Chlorophyll Fluorescence Imager

I. Product Overview

The Chlorophyll Fluorescence Imaging System is a professional instrument for plant photosynthesis research. Utilizing a high-sensitivity CMOS camera and LED light source control, it enables rapid, non-destructive detection and imaging analysis of chlorophyll fluorescence in plant leaves. The system integrates two core functions: OJIP rapid fluorescence kinetics measurement and PAM modulated fluorescence measurement, enabling comprehensive evaluation of plant photosynthetic system activity, light use efficiency, and responses to environmental stress.

Featuring a modular design with highly integrated hardware and software, the system offers a user-friendly graphical interface supporting bilingual Chinese-English switching. It is widely applicable for research and teaching in plant physiology, ecology, agricultural science, environmental science, and related fields.

II. Technical Specifications

Camera:

Resolution: 1608(H) × 1104(V)

Pixel Size: 9µm × 9µm

★Frame Rate: 100 fps

Pixel Depth: 12 bit

Interface Type: USB 3.0

Lens and Optical Parameters

★Focal Length: 12mm

★Maximum Aperture: F/2.8 (dynamically adjustable)

Horizontal Field of View (HFOV): Approx. 62.11°

Vertical Field of View (VFOV): Approx. 44.83°

Maximum Imaging Range: 50cm × 35cm at standard working distance

Light Source Parameters

Blue Light Wavelength: 450 nm excitation light source for fluorescence excitation

Red Light Wavelength: 630 nm photochemical light for PAM measurement

Far-Infrared Light: 730 nm for specific measurement requirements

LED Brightness Range: 1% - 100%, peak intensity up to 1440 µmol/(m²·s)

Measurement Range

1. OJIP Measurement

Measurement Duration: 0.1 - 1.0 seconds, adjustable, recommended 1 second

LED Brightness: 1% - 100%, corresponding to 90-1440 µmol/(m²·s), 5% increments

2. PAM Measurement

Dark adaptation time: 0 - 3600 seconds, can be set to 0 to skip

Light cycle count: 1 - 100 cycles, number of cycles during light adaptation phase

Monitoring duration: 10 - 120 seconds/cycle, monitoring time per cycle

Recovery time: 60 - 600 seconds, dark recovery monitoring duration

Photochemical light intensity: 1000 - 30000, red light 630nm LED brightness value

Saturation pulse (Fm): 15% - 100%, dark adaptation saturation pulse (blue light 450nm)

Saturation pulse (Fm'): 15% - 100%, light adaptation saturation pulse (blue light 450nm)

Sampling Interval: 0.1 - 10.0 seconds, data acquisition interval

Measurement Accuracy

1. Fluorescence Intensity Measurement

Dynamic Range: 12-bit (0-4095)

Signal-to-Noise Ratio: >100:1

Repeatability: CV < 3%

Linearity: R² > 0.999

Sensitivity: Capable of detecting faint fluorescence signals

2. Parameter Calculation Accuracy

Fv/Fm: ±0.005

ΦPSII: ±0.01

qP/qN: ±0.02

NPQ: ±0.1

PIABS: ±0.05

3. Time Resolution

OJIP Mode: Minimum acquisition interval 10ms

PAM Mode: Minimum sampling interval 100ms

Exposure Time: Adjustable 100ms - 1000ms

Response Time: <1ms (LED light source)

4. Spatial Resolution

★ Imaging Resolution: 1608 × 1104 pixels

Pixel Size: 9µm × 9µm (sensor)

Actual Spatial Resolution: Approx. 0.3mm/pixel (at 50cm × 35cm field of view)

Field of View: Horizontal 62.11°, Vertical 44.83°

★ Imaging Area: Maximum 50cm × 35cm

III. Function Overview

1. OJIP Rapid Fluorescence Kinetic Analysis

The OJIP measurement mode enables rapid assessment of photosystem II (PSII) activity and light use efficiency in plants. By applying intense light excitation, it records the complete rise kinetics from initial fluorescence (Fo) to maximum fluorescence (Fm) within 1 second.

