JPS625146A - Optical characteristic measuring apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an optical measuring device for measuring the optical characteristics of an optical member to be tested, and is particularly suitable for automatic curvature measuring devices, automatic lens refractometers, etc. is.

(Background of the Invention) As this type of device, for example, Japanese Patent Application Laid-Open No. 57-19740
There is an automatic measuring device for the radius of curvature as shown in Japanese Patent No. 5. This automatic radius of curvature measuring device projects two pairs of bright spots onto the optical member to be tested, photoelectrically converts the reflected image on the optical member to be tested, and uses this photoelectric conversion signal to determine the amount of light received by the receiver. All intervals between six pairs of reflected images on the surface (intervals of projections projected in two predetermined directions) are determined, and from this interval, the radius of curvature and the direction of the principal axis of the optical member to be inspected are determined.

Now, in such a device, it is possible to use a position detector that can obtain absolute coordinates corresponding to the position of the reflected image as a light receiver, but CC, which is a type of position detector,
Digital elements such as D have the disadvantage that their resolution is not very high, while analog elements that output analog voltages corresponding to coordinate positions have a problem of lacking stability.

Therefore, in the above publication, photoelectric conversion elements are provided corresponding to each reflected image, the light receiving surfaces of these elements are scanned in a predetermined direction with a chopper, the reflected image position is time-converted, and the phase difference of the photoelectric conversion signal is calculated. An example has been proposed in which each reflected image corresponds to a projection distance in a predetermined direction.

However, in order to measure the phase difference, it is inevitable that a phase shift will occur (due to filters in the processing circuit, etc.).
Furthermore, since the phase shift is affected by temperature and other factors, some kind of correction is required to perform accurate correction unless a processing circuit is shared. Therefore, conventionally, correction light from a correction light source is made to enter each photoelectric conversion element periodically,
The phase shift was corrected using the lighting signal at this time as a reference. However, such a configuration has the disadvantage of complicating the structure.

(Objective of the Invention) It is an object of the present invention to solve these drawbacks and provide a measuring device with a simple configuration and reduced phase shift, that is, measurement error.

(Summary of the Invention) The present invention includes a pair of light sources that irradiate different positions ff1i of an optical member to be tested, and a pair of light sources that are provided in correspondence with each of the light sources, and that emit light from the corresponding light sources to the optical member to be tested. A pair of juxtaposed light receivers that receive light through a member and output a photoelectric conversion signal; and a pair of light receivers that is disposed close to the light receiving surfaces of the pair of light receivers and scans the light receiving surface in a certain direction at a predetermined frequency. An optical measuring device comprising a chopper member and a phase difference measuring device for determining the phase difference of each photoelectric conversion element obtained from the pair of light receivers, and determining the optical characteristics of the optical member to be tested based on the phase difference. The technical point is that the light source and the chopper member form a phase comparator, and the entire measurement system constitutes a phase-locked loop.

(Example) The present invention will be described below based on the example shown in the drawings.

In order to project a pair of bright spots onto the subject's eye E from a direction symmetrical to the optical axis O of the objective lens 4 of the measurement optical system in FIG. In) K is the optical axis 0.0 of the pair of projection optical systems. ,0. is formed.

The projection optical axes O1, 0 both form angles θ with respect to the optical axis 0 of the objective lens, and are arranged so as to intersect at one point on the optical axis O of the objective lens. Optical axis 01.0! The light beams emitted from the upper illumination light sources (such as light emitting diodes) la and lb pass through pinhole plates 2a and 2b and then pass through pinhole plates 2a and 2b.

After the collimator lenses 3a and 3b whose focal plane is on the collimator lens 2b make the beam into a collimated beam, the beam is projected onto the eye Es.

The measurement optical system is separated by a beam splitter 5 into an automatic measurement optical path and an observation optical path for the examiner E.

The front objective lens 4 is common to both optical paths, and in the observation optical path reflected by the beam splitter 5, there is provided a rear objective lens 7 which together with the objective lens 4 constitutes a telescopic system. An aperture rim is provided in a plane where the rear focal plane of the front lens 4 and the front focal plane of the rear lens 7 coincide. The image formed on the focal plate 8 by the objective lens 4.7 is observed by the examiner E through the eyepiece 9.

On the other hand, in the automatic measurement optical path transmitted through the beam splitter 5, there is provided a rear objective lens 11 which forms a telecentric system together with the objective lens 4. An aperture 10 is provided in a plane where the rear focal plane and the front focal plane of the rear lens 11 coincide.

The optical path of the objective lenses 4 and 11 passes through a chopper disk 12 and reaches a pair of juxtaposed photodetectors 13a and 13b. The light receiver 13a receives the emitted light from the light source 1a, and the light receiver 13b
each light receiver 13a so as to receive the light emitted from the light source 1b.
, 13bu light sources 1a, 1b, respectively.

As shown in FIG. 2, the chopper disk 12 has a planar shape in which transparent parts 120 and light shielding parts 121 are formed at equal angular intervals, and the edges 120a and 120b of the transparent parts 120 almost act as light receivers. 13a toward the receiver 13b
It is connected to a motor 14 that rotates at a constant speed at a constant speed to scan the light receiving surfaces of a and tab. The photoelectric conversion signal from the photoreceiver 13a is input to the low-pass filter 16a through the amplifier 15at-. The output terminal of the low pass filter 16& is connected to the voltage controlled oscillator 17a.

