JPH05107057A - Focusing apparatus - Google Patents

Abstract

PURPOSE:To provide a focusing apparatus which places the focus quickly and accurately on an object. CONSTITUTION:In a focusing apparatus, a bundle of rays for measurement is applied to an object through an objective lens 5. A reflected light from the object is passed through a pinhole being vibrated and is applied to a light- sensing element 15. On the occasion, the quantity of light sensed by the light- sensing element 15 changes according to a distance between the objective lens 5 and the object 2 and the position of the pinhole. CPU detects a slippage of the focus from the quantity of the light sensed by the light-sensing element 15 and the position of the pinhole, and in accordance with the result of the detection, a motor 22 operates to alter the distance between the object 2 and the objective lens 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focusing device, and more particularly to a focusing device for focusing on an object by an optical instrument for observing or imaging the surface shape of the object.

[0002]

2. Description of the Related Art Conventionally, focusing devices used in optical instruments such as microscopes and image pickup devices irradiate an object with focusing light (light flux for measurement) when focusing on the object. Focusing was performed using reflected light. For example, as shown in FIG. 7, a light beam 80 is applied to an object 84 through an objective lens 82, the reflected light is reflected by a beam splitter 86, passes through a pinhole 88, and is applied to a light receiving element 90. is there. In that configuration, the amount of light received by the light receiving element 90 changes as shown in FIG. 8 by scanning the objective lens 82 up and down in the direction of the arrow. In this case, the position where the amount of light received is maximum is the object of the objective lens 82. The focus is on the object 84.

As a result, the focusing device returns the objective lens to the position at which the maximum amount of received light of the received light amount of the light receiving element 90 obtained by moving the objective lens 82 within a predetermined range is detected. The action was taking place.

[0004]

However, in the focusing device as described above, the objective lens is moved once within a predetermined range and then moved again to the in-focus position. It took a very long time to make the match.

Further, as shown in FIG. 8, since the change in the output signal of the light receiving element near the in-focus position is small, the in-focus position accuracy is poor.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a focusing device capable of performing a focusing operation quickly and accurately.

[0007]

In order to achieve this object, a focusing device of the present invention comprises a light source for irradiating an object with a measuring light flux with an objective lens of an optical instrument as an optical axis.
Optical path restricting means for limiting the optical path of reflected light from the object, vibrating means for vibrating the optical path restricting means in order to change the amount of reflected light from the object, and an optical path vibrated by the vibrating means. Position detecting means for detecting the position of the regulating means, a light receiving element for receiving the reflected light that has passed through the optical path regulating means, and a focus according to the detection result of the position detector and the amount of light received by the irradiated light receiving element. A defocus detecting means for calculating a position deviation and a distance changing means for changing a distance between the object and the objective lens according to a detection result of the defocus detecting means.

[0008]

The focusing device of the present invention having the above construction is
An object is irradiated with a measuring light beam through an objective lens.
Then, the reflected light from the object passes through the optical path restricting means that restricts the optical path while vibrating, and is applied to the light receiving element. At this time, the output of the light receiving element changes depending on the distance between the objective lens and the object and the position of the optical path regulating means. Then, the focus shift detecting means calculates the focus shift based on the output of the light receiving element and the output of the position detector of the optical path restricting means, and the distance changing means calculates the distance between the object and the objective lens according to the calculation result. Works to change.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the focusing device of the present invention will be described below.

2 and 3 are views showing a shape measuring apparatus provided with the focusing device of the present invention.

The shape measuring device comprises an optical unit 1 and a focusing control device 40.

The optical unit 1 picks up an image of the surface of the work 2 placed on the stage 3.
It is provided so as to be slidable in the vertical direction (the direction of the arrow in FIG. 2). An objective lens 5 is detachably attached to the optical unit 1 at a position facing the stage 3.
Above the objective lens 5, a CCD camera 6 is arranged in alignment with the axis of the objective lens 5. The optical unit 1 is provided with the following optical focusing mechanism for focusing the CCD camera 6.

The semiconductor laser 8 is a light source for focusing, and the light flux emitted from the semiconductor laser 8 is corrected into parallel light by the collimator lens 9 and then corrected into a circular sectional shape by the correction prism 9. After passing through the lens 11 and the beam splitter 13, the light flux is reflected by the dichroic mirror 12, passes through the objective lens 5, and is irradiated onto the surface of the work 2. The dichroic mirror 12 has spectroscopic characteristics in which reflected light and transmitted light are different from each other. When the light flux from the objective lens is visible light, it is transmitted, and when it is infrared light, it is reflected.

The light beam reflected by the surface of the work 2 passes through the objective lens 5 and then is reflected by the dichroic mirror 12 toward the beam splitter 13. The light beam reflected from the dichroic mirror 12 is reflected by the beam splitter 13. In the optical path of the reflected light flux, the pinhole 17 and the pinhole vibrating mechanism 1 as the optical path regulating means of the present invention are provided.
6, a pinhole position detector 18 and a light receiving element 15 are provided. The pinhole 17 is a very thin plate with a small hole.

When the pinhole 17 is not vibrating, the luminous flux reflected from the beam splitter 13 passes through the pinhole 17 in a focused state and the amount of light applied to the light receiving element 15 is maximized and the focus is deviated. When the focus is on, the light is blocked by the pinhole 17 and the light receiving element 15 is irradiated with a smaller amount of light than that at the time of focusing. The relationship between the position of the optical unit 1 and the output of the light receiving element 15 is as shown in FIG. When the pinhole 17 is vibrating, the output of the light receiving element 15 also changes according to the position of the optical unit 1 and the position of the pinhole 17.
Then, the output C corresponding to the defocus is calculated from the following formula.