Measurement Principle:

Under dark-adapted conditions, intense light exposure causes gradual reduction of PSII reaction center QA from its oxidized state, resulting in rapid fluorescence intensity increase. This process reflects electron transport chain efficiency and the quantity/activity of PSII reaction centers.

Information Obtained:

O point (Fo): Initial fluorescence when all PSII reaction centers are open

J point: Approx. 2ms, reflecting electron transfer from QA to QB (calculated)

Point I: Approx. 30 ms, reflecting the reduction state of the PQ pool

Point P (Fm): Maximum fluorescence when all reaction centers are closed

Key Calculated Parameters:

Fundamental Parameters: Fv = Fm - Fo, Fv/Fm (maximum photochemical efficiency)

Specific activity: Mo (initial slope), Area (QA reduction area)

Quantum yield: ΦPo (capture efficiency), ΦEo (electron transfer efficiency), ΦDo (thermal dissipation)

Energy flux: ABS/RC, TRo/RC, ETo/RC, DIo/RC

Performance index: PIABS (comprehensive performance index)

Application Scenarios:

Rapid screening of plant materials

Assessment of environmental stress levels

Monitoring changes in growth status

Comparing effects of different treatments

2. PAM Modulated Fluorescence Measurement

PAM measurement mode employs modulated fluorescence technology to monitor plant photosynthetic activity under varying light conditions. It distinguishes between photochemical and non-photochemical quenching, providing insights into plant photoprotection mechanisms.

Measurement Procedure:

Dark Adaptation Phase: Plants fully relax in darkness, restoring all reaction centers to open states

Fo and Fm Measurement: Apply measurement light and saturation pulses to determine dark-adapted fluorescence parameters

Light-adapted phase: Photochemical light is provided to simulate natural light conditions.

Cyclic monitoring: Saturation pulses are periodically applied to measure Fs and Fm'.

Dark relaxation phase: Far-red light is immediately applied after photochemical light is turned off to determine the light-adapted minimum fluorescence (Fo').

Dark recovery detection: Photochemical light and far-red light are turned off to monitor the fluorescence recovery process.

Key Parameters:

Fv/Fm: Maximum photochemical efficiency of PSII (0.78–0.84 in healthy plants)

ΦPSII: Actual photochemical efficiency of PSII (light energy utilization under illumination)

qP: Photochemical quenching coefficient (proportion of open reaction centers)

qN: Non-photochemical quenching coefficient (photoprotection capacity)

NPQ: Non-photochemical quenching (degree of heat dissipation)

ETR: Electron Transfer Rate (indicator of photosynthetic rate)

Application Advantages:

Non-destructive measurement, repeatable monitoring

Distinguishes between photochemical and non-photochemical processes

Real-time monitoring of photosynthetic dynamics

Evaluates efficiency of photoprotection mechanisms

★3. Data Analysis and Visualization

Basic Fluorescence Parameters (OJIP): F0, Fm, Fv, Fv/Fm

JIP-test Parameters: ΦPo, ΦDo, ΦEo, ψEo, δRo, ABS/RC, TRo/RC, ETo/RC, DIo/RC, REo/RC, PI_abs, M0, Vj, Vi, Area, Sm, N

Basic Fluorescence Parameters (PAM): F0, Fs, F0', Fv/Fm

PAM-derived parameters: ΦPSII, qP, qL, qN, NPQ, NPQ_SV, Rfd, Kf, Fs/Fm, Fs/Fm', PSII_closed, PSII_closed_Lake, actual_efficiency, excitation_pressure, Fm_decline_percent, efficiency_decline_percent, Vitality_Index, qP', qL_full, PSII_closed_Lake_full, ΦNPH, ΦNO, Y_NPH, Y_NO, Rfd'

Visualization Display

Fluorescence Images: Displays 2D fluorescence color images for each parameter of basic fluorescence parameters (OJIP, PAM), JIP-test parameters, and PAM-derived parameters.

