JPH0820334B2 - Automatic lens meter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a lens meter for measuring a spectacle lens or a contact lens.

[Conventional technology]

When measuring a lens with a manual lens meter, the relative position on the optical axis of the optical system including the lens to be inspected is changed, or the distance of the light source optical system is changed to trace the image focus plane, and the focus plane is Based on the relationship between the moving distance of the obtained image and the light-transmitting optical system, the focal length was obtained by observing with a naked eye or a visual device. However, the visual determination of the focus position has a drawback that a visual error is likely to occur due to an individual difference.

Therefore, in order to solve the drawbacks of the manual lens meter, Japanese Patent Application No. 48-32994 and Japanese Patent Application Laid-Open No. 60-17335 are disclosed as automatic lens meters. The former is an imaging optical system in which the lens to be inspected is fixed by aligning the optical centers on the optical axes of the light-transmitting collimator and the light-receiving collimator, and the photoelectric converter is arranged on the focal plane on the extension line of the optical axis, and the photoelectric converter. An electric circuit that sorts out the luminance signal of the target image decomposed by the search line and counts the position where the time width area of the luminance electric signal is minimized in the forward and backward movements of the light source optical system and in synchronization with this electric circuit. It is characterized by a circuit that automatically controls the reciprocal drive of the light source optical system by a pulse motor and its drive signal generator, and converts the position where the target image becomes the minimum area into a diopter display signal. .

On the other hand, the latter is an automatic lens meter including the former,
Since it is necessary to provide a means for detecting the best position and a mechanism for moving the target, as an improvement thereof, by processing the signal on the image sensor arranged on the focal plane of the imaging lens without moving the slit pattern, The refractive index of the lens, the axial angle, and the prism amount are measured.

[Problems to be solved by the invention]

However, in the above-mentioned JP-A-60-17335, the measuring light is divided into two behind the light receiving objective lens, and the deflection of the measuring light by the test lens is detected by two image sensors.
The calculation processing is performed based on the data to calculate the refracting power, but the measurement light that has passed through the lens to be measured is divided into two and separated into the X direction and the Y direction, and the signal is sent to the image sensor. Therefore, the optical signal sent to the image sensor is less than half of the original signal, so special electrical processing is required to improve the S / N ratio, and the electric circuit is complicated and expensive. Will be things.

Further, since the beam splitter for splitting into two and the two image sensors have to be separately arranged, it is inevitable that the optical path, the two image sensors and their mounting parts are complicated and expensive.

The present invention has been made to eliminate such problems, and an object thereof is to provide an automatic lens meter having a simpler structure.

[Means for solving problems]

The present invention has been made to achieve such an object, and uses the Prentice formula to automatically measure the optical characteristics of a test lens from the deviation amount and direction of a pattern image formed on an image sensor. A lens meter,
The lens meter includes four light sources arranged at the respective vertex positions of a square centered on the optical axis, and a light-transmitting lens having the center of the four light sources arranged at the respective vertex positions of the square as a focus. A measuring table on which a lens is mounted, a collimator lens for imaging each of the four light sources on a test lens mounted on the measuring table, and a light receiving objective for imaging light passing through the test lens on an image sensor. A lens, a single image sensor for detecting the position of the pattern image at a position conjugate with the origin position of the pattern image through the light receiving objective lens, and at least two linear slit portions that are not parallel to each other. When the image is illuminated by any one of the four light sources through the light-sending lens, the linear slit portions in the image sensor area do not intersect each other and the image is emitted. An automatic lens meter is provided, which is equipped with an optical system that is formed with a slit-shaped pattern that forms an image image that intersects with a sensor at at least two points and that is movable in the optical axis direction. Is.

〔Example〕

 Next, examples of the present invention will be described.

