JP4462809B2 - Scanning imaging lens, image writing method, and image writing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a scanning imaging lens, an image writing method, and an image writing apparatus.
[0002]
[Prior art]
Red, green, and blue light beams are simultaneously deflected by a common polygon mirror, and each color deflected light beam is condensed as a light spot on a color photographic paper by a common scanning imaging lens. 2. Description of the Related Art Image writing apparatuses that perform color image writing by modulating a light beam with image information of a corresponding color are known.
[0003]
In this type of image writing apparatus, if the scanning imaging lens has chromatic aberration of magnification, the “light scanning length”, which is the length of one line scanned by the light beam, differs for each color light beam. The light spots for writing are also shifted from each other.
[0004]
Such an optical scanning length or a shift between the light spots deteriorates the image quality of the formed color image.
[0005]
As a measure for avoiding such a problem of “displacement”, for example, as proposed in Japanese Patent Laid-Open No. 7-191261, there is a method of “using a scanning imaging lens in which lateral chromatic aberration is well corrected”. If the chromatic aberration of magnification is corrected sufficiently satisfactorily, the number of lenses increases, and the space that the scanning imaging lens occupies in the image writing device increases, resulting in an increase in the size of the device, and an increase in cost. is there.
[0006]
By accepting the presence of lateral chromatic aberration in the scanning imaging lens and setting the frequency of the clock for modulating each color light beam as a unique frequency for each light beam, it is possible to align the above "light scanning length" It is disclosed in JP-A-9-11538. Although this method certainly eliminates the “shift in optical scanning length”, it does not take into account the “difference in fθ characteristics with respect to each color light beam” due to the wavelength difference. The “shift” is not resolved.
[0007]
Japanese Patent Application Laid-Open No. 11-88619 discloses a method for eliminating the optical scanning length shift and the light spot shift so that the chromatic aberration of magnification in the scanning imaging lens is “same for red light and blue light” and green. A method of adjusting the clock frequency for the red light beam and the blue light beam based on the clock frequency for the light beam is disclosed.
[0008]
  thisMethodHowever, in order to make the chromatic aberration of magnification in the scanning imaging lens “same for red light and blue light”, the problem of an increase in the number of lenses and an increase in cost cannot be solved sufficiently.
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the circumstances described above, and is capable of satisfactorily correcting the deviation of the optical scanning length and the deviation of the optical spot, and a novel scanning imaging that can be realized at low cost. The objective is to realize a lens.
[0010]
Another object of the present invention is to realize a novel image writing method and apparatus capable of performing good image writing by effectively correcting the deviation of the optical scanning length and the deviation of the light spot using such a scanning imaging lens.
[0011]
[Means for Solving the Problems]
  The scanning imaging lens according to the present invention is “a light beam of each of the three primary colors A, B, and C simultaneously deflected by a common light deflecting means is reflected by a common scanning imaging lens.Same photosensitive recording medium (color photographic paper)A scanning imaging lens used in an image writing apparatus that performs color scanning by focusing light beams as light spots and modulating each color light beam with image information of the corresponding color. It is characterized by the following points.
[0012]
  That is,Reference color: relative to the lateral chromatic aberration of A, color: B, color: C lateral chromatic aberration: CD _BA , CD _CA However, the chromatic aberration of magnification has been corrected so as to be linear changes with different inclinations with respect to the image height: H,When the constant velocity characteristics for each color light beam are A (H), B (H), and C (H) with respect to the image height: H, these are:Chromatic aberration of magnificationAnd when A (H) is used as a reference, K_AB, Where KAC is a constantAbbreviation, A (H) = K_AB・ B (H) and A (H) = K_AC-The constant velocity characteristics are corrected so that C (H) is satisfied.
[0013]
  The “photosensitive recording medium” is, for example, the color photographic paper, and the three primary colors: A, B, and C can write a color image on such a recording medium.3 colors, ieIt is green, red, and blue which will be described later.
[0014]
  “Light deflecting means” is a device that rotates the deflecting / reflecting surface at a constant speed, such as a polygon mirror, a rotating mirror, and a rotating mirror.used. Therefore, the “constant velocity characteristic” is an fθ characteristic.
[0015]
  The scanning imaging lens according to claim 1.In the three primary colors: A, B and C are green, red and blue, respectively.Scan imaging lensThe lens is composed of a plurality of lenses including a lens having a positive refractive power in the main scanning direction and a lens having a negative refractive power in the main scanning direction. Number: νdp, Abbe number with respect to d-line of lens material having negative refractive power: νdn is a condition:
  (1) νdp ≧ 55
  (2) It is preferable to satisfy νdn ≦ 31 (Claim 2).
[0016]
  Claim 2As shown in FIG. 3, the scanning imaging lens includes a first group and a second group in order from the common light deflection unit side to the photosensitive recording medium side. The group is “three lenses L whose refractive power in the main scanning direction is negative, positive, positive in order from the side of the light deflection means”.₁₁, L₁₂, L₁₃The second group is “a long toroidal lens L that is long in the main scanning direction.₂And having a function of correcting curvature of field in the sub-scanning direction and having no effective refractive power in the main scanning direction ”(Claim 3).
