JPH02298933A - Image forming device with distance detecting means - Google Patents

Abstract

PURPOSE:To accurately detect the quantity of flotation of a document and to accurately project and form image information on the surface of a photosensitive body by arranging a light projection means and a photodetection means so that their optical axes cross each other at right tangles. CONSTITUTION:The optical axis 101 of the projection means 103 and the optical axis 102 of the photodetecting means 104 are made to cross each other almost at right angles and the image formation magnification on the surface of the sheet document is made constant. At this time, when the sheet document is mounted on the surface of contact glass 2, the luminous flux from a light emission member 4 passes through an optical axis A and is converged on a reference point 6a on the surface of a light receiving element 6. When a bodily document is mounted, on the other hand, the luminous flux passes through an optical path B in a center flotation area and is converged on a point 6b on the surface of the element 6. The point 6b shifts from the position 6a by a distance (x). This distance (x) varies as compared with the quantity (y) of flotation of the document 1 from the glass 2 sine the image formation magnification of an image forming means 5 is constant.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image forming apparatus having a distance detecting means, and in particular to a thick book type with a closed back as image information placed on a document table. Even if the document has a partially depressed area, such as HMA, image information on the surface of the document can be projected and formed on a predetermined surface such as a photoreceptor with high precision, and is suitable for, for example, a copying machine. It is.

(Prior Art) Conventionally, in image forming apparatuses such as copying machines, a document placed on a document table (contact glass) is scanned by a light beam from a light source, and a light beam reflected from the document surface is used to scan the document. Image information on the document surface is projected onto the surface of the photoreceptor by a projection lens.

The projection lens used in such an image forming apparatus is required to have a wide angle of view, high resolution, and short focal length, and generally, the depth of focus during projection imaging is extremely shallow at about 1 mm.

Therefore, in order to obtain a clear image, it is necessary to place the original in close contact with the contact glass surface that constitutes the original table.

For example, when attempting to form image information on a photoreceptor surface for a book-type original such as a two-page spread book in which the central binding part is raised, the raised part is copied black or becomes unclear.

In particular, the thicker the contact glass or the newer the contact glass, the more it lifts up from the contact glass, and the width of the blurred part and the width of the black streak tend to become wider.

Conventionally, the raised area is pressed from above the document pressure plate to reduce the amount of raised part and the copy is made, but it is not possible to completely eliminate the blurred area and the width of the black line, and the binding part of the original is prone to tearing. , and there was also the problem of damaging the manuscript.

As a method of eliminating such black streaks in raised portions, a conventional method has been to erase portions corresponding to the raised portions on the image surface of the photoreceptor.

However, although this method can erase black lines, there is a problem in that depending on the degree of raisedness, even necessary image information such as characters may be erased.

(Problems to be Solved by the Invention) On the other hand, for example, in JP-A-61-264857 and JP-A-62-257141, when a book-type original with raised surfaces is used, the contact glass of the original We propose an image forming apparatus that detects the amount of lifting from the photoreceptor using a distance detection means, drives optical elements such as lenses and mirrors according to the amount of lifting, and constantly forms a focused image on the surface of the photoreceptor. are doing.

FIG. 4 is a schematic diagram of the main part of the distance detecting means in the image forming apparatus proposed in the publication.

In the figure, the surface 2 of the document table 2 is made of contact glass, etc.
Lifting of the original surface 1b of the original 441 placed on a fft
A light beam from a light source 4 is projected onto the document surface 1b by a light projecting lens 3, and a reflected light beam from the YrC surface 1b is imaged by a light receiving lens 5 onto a surface of a light receiving element 6. and light receiving element 1
The elevation ff1y is determined by detecting the imaging position of the reflected light beam on the surface.

However, the image formation state (spot diameter) of the reflected light beam from the document surface 1b on the light receiving element 6 surface changes variously depending on the amount of lift, and the image formation position (ly) of the reflected light beam on the right side of the light receiving element 6 surface varies. There was a problem in that it was very difficult to obtain it accurately.

Further, in Japanese Patent Application Laid-Open No. 60-117230, as shown in FIG. Each element is set to .

In the publication, a position 2al on the surface of the document table 2 forms an image on the light receiving element 6 surface at an imaging magnification β1, and a raised portion 1bl on the document surface 1b forms an image at an imaging magnification β2 different from the imaging magnification β1. The image is formed on the 6th surface of the light receiving element.