[0016]

[Equation 1]

The relationship between the position of the optical unit 1 and the output C corresponding to the defocus is as shown in FIG.

The mechanism for moving the position of the optical unit 1 is composed of a frame 70, a motor 22 and a ball screw 23. That is, it is a mechanism for transmitting the rotation of the motor 22 to the ball screw 23 to drive the optical unit 1 itself in the up-down direction. Therefore, the rotation of the motor 22 can change the distance between the stage 3 and the optical unit 1, that is, the distance between the surface of the work 2 and the objective lens 5 for focusing.

On the side surface of the optical unit 1, an optical linear encoder 21 for detecting the vertical position of the optical unit 1 is provided.
Are arranged. The optical linear encoder 21 is a known linear position sensor, and includes a main scale 21A fixed to the frame 70 and a sensor head 21B fixed to the side surface of the optical unit 1 and having a light source, a light receiving element, an index scale and the like. ing. Then, by detecting which part of the main scale 21A fixed to the frame 70 the index scale of the sensor head 21B that moves up and down together with the optical unit 1 is detected, the vertical position of the optical unit 1 is detected. It

Next, the focusing control device 40 will be described with reference to FIG. The focusing control device 40 includes an electronic control device 50 including a known CPU 51, ROM 52, RAM 53, input / output interface 54, bus 55, and the like, and a motor driver 61 that drives the motor 22.
And an LCD 63 that displays 7-segment using liquid crystal
An LCD driver 62 for driving the LCD 63, an operation switch 64, and the like. The optical linear encoder 21, the light receiving element 15, and the position detector 18 for the pinhole 7 are connected to the input / output interface 54.

Next, the focusing operation of the thus-configured measuring apparatus will be described with reference to FIGS. 4 and 6.

As described above, the light beam emitted from the light source is reflected on the surface of the work 2 and then irradiates the light receiving element 15. Then, by operating the operation switch section 64, the focus control routine of FIG. 4 is started.

First, the output signal A1 of the light receiving element 15 and the output signal B1 of the position detector 18 of the pinhole 17 are AD converted at the input / output interface 54, and then C
It is read by the PU 51 (S1).

The CPU 51 outputs the output C corresponding to the defocus.
1 is calculated from the output signal A1 of the light receiving element 15 and the output signal B1 of the position detector 18 of the pinhole 17 (S2).
Then, the output C1 of the light receiving element corresponding to the defocus is changed to C1.
The CPU 51 determines whether or not = 0 (S3).
Then, as shown in FIG. 6, when C1 = 0 (S3: YE
In S), the optical unit 1 is in the in-focus position, which is displayed on the LCD 63, and the focusing is completed.

When C1 = 0 is not satisfied (S3: NO), C
The CPU 51 determines whether the value of 1 is positive or negative (S4). The drive direction of the motor is determined based on the result of the determination, and the motor is rotated until C1 = 0. That is, when the value of C1 is positive, the motor 22 is rotated in the direction in which the optical unit 1 moves upward, and when the value of C1 is negative, in the direction in which the optical unit 1 moves downward. The motor 22 is rotated. (S5 / S6). afterwards,
This is displayed on the LCD 63, and focusing is completed.

[0026]

As is apparent from the above description, the focusing device of the present invention detects the defocus from the position of the pinhole that regulates the light amount of the reflected light from the object and the optical path of the reflected light. Therefore, it is not necessary to move the objective lens within a predetermined range to detect the in-focus position by detecting all the light amount during that time, and it is possible to achieve the excellent effect that the focusing operation can be performed quickly and accurately.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a focusing device of the present invention.

FIG. 2 is a schematic configuration diagram of a mechanical portion of a shape measuring apparatus including a focusing device of the present invention.

FIG. 3 is a schematic configuration diagram of a control portion of a shape measuring apparatus provided with a focusing device of the present invention.

FIG. 4 is a flowchart showing a focus control routine of the present invention.

FIG. 5 is a diagram illustrating a defocus detection method according to the present invention.

FIG. 6 is a diagram illustrating a defocus detection method according to the present invention.

FIG. 7 is a diagram illustrating a conventional defocus detection method.

FIG. 8 is a diagram illustrating a conventional defocus detection method.

[Explanation of symbols]

 1 Optical Unit 2 Work 3 Stage 5 Objective Lens 8 Semiconductor Laser 15 Photoreceptor 16 Vibration Mechanism 17 Pinhole 18 Position Detector 22 Motor 40 Focusing Control Device 50 Electronic Control Device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiro Ito 15-1 Naesehiro-cho, Mizuho-ku, Nagoya-shi Brother Industrial Co., Ltd. Within the corporation

Claims (1)

[Claims] 1. A focusing device for focusing on an object of an optical device for observing or imaging a surface shape of the object, wherein a measuring light beam is applied to the object with an objective lens of the optical device as an optical axis. A light source that irradiates a bundle, an optical path restricting unit that restricts an optical path of reflected light from the target object, and a vibrating unit that vibrates the optical path restricting unit to change the light amount of the reflected light from the target object, Position detecting means for detecting the position of the optical path regulating means vibrated by the vibrating means, a light receiving element for receiving the reflected light that has passed through the optical path regulating means, and a detection result of the position detecting means and the amount of light received by the light receiving element. Focus shift detecting means for calculating the shift of the focus position in accordance therewith, and separation changing means for changing the distance between the object and the objective lens according to the detection result of the focus shift detecting means. Focusing apparatus characterized by comprising.