[0017]
  Claim 2As shown in FIG. 4, the scanning imaging lens includes a first group and a second group in order from the common light deflecting means side to the photosensitive recording medium side. One group is “three lenses L whose refractive power in the main scanning direction is positive, negative, positive in order from the side of the light deflection means”.₁₁', L₁₂', L₁₃The second group is composed of a long toroidal lens L that is long in the main scanning direction.₂', Which has a function of correcting curvature of field in the sub-scanning direction and has no effective refractive power in the main scanning direction ”(Claim 4).
[0018]
  theseClaim 3,For any of the four types, a positive chromatic aberration is generated by a lens having a positive refractive power and a negative chromatic aberration is generated by a lens having a negative refractive power, respectively. Can take.
[0019]
  Claim 3 or 4The scanning imaging lens described can also be “having a geometrically optically conjugate relationship between the deflection starting point by the light deflecting means and the position of the photosensitive recording medium” in the sub-scanning direction (Claim 5In this case, the first group is rotationally symmetric with respect to the optical axis, and the incident side surface of the second group of long toroidal lenses is a “Y toroidal surface” whose rotational axis is parallel to the main scanning direction. The side surface may be an “X toroidal surface” whose rotation axis is parallel to the sub-scanning direction (Claim 6).
[0020]
By using the first group as a lens that is rotationally symmetric with respect to the optical axis, the lens processing time can be reduced, and the cost of manufacturing the lens can be reduced.
[0021]
  According to the image writing method of the present invention, “light beams of the three primary colors A, B, and C simultaneously deflected by a common light deflecting means are irradiated onto a common photosensitive recording medium by a common scanning imaging lens. A method of performing color scanning by condensing as a spot, performing optical scanning, and modulating each color light beam with image information of the corresponding color.Characterized by the following points.
  That is, as a scanning imaging optical systemClaims 1-6Any one of 1 is used.
[0022]
Also, the frequency of the clock that modulates each color light beam is F_A, F_B, F_CWhen these are made different from each other, the frequency in the reference color A light beam: F_AOn the other hand, the frequency for the B color light beam: F_BF_A・ K_AB, Frequency for C light beam: F_CF_A・ K_ACAs described above, the color spot writing and the optical scanning length of each color light beam are substantially matched with each other to write a color image.
[0023]
Clock frequency for each color light beam: F_A, F_B, F_CAre different from each other, but they are set uniformly, so that the frequency of the clock is always constant when optical scanning of each color light beam is performed.
[0024]
  Claim 7The image writing method ofAs aboveAs a scanning imaging lensClaims 1-6The three primary colors for writing a color image using the one described in any one of: green, red, and blue light beams are deflected at a constant angular velocity by a common light deflecting means.Do.
[0025]
  An image writing apparatus according to the present invention includes a light source unit, a modulation unit, a clock generation unit,With light deflection meansA scanning imaging lens, and the scanning imaging lens isClaims 1-6Of any one of (Claim 8).
[0026]
The “light source unit” emits light beams of three primary colors: A, B, and C for writing a color image.
The “modulation means” modulates each color light beam according to image information of a corresponding color.
The “clock generator” individually generates a clock for modulating each color light beam by the modulator for each light beam.
[0027]
The “light deflecting means” is for deflecting each color light beam, and is common to each color light beam.
[0028]
  The “scanning imaging lens” is a photosensitive recording medium that converts each color light beam deflected by light deflecting means.Is color photographic paperThe light is condensed as a light spot on the top. Therefore, it is common to each color light beam.
[0029]
The frequency of the clock that modulates each color light beam is F_A, F_B, F_CAre different from each other, and the frequency of the reference A color light beam: F_AOn the other hand, the frequency for the B color light beam: F_BIs F_A・ K_AB, Frequency for C light beam: F_CIs F_A・ K_ACAs described above, the color spot is set uniformly, and the light spot position and the light scanning length of each color light beam are substantially matched with each other to write a color image.
[0030]
  That is,The image writing device is described as “Three primary colors for writing a color image: common light deflecting means for simultaneously deflecting light beams of green, red, and blue. As a scanning imaging lensClaims 1-6Any one ofUse ".
[0031]
  This image writing deviceHas a "line image imaging means for forming each color light beam from the light source section as a long line image in the main scanning direction in the vicinity of the position of the deflecting reflection surface of the common light deflection means" as a scanning imaging lens.Claim 5 or 6It can be configured using the described one (Claim 9).
[0032]
  A little supplementary explanation.
  In general, “constant velocity characteristic: E (H)” is an image height of an actual light spot in optical scanning when the light spot speed is V when an ideal constant velocity is realized.: Htime: TFunction: When H (t), H (t) −(Vt)"V · t(Product of speed and time)”
  E (H) = {H (t) − (V · t)} / (V · t)
Given in. From this, H (t) is as follows.
