CN110375851A - A kind of high signal to noise ratio wide spectrum double aperture slit spectrometer - Google Patents

Abstract

The invention discloses a high-signal-to-noise ratio wide-spectrum double-slit spectrometer. The system consists of a double-slit assembly, a collimating free-form surface mirror, a curved prism, an imaging free-form surface mirror, a spectrum-segment folding mirror, and a spectrum-segment detection It consists of a detector and a spectrum two detector. The curved prism has high efficiency in a wide spectral range, and the refractive index difference dispersion beam has a high signal light stray light ratio (signal-to-noise ratio). The curved prism and the free-form mirror are used to realize the separation of the double slits at the object surface. Imaged on detector focal planes of different spectral bands. The system has excellent imaging quality and simple structure, and can effectively solve the contradiction between the signal-to-noise ratio and resolution of different spectral bands of the spectrometer.

Description

A high signal-to-noise ratio wide-band double-slit spectrometer

technical field

The invention relates to the field of imaging spectrometers, in particular to an optical system of a high signal-to-noise ratio wide-spectrum double-slit spectrometer.

Background technique

Spectroscopic technology has always been the core of the spectrometer system, and gratings and prisms are the mainstream spectroscopic methods in recent years. The grating uses few optical components and has good spectral linearity. The disadvantage is that the grating generally uses the first-order spectrum, and the utilization rate of light energy is low. The prism makes the outgoing light of different wavelengths have different angles through the difference of refractive index in different wavelength bands, resulting in dispersion, which has a certain nonlinearity and requires post-correction. The transmittance has a high utilization rate of light energy, the signal light stray light ratio (signal-to-noise ratio) is large, and it is not sensitive to light polarization.

In recent years, with the remarkable progress of ultra-precision optical processing, manufacturing and inspection technology, the high-precision processing, inspection and adjustment of complex curved prisms and complex optical surfaces have become possible. The use of prism dispersion light dispersion plus complex optical surface large design The degree of freedom can effectively correct various imaging aberrations and distortions of the spectrometer system, and can build a high-signal-to-noise ratio wide-spectrum spectrometer system with excellent performance.

There are often two ways to use the traditional broad-spectrum prism spectrometer: one is for single-slit spectroscopic imaging, using a dichroic plate at the detector position close to the focal plane to separate different spectral bands, and then using a dichroic plate at each focal plane to separate the different spectral bands. The detector in the spectrum should receive the signal. This scheme has the problems of limited total energy entering the system and low signal-to-noise ratio in the boundary area of the dichroic film system curve. The second is dual-slit spectroscopic imaging. Two spectrometers are used to realize the spectroscopic imaging of different spectral bands of a single slit, and the reasonable arrangement of the two rear optical path spectrometers is realized by the folding of the folding mirror at the slit. The energy is doubled, and there is no problem of the overlapping area of the color separation sheets, but the volume and weight of the system are relatively large and the complexity is relatively high.

SUMMARY OF THE INVENTION

The invention provides a double-slit spectrometer with high signal-to-noise ratio and wide spectrum. The curved prism is used for light splitting, and the free curved surface acts as a collimating mirror and an imaging mirror respectively. In spectroscopic imaging, at the respective dispersive imaging focal plane positions of the two slits, the detectors of different wavelength bands are used to receive signals respectively to realize the spectral imaging of different spectrum bands.

A high-signal-to-noise ratio wide-spectrum double-slit spectrometer of the present invention comprises a double-slit assembly 1, a collimating free-form surface mirror 2, a curved-surface prism 3, an imaging free-form surface mirror 4, a spectral segment folding mirror 5, and a spectral segment 1 Detector 6 and Spectrum II Detector 7. The light reflected by the ground object is incident on the collimating free-form surface mirror 2 through the double slit assembly 1, and then is reflected by the collimating free-form surface mirror 2 to the front surface of the curved prism 3 for transmission, and is reflected in the back surface of the curved prism 3, and again The transmission passes through the front surface of the curved prism 3 and is reflected and focused on the imaging free-form curved mirror 4 . Among them, the light incident through the slit below the double slit assembly 1 is reflected by the sub-segment refraction mirror 5 to the detector 6 of the first spectrum, and the light incident through the slit above the double slit assembly 1 is directly incident on the second spectrum. The detector 7 detects reception.

The double slit assembly 1 includes two parallel slits separated by a certain distance, and can be set to different slit widths according to different operating bands and different resolution requirements.

The collimating free-form surface mirror 2 and the imaging free-form surface mirror 4 are optical surfaces that do not have rotational symmetry, but are axis-symmetrical about the center line connecting the two slits.

According to the spectrum used, the curved prism material is made of optical glass with high transmittance, and there is no multi-level spectrum, so the system has a wider imaging spectrum and a higher signal-to-noise ratio. The front and rear surfaces of the curved prism are eccentrically set, free The curved collimating mirror and the free-form surface imaging mirror are xy polynomial optical surfaces without rotational symmetry. As shown in formula 1, they are processed by diamond single-point turning and matched with CGH compensator for high-precision surface inspection.

