JP3072805B2 - Gap spacing measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for non-contact measurement of a gap interval.

[0002]

2. Description of the Related Art Conventionally, in a non-contact gap measurement, a light projecting unit and a light receiving unit are opposed to each other, and a gap to be measured is arranged therebetween.
Light or slit light scanned by the light projecting means is projected, and a light-passing type gap measuring method for determining a gap interval from the width of light passing through the gap, and an edge portion forming the gap are illuminated,
There is a method of measuring the gap width using a microscope. FIG. 8 is a diagram showing the former. Reference numerals 1 'and 2' denote drums forming a gap to be measured, 7 'denotes a housing, 36 denotes light receiving means, 37 denotes light projecting means, and 37A denotes an optical path of a projected light beam.

[0003]

However, the light-passing type gap measuring method has to secure an optical path for transmitting the measuring light, and cannot be used for a measurement object which cannot secure this optical path. In addition, when the measurement object is at an interval between the two cylinders, the reflected light on the cylinder surface becomes smaller as approaching the edge in the microscopic measurement, and the reflected light hardly returns at the edge, so that the boundary between the cylinder and the gap is determined. Difficult to distinguish,
It is difficult to measure accurately.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and has as its object to provide a method capable of measuring a gap interval with a high degree of freedom in device configuration and with high accuracy.

[0005]

In order to achieve the above-mentioned object, a method according to the present invention is arranged such that an illuminating means is arranged on one side of a gap to be measured, and a diffusing surface arranged on the opposite side of the illuminating means is provided with the gap. Illuminated by the illumination means, and a silhouette image of the gap is captured by the light receiving means from the illumination means side through an objective lens and through a slit provided between the objective lens and the gap in parallel with the gap. Then, the gap interval of the gap to be measured is measured.

[0006]

According to the present invention, since the light is projected from one side and the diffused surface is illuminated through the gap, in the conventional light-passing type measurement, it is impossible to arrange the light emitting and receiving means due to, for example, an obstacle in the optical path. In the present invention, even if the measurement cannot be performed, the degree of freedom in the arrangement of the light receiving means can be measured. Furthermore, by illuminating the diffusion surface on the opposite side of the light emitting means, a silhouette image with sharp contrast at the edge part is obtained,
Gap measurement can be performed accurately.

[0007]

FIG. 1 is a perspective view and a side view showing the structure of a gap detecting section between a photosensitive drum and two developing sleeve cylinders of a toner cartridge of a laser printer according to an embodiment of the present invention. FIG. FIG. 2 is a block diagram of a configuration and a signal processing system as viewed from a side of the gap measurement device including an interval detection unit.
1 is a photosensitive drum, 2 is a developing sleeve, and a gap (about 300 μm) between these two cylinders (about φ30 mm) is an object to be measured. Reference numeral 3 denotes a laser light source for illumination, which illuminates the diffusion surface 4 through a gap to be measured. The diffusion surface 4 is located at a position about 20 mm from the gap to be measured. Reference numeral 5 denotes a slit which is set in the same direction as the longitudinal direction of the gap to be measured. 6
Is an objective lens for enlarging the image of the gap, and 7 is a CCD camera for picking up the enlarged gap image. In addition, a line sensor may be used for 7, and in that case, the mounting direction is set to a direction perpendicular to the longitudinal direction of the gap. Further, in FIG. 2, reference numeral 8 denotes a toner cartridge, and 9 denotes means for fixing the toner cartridge 8. 10, 11 and 12 are precision stages for driving the entire gap measuring section shown in FIG. 1 in the focusing direction, the direction perpendicular to the gap, and the optical axis angle direction, respectively, 13 is an AD converter for converting an analog video signal into a digital signal, 14 is an image memory,
Reference numeral 15 denotes a small computer for calculating the gap width and controlling the entire system.

[0008] The imaging focus of the light receiving means constituted by the CCD camera 7 and the objective lens 6 is set to the photosensitive drum 1 and the developing sleeve 2.
The diffusing surface 4 is arranged outside the depth of focus in accordance with the gap between. The diffusion surface 4 may be the inner surface of the toner cartridge 8.
The diffusion surface 4 is illuminated through the gap to be measured using the laser light source 3 as a light source. The illumination position is on the optical axis of the light receiving means. The illumination light passes through the gap obliquely with respect to the optical axis of the light receiving system so as to be outside the field of view of the light receiving means. By collimating the beam diameter of the illuminating light to the same diameter as the gap to be measured, the amount of light blocked by the cylinder when passing through the gap is reduced, so that the amount of light loss is reduced and the illumination efficiency is good.