[0033]
  H (t) =E (H) ・ V ・ t + V ・ t
  Since the speed of the light spot on the recording medium is dH (t) / dt,
  dH (t) / dt =V · t・ DE (H) / dH ・(DH / dt)+ E (H) ・ V + V
However, since the constant velocity characteristic: E (H) is generally on the order of several percent, dE (H) / dH in the first term on the right side is very small and can be substantially ignored.
[0034]
Therefore,
dH (t) / dt = E (H) · V + V
It becomes.
[0035]
For simplicity, it is assumed that the constant velocity characteristic is symmetric with respect to the image height of the light spot: 0.
Then the integration of both sides of the above formula:
∫ {dH (t) / dt} dt = ∫E (H) · Vdt + ∫Vdt
Considering that V is constant and Vdt = dH, integration: 積分 Vdt = L₀If you put / 2, the right side of this expression is
∫E (H) dH + L₀/ 2
It becomes. This formula was doubled
2∫E (H) dH + L₀
Is the length of one line: L, L₀Gives the optical scanning length when optical scanning is performed with ideal constant velocity characteristics.
[0036]
Let N be the number of dots when one line (optical scanning length) is fully written.
Constant velocity characteristics with respect to the A color light beam: A (H) is used as a reference, and the length of one line when one line is written with N dots with the A color light beam, that is, the optical scanning length is L._ALet T be the time required to write one line. Then, the frequency of the clock in this case is given by “N / T”.
[0037]
  When N dots are written with a B-color light beam, the optical scanning length is L when one line is written with the clock frequency being the above N / T._BSimilarly, when N dots are written with a C-color light beam, one line is written with the clock frequency being N / T.ofLight scanning length is L_CSuppose that
  When the scanning imaging lens of the present invention is used, LA ≠ LB ≠ LC.
[0038]
FIG. 2A illustrates this state in an explanatory manner. Colors: A, B, and C are shown as green (G), red (R), and blue (B), respectively, and the positions of the light spots are highlighted with an image height of 0, an intermediate image height, and a peripheral image height. . Optical scanning length: L_G, L_R, L_BIs the above L_A, L_B, L_CCorresponding to
[0039]
The light spot positions of the respective color light beams match only at the image height: 0, and at other image heights, the positions of the light spots having different colors are shifted from each other, and the light scanning length: L_G, L_R, L_BAre different from each other.
[0040]
When the above consideration is performed for the A color light beam, the B color light beam, and the C color light beam,
2∫A (H) dH + L₀= L_A
2∫B (H) dH + L₀= L_B
2∫C (H) dH + L₀= L_C
Is obtained. As mentioned above, between A (H), B (H), and C (H)
A (H) = K_AB・ B (H) and A (H) = K_AC・ C (H)
The above formula is
2∫A (H) dH + L₀= L_A
2∫B (H) dH + L₀= L_B= 2A (H) dH / K_AB+ L₀
2∫C (H) dH + L₀= L_C= 2A (H) dH / K_AC+ L₀
And L_A-L₀= ΔL_A, L_B-L₀= ΔL_B, L_C-L₀= ΔL_CThen, ΔL_B= ΔL_A・ K_AB, ΔL_C= ΔL_A・ K_ACIt becomes.
[0041]
Since the number of dots in one line is N, the clock frequency is set to N / T per A color light beam._A(= F_A), B / B light beam, N / T_B(= F_B), N / T with C color light beam_C(= F_C), The length of one line, which is the length of N dots by the A, B, and C color light beams, is the same, ΔL, which is an error of one line length according to the constant velocity characteristics._A, ΔL_B, ΔL_CΔL_B, ΔL_CIs the reference ΔL_AF to be equal to_B, F_CCan be set, which is F_B= F_A・ K_AB, F_C= F_A・ K_ACCan be realized.
[0042]
  Note that the constant velocity characteristics for each color light beam: A (H), B (H), and C (H) are different from each other due to the chromatic aberration of magnification.Abbreviation,
  A (H) = K_AB・ B (H) and A (H) = K_AC・ C (H)
Is satisfied, color: B, color: C magnification chromatic aberration: CD relative to the reference color: A magnification chromatic aberration_BA, CD_CAHowever, it is only necessary that the image heights are linear changes with different inclinations.
[0043]
FIG. 2B shows a state in which such correction by adjusting the “clock frequency for each color light beam” is performed, as an explanatory diagram. The positions of the light spots having different colors substantially match each other at the entire image height, and the light scanning lengths also match each other. In other words, in the present invention, the positional deviation between the light spots of different colors and the deviation of the optical scanning length are corrected by an electrical means called clock frequency adjustment. This is equivalent to adjusting the magnification by changing the focal length of the scanning imaging lens for each color.
[0044]
Usually, in a scanning imaging lens (fθ lens) when using a light source of a single wavelength, in order to improve beam imaging performance, a lens having a positive refractive power is made of a material having a small Abbe number, that is, a high refractive index. Use.
[0045]
4. The scanning imaging lens according to claim 3, wherein a difference in lateral chromatic aberration with respect to red (R), green (G), and blue (B) light beams is controlled (as described above, a reference color: G lateral chromatic aberration). Relative chromatic aberration of color: R, color: B relative to_RG, CD_BGTherefore, a lens having a positive refractive power and a material having a large Abbe number, that is, a relatively low refractive index is used. In addition, a material having a small Abbe number is used for a lens having a negative refractive power.
