JP2002048678A - Lens performance evaluator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens performance evaluator which can evaluate the drawing performance of the lens quickly and with higher resolutions. SOLUTION: This apparatus is provided with a half mirror 3 to divide a luminous flux which passes through a lens 4 from a chart 5 to be imaged on a focal plane later, two CCD line sensors 1a and 1b arrayed on the imaging planes of the respective luminous fluxes by shifting the positions of pixels photographing the luminous fluxes of the image of the chart 5 divided by the half mirror 3 by a half of the pixel pitch thereof horizontally or vertically and an image processing part 2 for synthesizing output signals of the two CCD line sensors 1a and 1b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens performance evaluation apparatus for evaluating a lens drawing performance such as a contrast of a lens used for a camera, a digital camera or the like.

[0002]

2. Description of the Related Art Conventionally, a piezo element (mechanical mechanism)
Japanese Patent Application Laid-Open No. 9-55892 discloses a solid-state imaging device that evaluates the imaging performance of a lens, such as the contrast of the lens, while shifting the pixels of the imaging element by a small pitch.

An outline of a conventional solid-state imaging device disclosed in the publication will be described with reference to FIG.

The conventional solid-state image pickup device shown in FIG. 9 includes a chart 105, a photographing lens 104 arranged opposite to the chart 105, a CCD line sensor 100 as an image pickup device, and a CCD line sensor 100. A driving CCD line sensor driving unit 101 and a CCD line sensor 1 driven by the CCD line sensor driving unit 101
It comprises a feed mechanism 102 using a piezo element that feeds 00 at a fine pitch, and an image memory 103 that takes in and stores image data captured by the CCD line sensor 100.

In this solid-state image pickup device, the image shown in FIG. 105 for evaluating the drawing performance is formed on the element surface of the CCD line sensor 100 by the lens 104,
In accordance with the basic timing signal output from the line sensor drive unit 101, the CCD line sensor 100 captures the image of the chart 105 for each line. And
A one-line reading completion signal is sent from the CCD line sensor driving unit 101 to the image memory 103, whereby the image memory 103 temporarily stores the image data of the chart 105 for each line.

Next, a feed mechanism 10 using a piezo element
2, when the position of each pixel of the CCD line sensor 100 is shifted by 画素 pixel, the CCD line sensor 100
Captures the image of the chart 105 again line by line. Also in this case, the image memory 103 has the chart shown in FIG.
05 is temporarily stored for each line. The image data for each line read and temporarily stored in this manner is synthesized by an image processing unit (not shown), output as an image of a chart 105, and used for evaluation of the lens 104.

[0007]

However, the conventional solid-state imaging device disclosed in the above publication has the following problems.

In a conventional solid-state imaging device, in order to obtain a high resolution, the CCD line sensor 100 is step-moved by a feed mechanism 102 using a piezo element to capture image data.

That is, the CCD line sensor 100 is mechanically moved by １ ／ pixel using a piezo element (piezoelectric element) to obtain a higher resolution than the resolution based on the pixel array of the CCD line sensor 100 itself. Therefore, the reading speed of the chart 105 shown in FIG.
There is a problem that the scanning time is delayed by the time required for the mechanical scanning time of zero.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and does not require a mechanism for moving an image pickup device, and quickly and at high resolution without a mechanical scanning time. The present invention provides a lens performance evaluation device capable of performing the following.

[0011]

According to a first aspect of the present invention, there is provided a lens performance evaluation apparatus comprising: a lens performance evaluation chart;
A light splitting member that splits the light flux passing through the lens from the chart and forming an image on its focal plane, after passing through the lens,
The two pixels arranged on the imaging plane of each light beam by shifting the position of the pixel for capturing each light beam of the chart image divided by the light dividing member by １ ／ of the pixel pitch in the horizontal direction or the vertical direction. An image sensor and an image processing unit that combines output signals of the two image sensors are provided.

According to the present invention, the positions of the pixels of the two image pickup devices are set to one pixel pitch in the horizontal or vertical direction.
Since the arrangement is such that the chart image is picked up by being shifted by / 2 and the output signal of each image pickup element is synthesized by the image processing unit, a mechanism for moving the image pickup element as in the conventional example is unnecessary. This makes it possible to quickly capture images of the chart at twice the resolution without requiring a special scanning time, and to evaluate the drawing performance such as the contrast of the lens.

According to a second aspect of the present invention, there is provided a lens performance evaluation apparatus comprising: a lens performance evaluation chart; and a light beam passing through the lens from the chart and forming an image on a focal plane thereof, after passing through the lens. a plurality of light splitting members for repeating the splitting n times (n is a positive integer), 2 ⁿ image sensors for picking up each light beam of the chart image split by the plurality of light splitting members, and an image processing unit for combining the output signals of the 2 ⁿ pieces of the image sensor, the 2 ⁿ
A plurality of image sensors are arranged on the image forming plane of each light beam so that the position of the pixel is shifted in the horizontal or vertical direction by 1/2 ⁿ of the pixel pitch in each of the divided light beams.

