JPH07190726A - Coaxial lighting device and its method - Google Patents

Abstract

PURPOSE:To make uniform the distribution of illumination intensity in a camera photographing surface for a photographed object by a coaxial lighting device provided with a half mirror to be disposed in front of a lens of a camera. CONSTITUTION:When light is irradiated from a surface light source where emitting strength is controlled every coaxially disposed light emitting diode 47 while the center axis of the surface light source is perpendicularly intersected with the optical axis of a camera 10, light passes through a diffusion plate 43 which is disposed while being faced to the surface light source, it is reflected by a half mirror 41 which is disposed while being inclined by 45 deg. with respect to the optical axis of the camera 10, and it is irradiated over a photographed surface, so that an image can thereby be picked up over a camera photographing surface while illumination intensity is uniformly distributed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coaxial lighting device mainly used for recognizing semiconductor elements.

[0002]

2. Description of the Related Art A semiconductor element 2 separated from an adhesive sheet 1 is picked up by a push-up pin and a suction collet, taken out from the adhesive sheet 1, and mounted on a lead frame or the like. Camera 1 for detecting the position of semiconductor element 2
0 is arranged, and a coaxial illumination device 20 for illuminating the semiconductor element 2 with sufficient illuminance is incorporated in the camera 10. The coaxial lighting device 20 has a structure as shown in FIG.
Is a lens, 21 is a mirror box 2 in front of the lens 12.
The half mirror 21 is supported via 2 and is supported so as to be inclined by 45 degrees with respect to the optical axis of the lens 12.

Reference numeral 23 denotes a lamp house which is arranged beside the half mirror 21 in a state of being connected to the mirror box 22. The lamp house 23 includes a lamp 24 arranged substantially in the center of the lamp house 23, a reflecting mirror 25 arranged behind the lamp 24, a convex lens 26 arranged in front of the lamp 24, and a half mirror 21 in front of the lamp house 23.
And a diffusion plate 27 arranged on the surface facing the. Then, the light emitted from the lamp 24 is sent to the half mirror 21 via the lens 26 and the diffusion plate 27, and is reflected by the half mirror 21 to be reflected by the semiconductor element 2
The semiconductor element 2 is illuminated by guiding it upward.

[0004]

As described above, if the light from the lamp house 23 is guided to the semiconductor element 2 via the half mirror 21, the optical axis of the camera 10 and the irradiation direction of the illumination light can be coaxial. Therefore, when the semiconductor element 2 is illuminated, it is possible to prevent unnecessary shadows that adversely affect imaging.
However, in the lamp house 23 used in the coaxial lighting device 20, since the light from the lamp 24 is made uniform by using the convex lens 26 and the diffusion plate 27, the central portion where the filament of the lamp 24 is inevitably located. Has a problem in that all of the semiconductor elements 2 cannot be uniformly irradiated.

In recent years, the size of the semiconductor element 2 has tended to increase, but when the size of the semiconductor element 2 increases and the illumination area expands, the conventional coaxial lighting device 20 is required.
There was also a problem that it could not be adequately dealt with.

That is, since the lamp house 23 of the coaxial illuminating device 20 uses the convex lens 26, and there is a limit to the enlargement of the diameter of the convex lens 26, the illumination area is made too large due to the restriction of the lens diameter. There was also a problem that I could not do it.

Further, when a lamp house 23 accommodating a lamp 24 is arranged near the lens 12 of the camera 10,
The heat from the lamp 24 heats the atmosphere in the vicinity of the lens 12 to cause fluctuations in the atmosphere, and the images captured by the camera 10 fluctuate, which may make accurate position determination impossible.

Further, in order to solve the above problem, there is proposed a "coaxial illumination device", Japanese Patent Application No. 4-239090, which uses an optical fiber for a light emitting flat plate as shown in FIG. 5, but the semiconductor element 2 is large. As a result, the irradiation area of the lens is expanded and the angular range of the light beam incident on the lens is expanded, so that of the light that passes through the lens from the imaged part, the light beam that passes through the center of the lens is the light beam that comes from the periphery. This is affected by the law of cosine fourth, which is larger than that of the comparative example, and it was not possible to obtain a uniform illuminance distribution on the camera image pickup surface even when the light was emitted by a light emitter having a uniform illuminance distribution.

[0009]

Therefore, the coaxial illumination device of the present invention includes a camera for picking up an image of an object to be imaged, a half mirror tilted with respect to the optical axis of the camera and supported by the tip of the camera.
A diffusion plate supported laterally of the half mirror, a surface light source composed of light-emitting elements facing the diffusion plate and arranged in a concentric pattern, and an illumination control unit that electrically independently controls the light-emitting elements. And the central axis of the surface light source is arranged orthogonal to the optical axis of the camera.