Therefore, the relationship between the uplift tity from the document table surface 2a and the change fix in the imaging position of the reflected light beam from the document surface 1b on the light receiving element 6 surface is non-linear as shown in FIG. For this reason, when each optical element is driven and focused based on the output signal from the light-receiving element 6, each optical element must be driven non-linearly, which complicates the configuration of the driving section and control section. There was a problem.

Further, there is a problem in that specularly reflected light from the surface of the document table (contact glass) is incident on the surface of the light receiving element 6, reducing the S/N ratio.

The present invention has been developed by appropriately setting the optical arrangement of a light projecting means for projecting a light beam onto a document placed on a white surface and a light receiving means for receiving a light beam reflected from the surface of the document. An object of the present invention is to provide an image forming apparatus having a distance detecting means capable of accurately detecting the amount of lift (distance) from the surface of a document and projecting image information of the entire document surface onto a photoreceptor surface with high precision. Further, the distance detecting means is capable of appropriately setting the light emitting conditions of the light projecting means, preventing specularly reflected light from the contact glass from entering the light receiving element surface, and enabling highly accurate detection with a high S/N ratio. An object of the present invention is to provide an image forming apparatus having the following features.

(Means for Solving the Problems) An image forming apparatus having a distance detecting means of the present invention is provided with an image forming apparatus having a distance detecting means of the present invention, when an original placed on an original platen is projected onto an image carrier surface by a projection means. A light beam is projected obliquely onto the document table surface, a light receiver receives the reflected light beam from the document surface, and a calculation means uses a signal based on the incident position of the reflected light beam on the light receiver surface. An image forming apparatus that determines a distance from the document table surface to the document surface and optically displaces a part of the projection device based on a signal from the calculation device to adjust the imaging relationship. , the light projecting means and the light receiving means are arranged so that their respective optical axes are orthogonal to each other.

(Embodiment) FIG. 1 is a schematic diagram of a main part of an embodiment of the present invention. In the figure, l is a manuscript, and a book-type manuscript such as a book with a binding part in the center is shown as an example. Reference numeral 2 denotes a document table, which is made of transparent contact glass or the like. Reference numeral 9 denotes distance detecting means, which scans and detects the lift from the document table (contact glass) 2 when the document 1 is placed on the document table 2, as shown in the same figure, by a method described later. are doing.

A light source 7 scans and illuminates the original 1. A concave mirror 8 condenses the light beam from the light [7] and illuminates the original 1.

Reference numerals 10, 11, 12, and 13 are mirrors, respectively, and 14 is a projection lens, which projects the image information on the original H41 plane onto the drum-shaped photosensitive section 15 at a predetermined magnification.

! Reference numeral 7 denotes a calculation means, and the lens motor control device 18 uses the lifting amount of each region of the original 1 determined by the distance detection means 9.
The number of driving pulses is determined and stored in the storage means 19.

The lens motor control device 18 stores the original M4 from the storage means 19.
The motor 16 is driven based on the number of drive pulses for each region on the f-plane. The motor 16 drives an optical element such as a mirror on the optical axis so as to form an image on the projection lens 14 or the surface of the original 1 or photoreceptor 15 based on a signal of the number of driving pulses from the lens motor control device 18. .

As a result, the image information of the entire surface of the original H41 is projected and imaged onto the surface of the photoreceptor 15 with good density.

Next, the optical principle of the distance detecting means 9 of this embodiment will be explained using FIG. 2.

In the figure, the luminous flux emitted from the light emitting member 4 during scanning on the original M4f surface is converted into a parallel luminous flux by the collimator lens 3, and irradiates the original surface. Light emitting member 4 and collimator lens 3
constitutes a light projecting means 103. [A part of the reflected light beam from $1 is focused by the imaging lens 5 and formed into an image on the surface of the light receiving element 6.

The imaging lens 5 and the light receiving element 6 constitute a light receiving means 104. Then, by detecting the distance X of the focusing position (imaging position) of the reflected light beam on the light receiving element 6 from the reference position, the lifting amount y of the surface of the document 1 from the contact glass 2 is determined.

At this time, in this embodiment, the optical axis 101 of the light projecting means 103 and the optical axis 102 of the light receiving means 104 are made to be substantially perpendicular to each other.
The magnification of the image formed on one side of the original by the light receiving means 104 is kept constant.

That is, in the figure, when a flat sheet original is placed on the surface of the contact glass 2, the light beam from the light emitting member 4 passes through the optical path A and is focused on the reference point 6a on the surface of the light receiving element 6.

On the other hand, when a book type original is placed, the raised area in the center passes through the optical path B and points 6b on the surface of the light receiving element 6.
focus on.