Here, the CCD camera obtains a silhouette image of the gap (shown in FIG. 3A) using the place illuminated by the laser light as a secondary light source. That is, the gap portion 18 becomes bright because scattered light from the diffusion surface can pass therethrough, and the cylindrical portion 1
In the images 6 and 17, since the light is blocked, a dark and contrasted image can be obtained. In order to make the contrast clear, illumination light is obliquely incident on the optical axis of the light receiving system so that the cylindrical surface is not illuminated by the laser light for illumination. Further, the performance of the photoreceptor used for the photoconductive drum is impaired when exposed to external light, so the measurement is performed in a dark place. As a light source for illumination, a semiconductor laser, a HeNe laser, or the like having a wavelength range not affecting the photoconductor is used.

Next, this image is input to an image memory 14 through an AD converter 13 and image processing is performed by a small computer 15 to obtain a gap interval. Since the image obtained here is illuminated by the diffused laser light, speckles occur in the image of the gap. Therefore, when attention is paid to only one line of the image, the measurement value variation caused by speckle is large. Therefore, by projecting the image in the longitudinal direction of the gap image and averaging the speckles, a signal waveform 19 shown in FIG. 3B is obtained. The width 21 of the light portion is determined using the center 20 of the signal levels of the light portion and the dark portion of the waveform as a threshold value, and is defined as the gap width.

In the gap measuring device provided with the above-described gap width detecting section, when the imaging focus of the light receiving means is shifted from the gap, the measurement error increases. In addition, if the optical axis of the light receiving means is shifted from the gap and the gap image deviates from the screen, the measurement cannot be performed correctly. Further, if the optical axis of the light receiving means is not perpendicular to the gap, the measurement is made smaller than the true gap width. The gap width also changes depending on the mounting posture of the toner cartridge 8, and the gap width also changes depending on the rotation and stop of the photosensitive drum 1 and the developing sleeve 2. These positional deviations of the measurement target gap are caused by dimensional errors of the measurement target. Therefore, the light emitting means and the light receiving means are integrally driven by the precision stages 10, 11, and 12, and the position of the light emitting and receiving means is set to an optimum position in accordance with the above-mentioned positional shift. Further, the toner cartridge 8 is held in the same posture as when the product is used, and the drum 1 is driven at the same rotational speed as when the product is used.

First, the focus position is set by the focus position setting stage 10. The determination as to whether the imaging position is in focus at the gap position is made based on the fact that the inclination near the edge of the gap image has become maximum. The detector is sent at a constant interval over a predetermined range in the focus direction, and the above-described inclination at each position is obtained. Then, the focus position is adjusted by returning the position of the stage 10 to the position where the inclination becomes maximum.

The position of the gap in the direction perpendicular to the longitudinal direction is determined by setting the center of the detected image to zero, determining the center of gravity of the gap image, and driving the gap position setting stage 11 in a direction to correct the center of gravity to zero. . As a result, the gap image is always located at the center of the captured image.

The angle setting of the light receiving means is performed by a measurement angle setting stage 12. Stage 12 is mounted on stage 1
The rotation center of 2 is set so that the focal position of the light receiving means coincides. In this state, the angle of the precision stage 12 is sent at a constant angle over a predetermined angle range, and a gap measurement value at each angle is obtained. The measured value is maximum when the light receiving system is perpendicular to the gap. Therefore, the angle of the detection unit is adjusted by returning the angle of the stage 12 to the angle at which the measured gap value is maximized.

The distance between the photosensitive drum 1 and the developing sleeve 2 changes depending on the mounting posture of the toner cartridge 8 and the rotation and stop of the photosensitive drum 1. Therefore, in order to measure the gap interval when the product is used, the toner cartridge 8 is mounted in the same posture as when the product is used.
Is used to measure the gap interval while rotating the motor at the same rotational speed as when the product is used.

By performing the gap measurement by adjusting the sensor attitude to the gap with the above configuration, the gap interval can be accurately measured.

Next, a slit 5 placed in front of the objective lens 6
The effect of is described. In this embodiment, when the imaging focus of the light receiving system is focused on the gap, an image in which the gap and the edge can be clearly distinguished is obtained as shown in FIG. However, if the gap is deviated from the imaging focal position of the light receiving system due to the dimensional error of the measurement object, etc.,
Without the slit 5, a bright band image 18 'is formed near the edge as shown in FIG. FIG. 4B shows a waveform obtained by projecting this image in the longitudinal direction of the gap. FIG. 4 (a)
4B appears as a light intensity peak 19 'near the edge in FIG. In the figure, the light amount peak near the edge is located outside the width of the actual bright part. Then, the light amount peak near the edge is widened by two intervals on the left and right as the light amount peak deviates from the imaging focus. Therefore, when the focus is shifted, the width 21 of the bright portion is measured to be larger than the actual value. FIG. 4 (c) plots the state 22 of the change in the measured value against the shift of the focal position. It can be seen that the measured value is minimized in the vicinity of the focus, but the area 23 where the measured value change is flat is narrow, and the measurement error increases as the focus is shifted.

