JP2952197B2 - Image scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image scanning apparatus capable of changing a scanning range on a surface to be scanned.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 55-155328 discloses an optical scanning optical system mainly applied to an image recording apparatus, an image reading apparatus and the like and capable of changing a spot diameter. As shown in FIG. 7, a portion where a scanning light beam is parallel is provided between a light source portion and a deflector for scanning a light beam from the light source portion, and the light beam of the portion is provided. A configuration is adopted in which the spot diameter on the image forming surface is changed by converting the diameter by a light beam diameter conversion optical unit such as an afocal zoom expander.

On the other hand, optical beam diameter converting optical means such as an aperture stop having a variable aperture diameter is provided between a light source section and a deflector for scanning a light beam from the light source section to convert the light beam diameter. Such a configuration is generally well known.

In the above configuration, the diameter of the light beam from the light source is converted by a light beam diameter converting optical means provided between the light source and the deflector. The converted light beam is scanned by a deflector, enters an imaging lens such as an fθ lens, and forms and scans a light spot on the surface to be scanned. Here, for example, in the light beam diameter conversion optical element, if the light beam system is narrowly limited, the spot diameter on the surface to be scanned becomes large because the F number becomes large upon image formation by the imaging lens. .

On the other hand, when the light beam system is converted to be thick, the spot diameter on the surface to be scanned becomes smaller.

That is, in the above two examples, the diameter of the light beam incident on the imaging lens provided between the deflector and the surface to be scanned is changed, and consequently the spot diameter on the surface to be scanned can be converted. Has become.

[0007]

In the above-mentioned conventional example, only the spot diameter of the light beam becomes small and the scanning range and the scanning speed on the surface to be scanned do not change. I need to raise it.

When recording is performed by beam scanning, as is well known, in order to obtain a synchronization signal for determining a recording start position in each beam scanning, a synchronization signal forming position is set at a position where a beam first passes. Is disposed. However, when the scanning range is changed, the recording start position naturally changes. In order to cope with this, it is difficult to adjust the detection means for synchronizing signal formation every time the scanning range is changed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image scanning apparatus which can change a scanning range with a simple configuration and does not need to adjust a detecting means for forming a synchronization signal even if the scanning range is changed.

[0010]

According to the present invention, there is provided a light source unit for generating a light beam, scanning means for sequentially changing a deflection state to scan the light beam from the light source unit, and the scanning unit. A first optical system for forming an image of a light beam scanned by the scanning means on a surface to be scanned, and at least a part of the first optical system is shared with the first optical system, and the light beam scanned by the scanning means is scanned by the scanning means. A second optical system that forms an image on a surface, and a sub-scanning unit that relatively moves the light beam and the surface to be scanned in a sub-scanning direction that intersects the scanning direction of the scanning unit, An optical system scans the surface to be scanned in a first scanning range, the second optical system scans the surface to be scanned in a second scanning range different from the first scanning range, and further near a scanning start position. The light beam from the scanning means that has reached A common detecting means is provided in the first and second scanning ranges for forming a synchronizing signal by detecting from between the non-common part of the first optical system and the scanning means. An image scanning device.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment applied to an image recording apparatus will be described.
One embodiment will be described in detail with reference to the drawings.

FIG. 1 is a drawing which best illustrates the features of the embodiment. In FIG. 1, a light beam emitted from a light source section 15 such as a laser light source has a cylindrical lens 16 having a positive power only in the sub-scanning direction. Through the polygon mirror 1 which is a light deflecting means. The concave lens 2 and the toric lens 3 are fθ lenses for forming an image of the scanning light beam deflected by the polygon mirror 1 on the surface to be scanned, and are hereinafter referred to as a first imaging optical system. 4 is Mira, 5
Is a recording film provided on the surface to be scanned, 6 is sub-scanning means for sub-scanning in a direction intersecting the deflection direction with the recording film 5 interposed therebetween, and 11 is selectively advanced and retracted into the optical path by a mechanism (not shown). A possible mirror. Reference numeral 12 denotes a spherical lens for forming an image of the scanning light beam on the surface to be scanned when the mirror 11 enters the optical path, and is hereinafter referred to as an additional optical system.
Further, the entire optical system obtained by adding the additional optical system to the first image forming optical system is hereinafter referred to as a second image forming optical system. The additional optical system is not limited to the above configuration, and may be an optical system having the same positive power in the main scanning direction and the sub-scanning direction even if a plurality of lenses are combined.