FIG. 1a is a system block diagram of a lens meter 1 according to an embodiment of the present invention. First, from the optical system 2,
Reference numeral 3 is four ultra-bright light emitting diodes (LEDs), which are used as the light source of the lens meter 1. These four LEDs 3 need to be arranged at equal intervals as shown in FIG. 1b in order to simplify the later-described calculation. 4 is a light-sending lens that collimates the light emitted from each LED. That is, the LED 3 is arranged at the focal position of the light transmitting lens 4.
Reference numeral 5 denotes a slit-shaped pattern which forms an N-shaped slit as shown in FIG. 1c and is movably arranged between the light transmitting lens 4 and a collimator lens 6 described later. 6 is a collimator lens, which serves two functions. One is to create a light source image on the lens 7 to be inspected, and the other is to collimate the light beam forming the image image of the slit-shaped pattern 5 into a parallel light beam in cooperation with the lens 7 to be inspected. 8
Is a measuring table, and is adjusted so that the lens 7 to be inspected is set right above the light source image. Reference numeral 9 denotes an objective lens, which forms an image image of the slit-shaped pattern 5 made into a parallel light flux by the collimator lens 6 and the lens 7 under test. An image sensor (CCD) 10 is arranged at the focal position of the objective lens 9 and detects the position of the pattern 5 as described later.

Therefore, the light emitted from the light source composed of four LEDs 3 passes through the light-sending lens 4, illuminates the slit-shaped pattern 5, passes through the collimator lens 6, and enters the lens 7 to be inspected, and then the objective lens. Although it reaches the image sensor 10 via 9, the position of the light source and the position of the back surface of the lens 7 to be inspected are optically conjugate with each other. That is, four light sources are once focused on the back surface of the lens to be inspected (see FIG. 2). Here, the slit-shaped pattern 5 is maintained in a substantially conjugate relationship with the position of the image sensor 10. That is, the slit-shaped pattern 7 is made to correspond to the equivalent spherical surface value Se of the lens to be inspected by the pulse motor in the optical axis direction.
The measurement is carried out while maintaining the conjugate relationship between the slit-shaped pattern 5 and the image sensor 10 by moving the servo control by 5a.

In addition, in connection with these optical systems, the AC input is a DC processing system as an electrical processing system that performs control, detection, and arithmetic processing.
Power supply unit 11, CPU12, ROM that converts to input and supplies to control unit 30
13, control board 15 consisting of RAM 14, clock generation circuit 16 and C
A signal processing circuit 24 including a CD driving circuit 17, a peak hold circuit 18, an auto gain circuit 19, a differentiating circuit 20, a latch circuit 21, a counter circuit 22, and an address setting / writing pulse creating circuit 23, a display driving circuit 25, a light source ( LED) drive circuit 2
6, pulse motor drive circuit 27, numerical operation circuit 28, control unit 30 composed of each circuit of printer drive circuit 29, display unit 31 for performing LED display or monitor display, exposed as an operation panel on the main body and operated There is an operation switch section 32. The electric system of the control unit 30 will be described later.

Next, the four light spots on the lens to be inspected are (Xi, Yi), i =
1 to 4, and with each prism amount, the spherical value S, the astigmatic power C, and the axial direction (AX
= Θ), and a method of calculating the amount of eccentricity with respect to the measurement optical axis (prism value as the lens to be measured) will be described.

Here, when the prism quantity at each point of D _{1 to} D ₄ is decomposed into a spherical surface and a cylindrical surface, from FIG. 5, the spherical spherical surface PS _i (P _sxi , P _sYi ) is PRENTIC.
From E formula (prism value = eccentricity (mm) x D / 10) That is, Here, i = 1 to 4, X _i and Y _i are the center coordinates of each point (pattern image).

Judging from FIG. 6, the prism P _ci (P _xci , P _cYi ) formed by a cylinder is That is, the X direction is And in the Y direction, The prism composition in the X direction is The prism composition in the Y direction is The prism combined value in the X and Y directions is proportional to the amount of movement on the sensor. That is, when the proportional constant is k and the prism amount is expressed as the movement amount on the sensor, P _xi = kx _i P _Yi = ky _i where x _i and y _i are the movement amounts on the sensor.

