JPH11231216A - Ultra high color correction projection lens for pixel panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an improved projection lens for a pixelconversion panel, which has an ultra high degree of color correcting ability (color correction is sufficient including that of secondary colors), produces little distortion, and is moreover capable of operating (focusing) in a wide rage of magnification maintaining an effective combination with an output of an illumination system. SOLUTION: This projection lens is provided with a 1st lens unit U1 with a negative power and a 2nd lens unit U2 with a positive power. The 2nd lens unit U2 consists of a 1st sublens unit U2S1 having a positive or negative power, and a 2nd sub-lens unit having a positive power U2s2 . The 2nd sub-lens unit comprises at least three lens elements Lapd, Lapd 2, and the 1st lens element has a positive power, the 2nd lens element has a negative power, and the 3rd lens element has a positive power and an anomalous partial dispersion. With this composition, boht of the primary colors and secondary colors are corrected, lateral chromatic aberration becomes less than 40% of one pixel and axial chromatic aberration becomes not more than one pixel in a range of 470 nm to 630 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a projection lens, and more particularly to a projection lens.
The present invention relates to a projection lens that can be used to form an image of an object composed of pixels such as a CD.

[0002]

2. Description of the Related Art A projection lens device (hereinafter sometimes simply referred to as a "projection device") is used to form an image of an object on a screen. Such a projection lens device is divided into a front projection type and a rear projection type depending on whether the observer and the object are on the same side of the screen or on the opposite side, and when they are on the same side, the front projection type is used, When on the side, a rear projection type is used.

FIG. 5 shows the basic structure of such an apparatus. In FIG. 5, 10 is a light source (for example, a tungsten halogen lamp), 12 is an illumination optical system for forming an image of the light source (hereinafter, referred to as an “output” of the illumination system), and 14 is an object to be projected (for example, ON, Reference numeral 13 denotes a projection lens composed of a plurality of lens elements for forming an enlarged image of the object 14 on the screen 16. A field lens, for example, a Fresnel lens, may be arranged near the pixelated panel so that the exit pupil of the illumination system is appropriately located.

In the case of a front projection type (for example, Embodiments 1, 2, and 4 described later), an observer in FIG. 5 observes an image from the left side of a screen 16, and in a case of a rear projection type (for example, described later). Embodiment 3), the observer uses the screen 1
6. Observe the image from the right side of 6. In the case of a rear projection type housed in a single cabinet, a mirror is often used to bend the optical path to reduce the size of the entire apparatus.

A projection lens device whose object is a pixelated panel is used in various applications such as a data display device. In such a projection lens arrangement, it is desirable to use a single projection lens that forms an image of a single panel having, for example, red, green, and blue pixels. In some cases, for example, in a large image rear projection system, multiple panels and multiple projection lenses are used, with each set of panels and projection lenses forming part of the overall image. .

There is a need for a projection lens for a pixelated panel having at least the following characteristics.

(1) The color correction is extremely advanced, that is, the color correction including the color correction of the secondary color is sufficient.

(2) The distortion is small.

Further, it is desirable that the following characteristics are further provided depending on the use.

(3) Able to operate (focus) in a wide magnification (conjugate) range while maintaining efficient coupling with the output of the illumination system and advanced aberration correction. (Hereinafter, it is referred to as “focusing range of the lens.”) It is important that the color correction is extremely advanced. Chromatic aberrations are easily seen in the image of a pixelated panel as blurring of a pixel and, in severe cases, complete omission of that pixel. Generally, this problem is most pronounced at the edges of the field of view.

Although it is necessary to consider all chromatic aberrations of the apparatus, transverse chromatic aberration, color-based coma difference, and color-based astigmatism difference are generally particularly problematic. Lateral chromatic aberration,
That is, the difference in magnification depending on the color is a decrease in contrast,
It is particularly noticeable at the edges of the field of view, but is particularly troublesome as it appears. At worst, there is a rainbow effect throughout the field of view.

In the case of a projection apparatus using a cathode ray tube (CRT), for example, the size of an image formed on a red CRT surface is reduced on a blue CRT even if some horizontal chromatic aberration remains. It can be compensated electronically by making it smaller than what is done. However, in the case of a pixilated panel, the image is digitized and it is not possible to adjust the size smoothly over the entire field of view, so C
Compensation cannot be performed as in a projection device using an RT. Therefore, it is necessary that the lateral chromatic aberration of the projection lens be corrected to a higher degree.