Therefore, the drive circuit (driver) 18a of the light source 1a drives the light source 1a using the signal from the voltage controlled oscillator 17&. On the other hand, similarly, the light receiver 13b is connected to an amplifier 15bK, the amplifier 15b is connected to a low-pass filter 16b, the low-pass filter 16b is connected to a voltage-controlled oscillator 17b, and the voltage-controlled oscillator 17b is connected to a drive circuit 18b that drives the light source 1b. It is connected. Voltage controlled oscillator 17a
The output terminal of 917b is connected to the phase comparison circuit 19,
The phase difference obtained by the phase comparison circuit 19 is displayed on the calculation display device 2.
It is converted to a radius of curvature at 0 and displayed.

That is, the light source 1a is driven by the drive circuit 18a to
n (Get+θI), and the chopper disk 1
2, the pinhole image on the photoreceiver 13a is almost KO.
(! O! ) is almost equal to the width of (slit pitch) K(, , cos (ωt+00)・5in (ω is 10). This output is -KiKl(sin (2ω is 10, 10). ,)+5in
(θ.- is blocked and becomes '5in(θ.-〇,) (
However, K o K , / 2 = K'). Here, the free-running oscillation angular frequency of the voltage controlled oscillator 17a is ω. Then, the oscillation angular frequency of the output signal from the voltage controlled oscillator 17a is C4""Jo+6' sin (θ0-01)
becomes. Here, if we set K o K' = K, then ω = ω
o+Ksin(θ0−θl). Here θ. −〇、
=φ, the oscillation angular frequency aθ of light source 1 & is ω
, but becomes t.

On the other hand, the phase change θ given only by the chopper disk 12 is θp=θ. -ω, 1 ・・・・・・・・・・・・・・・
...Equation (2)), and the phase change θ9 given only by the light source IJL is θq=θ, -ω. t・・・・・・・・・Tap・Formula (
3) Therefore, Equation (2) 2 Equation (3) and θ. Since θq=θ, +θp-θ0 = θp-φ due to −〇, =φ, φ=θp-θq ・・・・・・・・・・・・・・・・・・
Equation (4) Now, considering the time change of the phase difference φ, Equation (4)
Here, considering equation (3) t- to θq, and becomes.

is given as −−1△ω φ=gtn() ......Equation (7). Therefore, if the value of K is set large relative to Δω, the phase error can be made almost zero.

The above explanation is based on the well-known phase-locked loop (PLL...---
...-phase Locked Loop), the light source 1a and the chopper disk 12 constitute a phase comparator, thereby forming a phase locked loop with the amplifier 15a, low-pass filter 16a, voltage-controlled oscillator 17a, and drive circuit 18&. be done.

As a result, the phase of the voltage controlled oscillator 17& depends only on the phase of the chopper disk 12, and the phase error of the circuit system *'e
The signal will not be received.

Note that if the diameter of the light spot is smaller than the width of the light-transmitting part, for example, the photoelectric conversion output of the light receiver 131 will be in the form of a rectangular wave. do. Of course, in this case as well, the light source 1a and the chopper disk 12 constitute a PLL phase comparator.

Similarly, the light source 1b, the chopper disk 12, the light receiver 13
The b1 amplifier xsb°, the low-pass filter 16b, the voltage controlled oscillator 17b, and the drive circuit 18b also form a PLLt-.

Therefore, the output signal of the phase difference circuit 19 for determining the phase difference between the output signals of the voltage controlled oscillators 17a and 17b is transmitted to the light receiver 13.
The phase difference corresponding to the distance in the scanning direction by the slit plate 12 of the image of the pinhole 2a #2b generated on a and 13b is shown. The playback display circuit 20 converts the output signal of the phase difference circuit 19 into the radius of curvature of the cornea of the eye to be examined within the paper plane and displays the converted signal.

In the above explanation, to simplify the explanation, the cornea of the eye to be examined is spherical and the radius of curvature is determined only within the plane of the paper. The same applies to the case of a surface. That is, for example, in FIG. 1, the optical axis 0 of the objective lens 4
A pair of target projection optical systems are provided to project a pair of bright spots onto the subject's eye E from a direction symmetrical to the optical axis O of the objective lens in a plane perpendicular to the plane of the paper. The angles that the projection optical axes of the optical systems make with the optical axis 0 of the objective lens are both θ, and the optical axes of the four target projection optical systems are set so that they intersect at one point on the optical axis O of the objective lens. The chopper disk 12 has a planar shape as shown in FIG. That is, the chopper disk 12 has a three-layer structure in the radial direction, and marks for separating the first region and the second region in the circumferential direction are formed on the outer layer. That is, half the circumference is formed by a light shielding part (first region) 122, and the remaining half circumference is formed by a light transmitting part (second region) 123. In the intermediate layer portion 124, light blocking portions and light transmitting portions are formed at equal angular intervals in the circumferential direction by vapor deposition or the like. And inner layer 1
25, in the first region of the chopper disk 12, the chi! defined by the function curve represented by γ= as (B + L). The flange slit is formed by vapor deposition or the like, and the tip flange slit defined by a function curve represented by γ=a·−(e+−) in the second region is formed by vapor deposition or the like. The detailed description of the slit for the tip is as follows.