[0046]
Abbe number: When the condition for νdp falls below 55, the lower limit of condition (1), the chromatic aberration of magnification of red (R) becomes too large for green (G, blue (B), and the difference in chromatic aberration of magnification is linear. In addition, when the condition regarding the Abbe number: νdn exceeds the upper limit of 31 of the condition (2), the chromatic aberration of magnification of red (R) increases with respect to green (G) and blue (B). Thus, the difference in chromatic aberration of magnification cannot be kept linear.
[0047]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments will be described.
FIG. 1A shows an embodiment of an image writing apparatus.
This image writing device is a “color photographic negative image device for writing a color image”, and the three primary colors for writing a color image from the light source devices 1, 2, and 3 constituting the “light source unit”: Each color light beam (laser beam) of red (R wavelength: 690 nm), green (G wavelength: 532 nm), and blue (B wavelength: 473 nm) is emitted.
[0048]
Each of these color light beams is modulated in accordance with image information of the corresponding color (R, G, B) by optical modulators 4, 5, 6 constituting "modulation means". Since a color photographic negative image apparatus requires fine image writing, the light source device does not perform modulation, and light modulators 4 to 6 other than the light source unit are provided. In this embodiment, the optical modulators 4 to 6 are AO modulators that perform modulation by optical path deflection using diffraction.
[0049]
As shown in FIG. 1B, each color light beam is output by the light modulators 4, 5, 6 according to the color image information: R, G, B input from the clock generating unit 20 to the image signal applying unit 21. Are individually generated for each light beam.
[0050]
Frequency of each clock: F_R, F_G, F_BIs the fθ characteristic which is a constant speed characteristic in the scanning imaging lens: relationship between G (H), R (H) and B (H): G (H) = K_GR・ R (H), G (H) = K_GB・ Based on B (H): F_R= F_G・ K_GR, F_B= F_G・ K_GBAre set uniformly.
[0051]
Each color light beam modulated by the light modulators 4, 5 and 6 is reflected by the mirror 7, passes through the spherical lenses 9, 10 and 11, respectively, and passes through the cylindrical lenses 13, 14 and 15 as line image imaging means. The light is reflected by the mirror 8 while converging in the sub-scanning direction by the action, and is incident on the deflection reflection surface (deflection surface in FIGS. 3 and 4) of the polygon mirror of the rotary polygon mirror 16 as the light deflection means, and near the deflection reflection surface. An image is formed at the same position as a “line image long in the main scanning direction”.
[0052]
The red light beam having a long wavelength is made incident on the cylindrical lens 13 after the beam expander 12 expands the beam diameter in order to match the spot diameter with the light spot of the green / blue light beam having a short wavelength.
[0053]
The polygon mirror has a deflecting reflection surface number of 6 and an inscribed circle radius of 18 mm. Each color light beam reflected by the deflecting reflecting surface by the constant-speed rotation of the polygon mirror is deflected at an equal angular velocity, transmitted through the scanning imaging lens, and the surface to be scanned 18 (substantially photosensitive) by the action of the lens. A light spot (spot diameter of 10 μm to 100 μm) is condensed on a color photographic paper as a recording medium, and the image is written by optical scanning by moving on substantially the same line (scanning line). Each color light beam is detected by the photodetector 19 prior to optical scanning, and the start of optical scanning by each color light beam is synchronized based on the detection signal.
[0054]
The scanning imaging lens is constituted by a first group 17-1 and a second group 17-2, and is according to any one of claims 3 to 7.
[0055]
  That is, the image writing apparatus shown in FIG. 1 indicates that “light sources 1, 2, 3 that emit light beams of three primary colors: A, B, C (G, R, B) for writing a color image; The modulation means 4, 5, 6 for modulating each color light beam in accordance with the image information of the corresponding color, and the clock for modulating each color light beam by this modulation means are individually generated for each light beam. The clock generating means 20, the light deflecting means 16 common to each color light beam for deflecting each color light beam, and each color light beam deflected by this light deflecting means as a light spot on the photosensitive recording medium Each of which has a scanning imaging lens for focusing, and the scanning imaging lensClaim 5 or 6When the frequency of the clock for modulating each color light beam is FG, FR, and FB, they are different from each other. The frequency of the reference green light beam: FG, and the frequency of the red light beam: FR is set to FG / KGR, frequency for C color light beam: FB is set to FG / KGB, respectively, and the light spot position and the optical scanning length by each color light beam are substantially matched to each other to write a color image. Perform image writingDevice.
[0056]
  Further, the image writing apparatus of FIG. 1 indicates that “the three primary colors for writing a color image: common light deflecting means 16 for simultaneously deflecting light beams of green, red and blue, It is deflected at a constant angular velocity by constant speed rotation.Yes, light source 1, 2, 3Scanning image forming lenses having line image forming means 13, 14, 15 for forming light beams from the respective color beams as long line images in the main scanning direction in the vicinity of the position of the deflecting reflection surface of the common light deflecting means 16. AsClaim 5 or 6Using the described oneIs a thing.
