JPS61113020A - Method and apparatus for generating image on photosensitive support - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a modulated light beam (hereinafter simply referred to as a beam).
The present invention relates to a method and apparatus for producing an image by scanning a photosensitive support along a continuous line, particularly for producing an image from photographs transmitted over long distances, e.g. between an artificial satellite and a ground station. Can be applied.

BACKGROUND OF THE INVENTION For applications of devices of this type it is sought to obtain images with the best possible resolution, which for a long time has been limited to within reasonable limits.

One non-limiting example of this type of device is an imaging device with a rotating drum, which is described in French Patent No. 730
It is described in detail in No. 7567.

When it is desired to increase imaging capability, e.g. production speed, various problems are encountered when the modulator itself has a limited passband or is generally included in an open loop with a limited passband itself. ing. Increasing production speed therefore requires providing modulators with wider passbands and/or open loops, which increases the complexity and cost of the device.

- Also, the mechanical elements used to perform image scanning have similarly limited capabilities; in particular, increasing the speed of the rotating drum generates fairly large centripetal forces, considering the dimensions of the drum, and also causes imbalances. This may cause contamination or destruction of the film placed on the circumference of the drum; in addition, the stepwise advancement of the carriage, which carries the mirror for reflecting the beam at the end, must be carried out in a reasonably commercial rhythm. .

The deficiencies mentioned above are encountered in other types of imaging devices as well, for example those that include rotating mirrors or use deflectors with galvanometers.

To overcome these deficiencies, multibeam devices have been designed that use acousto-optic modulators in cascades, thanks to which several image lines can be scanned simultaneously, which allows the characteristics of mechanical elements to be The OJ capability was to increase the imaging speed without modification.

Apart from their high cost, these modulators suffer from the following deficiencies: - the dependence of the adjustment of the knee beam diameter and line spacing; - the dependence of the optical intensity of the beam by the beam downstream of the first modulator; Elimination of the bombing effect, which allows only sequential modulation of pixels.

Moreover, the determination of these modulators involves complex calculations, and in fact these modulators do not allow any modification of the line spacing or the image spot diameter.

[Means for solving problems]

In order to overcome these deficiencies and allow a considerable degree of flexibility in the selection of the resolution of the images produced, the present invention provides a method for producing images on a photosensitive support, comprising: is simultaneously scanned by at least two modulated beams directed towards said support in the form of a spot by a converging lens, each beam being individually modulated and said plurality of beams being parallel to the optical axis of said lens. and symmetrically spaced apart on either side of the optical axis of the lens, and characterized in that said lens is positioned such that its focus extends beyond the surface of said support.

The invention also relates to an apparatus for carrying out this method.

〔Example〕

The present invention will now be described in more detail with reference to embodiments and the drawings.

The device for producing images from the photograph shown in Figure 1 includes a light source of 2 +IM+ (ioa), (1
0b), these are parallel beams (12a),
(12b) is released. These beams are connected to a modulator (L
4a), (14h), but the effect of the modulator is on the transmitted beams (16a), (16h).
b) the light intensity of the modulator (14a).

(14b) as a function of the electrical signal input.

The transmitted beams (16a > , (16h) are then refracted by a combination refractor (18a), (18b), respectively.
), and the role of this device will be explained below.

The refracted beams (20a) and (20b) are mirrors (24).

(26) and a semi-transparent plate (28).
) is reflected parallel to the axis XX.

A carriage (30), which moves linearly in steps parallel to the axis of the drum (22), carries a mirror (32) which reflects the beam perpendicular to the axis of the drum and of the converging lens (34). , this lens refracts the beam in the direction of its focal point F.

The outer surface of the drum (22) is provided with a photosensitive film and lies between the lens (34) and its focal point F. As a result, the beam is placed on the film at 21 distinct points Ta, Th.
will occur.

If the drum rotates but the carriage does not move,
The 2 (+lI+ spot scans two adjacent lines, following which the carriage is displaced by one segment, then the drum makes one more revolution while scanning two new lines, etc.) .

Referring now to the detailed diagrams of FIGS. 2 and 3, it will be readily appreciated that the present invention may be modified to adjust the spot width and stroke spacing.

As far as the width of the spot is concerned, it can be done by adjusting the distance between the converging lens and the surface of the drum. fact,
If φ is the diameter of the cross section of the beam reaching the lens, f is the focal length of the lens, and d is the lens/drum distance, then the width l of the spot can be expressed as Therefore, the width l can be adjusted by changing the distance d.