In the final image, lateral color bleeding is caused not only by the difference between coma, distortion, and astigmatism due to color, but also by the lateral chromatic aberration itself. In contrast, axial color bleeding is caused by axial chromatic aberration itself and spherical chromatic aberration. In a conventional projection lens used with a pixelated panel, only primary lateral chromatic aberration and primary axial chromatic aberration are considered, and secondary lateral chromatic aberration and secondary axial chromatic aberration are not considered much.
As will be described later, the projection lens of the present invention focuses on this point.

[0014] The use of a pixelated panel for a data display increases the demands on distortion correction. This is because to view the data, a high image quality is required up to the end of the field of view of the lens. Needless to say, there are no distortions in the displayed numbers and letters,
It is as important at the edges of the field as it is at the center. In addition, the projection lens is often used with a plurality of panels that face each other, and the lenses of the first, second, and fourth embodiments are designed as such. In such a case, the distortion on the screen may not be symmetrical with respect to a horizontal line passing through the center of the screen, and may, for example, increase monotonically from the lower edge to the upper edge of the screen. This makes even small distortions easily visible to the observer. The fact that distortion is small and chromatic aberration is well corrected
This is especially important when an enlarged image of the “WINDOWS” interface is projected onto the screen. Its interface with parallel lines, bordered command boxes and dialog boxes, and complex coloring is essentially a distortion and chromatic test pattern. Even a small amount of distortion or chromatic aberration in the image of such an interface is noticeable to the user.

It is desirable that the above-mentioned characteristic (3), that is, that the lens can be efficiently operated in a wide magnification range (the lens has a wide focusing range). This is because a projection lens device having such characteristics can be used regardless of the size of the screen and the size of the hole without changing parts of the device. Only the conjugation between the object and the image needs to be changed,
It can be easily changed simply by moving the lens relative to the pixelated panel. The difficulty is maintaining efficient coupling to the output of the illumination system and high aberration correction over the entire operable magnification range.

All the projection lenses described below satisfy all the above-mentioned requirements, and a projection lens apparatus capable of forming a high-quality color image of a pixelated panel on a screen is manufactured at a relatively low cost. It can be used for:

The following patent discloses a projection lens for use with a pixelated panel. U.S. Pat. No. 4,189,211 to Taylor; U.S. Pat.
U.S. Patent No. 5,179,4 to Yano et al.
73, Moskovich U.S. Patent No. 5,200,861, N
o. 5,218,480; IIzuka et al., US Pat.
278,698, Betensky U.S. Patent No. 5,313,
330, U.S. Patent No. 5,331,462 to Yano.

For LCD devices, US Pat. No. 4,425,028 to Gagnon et al., US Pat.
61,542; Ledebuhr U.S. Pat.
11 and EPO Patent Publication Nos. 311 and 116.

[0019]

In view of the above circumstances, the present invention has both the above-mentioned characteristics (1) and (2) (preferably also has a characteristic (3)). It is an object to provide an improved projection lens for a pixelated panel.

[0020]

A projection lens according to the present invention has a power Po and a focal length fo, and (A) a first lens unit (U1) having a negative power P1, and (B) a positive lens unit (B). A second lens unit (U2) having power P2 from the image side to the object side (from the long conjugate side to the short conjugate side) in this order, and the first lens unit and the second lens unit The axial distance between is D12, and the second lens unit is (i)
First sub-lens unit having positive or negative power
(U2s1) and (ii) a second sub-lens unit (U2s2) having a positive power Ps2 in this order from the image side to the object side, and the first sub-lens unit of the second sub-lens unit The on-axis distance from the lens unit is Ds1s2, and the second
_{Is composed} of a lens element Lapd having an abnormal partial dispersion and a power P _Lapd .

[0021] The second sub-lens unit may include a plurality of lens elements having an abnormal partial dispersion. For example, FIG. 1 shows two lens elements having anomalous partial dispersion, that is, a lens element L of power P _Lapd.
lens element P _Lapd2 of apd and power P _Lapd2 (Table 6)
Has been shown to be used.

In a preferred embodiment, the projection lens of the present invention has at least some of the following characteristics.

(1) One or more lens elements having anomalous partial dispersion have positive power.

(2) One or more lens elements having abnormal partial dispersion have positive power,
The second sub lens unit has a negative lens element;
(L _N ) and a positive lens element (L _P ).

(3) The first lens unit has at least one aspherical surface.