[0057]
  Therefore, according to the image writing apparatus in FIG. 1, the light beams of the three primary colors A, B, and C (G, R, and B) for writing the color image are deflected by the common light deflecting unit 16; A method of performing color image writing by optically scanning the recording medium by condensing each light spot on a photosensitive recording medium by a scanning imaging lens.Thus, an image writing method is performed in which a color image is written by substantially matching the light spot position and the optical scanning length of each color light beam.
[0058]
  Further, this image writing method uses a light beam of three primary colors: green, red, and blue for writing a color image at a constant angular velocity by a common light deflecting means 16.To be deflected.
[0059]
【Example】
Hereinafter, six specific examples relating to the scanning imaging lens used in the image writing apparatus shown in FIG. 1 will be described.
[0060]
As shown in FIGS. 3 and 4, the radius of curvature of the i-th lens surface in order from the light deflection means side (left side of the figure) to the surface to be scanned is set to R in the main scanning direction._iY, R per sub-scanning direction_iX, The distance between the i-th lens surface and the (i + 1) -th lens surface on the optical axis is D_iAnd Further, the refractive index and Abbe number of the material of the “jth lens” counted from the light deflecting means side with respect to the d-line are expressed as Nd._j, Νd_jAnd The unit of the quantity having the length dimension is “mm”.
[0061]
Example 1
i R_iY       R_iX        D_i     j Nd_j    νd_j      Remarks
0 45.78
1 -128.385 -128.385 5.22 1 1.58400 30.8
2 2321.7 2321.7 3.5
3 -4747.9 -4747.9 21.17 2 1.51680 64.2
4 -78.736 -78.736 3.5
5 281.662 281.662 10.53 3 1.52996 55.8
6 1100 1100 107.32
7 -700 -54.4 3 4 1.58400 30.8 Y toroidal surface
8 -700 -28.39 167.366 X toroidal surface
Writing width: 305mm
Red (R) focal length: 260.497mm
Green (G) focal length: 260mm
Blue (B) focal length: 259.793 mm
These focal lengths are values corrected by correcting the clock frequency.
[0062]
Example 2
i R_iY       R_iX        D_i     j Nd_j    νd_j      Remarks
0 69.613
1 -250.786 -250.786 7.872 1 1.80518 25.5
2 ∞ ∞ 7.432
3 ∞ ∞ 24.875 2 1.51680 64.2
4 -106.17 -106.17 4.852
5 378.043 378.043 16.203 3 1.51680 64.2
6 -1944.546 -1944.546 150
7 -700 -54.4 3 4 1.58400 30.8 Y toroidal surface
8 -700 -26.2 119.08 X toroidal surface
Writing width: 305mm
Red (R) focal length: 260mm
Green (G) focal length: 259.453 mm
Blue (B) focal length: 259.276 mm
These focal lengths are values corrected by correcting the clock frequency.
[0063]
Example 3
i R_iY       R_iX        D_i     j Nd_j    νd_j      Remarks
0 53.216
1 -219.01 -219.01 7.713 1 1.80518 25.5
2 ∞ ∞ 3.068
3 ∞ ∞ 24 2 1.60311 60.7
4 -111.788 -111.788 9.448
5 351.102 351.102 15.906 3 1.51680 64.2
6 -4239.016 -4239.016 150
7 -700 -54.4 3 4 1.58400 30.8 Y toroidal surface
8 -700 -26.2 113.993 X toroidal surface
Writing width: 305mm
Red (R) focal length: 260mm
Green (G) focal length: 259.569 mm
Blue (B) focal length: 259.43 mm
These focal lengths are values corrected by correcting the clock frequency.
[0064]
  Examples 1-3 above are as follows:Scanning imaging lens shown in FIG.It is the Example regarding.
[0065]
Example 4
i R_iY       R_iX        D_i     j Nd_j    νd_j      Remarks
0 60.656
1 -494.031 -494.031 17.787 1 1.51680 64.2
2 -134.758 -134.758 3
3 ∞ ∞ 9.065 2 1.80518 25.5
4 411.17 411.17 13.113
5 353.07 353.07 25 3 1.51680 64.2
6 -386.957 -386.957 80
7 -700 -57.4 3 4 1.58400 30.8 Y toroidal surface
8 -700 -30.11 181.223 X toroidal surface
Writing width: 330mm
Red (R) focal length: 280mm
Green (G) focal length: 279.531 mm
Blue (B) focal length: 279.364 mm
These focal lengths are values corrected by correcting the clock frequency.
[0066]
Example 5
i R_iY       R_iX        D_i     j Nd_j    νd_j      Remarks
0 57.49
1 -800.183 -800.183 16.112 1 1.51680 64.2
2 -137.135 -137.135 3
3 ∞ ∞ 8.063 2 1.80518 25.5
4 347.077 347.077 15.704
5 324.817 324.817 25 3 1.51680 64.2
6 -331.929 -331.929 70
7 -700 -57.4 3 4 1.58400 30.8 Y toroidal surface
8 -700 -29 169.983 X toroidal surface
Writing width: 305mm
Red (R) focal length: 260mm
Green (G) focal length: 259.592 mm
Blue (B) focal length: 259.466 mm
These focal lengths are values corrected by correcting the clock frequency.