The coaxial lighting device of the present invention is characterized in that the light emitting element is a light emitting diode.

Further, the coaxial lighting device of the present invention is characterized in that the shape of the entire light emitting portion is a circle or a quadrangle.

Further, according to the coaxial illumination method of the present invention, in the teaching of correction of uneven brightness, a uniform solid object is placed on the image pickup surface, the brightness distribution is measured by the recognition device, and the unevenness of the brightness distribution by the recognition device is minimized. As described above, the light emission intensity is controlled for each light emitting element arranged in a concentric circle to determine the light emission intensity data, and the light emission control is performed based on the stored light emission intensity data at the time of recognition.

Further, according to the coaxial illumination method of the present invention, in the teaching of the illumination light amount for recognizing the object to be imaged, the correction instruction for the uneven brightness is divided into a plurality of light amounts from a slight light amount to a maximum light amount. It is characterized in that it is performed and stored before teaching of an illumination light amount for recognition of an object to be imaged, and light emission is controlled based on the stored data so that the object to be imaged is uniformly imaged.

[0014]

[Function] A large number of light emitting elements are concentrically arranged on a light emitting flat plate serving as a light emitting surface, and the central axis of the surface light source is fixed so as to be orthogonal to the camera optical axis, and further, uniform illuminance is obtained on the image pickup surface. As described above, the light emission intensity is independently controlled for each concentric light emitting element.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show a coaxial lighting device according to the present invention. In the figure, 10 is a camera, and a lens 12 is arranged below the camera body 11. 41
Is a half mirror that is supported in front of the lens 12 via a mirror box 42. The half mirror 41 is supported so as to be inclined by 45 degrees with respect to the optical axis of the lens 12. Reference numeral 43 denotes a diffuser plate which is supported on the side of the mirror box 42 through a support frame 44, and 45 is also supported by the support frame 44 so as to face the diffuser plate 43, and a large number of light emitting diodes (hereinafter referred to as LEDs) 47. Is a light emitting flat plate on which are arranged surface light sources 48 arranged in a concentric pattern. Reference numeral 49 is a large number of illumination wiring cables that electrically connect the light emitting flat plate 45 and the illumination power supply 46, and 51 is the light emitting flat plate 4.
5 is a connector for connecting the lighting wiring cable 49. Reference numeral 52 is an illumination control unit including an illumination power supply 46 and a microcomputer 53. The end portion of the illumination wiring cable 49 on the side of the illumination power source 46 is bundled and fixed in a connector 46a provided on the front surface of the illumination power source 46, and each of its end faces has a ring illumination power source portion 53 in the illumination power source 46. Are connected to correspond to. Concentric LED (hereinafter LED
Each LE so that the brightness can be controlled for each ring).
Wiring is performed corresponding to each ring illumination power supply unit 53 for each D ring. Reference numeral 54 is a control signal cable connected to the microcomputer 53 to control the emission brightness of each LED ring.

Further, the end portion of the illumination wiring cable 49 on the light emitting flat plate 45 side is connected to each LED 47, and each LED 47.
The light emitting surface of the LED 47 faces the diffusion plate 43, and the end surface of each LED 47 on the light emitting flat plate 45 side is embedded and fixed in the light emitting flat plate 45.
The LEDs 47 are embedded and fixed in the light emitting flat plate 45 so as to draw concentric circles on the light emitting flat plate. The central axis of the concentric circle of the light emitting flat plate 45 is installed at a position perpendicular to the optical axis of the lens 12.

Surface light source 4 formed by each LED 47
The shape of 8 may be a quadrangular shape as shown in FIG. 3, instead of the circular shape as shown in FIG.

Reference numeral 50 in the drawing denotes a cover member arranged behind the light emitting flat plate 45.

In the above structure, when the semiconductor device 2 is mounted at the time of mounting by the coaxial lighting device according to the present invention, the light emitted from the LED 47 is emitted toward the diffusion plate 43. At this time, the illuminance distribution of the entire surface light source 48 formed on the light emitting flat plate 45 is controlled so as to concentrically increase the luminance of the peripheral portion. After the light emitted from the surface light source 48 is changed by the diffusion plate 43 so that the light emission distribution is changed more smoothly,
The semiconductor element 2 reaches the half mirror 41 and is reflected by the half mirror 41 to illuminate the semiconductor element 2. Therefore, the periphery of the semiconductor element 2 is gradually illuminated in a bright state. The emitted light is peripherally dimmed by the lens 12, and an image with a uniform image pickup area is obtained on the image pickup surface of the camera.

