JPH01147679A - Pattern measuring instrument - Google Patents

Abstract

PURPOSE:To accurately obtain a luminance distribution in the width direction of a projected pattern image by changing a slice level in response to the peak value of data outputs of said pattern image. CONSTITUTION:A projected pattern image is formed at an eyeground Er to be examined by a projection system 1. While another projected pattern image is formed at a CCD 3 by an image forming optical system 2. Then the pattern image of the CCD 3 is stored in a frame memory 24 after A/D conversion and then sent to a RAM 28 via a transfer processing means 27. Based on data stored temporarily in the RAM 28, a microprocessor 25 increases the slice level with a high peak level and vice versa to obtain the position of the luminance centroid in the width direction. Thus the luminance distribution is accurately obtained regardless of the variance of light quantity of the projected pattern.

Description

Detailed Description of the Invention Field of the Invention The present invention relates to an improvement in a pattern measuring device used in an autorefractometer or the like.

(Background of the Invention) In recent years, as a pattern measuring device, a photoelectric conversion element having a large number of pixels (e.g. , two-dimensional image sensor such as COD), scans this photoelectric conversion element to extract photoelectric information for each pixel, and stores the photoelectric information of each pixel in each address of the frame memory corresponding to each pixel. A central processing unit is used to extract a group of data corresponding to the brightness distribution in the band width direction of the projected pattern image as output, and this output is processed at a predetermined slice level to determine the brightness distribution. There is a method in which the position of the center of gravity is determined and the shape of the projected pattern image is determined by performing predetermined arithmetic processing based on the determined position of the center of gravity (
Patent Application No. 1988-102800, Patent Application No. 1983-19371
(See No. 6).

This pattern measuring device is configured to fix the slice level and determine the center of gravity position of the luminance distribution in the band width direction of the projected pattern image when determining the shape of the projected pattern image.

(Problems to be Solved by the Invention) By the way, a projected pattern image based on a pattern of a known shape projected through the fundus or cornea may contain uneven reflection of the fundus, clouding of the crystalline lens, or eyelashes. There is some unevenness in the amount of light due to the influence of these factors. When this light intensity unevenness exists, a central processing unit is used to call a group of data in the projection pattern image portion where the light intensity unevenness exists and that corresponds to the luminance distribution in the band width direction of the projection pattern image. In this case, the output of this group of data becomes lower or higher as a whole compared to the output of the group of data of other projection pattern image parts. For example, FIG. 5 shows the output V of a group of data M in a projection pattern image portion with uneven light intensity and the output V of a group of data N in another projection pattern image portion. If the output V of N is processed with a fixed slice level L, a group of data N
can be sliced at an appropriate level for the peak output α, but a group of data M cannot be sliced at an appropriate level for the peak output β, and the obtained center of gravity position is not the actual brightness distribution. As a result, the shape of the projected pattern image cannot be determined accurately. In FIG. 5, the horizontal axis corresponds to each address where data is stored, a□', a, /, a3', and 84' correspond to the addresses sliced by the slice level L. Y), (xt-Y2) is an address corresponding to the center of gravity of the luminance distribution in the band width direction of the projected pattern image.

Therefore, one object of the present invention is to provide a pattern measuring device that can determine the center of gravity of the luminance distribution in the band width direction of a projected pattern image as appropriately as possible, regardless of the presence of unevenness in the amount of light in the projected pattern image. be.

Mantle (7) 4 Waves (Means for Solving the Problems) The feature of the pattern measuring device according to the present invention is that when the central processing unit responds to the peak output of the output of a group of data, when this peak output is large, , the slicing level is changed so that the slicing level for slicing the output becomes large and the slicing level becomes low when the peak output is small.

(Example) Hereinafter, an example in which a pattern measuring device according to the present invention is applied to an autorefractometer will be described with reference to the drawings.

In FIG. 1, 1 is a projection optical system for forming a ring-shaped image as a projection pattern image on the fundus Er of the eye E to be examined;
2 is an imaging optical system for forming a ring-shaped image formed on the fundus Er on a CCD 3 as a photoelectric conversion element; 4 is a fixation target optical system for fixating the eye E in a foggy vision state;
Reference numeral 5 denotes an optical system 11 for observing the anterior segment of the eye E to be examined.

The projection optical system 1 includes a perforated mirror 6 and an infrared LED light source 7.
, a relay lens 8, a conical prism 9, a ring-shaped aperture stop 10, a relay lens 11, and an objective lens 21.

The imaging optical system 2 includes an objective lens 21 shared with the projection optical system 1,
It consists of a perforated mirror 6, a relay lens 13, and a CCD 3. The fixation target optical system 4 includes an objective lens 21 shared with the projection optical system 1, an infrared transmission visible reflection mirror 14, and a relay lens 15.
, a fixation target 16, and the optical system for viewing the anterior eye segment consists of an objective lens 21, a half mirror 20, a relay lens 17, an image pickup tube 18, and a monitor television 19. Ring-shaped aperture diaphragm 10 and fundus Er, CCD 3 and fundus Er, infrared light LE
D light source 7, perforated mirror 6, and eye to be examined! [! The arrangement of the optical systems 1 to 5 and the arrangement of their constituent elements, such as lEp being in a conjugate relationship, are as described in Japanese Patent Application Laid-open No. 164829/1983, so a detailed explanation thereof will be omitted.