Prism synthesis in X direction Prism synthesis in Y direction Here, when each point (i = 1 to 4) is substituted to create an equation, From equation (2), Becomes

From equation (1), From equation (2), Each pitch distance of the light source image on the lens to be inspected is determined as shown in FIG. 7, and OP (optical center of the lens to be inspected) is set to (0,
It is as follows when expressed by the coordinates of 0).

X ₁ −X ₃ = K Y ₁ −Y ₃ = 0 X ₂ −X ₄ = 0 Y ₂ −Y ₄ = K Therefore, using the above equation, (3), (4),
Equations (5) and (6) are simplified as follows.

According to the equations (7), (8), (9), and (10), (11),
(12) and (13) are obtained.

From equations (11), (12), and (13), the spherical power S, the astigmatic power C, and the axial power Ax can be obtained as follows.

Ax = 45 ° (where β = 0, γ> 0) Ax = 135 ° (where β = 0, γ <0) Also, determine the prism value as the amount of eccentricity in the lens layout of the lens under test as follows. You can If the x component and the y component of the value are Px and Py, respectively, σ = 90 ° (Px = 0, Py> 0) σ = 270 ° (Px = 0, Py <0) Therefore, the optical characteristics of the test lens can be calculated from the four light fluxes that pass over the test lens.

Next, a method of obtaining the center coordinates (Xi, Yi) of the pattern image by using one line sensor as an image sensor will be described. In FIG. 2, the four light source images condensed on the lens to be inspected are D1, D2, D3, and D4, respectively.

Fig. 3a is a pattern image when one LED lights up, and the horizontal line means the sensor.

As for the data, when D1 is lit, there are 6 data from P1 to P6 as shown in FIG. 3a. Similarly, when D2, D3, and D4 are turned on, there are 6 data items each.

When the X and Y coordinates of the center of the N-shaped pattern image are obtained by using these 6 data, the following formula is obtained (3b
See figure).

In the above formula, x indicates which bit of the sensor has the center in the horizontal direction, and y indicates the center of the sensor in the vertical direction when the sensor is replaced with + on the top and − on the sensor. Is there.

If the coordinates when the lens to be inspected is not inserted are (X0, Y0) and the coordinates when the lens to be inspected is (X1, Y1), X1-X0 is the X axis and Y1-Y0 is the Y axis. If a new coordinate system is drawn, it will represent the prism amount (deviation amount) itself at the measurement point of the lens under test.

However, (11), (12) and
The formula (13) and the formula of the prism amount are as follows.

Here, α, β, and γ can be obtained by substituting them into the formulas of S (spherical power), C (astigmatic power), and Ax (axial power) described above. Therefore, the optical characteristics of the lens to be inspected can be detected from one line sensor and the pattern image. Thus, theoretically, as described above, it is possible to detect with the configuration (one line sensor, four point light sources, pattern) according to the present invention. As you can see, the pattern is moved by servo control.

Explaining the movement of the pattern, there are two reasons for moving the pattern. One is the accuracy problem, and the other is the effective length of the sensor and the prism amount. In terms of accuracy, the light source image condensed on the test lens has at least an area, so when the test lens becomes strong, the refraction action causes blurring of the pattern image on the sensor. That is, the waveform of the signal on the sensor does not become sharp, and a state occurs in which it is difficult to capture the signal. Therefore, in order to make up for the drawback, a pattern is moved by servo control using a pulse motor,
Sphere correction was performed. The movement of the pattern is optically designed in advance so that the movement amount (distance) and the refractive power (D) have a certain regularity. Therefore, one of the pulse motor
Since the amount of movement of the pattern can be controlled by the pulse, the constant relational expressions of these three are established.

Actually, a certain amount of pattern movement is determined in advance based on the optical characteristic data detected while the pattern is stationary, and movement is performed based on that. It suffices to know how much D is currently corrected in the optical characteristic data obtained by detecting the pattern image after the movement. In this way, the movement of the pattern is used as a means for reducing the blurring of the pattern image on the sensor so that each of the six pieces of data can be more accurately taken by the sensor.