The system mentioned in the present invention, due to the use of double slits, avoids using a dichroic sheet for light splitting, there is no spectral overlap region, and the system has a high signal-to-noise ratio in the entire spectrum. In addition, with the double slit setting, different wavelength bands can use different slit widths, which can more effectively solve the contradiction between the signal-to-noise ratio and the resolution of the spectrometer. The large design freedom of the optical free-form surface is used to correct the off-axis aberration, spectral distortion and spectral line bending of the larger field of view caused by the separation of the double slits on the object side. The system has excellent imaging quality and simple structure.

Description of drawings

1 is a schematic diagram of an embodiment spectrometer;

In the figure, 1 is a double slit assembly, 2 is a collimating free-form surface mirror, 3 is a curved prism, 4 is an imaging free-form surface mirror, 5 is a spectral-segment folding mirror, 6 is a spectral segment-detector focal plane, and 7 is the focal plane of the spectral band two detectors.

2 is a schematic diagram of an embodiment double slit assembly;

Fig. 3 is the image quality of the spectrometer system of the embodiment, the transfer function curve of each field of view at each spectral section;

In the figure, (a) and (b) are the transfer functions at the two ends of the first spectrum at wavelengths of 0.35um and 1.0um, respectively. The cut-off frequency is 33.33lp/mm, and the field of view is the width of the slit under the slit assembly. Field of view; (c) and (d) are the transfer functions at the middle wavelength and long wavelength of the second spectrum at wavelengths 1.2um and 2.5um, respectively. The cut-off frequency is 16.7lp/mm, and the field of view is the upper slit of the slit assembly. field of view.

Detailed ways

Below in conjunction with accompanying drawing and embodiment, the present invention is described in further detail: as shown in Figure 1, a kind of high-signal-to-noise ratio wide-spectrum double-slit spectrometer of the present invention, double-slit assembly is placed on the focal plane of the front telescope (front The telescope is not within the scope of the present invention), the light passing through the double slits is reflected by the collimated free-form surface mirror, firstly transmitted through the front surface of the curved prism, internally reflected on the back surface, and twice transmitted on the front surface, and then passes through the imaging free-form surface mirror. Convergence imaging, in the focal plane of the first spectrum band, the separate receiving and detection of different spectrum bands to different detector focal planes are realized through the sub-spectrum folding mirror. The entire working wide spectral range of the embodiment of the present invention is 0.35-2.5um, the wavelength band 0.35-1.0um corresponds to the first spectrum, the corresponding slit is the lower slit in FIG. 1, the size of the slit is 0.015mm*80mm, and the wavelength band 0.9-2.5um corresponds to the second spectrum, the corresponding slit is the upper slit in Figure 1, and the size of the slit is 0.030mm*80mm. Fig. 2 is a side view of the double slit assembly of the embodiment. The upper and lower slits are separated by 20mm, which can not only satisfy the non-interference arrangement of the detectors in the first and second spectrums, but also balance the ability of the system to balance the off-axis aberration. , and its upper and lower slits correspond to the upper and lower slits in FIG. 1 . The system design indexes of the spectrometer of the embodiment are shown in Table 1, and the design parameters of the spectrometer are shown in Table 2.

Table 1. Design indicators of the embodiment system

Table 2. Spectrometer design parameters

Claims (3)

1. a kind of high signal to noise ratio wide spectrum double aperture slit spectrometer, including double aperture slit component (1), collimation free-form curved mirror (2), curved surface Prism (3), imaging free-form curved mirror (4), open score section are turned back mirror (5), one detector of spectral coverage (6) and two detector of spectral coverage (7), It is characterized in that:

The light of ground object target reflection is incident on collimation free-form curved mirror (2) by double aperture slit component (1), then collimated freedom Curved mirror (2) reflexes to the front surface transmission of curved surface prism (3), and in the rear surface internal reflection of curved surface prism (3), transmission is passed through again Focusing is reflected in imaging free-form curved mirror (4) after crossing the front surface of curved surface prism (3).Wherein, through below double aperture slit component (1) The light of slit incidence reflexes to one detector of spectral coverage (6) and receives through open score section mirror (5) of turning back, through narrow above double aperture slit component (1) It sews up the light penetrated and is directly transmitted to two detector of spectral coverage (7) detection reception.

2. a kind of high signal to noise ratio wide spectrum double aperture slit spectrometer according to claim 1, it is characterised in that: described is double narrow Stitching component (1) includes two slits parallel and that phase is with a certain distance from, is wanted using wave band with different resolution ratio according to different It asks and different slit widths can be set into.

3. a kind of high signal to noise ratio wide spectrum double aperture slit spectrometer according to claim 1, it is characterised in that: the collimation Free-form curved mirror (2) and imaging free-form curved mirror (4) are the line of centres axial symmetry about two slits not have rotational symmetry Optical surface.