During the measurement, the image of the anterior segment Ha is always displayed on the monitor TV 19.
The examiner appropriately monitors whether the anterior segment Ha is in a predetermined position. The subject sees the fixation target 16 as a blur, and the subject's eye E is fixed. In this state, the infrared light refracted by the conical prism 12 passes through the ring-shaped aperture diaphragm 10 and is reflected by the perforated mirror 6. It is reflected and reaches the fundus Er through the first objective lens 21, and a primary ring-shaped image R1 is formed on the fundus Er. This first ring-shaped image R
The infrared light that formed the image 1 is reflected by the fundus Er, passes through the hole 6a of the perforated mirror 6, and reaches the CCD 3, and a secondary ring-shaped image R3 as a band-shaped projection pattern image is formed on the CCD 3.
Formed in D3.

FIG. 2 shows the secondary ring-shaped image R7 formed on the CCD 3, and the primary ring-shaped image R1 and the secondary ring-shaped image R3 correspond to the refractive power of the eye E to be examined. It has been known that the size changes, and that if the eye E has astigmatism, it becomes elliptical. In each pixel GLj (i=1-m, j=1-n) of the CCD 3, signal charges corresponding to the luminance of each pixel of the ring-shaped image R3 are accumulated. The CCD 3 is driven by a drive circuit 22 of the pattern measuring device shown in FIG.
The signal charge accumulated in each pixel of D3 is sequentially extracted as data by A/D conversion W23, transferred to each address of frame memory 24, and is converted into a second ring-shaped image R3.
The data of each pixel is temporarily stored in each address corresponding to each pixel in the frame memory 24.

The pattern measuring device includes 1, a microprocessor 25 as a central processing unit, and a read-only memory (ROM).
26, transfer processing means 27, and random access memory (RAM) 28. A read-only memory (ROM) 26 stores address information necessary for determining the shape of the second ring-shaped image R7 in the frame memory 24. Here, as shown in FIGS. 2 and 3, pixels GL existing on lines of meridian directions A' to F' of the eye E to be examined are
Address information corresponding to the address of j is stored in a read-only memory (ROM) 26. Note that this read-only memory (ROM) 26 also stores information other than address information.

The transfer processing means 27 has a read/write control register 29 and a control register 30. This transfer processing means 2
7 has a function of calling data stored at each address of the frame memory 24 without going through the microprocessor 25 based on the address information stored in the read-only memory (ROA) 26. When the transfer start command signal TRI is input from the microprocessor 25 to the read/write control register 29 via the control bus, the read/write control register 29 transfers the address stored in the read-only memory (ROM) 26 via the address bus. The read-only memory (ROM) of the data stored in each address of the frame memory 24 is called based on the address information.
26 address information is sequentially called to the control register 30, and this control register 30
The data is transferred to random access memory (RAM) 28 by .

During this transfer process, the microprocessor 25 is executing other program processes, and the read-only memory (
When the transfer processing of the data stored at each address of the frame memory 24 to the random access memory (RAM) 28 based on the address information stored in the ROM 26 is completed, the read/write control register 29 indicates the end of the transfer. A signal Te is output to the microprocessor 25. Thereafter, the microprocessor 25 performs arithmetic processing to determine the shape of the second ring-shaped image R3 based on the data temporarily stored in the random access memory (RAM) 28.

In this way, the random access memory (RAM) 2g temporarily stores and holds the minimum data required for determining the shape of the second ring-shaped image R3. For example, as shown in FIG. 3, meridian directions A', D' of the eye E to be examined
Suppose that we take out a group of data M and N, which are address data corresponding to each pixel GLJ existing on the line of , and which correspond to the luminance distribution in the band width direction of the projected pattern image.
The output distribution will be as shown in FIG. In FIG. 4, the horizontal axis corresponds to each address where data is stored, and L is the slice level.

The microprocessor 25 first calculates a group of data M using a counter (not shown) as a process for determining the center of gravity position of the luminance distribution in the band width direction of the projected pattern image.
, N. Determining the address of the peak output of this group of data M, N is performed by determining the address position of the virtual peak output of the group of data M, N using the slice level L. This is done by slicing V and finding the address existing at the boundary of the slice level L. Here, the microprocessor 25 calculates the peak outputs α, β according to the peak outputs α, β of the group of data M, N. When is large, the slice level L
So that it gets bigger, and.

When the peak outputs α and β are small, the slice level is changed and controlled so that the slice level becomes low. Here, the microprocessor 25 calculates the slice level L for the peak outputs α and β when determining the barycenter position of the luminance distribution in the band width direction of the projected pattern image in the different meridian directions A′ to F′ of the eye Er. The ratio K is controlled to be constant.