(4) The first lens unit comprises one lens element.

(5) The first lens unit comprises only a plastic lens element, and the second lens unit comprises only a glass lens element.

(6) The second lens unit has only a spherical surface.

(7) The projection lens satisfies at least some of the following conditions.

(I) 0.3 <| P1 | / Po <1.2 (ii) 0.3 <P2 / Po <1.2 (iii) 0.2 <Ps2 / Po <1.0 (iv) 0.4 <P _Lapd / Po <1.5 (v) 0.4 <D12 / fo <4.0 (vi) 0.3 <Ds1s2 / fo <3.0 where fo = 1 / Po, where D12 is the surface closest to the object of the first lens unit and the surface closest to the image of the second lens unit , Ds1S2 is the distance between the surface of the first sub-lens unit closest to the object and the surface of the second sub-lens unit closest to the image.

The projection lens of the present invention is desirably designed using the position of the output of the illumination system as a pseudo aperture stop / entrance pupil of the projection lens. (Betensky US Patent No. 5,
313, 330, the relevant parts of which are hereby incorporated by reference). This results in an efficient coupling between the light output of the illumination system and the projection lens.

According to such an embodiment of the present invention,
A projection lens apparatus for forming an image of an object, comprising: (a) an illumination system including a light source and an illumination optical system for forming an image of the light source (output of the illumination system); (b) pixels constituting the object And (c) a projection lens as described above, wherein the projection lens has an entrance pupil at a position substantially corresponding to the position of the output of the illumination system.

In terms of performance, the desirable level of image quality of the projection lens of the present invention is that distortion is less than 1%, more preferably less than 0.5%, and lateral chromatic aberration is one pixel in a wavelength range of 470 nm to 630 nm. Less than 40%, and the axial chromatic aberration is less than one pixel in the wavelength range of 470 nm to 630 nm. These performance levels of color correction are applied on the object or image, and if the criterion is applied on the image, enlarged pixels are used. The performance level of the longitudinal chromatic aberration is gentler than the lateral chromatic aberration. This is because axial chromatic aberration appears as a symmetric halo, but the halo is less noticeable than a halo caused by lateral chromatic aberration.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A projection lens according to the present invention basically comprises a first negative lens unit and a second positive lens unit, and the second lens unit comprises two sub lens units. You.

The projection lens of the present invention has at least one, preferably a plurality of aspherical surfaces for correcting aberrations such as spherical aberration, astigmatism, coma, and distortion.
The aspheric surface is preferably formed on a plastic lens element. It is preferable that the aspherical surface is formed only in the first lens unit so that all the lens elements of the second lens unit can be formed of glass. This facilitates manufacture and assembly of the projection lens.

As mentioned above, distortion correction is particularly important for projection lens systems used with pixelated panels. Desirably, distortion correction in the projection lens of the present invention is better than about 1.0%, and more preferably better than about 0.5%. This distortion correction level must be maintained over the entire focusing range. In fact, it has been found that a projection lens having an aspheric surface only in the first lens unit can provide such a high level of distortion correction.

For primary color correction, the projection lens generally needs to have a negative lens element made of a high dispersion material and at least one positive lens element made of a low dispersion material. The high and low dispersion materials may be glass or plastic. In general,
The high-dispersion material is a material having dispersibility such as flint glass, and the low-dispersion material is a material having dispersibility such as crown glass. More specifically, the high dispersion material has a refractive index in the range of 1.85 to 1.5 and 20 to 5
The low-dispersion material has a V-value in the range of 35 to 75 for the same range of refractive index.

In the case of a plastic lens, the high dispersion material and the low dispersion material are, for example, styrene and acrylic resin, respectively. Of course, other plastics can be used if desired. For example, instead of styrene, a polycarbonate having the same dispersing power as flint glass, a copolymer of polystyrene and an acrylic resin (eg, NAS), or the like can be used. “USPrecision Lens Inc.,” Cincinnati, Ohio
"The Handbook of Plastic Optics" 1983 edition,
See pages 17-29.

For secondary color correction, the projection lens of the present invention comprises at least one lens having an extraordinary partial dispersion disposed in a second lens unit, in particular a second sub-lens unit of the second lens unit. Single lens element (Lapd)
It is necessary to provide. The partial dispersion of the optical glass can be expressed as follows.

[0040] _{P 'x, y = (n} x -n y) / (n F' -n C ') (1) where n _x, n _y is the wavelength x, the refractive index of the glass at y, n
_{F '} and nC _' are the refractive indices of the glass at two reference wavelengths, for example, 480 nm and 644 nm.