[0067]
Example 6
i R_iY       R_iX        D_i     j Nd_j    νd_j      Remarks
0 62.006
1 -1011.161 -1011.161 11.698 1 1.48749 70.4
2 -150.186 -150.186 7.192
3 ∞ ∞ 9.197 2 1.80518 25.5
4 391.613 391.613 18.217
5 372.443 372.443 25.694 3 1.48749 70.4
6 -245.843 -245.843 150
7 -700 -57.4 3 4 1.58400 30.8 Y toroidal surface
8 -700 -22.1 87.214 X toroidal surface
Writing width: 305mm
Red (R) focal length: 260mm
Green (G) focal length: 259.612 mm
Blue (B) focal length: 259.511 mm
These focal lengths are values corrected by correcting the clock frequency.
[0068]
  Examples 4-6 above areScanning imaging lens shown in FIG.It is the Example regarding.
[0069]
FIG. 5 shows the fθ characteristic as the constant velocity characteristic of the scanning imaging lens of Example 1. R is red, G is green, and B is blue. FIG. 6 shows a state in which the frequency of the clock for each color light beam is corrected for the scanning imaging lens of Example 1 and the fθ characteristic is substantially matched with the reference fθ characteristic. FIG. 7 is a diagram showing chromatic aberration of magnification relative to red and blue green of the scanning imaging lens of Example 1. FIG. 8 is a diagram illustrating correction of relative chromatic aberration of magnification in FIG. 7 by correcting the clock frequency. The following is shown.
[0070]
FIG. 9 shows the fθ characteristic as the constant speed characteristic of the scanning imaging lens of Example 2 in accordance with FIG. FIG. 10 shows a state in which the frequency of the clock for each color light beam is corrected for the scanning imaging lens of Example 2 so that the fθ characteristic is substantially matched with the reference fθ characteristic. FIG. 11 is a diagram illustrating chromatic aberration of magnification relative to red and blue green of the scanning imaging lens of Example 2, and FIG. 12 is a diagram illustrating correction of relative chromatic aberration of magnification in FIG. 11 by correcting the clock frequency. The following is shown.
[0071]
FIG. 13 shows the fθ characteristic as the constant velocity characteristic of the scanning imaging lens of Example 3 in a manner similar to FIG. FIG. 14 shows a state in which the frequency of the clock for each color light beam is corrected for the scanning imaging lens of Example 3 so that the fθ characteristic is substantially matched with the reference fθ characteristic. FIG. 15 is a diagram showing chromatic aberration of magnification relative to red and blue green of the scanning imaging lens of Example 3. FIG. 16 is a diagram illustrating correction of relative chromatic aberration of magnification in FIG. 15 by correcting the clock frequency. The following is shown.
[0072]
FIG. 17 shows the fθ characteristic as the constant speed characteristic of the scanning imaging lens of Example 4 in a manner similar to FIG. FIG. 18 shows a state in which the frequency of the clock for each color light beam is corrected for the scanning imaging lens of Example 4 so that the fθ characteristic is substantially matched with the reference fθ characteristic. FIG. 19 is a diagram showing chromatic aberration of magnification relative to red and blue green of the scanning imaging lens of Example 4. FIG. 20 is a diagram illustrating correction of relative chromatic aberration of magnification in FIG. 19 by correcting the clock frequency. The following is shown.
[0073]
FIG. 21 shows the fθ characteristic as the constant speed characteristic of the scanning imaging lens of Example 5 in a manner similar to FIG. FIG. 22 shows a state in which the frequency of the clock for each color light beam is corrected for the scanning imaging lens of Example 5 and the fθ characteristic is substantially matched with the reference fθ characteristic. FIG. 23 is a diagram showing chromatic aberration of magnification relative to red and blue green of the scanning imaging lens of Example 5, and FIG. 24 is a diagram illustrating correction of relative chromatic aberration of magnification in FIG. 23 by correcting the clock frequency. The following is shown.
[0074]
FIG. 25 shows the fθ characteristic as the constant speed characteristic of the scanning imaging lens of Example 6 in a manner similar to FIG. FIG. 26 shows a state in which the frequency of the clock for each color light beam is corrected for the scanning imaging lens of Example 6 so that the fθ characteristic is substantially matched with the reference fθ characteristic. FIG. 27 is a diagram showing chromatic aberration of magnification relative to red and blue green of the scanning imaging lens of Example 6. FIG. 28 is a diagram illustrating correction of relative chromatic aberration of magnification in FIG. 27 by correcting the clock frequency. The following is shown.
[0075]
As is apparent from FIGS. 8, 12, 16, 20, 24, and 28, after correction by adjusting the frequency field of the clock, the positional deviation of the red and blue light spots relative to the green light spot is at most. Considering that the diameter of the light spot is 10 μm or less and the normal light spot diameter is about several tens to 100 μm, the positional deviation between the light spots is “one-fifth or less” of 1 dot size, It is possible to effectively reduce the image quality degradation caused by the color image.
