JP2000009423A - Focusing device for optical instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a collimator device which has a simple structure, can immediately display the measured value of the out-of-focus amount of a lens to be inspected by only placing the lens without requiring the manual operation of a measuring instrument by a worker, and can maintain high resolution accuracy and from which reading errors are eliminated by displaying the shifting amount of the focal point after converting the amount into an electric signal even when the lens to be inspected is not operated. SOLUTION: The illuminating light from a light source section consisting of a reflecting mirror 1 and a light source 2 irradiates a chart 6 through a diffusing plate 3 and a condenser lens 4. A collimator lens 7 is focused on the chart 6 so that the light emitted from the lens 7 may be emitted as if the chart 6 exists at an infinite point. The light is made incident to a lens 8 to be inspected and an AF sensor unit 9 is set up at the image forming position of the light and irradiated with the light. The sensor unit 9 finds the out-of-focus amount of the lens 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus adjusting device for adjusting the focus of an optical device such as an interchangeable lens.

[0002]

2. Description of the Related Art Conventionally, a focus adjusting device for an optical device such as an interchangeable lens has a collimator which emits a parallel beam of light coming from a focal position of an objective lens of a collimator to a sample. An autocollimator device that uses a so-called autocollimation method to measure a sample from the state described above is used. FIG. 3 is a configuration diagram of the autocollimator device. In the figure, reference numeral 1 denotes a reflecting mirror that reflects light from a light source 2, and illumination light from the light source illuminates a chart 6 via a diffusion plate 3 and a condenser lens 4. I do. The light passing through the collimator lens 7 is reflected by the plane mirror M1 through the lens 8 to be inspected, returns to the collimator lens 7 through the lens 8 to be inspected, and forms an image at a position conjugate with the chart 6 by the half mirror M2. The helicoid of the lens 8 to be inspected is adjusted so that the best chart image can be captured by the eyepiece 30. When the lens 8 to be inspected is a zoom lens, the lens 8 to be inspected is set to TELE and the scale of the micro gauge 31 is adjusted to zero (the plane mirror M1 has a structure that can be moved up and down by the micro gauge 31). The helicoid is adjusted to focus the chart image, then the lens 8 to be inspected is set to WIDE, the micro gauge 31 is moved again so that the chart image is in focus, and the plane mirror M1 is moved up and down. The numerical value of 31 is directly read to detect the shift amount of the focal position.

Recently, with the development of solid-state imaging devices and microcomputers, light reflected by a plane mirror M1 is focused on a detector 32 of a solid-state imaging device (such as a CCD image sensor) by a half mirror M3 as shown in FIG. The shift amount of the focal position is electrically detected by the detector 32.

[0004]

Conventionally, however, the microgauge linked to the plane mirror is manually moved to confirm the focus by visual inspection, the scale of the microgauge at that time is directly read, and the measured value is read. Since it is greatly influenced by individual errors to obtain the data, the worker becomes a professional and it is difficult to standardize the work. Further, the work process is complicated. Also, when a solid-state imaging device is used in a device using the auto-collimation method, two half mirrors must be used in the vicinity of the eyepiece, and there is a problem that the structure of the device becomes complicated.

An object of the present invention is to use a phase difference type AF sensor unit for measuring a focal length deviation amount without a manual operation of a measuring device by a simple structure of a collimator device. The displacement of the focal position is displayed immediately by placing the test lens on the target, and the measured value is displayed immediately, enabling high-resolution accuracy.The displacement of the focal position is converted into an electric signal without operating the test lens. It is an object of the present invention to provide a collimator device which eliminates a reading error in order to perform display.

Another object of the present invention is to provide a collimator device which can detect the quality of the resolving power and the presence or absence of flare by measuring the contrast ratio of light passing through the lens to be inspected by using the AF sensor unit.