The focusing position 6b at this time is shifted by a distance X compared to the reference position 6a for other flat surfaces or sheet originals. At this time, the distance l11x is equal to the original value because the imaging magnification of the imaging lens 5 is constant as described above. It changes in proportion to the lifting amount y of I41 from the contact glass 2.

In this embodiment, the angle between the light beam from the light emitting member 4 and the document table 2 is θ, and the position irradiated by the light beam on the surface of the document 1 is the focal point when the imaging lens 5 forms an image on the surface of the light receiving element 6. If the image magnification is β, then there is the following relationship: y=sinθ×βX (1).

Conventionally, the imaging magnification differed depending on the position on the photodetector surface.
In other words, β was a function of X, but in this embodiment, as described above, each element is set so that the imaging magnification β is always constant regardless of the lift of the original 1 ff1y. For this reason (
1) Equation is simply the amount of uplift y and the distance 1IIx which is the amount of deviation.
becomes a linear function as shown in FIG.

This allows the original M4f to be easily calculated by finding the distance sl×.
The lifting amount y from the contact glass 2 is detected.

In this embodiment, the light receiving element 6 is, for example, a 1-line CCD.
COD the deviation X of the image formation position on the light receiving element using a sensor
It is configured to digitize the image at a pixel pitch of , and output the pixel number at the imaging position.

Now, output pixel number 2. The difference between the output pixel number 10 and the direct output pixel number 1. - Lifting change corresponding to xo! it
is determined, and the number of drive pulses corresponding to the amount of change is calculated by the calculation circuit 17 and stored in the storage circuit. In the conventional example, since the imaging magnification was different at each position on the light receiving element surface, the number of driving pulses changed by 1 pixel.
It was not possible to make it correspond to driving by the number of pulses.

For example, the output pixel number is 12 = 2. It, = 1゜I
L, = o, and the amount of raisedness corresponding to each output pixel number is y2 = 0.7 mm% y1 = 0.3 mm, y.

=Omo+. It I−It o = 1 0
= 1.1□-ffil =2 1=1. y+
7゜=0.3-0=0.31m%y2-'/l=0.7
-0.3=0.4mm, and if there is a shift of 1 pixel from 2° to iLI, the amount of change in elevation is 0.3mm, and 1
．． When there is a one pixel change from 1 to 12, the amount of change in elevation is 0.4IIIm.

Conventionally, in this case, one pulse of the motor was set to correct the amount of lift change by 0.1 mm, and from 2° to U,
3 pulses, 2. It is necessary to send a 4-pulse signal from 12 to 12.

On the other hand, in this embodiment, since the imaging magnification β is constant, when the number of drive pulses changes by one pixel, it can be adapted to drive by one pulse. For example, now, output pixel number x2=z'.

ILl=1.2o=0, and the lifting amount corresponding to each output number is 3/2=0. 6mm, y, =0.3
mIII, y0=Omn+. When there is a shift of one pixel from Il to i, the amount of change in elevation is 0.3 mm, and when there is a shift of one pixel from 11 to 12, the amount of elevation is also 0.3 mm. In this case, it can be set to correct the lift change amount by 0.3 mm with one pulse, and fi
, to 2. 1 pulse! , it is sufficient to send one pulse signal from Il2.

Accordingly, in the conventional example, the maximum number of pulses is required to be several times the maximum number of pulses. The increase in the number of drive pulses per unit time is the motor drive frequency. This increases the motor size, which is undesirable.

In contrast, this embodiment has the advantage of being able to use the maximum number of pixels.

In this embodiment, the incident angle α of the luminous flux from the light projecting means of the distance detecting means onto the original document 1 is set so that the specularly reflected light from the contact glass does not enter onto the surface of the light receiving element 6.

in particular, 15° 　α　〈40゜ 50° 　α　〈750 It is within the range that satisfies the following formula.

That is, since the raised portion of a document generally has a curved surface as shown in FIG. 1, only a small amount of the diffusely reflected light beam is focused on the light receiving element. For this reason, it is conceivable that the intensity of the specularly reflected light, which is the noise light flux from the contact glass, is greater than that of the signal light flux. When the intensity of the specularly reflected light becomes stronger in this way, the original is mistakenly perceived as being on the contact glass, even though the original is floating.

Therefore, in this embodiment, the incident angle of the light beam from the light projecting means is set as described above so that the specularly reflected light from the contact glass does not enter the light receiving element.

FIG. 7 is a schematic diagram of main parts of a second embodiment of the present invention. In this figure, the same elements as those shown in FIG. 1 are given the same reference numerals.