However, this width l can also be adjusted by changing the cross-sectional diameter φ. To this end, the invention interposes an afocal fit (36) in the optical path of the beam, for example upstream of the mirror (26). This mirror reflects the beam parallel to the axis of the drum.

This device essentially consists of two consecutive converging lenses (3
6a) and (36b), their optical axes intersect and the superimposed focal points are located between them. If al and a2 are their respective focal lengths, the cross-sectional diameter φ of the exit beam is connected to the cross-sectional diameter φ0 of the incident beam by the following relationship: φ−φ0□ In reality, the exact width of the spot is The adjustment is performed using several afocal devices (3
6) by adjusting the converging lens/drum distance.

Once the spot width is adjusted, the spot spacing or scan line spacing is easily adjusted. For this purpose (3rd
(see figure), paired refracting device (18a), (
18b) is used.

These devices consist of two transparent plates with parallel surfaces that intercept the beam exiting the modulator.

These two plates form two beams (16a).

(16h) and are assembled to rotate around two axes Ya, Yb perpendicular to the common plane of (16h) and are simultaneously driven in opposite rotational directions by micrometer displacement blocks (38).

When these two transparent plates are perpendicular to the beam, the beam is not refracted and the mirror <24> and the translucent plate (28)
) and are in a position where they intertwine in the air after being reflected. The beam thus passes through the afocal device (36) and then through the converging lens (34) along its optical axis and produces two spots on the film placed on the drum.

When the micrometer displacement block (38) is driven, the thin plate (18a) rotates counterclockwise and the thin plate (18a) rotates counterclockwise and
18b) are rotated clockwise simultaneously and by angles equal in absolute value.

Because of this rotation, the beams are offset parallel to each other and from the initial direction the beam (16a) is at a distance of %1lte.
(positive) and the beams (16h) are separated by a distance C(-).

After being reflected by the various mirrors and passing through the afocal device (36) and the converging lens, the spots formed on the drum are separated by a distance g with their center distances having the relationship: When the width of the spot is adjusted and the value of the interval is set as shown below, the interval g is the parallel plane thin plate (18a), (18b).
can be easily adjusted by (acting on) a combination of rotations.

In fact, it is difficult to find the center of both spots, so this adjustment can be done by separating the circumferences of these two spots and measuring the gap i between the distances g and g = 0 degrees Celsius. It will be done.

Naturally, in order for the successive scanning of the drum by pairs of lines to form a regular frame, it must be ensured that the numbers 1 and 1 are actually related to the pitch p of the displacement of the carriage in the following relation:

p=2 (i-+-12) Until now, we have assumed that the lens used is perfect, but in reality, due to spherical aberration, it is necessary to use a lens with a long focal length and a beam as narrow as possible. is desirable.

From the foregoing, it is clear that the invention provides a particularly simple adjustment device for precisely aligning the two incident beams parallel to the optical axis z, Z of the converging lens (34) and in a perfectly symmetrical spaced relationship with respect to this axis. It is noteworthy that this allows for faithful placement. This simple adjustment device ensures an equal value of refraction parallel to each other and opposite to the original direction (the beam coincides with the optical axis of the lens (34) when it reaches it).

In the embodiment shown in Figure 4, a single light source (10) (laser) is used, the beam of which is coupled to a mirror (40).

(42) and semi-transparent plates (44), (46) to form three parallel beams (12a)'+(12b
), (12c) and each beam is split into an individual modulator (14a).

(14b) and (14c).

The two beams coming out of the modulators (14a) and (14b) are transferred to the combination refractor (18a) as described above.
).

(18b), but the beam (16c) emerging from the modulator (14c) is guided precisely along the optical axis of the successively transmitted device.

Three spots Ta, Tb, Tc are therefore obtained on the drum, the width and spacing of which can be adjusted independently as described above.

In this case, three image lines are scanned simultaneously.

Naturally, the present device can be generalized to use 2N beams treated as a pair of beams, and to have a predetermined width and symmetrical relation to the optical axis onto the drum surface by N combination refractors. One can imagine a device that creates 2N regularly spaced spots.

Finally, the (2N+1)th H beam can be added and guided along the optical axis to create the rl central spot.

The sequential deformation of the spot as it moves outward from the center due to the spherical aberration of the lens presents a practical limit to this generalization.

As long as each beam is individually modulated, the scanning of the line produces a continuously shaded line and thus an image of excellent quality.