FIG. 2 is a diagram showing the power arrangement of the optical system in the main scanning direction and the sub-scanning direction. The power arrangement of the first imaging optical system is shown by a solid line, and the mirror 11 enters the optical path. The power arrangement of the second imaging optical system thus performed is indicated by a dotted line. In the drawing, α and β represent the maximum angle (ψ) between the optical axis and the light beam on the film surface after entering the mirror, and α ′ and β ′ represent after entering the mirror.

Here, on the imaging plane, ie, the film plane,
The spot diameter d has the following relationship with the maximum angle ψ.

D = kλ / nψ (ψ≪1 rad)

Here, k is a constant, λ is the wavelength of light, and n is the refractive index of the medium on the film surface.

The spherical lens 12, that is, the additional optical system is a spherically symmetric optical system having a positive power and, for example, has a function of reducing the focal length in each of the main scanning direction and the sub-scanning direction to approximately 1/2. After the mirror 11 enters, the maximum angle is substantially doubled in each of the main scanning direction and the sub-scanning direction. Therefore, according to the above relational expression, the spot diameter on the film surface after entering the mirror 11 is approximately 1/2 in each of the main scanning direction and the sub-scanning direction.

Returning to FIG. 1, the polygon mirror 1 and the mirror 11
The small mirror 7 is arranged on the optical path near the scanning start position between the small mirror 7 and the light beam turned back by the small mirror 7
Through a photodetector 9 for generating a synchronizing signal.
Is guided. As a result, a synchronization signal can be generated at the same timing with only one set of optical system and photodetector regardless of the movement of the mirror 11 into and out of the optical path.

FIG. 3 is a block diagram of a control system according to the present embodiment. The central control means 30 controls the lens insertion means 32 and the sub-scanning speed control means 31. Lens insertion means 32
Drives the mirror 11 according to a control signal from the central control means 30 to enter or leave the optical path. The sub-scanning speed control means 31 has a function of controlling the sub-scanning speed of the sub-scanning means 6 by a control signal from the central control means 30, and when the mirror 11 is inserted into the optical path, the change rate of the spot diameter is changed. Both the sub-scanning speed and the speed are changed in accordance with. For example, when the spot diameter becomes approximately 1/2 as described above, the sub-scanning speed is also approximately 1
/ 2. Also, the sub-scanning speed detecting means 33
Detects the speed of sub-scanning by the sub-scanning means 6 and feeds back the result to the sub-scanning speed control means 31 to perform feedback control.

In the above configuration, in the optical system in which the mirror 11 is retracted from the optical path, that is, in the first imaging optical system, the scanning light beam deflected by the polygon mirror 1 is condensed by the lenses 2 and 3. And folded back on mirror 4 on film 5
An image is formed at a position 5A, and the recording surface of the film 5 is scanned in the main scanning direction.

On the other hand, the mirror 11 is made to enter the optical path between the first imaging optical system and the mirror 4 as shown by a dotted line, and substantially added between the first imaging optical system and the surface to be scanned. In a state where the optical system has entered, that is, in the second imaging optical system, the light beam condensed by the lenses 2 and 3 is turned by the mirror 11 and enters the spherical lens 12, that is, the additional optical system. The additional optical system is an optical system having the same power in both the main and sub scanning directions, and forms an incident scanning light beam at a position 5B on the film 5.

When the mirror 11 moves back and forth, the sub-scanning speed is set by the sub-scanning speed control means 31 shown in FIG. 3 according to the change rate of the spot diameter. As a result, the aspect ratio of the image is kept constant even when the magnification is changed. Note that the sub-scanning speed may be set to a desired value, and the aspect ratio of the image may be set to a desired ratio.

