JPH10206993A - Device for evaluating describing performance for camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily evaluate describing performance by a lens including resolving power without using a focusing screen for which accuracy is required by providing a solid-state image pickup element camera for picking up a chart image and a means receiving output from a solid-state image pickup element and deciding the describing performance on a chart by the lens. SOLUTION: A chart plate 4 consisting of chart plates 4a and 4b for evaluating the describing performance in a telephoto state and a wide-angle state is provided in front of the photographing lens 1a of the camera to be inspected 1 by leaving a specified distance in a state where it can freely move in the optical axis direction of the lens 1a of the camera 1. A CCD camera 10 receiving the image from an enlarging optical system 7 through a mirror 9 is attached to one end of an L-shaped hollow cylindrical holder 8. The CCD camera 10 is connected to an arithmetic device 12 functioning as the deciding means. By such constitution, the device 12 outputs a digital value as a value for evaluating the describing performance by the lens based on the chart image picked up by the camera 10, and displays it on a display device 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a depiction performance evaluation device for evaluating depiction performance of a photographic lens of a camera.

[0002]

2. Description of the Related Art Conventionally, in evaluating the imaging performance of a photographic lens of a camera, a chart plate on which a chart for resolving power evaluation is described is attached to a camera (examined camera) having a lens to be inspected. A method is known in which an image is taken on a film, and the film is developed to visually determine the resolving power of a chart diagram, or a method of evaluating performance using an MTF. The use of a solid-state imaging device (hereinafter referred to as a CCD) in this MTF inspection apparatus has also been disclosed in
No. 35052, No. 64-11887, No. 1
No. 45861, and Japanese Utility Model Application Laid-Open No. 58-186454.

[0003]

The method of visually judging the image of the film on which the chart is photographed has to rely on the skill of the person who judges the chart, and the method cannot be evaluated unless the operator is a skilled worker. There was a problem in that the results varied, resulting in a lack of reliability. In addition, as a matter of course, it has to go through a work process of developing a film, which is very troublesome.

On the other hand, since the output result of the MTF inspection apparatus is a curve graph, it is difficult to intuitively understand whether or not the resolving power of the lens is within a specified range. There was a problem that I had to rely on. In the camera inspection, for example, an AF (autofocus) function inspection and an LD (lens drive) amount inspection are also performed in addition to the lens resolution. For example, the MTF inspection apparatus performs the AF inspection and the LD inspection. It was not possible to double.

[0005] From the above viewpoint, the present applicant uses a CCD camera for the imaging performance inspection, digitally outputs the imaging performance of the lens including the resolution, and evaluates the image so that the inspector can clearly judge the quality of the lens. The device was filed as Japanese Patent Application No. 9-7170. In this method, a reticle having a light-diffusion surface in the form of ground glass is arranged on the focal plane of the camera, this is imaged by a solid-state imaging camera, and the resolution is determined by a determination means.

However, in this application, a frosted glass surface portion having a diffusion surface particle size of about 1 to 6 microns and having no unevenness must be provided as a focusing plate on one side of the condenser lens. , It was very difficult to make it. Further, it is almost impossible to form a number of ground glass portions having the same diffused surface state, and there is a problem that the appearance changes when the condenser lens with the reticle is replaced. Further, there is a problem that the condenser lens with a focusing screen is easily damaged when handled.

Further, since the particle size of the diffusing surface becomes non-uniform, absolute comparison cannot be made for each image limit to be measured, a reticle must be recreated every time the incident angle changes, and aberrations may occur depending on the set position. However, there was also a problem that it could not be ignored.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is a camera capable of easily evaluating a lens drawing performance including a resolving power without using a focusing screen which requires the above-described accuracy. The purpose of the present invention is to obtain a depiction performance evaluation device.

[0009]

SUMMARY OF THE INVENTION In the present invention, a chart for evaluation of imaging performance is formed on a focal plane through a lens, and the imaging performance of the camera is evaluated using the formed image. In the device, one end is positioned at the focal plane of the camera as a light incident surface,
An optical fiber bundle extending rearward of the camera in a state parallel to the photographing optical axis of the camera with the other end as a light emitting surface, and an enlarging optical system arranged at a position facing the light emitting surface of the optical fiber bundle A solid-state imaging device camera that captures a chart image obtained via the magnifying optical system; and a determination unit that receives an output of the solid-state imaging device and determines the drawing performance of the chart by the lens. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, reference numeral 1 denotes a variable focal length zoom photographing lens 1a movable between a telephoto state (hereinafter abbreviated as a T state) and a wide-angle state (hereinafter abbreviated as a W state) and its photographing. The camera to be inspected comprises a camera body 1b to which a lens 1a is attached, and is attached to the transport device 3 while being detachably held by the holder 2. Here, when the camera to be inspected 1 is attached to the holder 2, the back cover (not shown) is open.

In front of the taking lens 1a of the camera 1,
A chart plate 4a for evaluating the drawing performance in the T state at a predetermined distance and a chart plate 4 for evaluating the drawing performance in the W state
The chart plate 4 made of “b” is provided so as to be movable in the direction of the optical axis of the photographing lens of the camera 1. The above W
The chart plate 4b is also configured to be able to retreat laterally from the optical axis. Further, on the chart plate 4, a drawing performance evaluation diagram such as a known resolving power evaluation chart diagram is drawn.