In the case of a glass having a normal partial dispersion,
P ′ _{x, y} is almost a linear function of Abbe number υd.

[0042]

(Equation 1)

Equation (2) can be applied to most optical glasses. However, the partial dispersion of a certain optical glass, for example, the FCD1 glass used in the embodiment described later, deviates considerably from a straight line. The partial dispersion of such a glass is given by:

P ′ _{x, y} = a _{x, y} + b _{x, y} υd + ΔP ′ _{x, y} (3) In the present specification, the glass having anomalous partial dispersion is defined by the formula (2) It refers to a glass having a partial dispersion represented by the formula (3). Such glasses are described in the Hoya and Schott optical glass catalog. For example, the Hoya Optical Glass Catalog of Hoya Optics, Fremont, CA 2.
Section 4, `` Relative Partial Dispersion and Abnormal Disp
ersion ", Schott Gla, Dourier, PA
ss Technologies' Schott Optical Glass Catalo
g ", section 2.2," Secondary Apectrum ".

It is desirable that the lens element having anomalous partial dispersion be formed of crown glass and have a positive power. However, if desired, a lens element formed of flint glass and having a negative power may be used. In order to achieve the desired very high color correction, lens elements with anomalous partial dispersion need to have considerable power.

Since the refractive index of glass having anomalous partial dispersion, especially of this type of crown glass, is generally small, a large curvature is necessary to obtain a strong lens. As the curvature increases, the monochromatic aberration also increases. Therefore, the second
The second sub-lens unit of this lens unit needs to include a lens element for compensating for monochromatic aberration caused by a lens element having anomalous partial dispersion. For this reason, the second sub-lens unit of each projection lens according to the embodiment described below includes at least one positive lens element (L _P ) and one negative lens element.
(L _N ).

As will be described later in the embodiments, the first sub-lens unit of the second lens unit can have various shapes depending on the use of the projection lens. That is, the first sub-lens unit corresponds to the first, second, and fourth embodiments.
May have a positive power as in the above, or may have a negative power as in the third embodiment. The first sub lens unit may be composed of a plurality of lens elements (Embodiments 3 and 4),
It may be constituted only by a single lens element (Embodiments 1 and 2).

Focusing of the projection lens of the present invention can be performed in various ways, but is preferably performed by changing at least one interval in the lens and simultaneously moving the entire lens with respect to the pixelated panel. Further, as in Embodiment 4, a zoom function may be provided to the projection lens in addition to the focusing function. A known mechanism can be used to move the lens and its components during focusing and zooming.

FIGS. 1 to 4 show projection lenses according to first to fourth embodiments of the present invention. 1st to 4th
Tables 1 to 4 show specifications, optical characteristics, and the like of the embodiment. The glass used for the lens system is "H
OYA ”or“ SCHOTT. ”In practice, equivalent glass from other manufacturers can be used, and plastic lens elements are made of industrially usable materials.

The aspherical coefficients shown in Tables 1 to 4 are used in the following equations.

[0051]

(Equation 2)

Where z is the sag of the surface at a distance y from the optical axis of the system, c is the curvature of the lens on the optical axis, and k is the cone coefficient. The conic coefficient k is 0 unless otherwise specified in Tables 1 to 4.

The abbreviations in the table are as follows.

EFL Effective focal length FVD Front vertex distance f / F number ENP Entrance pupil viewed from length conjugate BRL Lens barrel length OBJHT Object height MAG Magnification STOP Position and size of aperture stop IMD Image distance OBD Object distance OVL Total length “A” attached to the surface in the table represents an aspheric surface, that is, a surface in which at least one of D, E, F, G, H, and I in the above formula is not 0, and “c” is k in the above formula. Represents a non-zero surface. Surface 5 in Tables 1 and 2 and Surface 11 in Table 3 are optional vignette surfaces. The unit of all dimensions in the table is mm.

The table is created on the assumption that light travels from left to right in the figure. In practice, the screen will be placed on the left, the pixelated panel will be placed on the right, and the light will travel from right to left. In particular, the description of objects and images in the tables is the reverse of the description herein below and the claims. In the figure, the pixelated panel is indicated by PP.