As for the problems related to the effective length of the sensor and the prism amount, generally, the measurement range of the lens meter is +/− 25D,
Up to 5 prisms can be measured.

In this embodiment, as shown in FIG. 8, when the measurement point pitch is 4 mm, the deviation amount from PO is 2 mm, and the lens to be measured is a 25D spherical lens, the prism amount at the measurement point is 5 prisms. Become. In other words, if the pattern is not moved, the pattern image moves up to 10 prisms, so the sensor length is needed to cover it. P _MAX = 5 ^Δ +5 ^Δ = 10 ^{Δ If the} pattern is moved in advance by the spherical power based on the detection data before moving the pattern, the pattern image will become one, and the maximum 5 prisms will move, so only the sensor length corresponding to that Will be good. That is, if you move the pattern,
The sensor can be shortened accordingly, and the design becomes compact.

For the above reasons, the pattern is moved, but the formula for obtaining the spherical power S at that time is slightly different from the formula for explaining the principle of 2.

(However, SE is the spherical power for moving the pattern.) SE = (spherical power for one pulse of the pulse motor) × (the number of pulses sent to the pulse motor) In the shape of the slit of the pattern, N is used in this embodiment.
Although the character shape is used, in the relation of one line sensor, if the line direction on the line sensor is x and the direction perpendicular to x is y, the position of the image on the sensor (center)
Has at least two linear slit portions that are not parallel to each other in order to detect the x component and the y component, and when illuminated by any of the four light sources through the light transmitting lens described above, An image image is formed in which the linear slit portions do not intersect with each other and intersect with the image sensor at at least two places, and the intersecting portions are defined as N ₁ and N _2, and the center X of the figure of the preset pattern is formed. The distance from N ₁ to N _3, where the coordinates are N _3.
If Z ₁ and the distance Z ₂ from N ₂ to N _{3 make the} line sensor y
Assuming scanning in the axial direction (actually this is the opposite because the pattern moves) and Z ₁ ≠ Z ₂ and Z ₁ and Z ₂ are proportional to the movement in the y direction. The x-axis component and the y-axis component are obtained from the distance ratio, and it is possible to detect which position of the slit figure is being scanned by this sensor. Further, the position of the center of this slit can be known from this detection position. be able to. This slit shape is preferably a part of N-shaped and / or V-shaped slits or a modified shape as shown in, for example, FIGS. 9a to 9j.

Next, the signal processing of the electric system of the control unit 30 according to the present invention will be described with reference to FIG.

In the signal processing circuit 24, the pulse from the clock generation circuit 16 is divided in the counter to generate the LED drive signal 33, and L
Four LED light sources 30 (D ₁ , D through the ED (light source) drive circuit 24
₂ , D ₃ , D ₄ ) are alternately lit every 20 ms. That is,
Reference pulse generated by the clock generation circuit 16 (800KH
z) causes the counter circuit 22 and the CCD drive circuit 17 to operate, so that the lighting of the LED 3 and the cycle with other circuits are taken. The LED drive circuit 26 causes the four LEDs 3 from D ₁ to D ₄ to The operation of turning on for 20 ms and turning off for 60 ms is repeated in a time series.

The light from four LEDs3 illuminates the pattern, then CCD10
Reach The light that reaches the CCD 10 is divided into four in time series. That is, D ₁ signal, D ₂ signal, D ₃ signal and
This is a signal for D ₄ .

The output signal from the CCD10 passes through the CCD drive circuit 17 and is amplified.
After reaching 34, the peak hold circuit 18 and the auto gain circuit 19 are reached. The peak hold circuit 18 holds the dummy signal (optical signal for 5 ms) when D _{1 is} lit and outputs it to the auto gain circuit 19. When the light quantity is small, the peak value is small, and when the light quantity is large, the peak value is large.