Instead of recording on the same film as shown in the figure, films of different sizes may be arranged at the positions of 5A and 5B and selectively recorded. For example, a silver halide film of a general size is arranged at the position of 5A, and a small film for slide is arranged at the position of 5B.
It is also possible to change the size of the same image and record it at a variable magnification.

The surface to be scanned is not limited to a recording film.
A recording medium such as a photosensitive drum may be used.

According to this embodiment, the following effects can be obtained.

(1) Since the focal lengths in the main scanning direction and the sub-scanning direction are proportionally reduced, the diameter of the spot formed on the film 5 is also reduced substantially proportionally.

(2) Since the conjugate relationship between the polygon surface and the film 5 is maintained in the sub-scanning direction, even when the additional optical system 11 is inserted, the function of correcting the surface tilt of the polygon mirror 1 is maintained.

(3) The additional optical system can maintain the fθ correction function by balancing aberrations irrespective of the movement into and out of the optical path.

(4) A scaled image of an image obtained before the additional optical system is inserted can be obtained with the same pixel clock. That is, there is no need to change the clock frequency before and after the insertion of the additional optical system.

(5) Since the diameter of the scanning light beam at the polygon mirror does not change, it is not necessary to change the size of the polygon mirror.

(6) Since the diameter of the light beam incident on the first imaging optical system does not change, the surface accuracy of the fθ lens may be the same as that of the conventional one.

(7) Since the pixel density in the sub-scanning direction can be freely changed, the aspect ratio of the recorded image can be kept constant before and after the mirror 11 is inserted. That is, a scaled image having the same magnification in the vertical and horizontal directions can be obtained. Conversely, the aspect ratio of the image can be set to a desired ratio.

(8) Synchronous signals can be generated at the same timing before and after the mirror 11 is pushed by only one set of timing signal detecting means.

Next, a second embodiment of the present invention will be described with reference to FIGS. 1 denote the same or similar members.

FIG. 4 is an overall view of the image recording apparatus, and FIG. 5 is a detailed view of the optical system. In both figures, the additional optical system formed by the combination of the concave lens 21 and the fθ lens of the convex lens forms a so-called retrofocus type optical system, and has a positive power as a whole. This additional optical system 23 can be selectively advanced and retracted in the optical path by a mechanism not shown,
When the additional optical system enters the optical path, the first fixed
, Ie, a second imaging optical system combined with the lenses 2 and 3 is formed.

Since the additional optical system is a retrofocus type optical system, the entire optical path length does not change before and after insertion into the optical path. That is, when inserted into the optical path, the optical path length to the surface to be scanned does not change despite the fact that the focal length is short. Therefore, before and after insertion, the spot diameter can be changed without changing the imaging position, and main scanning can be performed on the same line of the scanned surface by changing the scanning range. Before and after insertion, the spot diameter and the scanning range change proportionally.

The configuration of the control system of this embodiment is the same as that of FIG.
The sub-scanning speed is changed in accordance with the advance and retreat of the additional optical system, and a scaled image having the same magnification in the vertical and horizontal directions can be obtained.

FIG. 6 is a diagram showing the power arrangement in the main scanning direction and the sub-scanning direction of the optical system shown in FIG. The power arrangement of the second imaging optical system in which the additional optical system 23 is arranged in the optical path is indicated by a dotted line in the figure.

In this embodiment, images can be recorded at the same scanning position at different magnifications.

In Examples 1 and 2 above,
The additional optical system is a power-invariant optical system that can advance and retreat in the optical path, but may be a zoom optical system. By using a zoom optical system, the spot diameter can be arbitrarily changed. The zoom optical system may be able to advance and retreat in the optical path as in the embodiment, or may be fixed in the optical path.

Next, a third embodiment of the present invention will be described.
The configuration is similar to that of FIG. 1 or FIG.