Such errors are caused not only by the fact that the light scattered by the diffusing surface 4 serving as the secondary light source directly enters the light receiving system, but also that the light is reflected by the cylindrical surface and enters the light receiving system. This is because the reflected light from the cylindrical surface forms an image near the edge of the gap image. Light reflected on the cylindrical surface travels along an optical path as shown in FIG. In FIG. 6, reference numeral 1 denotes a photosensitive drum, 2 denotes a developing sleeve, and a gap between the two cylinders is an object to be measured.
4 is a diffusing surface, 5 is a slit, 6 is an objective lens, 7 is CC
D camera, 24: straight light passing straight through the gap, 25: reflected light reflected by the cylindrical surface, 26: light quantity distribution of the straight light 24 at the objective lens entrance, 27: light quantity of the reflected light 25 at the objective lens entrance Distribution, 28 is a CCD camera 7 with straight light 24
Is a light amount distribution on the light receiving surface, and 29 is a light amount distribution of the reflected light 25 on the light receiving surface. The straight light 24 passing straight through the gap concentrates at the center of the objective lens near the entrance of the objective lens.
are doing. On the other hand, the reflected light 25 reflected on the cylindrical surface is thinly and widely distributed 27 near the objective lens entrance. Each light beam has a light amount distribution near the entrance of the objective lens as shown in FIG. 6B, and the light amount distribution as a sum of these distributions. When these light beams are imaged on the light receiving surface of the CCD camera 7 by the objective lens 6, the straight light 24 that has passed straight through the gap forms an image 28 with a sharp edge on the light receiving surface. Reflected light 25
Are concentrated near the edge of the gap image on the light receiving surface, and generate a light amount peak 29 near the edge of the gap image as shown in FIG. When the focal position is changed by changing the distance between the light receiving optical system and the measured gap, the light amount peak near the edge becomes 2
The interval of 9 becomes narrower or wider. Therefore, the width of the bright portion changes, and a measurement error occurs due to defocus.

As described above, the error due to the defocus is caused by the reflected light 25 on the cylindrical surface. Therefore, the slit 5 is inserted near the entrance of the objective lens to allow all the straight light 24 to pass therethrough and block most of the reflected light 25. Here, if there is no slit 5, the gap image obtained when the slit 5 is inserted in front of the objective lens 6 at the focal position where the light intensity peak occurs near the edge as shown in FIG. And the light intensity peak near the edge disappears. It can also be seen from FIG. 5A that the projection in the longitudinal direction of the gap in FIG. 5B shows that the light amount peak near the edge is almost eliminated. FIG. 5C is a plot of the change 22 of the measured value with respect to the deviation from the focal position when the slit 5 is used. From this figure, the area 2 where the change of the measured value with respect to the deviation from the focal position becomes flat by using the slit 5 is shown.
3 spreads, and it is understood that a light receiving system strong against defocus can be formed.

FIG. 7 is a configuration diagram of a gap detecting section between the photosensitive drum of the toner cartridge and the two cylinders of the developing sleeve of the laser printer according to the second embodiment of the present invention. The same members as those described above bear the same reference numerals, but will be described briefly. 1 is a photosensitive drum, 2 is a developing sleeve, and a gap (about 300 μm) between these two cylinders (about φ30 mm) is an object to be measured. Diffusing surface 4 is about 20m from the gap to be measured
m. Reference numeral 5 denotes a slit which is set in the same direction as the longitudinal direction of the gap to be measured. 6 is an objective lens for enlarging and projecting the image of the gap, and 7 is a CC for imaging the enlarged gap image.
D camera. In addition, a line sensor may be used for 7, and in that case, the mounting direction is set to a direction perpendicular to the longitudinal direction of the gap. Further, 30 is a HeNe laser, 31 is a beam expander, 32 is a lens, 33 and 34 are apertures, and 35 is a beam splitter.