Various elements and lens surfaces in Tables 1 to 4 and the above-mentioned "first lens unit" and "second lens unit"
Lens unit ”,“ first sub lens unit ”,
Correspondence with terms such as "second sub-lens unit" is shown in Table 5. U1 is a first lens unit, U2 is a second lens unit, U2 _S1 is a first sub lens unit of the second lens unit, and U2 _S2 is a second sub lens unit of the second lens unit.

As mentioned above, the projection lenses shown in Tables 1 to 4 are disclosed in Betensky US Pat. 5,313,330
Are designed using the pseudo-aperture stop / entrance pupil method.
According to this method, an illumination system is used to determine the position of the entrance pupil of the projection lens, which is located at a fixed position relative to the pixelated panel at all focal lengths and conjugates of the lens. . The position of the entrance pupil is determined by substantially parallel light (almost telecentric light) from the illumination system passing through the pixelated panel.

In Tables 1 to 4, the surface designated as "aperture stop" is a surface constituting the pseudo-aperture stop in the above-mentioned Betensky US Patent. The position of the pseudo aperture stop corresponds to the position of the output of the illumination system. As is evident from the "variable spacing" portion of each table, the distance from the pseudo-aperture stop to the pixilated panel is substantially constant for all magnifications of the projection lens devices of Tables 1-4. (Refer to the column of “image distance”.) For the magnifications shown, the variable intervals for determining the position of the aperture stop with respect to the rear surface of the projection lens are negative in Tables 1, 2, and 4. This means that the output of the illumination system is located in the space defined by the front and rear lens surfaces of the lens. The same applies to Table 3 if the surface 18 is considered. Although this pseudo aperture stop method is desirable, it does not mean that it must be used for designing the lens of the present invention. The lens of the present invention can also be designed using a conventional aperture stop.

As described above, the projection lens according to the fourth embodiment has both a focusing function and a zoom function.
By having the zoom function, the image can be finely tuned. For example, the image can be adjusted to fill the screen.

Although both focusing and zooming involve a change in magnification, the process in which the change in magnification occurs is fundamentally different. That is, at the time of focusing, the focal length of the lens is substantially constant even if the image conjugate and the object conjugate change. A change in magnification is obtained as a result of the change in both conjugates. On the other hand, during zooming, the image conjugate and the object conjugate are kept constant, the focal length changes, and the change in the focal length leads to a change in magnification.

Positions 1 to 5 in Table 4 show this difference, positions 2, 4, and 5 are associated with lens focusing, and positions 1, 2, and 3 are associated with zooming. The lens of this embodiment includes means for allowing a change in focus due to zooming. Table 4 shows the change in conjugate during zooming to achieve this focus correction.

The focusing range F of the lens shown in Table 4 is 0.08. Here, the focusing range F of the projection lens is defined as F = max | hI / ho | -min | hI / ho |. Where ho is the height of the object, hI is the height of the magnified image, max
| HI / ho | and min | hI / ho | are the maximum and minimum values of magnification (reduction ratio) (image / object) that can be achieved by the projection lens while maintaining a desired level of image quality, respectively. . The lens according to the fourth embodiment can maintain the above-described image quality level over the entire focusing range.

Table 4 shows the zooming range Z of the lens.
Is 0.112. The zoom range Z of the projection lens is Z = 2 · (max | hI | -min | hI |) / (max | hI | + min
| HI |).

However, max | hI | and min | hI | are the maximum image height and the minimum image height when zooming around a certain | hI / ho | ratio within the focusing range, respectively.

As is well known, all zoomable lenses can be "forced" beyond their design zoom range. Of course, the performance of the lens is reduced by the "forced drive". However, the decrease in performance is usually not very sharp and generally does not affect all performance parameters at the same rate. Therefore, here, the zoom range of the lens means that when the range is expanded by 50%, the image quality falls below a desired range at any point within the expanded range, or the lens element moves. Is limited by the physical structure of the lens or the supporting structure of the lens. In the case of the lenses in Table 4, distortion is a problem, and when the zoom range is increased to 0.168, the distortion exceeds 1%.

Table 6 summarizes various characteristics of the lens device of the present invention. As can be seen from this table, in the lens apparatus of the present invention, Po (= 1 / fo), P1, P2, P _S2 , P
_Lapd, desired relationship as described above can be obtained for D _12, D _S1S2.

As described above, the lens of the present invention has all the above-mentioned characteristics desired for a projection lens used with a pixelated panel. The specific embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made.