According to the present invention, the positions of the pixels of the 2 ⁿ imaging elements are shifted by 1/2 ⁿ of the pixel pitch in the horizontal direction or the vertical direction for each of the divided light fluxes to form a chart. Since an image is captured and the output signal of each image sensor is synthesized by the image processing unit, a mechanism for moving the image sensor as in the conventional example is not required, and the mechanism can be quickly and quickly performed without requiring a mechanical scanning time. It becomes possible to take an image of the chart with ⁿ times resolution and evaluate the drawing performance such as the contrast of the lens.

[0015]

Embodiments of the present invention will be described below in detail.

(Embodiment 1) FIG. 1 is a configuration diagram showing a lens performance evaluation apparatus according to Embodiment 1 of the present invention.

The lens performance evaluation device of the first embodiment is
The image of the chart 5 having, for example, a striped pattern for evaluating the drawing performance of the lens is divided by the lens 4 and further through the half mirror 3 into two parts, and is constituted by a planar solid-state imaging device. The light enters the CCD line sensor 1a and the CCD line sensor 1b.

Here, the CCD line sensor 1a and the CC
As shown in FIG. 2, the D line sensor 1b is provided on the image forming plane of each of the two divided light beams in the horizontal direction for a half pitch of the pixel pitch p of the CCD line sensor 1a (1b), ie, p / They are offset by two.

Output signals from the CCD line sensor 1a and the CCD line sensor 1b are sent to an image processing unit 2 where they are alternately synthesized in the horizontal direction and output as an image signal 6.

FIG. 3 is a diagram showing a horizontal density distribution of the image of the chart 5. 4 (a), (b), and (c)
Each of the CCD line sensors 1a and 1b on one arbitrary line, which is obtained when the CCD line sensors 1a and 1b are shifted in the horizontal direction by 1/2 pitch as shown in FIG. FIG. 6 is a diagram showing output signals of the CCD line sensor 1b and their combined signals (image signals 6).

Generally, in a CCD line sensor, a gray scale signal of an image formed at the center of the image is sampled and output at a pixel pitch p.

Therefore, when the chart image of the grayscale signal as shown in FIG. 3 is formed on the CCD line sensor 1a,
As shown in the plot of (a), sampling is performed at pixel pitch p intervals, but the gray level signal of the image corresponding to the intermediate portion of each pixel is unknown.

However, this gray scale signal is shifted by p / 2 in the horizontal direction with respect to the CCD line sensor 1a.
The CD line sensor 1b outputs a correct signal as shown in the plot of FIG.

FIG. 4 (c) shows an image signal 6 obtained by synthesizing these in the image processing unit 2, and FIG.
The gray-scale signal of the chart image indicated by is sampled at twice the resolution in the horizontal direction, and it is possible to realize a high-resolution lens description performance evaluation.

In the first embodiment, the CCD line sensor 1a and the CCD line sensor 1b are displaced by a half pitch in the horizontal direction.
The CD line sensor 1b may be shifted vertically by ピ ッ チ pitch. In this case, the gray scale signal of the chart image is sampled with twice the resolution in the vertical direction, and the depiction performance of the high resolution lens Evaluation can be realized.

(Embodiment 2) FIGS. 5 to 7 show Embodiment 2 of the present invention. FIG. 5 is a configuration diagram showing a lens performance evaluation device according to Embodiment 2 of the present invention.

In the lens performance evaluation apparatus according to the second embodiment, the image of the chart 5 having, for example, a striped pattern for evaluating the depiction performance of the lens is transmitted through the lens 4 to the half mirror 3-1. Divided.

Each of the two divided light beams is further divided into two light beams by two half mirrors 3-2 to form four light beams, and a CCD line sensor 1-1 composed of a surface-type solid-state image pickup device. , 1-2, 1-3, and 1-4.

Here, the CCD line sensors 1-1, 1-
As shown in FIG. 6, reference numerals 2, 1-3 and 1-4 denote, on the image forming plane of each of the four divided light beams, one-fourth of the pixel pitch p of each CCD line sensor in the horizontal direction, ie, They are staggered by p / 4.

CCD line sensors 1-1, 1-2, 1-
The output signals from 3, 3 and 4 are sent to the image processing unit 2,
The images are synthesized while being shifted by p / 4 in the horizontal direction, and output as an image signal 6.

FIGS. 7A, 7B, 7E, and 7D show the CCD line sensors 1-1, 1-2, 1-3, respectively.
FIG. 7 (e) is a diagram showing output signals 1-4, and FIG. 7 (e) shows these composite signals (image signal 6).

As in the case described above, the CCD line sensor samples and outputs the grayscale signal of the image formed at the center of the pixel at the pixel pitch p.

Therefore, when the chart image of the gray scale signal as shown in FIG. 3 is formed on the CCD line sensor 1-1, the chart image shown in FIG.
As shown in the plot of (a), sampling and output are performed at an image pitch p interval, but the gray scale signal of the image corresponding to the intermediate portion and the peripheral portion of each pixel is unknown.