The teaching procedure for controlling the emission brightness of each LED in order to obtain a uniform illumination reflected light is as follows. First, place a blank paper on the surface to be imaged and let the front LED ring emit light with the same brightness.
The illuminance distribution on the white paper at this time is measured by the recognition device through the camera, and the light emission intensity of each LED ring is based on the brightness of the optical axis so that the brightness distribution of each LED ring is uniform on the camera imaging surface. The partial brightness is controlled to be corrected in order from the optical axis part. In the teaching of the illumination light amount for recognizing the object to be imaged, for each step in which the correction instruction for the brightness unevenness is divided from the minute light amount to the maximum light amount, for example, for each of 10 steps, the illumination light amount for recognizing the object to be imaged It is performed and stored before teaching, and when teaching / adjusting the illumination light amount for actual recognition of the object to be imaged, the operator adjusts the illumination light amount while reading the volume value and based on the brightness correction storage data at each stage. The interpolation correction data is calculated, and the light emission is controlled so that the object to be imaged is uniformly imaged.

Of course, it is possible to teach by using plain uniform paper or plain parts instead of the white paper for controlling the light emission. Regarding the steps for dividing the uneven brightness from the small amount of light to the maximum amount of light, the example of 10 steps is shown, but it is needless to say that the steps can be given in 5 steps, 20 steps, or more steps.

[0023]

As described above, according to the present invention, the light emitting flat plate serving as the light emitting surface is composed of a large number of LEDs, and each LED is embedded and fixed in the light emitting flat plate on the light emitting flat plate. By arranging so as to draw concentric circles, the amount of emitted light can be controlled for each concentric portion centered on the optical axis, and the semiconductor element can be uniformly illuminated on the camera imaging surface.

Further, according to the present invention, a convex lens is eliminated from the front surface of the lamp by using a large number of LEDs for the light emitting flat plate serving as a light emitting surface by electrically connecting means without using a lamp house. In addition, the area of the light emitting portion formed by the LED surface light source can be freely set, and it is possible to sufficiently cope with the expansion of the illumination area accompanying the increase in the diameter of the semiconductor element. Further, the present invention does not have a lamp as a heat source and the LED hardly generates heat, so that it is possible to reliably prevent the atmosphere near the lens of the camera from being heated by the lamp, and at the same time, in front of the camera. The arranged light emitting unit can be significantly downsized.

Further, since the LED having a long life is used as the light source, maintenance is not required as compared with the conventional incandescent lamp, halogen lamp or fluorescent lamp.

[Brief description of drawings]

FIG. 1 is a side view showing a partial cross section of a coaxial lighting device according to an embodiment of the present invention.

FIG. 2 is a front view showing a light emitting flat plate of the coaxial lighting device according to the embodiment of the invention.

FIG. 3 is a front view showing a light emitting flat plate of a coaxial lighting device according to another embodiment of the present invention.

FIG. 4 is a partial sectional side view of a conventional coaxial lighting device.

FIG. 5 is a partial sectional side view of a conventional coaxial illumination device using an optical fiber.

[Explanation of symbols]

 10 Camera 12 Lens 41 Half Mirror 43 Diffuser 47 Light Emitting Element (Light Emitting Diode) 48 Surface Light Source 52 Lighting Control Section

Claims (5)

[Claims] 1. A camera for picking up an image of an object to be imaged, and a half mirror tilted with respect to an optical axis of the camera and supported by a front end of the camera.
A diffusion plate supported laterally of the half mirror, a surface light source composed of light-emitting elements facing the diffusion plate and arranged in a concentric pattern, and an illumination control unit that electrically independently controls the light-emitting elements. And a coaxial illumination device in which the central axis of the surface light source is arranged orthogonal to the optical axis of the camera. 2. The coaxial lighting device according to claim 1, wherein the light emitting element is a light emitting diode. 3. The coaxial lighting device according to claim 1, wherein the surface light source has a circular shape or a quadrangular shape. 4. The light from a light-emitting element arranged concentrically with a half mirror inclined with respect to the optical axis of the camera is reflected to illuminate the object to be imaged with a uniform solid color, and the uniform image with a solid color is formed. The luminance signal is processed by processing a video signal of an object to be imaged by the camera, the light emission intensity data necessary for uniformly controlling the measured luminance distribution is stored, and the light emitting element is based on the light emission intensity data. A coaxial lighting method that controls the amount of light independently for each. 5. The coaxial illumination method according to claim 4, wherein the light emission intensity data is stored in each step of a predetermined light amount control range.