To control the modulator, a double set of 2N(+1) memories should be provided, one set of memories stores information about the next 2N(+1) lines, while Reading is performed for other sets of storage devices while scanning the 2N(+1) lines. At the end of the read, the carriage is advanced by one pitch p, and then the successive and write operations of these two sets of storage devices are reversed.

[Brief explanation of drawings]

1 is an overall diagram of an embodiment of the device according to the invention, FIG. 2 is a detailed diagram of a part of the device shown in FIG. 1, and FIG. 3 is a detailed diagram of another part of the device shown in FIG. Detailed Diagram FIG. 4 is a general diagram of another embodiment of the device according to the invention. (10a), (10h) are light sources, (12a)
), (12h) is the beam, (14a),
(14b) is a modulator, (18a). (18b) is a combination refractor, (24), (26
) is a mirror, (28) is a translucent plate, (30) is a carriage,
(32) is a mirror, (34) is a converging lens, (36) is an afocal device, (38) is a micrometer type displacement block,
F is the focal point, Ta, Tb, Tc are the spots, zz is the optical axis,
φ is the cross-sectional diameter, al+ a2+ f is the focal length, Y
a and Yb are axes.

Claims (1)

Claims: 1. Creating an image on a photosensitive support, the support being simultaneously scanned by at least two modulated beams directed at the photosensitive support in the form of spots by a converging lens. wherein the method comprises the steps of individually modulating each beam, directing the beam to the lens parallel to and symmetrically spaced on either side of the optical axis of the lens, and finally bringing the focal point of the lens to the A method of producing an image on a photosensitive support, comprising the step of positioning said lens so as to extend beyond the surface of the support. 2. Claims in which the beam is initially directed to coincide with the optical axis of the lens and then both beams are refracted by an equal amount parallel to each other and opposite to their initial direction. A method for producing an image on a photosensitive support according to paragraph 1. 3. Prior to scanning, the width of the spot is adjusted by adjusting the distance from the support to the lens, and the spacing of the spot adjusts the distance of the beam on either side of the optical axis of the lens. A method for producing an image on a photosensitive support according to claim 1 or 2, which is prepared by: 4. The beam is separated by guiding the beam through a pair of transparent plates having parallel surfaces tilted at equal angles in opposite directions on both sides of the optical axis of the lens. A method for producing an image on a photosensitive support according to any one of clauses 3 to 6. 5. The number of the beams is 2N, and the beams are guided to the lens in pairs parallel to the optical axis of the lens and symmetrically spaced on both sides of the optical axis of the lens. ,
5. A method of producing an image on a photosensitive support according to any one of claims 1 to 4, wherein the separation distance between successive pairs increases sequentially. 6. A method for producing an image on a photosensitive support according to claim 5, wherein a (2N+1)th beam is provided and directed along the optical axis of the lens. 7. A method for producing an image on a photosensitive support, wherein said support is scanned simultaneously by at least two modulated beams directed at said support in the form of spots by a converging lens, said method modulating each beam individually, directing the beams toward the lens parallel to and symmetrically spaced on either side of the optical axis of the lens, and finally bringing the focus of the lens beyond the surface of the support. 1. An apparatus for carrying out a method for producing an image on a photosensitive support, characterized in that the method comprises the step of: positioning said lens so as to focus said beams, said apparatus comprising: means for producing at least two beams; An apparatus comprising means for individually modulating the beam as a function of a modulation signal and means for directing said beam in the form of a spot on a photosensitive support by means of a converging lens, said apparatus comprising means for directing said beam in the form of a spot on a photosensitive support, said apparatus Apparatus for producing an image on a photosensitive support, characterized in that it has means for positioning in symmetrically spaced relationship on both sides and means for adjusting the distance between said lens and said support. 8. means for positioning said beam in a symmetrically spaced relationship parallel to and on either side of the optical axis of said lens;
A pair of transparent plates each having parallel surfaces through which the beam passes, mounted for rotation about an axis perpendicular to the beam, and together driven in equal and opposite rotation by a micrometer type device. 8. An apparatus for producing an image on a photosensitive support as claimed in claim 7. 9. A method for creating an image on a photosensitive support according to claim 7 or 8, comprising an afocal device placed in the optical path of the beam and changing the cross section of the beam to a predetermined ratio. and equipment. 10, the number of beams is 2N and N with parallel surfaces
9. A method and apparatus for producing an image on a photosensitive support according to claim 8, comprising a pair of transparent plates. 11. A method and apparatus for creating an image on a photosensitive support as claimed in claim 10, wherein a (2N+1)th beam is provided and directed along the optical axis of the lens.