[0007]

According to the present invention, a phase difference type AF sensor unit is used for measuring the amount of deviation of the focal length of a test lens at the position of a reflecting mirror of an autocollimator device.
High resolution accuracy is represented by digital display, eliminating reading errors and using a phase difference AF sensor unit enables measurement of the focal length deviation amount without operating the lens to be inspected, thus reducing the number of work processes. Do. Also, the present invention
By using a phase difference type AF sensor unit for measuring the contrast ratio, the contrast ratio of the amount of light transmitted through the lens to be measured can be measured to eliminate an error in reading individual differences.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a focus adjusting device according to the present invention. FIG. 1 is a configuration diagram of a main part of a focus adjustment device according to an embodiment of the present invention, and FIG. 2 is a configuration diagram of a phase difference detection AF optical system. In FIG. 1, illumination light from a light source unit including a reflecting mirror 1 and a light source 2 illuminates a chart 6 via a diffusion plate 3 and a condenser lens 4. The collimator lens 7 has its focal length at the position of the chart 6, and the light emitted from the collimator lens 7 has a structure in which the chart is located at infinity. The light is made incident on the lens 8 to be measured, an AF sensor unit 9 is installed at the image forming position, and the light is irradiated to the AF sensor unit 9.

The light source 2 has a stable luminous flux and a stable color temperature. The light beam irradiated to the condenser lens 4 is uniformly irradiated by the diffusion plate 3. In addition, by using the wavelength selected by the color selection filter 5, the influence of the chromatic aberration of the lens 8 to be inspected is removed. Collimator lens 7
Is emitted to the test lens 8, and the test lens 8
Is irradiated on the condenser lens in the AF sensor placed at the image forming point.

Next, the structure inside the AF sensor will be described with reference to FIG. The light beam emitted from the test lens enters the condenser lens 21 of the AF sensor on the imaging surface of the test lens, and the exit pupil of the condenser lens 21 is divided into two right and left parts in the horizontal direction of the optical axis. Re-images two areas on the CCD image sensor 24 in the AF sensor by the aperture masks 22a, 22b, 22c and the separator lenses 23a, 23b in the AF sensor.

The refocused image has a smaller image interval at the front focus and a larger image interval at the rear focus compared to the in-focus condition. The focus position can be detected by detecting the image interval on the CCD image sensor in the AF sensor.

The optical signal formed on the photodiode on the CCD image sensor is electrically converted, and the data obtained by the A / D conversion into 256 gradations by the AF operation circuit is transferred to the RAM, and the correlation calculation is performed.

As a correlation between the area of the reference part and the area of the reference part,

[0014]

[Equation 1]

Is calculated. Let l which minimizes S (l) be l
The region of the reference portion corresponding to min is calculated as the portion having the highest correlation. The amount of deviation of the image interval from the time of focusing is obtained from the value of lmin. Until now, only one pitch unit of the CCD photodiode array has been obtained. For this purpose, a more accurate deviation amount of the image interval is obtained by interpolation calculation. Further, the defocus amount is calculated by multiplying the obtained interpolation value by S × Fw / β. The mount washer amount is calculated by multiplying the defocus amount by the coefficient of the test lens.

Fw is the angle between the principal ray and the optical axis, and the F number Fw = (1/2) × (1 / tan θ) The amount of defocus and the amount on the CCD surface (d and Δl) Δl = d × tan θ = d / 2Fw Secondary image (that is, magnification β of the AF optical system) Δl ′ = β × l Therefore, = (β × d) / 2F where P is the width of one bit of the CCD image and P≡2Δl ′ = (β × d) / F That is, θ is the angle between the principal ray of the light beam and the optical axis. If the F number is Fw, Fw = 1 / (2 × sin θ) 1) * The F number is the maximum focusing angle Assuming that the focus indicating the maximum light receiving angle is out of focus, it is considered that images are formed at positions separated from each other by Δl on the film equivalent surface as compared with when focusing. Here, the deviation amount Δl of the optical axis is represented by Δl = dtan θ ≒ d / (2 × F).