In this embodiment, the gap measurement is performed coaxially with the light emitting and receiving light. A HeNe laser 30 is used as a light source, and a light beam is expanded by a beam expander 31 and then condensed by a lens 32. By matching the focal position of the lens 32 and the image plane position of the objective lens 6, this light beam is narrowed to a beam diameter of 100 μm or less at the position of the measured gap, and the distance between the two cylinders is about 3 μm.
The light passes through the gap of 00 μm and illuminates the diffusion surface 4. At this time, the size of the illumination area can be changed by the stop 33 immediately after the lens 32. The diaphragm 34 is placed at a position conjugate to the imaging focal point of the objective lens 6 and blocks diffracted light or scattered light that directly illuminates the cylinders 1 and 2 at the gap to be measured.

According to the gap width detecting section provided with the coaxial illumination having the above-described configuration, even when the gap to be measured is only partially visible from the outside, the diffusion surface 4 can be illuminated through the gap to be measured. Can be imaged by the CCD camera 7.

[0023]

As described above, the illuminating means is arranged on one side of the gap to be measured, and the diffusion surface arranged on the side opposite to the illuminating means is illuminated by the illuminating means through the gap to be measured, and a silhouette image of the gap is obtained. Is imaged by the light receiving means from the side of the illuminating means via the objective lens, and by measuring the gap interval of the gap to be measured before, the gap interval measurement can be performed in a non-contact manner. According to the present invention, the measurement can be performed even when the measurement cannot be performed due to an obstacle in the optical path. Furthermore, since the diffusion surface on the opposite side of the light emitting and receiving means is illuminated, a silhouette image with a clear contrast at the edge portion is obtained, and the gap measurement can be performed with high accuracy. In particular, at this time, a slit is provided between the objective lens and the gap to be measured, parallel to the gap, and light is received and imaged through the slit, so that the direct reflected light from the object forming the gap can be effectively eliminated. And the measurement accuracy is improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a gap interval detection unit embodying the present invention.

FIG. 2 is a configuration diagram of a gap measuring device.

FIG. 3 is a diagram showing a detected image (a) and a signal waveform (b) obtained by projecting the detected image in a longitudinal direction of a gap and averaging the projected image.

FIGS. 4A and 4B are a detection image (a) when the imaging focus is deviated by a detection system configuration without a slit 5, a signal waveform (b) obtained by projecting the detection image in a longitudinal direction of a gap, and an average value, and a measured value for defocus; It is a figure which shows the change (c) of.

FIG. 5 shows a detection image (a) and a signal waveform (b) obtained by projecting the detected image in the longitudinal direction of the gap and averaging the detected image when the imaging focus is deviated by the detection system configuration using the slit 5, and measuring the defocus. It is a figure showing a change (c) of a value.

FIG. 6 shows the optical path of light passing between cylinders (a), the light quantity distribution of straight light 24 and reflected light 25 before the objective lens (b), and the light quantity of straight light 24 and reflected light 25 on the image plane. Distribution (c)
It is shown.

FIG. 7 is a schematic diagram of a gap interval detection unit of a coaxial illumination system according to a second embodiment of the present invention.

FIG. 8 is a configuration diagram of a conventional gap measuring device using an outer diameter measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Developing sleeve 3 Laser light source 4 Diffusion surface 5 Slit 6 Objective lens 7 CCD camera 8 Toner cartridge 9 Cartridge mounting stand 10 Focus position setting stage 11 Gap direction position setting stage 12 Measurement angle setting stage 13 AD converter 14 Image memory 15 Small Computer 16 Developing Sleeve Image 17 Photosensitive Drum Image 18 Gap Image 19 Gap Image Projection Waveform 20 Projection Waveform Threshold 21 Gap Width 22 Change in Measurement Value for Defocus 23 Measurement Width for Defocus 23 Flat Plate Width 24 Cylindrical Surface Straight light 25 that is reflected straight by a cylindrical expression 26 light quantity distribution of the straight light 24 at the entrance of the objective lens 27 light quantity distribution of the reflected light 25 at the entrance of the objective lens 28 light quantity of the straight light 24 at the light receiving surface Distribution 29 Light intensity distribution of reflected light 25 on light receiving surface 30 H Ne laser 31 beam expander 32 lenses 33 aperture 35 the beam splitter 36, 37 the outer diameter measuring instrument emitting and receiving unit

Claims (2)

(57) [Claims] 1. A place illumination means on one side of the measurement target gap, the diffusion surface disposed opposite illuminated by the illumination means through the measurement target gap with illumination means, the illumination silhouette image of the gap Through the objective lens from the means side, and
Provided between the objective lens and the gap in parallel with the gap
A gap interval measuring method for measuring the gap interval of the gap to be measured by taking an image with a light receiving means through a slit provided . 2. An object forming the gap to be measured is a cylinder.
The method according to claim 1 , further comprising a member .