On the other hand, a flat-fiber optic plate (Flat-fiber Opt) is provided at a position corresponding to the focal plane of the camera (where the film is disposed).
One end 5a of the optical fiber bundle 5 called an icPlate (hereinafter abbreviated as F-FOP) is disposed in a state of being held by one end of a hollow cylindrical holder 8 formed in an L shape. That is, one end 5a of the optical fiber bundle 5 is connected to the photographing lens 1a.
Is the incident surface of the chart image that has passed through. On the other hand, the other end 5b of the optical fiber bundle 5 extends rearward along the optical axis, and serves as an emission surface of a chart image.

Further, the holder 8 holds the optical fiber bundle 5
And an optical system 7 for enlarging the chart image emitted from the camera by about twice. This optical system 7 has a high refractive index (large NA).
It consists of an objective lens, and specifically uses an objective lens for a microscope. Further, a mirror 9 for bending the optical path of the image from the magnifying optical system 90 by 90 degrees is fixed to the L-shaped refraction portion of the holder 8. A CCD camera 10 is attached to the other end of the holder 8 so as to receive an image from the magnifying optical system 7 via the mirror 9. These optical fiber bundle 5, magnifying optical system 7, holder 8,
An inspection block 11 is constituted by the mirror 9 and the CCD camera 10.

The inspection block 11 is movably held in the xyz directions and is held by the transfer device 3 by an appropriate means. Further, the CCD camera 10 is held by the holder 8 so as to be rotatable in the w direction about its imaging optical axis.

Further, the CCD camera 10 is connected to an arithmetic unit 12 as a judging means by appropriate means, and this arithmetic unit 12 is connected to a display unit 13. here,
The arithmetic unit 12 outputs the drawing performance of the lens as a digital value based on the chart image captured by the CCD camera 10. Specifically, in the arithmetic unit 8, the maximum output portion (Bmax) and the minimum output portion (Bmin) in each cell of the CCD make the contrast C by C = (Bmax−Bmin) / (Bmax + Bmin). Output. The display device 13 displays the output result of the arithmetic device 12 on a cathode ray tube or prints the result with a printer. The computing device 14 and the display device 15 are attached to the transport device 3 by appropriate means.

Here, F-FOP as the optical fiber bundle is used.
Will be described. Fiber Optic Plate
e (hereinafter abbreviated as FOP) is a magazine “Technical Report of the Institute of Television Engineers of Japan,” Vol. 14． No. 53 (Sep. 19)
As described in 90), the optical fibers are bundled into a rod shape and are known as members for transmitting optical information. The optical fiber is formed to have the same diameter over the entire length, and has a configuration in which a real image formed on the incident side end surface comes out of the exit side end surface as it is. The FOP in which the entrance side and the exit side are formed to have the same diameter is particularly called an F-FOP. In this embodiment, an optical fiber having a diameter of 3 microns is used as shown in FIG.

In the above evaluation apparatus, first, the camera 1 to be inspected is held by the holder 2, the focal length of the lens is set to the focal length to be inspected, such as the W end or the T end, and the chart plate 4a or 4b is adjusted accordingly. Set the position of. Next, the incident end face 5a of the optical fiber bundle 5 is moved to a position corresponding to the chart to be analyzed via the holder 8. At this time, a real image of a chart is formed on the incident end face 5a of the optical fiber bundle 5. Further, since the holder 8 is movable in the xyz directions, it is possible to freely perform an image analysis of a required portion.

Next, by operating an appropriate switch (not shown), the image pickup result by the CCD camera 10 is calculated by the calculation device 12, and a value based on the contrast C is output as a digital value as a value for evaluating the drawing performance. This is displayed on the display device 13.

[0019]

According to the present invention, since the lens depiction performance is output as a digital value as a value indicating the image formation state of the image, the inspector can clearly determine the quality of the lens, and furthermore, can determine the lens position at any position. Inspection can also be made possible.
Also, from the viewpoint that not only the lens resolving power determination but also the magnitude of the contrast and the degree of focusing have a corresponding relationship,
It can also be used to determine the quality of the optical performance of a camera such as AF or LD, and a single evaluation device can comprehensively evaluate the optical state of the camera.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system according to an embodiment of the present invention.

FIG. 2 is a diagram showing an optical fiber bundle in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Test camera 2 Holder 3 Transporting device 4 Chart board 5 Optical fiber bundle 7 Magnifying optical system 10 CCD camera

Claims (1)

[Claims] 1. A depiction performance evaluation apparatus for a camera, which forms a depiction performance evaluation chart on a focal plane through a lens, and evaluates the depiction performance of the lens using the formed image. An optical fiber bundle that is positioned at the focal plane of the camera and extends rearward from the camera in a state in which the other end is a light emitting surface and is parallel to the imaging optical axis of the camera; and a light emitting surface of the optical fiber bundle. A solid-state imaging device camera that captures a chart image obtained via the magnifying optical system; a solid-state imaging device that receives an output of the solid-state imaging device; And a determination means for determining the image quality.