[0068]

[Table 1]

[0069]

[Table 2]

[0070]

[Table 3]

[0071]

[Table 4]

[0072]

[Table 5]

[0073]

[Table 6]

[0074]

[Table 7]

[0075]

[Table 8]

[0076]

[Table 9]

[0077]

[Table 10]

[Brief description of the drawings]

[Fig. 1]

FIG. 4 is a schematic side view of the projection lens according to the embodiment of the present invention.

FIG. 5 is a schematic view showing an entire projection lens device that can use the projection lens of the present invention.

[Explanation of symbols]

U1 First lens unit U2 Second lens unit U2 _s1 First sub-lens unit of second lens unit U2 _s2 Second sub-lens unit of second lens unit Lapd, Lapd2 Lens element PP Pixelated panel

Claims (20)

[Claims] The power for forming an image of an object is
Po, a projection lens having a focal length of fo, wherein (A) a first lens unit having a negative power P1, and (B) a second lens unit having a positive power P2,
The first lens unit and the second lens unit are provided in this order from the image side to the object side, and the axial distance between the first lens unit and the second lens unit is D12. A lens unit, and (ii) a second sub-lens unit having a positive power Ps2 in this order from the image side to the object side, wherein the second sub-lens unit has a second power from the first sub-lens unit. A projection lens, wherein the axial distance is Ds1s2, and the second sub-lens unit is _composed of a lens element Lapd having an abnormal partial dispersion and a power P _Lapd . 2. The projection lens according to claim 1, wherein the lens element having the abnormal partial dispersion has a positive power. 3. The projection lens according to claim 2, wherein said second sub-lens unit further comprises a negative lens element and a positive lens element. 4. The projection lens according to claim 2, wherein 0.4 <P _Lapd /Po<1.5. 5. The projection lens according to claim 1, wherein the first lens unit has at least one aspheric surface. 6. The projection lens according to claim 1, wherein said first lens unit comprises a single lens element. (7) 0.3 <| P1 | / Po <1.2, 0.3 <P2 / Po <1.2, 0.
2. The projection lens according to claim 1, wherein 2 <Ps2 / Po <1.0. 8. The projection lens according to claim 1, wherein 0.4 <D12 / fo <4.0 and 0.3 <Ds1s2 / fo <3.0. 9. The projection lens according to claim 1, wherein the object is a pixelated panel. 10. The method according to claim 9, wherein lateral chromatic aberration is less than 40% of one pixel in a wavelength range of 470 nm to 630 nm, and axial chromatic aberration is less than one pixel in a wavelength range of 470 nm to 630 nm.
The projection lens as described. 11. A projection lens device for forming an image of an object, comprising: (a) an illumination system including a light source and an illumination optical system for forming an image of the light source as an output; and (b) constituting the object. A projection lens device comprising: a pixelated panel; and the projection lens according to claim 1. 12. The projection lens device according to claim 11, wherein the projection lens has an entrance pupil at a position substantially corresponding to a position of an output of the illumination system. 13. A projection lens for forming an image of an object, comprising: (A) a first lens unit having a negative power; and (B) a second lens unit having a positive power. , From the image side to the object side in this order, there is an axial spacing between the second lens unit and the first lens unit, and the second lens unit comprises: (i) a first sub lens A unit, and (ii) a second sub-lens unit having a positive power, in this order from the image side to the object side, and between the second sub-lens unit and the first sub-lens unit. A projection lens having an axial spacing, wherein the second sub-lens unit comprises a lens element having anomalous partial dispersion. 14. The projection lens according to claim 13, wherein said first lens unit comprises a single lens element. 15. The projection lens according to claim 14, wherein the first lens unit has at least one aspheric surface. 16. The lens element having an abnormal partial dispersion having a positive power.
3. The projection lens according to 3. 17. The projection lens according to claim 16, wherein said second sub-lens unit further comprises a negative lens element and a positive lens element. 18. The object is a pixelated panel, wherein lateral chromatic aberration is less than 40% of one pixel in a wavelength range of 470 nm to 630 nm, and axial chromatic aberration is less than 1 pixel in a wavelength range of 470 nm to 630 nm. The projection lens according to claim 13, wherein 19. A projection lens apparatus for forming an image of an object, comprising: (a) an illumination system including a light source and an illumination optical system for forming an image of the light source as an output; and (b) constituting the object. A projection lens device comprising: a pixelated panel; and the projection lens according to claim 13. 20. The projection lens device according to claim 19, wherein the projection lens has an entrance pupil at a position substantially corresponding to a position of an output of the illumination system.