

As shown in FIG.
It has charts such as

The linear pattern section 4 is used for focus adjustment, linearity adjustment, etc.

5 is a projection lens, and 6 is an image sensor.

In this embodiment, the light beam emitted from the light source 1 is condensed by a condenser lens to uniformly illuminate the halftone dot pattern section 3 and the linear pattern section 4 of the test pattern 10.

Then, each pattern portion of the test pattern 10 is superimposed and imaged on the surface of the image sensor 6 by the projection lens 5.

Generally, in a television camera, a high frequency component is required for the straight line pattern section 4 used for focus adjustment, linearity adjustment, etc., and a high frequency component is not required for the halftone pattern section 3 used for gamma adjustment etc., and some blurring can be tolerated.

Therefore, in this embodiment, adjustment is made so that the straight line pattern section 4 is well focused on the surface of the image sensor 6, and the halftone pattern section 3 placed behind or in front of the straight line pattern section 4 is brought into focus on the image sensor 6 in an out-of-focus state. The image is formed on a surface.

At this time, each element is set so that the halftone dots of the halftone dot pattern section 3 are out of focus to the extent that they cannot be resolved. This is because the size of the halftone dots is formed in advance to be approximately the same pitch as the scanning line, so in this degree of out-of-focus state, the boundary of the gray scale section 26 of the halftone dot pattern section 3 will line up with the scanning line. This is because the blurring is only about the size of one line, and there is no practical problem.

As a result, the halftone dots on the surface of the image sensor 6 are blurred to provide uniform brightness, and the occurrence of moiré fringes due to interference with the scanning line is effectively prevented.

In this embodiment, the halftone pattern section 3 and the straight line pattern section 4 of the test pattern 10 are each formed from separate members, but the halftone pattern section and the straight line pattern section are formed on the front and back surfaces of a single member, respectively. You may do so.
Then, when the thickness of the member is appropriately set and the linear pattern portion is focused on the image sensor surface, the halftone dots of the halftone dot pattern portion may be brought out of focus as described above.

Also, in order to eliminate the blurring of the boundary of the grayscale part of the halftone dot pattern part, for example, if a black frame is placed at a position corresponding to the boundary of the grayscale part of the halftone dot pattern part of the straight line pattern part, the boundary of the grayscale part The blur can be covered with the black frame.

(Effect of the invention) According to the invention, the halftone dot pattern portion and the linear pattern portion of the test pattern are formed on different planes, and when these pattern portions are projected onto the image sensor surface, the halftone dot pattern portion and the straight line pattern portion are formed on different planes. By setting each element so that the image is blurred by a predetermined amount on the image sensor surface, moiré fringes due to interference between halftone dots and scanning lines are prevented from occurring.
It is possible to achieve a test pattern projection device that can provide a good projection pattern without false signals and also without color shifts due to wavelength differences in transmittance caused by diffraction of halftone dots.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention.
FIG. 2 and FIG. 3 are explanatory diagrams of a part of the test pattern according to the present invention, respectively. In the figure, 1 is a light source, 2 is a condenser lens, and 10
3 is a test pattern, 3 is a halftone pattern part, 4 is a straight line pattern part, 5 is a projection lens, 6 is an image sensor,
26 is a gray scale part.

Claims (1)

[Scope of utility model registration request] In a test pattern projection device that projects a test pattern onto a predetermined surface using a projection lens, the test pattern includes a halftone dot pattern section in which halftone dots are arranged on one plane, and a halftone dot pattern section arranged on a different plane from the halftone dot pattern section. 1. A test pattern projection device comprising a linear pattern section in which linear or grid-like charts are arranged.