Next, consider the image on the CCD. This is because the images formed on the film equivalent surface are separated by the separator lenses 23a and 23a.
It is considered that the image was re-imaged by b. Therefore, the moving amount 2Δ of the image on the CCD generated for the front focus by d.
The relationship between l ′ and d is d = (Fw × 2Δl ′) / β, assuming that the magnification of the separator lens is β, Δl ′ = β × Δl.

This equation shows that the change of the image interval on the CCD is proportional to the magnification β and the defocus amount d, and is inversely proportional to the F-number Fw.

Further, it is also shown that the direction of the change of the image interval becomes narrower at the front focus and wider at the rear focus. Here, assuming that the amount of movement of the image on the CCD is P in CCD pitch units and that the pitch of one CCD is s, d = (s × Fw × P) / β.

The amount of displacement of the focal position of the lens to be measured is measured by such an operation, and the amount of space washer is calculated by multiplying the constant by a constant.

The method for measuring the amount of deviation is as follows. Place the test lens on the mount adapter. 2. On the TELE side, the shift amount is adjusted within the specified range by moving the focal length adjustment unit of the test lens in accordance with the INF position. 3. Next, the zoom ring of the lens to be inspected is set to the WIDE side, the shift amount is measured, and the shift amount is multiplied by a constant to calculate the space washer amount.

As described above, the amount of deviation can be easily measured, and the operation can be performed mechanically, so that there is no individual difference among operators.

Further, in order to determine the deterioration of the contrast ratio due to the poor resolving power of the test lens and the deterioration of the contrast ratio due to flare, the contrast ratio of the test lens is detected by using the data of the CCD image sensor 24 shown in FIG. I do.

The CCD image sensor 24 in the AF sensor is composed of a light receiving element, a register, etc., converts an optical signal transmitted through the lens 8 to be detected into an electric signal, and converts the photoelectrically converted data into an AD signal by the AF operation circuit unit 10. The data is converted into 256 gradations.
The upper limit value of the bright portion of the chart and the lower limit value of the dark portion are conditionally determined, and the data is binarized. The contrast ratio between the bright portion and the dark portion of the chart is changed due to poor resolution of the lens 8 to be inspected and flare. Since the resolution is poor, the presence or absence of flare is compared with the reference value of the contrast ratio to determine the lens 8 to be inspected.
Can be determined.

[0025]

As described above, according to the present invention,
The phase difference type A is set at the position of the plane mirror of the autocollimator.
Equipped with a detector consisting of an F sensor unit, the structure of the device can be simplified, and by using a phase difference AF sensor unit to measure the amount of deviation of the focal position, high-resolution accuracy can be digitally displayed. And reading errors can be eliminated. Further, by using the phase difference type AF sensor unit, the amount of deviation of the focal position can be measured without operating the lens to be inspected, thereby reducing the number of working steps. In addition, by using an AF sensor unit of the phase difference method, the amount of light transmitted through the lens to be measured is measured, the contrast ratio is measured, the resolution of the lens to be measured is poor, the presence or absence of flare is determined, and the reading error of the individual difference is determined. Can be eliminated.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a main configuration of a focus adjustment device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating a main configuration of an AF sensor unit according to the embodiment of the present invention.

FIG. 3 is a configuration diagram of an autocollimator device.

FIG. 4 is a configuration diagram of an autocollimator device using a detector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reflecting mirror 2 Light source 3 Diffusing plate 4 Condenser lens 5 Color selection filter 6 Chart 7 Collimator lens 8 Test lens 9 AF sensor unit 10 AF operation circuit 11 Control CPU circuit

(Equation 1)

Claims (2)

[Claims] 1. A focus adjustment device for adjusting the focus of a lens to be inspected, wherein a phase difference type AF sensor unit is used for a detector for detecting a shift amount of a focal position, and a focus adjustment device is provided between the collimator lens and the detector. A focus adjustment device for an optical device, wherein a lens to be inspected is arranged. 2. The focus adjusting device for an optical device according to claim 1, wherein a phase difference type AF sensor unit of a detector for detecting a shift amount of a focal position is also used as an image plane illuminance detecting means. .