In this embodiment, the light beam from the light projecting means of the distance detecting means 9 and the reflected light beam from the Jg and Mk surfaces are received through image forming mirrors 10, 11 and 12, as shown in FIG. This is different from the first embodiment.

In this embodiment, a preliminary scan is performed before starting the copying operation of the original i1 onto the surface of the photoreceptor 15. Then, the amount of lifting in the entire area of the original 1 is detected, and the corresponding number of motor drive pulses by the lens motor control device is determined by the calculation means 17 and temporarily stored in the storage device 19. Next, during the copying operation, by sequentially sending the memorized number of drive pulses to the lens motor control device 18, the motor 16 controls the projection lens 14.
is driven to correct lifting of the original 1 from the contact glass 2.

In this embodiment, since the distance detecting means 9 can be fixed on the main body of the image forming apparatus, the light emitting member, the light receiving element, etc. This makes it possible to further simplify the arrangement of driving circuits, etc.

1st. In the second embodiment, a halogen lamp having a wide range of spectral sensitivity is used as a light source for image formation, and a preliminary scan is performed to determine the amount of lift of the original 1 from the contact glass 2.

On the other hand, an infrared light emitting diode is used as the light source of the light projecting means of the distance detecting means, an element sensitive to the infrared region is used as the light receiving element, and the exposure light source of the image forming apparatus has no spectral characteristics in the infrared region. If a light source such as a fluorescent lamp is used, the light flux from the exposure light source can be made to have no effect on the detection by the distance detecting means. By configuring each element in this way, it is possible to perform exposure scanning of the original at the same time as detecting the amount of lifting of the original 1 from the contact glass 2, and the preliminary scanning can be omitted.As a result, rapid image formation is possible. It can be done.

(Effects of the Invention) According to the present invention, the optical arrangement of the light emitting means and the light receiving means of the distance detecting means is set as described above, and the imaging magnification of the document surface illuminated by the light emitting means on the light receiving element is constant. As a result, the amount of lift of the original from the contact glass can be easily and highly accurately determined using the output signal from the light receiving element, and the driving control of the projection lens can be easily controlled. Accordingly, it is possible to achieve an image forming apparatus having a distance detecting means suitable for a copying machine or the like, which can accurately project and form image information on a photoreceptor surface.

Furthermore, the present invention prevents unnecessary light from entering the light receiving element by appropriately setting the angle of incidence of the light beam from the light projecting means on the document surface, thereby enabling distance detection with a high S/N ratio. It has the following features.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the main parts of the first embodiment of the present invention, FIG. 2 is an explanatory diagram of the distance detection means of FIG. 1, and FIG. FIGS. 4 and 5 are explanatory diagrams showing the relationship between the lifting amount of 59L, and FIGS. 4 and 5 are explanatory diagrams of distance detection means in a conventional image forming apparatus. FIG. FIG. 7 is an explanatory diagram showing the relationship with the lifting amount of the original, and is a schematic diagram of the main part of the second embodiment of the present invention. In the figure, 1 is the original, 2 is the original table (contact glass), and 3
1 is a light projecting lens, 4 is a light emitting member, 5 is an imaging lens, 6 is a light receiving element, 7 is a light source, 103 is a light projecting means, 104 is a light receiving means, 14 is a projection lens, 15 is a photoreceptor, 16 is a motor,
17 is an arithmetic circuit, 18 is a lens motor control device, and 19 is a storage means. Father-in-law 3rd place 4th picture 5th picture 6th picture

Claims (3)

[Claims] (1) When projecting an original placed on the original table surface onto the image carrier surface by the projection means, the light beam from the light projecting means is projected obliquely onto the document table surface, and the light beam is reflected from the document surface. A light beam is received by a light receiving means, and a distance from the document table surface to the document surface is determined by a calculating means using a signal based on the incident position of the reflected light beam on the surface of the light receiving means, and based on the signal from the calculating means. An image forming apparatus in which the image forming relationship is adjusted by optically displacing a part of the projection means, wherein the light projection means and the light reception means are arranged so that their respective optical axes are orthogonal to each other. An image forming apparatus having a distance detecting means. (2) Distance detection according to claim 1, characterized in that each element is set so that the irradiation position on the document surface by the light projecting means and the light receiving surface of the light receiving means have a constant imaging magnification. An image forming apparatus having means. (3) The light projecting means is arranged so as to satisfy the following conditions: 15°<α<40° 50°<α<75°, where α is the angle of incidence of the light beam from the light projecting means onto the document table surface. An image forming apparatus having a distance detecting means according to claim 1.