[0076]
【The invention's effect】
As described above, according to the present invention, a novel scanning imaging lens, image writing method, and image writing apparatus can be realized. The scanning imaging lens of the present invention is based on the chromatic aberration of magnification with respect to light of a desired color, and the chromatic aberration of magnification of other colors relative to the reference chromatic aberration of magnification is “linear with different inclinations”. Thus, the constant velocity characteristics for each color light beam can have a certain ratio to each other. Therefore, in the image writing method and the image writing apparatus using the same, the two color light beams other than the reference color light beam are used. By simply correcting the frequency of the clock that modulates the light, it is possible to correct the deviation in the optical scanning length and also to correct the positional deviation between the light spots.
[0077]
Also, making the chromatic aberration of magnification of other colors relative to the reference chromatic aberration of chromaticity “a linear shape with different inclinations” is comparable to making the relative chromatic aberration of magnification of other colors the same. Therefore, the scanning imaging lens of the present invention can be easily realized at low cost.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an embodiment of an image writing apparatus.
FIG. 2 is a diagram for explaining correction of a shift in optical scanning length and a shift between light spots.
[Fig. 3]Example of lens configuration of scanning imaging lensIt is a figure for demonstrating.
[Fig. 4]Other examples of the lens configuration of the scanning imaging lensIt is a figure for demonstrating.
5 is a diagram illustrating fθ characteristics of red (R), green (G), and blue (B) of the scanning imaging lens of Example 1. FIG.
6 is a diagram in which the fθ characteristic for each color light beam is substantially matched by adjusting the clock frequency in image writing using the scanning imaging lens of Embodiment 1. FIG.
7 is a graph showing chromatic aberration of magnification relative to red and blue green in the scanning imaging lens of Example 1. FIG.
FIG. 8 is a diagram showing a state after correcting the relative lateral chromatic aberration of FIG. 7 by correcting the clock frequency.
FIG. 9 is a diagram illustrating fθ characteristics with respect to red (R), green (G), and blue (B) of the scanning imaging lens of Example 2;
10 is a diagram in which fθ characteristics for each color light beam are substantially matched by adjusting a clock frequency in image writing using the scanning imaging lens of Embodiment 2. FIG.
11 is a graph showing chromatic aberration of magnification relative to red and blue green in the scanning imaging lens of Example 2. FIG.
12 is a diagram showing the result after correcting the relative lateral chromatic aberration in FIG. 11 by correcting the frequency of the clock.
13 is a diagram illustrating fθ characteristics with respect to red (R), green (G), and blue (B) of the scanning imaging lens of Example 3. FIG.
14 is a diagram in which the fθ characteristic for each color light beam is substantially matched by adjusting the clock frequency in image writing using the scanning imaging lens of Example 3. FIG.
15 is a graph showing chromatic aberration of magnification relative to red and blue green in the scanning imaging lens of Example 3. FIG.
FIG. 16 is a diagram showing a state after correcting the relative lateral chromatic aberration of FIG. 15 by correcting the clock frequency.
FIG. 17 is a diagram illustrating fθ characteristics with respect to red (R), green (G), and blue (B) of the scanning imaging lens of Example 4;
FIG. 18 is a diagram in which the fθ characteristic for each color light beam is substantially matched by adjusting the frequency of the clock in image writing using the scanning imaging lens of Example 4.
FIG. 19 is a diagram showing chromatic aberration of magnification relative to red and blue green in the scanning imaging lens of Example 4;
20 is a diagram showing the result of correcting the relative lateral chromatic aberration of FIG. 19 by correcting the clock frequency.
FIG. 21 is a diagram illustrating fθ characteristics with respect to red (R), green (G), and blue (B) of the scanning imaging lens of Example 5;
FIG. 22 is a diagram in which the fθ characteristic for each color light beam is substantially matched by adjusting the clock frequency in image writing using the scanning imaging lens of Example 5.
23 is a graph showing chromatic aberration of magnification relative to red and blue green in the scanning imaging lens of Example 5. FIG.
24 is a diagram showing the result of correcting the relative lateral chromatic aberration of FIG. 23 by correcting the clock frequency.
25 is a graph showing fθ characteristics of red (R), green (G), and blue (B) of the scanning imaging lens of Example 6. FIG.
FIG. 26 is a diagram in which the fθ characteristic for each color light beam is substantially matched by adjusting the frequency of the clock in image writing using the scanning imaging lens of Example 6.
FIG. 27 is a diagram showing chromatic aberration of magnification relative to red and blue green in the scanning imaging lens of Example 6;
FIG. 28 is a diagram showing the result after correcting the relative lateral chromatic aberration of FIG. 26 by correcting the clock frequency.