However, these gray-scale signals are output from the CCD line sensors 1-2, 1-3, and 1-4 which are horizontally shifted by p / 4 from the CCD line sensor 1-1, as shown in FIG. b) Correct output is obtained as shown in the plots of (c) and (d).

FIG. 7E shows an image signal 6 obtained by synthesizing these in the image processing unit 2, and FIG.
The gray-scale signal of the chart image indicated by is sampled in the horizontal direction with four times the resolution, and it is possible to realize a high-resolution lens description performance evaluation.

In the second embodiment, the CCD line sensors 1-1, 1-2, 1-3, and 1-4 are arranged shifted by 1/4 pitch in the horizontal direction.
1, 1-2, 1-3, and 1-4 may be arranged so as to be shifted by 1/4 pitch in the vertical direction. In this case, the grayscale signal of the chart image is sampled in the vertical direction with four times the resolution. This also makes it possible to realize a high-resolution lens imaging performance evaluation.

In the second embodiment, for the sake of simplicity, the light beam passing through the lens 4 is
Although the case of dividing into two times by -1, 3-2, that is, into a total of four lines has been described, this can be easily extended to the case of dividing into n times.

[0038] That is, the light flux passing through the lens 4, the half mirror 3-1, 3-2, ..., 3-n configured to sequentially transmits or reflects, 2 ⁿ book divided in this way Light beam in the horizontal or vertical direction, respectively.
/ ^{2 n} pitch by shifting ² was placed in the ⁿ CCD line sensors 3-1, 3-2, ..., it is sufficient to enter the 3-2 ^n.

The output signal from each CCD line sensor is
The image is synthesized by the image processing unit 2 while being shifted by p / ²ⁿ in the horizontal or vertical direction, and is output as an image signal 6. FIG. 8 shows this image signal 6. According to this, the gray-scale signal of the chart image is sampled with a resolution of ²ⁿ times in the horizontal or vertical direction,
Further, it is possible to evaluate the depiction performance of a high-resolution lens.

[0040]

According to the first aspect of the present invention, imaging is performed by disposing two image sensors in the horizontal or vertical direction by half the pixel pitch and arranging them on the image plane of each light beam. A gray scale signal of a chart image is sampled in a horizontal direction or a vertical direction with twice the resolution without moving the element itself, and a lens performance evaluation device capable of realizing a high resolution lens evaluation performance can be provided.

According to the invention of claim 2, 2ⁿPieces
The image element is moved horizontally or vertically in half the pixel pitch.ⁿ
By shifting each light beam and arranging it on the image plane of each light beam,
The grayscale signal of the chart image can be obtained without moving the element itself.
2 horizontally or vertically ⁿSun with double resolution
To evaluate the imaging performance of a lens with higher resolution.
A lens performance evaluation device that can be realized can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a lens performance evaluation device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an arrangement of two imaging elements in the lens performance evaluation device according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a grayscale distribution of a chart image in the lens performance evaluation device according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing output signals and composite signals of two image sensors in the lens performance evaluation device according to the first embodiment of the present invention.

FIG. 5 is a configuration diagram illustrating a lens performance evaluation device according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram showing an arrangement of four image sensors in a lens performance evaluation device according to a second embodiment of the present invention.

FIG. 7 is an explanatory diagram showing output signals and combined signals of four image sensors in a lens performance evaluation device according to a second embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a composite signal of output signals of ²ⁿ image sensors in the lens performance evaluation device according to the second embodiment of the present invention.

FIG. 9 is a schematic diagram showing a conventional solid-state imaging device.

[Explanation of symbols]

 1a CCD line sensor 1b CCD line sensor 1-1 CCD line sensor 1-2 CCD line sensor 1-3 CCD line sensor 1-4 CCD line sensor 2 Image processing unit 3 Half mirror 3-1 Half mirror 3-2 Half mirror 4 Lens 5 Chart 6 Image signal

Claims (2)

[Claims] 1. A lens performance evaluation chart, a light splitting member that splits a light flux passing through the lens from the chart and forming an image on a focal plane thereof after passing through the lens, and being split by the light splitting member Two image sensors arranged on the imaging plane of each light beam by shifting the position of a pixel that captures each light beam of the chart image in the horizontal or vertical direction by の of the pixel pitch, An image processing unit for synthesizing output signals of the image sensor of Claim 1. 2. A chart for lens performance evaluation, and a light beam passing through the lens from the chart and forming an image on its focal plane is divided into n times (n is a positive integer) after passing through the lens. A plurality of light splitting members for repeating, 2 ⁿ image pickup elements for picking up each light beam of the chart image divided by the plurality of light splitting members, and output signals of the 2 ⁿ image pickup elements An image processing unit for synthesizing, wherein the 2 ⁿ image sensors are arranged on the imaging plane of each light beam, and for each of the divided light beams, the position of the pixel is set to 1 pixel pitch in the horizontal or vertical direction. / 2. A lens performance evaluation apparatus, wherein the lens performance evaluation apparatus is shifted by ⁿ .