In FIG. 1 or FIG. 4, an anamorphic optical system having a plurality of lenses having different powers in the main scanning direction and the sub-scanning direction and having the same focal plane in both directions is employed as an additional optical system. Accordingly, the aspect ratio of the spot shape in the main scanning direction and the sub-scanning direction on the surface to be scanned can be set to a predetermined value by the second imaging optical system in which the additional optical system is inserted. Furthermore, if the second imaging optical system is an anamorphic zoom optical system, the spot size and the scanning range can be freely changed along with the aspect ratio.

In the embodiment shown in FIG. 1 or FIG. 4, since the additional optical system is an optical system having the same positive power in both the main and sub scanning directions, the spot diameter on the surface to be scanned is both the main scanning direction and the sub scanning direction. It becomes smaller almost in proportion.

Accordingly, there is a feature that the ratio of the spot diameter in the main scanning direction and the spot diameter in the sub scanning direction does not change regardless of the movement of the additional optical system.

However, when recording a fine image such as a slide, the image quality may be improved by making the spot diameter in the sub-scanning direction smaller than when recording an ordinary image. If the control width of the sub-scanning speed by the sub-scanning speed control means is limited, it may be necessary to change the spot diameter in the sub-scanning direction to compensate for the deterioration in image quality. The present embodiment provides an optical system suitable for such a case.

In all of the embodiments described above, a reduced image is obtained by using the additional optical system as an optical system having a positive power. On the contrary, the additional optical system is used as a whole. If the optical system has a negative power, the spot size and the scanning range are enlarged, so that a magnified image can be obtained.

Although the above embodiment is applied to an image recording apparatus, the scanning optical system of the present invention can be applied to an image reading apparatus. That is, the spot diameter and the scanning range are changed according to the size of the image to be read, and the image of different size can be scanned and read by a simple optical system.

[0048]

According to the present invention, different scanning ranges for forming a synchronizing signal by detecting a light beam from the scanning means reaching the vicinity of the scanning start position from between the non-common part and the scanning means. By providing a common detecting means, the detecting means for synchronizing signal formation can be shared in different scanning ranges without adding a special configuration, and the apparatus configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention,

FIG. 2 is a power arrangement diagram of an optical system,

FIG. 3 is a block diagram of a control system,

FIG. 4 is a configuration diagram of a second embodiment of the present invention,

FIG. 5 is a detailed view of an optical system,

FIG. 6 is a power arrangement diagram of the optical system,

FIG. 7 is a configuration diagram of a conventional example,

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polygon mirror 2 Concave lens 3 Toric lens 4 Mirror 5 Film 5A, 5B Scanning position 6 Sub-scanning means 7 Small mirror 8 Convex lens 9 Photodetector 11 Mirror 12 Convex lens 15 Laser light source

Claims (3)

(57) [Claims] A light source for generating a light beam; scanning means for sequentially changing a deflection state to scan the light beam from the light source; and a light beam scanned by the scanning means being imaged on a surface to be scanned. A second optical system that shares at least a part of the first optical system with the first optical system and forms an image of a light beam scanned by the scanning unit on a surface to be scanned; Sub-scanning means for relatively moving the light beam and the surface to be scanned in a sub-scanning direction intersecting with the scanning direction by the scanning means, wherein the first optical system scans the surface to be scanned in a first scanning range Then, the surface to be scanned is scanned by the second optical system in a second scanning range different from the first scanning range, and the light beam from the scanning unit that has reached near the scanning start position is further transmitted to the second scanning range. A non-common part of the optical system with respect to the first optical system, and scanning means; An image scanning apparatus, comprising: a common detection means provided in the first and second scanning ranges for forming a synchronizing signal by detecting from between. 2. The method according to claim 1, wherein the detecting unit includes the scanning unit and the second unit.
The image scanning device according to claim 1, further comprising a mirror for extracting a light beam between the optical systems. 3. The image scanning apparatus according to claim 1, wherein at least a part of the second optical system has an optical member that can be inserted into and removed from an optical path of the first optical system.