[Explanation of symbols]
1-3 Light source
4-6 Modulation means
20 Clock generation means
14 Light deflection means
17-1, 17-2 Scanning imaging lens

Claims (9)

Light beams of the three primary colors: A, B, and C simultaneously deflected by a common light deflecting means that rotates the deflecting reflecting surface at a constant speed are condensed as a light spot on the same color photographic paper by a common scanning imaging lens. A scanning imaging lens used in an image writing apparatus for performing color scanning by performing optical scanning and modulating each of the color light beams with image information of a corresponding color,
The above three primary colors: A, B and C are green, red and blue, respectively.
Reference color: relative to the lateral chromatic aberration of A, color: B, color: C lateral chromatic aberration: CD _BA and CD _CA are linear changes with different inclinations with respect to image height: H. The chromatic aberration of magnification is corrected so that
When the constant velocity characteristics for each color light beam are A (H), B (H), and C (H) with respect to the image height: H, these differ from each other due to chromatic aberration of magnification,
And when A (H) is used as a reference, K _AB and K _AC are assumed to be constants ,
Scanning imaging characterized by correcting the constant velocity characteristics so that A (H) = K _AB · B (H) and A (H) = K _AC · C (H) are satisfied. lens. The scanning imaging lens according to claim 1.
The lens is composed of a plurality of lenses including a lens having a positive refractive power in the main scanning direction and a lens having a negative refractive power in the main scanning direction. Number: νdp, Abbe number with respect to d-line of lens material having negative refractive power: νdn is a condition:
(1) νdp ≧ 55
(2) νdn ≦ 31
A scanning imaging lens characterized by satisfying The scanning imaging lens according to claim 2.
The first group and the second group are arranged in order from the common light deflecting means side to the photosensitive recording medium side,
The first group is composed of three lenses whose refractive power in the main scanning direction is negative, positive, and positive in order from the side of the light deflection means,
The second group is a long toroidal lens that is long in the main scanning direction, has a function of correcting curvature of field in the sub-scanning direction, and has no substantial refractive power in the main scanning direction. A scanning imaging lens. The scanning imaging lens according to claim 2.
The first group and the second group are arranged in order from the common light deflecting means side to the photosensitive recording medium side,
The first group is composed of three lenses whose refractive power in the main scanning direction is positive, negative, and positive in order from the side of the light deflection means,
The second group is a long toroidal lens that is long in the main scanning direction, has a function of correcting curvature of field in the sub-scanning direction, and has no substantial refractive power in the main scanning direction. A scanning imaging lens. The scanning imaging lens according to claim 3 or 4,
A scanning imaging lens characterized in that, in the sub-scanning direction, the origin of deflection by a common light deflecting means and the position of a photosensitive recording medium have a geometrically conjugate relationship. The scanning imaging lens according to claim 5.
The first group is rotationally symmetric with respect to the optical axis, the incident side surface of the second group of long toroidal lenses is a Y toroidal surface whose rotation axis is parallel to the main scanning direction, and the emission side surface is sub-scanned by the rotation axis. A scanning imaging lens characterized by an X toroidal surface parallel to the direction. The light beams of the three primary colors: A (green), B (red), and C (blue), which are simultaneously deflected by a common light deflecting unit that rotates the deflecting reflection surface at a constant speed, are made the same by a common scanning imaging lens. A method of writing a color image by condensing the light beam on a color photographic paper as a light spot, performing optical scanning, and modulating each color light beam with image information of a corresponding color,
The one according to any one of claims 1 to 6 is used as a scanning imaging optical system,
Further, when the frequency of the clock for modulating each color light beam is F _A , F _B , and F _C , these are made different from each other, and the frequency for the A color light beam as a reference: F _A for the B color light beam: By uniformly setting F _B as F _A · K _AB and the frequency for the C color light beam: F _C as F _A · K _AC , the light spot position and the light scanning length of each color light beam are substantially equal to each other. An image writing method characterized in that a color image is written in accordance with the above. A light source unit that emits light beams of three primary colors for writing a color image: A (green), B (red), and C (blue);
Modulation means for modulating each color light beam according to image information of a corresponding color;
A clock generating means for individually generating a clock for modulating each color light beam by the modulating means for each light beam;
A light deflector common to each color light beam for deflecting each color light beam;
Each color light beam deflected by the light deflecting means is condensed as a light spot on the same photosensitive recording medium, and has a scanning imaging lens common to each color light beam,
The light deflection means performs deflection by rotating the deflection reflection surface at a constant speed,
The scanning imaging lens is as defined in any one of claims 1 to 6,
When the frequency of the clock for modulating each color light beam is F _A , F _B , and F _C , these are different from each other, and the frequency for the reference A color light beam: F _{A and the} frequency for the B color light beam: F _B Is a frequency for F _A · K _AB and C color light beam: F _C is uniformly set as F _A · K _AC , and the light spot position and the optical scanning length by each color light beam are substantially matched to each other to obtain a color image An image writing apparatus for writing The image writing device according to claim 8.
Claims: As a scanning imaging lens, there is a line image imaging means for imaging each color light beam from the light source section as a long line image in the main scanning direction in the vicinity of the position of the deflection reflection surface of the common light deflection means. An image writing apparatus using the apparatus described in 5 or 6.

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