By the dummy signal input to the auto gain circuit 19,
Controls the amplification factor of the auto gain circuit 19. When the light amount is small, the amplification factor is large, and when the light amount is large, the amplification factor is small. The output of the auto gain circuit 19 becomes a signal with a constant amplitude regardless of the light intensity, and the comparator
Entered in 35. The output from the comparator 35 is a differentiation circuit.
It is input to 20, and a pulse is generated every time the change in the light amount exceeds a certain value. The pulse from the differentiating circuit 20 is input to the address setting / writing pulse creating circuit 23, and is combined with the value of the counter to be an address address. Further, it becomes a write pulse and is input to the RAM 14.

The position of the CCD 10 where the light hits is latched by the 21 pulse input to the latch circuit, and the latch circuit 21 causes the RAM 14
Output to D ₁ to D ₄ is in RAM14 by the process
The illuminated position on the CCD when lit is memorized regularly.

The CPU 12 can calculate S, C, and Ax by reading the contents of the RAM 14 when necessary and appropriately processing the data 9, and the data for driving the position of the pulse motor 5a to an appropriate place. Can be created.

The data string thus written in the RAM 19 is read out by the CPU 12, the ROM 13, and the RAM 14a when necessary, and the numerical calculation circuit 28 calculates each item of the spectacle lens. The calculation result can be displayed on the CRT display via the display drive circuit 25 or printed by the printer via the printer drive circuit as desired.

〔The invention's effect〕

Since the present invention simplifies the configuration of the image sensor, no special electric processing is required, and the electric circuit is simple, so that a simpler lens meter can be provided and the cost effect is great. .

[Brief description of drawings]

FIG. 1a is a system block diagram of a lens meter according to an embodiment, FIG. 1b is a front view of a light source, FIG. 1c is a front view of a slit pattern, and FIG. 2 is a light source image formed on a lens to be inspected. Fig. 3a shows the pattern image formed on the sensor, Fig. 3b shows the pattern image of Fig. 3a in the coordinate system, and Figs. 4a and 4b show the signal from the sensor. FIG. 5 shows the state of the prism, FIG. 5 is an analysis diagram of a prism using a spherical surface, FIG. 6 is an analysis diagram of a prism using astigmatism, and FIGS. 7 and 8 are
FIG. 9a is a diagram showing the pitch of the light source image formed on the lens under test.
Figure, Figure 9b, Figure 9c, Figure 9d, Figure 9e, Figure 9f, Figure 9g
FIG. 9, FIG. 9h, FIG. 9i, and FIG. 9j are diagrams showing modified examples of the pattern, and FIG. 10 is an electric circuit diagram according to the embodiment. 1 ... Lens meter, 3 ... LED, 4 ... Sending lens,
5 ... Slit pattern, 5a ... Pulse motor, 6 ...
… Collimator lens, 7 …… Test lens, 8 …… Measuring table, 9 …… Objective lens, 10 …… Image sensor, 30 ……
Control unit, 31 ... Display unit

Claims (1)

[Claims] 1. An automatic lens meter for measuring optical characteristics of a lens to be tested from a deviation amount and a direction of a pattern image formed on an image sensor by using Prentice's formula. Four light sources arranged at the respective vertex positions of a square centered on the optical axis, a light-sending lens having the center of the four light sources arranged at the respective vertex positions of the square as a focus, and a test lens are mounted. A measuring table; a collimator lens for forming an image of each of the four light sources on a test lens mounted on the measuring table; a light receiving objective lens for forming an image of light passing through the test lens on an image sensor; One image sensor for detecting the position of the pattern image at a position conjugate with the origin position of the pattern image through the objective lens, and at least two linear slits that are not parallel to each other. At least two locations in the image sensor area without intersecting the linear slit portions when illuminated by any one of the four light sources through the light transmitting lens. An automatic lens meter, comprising: an optical system configured by a slit-shaped pattern that forms an image image intersecting with each other and is movable in the optical axis direction.