Kinetic Curves: OJIP curve, relative variable fluorescence curve

Time Series Curves: PAM fluorescence intensity change curve

Parameter Table: Clear display of parameter names, values, and units

4. Image Processing and Analysis

★Automatic Region Segmentation: The system uses an intelligent threshold segmentation algorithm to automatically identify plant leaf areas in the image, excluding background and non-target objects. Users can enable or disable this function as needed.

Manual Selection: For complex backgrounds or situations requiring precise analysis of specific areas, users can directly select rectangular, circular, and irregular areas on the Fm image and view the selection information in real time.

★Image Region Mean: Supports selecting points, rectangles, circles, and irregular areas on any image and viewing the regional mean in real time.

Image Enhancement Processing:

Gaussian filtering for noise reduction

Adaptive contrast enhancement

Scientific color scheme (Jet pseudocolor)

Color bar displays numerical range

5. Data Management

★Automatic Parameter Saving: All measurement parameters (LED brightness, measurement time, number of cycles, etc.) are automatically saved to the configuration file after modification, and automatically loaded upon next startup, eliminating the need for repeated settings.

Result Export Function:

Export Images: Export all analyzed images in PNG format, maintaining original resolution.

Export Parameters: Export the parameter table as a CSV or Excel file for statistical analysis.

Export All: One-click export of all images and parameter tables to a specified directory.

File Naming Convention: Exported files are automatically named according to the format "Mode + Sequence Number + Image Name," clearly identifying the content source.

6. System Settings

Language Switching: Click the language switching button in the upper right corner of the interface to instantly switch between Chinese and English. Language settings are automatically saved and retained after restarting.

Parameter Configuration: All measurement parameters support user-defined settings to adapt to different experimental needs. The system provides parameter tooltips to help users understand the meaning and recommended range of each parameter.

Device Management: The system automatically detects and connects to the camera and LED controller upon startup. The status bar displays the device connection status in real time, facilitating timely detection and resolution of hardware problems. IV. Application Scope

1. Plant Physiology Research

Photosynthesis mechanism research

Photosystem activity assessment

Light energy utilization efficiency analysis

Non-photochemical quenching research

Electron transport chain function evaluation

2. Environmental Stress Research

Drought stress response

Temperature stress effects

Light stress adaptability

Heavy metal toxicity assessment

Early diagnosis of pests and diseases

3. Agricultural Applications

Crop variety screening

Cultivation condition optimization

Fertilizer effect evaluation

Pesticide damage detection

Growth status monitoring

4. Ecological Research

Plant photoadaptation research

Community photosynthetic characteristics

Ecosystem function assessment

Climate change response

Biodiversity assessment

Case Studies

1: Assessing the impact of different drought levels on plant photosynthetic performance

Method: Rapid measurement of Fv/Fm and PIABS using the OJIP protocol

Results: Mild drought led to a 5-10% decrease in Fv/Fm, with the proportion increasing with the severity of drought; severe drought resulted in a decrease of over 30%.

2: Screening for heat-tolerant crop varieties

Method: PAM protocol measurement of ΦPSII and NPQ after high-temperature treatment

Results: Heat-tolerant varieties maintained higher ΦPSII (>0.5) and moderate NPQ (2-3) under high temperatures.

3: Comparing the effects of different fertilization schemes on photosynthetic efficiency

Method: OJIP and PAM combined for comprehensive assessment of photosynthetic performance

Results: Better fertilization schemes resulted in increased Fv/Fm and PIABS.

4: Detecting disease stress before symptoms appear

Method: Continuous monitoring of Fv/Fm and OJIP curve changes

Results: A significant decrease in Fv/Fm could be detected 1-2 days before symptoms appeared.