That is, K=α/L=β/L.

The counter is based on this slice level L.

The addresses existing on the boundary are counted and output to the microprocessor 25 as address information.

The address information is assumed to be al, a7, al, and a4.

This address information a1, at, a3. a4 is the intersection point a16*a26, as between the boundary line Q1, base, of the secondary ring-shaped image R2 shown in FIG. 3, and the meridian directions A', D'. , al0
It corresponds to Therefore, the address information a1, a2
and address information a1, a.

By averaging these, address information corresponding to the peak of the luminance distribution in the band width direction of the projected pattern image can be obtained. Let the address information corresponding to the peak of the luminance distribution be (x x - y z ), (Xi - Yz), where the sign or X-axis direction is indicated, and the symbol Y indicates the Y-axis direction; The address information corresponding to the peak of the luminance distribution is determined as the position from the origin 0. Meridian direction B'.

Similarly, address information corresponding to the peak of the luminance distribution is obtained for C', E', and F'. In this way,
Here, address information corresponding to six brightness peaks around the origin 0, Cxx=y-), (Xs, Yz),
(Xi, Y3), (x,,Y,).

Cxs, yi) and (xst y,) are determined, and the shape of the projected pattern image is determined by a known processing method based on the address information.

That is, in Fig. 3, assuming that the horizontal scanning direction is the X-axis, the major axis of the ellipse R7 is a (the diameter in the meridian direction A), the minor axis is b (the diameter in the meridian direction C), and the major axis a is relative to the X-axis. Assuming the angle φ, the angle φ corresponds to the astigmatic axis, the major axis a corresponds to the refractive power of the strong principal meridian of astigmatism, and the size of the ellipse corresponds to the spherical power, so the coefficient A is calculated based on the following -' general formula. , B, and C, the refractive powers S, C, and A can be obtained.

Ax"+By"+Cxy=1 -■ or more,
Although the embodiment has been described, for example, for different meridian directions A' and B' of the eye to be examined, the center of gravity of the luminance distribution in the band width direction of the projected pattern image is 1! (x,, Y,
), when finding (Xse ya).

The slice level is set by predicting that the output based on the data at the address (x - = y z ) corresponding to the center of gravity of the luminance distribution in the meridian direction A' measured last time is the peak output in the meridian direction B measured this time. You can also change it. In this way, the time required to detect the peak output can be shortened, and the overall measurement time can be shortened.

Further, in this embodiment, an example in which the pattern measuring device is applied to an auto-reflex aritometer has been described, but the pattern measuring device according to the present invention can also be applied to a keratometer.

Since the pattern measuring device according to the present invention is constructed as described above, it is possible to determine the center of gravity of the luminance distribution in the band width direction of the projected pattern image, regardless of the presence of unevenness in the amount of light in the projected pattern image. This has the effect that it can be determined as appropriately as possible.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the main part configuration when the pattern measuring device according to the present invention is applied to an autorefractometer, Fig. 2 is a diagram showing a projected pattern image formed on the CCD, and Fig. 3 is a diagram showing the projected pattern image. The enlarged views of the projected pattern images, FIGS. 4 and 5, are explanatory diagrams for explaining the process for determining the shape of the projected pattern. 1... Projection optical system 3... Area CCD
, 25...Microprocessor 24...Frame memory E...Eye to be examined Er...Fundus R6...Second ring image (projection pattern image) M, N
...Data α, β...Peak output 2nd
Figure 3 Figure 4 Figure 5

Claims (4)

[Claims] (1) A band-shaped projected pattern image formed based on a pattern of a known shape projected via the eye to be examined is photoelectrically converted by a photoelectric conversion element having a large number of pixels, and the photoelectric conversion element is scanned. The photoelectric information of each pixel is stored as data in each address of the frame memory corresponding to the pixel, and a group of data corresponding to the luminance distribution in the band width direction of the projected pattern image is output using the central processing unit. A pattern measuring device that extracts the output and processes the output at a predetermined slice level to obtain the center of gravity position of the luminance distribution, and performs a predetermined calculation based on the obtained center of gravity position to determine the shape of the projected pattern image. According to the peak output of the output of the group of data, the central processing unit increases the slice level when the peak output is large, and decreases the slice level when the peak output is small. A pattern measuring device characterized in that the slice level is changed as follows. (2) The central processing unit controls the ratio of the slice level to the peak output to be constant when determining the center of gravity of the luminance distribution in the band width direction of the projection pattern image. A pattern measuring device according to claim 1. (3) When determining the centroid position of the luminance distribution in the band width direction of the projected pattern image in different meridian directions of the eye to be examined, the central processing unit may Claim 1: The slice level is changed by predicting that the output based on the data of the address corresponding to the gravity center position of the luminance distribution is the peak output in the meridian direction currently measured.
The pattern measuring device described in Section. (4) Pattern measurement according to claim 1, wherein the pattern of the known shape is projected onto the fundus, and the central processing unit calculates the refractive power based on the projected pattern image. Device.