Among the normal lines of the chopper disk 12, the normal line that makes an angle of 45 degrees with the reference direction (for example, the horizontal direction)! When the light-receiving surface of the light receiver 130 is arranged perpendicular to the optical axis of the optical system forming the automatic measurement optical path so that the surface including Let ψ be the angle at which it intersects the
= a, e tan ((90 - ψ)・(θ 10 engineering π)) and 2, ...... de'), &1 corresponds to the inner diameter of the inner circumference.Here, If the angle ψ is 45 degrees and 135 degrees, then the second
A slit is formed on the glass plate used to form a slit in each region. However, at<rt<at, a, (
r2(al (& corresponds to the outer diameter of the inner peripheral portion)), and each curve of the slit is defined using the boundary between the first region and the second region as a reference for the angular position in polar coordinates.

Then, as shown in FIGS. 4(a) and 4(b) when viewed from the front direction of the chopper disk 12, when the first region crosses over the light receivers 13a-iad by clockwise rotation of the chopper disk 7, is scanned from bottom to top on the light receiving surface, that is, in the Y direction (Fig. 4(a)), and the second area is scanned from the bottom to the top of the light receiving surface.
3d, the light-receiving surface is scanned from left to right, that is, in the X direction perpendicular to the above Y direction, it becomes K (
Figure 4(b)).

The outer layer portion of the collar disk 7 is sandwiched between a light source and a photoelectric conversion element to constitute an area identification device, and therefore the first area and the second area are identified from the photoelectric conversion signal of the photoelectric conversion element.

As in the case of the light receivers 13a and 13b, a phase comparator is constructed between the light sources provided correspondingly for the light receivers 13c and 13d, and each has an amplifier, a low-pass filter, a voltage controlled oscillator, A drive circuit is provided to configure a phase-locked loop CPLL).

Thereby, the phase difference corresponding to the interval in the scanning direction of the tip disk 12 between the pinhole images on each of the light receivers 13a to 13d can be determined in exactly the same manner.

The above is an example in which the present invention is applied to an automatic radius of curvature measurement device, but multiple light beams are made incident on different positions of the test lens, and the optical beam biased by the test lens is measured. It is obvious that the present invention can be similarly used in an automatic refractor whose position is detected by a light receiver. The latter is a device that focuses on the fact that the change in the distance between light images due to refraction corresponds to the refractive power, whereas the former is a device that focuses on the fact that the change in the distance between light images due to reflection corresponds to the radius of curvature.
The only difference in the optical system is whether the optical member to be inspected is viewed through transmission or reflection, and other aspects are substantially the same.

Of course, the present invention can be applied to other than automatic curvature radius measuring devices and automatic refractometers, and any device that measures changes in the distance between optical images may be used.

(Effect of the invention) As described above, according to the present invention, the phase difference can be reduced.

This allows for good waveform shaping. This is equivalent to eliminating the error when the phase difference is used as the measurement chamber, so it not only has the advantage of eliminating the need for phase error correction that was required until now, but also allows the output of the oscillator to be used as the output waveform. Therefore, ideal waveform shaping is possible.

For the above reasons, it is effective for such devices.

[Brief explanation of the drawing]

Fig. 1 is an optical system and electrical block diagram of an automatic radius of curvature measuring device to which the present invention is applied, Fig. 2 is a plan view of the tip disk used in Fig. 1, and Fig. 13 is a diagram of two orthogonal directions. 4(a) and 4(b) are diagrams for explaining the operation of the Chita-tsuba disk of FIG. 3. FIGS. (Explanation of symbols of main parts) 1a, lb...Light source, 12. Old...Chopper disk, 13a to 13d...Receiver, 16a, 16b...Low pass filter, 17&
, 17b... Voltage controlled oscillator, 18a, 18b
・・・・・・Drive circuit.

Claims (1)

[Scope of Claims] A pair of light sources that illuminate different positions of the optical member to be tested; and a pair of light sources that are provided corresponding to each of the light sources, and that emit light from the corresponding light sources through the optical member to be tested. Receives light,
a pair of juxtaposed light receivers that output photoelectric conversion signals; a chopper member disposed close to the light receiving surfaces of the pair of light receivers and scanning the light receiving surface in a fixed direction at a predetermined frequency; a phase difference measuring device for determining the phase difference between each of the photoelectric conversion signals obtained from a light receiver; The apparatus includes: a pair of low-pass filters connected to each of the pair of light receivers; a pair of voltage-controlled oscillators connected to each of the pair of low-pass filters and outputting a frequency signal according to an input voltage; A pair of drive circuits that drive the pair of light sources based on the output signals of the voltage controlled oscillators, and a phase difference measurement circuit that measures the phase difference between the output signals of the pair of voltage controlled oscillators. Optical measuring device.